Power storage device

Abstract

This power storage device (10) is provided with: an electrode body (14) which is obtained by winding a positive electrode (11), a negative electrode (12), and a separator (13); a polygonal tubular case (20) which has a polygonal tubular part and an opening provided at one end of the tubular part, and which houses the electrode body (14) and an electrolytic solution; and a polygonal sealing body (30) which closes the opening of the case (20). A groove-shaped thin part (34A) which releases a gas inside the case (20) to the outside is provided at a corner of a bottom surface part (20B) of the case (20) or at a corner of the sealing body (30).

Description

Power storage device

[0001] The present disclosure relates to an electricity storage device.

[0002] Prismatic batteries are a well-known form of power storage device. Prismatic batteries have a rectangular cylindrical case (see, for example, Patent Document 1). Prismatic batteries are space-efficient and can be stably stored within a storage space. Therefore, prismatic batteries are suitable for making electrical devices smaller and thinner.

[0003] Patent No. 3709134

[0004] The use of the above-mentioned prismatic batteries certainly improves space efficiency, but the reliability of these batteries must be further improved in order to achieve high capacity and high output.

[0005] Therefore, an object of the present disclosure is to provide a power storage device that can improve reliability.

[0006] The energy storage device according to the present disclosure comprises an electrode body in which a positive electrode, a negative electrode, and a separator are wound together, a polygonal cylindrical case having a polygonal cylindrical portion and an opening at one end of the cylindrical portion, and containing the electrode body and an electrolyte solution, and a polygonal sealing body that closes the opening of the case, and is characterized in that an explosion-proof mechanism that releases gas inside the case to the outside is provided at a corner of the bottom of the case or at a corner of the sealing body.

[0007] According to the power storage device of the present disclosure, reliability can be improved.

[0008] 1 is a schematic cross-sectional view showing an electric storage device according to an embodiment; FIG. 2 is an exploded perspective view showing an electric storage device according to an embodiment; FIG. 3 is a plan view showing a first explosion-proof mechanism; FIG. 4 is an exploded perspective view showing an electric storage device according to another embodiment; FIG. 5 is an exploded perspective view showing an electric storage device according to another embodiment; FIG. 6 is a plan view showing another example of the first explosion-proof mechanism; FIG. 7 is a plan view showing another example of the first explosion-proof mechanism; FIG. 8 is a plan view showing another example of the first explosion-proof mechanism; FIG. 9 is a plan view showing another example of the first explosion-proof mechanism; FIG. 10 is a schematic cross-sectional view showing an electric storage device according to another embodiment; FIG. 11 is a schematic cross-sectional view showing an electric storage device according to another embodiment;

[0009] An example of an embodiment of the present disclosure will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating understanding of the present disclosure, and can be appropriately changed according to the application, purpose, specifications, etc.

[0010] [Electricity Storage Device (End Surface Current Collection Structure)] An electricity storage device 10 as an example of an embodiment will be described with reference to FIGS. 1 to 3 .

[0011] 1, the energy storage device 10 includes a cylindrical electrode assembly 14 in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound with a strip-shaped separator 13 interposed therebetween, an electrolyte (not shown), a polygonal cylindrical case 20 that houses the electrode assembly 14 and the electrolyte, and a polygonal sealing body 30 that closes the opening of the case 20. The energy storage device 10 can improve reliability, as will be described in detail below.

[0012] In this embodiment, the polygonal cylindrical shape is a combination of a rectangular cylindrical case 20 and a rectangular sealing body 30, but the present disclosure is not limited to this. For example, the polygonal shape may be a combination of a triangular cylindrical case and a triangular sealing body, a pentagonal cylindrical case and a pentagonal sealing body, a hexagonal cylindrical case and a hexagonal sealing body, or a parallelogram cylindrical case and a parallelogram sealing body. Note that the same applies to the polygonal shape described below.

[0013] In the following, the description may be made in accordance with the axial direction of the power storage device 10. The description may also be made in accordance with the upper side or lower side in the axial direction.

[0014] The positive electrode 11 has a strip-shaped positive electrode core material and a positive electrode mixture layer formed on at least one surface of the positive electrode core material. A positive electrode core material exposed portion 11A, where the positive electrode core material is not provided with the positive electrode mixture layer, protrudes from the upper end side (one end side in the width direction of the positive electrode 11). The positive electrode core material can be a foil of a metal such as aluminum or an aluminum alloy that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface layer.

[0015] The positive electrode mixture layer includes a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride, and is formed on both sides of the positive electrode core material, for example. The positive electrode active material may be, for example, a lithium transition metal composite oxide.

[0016] The negative electrode 12 may have, for example, a negative electrode core and a negative electrode mixture layer formed on the surface of the negative electrode core, or a metallic lithium foil may be used instead of the negative electrode mixture layer of the negative electrode 12. Alternatively, the negative electrode 12 may have a negative electrode core, and lithium metal may be deposited on the surface of the negative electrode core upon charging. The negative electrode 12 has a negative electrode core exposed portion 12A at one end in the width direction of the negative electrode core where no negative electrode mixture layer (or metallic lithium foil) is formed.

[0017] When the negative electrode 12 has a negative electrode mixture layer (or metal lithium foil), the negative electrode mixture layer (or metal lithium foil) is preferably formed on both sides of the negative electrode core. The negative electrode core can be made of a foil of a metal that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with such a metal disposed on the surface layer. The negative electrode mixture layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). For example, graphite, a silicon-based material, or the like is used as the negative electrode active material.

[0018] When the negative electrode active material contains a silicon-based material, the silicon-based material can absorb more lithium ions than graphite, and therefore the capacity of the power storage device 10 can be increased. Examples of silicon-based materials include Si, alloys containing Si, and SiO ｘ Si oxide represented by (0.5≦x≦1.6), Li ２ｙ SiO （２＋ｙ） Examples of the Si-based material include a Si-containing material in which fine particles of Si are dispersed in a lithium silicate phase represented by (0<y<2), and a Si-containing material in which fine particles of Si are dispersed in a carbon phase. ｘ In the negative electrode mixture layer, the ratio of the Si-based material to the total mass of the negative electrode active material is preferably 10% by weight or more from the viewpoints of improving battery capacity and suppressing deterioration of charge-discharge cycle characteristics.

[0019] As described above, when a silicon-based material is used as the negative electrode active material of the negative electrode 12, the volume expansion and contraction of the electrode body 14 associated with charging and discharging of the energy storage device 10 increases. Therefore, it is preferable that the separator 13 has an uneven surface. Examples of the uneven surface include aligned protrusions, or multiple grooves formed along the axial direction. This allows the volume expansion and contraction of the electrode body 14 associated with charging and discharging of the energy storage device 10 to be absorbed.

[0020] The electrode assembly 14 is formed into a cylindrical shape by winding the positive electrode 11 and the negative electrode 12 around a winding core (not shown) with the separator 13 interposed therebetween, with the positive electrode core exposed portion 11A and the negative electrode core exposed portion 12A offset so as to protrude in opposite directions in the axial direction. The winding core of this embodiment is cylindrical and formed into a circular shape when viewed from the axial direction, but the present disclosure is not limited thereto. The winding core may be formed into a polygonal shape when viewed from the axial direction, similar to the case 20 and the sealing body 30. For example, the winding core may be a rectangular tube when viewed from the axial direction.

[0021] The electrolyte is a non-aqueous electrolyte and includes 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. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and mixed solvents thereof. The electrolyte salt includes, for example, LiPF ６ Lithium salts such as

[0022] Provided on the upper side of the electrode body 14 are a positive electrode current collector 15 to which the positive electrode core material exposed portion 11A is joined, and an upper insulating plate 17 arranged on the upper side of the positive electrode current collector 15. The positive electrode current collector 15 has a convex portion 15A formed thereon that protrudes upward and passes through a through-hole in the upper insulating plate 17 to be joined to a sealing plate 32 (described later). This electrically connects the positive electrode 11 and the sealing plate 32, and the sealing plate 32 functions as a positive electrode external terminal.

[0023] 2, the upper insulating plate 17 is formed in a circular shape with approximately the same diameter as the electrode body 14 when viewed in the axial direction. As a result, as will be described in detail later, in the event of an abnormality in the energy storage device 10, the upper insulating plate 17 does not obstruct the exhaust of gas in the exhaust path, thereby improving reliability.

[0024] 1 again, provided below the electrode body 14 are a negative electrode current collector 16 to which the negative electrode core material exposed portion 12A is joined, and a lower insulating plate 18 disposed below the negative electrode current collector 16. The negative electrode current collector 16 is formed with a convex portion 16A that protrudes downward, passes through a through-hole in the lower insulating plate 18, and is joined to the inner surface of a bottom portion 20B of a case 20 (described later). This electrically connects the negative electrode 12 and the case 20, and the case 20 functions as a negative electrode external terminal.

[0025] 2, the lower insulating plate 18 is formed in a polygonal shape (a square shape in this embodiment) similar to the bottom surface portion 20B of the case 20 when viewed in the axial direction. As a result, as will be described in detail later, in the event of an abnormality in the energy storage device 10, the lower insulating plate 18 can prevent the gas from being exhausted from the exhaust path, thereby preventing the case 20 from bursting. Note that the lower insulating plate 18 is not necessarily required in the energy storage device of the present disclosure.

[0026] 1 again, the case 20 is a metal container having a polygonal cylindrical portion (a rectangular cylindrical portion in this embodiment) and an opening at the upper end of the cylindrical portion. With this configuration, when an abnormality occurs in the energy storage device 10 and the internal pressure rises, the corner spaces of the case 20, which are the gaps between the electrode body 14 and the cylindrical portion of the case 20, can be used as gas exhaust paths. This makes it possible to form many gas exhaust paths in the event of an abnormality in the energy storage device 10, thereby improving the reliability of the energy storage device 10.

[0027] The opening of case 20 is closed by a sealing body 30, which will be described later. Energy storage device 10 is sealed by laser welding the opening of case 20 to the periphery of sealing body 30. Case 20 also has a bottom surface portion 20B that is polygonal (rectangular in this embodiment) when viewed from the axial direction.

[0028] [Sealing Body] The sealing body 30 is formed in a polygonal shape (a quadrangular shape in this embodiment) when viewed from the axial direction. The sealing body 30 includes a cover plate 31 having a first explosion-proof mechanism at its corners, a sealing plate 32 provided in the center of the cover plate 31 and having a second explosion-proof mechanism, and a gasket 33 provided on the outer periphery of the sealing plate 32. Note that if the first explosion-proof mechanism is provided, the second explosion-proof mechanism does not necessarily have to be provided. In the following, the term "explosion-proof mechanism" is intended to include both the first explosion-proof mechanism and the second explosion-proof mechanism. Note that "the first explosion-proof mechanism is provided at a corner of the sealing body (or case)" means that, when a line is drawn from the center of the sealing plate (or case) to the corner, the first explosion-proof mechanism is located more toward the corner than the center. By providing the first explosion-proof mechanism at the corner, gas can be more easily released through the gap between the corner of the case (tubular portion) and the electrode body. It is also preferable that the gap between the electrode body and the cylindrical portion of the case overlap in the axial direction.

[0029] The cover plate 31 is formed in a polygonal shape (a square shape in this embodiment) when viewed from the axial direction. The periphery of the cover plate 31 is fixed to the opening of the case 20 by laser welding. A groove-shaped thin-walled portion 34A is formed at the corner of the cover plate 31 as a first explosion-proof mechanism that breaks to form an exhaust port in the event of an abnormality in the energy storage device 10 (see FIGS. 2 and 3). The thin-walled portion 34A will be described in detail below.

[0030] A circular ring portion 31A is formed on the underside of the cover plate 31, with the center of the cover plate 31 extending cylindrically toward the inside of the case 20. The sealing plate 32 is disposed on the inner periphery of the circular ring portion 31A with an annular gasket 33 interposed therebetween, and the sealing plate 32 is attached to the cover plate 31 by compressing the gasket 33 through a crimping process that bends the tip of the circular ring portion 31A inward.

[0031] The sealing plate 32 is formed in a circular shape when viewed in the axial direction. The sealing plate 32 has an outer peripheral portion 32A that is fixed to the annular portion 31A of the cover plate 31 by crimping, a central portion 32B formed inside the outer peripheral portion 32A, and a thin-walled portion 32C that serves as a second explosion-proof mechanism and is interposed between the outer peripheral portion 32A and the central portion 32B. The thickness of the thin-walled portion 32C is smaller than the thicknesses of the outer peripheral portion 32A and the central portion 32B, for example. As a result, if an abnormality occurs in the energy storage device 10, the internal pressure increases, and the sealing body 30 is pushed outward from the case 20, the thin-walled portion 32C in the sealing plate 32 will break preferentially, forming an exhaust port in the sealing plate 32.

[0032] 2 and 3 , groove-shaped thin-walled portion 34A serving as a first explosion-proof mechanism is formed along a diagonal line of rectangular sealing body 30. As a result, if an abnormality occurs in power storage device 10, causing the internal pressure to rise and sealing body 30 to be pushed outward from case 20, thin-walled portion 34A will break preferentially, forming an exhaust port in sealing body 30.

[0033] Furthermore, by forming the first explosion-proof mechanism (thin portion 34A) at the corner of sealing body 30, the corner space of case 20 can be used as an exhaust path for gas, and the gas can be exhausted from the first explosion-proof mechanism above the corner space. This allows for the provision of many exhaust ports in the event of an abnormality in power storage device 10, thereby improving the reliability of power storage device 10.

[0034] As shown in FIG. 2 , the upper insulating plate 17, which is closer to the first explosion-proof mechanism, has a smaller surface area extending in a direction perpendicular to the axial direction than the lower insulating plate 18, which is farther from the first explosion-proof mechanism than the upper insulating plate 17 when viewed in the axial direction. The upper insulating plate 17 is formed, for example, in a circular shape. With this configuration, a gap is likely to form between the upper insulating plate 17 and the case 20 in the direction perpendicular to the axial direction. This gap prevents the upper insulating plate 17 from interfering with the gas exhaust path in the event of an abnormality in the energy storage device 10 causing an increase in internal pressure. This improves the reliability of the energy storage device 10.

[0035] On the other hand, the lower insulating plate 18 is formed in a polygonal shape (a quadrilateral shape in this embodiment). With this configuration, if an abnormality occurs in the energy storage device 10 and the internal pressure rises, the lower insulating plate 18 can protect the bottom surface portion 20B of the case 20 from thermal damage in the gas exhaust path, thereby preventing the bottom surface portion 20B from exploding before the first explosion-proof mechanism ruptures. This can improve the operational reliability of the first explosion-proof mechanism. This can improve the reliability of the energy storage device 10.

[0036] Another embodiment (exhaust path) A power storage device 40 as another example of the embodiment will be described with reference to Fig. 4. In the following, the same components as those in the power storage device 10 described above will be described using the same reference numerals, or the description will be omitted.

[0037] In the power storage device 40, instead of the above-described explosion-proof mechanism, a first explosion-proof mechanism is provided on the bottom surface 20B of the case 20. The first explosion-proof mechanism is formed as a groove-shaped thin-walled portion 21A on the bottom surface 20B of the case 20. In this embodiment, the thin-walled portion 21A is formed along a diagonal line of the bottom surface 20B of the rectangular case 20. As a result, if an abnormality occurs in the power storage device 40, causing the internal pressure to increase and pushing the bottom surface 20B of the case 20 outward, the thin-walled portion 21A will break preferentially, forming an exhaust port on the bottom surface 20B of the case 20.

[0038] The lower insulating plate 18, which is closer to the thin-walled portion 21A serving as the first explosion-proof mechanism, has a smaller surface area extending in a direction perpendicular to the axial direction than the upper insulating plate 17, which is farther from the first explosion-proof mechanism than the lower insulating plate 18 when viewed from the axial direction. The lower insulating plate 18 is formed, for example, in a circular shape. This configuration makes it easy for a gap to form between the lower insulating plate 18 and the case 20 in the direction perpendicular to the axial direction. This gap prevents the lower insulating plate 18 from interfering with the gas exhaust path in the event of an abnormality in the energy storage device 40 causing an increase in internal pressure. This improves the reliability of the energy storage device 40.

[0039] On the other hand, the upper insulating plate 17, which is far from the thin-walled portion 21A and serves as the first explosion-proof mechanism, is formed, for example, in a polygonal shape (in this embodiment, a square shape) when viewed from the axial direction. With this configuration, if an abnormality occurs in the energy storage device 40 and the internal pressure rises, the upper insulating plate 17 protects the sealing member 30 from thermal damage caused by the gas in the gas exhaust path. This prevents the sealing member 30 from rupturing before the first explosion-proof mechanism ruptures. This improves the operational reliability of the first explosion-proof mechanism, thereby improving the reliability of the energy storage device 40.

[0040] An electric storage device 50 as another example of the embodiment will be described with reference to Fig. 5. In the following, the same components as those in the electric storage device 10 described above will be described using the same reference numerals or will not be described again.

[0041] In the energy storage device 50, a hollow pipe 22 is disposed in a corner space of the case 20, which is the gap between the electrode body 14 and the case 20. A gap is formed between the upper end of the pipe 22 and the sealing body 30. On the other hand, a gap is formed between the lower end of the pipe 22 and the bottom surface 20B of the case 20.

[0042] With this configuration, if an abnormality occurs in the power storage device 50 and the internal pressure rises, the pipe 22 can be used as a gas exhaust path. This makes it possible to easily ensure an exhaust path in the event of an abnormality in the power storage device 50, thereby improving the reliability of the power storage device 50. A notch may be formed in the axial end of the pipe 22. This notch makes it easy to allow gas to flow into the pipe 22 even if the axial end of the pipe 22 abuts against, for example, the bottom surface portion 20B, the lower insulating plate 18, the upper insulating plate 17, or the sealing body 30.

[0043] In addition, in the power storage device 50, the first explosion-proof mechanism may be a thin portion 34A formed on the cover plate 31 of the sealing body 30, the upper insulating plate 17 may be circular when viewed in the axial direction, and the lower insulating plate 18 may be polygonal when viewed in the axial direction. In addition, in the power storage device 50, the first explosion-proof mechanism may be a thin portion 21A formed on the bottom surface portion 20B of the case 20, the upper insulating plate 17 may be polygonal when viewed in the axial direction, and the lower insulating plate 18 may be circular when viewed in the axial direction.

[0044] Another embodiment (first explosion-proof mechanism) will be described with reference to Figures 6 to 12. Hereinafter, thin-walled portions 34B to 34G formed on cover plate 31 of sealing body 30 will be described, but thin-walled portions 21B to 21G formed on bottom surface 20B of case 20 may also have a similar shape.

[0045] As shown in FIG. 6, groove-shaped thin portions 34B serving as a first explosion-proof mechanism are formed along the diagonal lines of cover plate 31 and the outer periphery of cover plate 31 at the corners of cover plate 31 of rectangular sealing body 30.

[0046] As shown in FIG. 7, groove-shaped thin portions 34C serving as a first explosion-proof mechanism are formed along the outer periphery of the cover plate 31 at the corners of the cover plate 31 of the rectangular sealing body 30.

[0047] As shown in FIG. 8, the groove-shaped thin portion 34D serving as the first explosion-proof mechanism is formed at the corner of the cover plate 31 of the rectangular sealing body 30 so as to have a V-shape when viewed from the center of the cover plate 31.

[0048] 9 , groove-shaped thin-walled portion 34E serving as a first explosion-proof mechanism is formed in an X-shape at a corner of cover plate 31 of rectangular sealing body 30. A portion of thin-walled portion 34E is formed along a diagonal line of cover plate 31.

[0049] 10 , groove-shaped thin-walled portion 34F serving as a first explosion-proof mechanism is formed at a corner of cover plate 31 of rectangular sealing body 30 so as to form a Y shape when viewed from the center of cover plate 31. A portion of thin-walled portion 34F is formed along a diagonal line of cover plate 31.

[0050] As shown in FIG. 11, a groove-shaped thin portion 34G serving as a first explosion-proof mechanism is formed along the outer periphery of the cover plate 31, and the portions along the corners of the cover plate 31 are formed thinner than the other portions.

[0051] As shown in Figure 12, the groove-shaped thin-walled portions 21H serving as the first explosion-proof mechanism are formed at the corners of the bottom surface 20B of the rectangular case 20 so as to form a Y-shape when viewed from the center of the bottom surface 20B, and each thin-walled portion 21H is joined at the center of the bottom surface 20B.

[0052] Another embodiment (electricity storage device (tab structure)) An electricity storage device 60, which is another example of an embodiment, will be described with reference to Fig. 13. In the following, the same components as those in the electricity storage device 10 described above will be described using the same reference numerals, or the description will be omitted.

[0053] The electricity storage device 60 includes a cylindrical electrode assembly 14 formed by winding a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 with a strip-shaped separator 13 interposed therebetween, an electrolyte (not shown), a polygonal cylindrical (rectangular cylindrical in this embodiment) case 20 that houses the electrode assembly 14 and the electrolyte, and a polygonal (rectangular in this embodiment) sealing body 30 that closes the opening of the case 20. An upper insulating plate 17 is provided above the electrode assembly 14. On the other hand, a lower insulating plate 18 is provided below the electrode assembly 14.

[0054] A positive electrode tab 61 extends from the upper end of the electrode body 14. The positive electrode tab 61 is connected to, for example, the center portion of the positive electrode 11 in the longitudinal direction. The positive electrode tab 61 passes through the through-hole in the upper insulating plate 17, extends toward the sealing body 30, and is welded to the underside of the sealing plate 32. In this way, the sealing plate 32 functions as a positive electrode external terminal.

[0055] On the other hand, a negative electrode tab 62 extends from the lower end of the electrode body 14. The negative electrode tab 62 is connected to, for example, the longitudinal end of the negative electrode 12. The negative electrode tab 62 extends toward the bottom surface 20B of the case 20 and is welded to the inside of the bottom surface 20B of the case 20. In this way, the case 20 functions as a negative electrode external terminal.

[0056] In the energy storage device 60, similarly to the energy storage device 10, the first explosion-proof mechanism (thin-walled portion 34A) is formed at a corner of the sealing body 30, and the upper insulating plate 17 is formed in a circular shape with approximately the same diameter as the electrode body 14 when viewed in the axial direction. This improves the reliability of the energy storage device 60. Also, similarly to the energy storage device 40, the first explosion-proof mechanism (thin-walled portion 21A) may be formed at a corner of the bottom surface portion 20B of the case 20, and the lower insulating plate 18 may be formed in a circular shape with approximately the same diameter as the electrode body 14 when viewed in the axial direction. Furthermore, similarly to the energy storage device 50, a pipe 22 may be disposed in a corner space of the case 20, which is a gap between the electrode body 14 and the case 20.

[0057] Another embodiment (electricity storage device (rivet structure)) An electricity storage device 70, which is another example of an embodiment, will be described with reference to Fig. 14. In the following, the same components as those in the electricity storage device 10 described above will be described using the same reference numerals, or the description will be omitted.

[0058] The energy storage device 70 includes a cylindrical electrode assembly 14 formed by winding a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 with a strip-shaped separator 13 interposed therebetween, an electrolyte (not shown), a polygonal cylindrical (square cylindrical in this embodiment) case 71 that accommodates the electrode assembly 14 and the electrolyte, a rivet 72 serving as a positive electrode external terminal provided on the top surface of the case 71, and a polygonal (square in this embodiment) sealing body 75 that closes the opening on the bottom surface of the case 20. A positive electrode current collector 15 and an upper insulating plate 17 are provided above the electrode assembly 14. On the other hand, a negative electrode current collector 16 and a lower insulating plate 18 are provided below the electrode assembly 14. The negative electrode current collector 16, which is joined to the negative electrode core material exposed portion 12A of the negative electrode 12, is electrically connected to the sealing body 75 through the lower insulating plate 18. The outer periphery of sealing body 75 may be joined to the lower opening of case 71 by welding or the like.

[0059] The rivet 72 is made of metal and is fixed to an opening formed in the top surface of the case 71 via an insulating member 73. The positive electrode current collector plate 15 is joined to the bottom surface of the rivet 72 by a positive electrode tab 74, and the rivet 72 functions as a positive electrode external terminal.

[0060] In the energy storage device 70, similarly to the energy storage device 10, the first explosion-proof mechanism (thin portion) is formed at the corner of the sealing body 75, and the upper insulating plate 17 is formed in a circular shape with approximately the same diameter as the electrode body 14 when viewed in the axial direction. This improves the reliability of the energy storage device 60.

[0061] In the energy storage device 70, similarly to the energy storage device 60, instead of the positive electrode current collector 15 and the negative electrode current collector 16, a positive electrode tab that electrically connects the positive electrode 11 and the rivet 72 and a negative electrode tab that electrically connects the negative electrode 12 and the case 71 may be provided.

[0062] It should be noted that the present disclosure is not limited to the above-described embodiments and their variations, and it goes without saying that various modifications and improvements are possible within the scope of the matters described in the claims of the present application.

[0063] 10, 40, 50, 60, 70 Energy storage device, 11 Positive electrode, 11A Positive electrode core material exposed portion, 12 Negative electrode, 12A Negative electrode core material exposed portion, 13 Separator, 14 Electrode body, 15 Positive electrode current collector, 15A Convex portion, 16 Negative electrode current collector, 16A Convex portion, 17 Upper insulating plate, 18 Lower insulating plate, 20 Case, 20B Bottom portion, 21A, 21H, 34A, 34B, 34C, 34D, 34E, 34F, 34G Thin portion (first explosion-proof mechanism), 21H Thin portion (first explosion-proof mechanism), 22 Pipe, 30, 75 Sealing body, 31 Cover plate, 31A Annular portion, 32 Sealing plate, 32A Outer periphery, 32B Central portion, 32C Thin-walled portion (second explosion-proof mechanism), 33 gasket, 56 rivet, 61 positive electrode tab, 62 negative electrode tab, 71 case, 72 rivet, 73 insulating member, 74 positive electrode tab

Claims

1. An electricity storage device comprising: an electrode body in which a positive electrode, a negative electrode, and a separator are wound; a polygonal cylindrical case having a polygonal cylindrical portion and an opening provided at one end of the cylindrical portion, the polygonal cylindrical case containing the electrode body and an electrolyte; and a polygonal sealing body that closes the opening of the case, wherein a corner of a bottom surface of the case or a corner of the sealing body is provided with an explosion-proof mechanism that releases gas inside the case to the outside.

2. An energy storage device as described in claim 1, further comprising a first insulating plate and a second insulating plate respectively arranged on both sides of the electrode body in the axial direction, the first insulating plate being closer to the explosion-proof mechanism than the second insulating plate, and the first insulating plate having a smaller surface area extending in a direction perpendicular to the axial direction than the second insulating plate.

3. The energy storage device according to claim 2, wherein the first insulating plate is circular, and the second insulating plate is polygonal.

4. An electric storage device according to any one of claims 1 to 3, wherein the case has a cylindrical portion extending in the axial direction and the opening at one end of the cylindrical portion, and a hollow pipe is disposed in a corner space between a corner of the cylindrical portion of the case and the electrode body.

5. An energy storage device according to any one of claims 1 to 4, wherein the case has a cylindrical portion extending in the axial direction and the opening at one end of the cylindrical portion, and a corner space between a corner of the case and the electrode body and the explosion-proof mechanism overlap in the axial direction.

6. An electric storage device according to any one of claims 1 to 5, wherein the explosion-proof mechanism has a groove-shaped thin-walled portion formed along a diagonal line of the polygonal shape.

7. An electric storage device according to any one of claims 1 to 6, wherein the explosion-proof mechanism has a groove-shaped thin-walled portion formed along the outer periphery of the polygonal shape.

8. The electricity storage device according to any one of claims 1 to 7, wherein the negative electrode includes a metallic lithium foil.

9. The electricity storage device according to any one of claims 1 to 8, wherein the negative electrode active material of the negative electrode is a silicon-based material containing 10% or more silicon by weight.

10. The electric storage device according to claim 9, wherein the separator has a surface with projections and recesses.

11. An electric storage device according to any one of claims 1 to 10, wherein the electrode body has a polygonal winding core when viewed in the axial direction.

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