TWI811311B - Lithium secondary batteries and cards with built-in batteries - Google Patents

Abstract

The present invention provides a lithium secondary battery in the form of a film exterior. Even if the lithium composite oxide sintered body plate is used as a positive electrode plate, wrinkles are unlikely to occur near the end of the positive electrode plate even if the battery is repeatedly bent. This lithium secondary battery includes: a positive electrode plate which is a lithium composite oxide sintered body plate; a negative electrode layer; a separator; an electrolyte; and a pair of exterior films whose outer peripheries are sealed with each other to form an internal space for accommodating battery elements; the lithium secondary battery The thickness of the battery is 350-500 μm, the thickness of the positive plate is 70-120 μm, and the separation distance between the end of the positive plate and the end of the negative electrode layer is 50-2000 μm on the entire periphery of the positive plate and negative electrode layer.

Description

Lithium secondary batteries and cards with built-in batteries

The present invention relates to lithium secondary batteries and cards with built-in batteries.

In recent years, smart cards with built-in batteries are becoming practical. An example of a smart card with a built-in primary battery is a credit card with a one-time password display function. Examples of smart cards with built-in secondary batteries include cards equipped with fingerprint authentication and wireless communication functions that have wireless communication ICs, fingerprint analysis ASICs, and fingerprint sensors. Batteries for smart cards generally require the following characteristics: thickness less than 0.45mm, high capacity and low resistance, resistance to bending, and ability to withstand processing temperatures.

There have been proposals for secondary batteries for this purpose or cards equipped with secondary batteries. For example, Patent Document 1 (Japanese Patent Application Publication No. 2017-79192) discloses a secondary battery that is built into a plate member such as a card and has sufficient strength even when the plate member is bent and deformed. This secondary battery includes: an electrode body including a positive electrode and a negative electrode; a sheet-like laminated film exterior body in a state of covering the electrode body and welding the outer peripheral side; and one end side is connected to the aforementioned electrode body, and the other end side is connected from the laminated film The outer body has a positive connection terminal and a negative connection terminal extending outward. Furthermore, Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-331838) discloses a thin battery that is less prone to large wrinkles on the surface and has excellent bending resistance. This thin battery has a battery body part that accommodates a separator, a positive electrode layer, and a negative electrode layer, and a sealing part including a resin frame member that seals the periphery of the battery body part between a positive electrode current collector and a negative electrode current collector. ; When the thickness of the sealing part is D1 and the maximum thickness of the central part of the battery is D2, it satisfies 100μm≦D1≦320μm, and D1/D2≦0.85. The secondary batteries disclosed in Patent Documents 1 and 2 use a powder-dispersed positive electrode produced by coating and drying a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like.

Generally speaking, the powder-dispersed cathode contains a relatively large amount (for example, about 10% by weight) of components (binders, conductive additives) that do not contribute to capacity, so the filling density of the lithium composite oxide as the cathode active material becomes Low. Therefore, there is still a lot of room for improvement in terms of capacity and charge and discharge efficiency of powder-dispersed cathodes. Therefore, some people try to improve the capacity and charge and discharge efficiency by using a lithium composite oxide sintered body plate to form a positive electrode or a positive electrode active material layer. At this time, there is no binder or conductive additive in the positive electrode or the positive electrode active material layer, so the filling density of the lithium composite oxide will be higher. This can be expected to achieve high capacity and good charge and discharge efficiency. For example, Patent Document 3 (Japanese Patent No. 5587052) discloses a positive electrode for a lithium secondary battery, which includes a positive electrode current collector and a positive electrode active material layer joined to the positive electrode current collector via a conductive joint layer. The positive active material layer is composed of a lithium composite oxide sintered body plate with a thickness of 30 μm or more, a porosity of 3 to 30%, and an opening rate of 70% or more. Furthermore, Patent Document 4 (International Publication No. 2017/146088) discloses that as a positive electrode of a lithium secondary battery equipped with a solid electrolyte, an aligned sintered body plate containing lithium such as lithium cobalt oxide (LiCoO ₂ ) is used. A plurality of primary particles composed of a composite oxide are aligned with an average alignment angle of more than 0° and less than 30° with respect to the surface of the positive electrode plate. [Prior art documents] [Patent documents]

[Patent Document 1] Japanese Patent Application Publication No. 2017-79192 [Patent Document 2] Japanese Patent Application Publication No. 2006-331838 [Patent Document 3] Japanese Patent No. 5587052 [Patent Document 4] International Publication No. 2017/146088

[Problem to be solved by the invention]

However, a card incorporating a thin-film exterior battery equipped with a lithium composite oxide sintered body plate (positive electrode plate) as disclosed in Patent Documents 3 and 4 cannot be bent repeatedly hundreds of times as required by JIS standards (Japanese Industrial Standards). During testing, there were problems such as wrinkles easily forming on the surface of the card near the end of the positive plate.

The inventors of the present case have discovered that in a lithium secondary battery in the form of a thin film exterior battery having a sintered positive electrode plate, the thickness of the lithium secondary battery, the thickness of the positive electrode plate, and the end of the positive electrode plate and the negative electrode The separation distance between the ends of the layers satisfies predetermined conditions, and wrinkles are not easily generated near the ends of the positive electrode plate even if it is repeatedly bent. In particular, we found that for film-covered lithium secondary batteries that meet the above conditions, wrinkles are less likely to occur near the end of the positive electrode plate even when the repeated bending test required by JIS standards is performed hundreds of times in the form of a card with a built-in battery. pleats.

Therefore, an object of the present invention is to provide a lithium secondary battery in the form of a film exterior, which has a lithium composite oxide sintered body plate as a positive electrode plate and is not easily bent even if it is repeatedly bent (especially in the form of a card with a built-in battery). Wrinkles occur near the end of the positive plate. [Means to solve the problem]

According to one aspect of the present invention, a lithium secondary battery can be provided, having: The positive plate is a lithium composite oxide sintered body plate; The negative electrode layer has a larger size than the aforementioned positive electrode plate and contains carbon; A separator is interposed between the positive electrode plate and the negative electrode layer, and is larger in size than the positive electrode plate and the negative electrode layer; Electrolyte, impregnated in the aforementioned positive electrode plate, the aforementioned negative electrode layer, and the aforementioned separator; and 1 pair of exterior films, the outer peripheries of which are sealed to each other to form an internal space, and the internal space accommodates the aforementioned positive electrode plate, the aforementioned negative electrode layer, the aforementioned separator, and the aforementioned electrolyte; The outer peripheral portion of the separator is in close contact with at least the outer peripheral edge of the positive electrode plate side exterior film or the surrounding area near it, and isolates the block housing the positive electrode from the block housing the negative electrode, The thickness of the aforementioned lithium secondary battery is 350 to 500 μm, the thickness of the aforementioned positive electrode plate is 70 to 120 μm, and the separation distance between the end of the aforementioned positive electrode plate and the end of the aforementioned negative electrode layer is the entire outer periphery of the aforementioned positive electrode plate and the aforementioned negative electrode layer. 50～2000μm.

According to another aspect of the present invention, a card with a built-in battery is provided, including a resin base material and the aforementioned lithium secondary battery embedded in the resin base material.

Lithium secondary battery An example of the lithium secondary battery of the present invention is schematically shown in FIG. 1 . The lithium secondary battery 10 shown in FIG. 1 includes a positive electrode plate 16, a separator 18, a negative electrode layer 20, an electrolyte 24, and a pair of exterior films 26. The positive electrode plate 16 is a lithium composite oxide sintered body plate. The negative electrode layer 20 contains carbon and has a larger size than the positive electrode plate 16 . The separator 18 is interposed between the positive electrode plate 16 and the negative electrode layer 20 , and has a larger size than the sizes of the positive electrode plate 16 and the negative electrode layer 20 . The electrolyte 24 impregnates the positive electrode plate 16, the negative electrode layer 20, and the separator 18. The outer peripheral edges of a pair of exterior films 26 are sealed to each other to form an internal space, and the positive electrode plate 16, the negative electrode layer 20, the separator 18, and the like are accommodated in the internal space. and electrolyte 24. The outer peripheral part of the separator 18 is in close contact with at least the outer peripheral edge of the exterior film 26 on the side of the positive electrode plate 16 or the surrounding area near it, and isolates the block that accommodates the positive electrode plate 16 from the block that accommodates the negative electrode layer 20 . In addition, the thickness of the lithium secondary battery 10 is 350 to 500 μm, and the thickness of the positive electrode plate 16 is 70 to 120 μm. In addition, the separation distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 is 50 to 2000 μm over the entire outer circumference of the positive electrode plate 16 and the negative electrode layer 20 . In this way, in the lithium secondary battery 10 in the form of a film-covered battery having a positive electrode sintered body plate, the thickness of the lithium secondary battery 10 , the thickness of the positive electrode plate 16 , and the end of the positive electrode plate 16 and the negative electrode layer 20 The separation distance D between the ends satisfies the predetermined conditions, and wrinkles are not easily generated near the ends of the positive electrode plate even if it is repeatedly bent. In particular, even when the lithium secondary battery 10 satisfying the above conditions is subjected to hundreds of repeated bending tests required by JIS standards in the form of a card with a built-in battery, wrinkles are less likely to occur near the end of the positive electrode plate.

That is, as mentioned above, when a card with a built-in film-covered battery equipped with a lithium composite oxide sintered body plate (positive electrode plate) as disclosed in Patent Documents 3 and 4 is subjected to hundreds of repeated bending required by JIS standards, During the test, there is a problem that wrinkles easily occur on the surface of the card near the end of the positive plate. In this regard, according to the lithium secondary battery of the present invention, these wrinkles can be effectively suppressed. The reason for this is not clear yet, but it is thought that, for example, it is because it is difficult for the end portion of the positive electrode plate 16 to push up the exterior film 26 . Therefore, the lithium secondary battery 10 of the present invention is preferably a thin secondary battery that can be built into a card, and is more preferably a thin secondary battery that can be embedded in a resin substrate and formed into a card. That is, according to another ideal aspect of the present invention, a card with a built-in battery can be provided, including a resin base material and a lithium secondary battery embedded in the resin base material. The card with a built-in battery typically has a pair of resin films and a lithium secondary battery sandwiched between the pair of resin films. The resin films are preferably bonded to each other by an adhesive or by heating and pressing. It is preferable to thermally fuse the resin films to each other.

The positive electrode plate 16 is a lithium composite oxide sintered body plate. The positive plate 16 is a sintered body plate, which means that the positive plate 16 does not contain a binder. This is because even if the green sheet contains a binder, the binder will disappear or burn out during calcination. In addition, since the positive electrode plate 16 does not contain a binder, there is an advantage that deterioration of the positive electrode caused by the electrolyte 24 can be avoided. In addition, it is particularly preferred that the lithium composite oxide constituting the sintered body plate is lithium cobalt oxide (typically LiCoO ₂ (hereinafter, sometimes abbreviated as LCO)). Various lithium composite oxide sintered body plates or LCO sintered body plates are known, and those disclosed in Patent Document 3 (Japanese Patent No. 5587052) and Patent Document 4 (International Publication No. 2017/146088) can be used, for example.

According to an ideal aspect of the present invention, the positive electrode plate 16 , that is, the lithium composite oxide sintered body plate, preferably contains a plurality of primary particles composed of a lithium composite oxide, and the plurality of primary particles are positioned relative to the surface of the positive electrode plate. Alignment positive plates that are aligned at an average alignment angle exceeding 0° and below 30°. FIG. 3 shows an example of an SEM image of a cross-section of the aligned positive plate 16 perpendicular to the plate surface. On the other hand, FIG. 4 shows an electron backscatter diffraction (EBSD) of the aligned positive plate 16 of a cross-section perpendicular to the plate surface. Diffraction) image. In addition, FIG. 5 shows a histogram representing the alignment angle distribution of the primary particles 11 in the EBSD image of FIG. 4 on an area basis. In the EBSD image shown in Figure 4, discontinuities in crystal orientation can be observed. In FIG. 4 , the alignment angle of each primary particle 11 is represented by the depth of the color. The darker the color, the smaller the alignment angle. The alignment angle is the inclination angle formed by the (003) plane of each primary particle 11 relative to the direction of the plate surface. In addition, in FIGS. 3 and 4 , the portions shown in black inside the aligned positive electrode plate 16 are pores.

The aligned positive electrode plate 16 is an aligned sintered body composed of a plurality of primary particles 11 bonded to each other. Each primary particle 11 is mainly plate-shaped, but may also be formed into a rectangular parallelepiped shape, a cubic shape, a spherical shape, or the like. The cross-sectional shape of each primary particle 11 is not particularly limited, and may be a rectangular shape, a polygonal shape other than a rectangular shape, a circular shape, an elliptical shape, or a complex shape other than these.

Each primary particle 11 is composed of lithium composite oxide. The lithium composite oxide is an oxide represented by Li _x MO ₂ (0.05<x<1.10, M is at least one transition metal, and M typically contains one or more of Co, Ni, and Mn). Lithium composite oxide has a layered rock salt structure. The layered rock salt structure refers to a crystal structure in which lithium layers and transition metal layers other than lithium are alternately stacked with oxygen layers sandwiched between them. That is, transition metal ion layers and lithium layers are alternately laminated with oxide ions interposed therebetween. A stacked crystal structure (representatively α-NaFeO ₂ -type structure, that is, a structure in which transition metals and lithium are regularly arranged along the [111] axis direction of a cubic crystal rock salt type structure). Examples of lithium composite oxides include: Li _x CoO ₂ (lithium cobalt oxide), Li _x NiO ₂ (lithium nickel oxide), Li _x MnO ₂ (lithium manganate), Li _x NiMnO ₂ (lithium nickel manganate), _{Li _ _ _ _ _ _ _} for LiCoO ₂ ). The lithium composite oxide may also contain Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, Sb, Te One or more elements among , Ba, Bi, and W.

As shown in FIGS. 4 and 5 , the average value of the alignment angle of each primary particle 11 , that is, the average alignment angle, is more than 0° and less than 30°. Through this, the following various advantages can be obtained. First, since each primary particle 11 is in an inclined direction with respect to the thickness direction, the adhesion between the primary particles can be improved. As a result, the lithium ion conductivity between a certain primary particle 11 and other primary particles 11 adjacent to both sides of the primary particle 11 in the longitudinal direction can be improved, thereby improving rate characteristics. Second, the speed characteristics can be further improved. The reason is: as mentioned above, when lithium ions move in and out, in the aligned positive electrode plate 16, the expansion and contraction in the thickness direction is more dominant than the expansion and contraction in the plate surface direction, so the expansion and contraction of the aligned positive electrode plate 16 becomes smooth and consistent with the expansion and contraction of the aligned positive electrode plate 16. Along with this, the movement of lithium ions also becomes smoother.

The average alignment angle of the primary particles 11 is obtained by the following method. First, in the EBSD image obtained by observing a rectangular area of 95 μm × 125 μm at a magnification of 1000 times as shown in FIG. 4 , draw three transverse lines dividing the aligned positive electrode plate 16 into four quarters along the thickness direction, and three A longitudinal line dividing the aligned positive electrode plate 16 into four equal parts along the direction of the plate surface. Then, the average alignment angle of the primary particles 11 is obtained by arithmetic averaging the alignment angles of all the primary particles 11 intersecting at least one of the three transverse lines and the three longitudinal lines. From the perspective of further improving the rate characteristics, the average alignment angle of the primary particles 11 is preferably 30° or less, and more preferably 25° or less. From the perspective of further improving the rate characteristics, the average alignment angle of the primary particles 11 is preferably 2° or more, and more preferably 5° or more.

As shown in FIG. 5 , the alignment angle of each primary particle 11 can be widely distributed between 0° and 90°, but most of them are preferably distributed in a region exceeding 0° and below 30°. That is, when the cross section of the aligned sintered body constituting the aligned positive electrode plate 16 is analyzed by EBSD, the alignment angle of the primary particles 11 contained in the analyzed cross section with respect to the surface of the aligned positive electrode plate 16 exceeds 0° and is within 30°. The total area of the following primary particles 11 (hereinafter, referred to as low-angle primary particles) is relative to the total area of the primary particles 11 included in the cross section (specifically, the 30 primary particles 11 used in the calculation of the average alignment angle) , preferably more than 70%, more preferably more than 80%. This can increase the proportion of primary particles 11 with high mutual adhesion, so the rate characteristics can be further improved. In addition, the total area of the low-angle primary particles with an alignment angle of 20° or less is preferably 50% or more of the total area of the 30 primary particles 11 used in the calculation of the average alignment angle. Furthermore, the total area of the low-angle primary particles with an alignment angle of 10° or less is preferably 15% or more of the total area of the 30 primary particles 11 used in the calculation of the average alignment angle.

Each primary particle 11 is mainly plate-shaped, so as shown in FIGS. 3 and 4 , the cross-section of each primary particle 11 extends in a predetermined direction, and is typically approximately rectangular in shape. That is, when the cross section of the aligned sintered body is analyzed by EBSD, the total area of the primary particles 11 with an aspect ratio of 4 or more among the primary particles 11 included in the analyzed cross section is smaller than the total area of the primary particles 11 included in the cross section (specifically, , the total area of the 30 primary particles 11) used in the calculation of the average alignment angle is preferably more than 70%, and more preferably more than 80%. Specifically, in the EBSD image shown in FIG. 4 , the mutual adhesion between the primary particles 11 can be further improved, and as a result, the rate characteristics can be further improved. The aspect ratio of the primary particle 11 is a value obtained by dividing the Feret maximum diameter (Feret Max) of the primary particle 11 by the Feret minimum diameter (Feret Min). The Felt maximum diameter is the maximum distance between two parallel straight lines when the primary particle 11 is sandwiched between the straight lines in the EBSD image during cross-sectional observation. The Felt minimum path is the minimum distance between two parallel straight lines when the primary particle 11 is sandwiched between the straight lines in the EBSD image.

The average particle diameter of the plurality of primary particles constituting the aligned sintered body is preferably 5 μm or more. Specifically, the average particle diameter of the 30 primary particles 11 used in the calculation of the average alignment angle is preferably 5 μm or more, more preferably 7 μm or more, particularly preferably 12 μm or more. Thereby, the number of particle boundaries between the primary particles 11 in the direction of lithium ion conduction is reduced, and the overall lithium ion conductivity is improved, so the rate characteristics can be further improved. The average particle diameter of the primary particles 11 is a value obtained by arithmetically averaging the circular equivalent diameters of each primary particle 11 . The circle equivalent diameter refers to the diameter of a circle having the same area as each primary particle 11 in the EBSD image.

The density of the aligned sintered body constituting the aligned positive electrode plate 16 is preferably above 70%, more preferably above 80%, even more preferably above 90%. Thereby, the mutual adhesion between the primary particles 11 can be further improved, so the rate characteristics can be further improved. The density of the aligned sintered body was calculated by polishing the cross section of the positive electrode plate using CP (section polishing) polishing, then conducting SEM observation at a magnification of 1000, and binarizing the obtained SEM image. The average circular equivalent diameter of each pore formed inside the aligned sintered body is not particularly limited, but is preferably 8 μm or less. The smaller the average circular equivalent diameter of each pore is, the more the mutual adhesion between the primary particles 11 can be further improved, and as a result, the rate characteristics can be further improved. The average circular equivalent diameter of the pores is the arithmetic average of the circular equivalent diameters of 10 pores in the EBSD image. The circle equivalent diameter refers to the diameter of a circle with the same area as each pore in the EBSD image. Each pore formed inside the aligned sintered body may be an opening communicating with the outside of the aligned positive electrode plate 16 , but preferably does not penetrate the aligned positive electrode plate 16 . In addition, each pore may also be a closed hole.

The thickness of the positive electrode plate 16 is 70-120 μm, preferably 80-100 μm, more preferably 80-95 μm, particularly preferably 85-95 μm. If it is within this range, the active material capacity per unit area can be increased and the energy density of the lithium secondary battery 10 can be improved, and the deterioration of battery characteristics (especially the increase in resistance value) accompanying repeated charging and discharging can be suppressed, thereby suppressing Wrinkles occur near the end of the positive electrode plate 16 due to repeated bending. In addition, the size of the positive plate 16 is preferably 5 mm × 5 mm square or more, more preferably 10 mm × 10 mm ~ 200 mm × 200 mm square, especially 10 mm × 10 mm ~ 100 mm × 100 mm square. In other words, it is preferably 25 mm ² or more, more preferably 100～40000mm ² , preferably 100～10000mm ² .

The negative electrode layer 20 contains carbon as a negative electrode active material. Examples of carbon include graphite, thermally decomposed carbon, coke, calcined resin, mesophase pellets, mesophase pitch, etc., and graphite is preferred. Graphite can be any of natural graphite and artificial graphite. The negative electrode layer 20 should further contain a binder. Examples of the binder include styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc., and preferably styrene butadiene rubber (SBR) or polyvinylidene fluoride Ethylene (PVDF). Especially when using γ-butyrolactone (GBL), which has excellent heat resistance, as the electrolyte 24, styrene butadiene rubber (SBR) is used as the adhesive, considering that it is not easily dissolved in GBL and can avoid deterioration of the binder function due to heating. agent is better.

The thickness of the negative electrode layer 20 is not particularly limited, but is preferably 70 to 160 μm, more preferably 80 to 150 μm, even more preferably 90 to 140 μm, particularly preferably 100 to 130 μm. Within this range, the active material capacity per unit area can be increased and the energy density of the lithium secondary battery 10 can be improved, and the occurrence of wrinkles near the end of the positive electrode plate 16 caused by repeated bending can be more effectively suppressed. .

The separator 18 is preferably made of polyolefin, polyimide, polyester (eg polyethylene terephthalate (PET)) or cellulose. Examples of the polyolefin include polypropylene (PP), polyethylene (PE), and combinations thereof. From the viewpoint of low price, polyolefin or cellulose separators are preferred. In addition, the surface of the partition 18 may be coated with ceramics such as aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), and silicon dioxide (SiO ₂ ). On the other hand, from the viewpoint of excellent heat resistance, a separator made of polyimide or cellulose is suitable. Unlike widely used polyolefin separators with poor heat resistance, separators made of polyimide, polyester (such as polyethylene terephthalate (PET)) or cellulose have excellent heat resistance. , not only that, but also has excellent wettability to γ-butyrolactone (GBL), an electrolyte component with excellent heat resistance. Therefore, when using an electrolyte containing GBL, the electrolyte can fully penetrate into the separator (no repulsion will occur). From the viewpoint of heat resistance, particularly preferred dividers are polyimide dividers. Separators made of polyimide are commercially available. Due to their extremely complex microstructure, they have the advantage of being able to more effectively prevent or delay the extension of lithium dendrites precipitated during overcharging and the resulting short circuit.

The electrolyte solution 24 is not particularly limited, and may be used with an organic solvent (for example, a mixed solvent of ethyl carbonate (EC) and methyl ethyl carbonate (MEC), ethyl carbonate (EC), and diethyl carbonate (DEC). A commercially available electrolyte for lithium batteries, such as a liquid obtained by dissolving a lithium salt (such as LiPF ₆ ) in a mixed solvent or a mixed solvent of ethyl carbonate (EC) and ethyl methyl carbonate (EMC), can be used.

When producing a lithium secondary battery with excellent heat resistance, the electrolyte solution 24 is preferably composed of lithium fluoroboride (LiBF ₄ ) in a non-aqueous solvent. In this case, the non-aqueous solvent may be a single solvent composed of γ-butyrolactone (GBL), or a mixed solvent composed of γ-butyrolactone (GBL) and ethyl carbonate (EC). By containing γ-butyrolactone (GBL), the non-aqueous solvent raises its boiling point, leading to a significant improvement in heat resistance. Considering this point of view, the volume ratio of EC:GBL in the non-aqueous solvent is preferably 0:1 to 1:1 (GBL ratio 50 to 100 volume %), and more preferably 0:1 to 1:1.5 (GBL ratio 60 to 100 Volume %), particularly preferably 0:1 to 1:2 (GBL ratio 66.6 to 100 volume %), particularly preferably 0:1 to 1:3 (GBL ratio 75 to 100 volume %). Lithium fluoroboride (LiBF ₄ ) dissolved in a non-aqueous solvent is an electrolyte with a high decomposition temperature, which also leads to a significant improvement in heat resistance. The LiBF ₄ concentration in the electrolyte 24 is preferably 0.5-2 mol/L, more preferably 0.6-1.9 mol/L, even more preferably 0.7-1.7 mol/L, particularly preferably 0.8-1.5 mol/L.

The electrolyte 24 preferably further contains vinyl carbonate (VC) and/or fluoroethyl carbonate (FEC) and/or ethylene ethyl carbonate (VEC) as additives. Both VC and FEC have excellent heat resistance. Therefore, since the electrolyte 24 contains these additives, an SEI film with excellent heat resistance can be formed on the surface of the negative electrode layer 20 .

The thickness of the lithium secondary battery 10 is 350-500 μm, preferably 380-450 μm, more preferably 400-430 μm. If the thickness is within this range, a thin lithium battery suitable for being built into thin devices such as smart cards can be made. In addition, the relationship between the thickness of the positive electrode plate 16 and the separation distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 helps to suppress the occurrence of wrinkles near the end of the positive electrode plate 16 caused by repeated bending. .

The outer peripheries of the pair of exterior films 26 are sealed with each other to form an internal space, and the battery element 12 and the electrolyte 24 are accommodated in the internal space. That is, as shown in FIG. 1 , the battery element 12 and the electrolyte 24 contained in the lithium secondary battery 10 are packaged and sealed with a pair of exterior films 26. As a result, the lithium secondary battery 10 becomes a so-called The shape of the film-wrapped battery. Here, the battery element 12 is defined as including the positive electrode plate 16, the separator 18 and the negative electrode layer 20, and typically further includes a positive electrode current collector (not shown in the figure) and a negative electrode current collector (not shown in the figure). ). The positive electrode current collector and the negative electrode current collector are not particularly limited, but are preferably metal foils such as copper foil and aluminum foil. The positive electrode current collector is preferably interposed between the positive electrode plate 16 and the exterior film 26 , and the negative electrode current collector is preferably interposed between the negative electrode layer 20 and the exterior film 26 . In addition, the positive electrode terminal is preferably provided on the positive electrode current collector in a form extending from the positive electrode current collector, and the negative electrode terminal is preferably provided on the negative electrode current collector in a form extending from the negative electrode current collector. The outer edges of the lithium secondary battery 10 are preferably sealed by thermally welding the exterior films 26 to each other. For sealing using heat fusion, it is advisable to use a heating rod (also called a heat bar) commonly used in heat sealing applications. Typically, the lithium secondary battery 10 is preferably in a quadrangular shape, and the outer periphery of a pair of exterior films 26 is sealed on all four sides of the outer periphery.

As the exterior film 26, a commercially available exterior film may be used. The thickness of the exterior film 26 is preferably 50-80 μm per piece, more preferably 55-70 μm, even more preferably 55-65 μm. The ideal exterior film 26 is a laminated film composed of a resin film and a metal foil, and more preferably, an aluminum laminated film composed of a resin film and aluminum foil. In the case of a laminated film, it is preferable to provide resin films on both sides of metal foil such as aluminum foil. At this time, the resin film on one side of the metal foil (hereinafter referred to as the surface protective film) is preferably made of nylon, polyamide, polyethylene terephthalate, polyimide, polytetrafluoroethylene, poly It is made of materials with excellent reinforcing properties such as chlorotrifluoroethylene. The resin film on the other side of the metal foil should be made of heat sealing materials such as polypropylene.

As mentioned above, the negative electrode layer 20 has a larger size than the positive electrode plate 16 . On the other hand, the separator 18 has a larger size than the positive electrode plate 16 and the negative electrode layer 20 . In addition, the outer peripheral part of the separator 18 is in close contact with at least the outer peripheral edge of the exterior film 26 on the side of the positive electrode plate 16 or the surrounding area near it, and isolates the area that accommodates the positive electrode plate 16 from the area that accommodates the negative electrode layer 20 . In addition, the outer peripheral portion of the separator 18 may be in close contact with the outer peripheral edge of the exterior film 26 on the negative electrode layer 20 side or the surrounding area near the negative electrode layer 20 side.

The separation distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 is 50 to 2000 μm, preferably 200 to 1500 μm, more preferably 200 to 1000 μm, particularly preferably 200～800μm, particularly preferably 450～600μm, optimally 450～550μm. Here, the separation distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20, as shown in FIG. 1, means the distance from the end of the positive electrode plate 16 to the end of the adjacent negative electrode layer 20, In other words, it can be said to mean the width of the negative electrode layer 20 extending from the positive electrode plate 16 .

Method for Manufacturing Lithium Cobalt Oxide Aligned Sintered Plate The aligned positive electrode plate or aligned sintered plate ideally used in the lithium secondary battery of the present invention can be manufactured by any manufacturing method, preferably as illustrated below, via (1) LiCoO ₂ template particles (template particles), (2) matrix particles, (3) green sheets, and (4) aligned sintered plates are manufactured.

(1) Preparation of LiCoO ₂ template particles Mix Co ₃ O ₄ raw material powder and Li ₂ CO ₃ raw material powder. The obtained mixed powder is calcined at 500-900°C for 1-20 hours to synthesize LiCoO ₂ powder. The obtained LiCoO ₂ powder is pulverized into a volume basis D50 particle diameter of 0.1 to 10 μm using a pot mill to obtain plate-shaped LiCoO ₂ particles that can conduct lithium ions parallel to the plate surface. The obtained LiCoO ₂ particles are in a state that is easily cut along the cleavage plane. LiCoO _template particles are produced by disintegrating and cutting the _LiCoO particles. Such LiCoO ₂ particles can also be obtained by the following methods: growing green sheets obtained by using LiCoO ₂ powder slurry and then disintegrating them; using a flux method, hydrothermal synthesis, and using single crystals from a molten liquid Growth, sol-gel method, etc. are used to synthesize plate-shaped crystals.

In this step, as described below, the characteristics of the primary particles 11 constituting the aligned positive electrode plate 16 can be controlled. - By adjusting at least one of the aspect ratio and particle size of _LiCoO2 template particles, the total area ratio of low-angle primary particles with an alignment angle exceeding 0° and below 30° can be controlled. Specifically, the larger the aspect ratio of the LiCoO ₂ template particles or the larger the particle diameter of the LiCoO ₂ template particles, the more the total area ratio of the low-angle primary particles can be increased. The aspect ratio and particle size of the LiCoO ₂ template particles can be adjusted by adjusting the particle sizes of the Co ₃ O ₄ raw material powder and Li ₂ CO ₃ raw material powder, the grinding conditions during grinding (crushing time, grinding energy, grinding method, etc.), and at least one of the crushed grades to control. - By adjusting the aspect ratio of the LiCoO ₂ template particles, the total area ratio of the primary particles 11 with an aspect ratio of 4 or more can be controlled. Specifically, the larger the aspect ratio of the LiCoO ₂ template particles, the more the total area ratio of the primary particles 11 with an aspect ratio of 4 or more can be increased. The aspect ratio of the _LiCoO2 template particles is adjusted as described above. - By adjusting the particle size of the LiCoO ₂ template particles, the average particle size of the primary particles 11 can be controlled. - By adjusting the particle size of the LiCoO ₂ template particles, the density of the aligned positive electrode plate 16 can be controlled. Specifically, the smaller the particle size of the LiCoO ₂ template particles, the more the density of the aligned positive electrode plate 16 can be increased.

(2) Preparation of matrix particles Co ₃ O ₄ raw material powder is used as matrix particles. The volume-based D50 particle size of the Co ₃ O ₄ raw material powder is not particularly limited. For example, it can be 0.1 to 1.0 μm. The volume-based D50 particle size of the LiCoO ₂ template particles should ideally be small. The matrix particles can also be obtained by heat-treating the Co(OH) ₂ raw material at 500 to 800°C for 1 to 10 hours. In addition, in addition to Co ₃ O ₄ , Co(OH) ₂ particles or LiCoO ₂ particles may be used as the matrix particles.

In this step, as described below, the characteristics of the primary particles 11 constituting the aligned positive electrode plate 16 can be controlled. - By adjusting the ratio of the particle size of the matrix particles to the particle size of the LiCoO ₂ template particles (hereinafter referred to as the "matrix/template particle size ratio"), the alignment angle can be controlled to exceed 0° and be below 30°. The total area ratio of low-angle primary particles. Specifically, the smaller the matrix/template particle size ratio, that is, the smaller the particle size of the matrix particles, the easier it is for the matrix particles to be incorporated into the _LiCoO2 template particles in the calcination step described later, so the total area of the low-angle primary particles can be increased. Proportion. - By adjusting the matrix/template particle size ratio, the total area ratio of primary particles 11 with an aspect ratio of 4 or more can be controlled. Specifically, the smaller the matrix/template particle size ratio, that is, the smaller the particle size of the matrix particles, the more the total area ratio of the primary particles 11 with an aspect ratio of 4 or more can be increased. - By adjusting the matrix/template particle size ratio, the density of the aligned positive plate 16 can be controlled. Specifically, the smaller the matrix/template particle size ratio, that is, the smaller the particle size of the matrix particles, the more the density of the aligned positive electrode plate 16 can be increased.

(3) Preparation of green sheet Mix LiCoO ₂ template particles and matrix particles at a ratio of 100:0 to 3:97 to obtain mixed powder. The mixed powder, dispersion medium, binder, plasticizer and dispersant are mixed, stirred and defoamed under reduced pressure, and adjusted to a desired viscosity to prepare a slurry. Then, the prepared slurry is shaped using a shaping method that can apply shear force to the LiCoO ₂ template particles to form a shaped body. In this way, the average alignment angle of each primary particle 11 can be made to exceed 0° and be 30° or less. The ideal molding method that can apply shear force to the LiCoO ₂ template particles is the doctor blade method. When using the doctor blade method, the prepared slurry is formed on a PET film to form a green sheet as a formed body.

In this step, as described below, the characteristics of the primary particles 11 constituting the aligned positive electrode plate 16 can be controlled. - By adjusting the molding speed, the total area ratio of low-angle primary particles whose alignment angle exceeds 0° and is less than 30° can be controlled. Specifically, the faster the molding speed, the more the total area ratio of the low-angle primary particles can be increased. - By adjusting the density of the molded body, the average particle size of the primary particles 11 can be controlled. Specifically, the greater the density of the molded body, the greater the average particle diameter of the primary particles 11 can be increased. - By adjusting the mixing ratio of LiCoO ₂ template particles and matrix particles, the density of the aligned positive electrode plate 16 can be controlled. Specifically, the more LiCoO ₂ template particles there are, the more the density of the aligned positive electrode plate 16 can be reduced.

(4) Preparation of aligned sintered plate The molded body of the slurry is placed on a carrier plate made of zirconia, and heat treatment (primary calcination) is performed at 500 to 900° C. for 1 to 10 hours to obtain an intermediate sintered plate. The sintered plate is placed on a zirconia carrier plate in a state of being sandwiched up and down by lithium sheets (for example, sheets containing Li ₂ CO ₃ ), and is fired twice, thereby obtaining a LiCoO ₂ sintered plate. Specifically, a carrier plate on which a sintered plate sandwiched by lithium sheets is mounted is placed in an alumina sheath, and is calcined in the atmosphere at 700 to 850° C. for 1 to 20 hours, and then the sintered plate is further sintered using lithium sheets. The LiCoO ₂ sintered plate is obtained by calcining at 750-900°C for 1-40 hours while being clamped up and down. This calcining step can be carried out in two times or once. When calcining in two times, the first calcining temperature should be lower than the second calcining temperature. In addition, the total amount of lithium sheets used in the two calcinings is such that the molar ratio of the amount of Li in the green sheet and the lithium sheet relative to the amount of Co in the green sheet, that is, the Li/Co ratio, becomes 1.0. Can.

In this step, as described below, the characteristics of the primary particles 11 constituting the aligned positive electrode plate 16 can be controlled. - By adjusting the temperature rise rate during calcination, the total area ratio of low-angle primary particles whose alignment angle exceeds 0° and is less than 30° can be controlled. Specifically, the faster the temperature rise rate is, the more sintering of the matrix particles can be suppressed, and the total area ratio of the low-angle primary particles can be increased. - By adjusting the heat treatment temperature of the intermediate, it is also possible to control the total area ratio of low-angle primary particles whose alignment angle exceeds 0° and is less than 30°. Specifically, the lower the heat treatment temperature of the intermediate, the more sintering of the matrix particles can be suppressed, and the total area ratio of the low-angle primary particles can be increased. - By adjusting at least one of the temperature rise rate during calcination and the heat treatment temperature of the intermediate, the average particle size of the primary particles 11 can be controlled. Specifically, the faster the temperature rise rate is, or the lower the heat treatment temperature of the intermediate is, the more the average particle size of the primary particles 11 can be increased. -The average particle size of the primary particles 11 can also be controlled by adjusting at least one of the amount of Li (for example, Li ₂ CO ₃ ) and the amount of sintering aid (for example, boric acid, bismuth oxide) during calcination. Specifically, the greater the amount of Li or the greater the amount of sintering aid, the more the average particle size of the primary particles 11 can be increased. - By adjusting the setting conditions during calcination, the density of the aligned positive electrode plate 16 can be controlled. Specifically, the higher the calcination temperature or the longer the calcination time, the more the density of the aligned positive electrode plate 16 can be increased. [Example]

The present invention is explained more specifically by the following examples.

example 1 (1) Production of lithium secondary batteries A lithium secondary battery 10 in the form of a film-covered battery schematically shown in FIG. 1 is produced according to the procedures shown in FIGS. 2A and 2B. The details are as follows.

First, a LiCoO ₂ sintered body plate (hereinafter referred to as an LCO sintered body plate) with a thickness of 90 μm was prepared. The LCO sintered body plate is produced according to the aforementioned manufacturing method of the lithium composite oxide sintered body plate and satisfies the ideal conditions of the aforementioned lithium composite oxide sintered body plate. The sintered body plate was cut into a square shape of 10.5 mm×9.5 mm using a laser processing machine to obtain a plurality of wafer-shaped positive electrode plates 16 .

Two sheets of aluminum laminated film (manufactured by Showa Denko Packaging, thickness 61 μm, three-layer structure of polypropylene film/aluminum foil/nylon film) were prepared as the exterior film 26 . As shown in FIG. 2A , a plurality of wafer-shaped positive electrode plates 16 are laminated on one outer film 26 with a positive electrode current collector 14 (aluminum foil with a thickness of 9 μm) interposed therebetween to form a positive electrode assembly 17 . Although FIG. 2A shows a plurality of wafer-shaped positive electrode plates 16 , the present invention is not limited thereto. The positive electrode assembly 17 may also be formed using one positive electrode plate 16 that is not divided into wafer shapes. At this time, the positive electrode current collector 14 is fixed to the exterior film 26 with an adhesive. In addition, the positive electrode terminal 15 is fixed to the positive electrode current collector 14 by welding in a form extending from the positive electrode current collector 14 . On the other hand, the negative electrode layer 20 (carbon layer with a thickness of 130 μm) was laminated on the other exterior film 26 with the negative electrode current collector 22 (copper foil with a thickness of 10 μm) interposed therebetween, thereby forming a negative electrode assembly 19 . At this time, the negative electrode current collector 22 is fixed to the exterior film 26 with an adhesive. In addition, the negative electrode terminal 23 is fixed to the negative electrode current collector 22 by welding in a form extending from the negative electrode current collector 22 . The carbon layer of the negative electrode layer 20 is a coating film containing a mixture of graphite as an active material and polyvinylidene fluoride (PVDF) as a binder.

A porous polypropylene membrane (manufactured by Polypore, thickness 25 μm, porosity 55%) was prepared as the separator 18 . As shown in FIG. 2A , the positive electrode assembly 17 , the separator 18 and the negative electrode assembly 19 are stacked in this order so that the positive electrode plate 16 and the negative electrode layer 20 face the separator 18 , so that both sides are covered with the outer film 26 and the outer film 26 is covered with the outer film 26 . The laminated body 28 has an outer peripheral portion 26 protruding from the outer edge of the battery element 12 . In this way, the thickness of the battery element 12 (positive electrode current collector 14, positive electrode plate 16, separator 18, negative electrode layer 20 and negative electrode current collector 22) constructed in the laminate 28 is 0.33 mm, and its shape and size are 2.3 mm. cm×3.2cm square shape.

As shown in FIG. 2A , three sides A of the obtained laminate 28 are sealed. This sealing is performed by heating and pressing the outer peripheral portion of the laminated body 28 for 15 seconds at 200° C. and 1.5 MPa using a jig (heating rod) adjusted so that the sealing width becomes 2.0 mm. This is carried out by thermally welding the exterior films 26 (aluminum laminated films) to each other. After sealing side A, the laminated body 28 is placed in a vacuum dryer 34 to remove moisture and dry the adhesive.

As shown in FIG. 2B , in the glove box 38 , the remaining unsealed side B of the laminated body 28 that has been sealed on the outer edge 3 sides A forms a gap between a pair of exterior films 26 , and an injection device is inserted into the gap. 36 and inject electrolyte 24, and use a simple sealing machine to temporarily seal edge B under a reduced pressure environment with an absolute pressure of 5kPa. The electrolyte is used in a mixed solvent containing ethyl carbonate (EC) and methyl ethyl carbonate (MEC) at a ratio of 3:7 (volume ratio), LiPF ₆ is dissolved at a concentration of 1.0 mol/L, and further Vinyl carbonate (VC) is dissolved at a concentration of 2% by weight. The laminate whose side B was temporarily sealed was initially charged and aged for 7 days. Finally, cut off the outer peripheral part of the remaining side B of the seal (the end part excluding the battery element) and perform degassing.

As shown in FIG. 2B , in the glove box 38, the edge B' produced by the temporary sealing cutout is sealed in a reduced pressure environment with an absolute pressure of 5 kPa. This sealing is also performed by heat-pressing the outer peripheral portion of the laminated body 28 under conditions of 200° C. and 1.5 MPa for 15 seconds to thermally fuse the exterior films 26 (aluminum laminated films) to each other in the outer peripheral portion. In this way, the side B' is sealed with a pair of exterior films 26 to form a lithium secondary battery 10 in the form of a film exterior battery. The lithium secondary battery 10 is taken out of the glove box 38 , and the excess portion of the outer periphery of the exterior film 26 is cut off to adjust the shape of the lithium secondary battery 10 . In this way, the lithium secondary battery 10 in which the four outer edges of the battery element 12 are sealed with a pair of exterior films 26 and in which the electrolyte 24 is injected is obtained. The obtained lithium secondary battery 10 had a rectangular shape of 38 mm×27 mm, a thickness of 0.45 mm or less, and a capacity of 30 mAh.

(2)Evaluation The following evaluation was performed on the produced lithium secondary battery.

<Separation distance D between the end of the positive electrode plate and the end of the negative electrode layer> The separation distance D between the end of the positive electrode plate and the end of the negative electrode layer was measured as follows. First, an X-ray transmission photograph of a lithium secondary battery was taken from the positive electrode side under the following conditions: - Measurement device: Three-dimensional measurement X-ray CT device (TDM1300-IW/TDM1000-IW switching type, manufactured by Yamato Scientific Co., Ltd.) - Measurement Mode: Microfocus X-ray transmission observation (DR method) -Tube voltage: 70kV -Tube current: 60μA -Use Al filter (1mm) -Irradiation time: 134 seconds. According to the X-ray transmission photograph method, the outer film 26 and the positive electrode current collector 14 (aluminum foil) are penetrated by X-rays, so the contrast between the positive electrode plate 16 and the negative electrode current collector 22 (copper foil) can be observed. The area of the negative electrode current collector 22 (copper foil) is equal to the area of the negative electrode layer 20. Therefore, based on the contrast between the positive electrode plate 16 and the negative electrode current collector 22 (copper foil), the end of the positive electrode plate 16 and the negative electrode layer 20 can be measured. The separation distance D between the ends. Specifically, for each of the four sides of the lithium secondary battery 10, three separations from the end of the positive electrode plate 16 (the positive electrode plate as a whole composed of a plurality of wafer-shaped positive electrode plates) to the end of the negative electrode layer 20 were measured. distance, find the average of the separation distances D ₁ , D ₂ , D ₃ and D ₄ of each of the four sides. The minimum value among D ₁ to D ₄ is used as a representative value of the separation distance D between the end of the positive electrode plate 16 and the end of the negative electrode layer 20 in the lithium secondary battery 10 and is shown in Table 1.

＜Repeated bending test＞ The obtained thin-film exterior battery was embedded in epoxy resin, and a rectangular battery-built-in card with a thickness of 0.76 mm and a size of 86 mm × 54 mm was produced. For this card with a built-in battery, a bending test was conducted in accordance with JIS X 6305-1. Specifically, the card was placed in the card holder of the bending tester, and the card was bent 250 times to make the surface convex in the long side direction, and 250 times to make the surface convex in the short side direction. A bending test of 1,000 times in total with the back surface convexly bent 250 times and the back surface convexly bent 250 times in the short side direction. Thereafter, the surface profile of the battery-embedded portion of the card was measured using a surface roughness meter (Talysurf, manufactured by TAYLOR HOBSON). That is, by repeating the bending test, convex portions of varying degrees are generated on the exterior film near the battery-embedded portion of the card, and the height of the convex portions is measured. Specifically, as schematically shown in FIG. 6 , in the obtained surface profile, the peak corresponding to the convex portion is identified, the baseline BL of the peak is drawn, and the vertical direction from the baseline BL to the peak PT is measured. The distance is defined as the height H of the convex portion, and the presence or absence of wrinkles is determined based on the following criteria. The results are shown in Table 1. ‐No wrinkles: The height H of the convex part is less than 40 μm ‐Wrinkles: The height H of the convex portion is 40 μm or more

Example 2 The battery was produced and evaluated in the same manner as in Example 1, except that the thickness of the positive electrode plate 16 was set to 70 μm and the thickness of the negative electrode layer 20 was set to 80 μm. The results are shown in Table 1.

Example 3 The battery was produced and evaluated in the same manner as in Example 1, except that the thickness of the positive electrode plate 16 was set to 120 μm and the thickness of the negative electrode layer 20 was set to 160 μm. The results are shown in Table 1.

Example 4 The battery was produced and evaluated in the same manner as in Example 1, except that the size of the negative electrode layer 20 was slightly reduced so that the separation distance D between the ends of the positive electrode plate 16 and the negative electrode layer 20 was changed to 200 μm. The results are shown in Table 1.

Example 5 (comparison) The battery was produced and evaluated in the same manner as in Example 1, except that the size of the negative electrode layer 20 was further reduced so that the separation distance D between the ends of the positive electrode plate 16 and the negative electrode layer 20 was changed to 30 μm. The results are shown in Table 1.

Example 6 (comparison) A battery was produced and evaluated in the same manner as in Example 1, except that the thickness of the positive electrode plate 16 was set to 130 μm and the thickness of the negative electrode layer 20 was set to 150 μm. The results are shown in Table 1.

Example 7 1) Set the thickness of the positive electrode plate 16 to 80 μm, and set the thickness of the negative electrode layer 20 to 90 μm, and 2) further reduce the size of the negative electrode layer 20 so that the end of the positive electrode plate 16 and the end of the negative electrode layer 20 are The battery was produced and evaluated in the same manner as in Example 1 except that the separation distance D was changed to 50 μm. The results are shown in Table 1.

[Table 1] *Indicates comparative example.

10‧‧‧Lithium secondary battery 11‧‧‧primary particles 12‧‧‧Battery elements 14‧‧‧Positive current collector 15‧‧‧Positive terminal 16‧‧‧Positive plate 17‧‧‧Anode assembly 18‧‧‧Dividers 19‧‧‧Anode assembly 20‧‧‧Anode layer 22‧‧‧Negative current collector 23‧‧‧Negative terminal 24‧‧‧Electrolyte 26‧‧‧Exterior film 28‧‧‧Laminated body 34‧‧‧Vacuum dryer 36‧‧‧Injection equipment 38‧‧‧Glove box 40‧‧‧Charger D‧‧‧The separation distance between the end of the positive electrode plate and the end of the negative electrode layer A‧‧‧side B‧‧‧side B’‧‧‧side BL‧‧‧baseline PT‧‧‧peak H‧‧‧The height of the convex part

[Fig. 1] is a schematic cross-sectional view of an example of the lithium secondary battery of the present invention. [Fig. 2A] is a diagram showing the first half of an example of the manufacturing steps of a lithium secondary battery. [FIG. 2B] is the second half of an example of the manufacturing process of a lithium secondary battery, and is a diagram showing the steps after the step shown in FIG. 2A. The right end of Figure 2B includes a photo of a film-encased battery. [Fig. 3] is an SEM image showing an example of a cross section of an aligned positive electrode plate perpendicular to the plate surface. [Fig. 4] An EBSD image of the cross section of the aligned positive plate shown in Fig. 3. [Fig. 5] A histogram showing the alignment angle distribution of primary particles in the EBSD image of Fig. 4 on an area basis. [Fig. 6] is a schematic diagram illustrating the surface profile of the height H of the convex portion produced on the surface of the card due to repeated bending tests.

Claims (13)

A lithium secondary battery having: The positive plate is a lithium composite oxide sintered body plate; The negative electrode layer has a size larger than the size of the positive electrode plate and contains carbon; A separator is interposed between the positive electrode plate and the negative electrode layer, and the size is larger than the size of the positive electrode plate and the negative electrode layer; Electrolyte, impregnated in the positive electrode plate, the negative electrode layer, and the separator; and 1 pair of exterior films, the outer peripheries of which are sealed to each other to form an internal space, and the internal space accommodates the positive plate, the negative layer, the separator, and the electrolyte, The outer peripheral part of the separator is at least in close contact with the outer peripheral edge of the outer casing film on the side of the positive electrode plate or the surrounding area near it, and isolates the block containing the positive electrode from the block containing the negative electrode, The thickness of the lithium secondary battery is 350-500 μm, the thickness of the positive electrode plate is 70-120 μm, and the separation distance between the end of the positive electrode plate and the end of the negative electrode layer is on the entire outer periphery of the positive electrode plate and the negative electrode layer. 50～2000μm. For example, the lithium secondary battery described in item 1 of the patent application is a thin secondary battery that can be built into a card. For example, the lithium secondary battery in the first or second patent scope of the application, wherein the thickness of the lithium secondary battery is 380 to 450 μm. For example, in the lithium secondary battery of item 1 or 2 of the patent application, the thickness of the positive plate is 80 to 100 μm. For example, in the lithium secondary battery of claim 1 or 2, the separation distance between the end of the positive electrode plate and the end of the negative electrode layer is 200 to 1500 μm over the entire periphery of the positive electrode plate and the negative electrode layer. For example, in the lithium secondary battery of item 1 or 2 of the patent application, the thickness of the negative electrode layer is 70 to 160 μm. For example, for the lithium secondary battery in the first or second patent scope, the thickness of the outer film is 50 to 80 μm per piece. For example, in the lithium secondary battery of claim 1 or 2, the exterior film is a laminate film composed of a resin film and a metal foil. For example, in the lithium secondary battery of claim 1 or 2, the separator is made of polyolefin, polyimide, or cellulose. For example, in the lithium secondary battery of item 1 or 2 of the patent application, the lithium composite oxide is lithium cobalt oxide. For example, the lithium secondary battery of claim 1 or 2, wherein the lithium composite oxide sintered body plate contains a plurality of primary particles composed of a lithium composite oxide, and the plurality of primary particles are relative to the positive electrode. An aligned positive plate whose surface is aligned with an average alignment angle exceeding 0° and below 30°. For example, the lithium secondary battery in item 1 or 2 of the patent scope further includes a positive electrode current collector and a negative electrode current collector. A card with a built-in battery that has: resin substrate; and A lithium secondary battery according to any one of items 1 to 12 of the patent application embedded in the resin substrate.