JP2015095285A - Square lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a square lithium ion secondary battery capable of reducing local difference in pressure applied to flat parts of a wound electrode group even when a wide face of a battery can gets concaved due to a pressure difference between inner side and outer side of a battery container.SOLUTION: The square lithium ion secondary battery includes: a wound electrode group 3 which is formed by winding in a flat-shape having two flat parts; and a battery container storing the wound electrode group, which has wide faces 1b each facing to the respective flat parts of the wound electrode group. The square lithium ion secondary battery has wide faces each of which is curved protruding inward of the battery container and a compression member 4 is provided between the flat part and the inner wall of the wide face. The compression member 4 is formed on one plane facing to the inner wall of the wide face having a concave part facing to the curved protruding part of the wide face. The rear side of the plane formed with the concave part 4b of the compression member is flat, and which faces to the flat part 3a of the wound electrode group.

Description

  The present invention relates to a prismatic lithium ion secondary battery.

  Since lithium ion secondary batteries have a higher energy density compared to other secondary batteries, they are now mainly used in portable devices such as digital cameras, notebook computers, and mobile phones. In recent years, research and development of large-sized lithium ion secondary batteries for the purpose of electric vehicles and power storage have been actively conducted in order to cope with environmental problems. In particular, in the automobile industry, the development of electric vehicles using a motor as a power source and hybrid electric vehicles using both an internal combustion engine and a motor are underway, some of which have already been put into practical use. Yes.

  In a lithium ion secondary battery, a prismatic battery comprising a wound electrode group formed by winding a strip-like positive electrode and a negative electrode over a separator and containing an electrolyte, that is, a prismatic lithium ion secondary battery, has been known. It has been. As a prismatic lithium-ion secondary battery for in-vehicle use that mainly requires high output, the uncoated parts of the positive electrode and negative electrode are projected at both ends in the winding axis direction of the wound electrode group, and are not projected. By connecting the coating part to the current collector, a simple configuration is possible, and the current path to the electrode terminal and current collector is shortened, and the connection resistance is reduced to achieve high output. Various things have been proposed.

  In such a rectangular lithium ion secondary battery, it has been found that it is important in terms of performance to press the wound electrode group over the entire surface in the thickness direction. On the basis of this knowledge, Patent Document 1 is provided with a film member having a thick portion formed between the wound electrode group and the inner wall of the battery can for the purpose of applying a load to the wound electrode group. A battery invention is disclosed. The thick portion is located at a boundary portion between the flat portion and the curved portion in the surface of the wound electrode group. Thereby, it has a structure in which the load when the secondary battery is restrained is widely applied to the flat portion of the wound electrode group.

  In a prismatic lithium ion secondary battery, the inside of the battery can is depressurized in order to promote the penetration of the electrolytic solution into the wound electrode group mainly in the liquid injection process. Thereafter, the liquid inlet is sealed and sealed. Due to the liquid injection process, the sealed battery can is in a negative pressure state, and the battery can is recessed from the center of the battery can to the outer edge due to a pressure difference between the inside and outside of the battery can. And the dent is recessed toward the center.

Japanese Patent No. 4998451

  In the film member described in Patent Document 1, since only the thickness portion is formed at the boundary between the curved portion and the flat portion of the wound electrode group, when the above-described dent occurs, the wound electrode group is applied. The pressure varies depending on where it is applied. As a result, the battery performance is not fully exhibited.

  The prismatic lithium ion secondary battery according to claim 1 is wound into a flat shape, accommodates a wound electrode group having two flat portions, a wound electrode group, and faces the flat portion of the wound electrode group. A wide surface, in a prismatic lithium ion secondary battery that is convexly curved toward the inside of the battery container, the wide surface is between the flat portion and the inner wall of the wide surface. The concave portion facing the curved convex portion has a compression member formed on one surface facing the inner wall of the wide surface, and the back surface of the surface on which the concave portion of the compression member is formed is flat, and It is characterized by facing the flat part of the wound electrode group.

  In this invention, when the center part of the wide surface of a battery can is dented by the pressure difference inside and outside a battery case, the difference by the place of the pressure which the winding electrode group receives from a wide surface can be made small.

The external appearance perspective view of a square lithium ion secondary battery. The disassembled perspective view of a square lithium ion secondary battery. The perspective view of a wound electrode group. The figure which shows a mode that the wide surface of the battery can was dented. The figure which shows the compression member in 1st Embodiment. The figure which compares this invention with a prior art. The figure which shows the compression member in 2nd Embodiment. The figure which shows the compression member in 3rd Embodiment.

-First embodiment-
FIG. 1 is a perspective view showing an external appearance of a prismatic lithium ion secondary battery 100, and FIG. 2 is an exploded perspective view showing an internal configuration of the prismatic lithium ion secondary battery 100 of FIG.

  As shown in FIGS. 1 and 2, the prismatic lithium ion secondary battery 100 has a flat rectangular parallelepiped shape, and includes a battery container including a battery can 1 and a battery lid 6. The material of the battery can 1 and the battery lid 6 is aluminum or an aluminum alloy.

  As shown in FIG. 2, the wound electrode group 3 is accommodated in the battery can 1. The battery can 1 has a pair of wide surfaces 1b, a pair of narrow surfaces 1c, and a bottom surface 1d, and is formed in a bottomed box shape having one end opened as an opening 1a. The wound electrode group 3 is accommodated in the battery can 1 while being covered with the insulating protective film 2. The material of the insulating protective film 2 is an insulating resin such as polypropylene or polyethylene terephthalate. Thereby, the wound electrode group 3 and the wide surface 1b, the narrow surface 1c, and the bottom surface 1d of the battery can 1 are electrically insulated.

  As shown in FIGS. 1 and 2, the battery lid 6 has a rectangular flat plate shape and is laser-welded so as to close the opening 1 a of the battery can 1. That is, the battery lid 6 seals the opening 1 a of the battery can 1. The battery lid 6 is provided with a positive external terminal 14 and a negative external terminal 12.

  The positive electrode external terminal 14 is electrically connected to the positive electrode uncoated portion 34 c of the wound electrode group 3 via the positive electrode current collector 44, and the negative electrode external terminal 12 is connected to the wound electrode group 3 via the negative electrode current collector 24. The negative electrode uncoated portion 32c is electrically connected. Thereby, electric power is supplied to the external load through the positive external terminal 14 and the negative external terminal 12, or external generated power is supplied to the wound electrode group 3 through the positive external terminal 14 and the negative external terminal 12. Charged.

As shown in FIG. 2, the battery lid 6 is provided with a liquid injection port 9 for injecting an electrolytic solution into the battery container. The liquid injection port 9 is sealed with a liquid injection stopper 11 after the electrolytic solution is injected. As the electrolytic solution, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.

  As shown in FIG. 1, a gas discharge valve 10 is recessed on the surface of the battery lid 6. The gas discharge valve 10 is formed by partially thinning the battery lid 6 by press work so that the degree of stress concentration at the time of internal pressure action is relatively high. The gas discharge valve 10 is heated when the prismatic lithium ion secondary battery 100 generates heat due to an abnormality such as overcharge and the like, and when the pressure in the battery container rises and reaches a predetermined pressure, the gas discharge valve 10 is split from the inside. The pressure in the battery container is reduced by discharging the gas.

  As shown in FIG. 2, the positive electrode external terminal 14, the negative electrode external terminal 12, the positive electrode current collector 44, and the negative electrode current collector 24 are attached to the battery lid 6. A gasket 5 is disposed between each of the positive external terminal 14 and the negative external terminal 12 and the battery cover 6. Thereby, each of the positive electrode external terminal 14 and the negative electrode external terminal 12 is electrically insulated from the battery cover 6. An insulating plate 7 is disposed between each of the positive electrode current collector base 41 of the positive electrode current collector 44 and the negative electrode current collector base 21 of the negative electrode current collector 24 and the battery lid 6. Thereby, each of the positive electrode current collector 44 and the negative electrode current collector 24 is electrically insulated from the battery lid 6. The material of the gasket 5 and the insulating plate 7 is a resin having insulation properties such as polybutylene terephthalate, polyphenylene sulfide, perfluoroalkoxy fluororesin.

  The material of the positive electrode external terminal 14 and the positive electrode current collector 44 is an aluminum metal, that is, aluminum or an aluminum alloy. The positive electrode external terminal 14 has a rectangular parallelepiped external terminal portion and a protrusion protruding from the surface of the external terminal portion on the battery lid 6 side toward the battery lid 6 side. The protrusion is inserted into the through hole of the gasket 5, the positive electrode side through hole 46 of the battery lid 6, the through hole of the insulating plate 7, and the positive electrode side opening hole 43 of the positive electrode current collector base 41 of the positive electrode current collector 44. The tip is caulked to the positive electrode current collector base 41 of the positive electrode current collector 44 in the battery container to form the positive electrode connection portion 14a. The positive electrode connecting portion 14a and the positive electrode current collector base 41 are caulked and fixed, and then spot welded by a laser. Thereby, the positive electrode external terminal 14 and the positive electrode current collector 44 are electrically connected, and each of the positive electrode external terminal 14 and the positive electrode current collector 44 is fixed to the battery lid 6.

  The material of the negative electrode external terminal 12 and the negative electrode current collector 24 is a copper-based metal, that is, copper or a copper alloy. The negative electrode external terminal 12 has a rectangular parallelepiped external terminal portion and a protrusion protruding from the surface of the external terminal portion on the battery lid 6 side toward the battery lid 6 side. The protrusion is inserted into the through hole of the gasket 5, the negative electrode side through hole 26 of the battery lid 6, the through hole of the insulating plate 7, and the negative electrode side opening hole 23 of the negative electrode current collector base 21 of the negative electrode current collector 24. The tip is caulked to the negative electrode current collector base 21 of the negative electrode current collector 24 in the battery container to form the negative electrode connection portion 12a. The negative electrode connection portion 12a and the negative electrode current collector base portion 21 are fixed by caulking and then spot welded by a laser. Thereby, the negative electrode external terminal 12 and the negative electrode current collector 24 are electrically connected, and each of the negative electrode external terminal 12 and the negative electrode current collector 24 is fixed to the battery lid 6.

  As shown in FIG. 2, the positive electrode current collector 44 includes a rectangular flat plate-shaped positive electrode current collector base 41 arranged along the inner surface of the battery lid 6, and substantially from the long side of the positive electrode current collector base 41. A positive electrode side flat plate portion 47 that is bent at a right angle and extends toward the bottom surface 1 d of the battery can 1 along the wide surface 1 b of the battery can 1, and a positive electrode side connecting portion 48 provided at the lower end of the positive electrode side flat plate portion 47. And a positive electrode side connection end 42 to be connected. The positive electrode side connection end portion 42 is a portion that is ultrasonically welded to the positive electrode uncoated portion 34 c of the wound electrode group 3.

  Similarly, the negative electrode current collector 24 is bent at a substantially right angle from a rectangular flat plate-shaped negative electrode current collector base portion 21 disposed along the inner surface of the battery lid 6 and a long side of the negative electrode current collector base portion 21. The negative electrode side flat plate portion 37 extending toward the bottom surface 1 d of the battery can 1 along the wide surface 1 b of the battery can 1 and the negative electrode connected by the negative electrode side connecting portion 38 provided at the lower end of the negative electrode side flat plate portion 37. Side connection end 22. The negative electrode side connection end portion 22 is a portion that is ultrasonically welded to the negative electrode uncoated portion 32 c of the wound electrode group 3.

  As described above, the wound electrode group 3 is accommodated in the battery can 1 while being covered with the insulating protective film 2. A compression member 4 is provided between the wound electrode group 3 covered with the insulating protective film 2 and the inner surface of the wide surface 1b of the battery container. Since the flat part 3a of the wound electrode group 3 has a front side and a back side, and each flat part 3a faces the wide surface 1b, there are two places between the wound electrode group 3 and the wide surface 1b. A compression member 4 is provided on the surface. That is, the wound electrode group 3 covered with the insulating protective film 2 is accommodated in the battery can 1 so as to be sandwiched between the two compression members 4. In addition, the compression member 4 is further demonstrated in the description location of FIGS. 4-6 mentioned later.

  FIG. 3 is a perspective view showing a state where the winding end side of the wound electrode group 3 is developed. The wound electrode group 3 has two flat portions 3a and two curved portions 3b.

  The wound electrode group 3 is configured by winding in a flat shape via a separator 33 between the negative electrode 32 and the positive electrode 34. As the shaft core for winding, one formed by winding a resin sheet having higher bending rigidity than any of the positive electrode foil 34a, the negative electrode foil 32a, and the separator 33 can be used. In the wound electrode group 3, the outermost electrode is the negative electrode 32, and the separator 33 is wound outside thereof. The separator 33 has a role of insulating between the positive electrode 34 and the negative electrode 32. The positive electrode uncoated portion 34c and the negative electrode uncoated portion 32c are regions where the metal surface of the electrode foil is exposed. In the wound electrode group 3, the positive electrode uncoated portion 34 c is arranged on one side in the winding axis direction, and the negative electrode uncoated portion 32 c is wound on the other side in the winding axis direction. Is done.

In order to produce the positive electrode 34, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of polyfluoride as a binder with respect to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. A positive electrode mixture was prepared by adding vinylidene (hereinafter referred to as PVDF), adding N-methylpyrrolidone (hereinafter referred to as NMP) as a dispersion solvent, and kneading. The positive electrode mixture was applied to both surfaces of a positive electrode foil 34a made of an aluminum foil having a thickness of 20 μm to provide a positive electrode mixture coating portion 34b. In that case, the positive electrode uncoated part 34c was provided in both surfaces of the one end part of the width direction of the positive electrode foil 34a by not coating a positive electrode mixture. Then, the positive electrode 34 was obtained through the drying, the press, and the cutting process. In addition, the thickness of the positive electrode mixture coating part 34b which deducted the thickness of the positive electrode foil 34a was 90 micrometers.

  In order to produce the negative electrode 32, 10 parts by weight of PVDF as a binder was added to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and NMP was added and kneaded as a dispersion solvent thereto. A mixture was prepared. This negative electrode mixture was applied to both surfaces of a negative electrode foil 32a made of a copper foil having a thickness of 10 μm to provide a negative electrode mixture coating portion 32b. In that case, the negative electrode uncoated part 32c was provided in both surfaces of the one end part of the width direction of the negative electrode foil 32a by not coating a negative electrode mixture. Then, the negative electrode 32 was obtained through the drying, the press, and the cutting process. In addition, the thickness of the negative electrode mixture coating part 32b which deducted the thickness of the negative electrode foil 32a was 70 micrometers.

  The negative electrode mixture coating portion 32b is larger in the width direction than the positive electrode mixture coating portion 34b, and the positive electrode mixture coating portion 34b extends from the negative electrode mixture coating portion 32b in the winding axis direction in the wound electrode group 3. It is arranged so as not to protrude. The positive electrode uncoated portion 34c and the negative electrode uncoated portion 32c are respectively bundled and connected to the positive electrode current collector 44 and the negative electrode current collector 24 by welding. The separator 33 is larger in the width direction than the negative electrode mixture coating portion 32b. However, since the positive electrode uncoated portion 34c and the negative electrode uncoated portion 32c in the wound electrode group 3 are disposed so as to protrude outward in the winding axis direction from the separator 33, the separator 33 is not coated with the positive electrode. It does not become a hindrance when 34c and the negative electrode uncoated part 32c are welded.

  FIG. 4 shows a state in which the wide surface 1b of the battery can 1 is recessed due to a pressure difference between the inside and outside of the battery container. FIG. 4A is a perspective view of the battery case, and schematically shows a state where the center portion of the wide surface 1b is recessed with a dotted line. FIG. 4B is a view of the battery container as viewed from the narrow surface 1c side. A line 50a indicates an outer edge of the wide surface 1b on the narrow surface 1c side. A line 50b is a line on the wide surface 1b as viewed from the narrow surface 1c side, which is a line passing through the center in the vertical direction in the figure. That is, the line 50b represents the outer shape of the wide surface 1b at the center in the left-right direction in FIG. FIG.4 (c) is the figure which looked at the battery container from the bottom face 1d side. A line 51a indicates an outer edge of the wide surface 1b on the bottom surface 1d side. A line 51b is a line on the wide surface 1b as viewed from the bottom surface 1d side, which is a line 61 passing through the center in the horizontal direction in the figure. That is, the line 51b represents the outer shape of the wide surface 1b at the center in the vertical direction in FIG.

  As can be seen from the line 50a shown in FIG. 4B and the line 51a shown in FIG. 4C, the outer edge of the wide surface 1b is hardly deformed. On the other hand, as can be seen from the line 50b shown in FIG. 4 (b) and the line 51b shown in FIG. 4 (c), it can be seen that the central portion of the wide surface 1b is deformed, that is, recessed, toward the inside. Furthermore, it turns out that the depth of a dent becomes small as it goes to an outer edge.

  FIG. 5 is a perspective view of the compression member 4. The pressing member 4 has a flat portion 4 a on the surface facing the flat portion 3 a of the wound electrode group 3. On the other hand, on the surface opposite to the wide surface 1b of the battery can 1, which is the back surface, there is a recess 4b whose depth increases from the outer edge toward the center.

  The compression member 4 can be manufactured, for example, by injection molding in which a molten resin is poured into a mold and cured. For the compression member 4, for example, a synthetic resin such as PP (polypropylene), polyimide, polybutylene terephthalate, or the like can be used as a material. Polyimide is preferable from the viewpoint of strength, and polypropylene is preferable from the viewpoint of workability.

  FIG. 6A shows a cross section passing through the central portion of the recessed wide surface 1b in the prismatic lithium ion secondary battery 100 of the first embodiment of the present invention, for example, a cross section including the line 61 shown in FIG. Sectional drawing is shown. FIG. 6B is a cross-sectional view of a conventional prismatic lithium ion secondary battery passing through the central portion of the recessed wide surface 1b, for example, a cross-section including the line 61 shown in FIG. Yes. In any of the figures, the insulating protective film 2 covering the wound electrode group 3 is not shown. Moreover, in this specification, the insulation protective film 2 does not have the rigidity which can disperse | distribute the pressure from the wide surface 1b. Furthermore, in this embodiment, the compression member 4 is arrange | positioned on the outer side of the insulation protective film 2 (refer the description location of FIG. 2).

The prismatic lithium ion secondary battery 100 of the first embodiment is different from the conventional prismatic lithium ion secondary battery in that the pressing member 4 is provided.
In FIG. 6A, the wound electrode group 3 covered with the insulating protective film 2 (not shown) is accommodated in the battery can 1 so as to be sandwiched between the pair of compression members 4. At that time, the flat portion 4a of the compression member 4 is opposed to the flat portion 3a of the wound electrode group via the insulating protective film 2 (not shown). Further, the recess 4 b of the compression member 4 faces the inner wall of the wide surface 1 b of the battery can 1. The wide surface 1b is recessed toward the center, but the pressure applied to the compression member 4 from the wide surface 1b is dispersed because the concave portion of the compression member 4 has a shape along the depression. Further, the flat portion 4a of the compression member 4 is subjected to the pressure that the flat portion 3a of the wound electrode group 3 receives the dispersed pressure and the difference depending on the location is reduced.

  On the other hand, in FIG. 6B, the flat portion 3 a of the wound electrode group 3 covered with the insulating protective film 2 (not shown) is opposed to the wide surface 1 b without the insulating protective film 2 interposed therebetween. Therefore, since the concave wide surface 1b concentrates and abuts near the center of the flat portion 3a, the pressure of the wound electrode group 3 is not dispersed from the wide surface 1b.

  The thickness at the center of the compression member 4, that is, the distance between the recess 4 b and the flat portion 4 a at the center of the compression member 4 is the thickness at the outer edge of the compression member 4, that is, the recess at the outer edge of the compression member 4. The distance is preferably in the range of about 0.4 to 0.8 times the distance between 4b and the flat portion 4a. By setting the thickness at the center of the compression member 4 within this range, it is possible to make the shape along the recess of the wide surface 1b of the battery can 1.

  The thickness at the outer edge of the compression member 4, that is, the distance between the concave portion 4 b and the flat portion 4 a at the outer edge of the compression member 4 is the thickness between the flat portions 3 a of the wound electrode group 3, that is, the thickness of the wound electrode group 3. The range is preferably about 0.01 to 0.2 times the distance between the flat portions 3a. When the thickness at the outer edge of the compression member 4 is too thick outside this range, the ratio of the compression member 4 to the battery volume increases, and the capacity per volume and the output decrease. If the thickness at the outer edge of the compression member 4 is too thin outside this range, the depth of the recess 4b cannot be increased. Moreover, the strength of the compression member 4 also decreases.

As described above, according to the prismatic lithium ion secondary battery 100 of the first embodiment, the following operational effects can be obtained.
(1) The prismatic lithium ion secondary battery 100 according to the first embodiment is wound in a flat shape, accommodates the wound electrode group 3 having two flat portions 3a and the wound electrode group 3, and is wound. And a battery container having a wide surface 1b facing the flat portion 3a of the electrode group 3. The wide surface 1b of the battery container is convexly curved toward the inside of the battery container. Between the flat part 3a of the wound electrode group 3 and the inner wall of the wide surface 1b, a recess 4b is formed so that the pressure due to the pressing of the wide surface 1b reduces the difference in location in the flat part 3a of the wound electrode group 3. Is provided with a compression member 4 formed on one surface. The back surface of the surface on which the concave portion 4b is formed is a flat portion 4a, the concave portion 4b is opposed to the inner wall of the wide surface 1b, and the flat portion 4a is opposed to the flat portion 3a of the wound electrode group 3.
Thereby, when the wide surface 1b of the battery container is recessed due to a pressure difference between the inside and outside of the battery container, the pressure applied to the compression member 4 from the wide surface 1b can be dispersed by the recess 4b of the compression member 4, and the dispersion In response to the applied pressure, the flat portion 4a of the compression member 4 can apply a pressure that reduces the difference depending on the location to the flat portion 3a of the wound electrode group 3.

(2) The depth of the recess 4b of the compression member 4 is continuously increased from the outer edge toward the center. Thereby, it can be made to follow the dent of the wide surface 1b.

-Second embodiment-
FIG. 7 is a view showing the compression member 4 in the second embodiment. Explanations similar to those in the first embodiment are omitted. The compression member 4 in the second embodiment is provided with a stepped recess 4b. In the present embodiment, the number of stages is one. Even such a compression member 4 can achieve the same effects as those of the first embodiment.

  Below, the example of preparation of the compression member 4 in 2nd Embodiment is described. By superimposing a plate having a through hole in the center on a substrate having a uniform thickness, the compression member 4 having a thickness that changes stepwise from the center to the outer edge, that is, having a stepped recess, is obtained. Can do.

  As the substrate and the plate having through holes, for example, a synthetic resin such as PP (polypropylene) or a material such as polyimide or polybutylene terephthalate can be used.

  In order to dent uniformly from the center part of the battery can 1 to the outer edge, the through hole is preferably located at the center part of the compression member. In addition, the opening area of the through hole is preferably in the range of 0.1 to 0.7 when the area of the substrate is 1, considering how the wide surface 1b of the battery can 1 is recessed. When the opening area of the through hole is larger than 0.7, the central part of the battery container cannot come into contact with the compression member 4. When the opening area of the through hole is smaller than 0.1, the outer edge portion of the compression member 4 and the battery container may not come into contact with each other. The shape of the through hole is preferably a quadrangular shape so as to follow the recess of the wide surface 1 b of the battery can 1. Other than the square, a round shape, a rhombus shape, or the like can be used as appropriate.

  In the present embodiment, the compression member 4 is manufactured from a plurality of parts (plates), but it can also be manufactured integrally by injection molding.

-Third embodiment-
FIG. 8 is a view showing the compression member 4 in the third embodiment. Explanations similar to those in the first embodiment are omitted. The compression member 4 in the third embodiment is provided with a stepped recess 4b. In the present embodiment, the number of stages is three as an example of a plurality of stages. Even such a compression member 4 can achieve the same effects as those of the first embodiment.

  Below, the example of preparation of the compression member 4 in 2nd Embodiment is described. A plurality of plates each having through-holes having different sizes are stacked on a substrate having no through-holes. By pressing the plate closer to the substrate so as to have a smaller through hole, the compression member 4 as shown in FIG. 8 can be manufactured.

  The number of steps of the recess 4b is desirably 3 to 5. Compared with the compression member 4 in the second embodiment, the manufacturing method of the compression member 4 in the third embodiment is complicated, but since the region in contact with the inner wall of the wide surface 1b of the battery can 1 increases, the wound electrode The difference of the force applied to the group 3 due to the location can be reduced. The same material as that of the second embodiment can be used for the material of the plate and the bonding method.

  In the present embodiment, the compression member 4 is manufactured from a plurality of parts (plates), but it can also be manufactured integrally by injection molding.

-Modification-
In addition, the following modifications may be made in the present invention.

  As a positive electrode active material, other lithium manganate having a spinel crystal structure, a lithium manganese composite oxide partially substituted or doped with a metal element, lithium cobaltate having a layered crystal structure, lithium titanate, and the like A lithium-metal composite oxide in which a part of the metal is substituted or doped with a metal element may be used.

As a negative electrode active material, natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbonaceous materials such as coke, and compounds such as Si and Sn (for example, SiO, TiSi _2, etc.) Or a composite material thereof. Also in the particle shape, there is no particular limitation such as a scale shape, a spherical shape, a fiber shape, or a lump shape.

  As a binder for the coating part in the positive electrode and the negative electrode, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes Polymers such as acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof can be used.

1: battery can, 1a: opening, 1b: wide surface, 1c: narrow surface, 1d: bottom surface,
2: insulation protective film, 3: wound electrode group, 3a: flat part, 3b: curved part,
4: compression member, 4a: flat part, 4b: recessed part, 5: gasket,
6: Battery cover, 7: Insulating plate, 9: Injection port, 10: Gas discharge valve, 11: Injection plug,
12: negative electrode external terminal, 12a: negative electrode connection part, 14: positive electrode external terminal,
14a: positive electrode connection part, 21: negative electrode current collector base part, 22: negative electrode side connection end part,
23: negative electrode side opening hole, 24: negative electrode current collector, 26: negative electrode side through hole, 32: negative electrode,
32a: negative electrode foil, 32b: negative electrode mixture coating part, 32c: negative electrode uncoated part,
33: Separator, 34: Positive electrode, 34a: Positive foil, 34b: Positive electrode mixture coating part,
34c: positive electrode uncoated part, 41: positive electrode current collector base part, 42: positive electrode side connection end part,
43: positive electrode side opening hole, 44: positive electrode current collector, 46: positive electrode side through hole,
100: Square lithium ion secondary battery

Claims (4)

A wound electrode group wound in a flat shape and having two flat portions;
A battery container that houses the wound electrode group and has a wide surface facing the flat portion of the wound electrode group;
In the prismatic lithium ion secondary battery in which the wide surface is convexly curved toward the inside of the battery container,
Between the flat portion and the inner wall of the wide surface, there is a compression member in which a recess facing the curved convex portion of the wide surface is formed on one surface facing the inner wall of the wide surface. And
A prismatic lithium ion secondary battery in which the back surface of the surface on which the concave portion of the compression member is formed is flat and faces the flat portion of the wound electrode group. The prismatic lithium ion secondary battery according to claim 1,
The concave portion is a prismatic lithium ion secondary battery formed in a step shape. The prismatic lithium ion secondary battery according to claim 2,
A square lithium ion secondary battery in which the number of steps of the recesses is one or more. The prismatic lithium ion secondary battery according to claim 1,
A prismatic lithium ion secondary battery in which the depth of the recess continuously increases from the outer edge of the compression member toward the center.

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