HK1035605B

HK1035605B - Flat non-aqueous electrolyte secondary cell

Info

Publication number: HK1035605B
Application number: HK01106014.8A
Authority: HK
Inventors: 铃木正美; 早见宗人; 宇田川和男; 饭塚一雄; 石原直美; 平原聪; 酒井广隆; 依田清人; 志子田将贵
Original assignee: Maxell Holdings, Ltd.
Priority date: 1999-08-27
Filing date: 2001-08-27
Publication date: 2005-09-16

Description

Flat nonaqueous electrolyte secondary battery

Technical Field

The present invention relates to a flat nonaqueous electrolyte secondary battery, and more particularly to a flat nonaqueous electrolyte secondary battery having improved heavy load discharge characteristics.

Background

In recent years, flat nonaqueous electrolyte secondary batteries such as coin-shaped and button-shaped nonaqueous electrolyte secondary batteries using MnO as a positive electrode material have been commercialized₂Or V₂O₅Metal oxides such as graphite fluoride, or organic compounds such as polyaniline and polyacene (ポリアセン) structures; the negative electrode is made of metal lithium, an organic compound such as a lithium alloy or polyacene structure, a carbonaceous material capable of absorbing and releasing lithium, or an oxide such as lithium titanate and lithium-containing silicon oxide; in addition, the electrolyte adopts non-aqueous solvent such as propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, gamma butyrolactone and the like, and LiCIO is dissolved in the non-aqueous solvent₄、LiPF₆、LiBF₄、LiCF₃SO₃、LiN(CF₃SO₂)₂、LiN(C₂F₅SO₂)₂Iso-support salt to formThe non-electrolyte of (2). The battery is suitable for a standby power supply of a light-load discharge SRAM or RTC with a discharge current of several muA to several tens muA and a main power supply of a watch without replacing the battery.

These flat nonaqueous electrolyte secondary batteries, such as coin-shaped and button-shaped batteries, generally have the structure shown in fig. 4. That is, the sealing structure is: a metal negative electrode case 5 serving also as a negative electrode terminal, and a metal positive electrode case 1 serving also as a positive electrode terminal. The insulating gasket 6 is fitted together with the interposition of an insulating gasket, and the positive electrode case 1 is caulked by a caulking process. The internal structure is as follows: a disk-shaped positive electrode 12 and a negative electrode 14 each having a diameter smaller by one turn than the opening diameter of the insulating gasket 6 are arranged face to face on both sides of a single-layer or multi-layer separator 13 impregnated with a nonaqueous electrolyte.

The flat nonaqueous electrolyte secondary battery such as coin-shaped and button-shaped batteries has the advantages that: simple manufacture, convenient mass production, long-term reliability and good stability. Further, these batteries are most characterized by being miniaturized because of their simple manufacture.

On the other hand, the miniaturization of application devices is progressing rapidly, particularly in small information terminals such as mobile phones and PDAs, and the miniaturization of secondary batteries as main power sources is also required. In the past, cylindrical and rectangular alkaline secondary batteries such as a cylindrical or rectangular lithium ion secondary battery in which a lithium-containing oxide such as lithium cobaltate is used as a positive electrode active material and a carbon material is used as a negative electrode, and a nickel hydrogen secondary battery in which a basic nickel hydroxide is used as a positive electrode active material and a hydrogen absorbing alloy is used as a negative electrode active material have been used as these power sources. These batteries are manufactured by coating or filling an active material layer on a current collector made of a metal foil or a metal mesh to form an electrode, welding a tab terminal to the central portion (the center portion) of the electrode, winding or laminating the electrode to form an electrode group, and subjecting the tab terminal drawn out from the central portion of the electrode group to a complicated bending process to weld the tab terminal to a mounting member, a seal pin, a battery case, or the like. However, since these batteries are manufactured in accordance with complicated manufacturing processes, they are inferior in manufacturability and it is difficult to miniaturize the components. In addition, in order to prevent the tab terminal from short-circuiting, it is necessary to provide a space in the battery or to install many parts such as safety parts into the battery, and therefore, the miniaturization of the battery has been almost at its highest limit at present.

Therefore, the present inventors have attempted to improve the output of the flat nonaqueous electrolyte secondary battery described above, instead of miniaturizing cylindrical and rectangular lithium ion secondary batteries and nickel hydrogen secondary batteries when miniaturizing the battery. That is, the present inventors used a large-capacity high-potential lithium cobaltate for the positive electrode active material; the negative electrode active material is made of graphitized carbonaceous material having high capacity and good voltage stability, and the positive electrode and the negative electrode are formed into a pressed sheet smaller than the sealing washer by one turn according to the conventional method and structure for manufacturing flat nonaqueous electrolyte secondary batteries.

However, although the characteristics of this battery are superior to those of conventional flat nonaqueous electrolyte secondary batteries, the characteristics are not good enough when discharging at a large current required for the main power supply of a small portable device, and the battery does not achieve a required level of characteristics as the main power supply of the small portable device. Therefore, it is necessary to develop a technique for improving the heavy load discharge characteristics of a small-sized flat nonaqueous electrolyte secondary battery to an unprecedented level.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a flat nonaqueous electrolyte secondary battery having particularly excellent heavy-load discharge characteristics.

In order to achieve the purpose, the invention adopts the following technical scheme: a flat nonaqueous electrolyte secondary battery having a structure in which a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted to each other through an insulating gasket, and the positive electrode case or the negative electrode case is caulked by caulking, and has a nonaqueous electrolyte and a power generating element including at least a positive electrode, a separator, and a negative electrode inside, characterized in that: the electrode unit in which the positive electrode and the negative electrode are opposed to each other via the separator has a plurality of electrode groups stacked together, and the total of the areas of the electrode groups opposed to the positive electrode and the negative electrode is larger than the opening area of the insulating gasket.

The flat nonaqueous electrolyte secondary battery is characterized in that: the electrode units are laminated at least 3 times to form an electrode group.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and the active material layer applied to the positive and negative electrode current collectors has a thickness of 0.03mm to 0.40mm on one surface.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet with a negative electrode acting material layer formed on one side or two sides of a negative electrode current collector, one end of each of the positive electrode sheet and the negative electrode sheet exposes each current collector to form a current-carrying part, and the positive electrode current-carrying parts are exposed from the same side surface of the positive electrode current-carrying parts and are electrically connected with the positive electrode shell; the negative electrode conducting parts are exposed from the other side surface of the negative electrode conducting parts through the spacer and electrically connected with the negative electrode casing.

The flat nonaqueous electrolyte secondary battery is characterized in that: a non-aqueous electrolyte is used in which₀₀₂A graphite structure having an interplanar spacing of 0.338nm or less, as a negative electrode, and ethylene carbonate and gamma-butyrolactone as main solvents, in which lithium fluoroborate as a supporting salt is dissolved.

The flat nonaqueous electrolyte secondary battery is characterized in that: the volume ratio of the ethylene carbonate to the gamma-butyrolactone is 0.3-1.0.

The flat nonaqueous electrolyte secondary battery is characterized in that: the concentration of the supporting salt in the nonaqueous electrolyte is 1.3 to 1.8 mol/l.

The flat nonaqueous electrolyte secondary battery is characterized in that: a stainless steel is used which is also used as a constituent material of a positive electrode case of a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are further added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: a stainless steel which is used as a constituent material of a positive electrode case of a positive electrode terminal or a metal component directly connected to a positive electrode active material is obtained by adding 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper to a ferrite stainless steel containing 20.50 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: a metal mesh is disposed between the positive electrode case and/or the negative electrode case and the electrode group.

The flat nonaqueous electrolyte secondary battery is characterized in that: a non-metallic heat insulating material is provided between the positive electrode case and/or the negative electrode case and the separator.

The flat nonaqueous electrolyte secondary battery is characterized in that: the sealing is carried out by utilizing the riveting processing method, namely, the insulating washer is compressed in the radial direction and the height direction by the anode shell, a notch is arranged on the side part of the anode shell, the width of the notch is 0.1 pi-0.9 pi rad relative to the center angle of the circumference of the anode shell, and the depth of the notch is 5-30% of the height of the anode shell.

The flat nonaqueous electrolyte secondary battery is characterized in that: the sealing is performed by a caulking process in which the insulating gasket is compressed in the radial direction and the height direction by the positive electrode case, and 1 or 2 grooves are formed in the longitudinal axis direction of the sealing portion of the positive electrode case to form a thin plate portion.

The flat nonaqueous electrolyte secondary battery is characterized in that: the thickness of the thin plate part formed by the groove processing is 0.07mm to 0.15 mm.

The flat nonaqueous electrolyte secondary battery is characterized in that: at least one breaking groove with concave section is arranged in the negative electrode shell.

The flat nonaqueous electrolyte secondary battery is characterized in that: a crushing groove having a concave cross section is formed on the outer surface of the negative electrode case.

The flat nonaqueous electrolyte secondary battery is characterized in that: the inside of the positive electrode case and/or the negative electrode case is provided with convexes and concaves or protrusions.

A flat nonaqueous electrolyte secondary battery having a structure in which a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted to each other through an insulating gasket, and the positive electrode case or the negative electrode case is caulked by caulking, and has a nonaqueous electrolyte and a power generating element including at least a positive electrode, a separator, and a negative electrode inside, characterized in that: the strip-shaped electrode units, in which the positive electrode and the negative electrode are arranged to face each other with the separator interposed therebetween, are wound to form an electrode group, and the total of the areas of the electrode group facing the positive electrode and the negative electrode is larger than the opening area of the insulating gasket.

The flat nonaqueous electrolyte secondary battery is characterized in that: an electrode group formed by winding the belt-shaped electrode unit is pressurized so that the positive and negative electrode facing surfaces are parallel to the flat surface of the flat battery, and no gap is present in the winding core portion.

The flat nonaqueous electrolyte secondary battery is characterized in that: the band-shaped positive electrode and negative electrode are wound from a position separated from each other via the separator, and the positive electrode and negative electrode are folded and wound so that the opposite surfaces of the positive electrode and the negative electrode are parallel to the flat surface of the flat battery, thereby forming a battery pack.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and the thickness of the active material film layer coated on the positive and negative electrode current collectors is 0.03mm to 0.40mm on one surface.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and each active material film layer is formed only on one surface of each end portion of the negative electrode sheet.

The flat nonaqueous electrolyte secondary battery is characterized in that: using a non-aqueous electrolyte of d₀₀₂The surface spacing of the carbon material is less than 0.338nm, and the carbon material with the developed graphite structure is used as a negative electrode; ethylene carbonate and gamma-butyrolactone are used as main solvents, and lithium fluoroborate is dissolved in the main solvents to be used as a supporting salt.

The flat nonaqueous electrolyte secondary battery is characterized in that:

a stainless steel is used as a constituent material of a positive electrode case serving as a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that:

a stainless steel is used as a constituent material of a positive electrode case serving as a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper are added to a ferrite stainless steel containing 20.00 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: and sealing by using a riveting processing method, namely compressing the insulating washer in the radial direction and the height direction by the anode shell, arranging a notch on the side part of the anode shell, wherein the width of the notch is 0.1-0.9 pi rad relative to the center angle of the periphery of the anode shell, and the depth of the notch is 5-30% of the height of the anode shell.

The flat nonaqueous electrolyte secondary battery is characterized in that: the sealing is performed by caulking, that is, the insulating gasket is compressed in the radial direction and the height direction by the positive electrode case, and 1 or 2 grooves are processed in the longitudinal axis direction of the sealing portion of the positive electrode case to form a thin plate portion.

A flat nonaqueous electrolyte secondary battery having a structure in which a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted to each other through an insulating gasket, and the battery has a sealing structure in which the positive electrode case or the negative electrode case is caulked by caulking and has at least a power generating element including a positive electrode, a separator, and a negative electrode and a nonaqueous electrolyte in its interior, characterized in that: the sheet-like positive electrode is wrapped with a separator except for a portion in contact with the inner surface of the positive electrode case, the sheet-like negative electrode is arranged so as to be orthogonal to the sheet-like positive electrode wrapped with the separator, and the positive electrode sheet and the negative electrode sheet are alternately folded to form an electrode group, and the total of the areas of the electrode group facing the positive electrode and the negative electrode is larger than the opening area of the insulating gasket.

The flat nonaqueous electrolyte secondary battery is characterized in that: the sheet-like positive and negative electrodes are arranged with a separator interposed therebetween so that the positive and negative electrodes intersect each other, and the lower electrode is folded onto the upper electrode via the separator, and the other electrode is folded and superposed on the upper electrode, and thereafter, the process is repeated to form an electrode group.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet with a negative electrode active material layer formed on one side or two sides of a negative electrode current collector, one end of each of the positive electrode sheet and the negative electrode sheet exposes each current collector to form a current-carrying part, and the positive electrode current-carrying parts are exposed from the same side surface of the positive electrode current-carrying parts and are electrically connected with the positive electrode shell; the negative electrode conducting parts are exposed from the other side surface of the negative electrode conducting parts through the spacer and electrically connected with the negative electrode casing.

The flat nonaqueous electrolyte secondary battery is characterized in that: a non-aqueous electrolyte is used in which₀₀₂A graphite structure having an interplanar spacing of 0.338nm or less, as a negative electrode, and ethylene carbonate and gamma butyrolactone as main solvents, in which lithium fluoroborate as a supporting salt is dissolved.

The flat nonaqueous electrolyte secondary battery is characterized in that: a stainless steel is used which is also used as a positive electrode case of a positive electrode terminal or a constituent material of a metal component directly contacting a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are further added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: a stainless steel which is used as a constituent material of a positive electrode case of a positive electrode terminal or a metal component directly connected to a positive electrode active material is obtained by adding 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper to a ferrite stainless steel containing 20.00 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: a non-metallic heat insulating material is provided between the positive electrode case and/or the negative electrode case and the electrode group.

A flat nonaqueous electrolyte secondary battery having a metal battery case serving also as an electrode terminal, a sealing plate for sealing the battery case, and another electrode terminal disposed on an opening portion of a part of the sealing plate via an insulator, the battery case having at least a power generating element including a positive electrode, a separator, and a negative electrode, and a nonaqueous electrolyte, characterized in that: the sealing plate is provided with an electrode group formed of electrode units, wherein the positive electrode and the negative electrode are arranged in an opposite manner through a spacer, and the sum of the opposite areas of the positive electrode and the negative electrode of the electrode group is larger than the opening area of the sealing plate.

The flat nonaqueous electrolyte secondary battery is characterized in that: the electrode units are overlapped in multiple layers to form an electrode group, wherein the positive electrode is electrically connected with the positive electrode, and the negative electrode is electrically connected with the negative electrode.

The flat nonaqueous electrolyte secondary battery is characterized in that: a battery pack in which strip-shaped positive and negative electrodes are wound with separators interposed therebetween is mounted in a battery.

The flat nonaqueous electrolyte secondary battery is characterized in that: a collector plate electrically integrated with the other terminal is disposed, and the collector plate is electrically connected to the positive electrode or the negative electrode.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and the thickness of the active material film layer applied to the positive and negative electrode current collectors is 0.03mm to 0.40mm on one surface.

The flat nonaqueous electrolyte secondary battery is characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet with a negative electrode active material layer formed on one side or two sides of a negative electrode current collector, one end of each of the positive electrode sheet and the negative electrode sheet exposes each current collector to form a current-carrying part, and the positive electrode current-carrying parts are exposed from the same side surface of the positive electrode current-carrying parts and are electrically connected with the positive electrode shell; the negative electrode current-carrying parts are exposed from the other side surface of the negative electrode current-carrying parts through the spacer and are electrically connected with the sealing plate.

The flat nonaqueous electrolyte secondary battery is characterized in that: a non-aqueous electrolyte is used in which₀₀₂A graphite structure having an interplanar spacing of 0.338nm or less, as a negative electrode, and a lithium fluoroborate as a supporting salt dissolved therein, using ethylene carbonate and γ -butyrolactone as main solvents.

The flat nonaqueous electrolyte secondary battery is characterized in that: a stainless steel is used which is a constituent material of a battery case serving as a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are further added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: a stainless steel is used which is also used as a constituent material of a battery case of a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper are further added to a ferrite stainless steel containing 20.00 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

The flat nonaqueous electrolyte secondary battery is characterized in that: a metal mesh is provided between the battery case and/or the sealing plate and the electrode group.

The flat nonaqueous electrolyte secondary battery is characterized in that: a non-metallic heat insulating material is provided between the battery case and/or the sealing plate and the separator.

The flat nonaqueous electrolyte secondary battery is characterized in that: at least 1 breaking groove with concave section is arranged on the sealing plate.

The flat nonaqueous electrolyte secondary battery is characterized in that: a crushing groove with a concave section is formed on the outer surface of the sealing plate.

The flat nonaqueous electrolyte secondary battery is characterized in that: the battery case and/or the sealing plate are provided with projections and depressions on the inner side thereof.

The present inventors have conducted repeated studies on the improvement of the heavy load discharge characteristic of the flat nonaqueous electrolyte secondary battery, and as a result, have found that: the present invention has been accomplished by the realization that the heavy load discharge characteristics can be greatly improved by significantly increasing the electrode area as compared with the conventional flat nonaqueous electrolyte secondary battery.

That is, the present invention is a flat nonaqueous electrolyte secondary battery having a sealing structure comprising: a battery comprising a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal, which are fitted together with an insulating gasket, and the positive electrode case and the negative electrode case are riveted together by caulking, and a power generating element and a nonaqueous electrolyte, which include at least a positive electrode, a separator, and a negative electrode, are provided inside the battery, characterized in that: the positive electrode and the negative electrode are arranged face to face by a separator, a plurality of electrode units are laminated to form an electrode group, or the positive electrode and the negative electrode are arranged face to face by a separator, a strip-shaped electrode unit is wound to form an electrode group, or the positive electrode and the negative electrode are surrounded by a separator except for a part contacting with the inner surface of the positive electrode shell, the negative electrode is arranged to be vertical to the positive electrode surrounded by the separator, the positive electrode sheets and the negative electrode sheets are alternately folded to form an electrode group, and the sum of the opposite areas of the positive electrode and the negative electrode of the electrode group is larger than the opening area of the insulating gasket.

The present invention is a flat nonaqueous electrolyte secondary battery including a metal battery case serving also as an electrode terminal, a sealing plate sealing the battery case, and another terminal disposed through an insulator at an opening provided in a part of the sealing plate, wherein the battery case includes at least a power generating element including a positive plate, a separator, and a negative electrode, and a nonaqueous electrolyte. A battery pack is formed of an electrode unit in which a positive electrode and a negative electrode are arranged to face each other with a separator interposed therebetween, and the sum of the areas of the electrode group in which the positive electrode and the negative electrode face each other is larger than the opening area of the sealing plate.

As described above, in the present invention, the total of the areas of the electrode group facing the positive and negative electrodes is larger than the opening area of the insulating gasket: (1) a plurality of the electrode units are stacked to form an electrode group having a sum of positive and negative electrode facing areas larger than an opening area of the insulating gasket, or (2) the electrode units are in a sheet shape, the sheet-shaped electrode units are wound to form an electrode group having a sum of positive and negative electrode facing areas larger than an opening area of the insulating gasket, or (3) the sheet-shaped positive electrode is surrounded by a separator except for a portion contacting an inner surface of the positive electrode case, the sheet-shaped negative electrode is arranged perpendicular to the sheet-shaped positive electrode surrounded by the separator, and the positive and negative electrode sheets are alternately folded to form an electrode group having a sum of positive and negative electrode facing areas larger than an opening area of the insulating gasket.

As described above, in the present invention, the total area of the facing surfaces (facing) of the positive and negative electrodes in the electrode group is made larger than the opening area of the insulating gasket or the sealing plate, whereby the heavy load discharge characteristics of the flat nonaqueous electrolyte secondary battery can be remarkably improved.

It is surmised that, in order to improve the heavy-load discharge characteristics, it is effective to increase the electrode area. However, in the conventional flat nonaqueous electrolyte secondary battery, since the positive electrode and the negative electrode each in the form of a sheet are accommodated in the battery so as to be inscribed in the insulating gasket, the facing area of the positive electrode and the negative electrode facing each other through the separator is not smaller than the opening area of the insulating gasket by one turn at any time, and it is logically impossible to incorporate an electrode having a facing area exceeding the opening area of the insulating gasket into the battery even if the electrode area is slightly enlarged by reducing the thickness of the gasket.

Therefore, the present inventors have solved the above-mentioned problems by laminating (laminating), winding or folding an electrode unit composed of a positive electrode, a negative electrode and a separator, and then putting it into a case of a very small flat battery such as a coin-shaped battery and a button-shaped battery so that the total of the areas of the electrode group facing the positive and negative electrodes is larger than the opening area of an insulating gasket, in order to change the conventional ideas.

In addition, in the conventional cylindrical or rectangular secondary battery, an electrode having several tens of layers may be incorporated. As described above, this type of battery has a complicated structure, and its electrode structure is difficult to apply to small flat nonaqueous electrolyte secondary batteries such as coin-shaped and button-shaped batteries as it is, and even if it can be applied, the advantages of small volume and good manufacturability of the flat nonaqueous electrolyte secondary battery cannot be maintained. Therefore, it has not been done in the past to incorporate an electrode having a positive electrode-negative electrode facing area larger than the opening area of the insulating gasket into a small flat nonaqueous electrolyte secondary battery such as a coin-shaped or button-shaped.

In a small flat nonaqueous electrolyte secondary battery such as a coin-shaped or button-shaped battery, the electrode group is formed in the form of (1), (2) or (3) as described above, so that the electrode area can be increased and the number of parts can be reduced as much as possible, and the electrode group and the nonaqueous electrolyte required for discharge can be accommodated in the space in the small battery. Further, by using these methods for incorporation, the electrode can be easily produced, and the method is excellent in manufacturability and low in production cost, and therefore, is advantageous for mass production.

In the present invention, when the electrode units are laminated to form the electrode group, it is preferable that at least 3 of the faces of the electrode units which face the positive and negative electrodes (faces which face the positive and negative electrodes) are provided. As the electrodes, a positive electrode plate and a negative electrode plate each having a current carrying portion provided at a part (end) of the electrode are arranged to face each other with a separator interposed therebetween, and the current carrying portions of the positive electrode plate are arranged to be exposed from one direction of the separator; exposing the current carrying part of the negative plate from the side face of the separator on the opposite side, and laminating to expose the current carrying part on the same side between the positive electrodes; the conducting portions are exposed on the same side between the negative electrodes, and the respective conducting portions are electrically connected. Since the conducting portions of the positive and negative electrodes are arranged in a state of opposing electrodes (electrodes are positioned in opposite directions), an internal short circuit caused by contact between the conducting portions of the positive and negative electrodes can be prevented even in a small flat-shaped nonaqueous electrolyte secondary battery such as a coin-shaped battery or a button-shaped battery.

The following describes a method of connecting the electrode group and the metal case.

As described above, in the case of a relatively large lithium ion secondary battery, such as a cylindrical or rectangular battery, current collection is performed by welding a tab terminal to the central portion and the winding core portion of the electrode group, bending the tab terminal, and welding the tab terminal to the safety element and the sealing pin. However, since bending is a complicated processing technique and is poor in manufacturability, it is necessary to leave a space necessary for preventing an internal short circuit in the battery or to insert an insulating plate between tab terminals of the electrode group. Further, when stress is applied to the portion of the electrode to which the tab terminal is welded, the separator is crushed or the electrode is deformed, so that the tab terminal must be protected by an insulating tape or a space must be provided in the core portion. Therefore, coin-shaped and button-shaped flat nonaqueous electrolyte secondary batteries having a small battery internal volume cannot adopt the current collecting method of such cylindrical and rectangular lithium ion secondary batteries.

Therefore, the present inventors have adopted a method of exposing a conductive positive electrode constituent material on one end surface of a laminated electrode group (a surface horizontal to the flat surface of a flat battery); the negative electrode constituent material having conductivity is exposed on the other end face, and the electrode constituent materials exposed respectively are brought into contact with the positive and negative electrode battery cases so as to secure current collection of the electrode group and the battery cases. In this way, it is not necessary to provide an unnecessary space or insulating plate between the electrode group and the battery case, and the discharge capacity can be increased. In addition, short circuit between the battery case or the electrode and the tab terminal is not generated, and safety and reliability are also improved.

Further, since the contact area between the electrode constituent material and the battery case is significantly larger than the contact area between the tab terminal and the battery case in the past, the current can be stably collected, and the complicated work that has been necessary in the past, that is, the welding work of the tab terminal and the battery case can be avoided.

Of course, if the electrode constituent material and the battery case are welded, or fixed with an adhesive having conductivity, or a current collector net is interposed between the electrode constituent material and the battery case after the current collecting method of the present invention is employed, the electrode constituent material and the battery case can be further kept in good electrical contact.

Next, in the present invention, when the electrode unit is wound to form the electrode group, the positive and negative electrode facing surfaces of the electrode unit may be in the horizontal direction or in the vertical direction with respect to the flat surface of the flat battery, but the horizontal direction is preferable. This is because the positive electrode constituent material having conductivity is structurally exposed to one end of the electrode group; the negative electrode constituent material having conductivity is exposed to the other end and is brought into contact with the battery case, respectively, thereby ensuring current collection.

The current collection method in the case of such a wound electrode group is: exposing one end surface (a surface horizontal to the flat surface of the flat battery) of the conductive positive electrode constituent material to the electrode group; the negative electrode constituent material having conductivity is exposed to the other end face, and the electrode constituent materials are brought into contact with the battery cases of the positive electrode and the negative electrode, respectively. With this configuration, it is not necessary to provide an extra space or insulating plate between the electrode group and the battery case, and the discharge capacity can be increased. And also does not short-circuit the battery case or the electrode and the tab terminal, so that safety and reliability are excellent.

As shown in fig. 2, the positive electrode and the negative electrode in a belt shape are wound while facing each other (facing each other) with a separator interposed therebetween. This is good in that the electrode can be effectively used from the opening to the end of the winding. Further, since there is no space in the center of the winding core of the wound electrode, even when a flat spiral electrode is used, two electrodes face each other at the beginning of winding, and therefore, the electrodes can be effectively used.

Further, the wound electrode group may be left as it is, but it is preferable to apply pressure after winding; so that the positive and negative electrodes passing through the spacer are better adhered to each other. In the coin-shaped and button-shaped flat nonaqueous electrolyte secondary batteries having a small internal volume, if there is no space in the center of the winding core of the wound electrode, the number of electrodes to be mounted can be increased by that amount, and the positive and negative electrodes can be more closely attached to each other via the separator. The flat spiral electrode is folded and wound while the two electrodes are opposed to each other, so that the opposed faces of the positive electrode and the negative electrode are in a horizontal direction with respect to the flat surface of the flat battery. Further, when the R portion of the side surface of the electrode group is fixed with a tape or the electrode and the separator are bonded, the winding displacement does not occur, and the effect is more excellent.

In addition, in the flat battery having the sealing structure of the present invention, since the battery case is subjected to a stress in a direction perpendicular to the flat surfaces of the negative electrode case and the positive electrode case by caulking (caulking), the adhesion between the electrode group and the battery case is improved, and smooth charging and discharging can be performed, thereby improving the battery characteristics. The electrode constituent material exposed portion of the electrode group and the electrode case may be directly connected to each other, or may be indirectly electrically connected to each other by a metal foil, a metal mesh, a metal powder, a carbon filler, a conductive paint, or the like.

The following description will be made of the electrode, and the positive and negative electrodes of the electrode can be formed by conventional methods using a particulate mixture and a method of filling a mixture in a metal substrate such as a metal mesh or nickel foam. In view of the ease of manufacturing a thin electrode, it is preferable to apply the slurry-like mixture to a metal foil and dry the mixture, and a method of rolling the mixture may be used. In the case of using an electrode in which the metal foil is coated with the mixture layer containing the active material, the electrode in the electrode group is preferably structured such that the active material layers are formed on both surfaces of the metal foil, and the electrode on both end surfaces of the electrode group, that is, the electrode in contact with the battery case, is preferably exposed, particularly the metal foil, among the electrode constituent materials, in order to reduce the contact resistance. In this case, the active material layer may be formed only on one surface of the electrode on the end surface, or the active material layer on only one surface may be removed after the active material layers have been formed on both surfaces.

The positive electrode active material and the negative electrode active material used in the battery of the present invention are described below.

The present invention focuses on the structure of a battery including an electrode, and the positive-electrode active material is not limited, and MnO may be used₂、V₂O₅、Nb₂O₅、LiTi₂O₄、Li₄Ti₅O₁₂、LiFe₂O₄Metal oxides such as lithium cobaltate, lithium nickelate and lithium manganate, or graphite fluoride and FeS₂And inorganic compounds, or organic compounds such as polyaniline and polyacene structures. Among them, lithium cobaltate, lithium nickelate, lithium manganate and mixtures thereof, or lithium-containing oxides in which a part of these elements is substituted with other metal elements are more preferable from the viewpoint of high operating voltage and good cycle characteristics, and in a flat-shaped nonaqueous electrolyte secondary battery which may be used for a long period of time, from the viewpoint of large capacity, weak reactivity with an electrolyte solution and moisture, and stable chemical properties,lithium cobaltate is preferably used.

The negative electrode active material is not limited, and metallic lithium, lithium alloys such as Li-Al, Li-In, Li-Sn, Li-Si, Li-Ge, Li-Bi, and Li-Pb, organic compounds such as polyacene structures, carbonaceous materials capable of absorbing and desorbing lithium, or Nb₂O₅、LiTi₂O₄、Li₄Ti₅O₁₂And oxides of silicon containing Li, oxides of tin containing Li, Li₃Nitride such as N, and the like. A carbonaceous material capable of absorbing and releasing Li is excellent in terms of good cycle characteristics, low operating potential and large capacity, and particularly, natural graphite, expanded graphite, artificial graphite, a fired intermediate phase pitch and a fired intermediate phase pitch fiber are excellent in terms of little decrease in battery operating voltage at the end of discharge₀₀₂A carbonaceous material having a developed graphite structure and having a surface-to-surface spacing of 0.338nm or less is preferable.

Further, in the flat nonaqueous electrolyte secondary battery having the above-mentioned laminate-shaped, wound-shaped or folded electrode group, the adhesion between the battery case of the positive and negative electrodes and the electrode group has a large influence on the battery resistance and the battery performance. For example, when stored in a high-temperature atmosphere of about 60 ℃ for a long period of time, the nonaqueous electrolyte decomposes, swelling of the battery occurs, the degree of adhesion between the battery case and the electrode group is significantly reduced, and the battery performance is reduced. In addition, when the flat nonaqueous electrolyte secondary battery is in an abnormal state such as a short circuit, a significant temperature rise occurs, and as a result, the nonaqueous electrolyte is decomposed, the solvent is vaporized, and the internal pressure of the battery rises, causing a problem such as battery cracking.

In contrast, in the present invention, with respect to these problems, Ethylene Carbonate (EC) and Gamma Butyrolactone (GBL) are used as the main solvents of the nonaqueous electrolyte; lithium fluoroborate was used as a supporting salt. Therefore, the generation of gas can be suppressed even at high temperatures, and the battery can be prevented from rupturing.

The mixed solvent of EC and GBL can maintain stability to the graphitized carbon negative electrode, and hardly causes solvent decomposition on the negative electrode side. Further, the stability at high potential is high, and gas generation due to decomposition of the positive electrode-side nonaqueous electrolyte is hardly caused even when the battery is left in a high-temperature atmosphere for a long time. Since EC and GBL have high boiling points (about 240 ℃ and 200 ℃), even when the battery generates heat due to a short circuit or is placed in an abnormal environment of about 150 ℃, the vapor pressure of the solvent can be kept low and decomposition is less likely to occur. Therefore, the internal pressure of the battery can be prevented from rising and the battery can be prevented from rupturing.

The mixing ratio of EC and GBL is preferably 0.3 to 1.0 in terms of the volume ratio of EC to GBL. This is because when the volume ratio of EC is low, a protective film cannot be sufficiently formed on the surface of the carbon material constituting the negative electrode during charge and discharge, resulting in a decrease in cycle characteristics, and when the volume ratio of EC is too high, lithium ions are difficult to move in a low-temperature atmosphere, resulting in a decrease in low-temperature characteristics.

Using lithium fluoroborate (LiBF)₄) As the supporting salt, the reason is: the supporting salt is generally LiBF₄6 lithium phosphate fluoride (LiBF)₆) Lithium perchlorate (LiCIO)₄) Lithium trifluoromethanesulfonate (LiCF)₃SO₃) From the viewpoints of the phase property with the graphitized carbon negative electrode, the stability at high potential, and the stability in high-temperature atmosphere, LiBF₄Preferably. For example, in the case of LiB6₄And LiCoO₄In the case of (3), if a graphitized carbon negative electrode is used as the negative electrode active material; further, when a mixed solvent of EC and GBL is used as the solvent for the nonaqueous electrolyte, the solvent is slightly decomposed on the negative electrode surface, which is not preferable. And, LiCF₄SO₃The conductivity of (b) is low, and the originally intended heavy-load discharge characteristics are poor. On the other hand, LiBF₄And LiPF₆And LiCoO₄In contrast, the heavy load discharge characteristics are slightly inferior. However, the decomposition of the solvent was controlled, so that the case was good, and LiBF was used₄The addition concentration of (B) is increased from the usual 0.5mol/l to 1.0mol/l to 1.3mol/l to 1.8mol/l, so that the heavy load characteristic is improved and the LiPF is obtained₆And LiCoO₄Equivalent heavy load characteristics.

In addition, the conventional positive electrode active material uses an oxide containing lithium cobaltate; lithium ion secondary batteries using carbonaceous materials as negative electrode active materials have a disadvantage that the materials contained in the positive electrode member dissolve in the electrolyte during long-term storage, and precipitate on the surface of the negative electrode, resulting in an increase in internal resistance. In contrast, ferrite stainless steel containing chromium and molybdenum (JP-A-63-124358), austenitic stainless steel containing chromium and molybdenum (JP-A-6-111849), and molybdenum-containing ferrite stainless steel with an increased amount of chromium (JP-A-2-126554) have been proposed as materials for positive electrode cases. However, even when stainless steel is used for a nonaqueous electrolyte battery having a battery voltage of 4V or more, the dissolution of the positive electrode member during long-term storage cannot be completely prevented.

In response to this problem, the present invention comprises: as the positive electrode case or the component of the metal part electrically connected with the positive electrode substance, stainless steel is used, which further contains 0.1-0.3% of niobium, 0.1-0.3% of titanium and 0.05-0.15% of aluminum in ferrite stainless steel containing 28.50-32.00% of chromium and 1.50-2.50% of molybdenum. Alternatively, the method comprises using a stainless steel in which 0.8 to 0.9% niobium, 0.05 to 0.15% titanium, and 0.20 to 0.30% copper are further added to a ferrite stainless steel containing 20.00 to 23.00% chromium and 1.50 to 2.50% molybdenum. By using stainless steel of such a material, the positive electrode member can be prevented from being dissolved during long-term storage.

However, when these flat nonaqueous electrolyte secondary batteries are assembled to the whole machine, generally, the lead terminal is welded to the outside of the negative electrode case by resistance welding, and the terminal portion and the whole machine are welded and assembled by soldering. In this case, the flat nonaqueous electrolyte secondary battery is obtained by laminating or winding thin positive and negative electrodes having a thickness of 1mm or less and a polyethylene or polypropylene film separator having a thickness of 0.5mm or less. Further, since the positive electrode case and the negative electrode case are directly in contact with each other, when a voltage of about 500V is applied to the battery case, heat generated during welding is transmitted to the electrode and the separator through the battery case, the separator is perforated to cause shrinkage, capacity deterioration, and short circuit in the battery, and current is concentrated on the welded portion, so that a failure such as the electrode connected to the welded portion being peeled off from the current collector occurs, and the battery function is deteriorated. Further, when the output at the time of welding is reduced, the above-described failure does not occur any more, but since the welding strength is reduced, the lead terminals are detached, and the contact between the battery and the lead terminals is defective. Further, even if the welding method of the lead terminals is changed to laser welding, the generation of heat cannot be suppressed, and the same trouble is caused.

In order to prevent the above-described failure, the present invention also provides a metal mesh between the positive electrode case and/or the negative electrode case and the electrode group. Thus, the concentrated heat generated when the lead terminals are welded can be dispersed, and the electrode and the separator in the battery case can be prevented from being damaged.

In order to prevent the above-described failure, there is another method of providing a non-metallic heat insulating material between the positive electrode case and/or the negative electrode case and the thin film sheet. Thus, heat generated when the lead terminal is welded can be blocked, and heat can be prevented from being transmitted into the electrode group, so that the electrode and the spacer in the battery can be prevented from being damaged. The setting method of the heat insulation material can be as follows: the current collecting part of the electrode assembly contacting the battery case is formed in a U-shape, and the heat insulating material is held in the U-shape. By adopting the method, the purpose can be achieved under the condition of uncomplicated structure.

The metal mesh may be shaped to form a gap with the battery case, and the electrolyte may be poured into the gap. The metal mesh may be a wire mesh, expanded alloy, punched metal or foam, or the like. The electrolyte in the voids has the effect of suppressing heat and voltage concentration. The shape and the opening degree of the current collector are not particularly limited.

Furthermore, the thickness of the metal mesh, plus the thickness of the shell, can be problematic. If the thickness is too thin, the effect of decomposing the concentration of heat is reduced, and the intended purpose cannot be achieved. Conversely, if the thickness is too large, the concentration of heat can be dispersed, but the number of electrodes that can be incorporated into the battery decreases, resulting in a decrease in battery capacity.

In view of these circumstances, it is most preferable to set the total thickness of the positive or negative electrode case and the metal mesh to 0.30mm to 0.45 mm.

Further, when the metal mesh is welded to the inner surface of the battery case in advance, the adhesion can be improved, and the metal mesh has good conductivity and a good effect. The material of the metal mesh may be any one. However, when a substance having a high potential such as a metal oxide is used for the positive electrode, if a metal mesh having a lower dissolution potential than that of the positive electrode substance is used, the potential is high during storage of the battery, and deterioration occurs, which affects the battery performance. Therefore, stainless steel containing a large amount of aluminum and titanium or chromium and molybdenum is preferably used for the metal mesh on the positive electrode side. Since the metal mesh on the negative electrode side has a much lower potential than the positive electrode, it is not necessary to consider corrosion resistance as in the positive electrode, and stainless steel, nickel, copper, or the like can be used. In order to reduce the contact resistance between the electrode group and the metal mesh, it is preferable to coat the surface of the metal mesh with a conductive coating material.

Further, a method of providing a heat insulating material between the battery case and the separator is: as the non-metallic heat insulating material, a glass material, a fluororesin such as Polytetrafluoroethylene (PTFE), tetrafluoroethylene-6-fluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), perfluoro (substituted) alkyl vinyl ether copolymer (PFA), or polyvinylidene fluoride (PVDF), a resin selected from polyimide, Liquid Crystal Polymer (LCP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), Polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and acetate resin, which is stable to an electrolyte solution and lithium ions, is preferably used; in order to prevent the heat generated during terminal welding from melting the heat insulating material and affecting the battery performance, the heat insulating material with heat resistance of more than 150 ℃ is preferably adopted; the glass material is preferably selected from the group consisting of PTFE, FEP, ETFE, PFA, PVDF, and other fluorine resins, and polyimide, LCP, PPS, and PBT.

Further, regarding the form, a material having flexibility such as a film, a woven fabric, a nonwoven fabric, or a fiber is preferable, and the adhesion with the electrode current collecting member is good, and the heat insulating effect is good. Further, a tape-shaped product obtained by coating a binder on one surface or both surfaces of a base material made of these materials is excellent in performance, and can prevent positional displacement of the electrode current collecting member and the heat insulating material, etc., and is more effective. Further, the shape of the heat insulator is not particularly limited, but when the terminal is welded, it is more effective to make the area of the heat insulator larger than the area of the current collecting portion of the electrode group in order to have a degree of freedom in the position and direction of the terminal.

If the thickness of the heat insulating material is too small, the heat insulating effect is insufficient, and the intended purpose cannot be achieved. On the other hand, if the thickness is too large, the amount of active material incorporated into the battery decreases, resulting in a decrease in battery capacity. In view of these circumstances, the thickness of the heat insulating material is preferably set to 0.05mm to 0.2 mm.

In addition, the flat nonaqueous electrolyte secondary battery of the present invention has a large electrode area and generates a large current, and therefore, a large amount of gas may be generated to cause battery rupture in the event of an accident such as an internal short circuit or an over-discharge. However, since it is impossible to provide a rupture prevention device such as a safety element in the battery structure as in the conventional cylindrical battery, if a large amount of gas is abnormally generated, the battery may be ruptured, the substances and the container in the battery may be scattered, and the used equipment may be damaged, which may cause damage to the human body.

Therefore, the flat nonaqueous electrolyte secondary battery of the present invention can adopt the following configuration in order to prevent battery rupture and improve safety. That is, a notch is provided on a side portion of the positive electrode case. Even if the notch is provided in this way, the insulating gasket is compressed in the radial direction and the height direction in a normal state, so that liquid leakage does not occur, but the insulating gasket can be opened by the notch when the internal pressure is increased by thermal breakdown, and the battery can be prevented from being broken.

In order to reliably avoid the breakage in the thermal breakdown state and to prevent the occurrence of a failure such as liquid leakage in a normal use state, it is preferable that the width of the notch provided in the side surface portion of the positive electrode case is set to 0.1 pi to 0.9 pi rad relative to the circumference of the positive electrode case and the depth of the notch is set to 5 to 30% of the height of the positive electrode case, as shown in the following experiment.

In addition, the invention forms a vertical groove on the sealing part of the positive electrode shell and forms a thin plate part so as to discharge gas to the outside of the battery when the internal pressure of the battery is increased due to abnormal gas generated in the battery. That is, the vertical groove thin plate portion of the sealing portion of the positive electrode case is pushed upward by the negative electrode case due to the increase of the internal pressure, and the vertical groove thin plate portion is deformed and broken, so that the negative electrode case is opened like two shells at a low pressure, and the gas is discharged to the outside of the battery. Therefore, it is possible to avoid breakage such as separation of the negative electrode case from the battery base body and scattering together with the battery internal material.

In the present invention, at least one fracture groove having a concave cross-section may be formed in the negative electrode case to prevent the battery from breaking as described above. Thus, for example, even in an abnormal state such as a short circuit due to an error in a method of using the battery, the rupture or explosion of the battery can be prevented by opening the crush groove. Further, since the crush grooves having a concave cross section are provided in the negative electrode case, they are not affected by the electrolyte and the positive electrode active material (oxidant) and are not corroded. Further, the crush groove is preferably formed on the outer surface of the negative electrode can so as to operate normally even in an abnormal condition.

Further, in the flat nonaqueous electrolyte secondary battery, the volume of the active material greatly changes according to charge and discharge, and the electrode group shrinks during discharge, so that the contact with the battery case is not maintained, the internal resistance increases, and a voltage drop occurs during large current discharge. In order to prevent this, the present invention may be configured such that the inner surface of one or both of the positive and negative electrode battery cases is provided with projections and depressions. If the diameter of the projection size is 0.2 to 2.0mm and the height is 0.01 to 0.50mm, good effects can be obtained. The number of the projections may be single or plural. Instead of the projections, projections and depressions such as embossing (embossing) may be provided.

Furthermore, the invention described above is believed to be primarily directed to flat round cells having an outermost diameter greater than the overall height of the cell, such as coin-shaped and button-shaped cells. However, the battery of the present invention is not limited to this type, and can be applied to a flat battery having a special shape such as an oval shape or a rectangular shape.

Drawings

Hereinafter, examples of the present invention and comparative examples will be described in detail with reference to the accompanying drawings.

Fig. 1 is a sectional view of a battery of example 1 of the present invention.

Fig. 2 is a sectional view of a battery of example 5 of the present invention.

Fig. 3 is a sectional view of a battery of example 7 of the invention.

Fig. 4 is a sectional view of a conventional flat nonaqueous electrolyte secondary battery.

Fig. 5 is a cross-sectional view of the flat nonaqueous electrolyte secondary battery of comparative example 3.

Fig. 6 is a sectional view of a battery of example 22 of the invention.

Fig. 7 is a sectional view of a battery of example 28 of the invention.

FIG. 8 is a detailed cross-sectional view of the insulation portion of FIG. 7.

Fig. 9 is a sectional view of a battery of example 40 of the present invention.

Fig. 10 is an oblique view of the positive electrode casing of fig. 9.

Fig. 11 is a sectional view of a battery of example 44 of the invention.

Fig. 12 is an external view of fig. 11.

Fig. 13 is a cross-sectional view of the positive electrode case of fig. 11 cut into a circular sheet shape.

Fig. 14 is a sectional view of a battery of example 16 of the invention.

Fig. 15 is an upper view of the negative housing of fig. 14.

Fig. 16 is an upper view of a negative electrode can of example 47 of the present invention.

Fig. 17 is an upper view of a negative electrode can of example 48 of the present invention.

Fig. 18 is an upper view of a negative electrode casing of example 49 of the invention.

Fig. 19 is an upper view of a negative electrode can of example 50 of the present invention.

Fig. 20 is an upper view of a negative electrode can of example 51 of the present invention.

Fig. 21 is an upper view of a negative electrode can of example 52 of the present invention.

Fig. 22 is a top view of a negative electrode can of comparative example 23.

Fig. 23 is a sectional view of a battery of example 53 of the present invention.

Fig. 24 is a top view of fig. 23.

Fig. 25 is a sectional view of a battery according to example 56 of the present invention.

Fig. 26 is a top view of fig. 25.

Detailed Description

< example 1>

A method for manufacturing a battery according to embodiment 1 of the present invention will now be described with reference to the sectional view of fig. 1.

First, LiCoO with a mass ratio of 100₂Acetylene black with the mass ratio of 5 and graphite powder with the mass ratio of 5 are added as conductive agents to increase the massPolyvinylidene fluoride fibers having a ratio of 5 were used as a binder, and diluted and mixed with N-methylpyrrolidone to obtain a slurry-like positive electrode mixture. Then, the positive electrode mixture was applied to one surface of an aluminum foil having a thickness of 0.02mm as a positive electrode current collector 2a by a doctor blade method and dried, and this application and drying operation was repeated until the thickness of the coating film layer containing the active material reached 0.39mm, and a film layer 2b containing the positive electrode active material was formed on one surface of the aluminum foil to prepare a single-surface-coated positive electrode.

Subsequently, both sides of the aluminum foil were coated by the same method as the one-side coated positive electrode to prepare a both-side coated positive electrode in which the thickness of the film layer containing the positive electrode active material was 0.39mm per side.

Next, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were added to 100 mass ratio of the graphitized mesophase pitch carbon fiber powder, and diluted and mixed with ion-exchanged water to obtain a slurry negative electrode mixture. The negative electrode mixture was repeatedly applied and dried to a copper foil having a thickness of 0.02mm as a negative electrode current collector 4a to form a film layer 4b having a thickness of 0.39mm and containing the active material, thereby producing a single-coated negative electrode.

Next, a double-coated negative electrode was produced by coating both surfaces of a copper foil in the same manner as in the single-coated negative electrode so that the thickness of the coating film of the layer containing the negative-electrode-acting material became 0.39mm per surface.

These electrodes were cut into a square shape of 13mm in width and 13mm in length, and a protrusion of 6mm in width and 2mm in length was formed on one side of each electrode, and then the film layer containing the active material formed on the protrusion was scraped off to expose the aluminum foil or copper foil as a current-carrying portion, thereby producing a positive electrode sheet and a negative electrode sheet coated on both sides and one side of the active material layer, each sheet having a square shape of 13mm in width and 13mm in length.

Then, on the film layer-forming part containing the positive electrode active material of the single-side coated positive electrode sheet, a double-side coated negative electrode sheet was arranged facing each other through a separator 3 composed of a polyethylene microporous film having a thickness of 25 μm. In this case, the current-carrying portion of the negative electrode is located on the opposite side of the current-carrying portion of the positive electrode sheet. Then, the double-coated positive electrode sheet is disposed so that the current-carrying portion faces in the same direction as the previous positive electrode sheet, and the single-coated negative electrode sheet is disposed on the upper face thereof so as to face through the separator 3. In this case, the film layer 4b containing the negative-electrode active material coated on one side of the negative-electrode sheet was brought into contact with the separator surface, and the current-carrying portion of the single-coated negative-electrode sheet was oriented in the same direction as the current-carrying portion of the previous negative-electrode sheet. Thus, an electrode group shown in fig. 1 was produced. That is, the positive electrode conducting portion is entirely exposed from the left side of the illustrated electrode group; all the negative electrode conducting portions are exposed from the right side of the illustrated electrode group, and the exposed conducting portions are electrically connected.

The electrode assembly thus produced was dried at 85 ℃ for 12 hours and then arranged so that the uncoated side of the electrode assembly, which was coated on one side with the negative electrode sheet (i.e., the negative electrode current collector 4a), and the insulating gasket 6 (having an opening diameter of 20mm and an opening area of 3.14 cm)²) The inner bottom surface of a negative electrode metal case 5 constituting an integral body is brought into contact with each other, and then a nonaqueous electrolyte in which LiPF is dissolved at a ratio of 1mol/l in a solvent prepared by mixing Ethylene Carbonate (EC) and Methyl Ethyl Carbonate (MEC) at a volume ratio of 1: 1 is injected₆As a supporting salt, a stainless-steel positive electrode case 1 was fitted so as to be in contact with the uncoated side of the electrode group on one side of the coated positive electrode sheet (i.e., the positive electrode collector 2a), and after being turned upside down, the positive electrode case was caulked and sealed to produce a flat nonaqueous electrolyte secondary battery shown in fig. 1 having a thickness of 3mm and a diameter of 24.5 mm. The number of faces passing through the facing faces of the positive and negative electrodes of the battery separator was 3 in total, and the total facing area of the positive and negative electrodes was 5.1cm²。

< example 2>

The coating film thickness of the film layer containing the active material on each of the positive and negative electrodes in the electrode group was 0.22mm, and the number of laminated sheets in which the positive electrode was coated on both sides and the negative electrode was coated on both sides in the middle part of the electrode group was 2, respectively, and the other battery production methods were the same as in example 1. Through the separator of the cellThe number of the faces of the opposite faces of the positive and negative electrodes is 5, and the sum of the opposite areas of the positive and negative electrodes is 8.5cm²。

< example 3>

The coating film thickness of the film layer containing the active material on each of the positive and negative electrodes in the electrode group was 0.15mm, and the number of laminated sheets in which the positive electrode was coated on both sides and the negative electrode was coated on both sides in the middle part of the electrode group was 3, respectively, and the other battery production methods were the same as in example 1. The number of faces of the opposite faces of the positive and negative electrodes passing through the separator was 7 in total, and the total of the opposite areas of the positive and negative electrodes was 11.8cm²。

< example 4>

The coating film thickness of the film layer containing the active material on each of the positive and negative electrodes in the electrode group was 0.11mm, and the number of laminated sheets in which the positive electrode was coated on both sides and the negative electrode was coated on both sides in the middle part of the electrode group was 4, respectively, and the other battery production methods were the same as in example 1. The number of faces of the opposite faces of the positive and negative electrodes passing through the separator was 9 in total, and the total of the opposite areas of the positive and negative electrodes was 15.2cm²。

< comparative example 1>

Comparative example 1 is explained below with reference to fig. 4.

LiCoO at a mass ratio of 100₂Acetylene black with the mass ratio of 5 and graphite powder with the mass ratio of 5 are added as conductive agents; and adding 5 mass percent of polyvinyl fluoride as a binder, mixing, crushing, and preparing into a granular positive electrode mixture. Then, the positive electrode pellet mixture was press-molded to obtain a positive electrode sheet 12 having a diameter of 19mm and a thickness of 1.15 mm.

Then, Styrene Butadiene Rubber (SBR) and carboxymethyl cellulose (CMC) as binders were added to 100 mass ratio of the graphitized mesophase pitch (メソフエ - ズピッチ) carbon fiber powder, respectively, and mixed, dried, and pulverized to prepare a granular negative electrode mix. The negative electrode pellet mixture was press-molded to obtain a negative electrode sheet 14 having a diameter of 19mm and a thickness of 1.15 mm.

Then, the positive and negative electrode circular sheets were dried at 85 ℃ for 12 hours and then adhered to the opening area of 314cm²The insulating gasket 6 of the negative electrode casing 5 constituting an integral body was sequentially provided with a negative electrode sheet 14, a separator 13 made of a polypropylene nonwoven fabric having a thickness of 0.2mm and a positive electrode sheet 12, and a nonaqueous electrolyte in which LiPF was dissolved at a ratio of 1mol/l in a solvent prepared by mixing ethylene carbonate and methyl ethyl carbonate at a volume ratio of 1: 1 was injected₆As a supporting salt. Then, the positive electrode case 1 made of stainless steel was fitted and the upper and lower sides were turned upside down, and the positive electrode case was subjected to caulking processing to obtain a flat nonaqueous electrolyte secondary battery having a thickness of 3mm and a diameter of 24.5 mm. The number of faces passing through the opposite faces of the positive and negative electrodes of the battery separator was 1 face, and the total of the opposite areas of the positive and negative electrodes was 2.8cm²。

< comparative example 2>

By the method described in example 1, 1 positive electrode and 1 negative electrode were coated with the active material layer on the separator side, with the coating film thickness of the active material-containing film layer being 1.24mm on each side, and the battery was produced in the same manner as in example 1. Therefore, the number of faces of the battery passing through the facing faces of the positive and negative electrodes of the separator was 1 in total, and the total of the facing areas of the positive and negative electrodes was 1.7cm²。

The batteries of the present example and comparative example fabricated as described above were initially charged for 48 hours under constant current and constant voltage conditions of 4.2V and 3 mA. Then, the discharge was carried out at a constant current of 30mA until it became 3.0V, and the discharge capacity under heavy load was determined. The results are shown in Table 1.

TABLE 1

	Kind of electrode	Thickness (mm) of the layer containing the active substance	Number of opposite faces of positive and negative poles	Sum of opposing areas of positive and negative electrodes (cm)²)	Discharge capacity (mAh) under heavy load
	Kind of electrode	Thickness (mm) of the layer containing the active substance	Number of opposite faces of positive and negative poles		Discharge capacity (mAh) under heavy load	Comparative example 1	Wafer electrode	1.15	1	2.8	6.4
Comparative example 2	Coated electrode	1.24	1	1.7	2.4	Comparative example 1	Wafer electrode	1.15	1	2.8	6.4
Comparative example 2	Coated electrode	1.24	1	1.7	2.4	Example 1	Coated electrode	0.39	3	5.1	22.8
Example 2	Coated electrode	0.22	5	8.5	52.7	Example 1	Coated electrode	0.39	3	5.1	22.8
Example 2	Coated electrode	0.22	5	8.5	52.7	Example 3	Coated electrode	0.15	7	11.8	53.7
Example 4	Coated electrode	0.11	9	15.2	52.5	Example 3	Coated electrode	0.15	7	11.8	53.7

As can be seen from table 1: each of the batteries of the present example had a significantly increased discharge capacity during heavy load discharge, as compared with the battery of comparative example 1 (the battery using the disk-shaped electrode produced by the conventional pellet mix molding method and having the facing areas of the positive and negative electrodes smaller than the opening area of the gasket) and the battery of comparative example 2 (the battery having only one facing surface of the positive and negative electrodes and having the facing area smaller than the opening area of the gasket).

In the embodiment of the present invention, the flat nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte is the nonaqueous solvent is used, but it is needless to say that a polymer secondary battery using a polymer electrolyte as the nonaqueous electrolyte and a solid electrolyte secondary battery using a solid electrolyte can be applied. Instead of the resin separator, a polymer film or a solid electrolyte membrane may be used. The shape of the battery was described based on a coin-shaped nonaqueous electrolyte sealed by a positive electrode can caulking process. However, the positive and negative electrodes may be replaced and the negative casing may be sealed by riveting. Further, the shape of the battery does not need to be a positive shape, and the battery is also applicable to a flat nonaqueous electrolyte secondary battery having a special material shape such as an oval shape or a rectangular shape.

Next, examples of the battery of the present invention having a wound electrode group will be described in detail.

< example 5>

Fig. 2 is a sectional view of a battery of example 5 of the present invention.

The method for producing the battery of example 5 is explained below in detail.

First, at a mass ratio of 100 LiC₀O₂Acetylene black and graphite powder were added in a mass ratio of 5 as a binder, polyvinylidene fluoride was added in a mass ratio of 5, and the mixture was diluted and mixed with N-methylpyrrolidone to prepare a slurry-like positive electrode mixture. Then, the positive electrode mixture was applied to one surface of an aluminum foil having a thickness of 0.02mm as a positive electrode current collector by a doctor blade method and dried, and this application and drying were repeated until the thickness of the coating film of the film layer containing the positive electrode active substance reached 0.15mm on both surfaces, and the film layer 2b containing the positive electrode active substance was formed on one surface of the aluminum foil. Then, the film layer containing the active material was removed from the part 10mm away from the end portion of one surface of the electrode body to expose the aluminum layer, and the electrode body was cut into a shape having a width of 15mm and a length of 120mm as a current carrying part to obtain a positive electrode sheet.

Then, Styrene Butadiene Rubber (SBR) and carboxymethyl cellulose (CMC) were added to the graphitized mesophase pitch carbon fiber powder at a mass ratio of 100 in a mass ratio of 2.5, respectively, and diluted with ion-exchanged water and mixed to prepare a slurry-like negative electrode mixture. This negative electrode mixture was repeatedly applied and dried to a copper foil having a thickness of 0.02mm as a negative electrode current collector in the same manner as in the case of the positive electrode, so that the thickness of the film layer 4b containing the active material became 0.15mm, thereby producing a double-coated negative electrode. Then, the film layer containing the active substance was removed from the part of one side of the electrode body 10mm away from the end part to expose the copper layer, and the electrode body was cut into a shape having a width of 15mm and a length of 120mm as a negative electrode sheet using the copper layer as a current carrying part.

Then, the positive and negative electrode current-carrying parts were wound around the outer periphery of the tail part, and a separator 3 made of a polyethylene microporous film 25 μm in thickness was inserted between the positive and negative electrode sheets, and then the sheet was wound into a spiral shape, and pressure was applied in a predetermined direction so that the opposite surfaces of the positive and negative electrodes were in the horizontal direction with respect to the flat surface of the flat battery. The pressurization is performed until the space in the center of the wound electrode disappears. The total of the opposed areas of the positive and negative electrodes of the battery with the separator interposed was 34.5cm²。

The electrode assembly thus produced was dried at 85 ℃ for 12 hours and then arranged so that the uncoated side of the single-sided coated negative electrode sheet of the electrode assembly was in contact with the inner bottom surface of a negative electrode metal case 5 having an open surface area of 3.14cm²And an insulating gasket 6 having an opening diameter of 20mm is integrally formed. Then, a nonaqueous electrolyte in which LiPF is dissolved at a ratio of 1mol/l in a solvent prepared by mixing EC and MEC at a volume ratio of 1: 1 was injected₆Further, the stainless steel positive electrode case 1 was fitted and connected to the uncoated side of the single-sided coated positive electrode sheet of the electrode group, and after being turned upside down, the positive electrode case was crimped (caulked) and sealed to produce the flat nonaqueous electrolyte secondary battery of example 5 having a diameter of Φ 24.5 mm.

< example 6>

The strip-shaped positive electrode and negative electrode with the separator interposed therebetween are wound in a spiral shape while being folded at a predetermined distance. The opposite surfaces of the positive electrode and the negative electrode are in the horizontal plane direction relative to the flat surface of the flat battery. Further, battery production was performed as in example 5.

For the batteries of examples 5 and 6 and comparative example 1 described above, initial charging was performed for 48 hours at a constant current and constant voltage of 4.2V and 3 mA. Then, the discharge was carried out at a constant current of 30mA until it became 3.0V, and the discharge capacity was determined. The results are shown in Table 2.

TABLE 2

	Kind of electrode	Number of positive and negative electrode facing (cm)²)	30mA constant current (mAh) of discharge capacity
	Kind of electrode	Number of positive and negative electrode facing (cm)²)	30mA constant current (mAh) of discharge capacity	Example 5	Coated electrode	34.5	51.9
Example 6	Coated electrode	34.5	52.7	Example 5	Coated electrode	34.5	51.9
Example 6	Coated electrode	34.5	52.7	Comparative example 1	Wafer electrode	2.8	6.4

As can be seen from table 2: the batteries of examples 5 and 6 of the present invention had a significantly increased capacity as compared with the battery of comparative example 1 (the battery using the disk-shaped electrode produced by the conventional particle mixture molding method, in which the facing areas of the positive and negative electrodes were smaller than the opening area of the gasket). The winding method is different from the following winding method: the electrode shown in example 2 was folded and wound in a spiral shape, so that the current collection between the electrode layers was good and the heavy load characteristics were good.

The above embodiments have been described with reference to a flat nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte is a nonaqueous solvent. However, the present invention is applicable to a polymer secondary battery using a polymer electrolyte as a nonaqueous electrolyte and a solid electrolyte secondary battery using a solid electrolyte. Instead of the resin separator, a polymer film or a solid electrolyte membrane may be used. The shape of the battery was described based on a coin-shaped nonaqueous electrolyte sealed by a positive electrode can crimping method. However, the positive and negative electrodes may be changed and the sealing may be performed by a method of crimping the negative casing. The present invention is not necessarily required to be coin-shaped, and can be applied to a flat nonaqueous electrolyte secondary battery having a special shape such as an oval shape or a rectangular shape.

Next, in the present invention, examples of flat nonaqueous electrolyte secondary batteries sealed by a sealing plate without using an insulating gasket will be described.

< example 7>

The method for manufacturing the battery of this embodiment is explained with reference to the sectional view of fig. 3.

Both-side coated and single-side coated positive and negative electrode sheets of the same size were produced in exactly the same manner as in example 1. Then, an electrode group was produced using these positive and negative electrode sheets in the same manner as in example 1.

The electrode assembly thus produced was dried at 85 ℃ for 12 hours, and then a flat nonaqueous electrolyte secondary battery shown in FIG. 3 was produced from the electrode assembly by the following method. That is, the electrode group is arranged such that the uncoated side (i.e., the positive electrode collector 2a) of the electrode group is coated on one side thereofAn inner bottom surface of a positive electrode case 11 having an opening diameter of 20mm and an opening area of 3.14cm is connected²The insulation treatment was performed by applying SBR to the inner surface side. Further, a nonaqueous electrolyte in which LiPF is dissolved at a ratio of 1mol/l in a solvent prepared by mixing EC and MEC at a volume ratio of 1: 1 was injected₆As a supporting salt.

At the center of the sealing plate 7, a negative electrode terminal 8 electrically integrated with the collector electrode 10 is provided, and the uncoated side of the single-sided coated negative electrode sheet of the electrode group (i.e., the negative electrode collector 4a) is connected to the collector electrode 10. The negative electrode terminal 8 and the sealing plate 7 are electrically insulated by a glass seal 9. The positive electrode case 11 and the sealing plate 7 were sealed by laser welding to produce a flat nonaqueous electrolyte secondary battery having a total height of 5mm and a diameter of Φ 21.0 mm. The number of the facing surfaces of the positive and negative electrodes with the separator interposed therebetween was 3 in total, and the total facing area of the positive and negative electrodes was 5.1cm²。

< example 8>

The film thickness of the film layer containing the active material on each surface of the positive electrode and the negative electrode in the electrode group was 0.22 mm. The number of stacked layers of the double-coated positive electrode and the double-coated negative electrode in the middle portion of the electrode group was 2, and the other battery production methods were the same as in example 7. The number of faces of the positive and negative electrode facing faces with the separator interposed therebetween was 5 in total. The sum of the opposed areas of the positive and negative electrodes was 8.5cm²。

< example 9>

The film thickness of the film layer containing the active material on each surface of the positive electrode and the negative electrode in the electrode group was 0.15 mm. The number of stacked layers of the both-side coated positive electrode and the both-side coated negative electrode in the middle portion of the electrode group was 3, and the other battery production methods were the same as in example 7. The number of faces of the positive and negative electrode facing faces with the separator interposed therebetween was 7 in total. The sum of the opposed areas of the positive and negative electrodes was 11.8cm²。

< example 10>

The film thickness of the film layer containing the active material on each surface of the positive electrode and the negative electrode in the electrode group was 0.11 mm. The number of stacked layers of the positive electrode coated on both sides and the negative electrode coated on both sides in the middle part of the electrode was 4, and the other battery production methods were the same as in example 7. The number of faces of the battery on the opposite faces of the positive and negative electrodes with the separator interposed therebetween was 9 in total. The sum of the opposing areas of the positive and negative electrodes was 15.2cm²。

< comparative example 3>

Positive and negative electrode disks were produced in the same manner as in comparative example 1, dried at 85 ℃ for 12 hours, and then, as shown in fig. 5, a positive electrode disk 12, a separator 13 and a negative electrode disk 14 were sequentially arranged on the inner bottom surface of a positive electrode metal case 11 in the same manner as in example 7, and a nonaqueous electrolyte was injected in the same manner as in example 7, and the positive electrode case 11 and a sealing plate 7 were welded and sealed by a laser welding method to produce a flat nonaqueous electrolyte secondary battery having a total height of 5mm and a diameter of Φ 21.0mm as shown in fig. 5.

In fig. 5, the same portions as those in fig. 3 are denoted by the same reference numerals. The number of the faces of the opposite faces of the positive and negative electrodes with the separator interposed therebetween was 1, and the total of the opposite areas of the positive and negative electrodes was 2.8cm²。

< comparative example 4>

The positive electrode and the negative electrode in the motor set are respectively coated with electrodes on one side, and the coating thickness of the film layer containing the acting substances is 1.24mm respectively. Otherwise, a battery was produced in the same manner as in example 7. The area of the opposite surfaces of the positive and negative electrodes with the separator in between is 1 surface in total, and the sum of the opposite areas of the positive and negative electrodes is 1.7cm²。

The batteries of examples 7 to 10 and comparative examples 3 to 4 produced above were initially charged at a constant current and constant voltage of 4.2V and 3mA for 48 hours. Then, the discharge was performed at a constant current of 30mA until 3.0V, and the discharge capacity under heavy load was determined. The results are shown in Table 3.

TABLE 3

	Kind of electrode	Thickness (mm) of the layer containing the active substance	Number of opposite faces of positive and negative poles	Sum of opposing areas of positive and negative electrodes (cm)²)	Discharge capacity (mAh) under heavy load
	Kind of electrode	Thickness (mm) of the layer containing the active substance	Number of opposite faces of positive and negative poles		Discharge capacity (mAh) under heavy load	Comparative example 3	Pressed sheet electrode	1.15	1	2.8	4.6
Comparative example 4	Coated electrode	1.24	1	1.7	2.4	Comparative example 3	Pressed sheet electrode	1.15	1	2.8	4.6
Comparative example 4	Coated electrode	1.24	1	1.7	2.4	Example 7	Coated electrode	0.39	3	5.1	22.8
Example 8	Coated electrode	0.22	5	8.5	52.7	Example 7	Coated electrode	0.39	3	5.1	22.8
Example 8	Coated electrode	0.22	5	8.5	52.7	Example 9	Coated electrode	0.15	7	11.8	53.7
Example 10	Coated electrode	0.11	9	15.2	52.5	Example 9	Coated electrode	0.15	7	11.8	53.7

As can be seen from table 3: the batteries of the above examples had significantly increased discharge capacity during heavy-load discharge as compared with the batteries of comparative example 3, one of which was a pellet-shaped electrode produced by a conventional pellet mixture molding method; the other is comparative example 4, in which the number of the opposite surfaces of the positive and negative electrodes is only 1, and the opposite area is small.

In the above-described embodiment, the description has been made using the flat nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte is a nonaqueous solution, but it goes without saying that a polymer secondary battery in which a polymer electrolyte is used as the nonaqueous electrolyte and a solid electrolyte secondary battery in which a solid electrolyte is used are also applicable. Instead of the resin separator, a polymer film or a solid electrolyte membrane may be used. And the positive and negative electrodes may be changed. Further, the battery shape does not need to be a perfect circle, and a flat nonaqueous electrolyte secondary battery having a special shape such as an oval shape or a rectangular shape can be applied.

The electrolyte was studied, and examples thereof are as follows.

Experiment a, experiment for the kind of solvent of nonaqueous electrolyte

< example 11>

In the battery of the above example 5, a nonaqueous electrolyte in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent prepared by mixing gamma-butyrolactone (GBL) and EC at a ratio of 2: 1 was injected₄A flat nonaqueous electrolyte secondary battery was produced in the same manner as in example 5 except for using a supporting salt.

< comparative example 5>

A nonaqueous electrolyte in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent in which ethylene carbonate (DEC) and EC were mixed at a ratio of 2: 1 was injected₄A flat nonaqueous electrolyte secondary battery was produced as in example 5 except for using a supporting salt.

< comparative example 6>

A nonaqueous electrolyte in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent prepared by mixing methylethyl carbonate (MEC) and EC at a ratio of 2: 1 was injected₄As a supporting salt. Other systems of batteriesThe procedure was as in example 5.

The batteries of example 11 and comparative examples 5 and 6 thus produced were initially charged at a constant current and constant voltage of 4.2V and 3mA for 48 hours. Then, high-temperature storage characteristics 1, a heating test, a short-circuit test, and measurements were performed as described below to study and analyze battery characteristics. The results are shown in Table 4.

< initial discharge Capacity >

The discharge was carried out at a constant current of 30mA in the atmosphere at 20 ℃ and the discharge capacity was measured until the closed circuit voltage reached 3.0V.

< high temperature storage Property 1>

After the battery in a charged state was stored in an atmosphere at 60 ℃ for 30 days, the total height of the battery was measured, and then, the battery was discharged at a constant current of 30mA in an atmosphere at 20 ℃ to measure the discharge capacity until the closed-circuit voltage reached 3.0V. The ratio (maintenance ratio) of the capacity after high-temperature storage to the initial discharge capacity is shown in Table 4.

< Heat test >

The battery was heated to 150 ℃ at a temperature rise rate of 5 ℃/min and maintained at 150 ℃ for 3 hours, and the battery state was observed. The number of cells that broke by this test is shown in table 4.

< short-circuit test >

Cross-sectional area of 1.3mm at room temperature²The copper wire of (a) connects the positive terminal and the negative terminal of the battery to short-circuit the battery in a charged state. The number of cells that broke by this test is shown in table 4.

TABLE 4

	Non-aqueous electrolyte	High temperature storage Property 1 capacity maintenance ratio after high temperature storage (%)	Number of rupture of battery after heat test/number of test	Number of rupture of battery after short-circuit test/number of test
	Non-aqueous electrolyte		Number of rupture of battery after heat test/number of test		Example 11	1.5mol/LiBF₄EC/GBL	84	0/10	0/10
Comparative example 5	1.5mol/LiBF₄EC/DEC	42	9/10	8/10	Example 11	1.5mol/LiBF₄EC/GBL	84	0/10	0/10
Comparative example 5	1.5mol/LiBF₄EC/DEC	42	9/10	8/10	Comparative example 6	1.5mol/LiBF₄EC/MEC	44	10/10	7/10

From table 4, it can be seen that: when a mixed solvent of DEC and EC and a mixed solvent of MEC and EC are used, the capacity of the battery decreases after high-temperature storage; the cell broke when the heating test and the short-circuit test were performed. In contrast, when the mixed solvent of GBL and EC is used, the capacity of the battery is reduced after high-temperature storage, and the battery is not broken even when the heating test and the short-circuit test are performed.

Experiment B, characterization of volume mixing ratio with EC

< example 12>

A nonaqueous electrolyte was injected in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent in which GBL and EC were mixed at a ratio of 10: 3₄As a supporting salt. Other methods of manufacturing the battery were the same as in example 5.

< example 13>

A nonaqueous electrolyte was injected in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent in which GBL and EC were mixed at a ratio of 1: 1₄As a supporting salt. Other methods of manufacturing the battery were the same as in example 5.

< reference example 1>

A nonaqueous electrolyte was injected in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent prepared by mixing GBL and EC at a ratio of 10: 1₄As a supporting salt. Other methods of manufacturing the battery were the same as in example 5.

< reference example 2>

A nonaqueous electrolyte was injected in which LiBF was dissolved at a ratio of 1.5mol/l in a solvent in which GBL and EC were mixed at a ratio of 2: 3₄As a supporting salt. Other methods of manufacturing the battery were the same as in example 5.

10 of the batteries of examples 11 to 13 and reference examples 1 and 2 prepared as described above were initially charged at a constant current and constant voltage of 4.2V and 3mA for 48 hours. Then, the initial discharge capacity was measured in the same manner as in experiment a, and then the discharge capacity and cycle characteristics in a low-temperature atmosphere were measured as shown below, and the battery characteristics were examined, and the results are shown in table 5.

< discharge capacity in Low temperature atmosphere >

Discharging at-30 deg.C under constant current of 30mA, and measuring the discharge capacity before the closed circuit voltage reaches 3.0V.

< periodic characteristics >

The discharge was carried out at a constant current of 30mA at 20 ℃ in the atmosphere, and the discharge capacity was measured until the closed circuit voltage reached 3.0V. Then, charging was carried out for 3 hours at a constant current and constant voltage of 4.2V and 30mA, and the charging was repeated for 100 cycles. The maintenance rate of the discharge capacity at 100 th cycle with respect to the initial discharge capacity is shown in table 5.

TABLE 5

	Non-aqueous electrolyte	Volume ratio of EC to GBL	Low temperature characteristic capacity utilization (%)	Periodic characteristic capacity maintenance ratio (%)
	Non-aqueous electrolyte	Volume ratio of EC to GBL	Low temperature characteristic capacity utilization (%)	Periodic characteristic capacity maintenance ratio (%)	Reference example 1	1.5mol/LiBF₄EC/GBL	0.1	83	68
Example 12	0.3	81	80		Reference example 1		0.1	83	68
Example 12	0.3	81	80	Example 11	0.5		80	81
Example 13	1.0	79	83	Example 11	0.5		80	81
Example 13	1.0	79	83	Reference example 2	1.5		48	83

As can be seen from this table 5: when the ratio of EC to GBL is large (reference example 2), low-temperature characteristics deteriorate; the cycle characteristics decreased when the proportion of EC was small (reference example 1). This is because when the mixing ratio of EC is decreased, the formation of the protective film on the surface of the carbon material constituting the negative electrode becomes insufficient, and GBL is decomposed.

On the other hand, the batteries of examples 11 to 13 were excellent in low-temperature characteristics and cycle characteristics.

Experiment C, experiment for supporting salt species of electrolyte

< comparative example 7>

With the exception of the supporting salt of the non-aqueous electrolyte being LiBF₆Otherwise, the other methods of manufacturing the battery were the same as those of example 11.

< comparative example 8>

With the exception of the supporting salt of the non-aqueous electrolyte being LiCoO₄Other methods of making batteriesAll as in example 11.

< comparative example 9>

Unless the supporting salt of the aqueous electrolyte is LiCF₃SO₃Otherwise, the other methods of manufacturing the battery were the same as those of example 11.

The batteries of example 11 and comparative examples 7 to 9 were initially charged at a constant current and constant voltage of 4.2V and 3mA for 48 hours. Then, after the initial discharge capacity was checked and confirmed in the same manner as in experiment a, the following conditions, that is, high-temperature storage characteristic 2 and heavy-load discharge capacity were measured to check the battery characteristics, and the results are shown in table 6.

< high temperature storage Property 2>

After the battery in a charged state was stored in an atmosphere at 60 ℃ for 30 days, the total height of the battery was measured, and the rate of increase compared with the total height before storage was calculated. Then, in the atmosphere of 20 ℃, discharge was performed at a constant current of 30mA, and the discharge capacity until the closed circuit voltage reached 3.0V was measured. The total high increase rate of the battery and the capacity maintenance rate after high-temperature storage compared to the initial discharge capacity are shown in table 6.

< discharge capacity under heavy load >

Heavy load discharge was performed at a constant current of 180mA in the atmosphere of 20 c, and the heavy load discharge capacity was measured until the closed circuit voltage reached 3.0V. The utilization of the heavy-load discharge capacity with respect to the initial discharge capacity is shown in table 6.

TABLE 6

	Non-aqueous electrolyte	High temperature storage Property 2		Heavy load characteristic capacity utilization (%)
		High temperature storage Property 2			Increase rate of total cell height (%)	Capacity maintenance ratio after high-temperature storage (%)
		Example 11	1.5mol/LiBF₄EC/GBL		Increase rate of total cell height (%)		0.0	84	80
Comparative example 7	1.5mol/LiPF₆EC/GBL	Example 11	1.5mol/LiBF₄EC/GBL	6.7	59	75	0.0	84	80
Comparative example 7	1.5mol/LiPF₆EC/GBL	Comparative example 8	1.5mol/LiClO₄EC/GBL	6.7	59	75	10.0	35	70
Comparative example 9	1.5mol/LiCF₃SO₃EC/GBL	Comparative example 8	1.5mol/LiClO₄EC/GBL	0.0	80	46	10.0	35	70

As can be seen from table 6: comparative examples 7 and 8When the battery of (3) is stored at a high temperature of 60 ℃, the nonaqueous electrolyte is decomposed to generate gas, the total height of the battery increases, the contact between the electrode and the electrode case is poor, and the internal resistance of the battery increases. Therefore, a sufficient discharge capacity cannot be obtained. The battery of comparative example 9, LiCF₃SO₃The conductivity of (2) is low, and the load discharge characteristics aimed at this point are lowered, resulting in poor effects.

On the other hand, the battery of example 11 did not generate gas and did not increase the internal resistance even when stored at high temperature, and therefore, sufficient capacity was obtained and the heavy load characteristics were good.

Experiment D, investigation experiment for characteristics of electrolyte supporting salt concentration

< reference example 3>

The battery was fabricated in the same manner as in example 11, except that the supporting salt concentration of the nonaqueous electrolyte was 1.0 mol/l.

< example 14>

The battery was fabricated in the same manner as in example 11, except that the supporting salt concentration of the nonaqueous electrolyte was 1.3 mol/l.

< example 15>

The battery was fabricated in the same manner as in example 11, except that the supporting salt concentration of the nonaqueous electrolyte was 1.8 mol/l.

< reference example 4>

The cell fabrication method of the battery was the same as that of example 11 except that the supporting salt concentration of the nonaqueous electrolyte was 2.0 mol/l.

The batteries of examples 11, 14 and 15 and reference examples 3 and 4 prepared as described above were initially charged for 48 hours at a constant current and constant voltage of 4.2V and 3mA, and the initial discharge capacity, the discharge capacity in a low-temperature atmosphere, and the discharge capacity under a heavy load were measured. The results are shown in Table 7. And, the same method as experiment a was used for the measurement of the initial discharge capacity; capacity measurement in low temperature atmosphere, using the same method as experiment B; the heavy load discharge capacity was measured by the same method as in experiment C.

TABLE 7

	Non-aqueous electrolyte	Low temperature characteristic capacity utilization (%)	Heavy load characteristic capacity utilization (%)
	Non-aqueous electrolyte	Low temperature characteristic capacity utilization (%)	Heavy load characteristic capacity utilization (%)	Reference example 3	1.0mol/LiBF₁EC/GBL	67	52
Example 11	1.3mol/LiBF₁EC/GBL	75	79	Reference example 3	1.0mol/LiBF₁EC/GBL	67	52
Example 11	1.3mol/LiBF₁EC/GBL	75	79	Example 11	1.5mol/LiBF₁EC/GBL	81	80
Example 15	1.8mol/LiBF₁EC/GBL	77	80	Example 11	1.5mol/LiBF₁EC/GBL	81	80
Example 15	1.8mol/LiBF₁EC/GBL	77	80	Reference example 4	2.0mol/LiBF₁EC/GBL	65	78

As can be seen from the table, when the concentration of the supporting salt in the nonaqueous electrolyte is in the range of 1.3mol 1 to 1.8mol/l, the migration rate of lithium ions in the nonaqueous electrolyte is optimum, and a battery having good low-temperature characteristics and heavy-load characteristics can be obtained.

Examples of the study of the cathode casing material are shown below.

< example 16>

In the above-described embodiment 5, the positive electrode case is adopted: a stainless steel sheet is used in the production, which is produced by adding 0.20 mass ratio of niobium, 0.20 mass ratio of titanium, and 0.10 mass ratio of aluminum to 28.50 to 32.00 mass percent of chromium and 1.50 to 2.50 mass percent of molybdenum, and one side of the outer wall surface is plated with nickel, and then is subjected to press working to produce a positive electrode case.

< example 17>

In the above-described embodiment 5, the positive electrode case is adopted: a stainless steel sheet is used in the production, which is produced by adding 0.10 mass ratio of niobium, 0.10 mass ratio of titanium, and 0.05 mass ratio of aluminum to 28.50 to 32.00 mass% chromium and 1.50 to 2.50 mass% molybdenum-containing ferrite stainless steel, and one side of the outer wall surface is nickel-plated and then press-worked to produce a positive electrode case.

< example 18>

In example 5, the positive electrode case was manufactured by adding 0.30 mass% niobium, 0.30 mass% titanium, and 0.15 mass% aluminum to 28.50 to 32.00 mass% chromium and 1.50 to 2.50 mass% molybdenum ferrite stainless steel, and nickel plating one side of the outer wall surface and then press working the resulting plate.

< comparative example 10>

The positive electrode case used was manufactured by adding 0.05 mass% niobium, 0.05 mass% titanium, and 0.025 mass% aluminum to a ferrite stainless steel material containing 28.50 to 32.00 mass% chromium and 1.50 to 2.50 mass% molybdenum, plating one side of the outer wall surface with nickel, and then performing press working.

< comparative example 11>

The positive electrode case used was manufactured by adding 0.40 mass% niobium, 0.40 mass% titanium, and 0.20 mass% aluminum to 28.50 to 32.00 mass% chromium and 1.50 to 2.50 mass% molybdenum ferrite stainless steel, plating one side of the outer wall surface with nickel, and then performing press working.

< comparative example 12>

A positive electrode case is produced by using a stainless steel sheet containing 28.50 to 32.00 mass% of chromium and 1.50 to 2.50 mass% of molybdenum, and performing surface nickel plating on one side of the outer wall surface of the stainless steel sheet, followed by press working. Further, the stainless steel was the same as JIS SUS447J1 product.

< comparative example 13>

The positive electrode case is manufactured by plating nickel on the surface of one side of an outer wall surface of stainless steel prepared by adding 17.00-20.00 mass percent of chromium and 1.75-2.50 mass percent of molybdenum to ferrite stainless steel, and pressing the nickel by pressing. Further, the stainless steel is the same as JIS SUS444 products.

< comparative example 14>

A positive electrode case is produced by using a stainless steel plate produced by adding 16.00 to 18.00 mass percent of chromium, 2.00 to 3.00 mass percent of molybdenum, and 10.00 to 14.00 mass percent of nickel to an austenitic stainless steel, plating one side of an outer wall surface with nickel, and pressing the nickel by press. Further, the stainless steel is the same as JIS SUS316 products.

The chemical compositions of the stainless steel sheets used in the above examples and comparative examples are shown in table 8.

TABLE 8

	Chemical composition (wt%)
	Chemical composition (wt%)												C	Si	Mn	P	S	Ni	Cr	Mo	N	Nb	Ti	Al
	Example 16	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.20	0.20	C	Si	Mn	P	S	Ni	Cr	Mo	N	Nb	Ti	Al	0.10
Example 17	Example 16	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.20	0.20	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.10	0.10	0.05	0.10
Example 17	Example 18	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.30	0.30	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.10	0.10	0.05	0.15
Comparative example 10	Example 18	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.30	0.30	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.05	0.05	0.025	0.15
Comparative example 10	Comparative example 11	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.40	0.40	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.05	0.05	0.025	0.20
Comparative example 12JISSUS447J1	Comparative example 11	0.007	0.20	0.20	-	-	-	30.00	2.00	0.010	0.40	0.40	＜0.010	＜0.40	＜0.40	＜0.030	＜0.020	-	28.50～32.00	1.50～2.50	＜0.015	-	-	-	0.20
Comparative example 12JISSUS447J1	Comparative example 13JIS SUS444	＜0.025	＜1.00	＜1.00	＜0.040	＜0.030	-	17.00～20.00	1.75～2.50	＜0.025	-	-	＜0.010	＜0.40	＜0.40	＜0.030	＜0.020	-	28.50～32.00	1.50～2.50	＜0.015	-	-	-	-
Comparative example 14JIS SUS316	Comparative example 13JIS SUS444	＜0.025	＜1.00	＜1.00	＜0.040	＜0.030	-	17.00～20.00	1.75～2.50	＜0.025	-	-	＜0.080	＜1.00	＜2.00	＜0.045	＜0.030	10.00～14.00	16.00～18.00	2.00～3.00	-	-	-	-	-

After the batteries of examples 16 to 18 and comparative examples 10 to 14 were prepared in 1000 numbers, and initially charged at a constant current and a constant voltage of 4.2V and 3mA for 48 hours, 50 batteries were stored in a Dry environment at 60 ℃ for 20 days while a constant voltage of 4.4V was applied, and then the pitting corrosion of the positive electrode case was checked with a magnifying glass. The number of cells in which pitting corrosion occurred is shown in Table 9.

TABLE 9

	Number of tests (number)	Number of pitting corrosion
	Number of tests (number)	Number of pitting corrosion	Example 16	50	0
Example 17	50	0	Example 16	50	0
Example 17	50	0	Example 18	50	0
Comparative example 10	50	21	Example 18	50	0
Comparative example 10	50	21	Comparative example 11	50	4
Comparative example 12	50	23	Comparative example 11	50	4
Comparative example 12	50	23	Comparative example 13	50	50
Comparative example 14	50	50	Comparative example 13	50	50

As can be seen from table 9: the batteries of examples 16 to 18 did not suffer pitting corrosion. Pitting corrosion started to occur in comparative example 10 in which the amounts of niobium, titanium, and aluminum were small. In addition, pitting corrosion occurred in comparative examples 12 to 14 in which niobium, titanium and aluminum were not added. As described above, in the non-aqueous electrolyte battery having a high voltage exceeding 4V, the pitting potential is lower than the potential of the positive electrode active material in the stainless steel material to which chromium and molybdenum are added, and therefore, the material in the positive electrode member dissolves in the electrolyte solution, causing pitting corrosion. On the other hand, the addition amount of niobium, titanium, and aluminum is small, and pitting corrosion occurs.

Further, in comparative example 11 in which the amounts of niobium, titanium and aluminum were large, pitting corrosion was observed in a small amount of the sample. This is because the addition amount of titanium and aluminum is increased to separate inclusions, precipitates, and the like, and as a result, the pitting corrosion resistance is lowered.

In the present embodiment, the same effect can be obtained by using a power generation element in which the positive electrode and the negative electrode are wound with the separator interposed therebetween, or a power generation element in which the positive electrode and the negative electrode are laminated in a multi-layer manner with the separator interposed therebetween, or a power generation element in which the positive electrode and the negative electrode in a sheet form are folded with the separator interposed therebetween.

< example 19>

In the above example 5, the positive electrode case was used, and the manufacturing method thereof was: a stainless steel sheet is produced by adding 0.85 mass% niobium, 0.1 mass% titanium and 0.25 mass% copper to a ferrite stainless steel containing 20.00 to 23.00 mass% chromium and 1.50 to 2.50 mass% molybdenum, and nickel plating the side of the stainless steel sheet constituting the outer wall surface, followed by press working to produce a positive electrode case.

< example 20>

In the above example 5, the positive electrode case was used, and the manufacturing method thereof was: a stainless steel sheet is produced by adding 0.80 mass% niobium, 0.05 mass% titanium and 0.20 mass% copper to a ferrite stainless steel containing 20.00-23.00 mass% chromium and 1.50-2.50 mass% molybdenum, and nickel plating the side of the stainless steel sheet constituting the outer wall surface, followed by press working to produce a positive electrode case.

< example 21>

The manufacturing method of the positive electrode shell comprises the following steps: a stainless steel sheet is produced by adding 0.90 mass% niobium, 0.15 mass% titanium and 0.30 mass% copper to a ferrite stainless steel containing 20.00 to 23.00 mass% chromium and 1.50 to 2.50 mass% molybdenum, and nickel plating the side of the stainless steel sheet constituting the outer wall surface, followed by press working to produce a positive electrode case.

< comparative example 15>

The manufacturing method of the positive electrode shell comprises the following steps: a stainless steel sheet is produced by adding 0.75 mass% niobium, 0.03 mass% titanium and 0.15 mass% copper to a ferrite stainless steel containing 20.00 to 23.00 mass% chromium and 1.50 to 2.50 mass% molybdenum, and then nickel plating the side of the stainless steel sheet constituting the outer wall surface, followed by press working to produce a positive electrode case.

< comparative example 16>

The manufacturing method of the positive electrode shell comprises the following steps: a stainless steel sheet is produced by adding 0.95 mass% niobium, 0.20 mass% titanium and 0.35 mass% copper to a ferrite stainless steel containing 20.00 to 23.00 mass% chromium and 1.50 to 2.50 mass% molybdenum, and nickel plating the side of the stainless steel sheet constituting the outer wall surface, followed by press working to produce a positive electrode case.

The chemical compositions of the stainless steel sheets used in examples 19 to 21 and comparative examples 13 to 16 are shown in Table 10.

Watch 10

	Chemical composition (wt%)
	Chemical composition (wt%)												C	Si	Mn	P	S	Ni	Cr	Mo	N	Nb	Ti	Cu
	Example 19	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.85	0.10	C	Si	Mn	P	S	Ni	Cr	Mo	N	Nb	Ti	Cu	0.25
Example 20	Example 19	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.85	0.10	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.80	0.05	0.20	0.25
Example 20	Example 21	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.90	0.15	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.80	0.05	0.20	0.30
Comparative example 15	Example 21	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.90	0.15	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.75	0.03	0.15	0.30
Comparative example 15	Comparative example 16	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.95	0.20	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.75	0.03	0.15	0.35
Comparative example 13JISSUS444	Comparative example 16	0.007	0.15	0.10	-	-	0.2	22.00	2.00	-	0.95	0.20	＜0.025	＜1.00	＜1.00	＜0.040	＜0.030	-	17.00～20.00	1.75～2.50	＜0.025	-	-	-	0.35
Comparative example 13JISSUS444	Comparative example 14JISSUS316	＜0.080	＜1.00	＜2.00	＜0.045	＜0.030	10.00～14.00	16.00～18.00	2.00～3.00	-	-	-	＜0.025	＜1.00	＜1.00	＜0.040	＜0.030	-	17.00～20.00	1.75～2.50	＜0.025	-	-	-	-

1000 batteries of examples 19 to 21 and comparative examples 13 to 16 were prepared, and after initial charging for 48 hours under constant current and constant voltage of 4.2V and 3mA, 50 batteries were stored for 6 months under the condition that constant voltage of 4.4V was applied at room temperature, and pitting corrosion of the positive electrode case was confirmed with a magnifying glass. Further, 200 cells were stored in an environment of 45 to 93% relative humidity for 100 days, and leakage was checked with a magnifier. The number of cells in which pitting corrosion and weeping occurred is shown in Table 11.

TABLE 11

	Results of pitting test		Liquid leakage test results
	Results of pitting test		Liquid leakage test results		Number of tests (number)	Number of pitting occurred	Number of tests (number)	Number of leakage
	Example 19	50	0	200	Number of tests (number)	Number of pitting occurred	Number of tests (number)	Number of leakage	0
Example 20	Example 19	50	0	200	50	0	200	0	0
Example 20	Example 21	50	0	200	50	0	200	0	0
Comparative example 15	Example 21	50	0	200	50	3	200	0	0
Comparative example 15	Comparative example 16	50	6	200	50	3	200	0	2
Comparative example 13	Comparative example 16	50	6	200	50	50	200	1	2
Comparative example 13	Comparative example 14	50	50	200	50	50	200	1	0

As can be seen from table 11: the batteries of examples 19 to 21 did not suffer from pitting corrosion. However, the battery of comparative example 15 in which the amounts of niobium, titanium and copper added were small showed pitting corrosion. On the other hand, the battery of comparative example 16 in which the amounts of niobium, titanium and copper added were large exhibited pitting corrosion and liquid leakage. In comparative example 13 in which chromium and molybdenum were added, pitting corrosion also occurred in comparative example 14, and in particular, liquid leakage also occurred in comparative example 13.

It is seen from this that, in a high-voltage nonaqueous electrolyte battery having a voltage of more than 4V, the pitting potential of the stainless steel material to which chromium and molybdenum are added is lower than the potential of the positive electrode active material, and therefore, the substance in the positive electrode member dissolves in the electrolytic solution to cause pitting corrosion, and the pitting potential of the stainless steel material is made higher than the potential of the positive electrode active material by adding niobium, titanium, and copper, whereby the pitting corrosion can be prevented.

However, when the amounts of niobium, titanium and copper added are small, the pitting potential of stainless steel becomes insufficient for the potential of the positive electrode active material, and thus pitting corrosion occurs. Further, when the addition amounts of niobium, titanium and copper are increased, inclusions, precipitates and the like of additives contained in the stainless steel material are easily separated and generated, so that pitting corrosion resistance is lowered, and the formation of ferrite is promoted by the influence of niobium, so that the steel material is hardened and the working is difficult.

The following describes an example in which a metal mesh is provided between the positive and negative electrode cases and the electrode group.

< example 22>

A cross-sectional view of the battery of this example is shown in fig. 6. In the same battery as in example 5 above, a metal mesh 15 made of stainless steel having a thickness of 0.03mm was welded to the inner surfaces of the positive and negative electrode cases. The other manufacturing methods were the same as in example 5. The total of the thickness of the positive electrode case 1 and the negative electrode case 5 and the thickness of the metal mesh 15 was 0.28 mm.

< example 23>

A metal mesh having a thickness of 0.05mm was welded to the inner surfaces of the positive and negative electrode cases, and the total of the thickness of the positive and negative electrode cases and the thickness of the metal mesh was 0.30 mm. Other methods of manufacturing the battery were the same as in example 22.

< example 24>

A metal mesh having a thickness of 0.10mm was welded to the inner surfaces of the positive and negative electrode cases, and the total of the thickness of the positive and negative electrode cases and the thickness of the metal mesh was 0.35mm, respectively. Other methods of manufacturing the battery were the same as in example 22.

< example 25>

A metal mesh having a thickness of 0.15mm was welded to the inner surfaces of the positive and negative electrode cases, and the total of the thickness of the positive and negative electrode cases and the thickness of the metal mesh was 0.40mm, respectively. Other methods of manufacturing the battery were the same as in example 22.

< example 26>

A metal mesh having a thickness of 0.20mm was welded to the inner surfaces of the positive and negative electrode cases, and the total of the thickness of the positive and negative electrode cases and the thickness of the metal mesh was 0.45mm, respectively. Other methods of manufacturing the battery were the same as in example 22.

< example 27>

A metal mesh having a thickness of 0.30mm was welded to the inner surfaces of the positive and negative electrode cases, and the total of the thickness of the positive and negative electrode cases and the thickness of the metal mesh was 0.55mm, respectively. Other methods of manufacturing the battery were the same as in example 22.

< comparative example 17>

Instead of using a metal mesh, a positive electrode case and a negative electrode case were used, each of which had a thickness of 0.25mm and on the inner surface of the battery case a conductive coating material was applied. Other methods of manufacturing the battery were the same as in example 22.

Lead terminals made of stainless steel and having a thickness of 0.2mm were welded to the positive and negative electrode cases of the 300 batteries of the present example and the comparative example, which were fabricated as described above, by resistance welding at a welding output of 480 ± 10V. 50 of these batteries were randomly extracted, and the batteries were dissected to observe the porosity, shrinkage, and peeling of the electrode of the separator on the positive and negative electrode sides. These batteries were initially charged at a constant current and a constant voltage of 4.2V and 3mA for 48 hours, and after standing at room temperature for 3 days, the open circuit voltage was measured. Then, the cell having an open circuit voltage of 4.0V or more after 3 days was discharged at a constant current of 1mA until it reached 3.0V, and the discharge capacity was determined.

The porosity and shrinkage of the separator on the positive and negative electrodes, and the occurrence rate of peeling of the electrode are shown in table 12. Table 13 shows the average value of the discharge capacity of the batteries in which the open circuit voltage after the battery was left for 3 days was 4.0V or less and the open circuit voltage after the battery was left for 3 days was 4.0V or more after the initial charge.

As can be seen from the table: in the batteries of the examples of the present invention, the separator on the positive and negative electrode sides after the lead terminals were welded to the batteries by the resistance welding method was much more improved in porosity, shrinkage, and electrode peeling, and the short circuit of the batteries was also improved, as compared with the battery of comparative example 17. In the example in which the total of the thickness of the positive electrode case and the negative electrode case and the thickness of the metal mesh was 0.30mm or more, the separator on the positive and negative electrode sides after the lead terminals were welded to the battery by resistance welding was less likely to cause porosity (perforation), shrinkage, and electrode peeling, as compared with the battery of comparative example 17. The battery of example 22 exhibited a slight shrinkage of the positive electrode-side separator and the negative electrode-side separator after resistance welding, but did not exhibit a short circuit in the battery. In the batteries of examples 23 to 26, since the thickness of the metal mesh was adjusted, a large number of electrodes could be incorporated in the batteries, and a large capacity battery could be produced. However, in example 27 in which the metal mesh is thick, the capacity is decreased, and therefore, the effect is more preferable when the total of the thickness of the positive and negative electrode cases and the thickness of the metal mesh is 0.30mm to 0.45 mm.

TABLE 12

	Total thickness (mm) of electrode case and metal mesh	Failure rate of spacer and electrode
		Failure rate of spacer and electrode			Porosity of the spacer	Shrinkage of the septum	Exfoliation of electrodes
		Comparative example 17	0.25	50/50	Porosity of the spacer	Shrinkage of the septum	Exfoliation of electrodes	50/50	50/50
Example 22	0.28	Comparative example 17	0.25	50/50	0/50	2/50	0/50	50/50	50/50
Example 22	0.28	Example 23	0.30	0/50	0/50	2/50	0/50	0/50	0/50
Example 24	0.35	Example 23	0.30	0/50	0/50	0/50	0/50	0/50	0/50
Example 24	0.35	Example 25	0.40	0/50	0/50	0/50	0/50	0/50	0/50
Example 26	0.45	Example 25	0.40	0/50	0/50	0/50	0/50	0/50	0/50
Example 26	0.45	Example 27	0.55	0/50	0/50	0/50	0/50	0/50	0/50

Watch 13

	Total thickness (mm) of electrode case and metal mesh	The number of batteries having an open-circuit voltage of 4.0V or less 3 days after charging	Discharge capacity (mAh)
	Total thickness (mm) of electrode case and metal mesh		Discharge capacity (mAh)	Comparative example 17	0.25	50/50	18
Example 22	0.28	0/50	73	Comparative example 17	0.25	50/50	18
Example 22	0.28	0/50	73	Example 23	0.30	0/50	73
Example 24	0.35	0/50	71	Example 23	0.30	0/50	73
Example 24	0.35	0/50	71	Example 25	0.40	0/50	69
Example 26	0.45	0/50	67	Example 25	0.40	0/50	69
Example 26	0.45	0/50	67	Example 27	0.55	0/50	63

The following describes an example in which a non-metallic heat insulating material is provided between the positive and negative electrode cases and the separator.

< example 28>

The cross-sectional views of the battery of this embodiment are shown in fig. 7 and 8. As shown in these figures, after the same electrode group as in example 5 was produced, a portion within 10mm from the end of one surface of the electrode was used as a current carrying portion. Therefore, the negative electrode sheet 4 was obtained by removing the film layer 4b containing the negative electrode active material and then removing the film layer 4b containing the negative electrode active material on the back surface thereof within 22mm from the end. A glass tape having a thickness of 0.03mm was attached as shown in the figure to the part of the negative electrode sheet 4 from which the 22mm layer containing the negative-electrode active material was removed, as a heat insulating material 16. The glass ribbon was made of a glass cloth having a length of 11mm and a width of 16mm as a base material, and an adhesive material was applied to one surface of the glass cloth. Similarly, a heat insulating material 16 is attached to the positive electrode sheet. In the figure, 2 is a positive electrode sheet, 2a is a positive electrode current collector, 2b is a film layer containing a positive electrode active material, and 4a is a negative electrode current collector, and the rest is the same as in example 5.

< example 29>

The other manufacturing methods of the battery are the same as those of the embodiment 28 except that the glass strips with the thickness of 0.05mm are pasted on the positive plate and the negative plate.

< example 30>

The thickness of the film layer containing the active material of the positive electrode and the negative electrode was set to 0.14mm, and a glass tape having a thickness of 0.10mm was attached to the positive electrode sheet and the negative electrode sheet. Other methods of manufacturing the battery were the same as in example 28.

< example 31>

The thickness of the film layer containing the active substance of the positive electrode and the negative electrode was set to 0.13mm, and a glass tape having a thickness of 0.15mm was attached to the positive electrode sheet and the negative electrode sheet. Other methods of manufacturing the battery were the same as in example 28.

< example 32>

The thickness of the film layer containing the active substance of the positive electrode and the negative electrode was set to 0.12mm, and glass tapes having a thickness of 0.20mm were attached to the positive electrode sheet and the negative electrode sheet. Other methods of manufacturing the battery were the same as in example 28.

< example 33>

The thickness of the film layer containing the active substance of the positive electrode and the negative electrode was set to 0.10mm, and glass tapes having a thickness of 0.30mm were attached to the positive electrode sheet and the negative electrode sheet. Other methods of manufacturing the battery were the same as in example 28.

< example 34>

A PTFE tape having a thickness of 0.03mm and having a binder applied to one surface thereof was adhered to the positive electrode sheet and the negative electrode sheet. Other methods of manufacturing the battery were the same as in example 28.

< example 35>

PTFE tapes each having a thickness of 0.05mm were attached to the positive electrode sheet and the negative electrode sheet, and the other methods of producing the batteries were the same as in example 28.

< example 36>

The thickness of the film layer containing the active material of the positive and negative electrodes was set to 0.14mm, and a PTFE tape having a thickness of 0.10mm was attached to the positive and negative electrode sheets. Other methods of manufacturing the battery were the same as in example 28.

< example 37>

The thickness of the film layer containing the active material of the positive and negative electrodes was set to 0.13mm, and a PTFE tape having a thickness of 0.15mm was attached to the positive and negative electrode sheets. Other methods of manufacturing the battery were the same as in example 28.

< example 38>

The thickness of the film layer containing the active material of the positive and negative electrodes was set to 0.12mm, and a PTFE tape having a thickness of 0.20mm was attached to the positive and negative electrode sheets. Other methods of manufacturing the battery were the same as in example 28.

< example 39>

The thickness of the film layer containing the active material of the positive and negative electrodes was set to 0.10mm, and a PTFE tape having a thickness of 0.30mm was attached to the positive and negative electrode sheets. Other methods of manufacturing the battery were the same as in example 28.

< comparative example 18>

The battery was produced in the same manner as in example 28, except that no heat insulating material was attached to the positive electrode sheet and the negative electrode sheet.

In 300 batteries of the present example and the comparative example each manufactured as described above, lead terminals made of stainless steel and having a thickness of 0.2mm were welded to both the positive electrode and the negative electrode case, and the output voltage of the resistance welding machine was set to 480 ± 10V. 50 of these batteries were randomly selected, and the batteries were dissected to observe the porosity, shrinkage, and electrode peeling of the separator on the positive and negative electrodes. Then, 50 more cells were extracted from the remaining cells, and subjected to initial charging at a constant current and constant voltage of 4.2V and 3mA for 48 hours, and after standing at room temperature for 3 days, the open-circuit voltage was measured. Then, only the batteries having an open circuit voltage of 4.0V or more were sorted, and further discharged at a constant current of 1mA until the discharge capacity reached 3.0V, to obtain the discharge capacity.

The occurrence rates of porosity, shrinkage and peeling of the separators of the batteries of the present example and comparative example, the number of batteries having an open circuit voltage of 4.0V or less after leaving for 3 days, and the average value of the discharge capacity thereafter are shown in table 14.

TABLE 14

	Material of heat insulating material	Thickness of thermal insulation material (mm)	Failure rate of spacer and electrode			The number of batteries having an open-circuit voltage of 4.0V or less 3 days after charging	Discharge capacity (mAh)
			Failure rate of spacer and electrode					Porosity of the spacer	Shrinkage of the septum	Exfoliation of electrodes
			Comparative example 18	-	Is free of			Porosity of the spacer	Shrinkage of the septum	Exfoliation of electrodes	50/50	50/50	50/50	50	-
Example 28	Glass ribbon	0.01	Comparative example 18	-	Is free of	0/50	2/50	2/50	3	67	50/50	50/50	50/50	50	-
Example 28		0.01	Example 29	0.05	0/50	0/50	2/50	2/50	3	67	0/50	1/50	0	67
Example 30		0.10	Example 29	0.05	0/50	0/50	0/50	0/50	0	65	0/50	1/50	0	67
Example 30		0.10	Example 31	0.15	0/50	0/50	0/50	0/50	0	65	0/50	0/50	0	63
Example 32		0.20	Example 31	0.15	0/50	0/50	0/50	0/50	0	61	0/50	0/50	0	63
Example 32		0.20	Example 33	0.30	0/50	0/50	0/50	0/50	0	61	0/50	0/50	0	57
Example 34		PTFE	Example 33	0.30	0/50	0.01	0/50	2/50	4/50	3	0/50	0/50	0	57	67
Example 34	Example 35		0.05	0/50	0/50	0.01	0/50	2/50	4/50	3	1/50	0	67		67
Example 36	Example 35		0.05	0/50	0/50	0.10	0/50	0/50	0/50	0	1/50	0	67	65
Example 36	Example 37		0.15	0/50	0/50	0.10	0/50	0/50	0/50	0	0/50	0	63	65
Example 38	Example 37		0.15	0/50	0/50	0.20	0/50	0/50	0/50	0	0/50	0	63	61
Example 38	Example 39		0.30	0/50	0/50	0.20	0/50	0/50	0/50	0	0/50	0	57	61

As can be seen from table 14: the battery of each example of the present invention was significantly improved in porosity, shrinkage, and electrode peeling of the separator on the positive and negative electrode sides after the lead terminals were resistance-welded to the battery, as compared to comparative example 18, and the occurrence of a battery in which the internal short circuit was suppressed and the open circuit voltage was reduced. The batteries of examples 29 to 33 and examples 35 to 39, in which the thickness of the glass tape as a heat insulator or the PTFE tape as a fluororesin was 0.05mm or more, were almost free from the occurrence of porosity, shrinkage, electrode peeling, and open circuit voltage lowering of the separator on the positive and negative electrodes after the lead terminals were resistance-welded to the battery. Further, the batteries of examples 29 to 32 and examples 35 to 38 were able to be made into large-capacity batteries by incorporating a large amount of functional substances into the batteries because the heat insulating material had an appropriate thickness.

In the examples of the present invention, the case where glass or PTFE is used as the base material of the non-metallic heat insulating material is described. However, the same effect can be obtained even when FEP, ETFE, PFA, PVDF, polyimide, LCP, PPS, or PBT is used as the base material. Further, although the flat nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte is a nonaqueous solvent has been described in the embodiment of the present invention, the present invention is also applicable to a polymer secondary battery in which the nonaqueous electrolyte is a polymer electrolyte and a solid electrolyte secondary battery in which the nonaqueous electrolyte is a solid electrolyte, and is also effective for a battery in which a polymer thin film and a solid electrolyte film damaged by heat at the time of welding are used instead of a resin separator. The shape of the battery is described based on a coin-shaped nonaqueous electrolyte sealed by a positive electrode can crimping method. However, the positive and negative electrodes can be changed, and the sealing can be performed by using the method of crimping the negative casing. The shape of the battery does not need to be a positive circle, and the present invention can be applied to a flat nonaqueous electrolyte secondary battery having a special shape such as an oval shape or a rectangular shape.

The following describes an embodiment of the present invention in which a notch is provided in a positive electrode case.

(example 40)

The cross-sectional view of the battery of this embodiment is shown in fig. 9, and the oblique view of the positive electrode case thereof is shown in fig. 10.

A flat nonaqueous electrolyte secondary battery was produced in the same manner as in example 5. However, the positive casing 1 has a height of 3mm and a diameter of 24.5mm, and as shown in fig. 9 and 10, the positive casing is provided with a notch 1a, and the notch 1a has a dimension of 0.1 pi rad in width and 0.15mm in depth with respect to the center of the circumference of the positive casing. The positive electrode case is then crimped in the radial and height directions to seal the opening.

< example 41>

The notch 1a formed in the positive electrode case 1 has a radius angle of 0.1 π rad and a depth of 0.90 mm. The other manufacturing method of the battery was the same as in example 40.

< example 42>

The notch 1a formed in the positive electrode case 1 has a radius angle of 0.9 π rad and a depth of 0.15 mm. The other manufacturing method of the battery was the same as in example 40.

< example 43>

The notch 1a made on the positive electrode case 1 has a radius angle of 0.9 pi rad and a depth of 0.9 mm. The other manufacturing method of the battery was the same as in example 40.

< comparative example 19>

The battery was fabricated in the same manner as in example 40, except that no notch was formed in the positive electrode case 1.

< comparative example 20>

The notch 1a formed in the positive electrode case 1 has a radius angle of 0.1 π rad and a depth of 0.10 mm. The other manufacturing method of the battery was the same as in example 40.

< comparative example 21>

The notch 1a formed in the positive electrode case 1 has a radius angle of 0.1 π rad and a depth of 0.95 mm. The other manufacturing method of the battery was the same as in example 40.

< comparative example 22>

The notch 1a formed in the positive electrode case 1 has a radius angle of 0.05 π rad and a depth of 0.90 mm. The other manufacturing method of the battery was the same as in example 40.

< comparative example 23>

The notch 1a formed in the positive electrode case 1 has a radius angle of 0.95 π rad and a depth of 0.15 mm. The other manufacturing method of the battery was the same as in example 40.

< comparative example 24>

The notch 1a formed in the positive electrode case has a radius angle of 0.1 π rad and a depth of 0.15mm, and the positive electrode case 1 is crimped only in the radial direction and sealed. Other methods of manufacturing the battery were the same as in example 40.

50 of these batteries were prepared, and were initially charged for 48 hours under constant current and constant voltage of 4.2V and 3mA, and then stored at 45 ℃ under a relative humidity of 93% for 100 days, and the number of electrolyte leakage was examined. Further, a constant current forced discharge test of 300mA for 6 hours and a heating test of 5 ℃/min for 10 min at 160 ℃ were carried out to examine the occurrence of cracking.

The test results are shown in Table 15. The batteries of the present example and comparative examples 19, 20 and 22 did not leak by storage. In contrast, in comparative example 21, the notch was too deep, and the electrolyte leaked from the notch. In comparative example 23, the notch width was too large, and in comparative example 24, the compressibility of the insulating gasket was not increased, and the airtightness was poor, so that the electrolyte leaked.

In the forced discharge test and the heating test, the batteries of the present example and comparative examples 21, 23, and 24 did not crack. However, the positive electrode cases of the batteries of comparative examples 19, 20 and 22 were not deformed, and the insulating gasket was not opened, so that cracks occurred.

Watch 15

	Size of gap		Number of occurrence of leakage	Number of occurrence of crack
	Size of gap			Number of occurrence of crack		Width (rad)	Depth (mm)	At the time of forced discharge test	At the time of heating test
	Example 40	0.1π		0.15	0/30	Width (rad)	Depth (mm)	At the time of forced discharge test	At the time of heating test	0/10	0/10
EXAMPLE 41	Example 40	0.1π	0.1π	0.15	0/30	0.90	0/30	0/10	0/10	0/10	0/10
EXAMPLE 41	Example 42	0.9π	0.1π	0.15	0/30	0.90	0/30	0/10	0/10	0/10	0/10
Example 43	Example 42	0.9π	0.9π	0.15	0/30	0.90	0/30	0/10	0/10	0/10	0/10
Example 43	Comparative example 19	Without gaps		0/30	0/10	0.90	0/30	0/10	0/10	0/10
Comparative example 20	Comparative example 19	Without gaps		0/30	0/10	0.1π	0.10	0/30	0/10	0/10	0/10
Comparative example 20	Comparative example 21	0.1π	0.95	24/30	0/10	0.1π	0.10	0/30	0/10	0/10	0/10
Comparative example 22	Comparative example 21	0.1π	0.95	24/30	0/10	0.05π	0.90	0/30	0/10	0/10	0/10
Comparative example 22	Comparative example 23	0.95π	0.15	19/30	0/10	0.05π	0.90	0/30	0/10	0/10	0/10
Comparative example 24	Comparative example 23	0.95π	0.15	19/30	0/10	0.1π	0.15	29/30	0/10	0/10	0/10

As described above, since the notch of the positive electrode case has a width of 0.1 to 0.9 pi rad with respect to the center angle of the circumference of the positive electrode case and a depth of 5 to 30% of the height of the positive electrode case, a flat nonaqueous electrolyte secondary battery which is free from breakage at the time of abnormality and from leakage during storage can be obtained.

Further, although the embodiment of the present invention has been described using the flat nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte is the nonaqueous solvent, the same effect can be obtained also in the polymer secondary battery in which the nonaqueous electrolyte is a polymer electrolyte or the solid electrolyte secondary battery in which the solid electrolyte is used. In addition, a polymer film or a solid electrolyte membrane may be used instead of the resin separator. The case where the notch is single is explained. However, even when a plurality of notches are provided, the same effect can be obtained if the total width of the notches is 0.1 to 0.9 π rad with respect to the center angle of the positive electrode case circumference. In addition, the battery shape was described with respect to a coin-shaped nonaqueous electrolyte secondary battery in which sealing was performed by crimping of the positive electrode case, but the positive and negative electrodes may be replaced with each other, and the negative electrode case may be provided with a notch and sealed by crimping.

An example of a flat nonaqueous electrolyte secondary battery in which one or 2 grooves are formed in the longitudinal axis direction of the seal R portion of the positive electrode case to form a thin plate portion will be described below.

< example 44>

This embodiment is explained with reference to fig. 11, 12, and 13, and fig. 11 is a cross-sectional view of the battery of this embodiment; fig. 12 is an external view of the positive electrode can seal R portion of fig. 11; fig. 13 is a sectional view of the positive electrode case 1 formed in a circular sheet shape.

In the positive electrode case 1, a groove thin plate portion 1b is provided at the seal R portion. The length h of the groove thin plate part 1b is approximately half of the height of the positive electrode shell, and the thickness S of the groove thin plate part 1b is 7, from 0.05mm to 0.17mm, with the difference of 0.02 mm. After initial charging for 48 hours under constant current and constant voltage of 4.2V and 3mA, 10 of these batteries were subjected to a constant current forced discharge test of 300mAh and 6 hours and a heating test of holding the batteries at a temperature rise rate of 5 ℃/min and 160 ℃ for 10 minutes, and the rupture of the batteries was examined. And 30 cells each were stored at 45 ℃ with a relative humidity of 93% for 100 days, and the presence of electrolyte leakage was investigated.

< example 45>

The same secondary battery as in example 44 was used, and the groove thin plate portion of the positive electrode container was formed at 2 places, and the experimental evaluation was performed in the same manner. The test results are shown in Table 16. When the thickness of the thin plate part of the groove was 0.17mm, the thin plate part was not broken in both 1 and 2 grooves, and the battery content was broken to scatter. Moreover, when the thickness of the sheet is 0.05mm, leakage occurs in 1 or 2 grooves because the thickness of the sheet is too small, and cracks are generated during sealing, thereby deteriorating the sealing performance.

TABLE 16

Groove sheet thickness (mm)	Positive electrode container
	Positive electrode container						Example 441 grooved lamella portions			Example 452 grooved sheet sections
	Discharge of electricity	Heating of	Leakage of liquid	Discharge of electricity	Heating of	Leakage of liquid	Example 441 grooved lamella portions			Example 452 grooved sheet sections
	Discharge of electricity	Heating of	Leakage of liquid	Discharge of electricity	Heating of	Leakage of liquid	0.05	0/10	0/10	3/30	0/10	0/10	5/30
0.07	0/10	0/10	0/30	0/10	0/10	0/30	0.05	0/10	0/10	3/30	0/10	0/10	5/30
0.07	0/10	0/10	0/30	0/10	0/10	0/30	0.09	0/10	0/10	0/30	0/10	0/10	0/30
0.11	0/10	0/10	0/30	0/10	0/10	0/30	0.09	0/10	0/10	0/30	0/10	0/10	0/30
0.11	0/10	0/10	0/30	0/10	0/10	0/30	0.13	0/10	0/10	0/30	0/10	0/10	0/30
0.15	0/10	0/10	0/30	0/10	0/10	0/30	0.13	0/10	0/10	0/30	0/10	0/10	0/30
0.15	0/10	0/10	0/30	0/10	0/10	0/30	0.17	3/10	1/10	0/30	2/10	2/10	0/30

From the results, it can be seen that: the thickness of the thin plate part is controlled within the range of 0.07mm to 0.15mm, so that the flat nonaqueous electrolyte secondary battery can be prevented from cracking and can be stored without liquid leakage.

In example 44 and example 45 of the present invention, a flat nonaqueous solvent secondary battery using a nonaqueous solvent as a nonaqueous electrolyte was described. However, the same effects can be obtained for a polymer secondary battery in which the nonaqueous electrolyte is a polymer electrolyte and a fixed electrolyte secondary battery using a solid electrolyte.

The following examples of the present invention in which the fracture groove having a sectional concave shape is formed on the surface of the negative electrode case are described.

< example 46>

In example 5, as shown in fig. 14 and 15, the negative electrode case 5 was provided with the crush grooves 5e having a concave cross section. The crushing groove 5e is shaped such that 2 crushing grooves are connected to both ends of one crushing groove, respectively. Fig. 14 is a sectional view of the battery of this embodiment, and fig. 15 is a top view of the negative electrode can of fig. 14.

< example 47>

In this embodiment, the shape of the crushing groove is different from that in embodiment 46, and as shown in fig. 16 (upper view of the negative electrode case), the crushing groove 5f having a concave cross section is semicircular along the bottom circumference of the negative electrode case 5.

< example 48>

As shown in fig. 17 (the upper view of the negative electrode case), the crushing grooves 5g having a concave cross section are 1/4 circles along the bottom circumference of the negative electrode case 5, and 2 crushing grooves 5g face each other.

< example 49>

As shown in fig. 18 (the upper view of the negative electrode case), the crushing groove 5h having a concave cross section is a semicircular crushing groove along the bottom circumference of the negative electrode case 5, and the other crushing groove together form a T-shape.

< example 50>

The crushing grooves 5i having a concave cross section are a straight line as shown in fig. 19 (top view of the negative electrode case).

< example 51>

As shown in fig. 20 (the top view of the negative electrode case), the crushing groove 5j having a concave cross section is formed in a state: the 3 linear crushing grooves are collected to the center of the negative electrode can 5.

< example 52>

As shown in fig. 21 (the top view of the negative electrode case), the crushing groove 5k having a concave cross section is formed in a state: the 5 linear crushing grooves are collected to the center of the negative electrode can 5.

< comparative example 25>

As shown in fig. 22 (top view of the negative electrode case), the negative electrode case 5 without the crushed groove is used.

< comparative example 26>

A crushing groove having the same shape as that of the crushing groove shown in example 46 was formed in the positive electrode case. The other methods were the same as in comparative example 25.

< reference example 5>

The crushing groove having the same shape as in example 46 was formed not on the outer surface of the negative electrode case but on the inner surface of the negative electrode case.

50 batteries were initially charged at a constant current and a constant voltage of 4.2V and 3mA for 48 hours, and then stored at a relative temperature of 93% at 60 ℃ for 100 days to examine the occurrence rate of electrolyte leakage. Then, a constant current forced discharge test of 300mA for 6 hours and a heating test of 5 ℃ per minute at a temperature increase rate and 160 ℃ for 10 minutes were carried out to examine the number of occurrence of cell rupture. The test results are shown in Table 17.

TABLE 17

	Number of occurrence of leakage	Constant current forced discharge			Heating test
		Constant current forced discharge			Heating test			Number of cracks	Number of crushing actions	Breaking groove action time (hours)	Number of cracks	Number of crushing actions	Action time of crushing groove (minute)
		Example 46	0/30	0/10	10/10	5～5.5	0/10	Number of cracks	Number of crushing actions	Breaking groove action time (hours)	Number of cracks	Number of crushing actions	Action time of crushing groove (minute)	10/10	25～32
Example 47	0/30	Example 46	0/30	0/10	10/10	5～5.5	0/10	0/10	10/10	5～5.5	0/10	10/10	26～33	10/10	25～32
Example 47	0/30	Example 48	0/30	0/10	10/10	5.2～5.7	0/10	0/10	10/10	5～5.5	0/10	10/10	26～33	10/10	31～36
Example 49	0/30	Example 48	0/30	0/10	10/10	5.2～5.7	0/10	0/10	10/10	4.8～5.3	0/10	10/10	21～24	10/10	31～36
Example 49	0/30	Example 50	0/30	0/10	10/10	5.2～5.6	0/10	0/10	10/10	4.8～5.3	0/10	10/10	21～24	10/10	26～33
Example 51	0/30	Example 50	0/30	0/10	10/10	5.2～5.6	0/10	0/10	10/10	5.2～5.5	0/10	10/10	30～36	10/10	26～33
Example 51	0/30	Example 52	0/30	0/10	10/10	5.0～5.4	0/10	0/10	10/10	5.2～5.5	0/10	10/10	30～36	10/10	29～34
Comparative example 25	0/30	Example 52	0/30	0/10	10/10	5.0～5.4	0/10	10/10	10/10	-	10/10	-	-	10/10	29～34
Comparative example 25	0/30	Comparative example 26	21/30	0/10	10/10	5～5.5	0/10	10/10	10/10	-	10/10	-	-	10/10	25～32
Reference example 5	0/30	Comparative example 26	21/30	0/10	10/10	5～5.5	0/10	0/10	10/10	5.3～5.9	1/10	9/10	31～37	10/10	25～32

As can be seen from table 17: the batteries of example and comparative example 25 and reference example 5 did not leak during storage. In contrast, in comparative example 26, corrosion occurred in the positive electrode case due to storage, and the electrolyte leaked from a part of the fractured groove. Also, in reference example 5, one-tenth of the cracks occurred in the above heating test. This is believed to be because the crushing action of the grooves within the cell is not in time.

As shown in table 17, since at least 1 or more crushed grooves having a concave cross section were formed in the negative electrode case, a flat nonaqueous electrolyte secondary battery which was free from breakage at the time of abnormality and from leakage during storage was obtained.

Further, the embodiments of the present invention have been described using a flat nonaqueous electrolyte secondary battery in which a nonaqueous electrolyte is a nonaqueous solution. However, the same effects can be obtained also in a polymer secondary battery using a polymer electrolyte as a nonaqueous electrolyte and a solid electrolyte secondary battery using a solid electrolyte. In addition, a polymer film or a solid electrolyte membrane may be used instead of the resin separator.

The following shows an example in which the inside of the positive and negative electrode cases is provided with projections and depressions.

< example 53>

Fig. 23 and 24 are sectional views showing a battery of the present embodiment.

In the battery of example 5, a protrusion 5a having a diameter of 1.0mm and a height of 0.2mm was provided on the inner surface of the negative electrode can 5 from the outer surface of the container at the central portion thereof. Thus, 50 flat nonaqueous electrolyte secondary batteries of example 53, each having a thickness of 3mm and a diameter of Φ 24.5mm, were produced.

< example 54>

The negative electrode case was not provided with a projection, and a projection 5a having a diameter of 1.0mm and a height of 0.2mm was provided on the inner surface of the positive electrode case from the outer surface of the container at the center portion thereof. In addition, 50 cells were produced in the same manner as in example 53.

< example 55>

A protrusion 5a having a height of 0.2mm and a diameter of 1.0mm is provided at the center of the positive electrode case and the negative electrode case from the outer surface of the container to the inner surface thereof. In addition, 50 batteries having the structure shown in fig. 23 were produced in the same manner as in example 53.

< comparative example 27>

50 batteries having the structure shown in FIG. 23 were produced in the same manner as in example 53, except that the negative electrode case having no projection was used.

These batteries were initially charged at a constant current of 4.2V and 3mA for 48 hours, and then discharged at a constant current of 30mA until reaching 3.0V, to obtain an initial discharge capacity. Then, heavy-load discharge was performed at 3.0V under a constant current of 240mA, and the discharge capacity was determined. The utilization of the heavy load capacity relative to the initial capacity is shown in table 18.

Watch 18

	Negative electrode case bulge	Positive electrode shell bulge	Heavy load characteristic capacity utilization (%)
	Negative electrode case bulge	Positive electrode shell bulge	Heavy load characteristic capacity utilization (%)	Example 53	Is provided with	Is free of	65
Example 54	Is free of	Is provided with	65	Example 53	Is provided with	Is free of	65
Example 54	Is free of	Is provided with	65	Example 55	Is provided with	Is provided with	70
Comparative example 27	Is free of	Is free of	52	Example 55	Is provided with	Is provided with	70

As can be seen from table 18: the discharge capacity was reduced in the battery of the comparative example as compared with the battery of the present embodiment. At this time, the electrode shrinks during discharge, which causes unstable contact between the electrode group and the battery container, and increases internal resistance. As in the present embodiment, since the contact can be ensured by providing the projection, such a capacity reduction does not occur.

The following description is an example of the present invention in which an electrode group is used in which sheet-like positive and negative electrodes are alternately folded with a separator interposed therebetween.

< example 56>

Fig. 25 and 26 are a sectional view and an upper view of the electrode group of the present embodiment. As shown in the drawing, a sheet-like separator 3 slightly larger than the sheet-like positive electrode is attached to the sheet-like positive electrode 2, but a portion (separator) connected to the inner surface of the positive electrode case 1 is removed. The sheet-like negative electrodes 4 are arranged so as to intersect the sheet-like positive electrodes 2 (perpendicularly in the present embodiment), and then are alternately folded until a desired capacity is obtained, constituting an electrode group. The electrode group is arranged in the positive electrode case 1 with the gasket 6 interposed therebetween, the negative electrode case 5 is placed on the electrode group, and the positive electrode case and the negative electrode case are tooth-sealed (riveted, crimped). Further, the portions of the sheet-like positive and negative electrodes connected to the positive and negative electrode cases are mainly portions having a current collecting function, and therefore, as shown in the drawing, the thickness is substantially one-half as compared with other portions.

According to this embodiment, the electrode group housed in the gasket can be effectively used as compared with the laminated type of fig. 1 and the wound type of fig. 2, and therefore, it can be seen that the capacitance is increased by about 5%.

Claims

1. A flat nonaqueous electrolyte secondary battery having a structure in which a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted to each other through an insulating gasket, and the positive electrode case or the negative electrode case is caulked by caulking, and has a nonaqueous electrolyte and a power generating element including at least a positive electrode, a separator, and a negative electrode inside, characterized in that: the electrode unit in which the positive electrode and the negative electrode are opposed to each other via the separator has a plurality of electrode groups stacked together, and the total of the areas of the electrode groups opposed to the positive electrode and the negative electrode is larger than the opening area of the insulating gasket.

2. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the electrode units are laminated at least 3 times to form an electrode group.

3. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and the active material layer applied to the positive and negative electrode current collectors has a thickness of 0.03mm to 0.40mm on one surface.

4. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet with a negative electrode acting material layer formed on one side or two sides of a negative electrode current collector, one end of each of the positive electrode sheet and the negative electrode sheet exposes each current collector to form a current-carrying part, and the positive electrode current-carrying parts are exposed from the same side surface of the positive electrode current-carrying parts and are electrically connected with the positive electrode shell; the negative electrode conducting parts are exposed from the other side surface of the negative electrode conducting parts through the spacer and electrically connected with the negative electrode casing.

5. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: a non-aqueous electrolyte is used in which₀₀₂A graphite structure having an interplanar spacing of 0.338nm or less, as a negative electrode, and ethylene carbonate and gamma-butyrolactone as main solvents, in which lithium fluoroborate as a supporting salt is dissolved.

6. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the volume ratio of the ethylene carbonate to the gamma-butyrolactone is 0.3-1.0.

7. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the concentration of the supporting salt in the nonaqueous electrolyte is 1.3 to 1.8 mol/l.

8. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: a stainless steel is used which is also used as a constituent material of a positive electrode case of a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are further added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

9. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: a stainless steel which is used as a constituent material of a positive electrode case of a positive electrode terminal or a metal component directly connected to a positive electrode active material is obtained by adding 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper to a ferrite stainless steel containing 20.50 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

10. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: a metal mesh is disposed between the positive electrode case and/or the negative electrode case and the electrode group.

11. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: a non-metallic heat insulating material is provided between the positive electrode case and/or the negative electrode case and the separator.

12. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the sealing is carried out by utilizing the riveting processing method, namely, the insulating washer is compressed in the radial direction and the height direction by the anode shell, a notch is arranged on the side part of the anode shell, the width of the notch is 0.1 pi-0.9 pi rad relative to the center angle of the circumference of the anode shell, and the depth of the notch is 5-30% of the height of the anode shell.

13. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the sealing is performed by a caulking process in which the insulating gasket is compressed in the radial direction and the height direction by the positive electrode case, and 1 or 2 grooves are formed in the longitudinal axis direction of the sealing portion of the positive electrode case to form a thin plate portion.

14. The flat-shaped nonaqueous electrolyte secondary battery according to claim 13, characterized in that: the thickness of the thin plate part formed by the groove processing is 0.07mm to 0.15 mm.

15. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: at least one breaking groove with concave section is arranged in the negative electrode shell.

16. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: a crushing groove having a concave cross section is formed on the outer surface of the negative electrode case.

17. The flat-shaped nonaqueous electrolyte secondary battery according to claim 1, characterized in that: the inside of the positive electrode case and/or the negative electrode case is provided with convexes and concaves or protrusions.

18. A flat nonaqueous electrolyte secondary battery having a structure in which a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted to each other through an insulating gasket, and the positive electrode case or the negative electrode case is caulked by caulking, and has a nonaqueous electrolyte and a power generating element including at least a positive electrode, a separator, and a negative electrode inside, characterized in that: the strip-shaped electrode units, in which the positive electrode and the negative electrode are arranged to face each other with the separator interposed therebetween, are wound to form an electrode group, and the total of the areas of the electrode group facing the positive electrode and the negative electrode is larger than the opening area of the insulating gasket.

19. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: an electrode group formed by winding the belt-shaped electrode unit is pressurized so that the positive and negative electrode facing surfaces are parallel to the flat surface of the flat battery, and no gap is present in the winding core portion.

20. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the band-shaped positive electrode and negative electrode are wound from a position separated from each other via the separator, and the positive electrode and negative electrode are folded and wound so that the opposite surfaces of the positive electrode and the negative electrode are parallel to the flat surface of the flat battery, thereby forming a battery pack.

21. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and the thickness of the active material film layer coated on the positive and negative electrode current collectors is 0.03mm to 0.40mm on one surface.

22. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and each active material film layer is formed only on one surface of each end portion of the negative electrode sheet.

23. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: a non-aqueous electrolyte using a carbonaceous material developed with a graphite structure in which the d002 interplanar spacing is 0.338nm or less as a negative electrode; ethylene carbonate and gamma-butyrolactone are used as main solvents, and lithium fluoroborate is dissolved in the main solvents to be used as a supporting salt.

24. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the volume ratio of the ethylene carbonate to the gamma-butyrolactone is 0.3-1.0.

25. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the concentration of the supporting salt in the nonaqueous electrolyte is 1.3 to 1.8 mol/l.

26. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that:

27. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that:

28. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: a metal mesh is disposed between the positive electrode case and/or the negative electrode case and the electrode group.

29. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: a non-metallic heat insulating material is provided between the positive electrode case and/or the negative electrode case and the separator.

30. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: and sealing by using a riveting processing method, namely compressing the insulating washer in the radial direction and the height direction by the anode shell, arranging a notch on the side part of the anode shell, wherein the width of the notch is 0.1-0.9 pi rad relative to the center angle of the periphery of the anode shell, and the depth of the notch is 5-30% of the height of the anode shell.

31. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the sealing is performed by caulking, that is, the insulating gasket is compressed in the radial direction and the height direction by the positive electrode case, and 1 or 2 grooves are processed in the longitudinal axis direction of the sealing portion of the positive electrode case to form a thin plate portion.

32. The flat-shaped nonaqueous electrolyte secondary battery according to claim 31, characterized in that: the thickness of the thin plate part formed by the groove processing is 0.07mm to 0.15 mm.

33. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: at least one breaking groove with concave section is arranged in the negative electrode shell.

34. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: a crushing groove having a concave cross section is formed on the outer surface of the negative electrode case.

35. The flat-shaped nonaqueous electrolyte secondary battery according to claim 18, characterized in that: the inside of the positive electrode case and/or the negative electrode case is provided with convexes and concaves or protrusions.

36. A flat nonaqueous electrolyte secondary battery having a structure in which a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal are fitted to each other through an insulating gasket, and the battery has a sealing structure in which the positive electrode case or the negative electrode case is caulked by caulking and has at least a power generating element including a positive electrode, a separator, and a negative electrode and a nonaqueous electrolyte in its interior, characterized in that: the sheet-like positive electrode is wrapped with a separator except for a portion in contact with the inner surface of the positive electrode case, the sheet-like negative electrode is arranged so as to be orthogonal to the sheet-like positive electrode wrapped with the separator, and the positive electrode sheet and the negative electrode sheet are alternately folded to form an electrode group, and the total of the areas of the electrode group facing the positive electrode and the negative electrode is larger than the opening area of the insulating gasket.

37. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the sheet-like positive and negative electrodes are arranged with a separator interposed therebetween so that the positive and negative electrodes intersect each other, and the lower electrode is folded onto the upper electrode via the separator, and the other electrode is folded and superposed on the upper electrode, and thereafter, the process is repeated to form an electrode group.

38. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and each active material film layer is formed only on one surface of each end portion of the negative electrode sheet.

39. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet with a negative electrode active material layer formed on one side or two sides of a negative electrode current collector, one end of each of the positive electrode sheet and the negative electrode sheet exposes each current collector to form a current-carrying part, and the positive electrode current-carrying parts are exposed from the same side surface of the positive electrode current-carrying parts and are electrically connected with the positive electrode shell; the negative electrode conducting parts are exposed from the other side surface of the negative electrode conducting parts through the spacer and electrically connected with the negative electrode casing.

40. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: a non-aqueous electrolyte is used in which₀₀₂A graphite structure having an interplanar spacing of 0.338nm or less, as a negative electrode, and ethylene carbonate and gamma butyrolactone as main solvents, in which lithium fluoroborate as a supporting salt is dissolved.

41. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the volume ratio of the ethylene carbonate to the gamma-butyrolactone is 0.3-1.0.

42. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the concentration of the supporting salt in the nonaqueous electrolyte is 1.3 to 1.8 mol/l.

43. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: a stainless steel is used which is also used as a positive electrode case of a positive electrode terminal or a constituent material of a metal component directly contacting a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are further added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

44. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: a stainless steel which is used as a constituent material of a positive electrode case of a positive electrode terminal or a metal component directly connected to a positive electrode active material is obtained by adding 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper to a ferrite stainless steel containing 20.00 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

45. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: a metal mesh is disposed between the positive electrode case and/or the negative electrode case and the electrode group.

46. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: a non-metallic heat insulating material is provided between the positive electrode case and/or the negative electrode case and the electrode group.

47. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: and sealing by using a riveting processing method, namely compressing the insulating washer in the radial direction and the height direction by the anode shell, arranging a notch on the side part of the anode shell, wherein the width of the notch is 0.1-0.9 pi rad relative to the center angle of the periphery of the anode shell, and the depth of the notch is 5-30% of the height of the anode shell.

48. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the sealing is performed by caulking, that is, the insulating gasket is compressed in the radial direction and the height direction by the positive electrode case, and 1 or 2 grooves are processed in the longitudinal axis direction of the sealing portion of the positive electrode case to form a thin plate portion.

49. The flat-shaped nonaqueous electrolyte secondary battery according to claim 48, wherein: the thickness of the thin plate part formed by the groove processing is 0.07mm to 0.15 mm.

50. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: at least one breaking groove with concave section is arranged in the negative electrode shell.

51. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: a crushing groove having a concave cross section is formed on the outer surface of the negative electrode case.

52. The flat-shaped nonaqueous electrolyte secondary battery according to claim 36, wherein: the inside of the positive electrode case and/or the negative electrode case is provided with convexes and concaves or protrusions.

53. A flat nonaqueous electrolyte secondary battery having a metal battery case serving also as an electrode terminal, a sealing plate for sealing the battery case, and another electrode terminal disposed on an opening portion of a part of the sealing plate via an insulator, the battery case having at least a power generating element including a positive electrode, a separator, and a negative electrode, and a nonaqueous electrolyte, characterized in that: the sealing plate is provided with an electrode group formed of electrode units, wherein the positive electrode and the negative electrode are arranged in an opposite manner through a spacer, and the sum of the opposite areas of the positive electrode and the negative electrode of the electrode group is larger than the opening area of the sealing plate.

54. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: the electrode units are overlapped in multiple layers to form an electrode group, wherein the positive electrode is electrically connected with the positive electrode, and the negative electrode is electrically connected with the negative electrode.

55. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a battery pack in which strip-shaped positive and negative electrodes are wound with separators interposed therebetween is mounted in a battery.

56. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a collector plate electrically integrated with the other terminal is disposed, and the collector plate is electrically connected to the positive electrode or the negative electrode.

57. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet having a negative electrode active material layer formed on one or both surfaces of a negative electrode current collector, and the thickness of the active material film layer applied to the positive and negative electrode current collectors is 0.03mm to 0.40mm on one surface.

58. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: the positive electrode is composed of a positive plate with a positive electrode acting material layer formed on one side or two sides of a positive electrode current collector; the negative electrode is composed of a negative electrode sheet with a negative electrode active material layer formed on one side or two sides of a negative electrode current collector, one end of each of the positive electrode sheet and the negative electrode sheet exposes each current collector to form a current-carrying part, and the positive electrode current-carrying parts are exposed from the same side surface of the positive electrode current-carrying parts and are electrically connected with the positive electrode shell; the negative electrode current-carrying parts are exposed from the other side surface of the negative electrode current-carrying parts through the spacer and are electrically connected with the sealing plate.

59. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a nonaqueous electrolyte is used which is produced by using a carbonaceous material having a graphite structure in which the d002 interplanar spacing is 0.338nm or less as a negative electrode, ethylene carbonate and gamma-butyrolactone as main solvents, and lithium fluoroborate as a supporting salt dissolved therein.

60. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: the volume ratio of the ethylene carbonate to the gamma-butyrolactone is 0.3-1.0.

61. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: the concentration of the supporting salt in the nonaqueous electrolyte is 1.3 to 1.8 mol/l.

62. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a stainless steel is used which is a constituent material of a battery case serving as a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.1 to 0.3% of niobium, 0.1 to 0.3% of titanium, and 0.05 to 0.15% of aluminum are further added to a ferrite stainless steel containing 28.50 to 32.00% of chromium and 1.50 to 2.50% of molybdenum.

63. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a stainless steel is used which is also used as a constituent material of a battery case of a positive electrode terminal or a metal component directly connected to a positive electrode active material, wherein 0.8 to 0.9% of niobium, 0.05 to 0.15% of titanium, and 0.20 to 0.30% of copper are further added to a ferrite stainless steel containing 20.00 to 23.00% of chromium and 1.50 to 2.50% of molybdenum.

64. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a metal mesh is provided between the battery case and/or the sealing plate and the electrode group.

65. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a non-metallic heat insulating material is provided between the battery case and/or the sealing plate and the separator.

66. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: at least 1 breaking groove with concave section is arranged on the sealing plate.

67. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: a crushing groove with a concave section is formed on the outer surface of the sealing plate.

68. The flat-shaped nonaqueous electrolyte secondary battery according to claim 53, wherein: the battery case and/or the sealing plate are provided with projections and depressions on the inner side thereof.