Battery

Abstract

A cylindrical battery, which is an example of the embodiment of the present invention, is provided with: an electrode body (14); an electrolyte; a bottomed cylindrical outer package can (16) that houses the electrode body (14) and the electrolyte; and a sealing body (17) that closes the opening of the outer package can (16). A groove part (22) for supporting the sealing body (17) is formed in the inner surface of the outer package can (16). The cylindrical battery is additionally provided with an upper insulating plate (18) that is provided between the electrode body (14) and the groove part (22). A recess (30) into which an end of the upper insulating plate (18) fits is formed in the inner surface of the outer package can (16), and the upper insulating plate (18) is fixed to the recess (30).

Description

battery

[0001] The present disclosure relates to batteries, and more particularly to batteries with insulating plates.

[0002] Conventionally, cylindrical batteries have been widely known, which include a bottomed cylindrical outer can containing an electrode assembly and a nonaqueous electrolyte, a sealing body that closes the opening of the outer can, and an upper insulating plate disposed between the electrode assembly and the sealing body, with a groove formed in the outer can to support the sealing body (see, for example, Patent Document 1). Generally, sealed batteries such as cylindrical batteries are provided with a safety valve for releasing gas when an abnormality occurs in the battery and the internal pressure rises. In the cylindrical battery of Patent Document 1, a safety valve is provided in the sealing body, and in the event of an abnormality in the battery, the safety valve ruptures, releasing high-temperature gas from the sealing body side.

[0003] In applications requiring high capacity, such as electric vehicles, hybrid vehicles, and other electrically powered vehicles, and power storage systems, a plurality of batteries are generally used in the form of a battery module connected in series or in parallel.

[0004] Japanese Patent Application Laid-Open No. 2020-149821

[0005] Generally, when cylindrical batteries are modularized, multiple batteries are closely arranged adjacent to each other so that the bottom surfaces of the outer cans are flush with each other. However, as batteries continue to increase in capacity and power output, it is conceivable that the side wall of the outer can may break in the event of an abnormality, releasing high-temperature gas. In this case, there is a risk that the high-temperature gas may affect adjacent batteries. Therefore, it is important to prevent the side wall of the outer can from breaking in the event of a battery abnormality.

[0006] A battery according to one aspect of the present disclosure comprises an electrode assembly, an electrolyte, a cylindrical outer can with a bottom that houses the electrode assembly and the electrolyte, and a sealing body that closes an opening of the outer can, wherein a grooved portion that supports the sealing body is formed in the outer can, and the battery further comprises an upper insulating plate that is provided between the electrode assembly and the grooved portion of the outer can, and the upper insulating plate is press-fitted into the outer can and is disposed in close contact with the inner surface of the outer can.

[0007] Another aspect of the present disclosure provides a battery comprising an electrode body, an electrolyte, a cylindrical outer can with a bottom that houses the electrode body and the electrolyte, and a sealing body that closes the opening of the outer can, wherein a grooved portion that supports the sealing body is formed in the outer can, and the battery further comprises an upper insulating plate provided between the electrode body and the grooved portion of the outer can, wherein a recessed portion into which an end of the upper insulating plate fits is formed on the inner surface of the outer can, and the upper insulating plate is fixed to the recessed portion.

[0008] According to the battery according to the present disclosure, it is possible to prevent the side surface portion of the outer can from breaking in the event of an abnormality.

[0009] 1 is a cross-sectional view of a cylindrical battery according to an embodiment of the present invention, and is an enlarged view of the vicinity of a grooved portion.

[0010] Hereinafter, an example of an embodiment of a battery according to the present disclosure will be described in detail with reference to the drawings. Note that configurations obtained by selectively combining the components of multiple embodiments and variations described below are included within the scope of the present disclosure.

[0011] In the embodiment described below, a cylindrical battery 10 is illustrated in which a wound electrode assembly 14 is housed in a cylindrical outer can 16 with a bottom, but the outer can of the battery is not limited to a cylindrical outer can. The battery according to the present disclosure may be any battery that includes a cylindrical outer can with a bottom that houses an electrode assembly and an electrolyte, a sealing body that closes the opening of the outer can, and a grooved portion that supports the sealing body formed in the outer can. Another example of an embodiment is a prismatic battery that includes a rectangular outer can. Furthermore, the electrode assembly is not limited to a wound type, and may be a stacked electrode assembly in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators interposed therebetween.

[0012] FIG. 1 is a schematic diagram illustrating an axial cross section of a cylindrical battery 10 according to an embodiment. As shown in FIG. 1 , the cylindrical battery 10 includes a wound electrode assembly 14, an electrolyte, a cylindrical outer can 16 with a bottom that accommodates the electrode assembly 14 and the electrolyte, and a sealing member 17 that closes the opening of the outer can 16. In this embodiment, the sealing member 17 is provided with a safety valve that ruptures to release gas in the event of a battery malfunction. The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a spirally wound structure in which the positive electrode 11 and the negative electrode 12 are wound around the separator 13. Hereinafter, for convenience of explanation, the sealing member 17 side of the battery is referred to as the top, and the bottom side of the outer can 16 is referred to as the bottom.

[0013] The electrolyte may be an aqueous electrolyte, but in this embodiment, a non-aqueous electrolyte is used. The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte may be a liquid electrolyte (electrolytic solution) or a solid electrolyte. The cylindrical battery 10 is, for example, a lithium ion battery.

[0014] The liquid electrolyte (electrolytic solution) contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. Examples of the electrolyte salt include LiPF ６ Lithium salts such as

[0015] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesins, acrylic resins, and polyether resins. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0016] The positive electrode 11, negative electrode 12, and separator 13 that constitute the electrode assembly 14 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in the length and width directions. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and, for example, two separators 13 are arranged to sandwich the positive electrode 11. The electrode assembly 14 has a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.

[0017] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer provided on the positive electrode core. The positive electrode core can be a foil of a metal stable within the potential range of the positive electrode 11, such as aluminum, an aluminum alloy, stainless steel, or titanium, or a film with such a metal disposed on the surface layer. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder, and is preferably provided on both sides of the positive electrode core. The positive electrode active material is a lithium transition metal composite oxide containing a transition metal element such as Ni, Co, or Mn.

[0018] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer provided on the negative electrode core. The negative electrode core can be a foil of a metal stable within the potential range of the negative electrode 12, such as copper, copper alloy, stainless steel, nickel, or nickel alloy, or a film with such a metal disposed on its surface. The negative electrode mixture layer contains a negative electrode active material and a binder, and is preferably provided on both sides of the negative electrode core except for the portion to which the negative electrode lead 21 is connected. The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. The negative electrode active material may also use an element that alloys with Li, such as Si or Sn, or a material containing such an element.

[0019] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. The separator 13 may have, for example, a multi-layer structure including a thermoplastic resin layer such as polyolefin and a cellulose fiber layer, a two-layer structure of polyethylene (PE) / polypropylene (PP), or a three-layer structure of PE / PP / PE.

[0020] The outer can 16 is a cylindrical metal container with a bottom and an opening at one axial end, and the upper opening of the outer can 16 is closed by a sealing body 17. The cylindrical battery 10 includes an upper insulating plate 18 disposed between the electrode body 14 and the sealing body 17. The cylindrical battery 10 also includes a lower insulating plate 19 disposed between the electrode body 14 and the inner bottom surface of the outer can 16. That is, insulating plates are disposed above and below the electrode body 14.

[0021] In this embodiment, the positive electrode lead 20 passes through the through hole 18a of the upper insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the lower insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.

[0022] A gasket 28 is provided between the exterior can 16 and the sealing body 17 to ensure a tight seal inside the battery. The gasket 28 also functions to insulate the exterior can 16 from the sealing body 17. The exterior can 16 has a grooved portion 22 formed inward on its side surface, which supports the sealing body 17. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the exterior can 16, and supports the sealing body 17 on its top surface. The sealing body 17 is fixed to the top of the exterior can 16 by the grooved portion 22 and the open end of the exterior can 16, which is crimped to the sealing body 17.

[0023] Sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked. Each member constituting sealing body 17 has, for example, a disk or ring shape, and each member except for insulating member 25 is electrically connected to each other. Lower valve body 24 and upper valve body 26 are connected at their respective centers, and insulating member 25 is interposed between their respective peripheral edges.

[0024] If an abnormality occurs in the cylindrical battery 10 and the internal pressure rises, the lower valve body 24 deforms and pushes the upper valve body 26 toward the cap 27, causing it to break, cutting off the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure of the battery rises further, the upper valve body 26 breaks, causing high-temperature gas to be released from the opening of the cap 27. In other words, the sealing body 17 is provided with a current interruption mechanism and a safety valve. The safety valve is composed of two valve bodies (the lower valve body 24 and the upper valve body 26).

[0025] The configuration of the exterior can 16 and upper insulating plate 18 will be described in detail below with further reference to Figure 2. Figure 2 is an enlarged cross-sectional view showing the vicinity of the grooved portion 22 of the cylindrical battery 10.

[0026] 1 and 2 , the upper insulating plate 18 is a plate-shaped insulating member disposed between the electrode body 14 and the sealing body 17 so as to widely cover the upper surface of the electrode body 14. As described above, in this embodiment, the sealing body 17 serves as the positive electrode terminal, and the outer can 16 serves as the negative electrode terminal. Therefore, the upper insulating plate 18 insulates the negative electrode 12 of the electrode body 14 from the sealing body 17 and the positive electrode 11 of the electrode body 14 from the outer can 16 so that these components do not come into contact with each other.

[0027] The grooved portion 22 is formed in a ring shape and protrudes radially inward from the outer can 16. However, as batteries become larger in capacity and power output, high-temperature gas generated from the electrode body 14 in the event of a battery abnormality may directly hit the grooved portion 22, causing a rupture of the side portion of the outer can 16. This may have an adverse effect on adjacent batteries. For this reason, it is necessary to prevent rupture of the side portion of the outer can 16 and ensure that the high-temperature gas is discharged through the safety valve of the sealing body 17. As a result of studies by the present inventors, it has been found that the upper insulating plate 18 plays a major role in preventing rupture of the side portion of the outer can 16.

[0028] The upper insulating plate 18 is a circular plate with at least one through hole 18a formed therein. For example, the circle along the outer periphery of the upper insulating plate 18 has a perfect circular shape in a plan view. The upper insulating plate 18 widely covers the upper surface of the electrode body 14, and the sealing body 17 disposed on the upper insulating plate 18 is provided with a safety valve that opens to release gas in the event of a battery abnormality. For this reason, the upper insulating plate 18 is formed with a through hole 18a to ensure smooth exhaust from the safety valve. This through hole 18a also serves as a hole for the positive electrode lead 20 and the electrolyte to pass through.

[0029] The upper insulating plate 18 is preferably composed primarily of a highly heat-resistant resin, for example, a curable resin having a cross-linked structure. Alternatively, the upper insulating plate 18 may be composed primarily of a thermoplastic resin having a melting point of 200°C or higher. Examples of thermoplastic resins having a melting point of 200°C or higher include polyamide, polyether ether ketone, and thermoplastic polyimide. Here, the term "main component" refers to the component that constitutes the largest mass percentage of the components of the upper insulating plate 18. The upper insulating plate 18 also preferably includes a reinforcing material such as a fiber material such as glass fiber or carbon fiber, or a filler such as silica, clay, or mica.

[0030] The curable resin constituting the upper insulating plate 18 does not have a melting point, for example, and does not melt even at high temperatures of 200°C or higher. The upper insulating plate 18 is made of, for example, a fiber-reinforced phenolic resin. The fiber-reinforced phenolic resin contains a fiber material such as glass fiber and a curable resin, phenolic resin, and has excellent heat resistance. Examples of the curable resin constituting the upper insulating plate 18 include phenolic resin, urea resin, melamine resin, epoxy resin, and thermosetting polyimide. Among these, phenolic resin and epoxy resin are preferred, and phenolic resin is more preferred.

[0031] As shown in FIG. 2 , a recess 30 into which the end of the upper insulating plate 18 fits is formed on the inner surface of the outer can 16, and the upper insulating plate 18 is fixed in the recess 30. The recess 30 is formed between the electrode body 14 and the grooved portion 22 in the axial direction (vertical direction) of the outer can 16. The recess 30 is preferably formed in an annular shape along the inner circumferential surface of the cylindrical outer can 16. The recess 30 is formed, for example, by processing the inner circumferential surface of the outer can 16 with a roller, and is formed in the shape of a narrow groove having a substantially constant width and depth D along its entire length. The recess 30 is preferably formed at the same height along its entire length so that the upper insulating plate 18 is disposed parallel to the radial direction of the outer can 16.

[0032] It is preferable that the outer peripheral edge of the upper insulating plate 18 fits into the recessed portion 30 over its entire length. This brings the upper insulating plate 18 into close contact with the inner peripheral surface of the outer can 16, eliminating any gap between the inner peripheral surface of the outer can 16 and the upper insulating plate 18. In other words, high-temperature gas generated from the electrode assembly 14 in the event of a battery abnormality is prevented from passing through the gap between the inner peripheral surface of the outer can 16 and the upper insulating plate 18 and directly hitting the grooved portion 22. The upper insulating plate 18 has a through-hole 18a, but the through-hole 18a is not located in a position that overlaps with the grooved portion 22 in the vertical direction, and when the upper insulating plate 18 is viewed from the electrode assembly 14 side, the entire grooved portion 22 is covered by the upper insulating plate 18.

[0033] The upper insulating plate 18 has a diameter larger than the inner diameter of the portion of the outer can 16 where the recessed portion 30 is not present. The inner diameter of the portion of the outer can 16 from the grooved portion 22 to the can bottom is substantially constant, and the diameter of the upper insulating plate 18 is larger than the inner diameter of that portion. It is preferable that the diameter of the upper insulating plate 18 is at least the length obtained by adding the depth D of the recessed portion 30 to the inner diameter of the portion of the outer can 16 from the grooved portion 22 to the can bottom, or the length obtained by adding twice the length of the depth D of the recessed portion 30 to the inner diameter of the outer can 16. In this case, the upper insulating plate 18 is more securely fixed to the recessed portion 30 of the outer can 16, and direct impact of high-temperature gas on the grooved portion 22 is more effectively suppressed.

[0034] The upper insulating plate 18 has a diameter larger than the inner diameter of the outer can 16, and is therefore press-fitted from the opening of the outer can 16. Note that the upper insulating plate 18 can be press-fitted into the outer can 16 as long as the diameter of the upper insulating plate 18 is approximately twice the inner diameter of the outer can 16 plus the depth D of the recessed portion 30. The upper insulating plate 18 is press-fitted up to the portion where the recessed portion 30 is formed, and is fixed inside the outer can 16 by fitting into the recessed portion 30. Thereafter, a grooved portion 22 is formed in the outer can 16, and the sealing body 17 is crimped to seal the inside of the battery.

[0035] The depth D of the recessed portion 30 is preferably deep from the viewpoint of fixing the upper insulating plate 18, but is preferably less than 50% of the thickness T1 of the outer can 16 in consideration of the durability of the outer can 16, etc. In this embodiment, the thickness T1 of the outer can 16 is substantially constant over the entire side surface portion. That is, the entire side surface portion including the grooved portion 22, excluding the portion where the recessed portion 30 is formed, has substantially the same thickness T1. By making the thickness T1 of the outer can 16 constant, fracture of the side surface portion of the outer can 16 is more effectively suppressed.

[0036] The depth D of the recessed portion 30 is preferably 20% or more of the thickness T1 of the outer can 16. That is, an example of a suitable range for the depth D of the recessed portion 30 is 20% or more and less than 50% of the thickness T1. If the depth D of the recessed portion 30 is within this range, the upper insulating plate 18 can be stably fixed while ensuring good durability of the outer can 16. The thickness T1 of the outer can 16 is, for example, 150 μm or more and 350 μm or less, or 200 μm or more and 300 μm or less. Note that the depth D of the recessed portion 30 refers to the radial length from the inner surface of the outer can 16 in a portion where the recessed portion 30 is not formed to the deepest portion located at the outermost side of the recessed portion 30 in the radial direction of the outer can 16.

[0037] 2, the bottom of the recessed portion 30 extends along the vertical direction of the outer can 16, and the sidewalls located on both sides of the recessed portion 30 in the width direction are formed approximately perpendicular to the bottom, but the shape of the recessed portion 30 is not limited to this shape. The recessed portion 30 may be formed so as to gradually become deeper toward its deepest portion, or so as to gradually increase in width toward the radially inner side of the outer can 16. From the viewpoint of improving the durability of the outer can 16, it is preferable that the bottom of the recessed portion 30 is approximately flat, and it is preferable that the boundary portion between the bottom and the sidewalls is gently curved.

[0038] As described above, the upper insulating plate 18 is press-fitted into the outer can 16, fitted into the recessed portion 30, and disposed in close contact with the inner surface of the outer can 16. The upper insulating plate 18 may abut against the bottom of the recessed portion 30 and be compressed radially of the outer can 16 within the recessed portion 30. Alternatively, the upper insulating plate 18 may be sandwiched from above and below by the side walls of the recessed portion 30. The thickness T2 of the upper insulating plate 18 is, for example, larger than the thickness T1 of the outer can 16, specifically, 250 μm or more and 350 μm or less. The width of the recessed portion 30 is equal to or slightly larger than the thickness T2 of the upper insulating plate 18; however, it is also possible to form the width of the recessed portion 30 slightly smaller than the thickness T2 of the upper insulating plate 18 and press-fit the upper insulating plate 18 into the recessed portion 30.

[0039] As described above, cylindrical battery 10 having the above configuration can more reliably prevent the side portions of outer can 16 from breaking in the event of an abnormality. By tightly fitting upper insulating plate 18 to the inner surface of outer can 16 and eliminating any gap between upper insulating plate 18 and the inner surface of outer can 16, it is possible to prevent high-temperature gas generated from electrode assembly 14 in the event of an abnormality from directly hitting groove portion 22. As a result, breakage of the side portions of outer can 16 is effectively prevented, and smooth exhaust from the safety valve of sealing body 17 can be achieved.

[0040] The above-described embodiment can be modified as appropriate within the scope of the present disclosure. For example, while the above-described embodiment illustrates an outer can 16 having a recess 30 formed on its inner circumferential surface into which the upper insulating plate 18 fits, an outer can without the recess 30 can also be used. In this case, an upper insulating plate having a diameter larger than the inner diameter of the outer can is used. The upper insulating plate is press-fitted into the outer can and is disposed in close contact with the inner circumferential surface of the outer can. The side surface of the upper insulating plate along the thickness direction must abut against the inner circumferential surface of the outer can so that no gap is formed between the inner circumferential surface of the outer can and the upper insulating plate.

[0041] The present disclosure will be further described by the following embodiments. Configuration 1: A battery comprising an electrode assembly, an electrolyte, a cylindrical outer can with a bottom that accommodates the electrode assembly and the electrolyte, and a sealing body that closes the opening of the outer can, wherein a grooved portion for supporting the sealing body is formed in the outer can, and further comprising an upper insulating plate provided between the electrode assembly and the grooved portion of the outer can, wherein the upper insulating plate is press-fitted into the outer can and is disposed in close contact with the inner surface of the outer can. Configuration 2: A battery comprising an electrode assembly, an electrolyte, a cylindrical outer can with a bottom that accommodates the electrode assembly and the electrolyte, and a sealing body that closes the opening of the outer can, wherein a grooved portion for supporting the sealing body is formed in the outer can, and further comprising an upper insulating plate provided between the electrode assembly and the grooved portion of the outer can, wherein a recessed portion into which an edge of the upper insulating plate fits is formed in the inner surface of the outer can, and the upper insulating plate is fixed in the recessed portion. Configuration 3: The battery according to Configuration 2, wherein the outer can has a cylindrical shape with a bottom, and the upper insulating plate has a diameter larger than the inner diameter of the outer can at a portion where the recessed portion is not present.Configuration 4: The battery according to Configuration 2 or 3, wherein the depth of the recessed portion of the outer can is less than 50% of the thickness of the outer can.Configuration 5: The battery according to any one of Configurations 1 to 4, wherein the upper insulating plate is composed primarily of a curable resin.Configuration 6: The battery according to any one of Configurations 1 to 4, wherein the upper insulating plate is composed primarily of a thermoplastic resin having a melting point of 200°C or higher.

[0042] REFERENCE SIGNS LIST 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Recessed portion

Claims

1. A battery comprising an electrode body, an electrolyte, a bottomed cylindrical outer can containing the electrode body and the electrolyte, and a sealing body that closes the opening of the outer can, wherein a grooved portion for supporting the sealing body is formed in the outer can, and further comprising an upper insulating plate provided between the electrode body and the grooved portion of the outer can, wherein the upper insulating plate is press-fitted into the outer can and positioned in close contact with the inner surface of the outer can.

2. A battery comprising an electrode body, an electrolyte, a bottomed cylindrical outer can containing the electrode body and the electrolyte, and a sealing body that closes the opening of the outer can, wherein a grooved portion for supporting the sealing body is formed in the outer can, and further comprising an upper insulating plate provided between the electrode body and the grooved portion of the outer can, wherein a recessed portion into which an end of the upper insulating plate fits is formed on the inner surface of the outer can, and the upper insulating plate is fixed to the recessed portion.

3. The battery according to claim 2, wherein the exterior can has a cylindrical shape with a bottom, and the upper insulating plate has a diameter larger than the inner diameter of the exterior can at a portion where the recessed portion does not exist.

4. The battery according to claim 2, wherein the depth of the recess in the outer can is less than 50% of the thickness of the outer can.

5. The battery according to any one of claims 1 to 4, wherein the upper insulating plate is composed primarily of a hardening resin.

6. The battery according to any one of claims 1 to 4, wherein the upper insulating plate is composed primarily of a thermoplastic resin having a melting point of 200°C or higher.

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