Battery and battery lid

Abstract

This invention shortens the time required for an electrolyte to infiltrate into a plurality of wound electrode bodies. All or some of one or more liquid injection holes provided in this battery lid are provided at positions overlapping a curved top part of any of the plurality of wound electrode bodies housed in a battery container in a top view of the battery lid.

Description

Battery and Battery Cover

[0001] The present invention generally relates to a battery and a battery cover.

[0002] As a battery such as a lithium ion battery, the battery disclosed in Patent Document 1 is known. In this battery, an electrolytic solution is injected through an injection hole into a battery case that accommodates a plurality of wound electrode bodies. The injection hole is sealed by a sealing member extending in the vertical direction.

[0003] Japanese Patent Application Laid-Open No. 2024-064659

[0004] In the battery disclosed in Patent Document 1, the injection hole is formed at a position overlapping a valley between the wound electrode bodies in a top view of the battery. With this arrangement, the distal end of the sealing member that seals the injection hole can extend close to the valley, which allows the vertical length of the wound electrode bodies to be increased, thereby increasing the capacity of the battery.

[0005] However, in this configuration, the electrolytic solution injected from the injection hole first reaches the valley between the wound electrode bodies, so it takes a long time for the electrolytic solution to infiltrate the entire wound electrode bodies (especially to the top portions thereof).

[0006] Each of the one or more injection ports provided on the battery cover is provided at a position overlapping the curved top of any one of the plurality of wound electrode bodies accommodated in the battery container in a top view of the battery cover.

[0007] The time required for the electrolytic solution to infiltrate the plurality of wound electrode bodies can be shortened.

[0008] Fig. 1 is a perspective view of the secondary battery according to Example 1. Fig. 1 is an exploded perspective view of the secondary battery of Fig. 1. Fig. 1 is a configuration diagram of a wound electrode body. Fig. 1 is a cross-sectional view taken along line IV-IV of Fig. 1. Fig. 1 is a top view of the secondary battery according to Example 1. Fig. 1 is a top view of a first secondary battery according to Example 2. Fig. 1 is a top view of a second secondary battery according to Example 2. Fig. 1 is a top view of a third secondary battery according to Example 2. Fig. 1 is a top view of a fourth secondary battery according to Example 2. Fig. 1 is a top view of a fifth secondary battery according to Example 2. Fig. 1 is a top view of a sixth secondary battery according to Example 2. Fig. 1 is a top view of a seventh secondary battery according to Example 2. Fig. 1 is a top view of an eighth secondary battery according to Example 2.

[0009] The following examples will be described with reference to the drawings. Figures 1 to 9 below are schematic diagrams. In the following examples, the battery is a rechargeable battery, but the present invention may also be applied to batteries other than rechargeable batteries.

[0010] Figure 1 is a perspective view of a secondary battery according to Example 1. Figure 2 is an exploded perspective view of the secondary battery shown in Figure 1.

[0011] The secondary battery 1 is a flattened, rectangular lithium-ion secondary battery, for example, that is installed as a power source in electric vehicles or hybrid vehicles. In the following, the configuration of each part of the secondary battery 1 may be described using an xyz Cartesian coordinate system, where the width direction of the secondary battery 1 is the x direction, the thickness direction is the y direction, and the height direction is the z direction. Also, the up, down, left, and right directions in the following description are convenient directions for describing the configuration of each part of the secondary battery 1 based on the drawings, and are not limited to the vertical or horizontal directions.

[0012] The secondary battery 1 comprises a battery case 2 that forms a sealed case and houses two wound electrode bodies 5, 5 (an example of multiple wound electrode bodies). The battery case 2 is, for example, a metal case having a flat rectangular box shape. The battery case 2 has a pair of wide sides 3A along the width direction (x direction), a pair of narrow sides 3B along the thickness direction (y direction), and an elongated rectangular top surface 3C and bottom surface 3D. Of these wide sides 3A, narrow sides 3B, top surface 3C and bottom surface 3D, the wide side 3A has the largest area.

[0013] The battery case 2 consists of, for example, a battery container 3 which is a flat rectangular box with one side open in the height direction (z direction), and a rectangular plate-shaped battery cover 4 which closes the opening 3E of the battery container 3. The battery container 3 and the battery cover 4 are made of a metal material such as an aluminum alloy and are formed by deep drawing or press working.

[0014] After the wound electrode bodies 5, 5 for storing electricity are loaded into the battery container 3 through the opening 3E, the perimeter of the battery cover 4 is joined to the battery container 3 around the entire circumference of the opening 3E by laser welding or the like. As a result, the opening 3E is sealed by the battery cover 4.

[0015] The battery cover 4 has through holes 4A drilled at both ends in the longitudinal direction, which is the width direction (x direction) of the secondary battery 1, through which a portion of the positive electrode external terminal 7 and the negative electrode external terminal 8, which will be described later, are inserted, and a gas discharge valve 4B is formed in the center in the longitudinal direction. The gas discharge valve 4B is, for example, a portion of the battery cover 4 that has been thinned by press processing and a slit has been formed, and is integrally formed with the battery cover 4. When the internal pressure of the battery case 2 rises to a predetermined pressure, the gas discharge valve 4B opens and the gas inside the battery case 2 is discharged to the outside of the container.

[0016] Furthermore, the battery cover 4 has an electrolyte injection hole 4C drilled between, for example, the through hole and the gas discharge valve. The electrolyte injection hole 4C is a hole for injecting electrolyte into the inside of the battery cover 4, and after the electrolyte is injected, it is sealed by joining the electrolyte plug 6, for example, by laser welding. The electrolyte injected into the battery case 2 is, for example, lithium hexafluorophosphate (LiPF) in a carbonate ester-based organic solvent such as ethylene carbonate. ６ A non-aqueous electrolyte containing a dissolved lithium salt such as ) can be used.

[0017] In addition, a positive external terminal 7 and a negative external terminal 8 are fixed to the battery cover 4. These positive external terminals 7 and negative external terminals 8 are arranged spaced apart in the longitudinal direction on the outer surface of the battery cover 4 (the upper surface 3C of the battery case 2) and are electrically and physically connected to the corresponding positive current collector plate 11 or negative current collector plate 12 inside the battery case 2 via the battery cover 4. The positive external terminal 7 is made of, for example, aluminum or an aluminum alloy, and the negative external terminal 8 is made of, for example, copper or a copper alloy.

[0018] The positive external terminal 7 and the negative external terminal 8 each have joints 7A and 8A that are connected to, for example, a busbar, and connecting parts 7B and 8B that are connected to the positive current collector plate 11 or the negative current collector plate 12, respectively. The joints 7A and 8A are formed in a substantially rectangular parallelepiped shape and are fixed to the outer surface of the battery cover 4 via gaskets 9 and 10 made of insulating material. The connecting parts 7B and 8B are cylindrical or cylindrical portions that extend from the bottom side of the joints 7A and 8A facing the battery cover 4 in a direction that penetrates the battery cover 4, and are integrally formed with the joints 7A and 8A.

[0019] As shown in Figure 2, the positive electrode current collector plate 11 and the negative electrode current collector plate 12 are plate-shaped members bent into a predetermined shape and connected to the wound electrode bodies 5, 5. The positive electrode current collector plate 11 connects the positive electrode external terminal 7 to the positive electrode stacked portion 5A, which is the positive electrode of the entire wound electrode body 5, 5, and the negative electrode current collector plate 12 connects the negative electrode external terminal 8 to the negative electrode stacked portion 5B, which is the negative electrode of the entire wound electrode body 5. The positive electrode current collector plate 11 is made of, for example, aluminum or an aluminum alloy, and the negative electrode current collector plate 12 is made of, for example, copper or a copper alloy.

[0020] The positive electrode current collector plate 11 and the negative electrode current collector plate 12 are each formed by bending to be positioned along the battery cover 4 and consist of base portions 11A and 12A connected to the corresponding positive electrode external terminal 7 or negative electrode external terminal 8, and extended portions 11B, 11B, 12B, 12B that extend along the wide side surface 3A of the battery container 3 toward the bottom surface 3D. The joint portions 11BA, 11BA, 12BA, 12BA of the extended portions 11B, 11B, 12B, 12B are joined to the positive electrode laminated portion 5A, which is formed by winding and flattening the positive electrode foil exposed portion 23B (Figure 3) of the wound electrode body 5, or to the negative electrode of the wound electrode body 5 by ultrasonic bonding or the like.

[0021] Figure 3 shows a portion of the wound electrode body 5 unfolded. The wound electrode body 5 is formed into a flat shape by stacking a first separator 20, a negative electrode 21, a second separator 22, and a positive electrode 23, each formed in a strip shape, in that order, and winding them with the positive electrode 23 on the inside. In this case, the first and second separators 20 and 22 are made of insulating material, so that the negative electrode 21 and the positive electrode 23 are wound in an insulated state.

[0022] The negative electrode 21 comprises a negative electrode mixture layer 21A formed by applying a negative electrode active material (negative electrode mixture) to both sides of a negative electrode metal foil, which is a negative electrode current collector, and a negative electrode foil exposed portion 21B provided on one end of the negative electrode metal foil in the width direction (x direction) where the negative electrode mixture is not applied.

[0023] The negative electrode metal foil is made of, for example, copper foil having a thickness of about 10 μm. The negative electrode mixture layer 21A is formed to a thickness of about 70 μm by applying a slurry-like negative electrode mixture to the negative electrode metal foil, drying the applied negative electrode mixture, and pressing it. The negative electrode 21 is manufactured by appropriately cutting the negative electrode metal foil on which the negative electrode mixture layer 21A has been formed.

[0024] As a slurry for the negative electrode mixture, for example, one can use a slurry prepared by adding 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder to 100 parts by weight of non-binding carbon powder, which is the negative electrode mixture, and then adding N-methylpyrrolidone (NMP) as a dispersion solvent and kneading the mixture.

[0025] Furthermore, the negative electrode active material contained in the negative electrode mixture layer 21A is not limited to the amorphous carbon described above. For example, the negative electrode active material may be natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbonaceous materials such as coke, or compounds such as Si or Sn (e.g., SiO, TiSi). ２ (etc.), or composite materials thereof can be used. Furthermore, the particle shape of the negative electrode active material is not particularly limited and may be, for example, flaky, spherical, fibrous, or lumpy.

[0026] On the other hand, the positive electrode 23 is configured to include a positive electrode mixture layer 23A formed by applying a positive electrode active material (positive electrode mixture) to both sides of a positive electrode metal foil, which is a positive electrode current collector, and a positive electrode foil exposed portion 23B on the other end side in the width direction (x direction) of the positive electrode metal foil, to which the positive electrode mixture is not applied.

[0027] The positive electrode metal foil is made of, for example, aluminum foil having a thickness of about 20 μm. The positive electrode mixture layer 23A is formed to a thickness of about 90 μm by applying a slurry-like positive electrode mixture, drying the applied mixture, and pressing it. The positive electrode 23 is manufactured by appropriately cutting the positive electrode metal foil on which the positive electrode mixture layer 23A is formed.

[0028] For example, the slurry of the positive electrode mixture is 100 parts by weight of lithium manganate (LiMn), which is the positive electrode mixture. ２ O ４To the above, 10 parts by weight of flaky graphite, which is a conductive material, and 10 parts by weight of PVDF, which is a binder, are added, and then NMP is added as a dispersion solvent and kneaded to produce a mixture that can be used.

[0029] The positive electrode active material contained in the positive electrode mixture layer 23A is not limited to the lithium manganese oxide described above. For example, other lithium manganese oxides having a spinel crystal structure, or lithium manganese composite oxides partially substituted or doped with a metal element can be used as the positive electrode active material. Alternatively, lithium cobalt oxide or lithium titanate having a layered crystal structure, or lithium-metal composite oxides partially substituted or doped with a metal element may be used as the positive electrode active material.

[0030] Furthermore, the binder used in the negative electrode mixture and positive electrode mixture is not limited to PVDF. Examples of binders that can be used include polymers such as polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene-butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, or acrylic resins, or mixtures thereof.

[0031] Although not shown in the diagram, the wound electrode body 5 may have an axis for winding the first separator 20, the negative electrode 21, the second separator 22, and the positive electrode 23 in a stacked manner. As the axis, for example, a resin sheet with higher bending rigidity than the positive electrode metal foil, the negative electrode metal foil, and the first and second separators 20 and 22 can be wound around it. Furthermore, the wound electrode body 5 is configured such that the dimensions of the negative electrode mixture layer 21A are larger than the dimensions of the positive electrode mixture layer 23A in the winding axis direction 24 (x direction), and the positive electrode mixture layer 23A is always sandwiched between the negative electrode mixture layers 21A.

[0032] In the wound electrode body 5, the exposed positive foil portion 23B of the positive electrode 23 and the exposed negative foil portion 21B of the negative electrode 21 are wound and stacked on one end and the other end in the winding axis direction 24 (x direction), as shown in Figure 3. Furthermore, the exposed positive foil portion 23B and the exposed negative foil portion 21B of each wound electrode body 5 are bundled flat, as shown in Figure 2, and joined to the joint portions 11BA and 12BA of the extended portions 11B and 12B of the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12, for example, by ultrasonic bonding or resistance bonding.

[0033] In the winding axis direction 24 (x direction), the dimensions of the first and second separators 20 and 22 are larger than the dimensions of the negative electrode mixture layer 21A of the negative electrode 21. However, the ends of the first and second separators 20 and 22 are positioned inside the winding electrode body 5 in the winding axis direction 24 (x direction) than the ends of the positive electrode foil exposed portion 23B of the positive electrode 23 and the negative electrode foil exposed portion 21B of the negative electrode 21. Therefore, the first and second separators 20 and 22 do not interfere when bundling the positive electrode foil exposed portion 23B of the positive electrode 23 and the negative electrode foil exposed portion 21B of the negative electrode 21 and joining them to the joint portion 11BA of the extended portion 11B of the positive electrode current collector plate 11 and the joint portion 12BA of the extended portion 12B of the negative electrode current collector plate 12, respectively.

[0034] The base portion 11A of the positive electrode current collector plate 11 and the base portion 12A of the negative electrode current collector plate 12 are fixed to the battery cover 4 via plate-shaped insulating members 13 and 14, respectively, and connected to the corresponding positive electrode external terminal 7 or negative electrode external terminal 8. More specifically, the connection portion 7B of the positive electrode external terminal 7 and the connection portion 8B of the negative electrode external terminal 8 are inserted, for example, through holes 9A and 10A of the gaskets 9 and 10, through hole 4A of the battery cover 4, through holes 13A and 14A of the insulating members 13 and 14, and through holes 11AA and 12AA of the base portions 11A and 12A of the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12, and are crimped so as to plastically deform the tip on the lower surface of the base portions 11A and 12A of the positive electrode current collector plate 11 or negative electrode current collector plate 12 to expand in diameter. As a result, the positive external terminal 7 and the positive current collector plate 11 are electrically connected to each other, and the negative external terminal 8 and the negative current collector plate 12 are electrically insulated from each other via gaskets 9 and 10 and insulating members 13 and 14, respectively, and are fixed to the battery cover 4.

[0035] Furthermore, the joint portion 11BA of the extended portion 11B of the positive electrode current collector plate 11 and the joint portion 12BA of the extended portion 12B of the negative electrode current collector plate 12 are joined to the positive electrode laminated portion 5A, which is formed by laminating the positive electrode foil exposed portion 23B of the wound electrode body 5, and the negative electrode laminated portion 5B, which is formed by laminating the negative electrode foil exposed portion 21B, respectively. As a result, the positive electrode 23 and the negative electrode 21 constituting the wound electrode body 5 are electrically connected to the corresponding positive electrode external terminal 7 or negative electrode external terminal 8 via the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12. The materials of the gaskets 9, 10 and the insulating members 13, 14 are, for example, electrically insulating resins such as polybutylene terephthalate, polyphenylene sulfide, and perfluoroalkoxy fluororesin.

[0036] Each of the wound electrode bodies 5, 5 is joined to a positive electrode current collector plate 11 and a negative electrode current collector plate 12, respectively, and is fixed to the battery cover 4 via the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12. It is then covered with an electrically insulating resin insulating cover 15 (Figure 2) and loaded into the battery container 3 through the opening 3E of the battery container 3. Each of the insulating covers 15, 15 is made by assembling a single sheet or multiple film members made of a synthetic resin such as polypropylene. Each of the insulating covers 15, 15 has dimensions and a shape that allows it to integrally cover almost the entire wound electrode body 5 to which the positive electrode current collector plate 11 and the negative electrode current collector plate 12 are joined.

[0037] As shown in Figures 2 and 3, each of the wound electrode bodies 5, 5 is wound in a flattened shape and has semi-cylindrical curved portions 5C provided at both ends in the height direction (z direction) of the battery case 2, and a flat portion 5D between these curved portions 5C. As shown in Figure 2, the wound electrode bodies 5, 5 are arranged along the y direction (for example, parallel) with the flat portions 5D facing each other. The wound electrode body 5 is loaded into the battery container 3 from one curved portion 5C so that the winding axis 24 direction is aligned with the width direction (x direction) of the secondary battery 1, and is housed in the battery container 3 so that the other curved portion 5C faces the battery cover 4. Then, as described above, the battery case 2 is constructed by joining the battery cover 4 around the entire circumference of the opening 3E of the battery container 3, the electrolyte is injected into the inside of the battery case 2 through the electrolyte injection hole 4C, and the battery case 2 is sealed by joining the electrolyte injection plug 6 to the electrolyte injection hole 4C.

[0038] With the above configuration, the secondary battery 1 can charge the wound electrode bodies 5, 5 by supplying power to the positive electrode 23 and negative electrode 21 of the wound electrode bodies 5, 5 via the positive electrode external terminal 7 and positive electrode current collector plate 11, and the negative electrode external terminal 8 and negative electrode current collector plate 12, respectively, or it can output power to the outside from the positive electrode 23 and negative electrode 21 of the wound electrode bodies 5, 5 via the positive electrode current collector plate 11 and positive electrode external terminal 7, and the negative electrode current collector plate 12 and negative electrode external terminal 8.

[0039] Figure 4 is a cross-sectional view taken along line IV-IV in Figure 1.

[0040] In the battery container 3, the wound electrode bodies 5, 5 are arranged along the thickness direction (y-direction) of the secondary battery 1 such that their main surfaces (the flat portions 5D exemplified in Fig. 2) face each other. One curved portion 5C of each wound electrode body 5 is in contact with the bottom of the battery container 3, and the other curved portion 5C faces the battery lid 4. According to the example shown in Fig. 4, the wound electrode bodies 5, 5 are in contact with each other in the thickness direction, but a gap may be provided between the wound electrode bodies 5, 5. According to the example shown in Fig. 4, in the battery container 3, there is a gap between the main surface on the y-direction side of the wound electrode body 5 on the y-direction side and the inner wall on the y-direction side of the battery container 3, but the main surface and the inner wall may be in contact with each other and there may be no gap. Similarly, according to the example shown in Fig. 4, in the battery container 3, there is a gap between the main surface on the -y-direction side of the wound electrode body 5 on the -y-direction side and the inner wall on the -y-direction side of the battery container 3, but the main surface and the inner wall may be in contact with each other and there may be no gap.

[0041] In this embodiment, the liquid injection hole 4C is located directly above the curved top portion 5CT of any one of the wound electrode bodies 5. In other words, as will be described later with reference to Fig. 5, in a top view of the secondary battery 1, the liquid injection hole 4C overlaps the curved portion top portion 5CT of any one of the wound electrode bodies 5.

[0042] The liquid injection hole 4C is sealed by a liquid injection plug 6. The liquid injection plug 6 has a body portion 6B inserted into the liquid injection hole 4C, and a head portion 6A connected to the body portion 6B and having a seat surface in contact with the peripheral surface of the liquid injection hole. The body portion 6B extends vertically downward from the head portion 6A. The body portion 6B is inserted into the liquid injection hole 4C, and the seat surface of the head portion 6A is in contact with the peripheral surface of the liquid injection hole 4C in the battery lid 4. The height of the body portion 6B is less than or equal to the length of the liquid injection hole 4C (the thickness of the battery lid 4). Therefore, the tip end of the body portion 6B of the liquid injection plug 6 that seals the liquid injection hole 4C does not extend below the inner surface (ceiling surface) of the battery lid 4. As a result, in this embodiment, the fact that the liquid injection hole 4C is located directly above the curved top portion 5CT of the wound electrode body 5 does not impose a restriction on the height of the wound electrode body 5.

[0043] Figure 5 is a top view of the secondary battery 1 according to Embodiment 1. For convenience, one of the wound electrode bodies 5 will be referred to as "first wound electrode body 5-1" and the other wound electrode body 5 as "second wound electrode body 5-2". Note that in Figure 5, the gas discharge valve 4B, the positive electrode external terminal 7, and the negative electrode external terminal 8 on the battery cover 4 are omitted from the illustration for improved visibility.

[0044] The upper surface of the battery cover 4 can be divided into a first region 500-1, which is the region on one side (the -y direction side), and a second region 500-2, which is the region on the other side (the y direction side), with a first center line 510 extending along the width direction (x direction) of the secondary battery 1 as the center line. In other words, the upper surface of the battery cover 4 can be divided into regions 500 that are opposite to and overlap with the top view range of each wound electrode body 5. In this embodiment, since there are two wound electrode bodies 5 housed in the battery container 3, the boundary (valley) between the wound electrode bodies 5 coincides with the first center line 510, and there are two regions 500-1 and 500-2 divided with respect to the first center line 510.

[0045] The liquid injection hole 4C is provided in one of the first region 500-1 and the second region 500-2, for example, in the first region 500-1. The liquid injection hole 4C is positioned so as to overlap with the curved top portion 5CT-1 that extends along the width direction of the first wound electrode body 5-1 when viewed from above the secondary battery 1. The position of the liquid injection hole 4C along the width direction can be any position as long as it overlaps with the curved top portion 5CT-1 that extends along the width direction.

[0046] As described above, according to Example 1, when viewed from the top of the secondary battery 1, the liquid injection hole 4C is provided at a position overlapping the curved top portion 5CT-1 of the first wound electrode body 5-1. Accordingly, the electrolyte injected from the liquid injection hole 4C first reaches the curved top portion 5CT-1 of the first wound electrode body 5-1, and then the electrolyte spreads from the curved top portion 5CT-1 downward into the first wound electrode body 5-1 while splitting from the curved top portion 5CT-1 in the y direction and the -y direction, advancing to the valley between the first wound electrode body 5-1 and the second wound electrode body 5-2, and also advancing to the gap between the first wound electrode body 5-1 and the inner wall surface of the battery container 3. Since the electrolyte flows and infiltrates in this manner, it can be expected to shorten the time required for the electrolyte to infiltrate the first wound electrode body 5-1 and the second wound electrode body 5-2.

[0047] Example 2 will be described. Hereinafter, differences from Example 1 will be mainly described, and descriptions of common points with Example 1 will be omitted or simplified.

[0048] In Example 2, a plurality of liquid injection holes 4C are provided in the battery lid 4. Each liquid injection hole 4C is provided at a position overlapping the curved top portion of any one of the wound electrode bodies 5 when viewed from the top of the battery lid 4.

[0049] An example of a summary of Examples 1 and 2 is as follows: The secondary battery 1 (an example of a battery) comprises a plurality of wound electrode bodies (5, 5), a battery container (3) having an opening (3E) that houses the plurality of wound electrode bodies and electrolyte, and a battery cover (4) that covers the opening of the battery container and has one or more injection holes (4C) into which the electrolyte is injected. The plurality of wound electrode bodies are arranged in parallel along the thickness direction in the battery container. Each of the plurality of wound electrode bodies has a pair of curved portions (5C) each having a curved apex (5CT), and a flat portion (5D) connecting the pair of curved portions (5C). All or some of the one or more injection holes are located in positions that overlap the curved apex of one of the wound electrode bodies when viewed from above the battery cover. This is expected to shorten the time required for electrolyte infiltration. As a result, for example, it is expected that a highly productive battery can be provided. In a top view of the battery cover, in all or some of the above-mentioned fluid injection holes, the injection holes may be provided in any of the multiple regions (501, 501) that are opposite to each other in a top view of the multiple wound electrode bodies. The wound electrode body 5 may be a winding of a positive electrode and a negative electrode. The wound electrode body 5 may also be called a wound electrode group. Each fluid injection hole may be sealed with the above-mentioned fluid injection plug (6), that is, a fluid injection plug having the above-mentioned body portion (6B) and head portion (6A). Furthermore, in Examples 1 and 2, for the sake of simplicity of explanation, all of the "one or more fluid injection holes" in this paragraph are provided in a position that overlaps with the curved apex of the curved portion of one of the multiple wound electrode bodies in a top view of the battery cover, but fluid injection holes provided in positions other than such positions may also be provided. In other words, "some of the injection holes" of "one or more injection holes" may be located in positions that overlap with the curved apex when viewed from above, while the remaining injection holes may be located in positions other than such positions.

[0050] An example of the arrangement of multiple injection holes 4C is as follows:

[0051] Figure 6 is a top view of the first secondary battery 1A according to Example 2.

[0052] First and second fluid injection holes 4C-1 and 4C-2 are provided, corresponding to the first and second wound electrode bodies 5-1 and 5-2. In a top view of the battery cover 4, the first fluid injection hole 4C-1 is positioned to overlap the curved top portion 5CT-1 of the first wound electrode body 5-1, and the second fluid injection hole 4C-2 is positioned to overlap the curved top portion 5CT-2 of the second wound electrode body 5-2.

[0053] Here, the first electrolyte injection hole 4C-1 and the second electrolyte injection hole 4C-2 are positioned symmetrically with respect to the first center line 510 of the battery cover 4. The electrolyte is poured in parallel from the first electrolyte injection holes 4C-1 and 4C-2, which are positioned symmetrically, and reaches the curved top 5CT-1 of the first wound electrode body 5-1 and the curved top 5CT-2 of the second wound electrode body 5-2 in parallel, so it is expected that the electrolyte will permeate the first and second wound electrode bodies 5-1 and 5-2 in a short time.

[0054] Figure 7 is a top view of the second secondary battery 1B according to Example 2.

[0055] The difference from the first secondary battery 1A shown in Figure 6 is that the first electrolyte injection hole 4C-1 and the second electrolyte injection hole 4C-2 are located in point-symmetric positions with respect to the center point 700 of the battery cover 4. The center point 700 is the intersection of the first center line 510 extending along the width direction and the second center line 520 extending along the thickness direction. Electrolyte is poured in parallel from the point-symmetrically positioned first electrolyte injection holes 4C-1 and 4C-2, reaching the curved top 5CT-1 of the first wound electrode body 5-1 and the curved top 5CT-2 of the second wound electrode body 5-2 in parallel, and it is expected that the electrolyte will permeate the first and second wound electrode bodies 5-1 and 5-2 in a short time.

[0056] Furthermore, it is not necessary for all the liquid injection holes 4C to be evenly positioned to overlap the curved peaks of multiple different wound electrode bodies 5, 5, and there may be some bias in their arrangement. For example, in the third secondary battery 1C illustrated in Figure 8, all the liquid injection holes 4C-11 and 4C-12 are positioned to overlap the winding peak 5CT-1 of the first wound electrode body 5-1, and none of the liquid injection holes 4C are positioned to overlap the winding peak 5CT-2 of the second wound electrode body 5-2. Also, in the fourth secondary battery 1D illustrated in Figure 9, all the liquid injection holes 4C-21 and 4C-22 are positioned to overlap the winding peak 5CT-2 of the second wound electrode body 5-2, and none of the liquid injection holes 4C are positioned to overlap the winding peak 5CT-1 of the first wound electrode body 5-1.

[0057] In the explanation so far, two wound electrode bodies 5, 5 have been used as examples of multiple wound electrode bodies, with one wound electrode body 5 being the first wound electrode body and the other being the second wound electrode body. However, three or more wound electrode bodies 5, 5, ... may be used as multiple wound electrode bodies. The above-mentioned line symmetry or point symmetry arrangements can also be applied to three or more wound electrode bodies 5, 5, ...

[0058] Specifically, as shown in Figures 10 to 13, there are fifth to eighth secondary batteries 1E to 1H, each containing three wound electrode bodies 5-1 to 5-3 as a plurality of wound electrode bodies. The three wound electrode bodies 5-1 to 5-3 are arranged parallel to each other in the thickness direction.

[0059] In the fifth secondary battery 1E shown in Figure 10, the liquid injection hole 4C-1, which is located at the curved apex 5CT-1 of the wound electrode body 5-1, and the liquid injection hole 4C-2, which is located at the curved apex 5CT-2 of the wound electrode body 5-2, are symmetrical with respect to the boundary between the wound electrode bodies 5-1 and 5-2. Similarly, the liquid injection hole 4C-2, which is located at the curved apex 5CT-2 of the wound electrode body 5-2, and the liquid injection hole 4C-3, which is located at the curved apex 5CT-3 of the wound electrode body 5-3, are symmetrical with respect to the boundary between the wound electrode bodies 5-2 and 5-3. Thus, in the three wound electrode bodies 5-1 to 5-3, the two liquid injection holes 4C are symmetrical with respect to the boundary between two consecutive wound electrode bodies.

[0060] In the sixth secondary battery 1F shown in Figure 11, the liquid injection hole 4C-1, which is located on the curved top 5CT-1 of the wound electrode body 5-1, and the liquid injection hole 4C-2, which is located on the curved top 5CT-2 of the wound electrode body 5-2, are point-symmetrical with respect to the intersection point 700A of the boundary between the boundary between the wound electrode bodies 5-1 and 5-2 and the central axis 520 along the thickness direction. Similarly, the liquid injection hole 4C-2, which is located on the curved top 5CT-2 of the wound electrode body 5-2, and the liquid injection hole 4C-3, which is located on the curved top 5CT-3 of the wound electrode body 5-3, are point-symmetrical with respect to the intersection point 700B of the boundary between the boundary between the wound electrode bodies 5-2 and 5-3 and the central axis 520. Thus, in the three wound electrode bodies 5-1 to 5-3, the two injection holes 4C are point-symmetrical with respect to the boundary between two consecutive wound electrode bodies.

[0061] As illustrated in Figures 12 and 13, it is not necessary for at least one liquid injection hole 4C to overlap the curved top 5CT of all wound electrode bodies 5, and there may be wound electrode bodies 5 where the liquid injection holes 4C do not overlap when viewed from above. For example, some liquid injection holes 4C may be concentrated on some wound electrode bodies 5, or the number of liquid injection holes 4C may be less than the number of wound electrode bodies 5. For example, in the seventh secondary battery 1G shown in Figure 12, the liquid injection hole 4C-1 located at a position overlapping the curved top 5CT-1 of wound electrode body 5-1 and the liquid injection hole 4C-3 located at a position overlapping the curved top 5CT-3 of wound electrode body 5-3 are symmetrical with respect to the boundary between wound electrode bodies 5-1 and 5-3 (in this case, the boundary may be, for example, a boundary equidistant in the thickness direction from wound electrode bodies 5-1 and 5-3). Furthermore, for example, according to the eighth secondary battery 1H shown in Figure 13, the liquid injection hole 4C-1, which is located on the curved top 5CT-1 of the wound electrode body 5-1, and the liquid injection hole 4C-3, which is located on the curved top 5CT-3 of the wound electrode body 5-3, are point-symmetrical with respect to the intersection point 700C of the central axis 520, with respect to the intersection point 700C of the boundary between the boundary between the wound electrode bodies 5-1 and 5-3 (in this case, the boundary may be, for example, a boundary that is equidistant in the thickness direction from the wound electrode bodies 5-1 and 5-3).

[0062] An example of a summary of the above embodiment 2 is as follows: That is, all of the "one or more injection holes, all or some of them" described above may be provided in a position that overlaps with the curved top of one wound electrode body (5) in a top view, but multiple of the "all or some of the injection holes" described above may be provided in a position that overlaps with the curved tops of multiple wound electrode bodies (5). For example, the multiple wound electrode bodies may include a first wound electrode body and a second wound electrode body. The "all or some of the injection holes" described above may include a first injection hole and a second injection hole. In a top view of the battery cover, the first injection hole may be provided in a position that overlaps with the curved top of the first wound electrode body, and the second injection hole may be provided in a position that overlaps with the curved top of the second wound electrode body. Furthermore, the first injection hole and the second injection hole may be positioned symmetrically with respect to the boundary between the first wound electrode body and the second wound electrode body, or they may be positioned symmetrically with respect to the position at the boundary between the first wound electrode body and the second wound electrode body. In this paragraph, the "first wound electrode body" and the "second wound electrode body" may refer to two adjacent, continuous wound electrode bodies among a plurality of wound electrode bodies, as illustrated in Figures 6, 7, 10, or 11, or they may refer to two wound electrode bodies separated by one or more wound electrode bodies among a plurality of wound electrode bodies, as illustrated in Figure 12 or 13.

[0063] Although several embodiments have been described above, these are merely illustrative examples for explaining the present invention and are not intended to limit the scope of the invention to these embodiments only. The present invention can be carried out in various other forms.

[0064] 1: Battery, 3: Battery container, 3E: Opening, 4: Battery cover, 4C: Injection hole, 5: Winding electrode body, 5C: Curved section, 5D: Flat section, 6: Injection plug

Claims

1. A battery comprising: a plurality of wound electrode bodies; a battery container having an opening, which houses the plurality of wound electrode bodies and an electrolyte; and a battery cover which covers the opening of the battery container and has one or more injection holes formed therein into which the electrolyte is injected, wherein the plurality of wound electrode bodies are arranged in the thickness direction within the battery container, each of the plurality of wound electrode bodies has a pair of curved portions having curved apexes and a flat portion connecting the pair of curved portions, and all or some of the one or more injection holes are located in positions that overlap the curved apex of a curved portion of any of the plurality of wound electrode bodies when viewed from above the battery cover.

2. The battery according to claim 1, wherein the plurality of wound electrode bodies include a first wound electrode body and a second wound electrode body, all or part of the liquid injection holes include a first liquid injection hole and a second liquid injection hole, and in a top view of the battery cover, the first liquid injection hole is provided at a position overlapping the curved apex of the first wound electrode body, and the second liquid injection hole is provided at a position overlapping the curved apex of the second wound electrode body.

3. The battery according to claim 2, wherein the first injection hole and the second injection hole are provided in positions symmetrical with respect to the boundary between the first wound electrode body and the second wound electrode body.

4. The battery according to claim 3, wherein the second wound electrode is a wound electrode adjacent to the first wound electrode.

5. The battery according to claim 2, wherein the first injection hole and the second injection hole are provided in positions that are point-symmetric with respect to the boundary between the first wound electrode body and the second wound electrode body.

6. The battery according to claim 3, wherein the second wound electrode is a wound electrode adjacent to the first wound electrode.

7. The battery according to claim 1, further comprising, for all or some of the aforementioned liquid injection holes, a liquid injection plug for sealing the liquid injection hole, wherein, for all or some of the aforementioned liquid injection holes, the liquid injection plug for sealing the liquid injection hole comprises a body portion inserted into the liquid injection hole and a head portion connected to the body portion and having a seating surface that contacts the surrounding surface of the liquid injection hole, and the height of the body portion is less than or equal to the length of the liquid injection hole.

8. A battery cover that covers the opening of a battery container housing a plurality of wound electrode bodies, having one or more injection holes into which electrolyte is injected, wherein the plurality of wound electrode bodies are arranged in the thickness direction within the battery container, each of the plurality of wound electrode bodies has a pair of curved portions having curved apexes and a flat portion connecting the pair of curved portions, and all or some of the one or more injection holes are located in a position that overlaps the curved apex of a curved portion of any of the plurality of wound electrode bodies when viewed from above.

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