JP2000277162A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

[PROBLEMS] To provide a light, safe and inexpensive non-aqueous electrolyte battery. In a non-aqueous electrolyte secondary battery in which a power generating element is housed in a bag-shaped unit cell case, a welded portion of the bag-shaped unit cell case parallel to the winding center axis of the power generating element, Overlap the positions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery in which a power generating element is housed in a bag-shaped unit cell case.

[0002]

2. Description of the Related Art In recent years, electronic devices such as a portable radio telephone, a portable personal computer, and a portable video camera have been developed, and various electronic devices have been reduced in size to be portable. Along with this, a battery having a high energy density and a light weight is also adopted as a built-in battery. A typical battery that satisfies such a requirement is an active material such as lithium metal or lithium alloy, or a host material containing lithium ions (here, a host material refers to a material that can occlude and release lithium ions). Lithium intercalation compound occluded in a certain carbon is used as a negative electrode material, and LiC
This is a non-aqueous electrolyte secondary battery using an aprotic organic solvent in which a lithium salt such as l04 and LiPF6 is dissolved as an electrolyte.

This non-aqueous electrolyte secondary battery has a negative electrode plate in which the above-mentioned negative electrode material is held on a negative electrode current collector as a support, and a reversible electrochemical reaction with lithium ions such as a lithium-cobalt composite oxide. The positive electrode plate, which holds the positive electrode active material that reacts on the positive electrode current collector that is the support, from the separator that holds the electrolytic solution and intervenes between the negative electrode plate and the positive electrode plate to prevent a short circuit between the two electrodes Has become.

[0004] Each of the positive electrode plate and the negative electrode plate is formed into a thin sheet or foil shape, and is a power generating element formed by sequentially laminating or spirally winding through a separator. Then, the power generating element is housed in a battery container made of a metal such as stainless steel, nickel-plated iron, or aluminum, and after injecting the electrolytic solution, hermetically sealed with a lid plate to assemble the battery.

However, when a metal battery container is used,
Although it is highly airtight and has excellent mechanical strength,
There are great restrictions on battery weight, battery container material and design.

In order to solve the problem, a method has been proposed in which a power generating element is housed in a bag-shaped unit cell case.
In particular, by using a metal laminated resin film having an airtight structure as a material of the bag-shaped unit cell case,
There is no leakage of electrolyte or intrusion of moisture or the like from the outside of the battery, and the battery can be reduced in weight.

[0007] The shape of the power generating element is a wound type,
In particular, when the cross section is non-circular or oval, the electrode surface area can be increased and the manufacturing process can be simplified.

When such a non-aqueous electrolyte secondary battery is used in electronic equipment, a desired voltage is obtained as a unit cell or a plurality of cells connected in series. The single or plural batteries are housed in a housing made of resin or metal and resin together with the charge / discharge control circuit, and sealed so that the contents cannot be taken out, and used as a battery pack.

[0009]

In a conventional non-aqueous electrolyte secondary battery in which a separator is sandwiched between a sheet-shaped positive electrode plate and a sheet-shaped negative electrode plate and a cross-sectionally non-circular or oblong wound type power generating element is used, The wound type power generating element was housed in the bag-shaped unit cell case such that the center axis of the winding was perpendicular to the opening surface of the bag-shaped unit cell case.

In order to prevent loosening between the electrodes,
The wound power generating element has one side wall portion parallel to the winding center axis, a portion between the positive electrode lead and the negative electrode lead on a plane perpendicular to the winding center axis and from which the lead is taken out, and parallel to the winding center axis. The other side wall portion and a plane perpendicular to the center axis of the winding and from which no lead is taken out are fixed with a winding tape.

Further, the welded portion of the bag-shaped unit cell case parallel to the winding center axis of the power generating element is attached in a direction protruding from the surface of the bag-shaped unit cell case, and this welded portion is bent to form a bag-shaped unit case. It was used while pressed against the surface of the cell case.

However, in the conventional non-aqueous electrolyte secondary battery, the position of the winding tape of the power generation element and the position of the welded portion of the bag-shaped unit cell case parallel to the winding center axis of the power generation element are irrelevant. there were.

In the conventional non-aqueous electrolyte secondary battery having such a configuration, it is difficult to keep the interval between the electrode plates constant for a long time, and there is a problem that the discharge capacity is reduced when the charge / discharge cycle is repeated. there were.

[0014]

SUMMARY OF THE INVENTION The non-aqueous electrolyte secondary battery according to the present invention has been made in view of the above problems, and comprises a power generating element having a positive electrode plate, an isolator, and a negative electrode plate in a bag-shaped unit cell. In the non-aqueous electrolyte secondary battery housed in the case, the power generating element has one side wall portion parallel to the central axis, and between the positive electrode lead and the negative electrode lead in a plane perpendicular to the central axis and the lead is taken out, The bag-shaped case is fixed with a wrapping tape passing through the other side wall portion parallel to the central axis and a plane perpendicular to the central axis and from which no lead is taken out. The present invention is characterized in that a welded portion of the unit cell case is provided, and a welded portion of the bag-shaped unit cell case parallel to the central axis of the power generating element is located at a position overlapping the winding tape.

Further, according to the present invention, the bag-shaped unit cell case has an airtight structure, and the oval wound type power generating element is housed such that the winding center axis is perpendicular to the opening surface of the bag-shaped unit cell case. It is characterized by having been done. It should be noted that the vertical direction does not only mean a completely vertical direction but also a substantially vertical direction.

Further, the present invention is characterized in that the material of the bag-shaped unit cell case is a metal laminated resin film.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings, taking a battery provided with an elliptical winding type power generating element as an example. FIG. 1 shows the appearance of the nonaqueous electrolyte secondary battery according to the present invention. The elliptical wound-type power generating element is housed in the bag-shaped unit cell case such that the winding center axis is perpendicular to the opening surface of the bag-shaped unit cell case. It should be noted that the vertical direction does not only mean a completely vertical direction but also a substantially vertical direction.

In FIG. 1, 1 is a non-aqueous electrolyte secondary battery,
2 is a bag-shaped unit cell case, 3 is a positive electrode lead, 4 is a negative electrode lead, 5 is a welded portion of the bag-shaped unit cell case parallel to the winding central axis of the power generating element, and 6 is a bag-shaped unit cell case of a lead take-out unit. Reference numeral 7 denotes a welded portion of the bag-shaped unit cell case on the opposite side of the lead take-out portion.

Next, the manufacturing process of the non-aqueous electrolyte secondary battery according to the present invention will be described with reference to FIGS. Note that a metal laminated resin film was used as the material of the bag-shaped unit cell case.

2 to 5, symbols 2 to 7 are the same as those in FIG. 1, 8 is an elliptical wound type power generating element, 9 is a winding center axis of the oval wound type power generating element, and 10 is Reference numeral 16 denotes an opening surface of the bag-shaped unit cell case, which is a tape for stopping winding.

First, in the first step, an elliptical wound power generating element as shown in FIG. 2 was manufactured. The oval was wound around a polyethylene winding core with its long side parallel to the winding center axis of the power generating element to obtain an oval wound power generating element.

The outermost peripheral portion of the elliptical wound power generating element is shown in FIG.
As shown in, one side wall portion parallel to the winding center axis, between the positive electrode lead and the negative electrode lead in a plane perpendicular to the winding center axis and from which the lead is taken out, and parallel to the winding center axis. It is fixed with a winding tape 16 passing through the other side wall portion and a plane perpendicular to the winding center axis and from which no lead is taken out.

Next, in a second step, as shown in FIG. 3, both ends of the metal laminated resin film 2 are overlapped and thermally welded to produce a cylindrical bag-shaped unit cell case.

Next, in the third step, as shown in FIG. 4, the power generating element 8 is turned so that its winding center axis is perpendicular to the opening surface 10 of the bag-shaped unit cell case. Store in case.

Further, in the fourth step, as shown in FIG. 5, first, the welded portion 5 of the bag-shaped unit cell case parallel to the winding center axis of the power generating element is bent so as to be bent on the surface of the bag-shaped unit cell case. It is fixed to the surface of the bag-shaped unit cell case by a method such as pressing, bonding with an adhesive, or heat welding. Next, the lead take-out part of the metal laminate resin film 2 is heat-welded to form a welded part 6 of the bag-shaped unit cell case at the lead take-out part. Thereafter, the bag-shaped single cell case on the opposite side of the welded portion 6 of the lead take-out portion is heat-welded to form a heat-welded portion 7 on the opposite side of the lead take-out portion.

As the adhesive, various kinds of adhesives can be used according to the material of the surface of the metal laminated resin film.

The shape of the power generating element used in the present invention is not limited to an elliptical wound type in cross section, but may be a circular wound type, a non-circular wound type in cross section, or a flat plate-type electrode plate. A power generating element having any shape can be used, such as a stack type in which the sheet-shaped electrode plate is folded and a type in which the sheet-shaped electrode plate is folded and stacked through a separator.

When the shape of the power generating element is a stack type in which flat electrode plates are stacked via a separator or a type in which a sheet-shaped electrode plate is folded and stacked via a separator, the outer shape of the power generating element is a substantially rectangular parallelepiped. The lead terminals are taken out from one surface of the rectangular parallelepiped. The central axis of the power generating element having such a shape refers to an axis connecting the center of the surface from which the lead terminals are taken out and the center of the surface facing the surface from which the lead terminals are taken out.

In the present invention, a bag-shaped unit cell case having an airtight structure can be used, and as the material of the bag-shaped unit cell case, a metal laminated resin film is preferably used.

In the present invention, when the elliptical wound type power generating element is housed in the bag-shaped unit cell case, the winding center axis of the elliptical wound type power generating element is set at the opening surface of the bag-shaped unit cell case. Preferably it is vertical. The vertical direction is
It does not only mean completely vertical, but also generally vertical.

As the material of the metal of the metal laminated resin film, aluminum, aluminum alloy, titanium foil and the like can be used.

As the material of the heat-welded portion of the metal laminate resin film, any material may be used as long as it is a thermoplastic polymer material such as polyethylene or polypropylene.

Further, the resin layer and the metal foil layer of the metal laminate resin film are not limited to one layer each, but may be two or more layers.

As the material of the wrapping tape, a material that is not affected by the electrolytic solution used for the battery is used.

The electrolyte solvent used in the non-aqueous electrolyte secondary battery according to the present invention includes ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethyl Acetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
A polar solvent such as 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

The lithium salt dissolved in an organic solvent includes LiPF6, LiClO4, LiBF4, LiAs
F6, LiCF3CO2, LiCF3SO3, LiN
(SO2CF3) 2, LiN (SO2CF2CF3)
2, LiN (COCF3) 2 and LiN (COCF2)
A salt such as CF3) 2 or a mixture thereof may be used.

The separator of the non-aqueous electrolyte secondary battery according to the north invention may be a material obtained by impregnating an electrolytic solution in a microporous insulating polyethylene membrane, a solid polymer electrolyte, or a solid polymer electrolyte. A gel electrolyte or the like may be used. Further, an insulating microporous film and a solid polymer electrolyte may be used in combination. Further, when a porous solid polymer electrolyte membrane is used as the solid polymer electrolyte, the electrolyte contained in the polymer and the electrolyte contained in the pores may be different.

Further, as a compound capable of inserting and extracting lithium as a positive electrode material, an inorganic compound is represented by a composition formula L
ixMO2 or LiyM2O4 (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2), a composite oxide, an oxide having tunnel-like vacancies, or a metal chalcogenide having a layered structure is used. be able to. Specific examples thereof include LiCoO2, LiNiO2, and LiMn2O.
4, Li2Mn2O4, MnO2, FeO2, V2O
5, V6O13, TiO2, TiS2 and the like.
Examples of the organic compound include a conductive polymer such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, as a compound as a negative electrode material, A
Alloys of lithium with l, Si, Pb, Sn, Zn, Cd, etc., transition metal oxides such as LiFe2O3, WO2, MoO2, carbonaceous materials such as graphite, carbon, Li5
Lithium nitride such as (Li3N) or metallic lithium foil, or a mixture thereof may be used.

[0040]

Next, the present invention will be described based on preferred embodiments. The non-aqueous electrolyte secondary battery according to the present invention is a metal-laminated resin obtained by heat-sealing a metal-laminated resin film together with a non-aqueous electrolytic solution with an elliptical wound-type power generating element including a positive electrode plate, a separator, and a negative electrode plate. It is housed in a film case, and its appearance is the same as that shown in FIG.

As the positive electrode active material, a lithium cobalt composite oxide was used. The positive electrode plate is obtained by holding the above-mentioned lithium cobalt composite oxide as an active material on a current collector. As the current collector, an aluminum foil having a thickness of 20 μm was used. The positive electrode plate was prepared by mixing 6 parts of polyvinylidene fluoride as a binder and 3 parts of acetylene black as a conductive agent together with 91 parts of an active material, appropriately adding N-methylpyrrolidone to prepare a paste, and then collecting the paste. It was manufactured by applying and drying both sides of an electric conductor material.

The negative electrode plate was prepared by mixing 92 parts of graphite (graphite) as a host substance and 8 parts of polyvinylidene fluoride as a binder on both sides of a current collector, and adding N-methylpyrrolidone as appropriate. Was prepared by coating and drying. As the current collector of the negative electrode plate, a copper foil having a thickness of 14 μm was used.

The separator was a microporous polyethylene membrane, and the electrolyte was a mixed solution of ethylene carbonate: diethyl carbonate = 4: 6 (volume ratio) containing 1 mol / l of LiPF6.

The dimensions of the electrode plate were such that the positive electrode plate had a thickness of 180 μm,
Width 49mm, separator thickness 25μm, width 53mm,
The negative electrode plate has a thickness of 170 μm and a width of 51 mm, and the lead terminals are welded to the positive electrode plate and the negative electrode plate, respectively, and superposed in order, with the rectangular core as the center, and the long side parallel to the winding central axis of the power generating element. To form a power generating element having a size of 53 × 35 × 4 mm.

The power generating element is housed in a metal-laminated resin film case, and the elliptical wound-type power generating element is housed so that the winding center axis is perpendicular to the opening surface of the bag-shaped metal laminated resin film case. Heat-sealing the lead-out part of the metal laminate resin film case and sealing it,
The electrolyte was vacuum-injected in such an amount that each electrode and the separator were sufficiently wet and no free electrolyte was present outside the power generating element.

FIG. 5 shows a cross section taken along line AA 'of the battery shown in FIG. In FIG. 5, reference numeral 11 denotes a 12 μm PET film for protecting the surface of the outermost layer, 12 denotes a 20 μm aluminum foil as a barrier layer, and 13 denotes a 100 μm acid-modified polyethylene layer as a heat welding layer. A metal-laminated resin film case as a bag-shaped unit cell case for an airtight opening is composed of 11, 12, and 13. The outermost surface protective PET film 11 and an aluminum foil 12 as a barrier layer are bonded with a urethane-based adhesive. are doing. The positive electrode lead 3 and the negative electrode lead 4 have a thickness of 50 to 1
It is a metal conductor of copper, aluminum, nickel or the like of 00 μm.

In FIG. 5, reference numeral 14 denotes an adhesive layer;
Denotes an electrolyte barrier layer, and the positive electrode lead 3 and the negative electrode lead 4 adhere to a 100 μm acid-modified polyethylene layer forming an adhesive layer 14 with a metal, and a 70 μm evar resin ( (Kuraray ethylene vinyl alcohol copolymer resin) layer. When these are overlapped and bonded as shown in FIG. 5, good airtightness can be obtained.

The opposite side of the lead-out portion of the bag-shaped metal laminated resin film case is sealed by heat welding, and the welded portion of the bag-shaped single cell case parallel to the winding center axis of the power generating element is bent to form a bag-shaped single cell. Pressed against the surface of the battery case.
Then, the position of the winding tape and the welded portion of the bag-shaped single cell case parallel to the winding central axis of the power generating element were made to overlap.

The non-aqueous electrolyte secondary battery according to the present invention is referred to as Battery A.
The non-aqueous electrolyte secondary battery in which the welded portion of the bag-shaped single cell case parallel to the winding center axis of the conventional power generating element does not overlap the position of the winding tape is referred to as Battery B, and both have a nominal capacity of 500 mAh. Batteries were made 10 cells each. Each battery was subjected to a charge / discharge cycle test under the following conditions. Charge: 500 mA constant current + 4.1 V constant voltage, total 3 hr Discharge: 500 mA constant current, final voltage 2.75 V As a result, the average discharge capacity of 10 cells in the 100th cycle is 496 mAh for battery A and 465 mAh for battery B
In the non-aqueous electrolyte secondary battery according to the present invention, the capacity decrease due to the number of cycles was smaller.

[0050]

According to the non-aqueous electrolyte secondary battery of the present invention, the welding portion of the bag-shaped single cell case parallel to the winding center axis of the power generating element and the position of the winding tape overlap each other. In the part where the winding tape overlaps, the winding type power generating element is constantly pressed, and the distance between the electrodes is kept constant during the charge / discharge cycle, so the capacity decrease due to the number of cycles is reduced. is there.

According to the present invention, an oval metal laminated resin film case as a bag-shaped unit cell case, which does not cause deterioration in battery characteristics, has high safety, and does not cause complexity in the manufacturing process. A non-aqueous electrolyte battery in which a wound power generation element is stored can be provided.

Further, according to the present invention, since the power generating element is housed in, for example, a thin sheet-shaped soft case, it is excellent in airtightness and can eliminate the complexity of the sealing process, thereby reducing the manufacturing cost and the weight. Becomes possible.

In addition, since the cells have excellent airtightness, the airtightness of the hard case itself does not matter as in the conventional case. Therefore, since a one-touch assembly structure can be provided, the manufacture of the battery pack can be extremely facilitated. Furthermore, since the terminal for connecting external equipment formed by insert molding is formed in the battery container, it is possible to further simplify the manufacturing process and reduce the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is an external view of a nonaqueous electrolyte secondary battery.

FIG. 2 is a diagram showing a first step of the nonaqueous electrolyte secondary battery according to the present invention.

FIG. 3 is a view showing a second step of the nonaqueous electrolyte secondary battery according to the present invention.

FIG. 4 is a view showing a third step of the nonaqueous electrolyte secondary battery according to the present invention.

FIG. 5 is a view showing a fourth step of the nonaqueous electrolyte secondary battery according to the present invention.

FIG. 6 is a view showing a cross section (AA ′ cross section in FIG. 1) of a lead extraction portion of the nonaqueous electrolyte secondary battery according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Non-aqueous electrolyte secondary battery 2 Bag-shaped unit cell case 3 Positive electrode lead 4 Negative electrode lead 5 Welding part of bag-shaped unit cell case parallel to the center axis of winding of power generating element 6 Welding of bag-shaped unit cell case at lead take-out part Part 7 Welded part of bag-shaped single cell case on the side opposite to the lead take-out part 16 Winding tape

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H011 AA13 CC02 CC06 CC10 DD13 DD15 EE04 FF02 GG09 JJ25 5H029 AJ05 AJ12 AJ14 AK02 AK03 AK05 AK16 AL02 AL03 AL06 AL07 AL08 AL12 AM03 AM04 AM05 AM07 BJ01 HJ12JJ12 DJ01

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery in which a power generation element having a positive electrode plate, a separator, and a negative electrode plate is housed in a bag-shaped single cell case, wherein the power generation element has one side wall parallel to a central axis. A winding perpendicular to the central axis, between the positive electrode lead and the negative electrode lead where the lead is taken out, the other side wall part parallel to the central axis, and a plane perpendicular to the central axis and the lead is not taken out. The bag-shaped case has a welded portion of a bag-shaped unit cell case parallel to the central axis of the power generating element, and the welded portion of the bag-shaped unit cell case parallel to the central axis of the power generating element is fixed by a fixing tape. A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte secondary battery is located at a position overlapping with a winding tape. 2. A bag-shaped unit cell case has an airtight structure, and an oval wound type power generating element is housed such that a winding center axis thereof is perpendicular to an opening surface of the bag-shaped unit cell case. The non-aqueous electrolyte secondary battery according to claim 1, wherein: 3. The non-aqueous electrolyte battery according to claim 1, wherein the material of the bag-shaped unit cell case is a metal laminated resin film.