Power storage device

Abstract

This power storage device comprises: an electrode body (14) in which a positive electrode (11), a negative electrode (12), and a separator (13) are wound; a polygonal cylindrical case (20) that has a polygonal cylindrical part and an opening at one end of the cylindrical part, and in which the electrode body (14) and an electrolytic solution are accommodated; and a rectangular sealing body (30) that closes the opening of the case (20). A first holding member (41) is interposed between the case (20) and the upper end portion in the axial direction of the electrode body (14). The first holding member (41) has a wall part (41B) positioned in a corner space between the electrode body (14) and a corner portion of the cylindrical part.

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] While the use of the above-mentioned prismatic batteries certainly improves space efficiency, this type of battery still needs to be made more reliable 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 a holding member is provided between the case and one axial end of the electrode body, and the holding member has a wall portion located in a corner space between the electrode body and a corner of the cylindrical portion.

[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 a partially see-through perspective view showing an electric storage device according to an embodiment; FIG. 3 is a perspective view showing a first holding member according to an embodiment; FIG. 4 is a perspective view showing a second holding member according to an embodiment; FIG. 5 is another perspective view showing the second holding member according to an embodiment; FIG. 6 is a perspective view showing a second holding member according to another embodiment; FIG. 7 is a schematic cross-sectional view showing an electric storage device according to another embodiment; FIG. 8 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 5 .

[0011] 1 and 2 , the energy storage device 10 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 case 20 that houses the electrode assembly 14 and the electrolyte, a polygonal sealing body 30 that closes the opening of the case 20, and holding members (a first holding member 41 and a second holding member 42) that hold both axial ends of the electrode assembly 14. The energy storage device 10 can improve reliability, as will be described in detail below. Note that the first holding member 41 and the second holding member 42 are omitted from FIG. 1 .

[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. Like the case 20 and the sealing body 30, the winding core may be formed into a polygonal shape when viewed from the axial direction. For example, the winding core may be formed into 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 ６Lithium 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 and a first holding member 41 arranged above the positive electrode current collector 15. The positive electrode current collector 15 is formed with a convex portion 15A that protrudes upward and passes through through holes in the upper insulating plate 17 and the first holding member 41 to be joined to a sealing plate 32 described below. This electrically connects the positive electrode 11 and the sealing plate 32, and the sealing plate 32 functions as a positive electrode external terminal. Note that the upper insulating plate 17 is not necessarily required in the energy storage device of the present disclosure.

[0023] 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 and a second holding member 42 arranged 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 through holes in the lower insulating plate 18 and the second holding member 42, and is joined to the inner surface of a bottom portion 20B of a case 20 (described below). This electrically connects the negative electrode 12 and the case 20, and the case 20 functions as a negative electrode external terminal. Note that the lower insulating plate 18 is not necessarily required in the power storage device of the present disclosure.

[0024] [Case] ​​The case 20 is a metal container having a polygonal cylindrical portion and an opening at the upper end of the cylindrical portion (a rectangular cylindrical portion in this embodiment). 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.

[0025] 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 outer 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.

[0026] [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 provided at its corners, a sealing plate 32 provided in the center of the cover plate 31 and having a second explosion-proof mechanism provided thereon, 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" includes 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 30 (or the case 20)" means that when a line is drawn from the center of the sealing body 30 (or the case 20) to the corner, the first explosion-proof mechanism is located more eccentrically toward the corner than toward the center. By providing the first explosion-proof mechanism at the corner, gas can be easily released through the gap between the corner of the case 20 (tubular portion) and the electrode body 14. It is also preferable that the gap between the electrode body 14 and the cylindrical portion of the case 20 overlap in the axial direction.

[0027] The cover plate 31 is formed in a polygonal shape (a quadrangular shape in this embodiment) when viewed in the axial direction. The periphery of the cover plate 31 is fixed to the opening of the case 20 by laser welding.

[0028] 2 , groove-shaped thin-walled portions 34 are formed at the corners 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. In this embodiment, the thin-walled portions 34 are formed along the diagonals of the rectangular sealing body 30. 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 portions 34 will break preferentially, forming an exhaust port in the sealing body 30.

[0029] Furthermore, by forming the first explosion-proof mechanism (thin-walled portion 34) at the corner of the sealing body 30, the corner space of the case 20 can be used as an exhaust path, and exhaust can be made 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 the energy storage device 10, thereby improving the reliability of the energy storage device 10.

[0030] 1 again, a circular ring portion 31A is formed on the underside 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 in which the tip of the circular ring portion 31A is bent 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. As a result, if an abnormality occurs in the energy storage device 10, causing the internal pressure to increase and pushing the sealing body 30 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] [Holding Member] The holding members are provided on both ends inside the case 20, respectively, and hold both axial ends of the electrode body 14. The holding members include a first holding member 41 and a second holding member 42. The first holding member 41 is provided on the upper end side where the above-mentioned explosion-proof mechanism is provided. The second holding member 42 is provided on the lower end side where the explosion-proof mechanism is not provided. In the present embodiment, the first holding member 41 and the second holding member 42 are provided, but the present disclosure is not limited to this. Only the first holding member 41 or only the second holding member 42 may be provided.

[0033] As shown in FIG. 3 , the first holding member 41 is provided at the upper end of the interior of the case 20 and holds the axial upper end of the electrode assembly 14. The first holding member 41 is preferably formed of a non-conductive resin, ceramic, or the like. The first holding member 41 has a flat seat plate portion 41A facing the upper end surface of the electrode assembly 14 and a wall portion 41B connecting the axial upper end side with a corner space in the cylindrical portion of the case 20. The corner space in the case 20 is the gap between the electrode assembly 14 and the case 20. An opening 41C is formed in the center of the seat plate portion 41A for pouring electrolyte. The seat plate portion 41A may also be provided with a through-hole 41E through which the protrusion 15A of the positive electrode current collector plate 15 passes.

[0034] Wall portions 41B are preferably provided in all corner spaces of the cylindrical portion of case 20. Since case 20 of this embodiment has a rectangular shape, it has four corner spaces, and it is preferable that wall portions 41B are provided in each of these corner spaces. Wall portions 41B may be cylindrical with through holes 41F extending in the axial direction. The peripheral surface of wall portion 41B facing electrode body 14 has a curved surface that follows the shape of the outer peripheral surface of electrode body 14, and the surface facing the cylindrical portion of case 20 includes a flat surface that follows the surface of the cylindrical portion.

[0035] The wall portion 41B protrudes downward (toward the electrode body) from the lower surface of the seat plate portion 41A (the surface opposite the surface facing the electrode body 14) and upward from the upper surface of the seat plate portion 41A (the surface opposite the surface facing the electrode body 14 in the axial direction). The upward protruding portion of the wall portion 41B makes it easier to form a gap above the seat plate portion 41A in the case 20. This gap facilitates the movement of gas. Holes or notches may be formed on the outer peripheral surface of the upward protruding portion of the wall portion 41B (particularly the surface toward the center of the seat plate portion 41A). This makes it easier for gas to flow from the through-holes in the wall portion 41B into the gap above the seat plate portion 41A.

[0036] The first holding member 41 suppresses displacement of the electrode body 14 in the case 20, and when an abnormality occurs in the energy storage device 10 causing the internal pressure to rise and the corner space of the case 20, which is the gap between the electrode body 14 and the cylindrical part of the case 20, is used as an exhaust path, the gas can be actively guided through the through-hole in the wall part 41B to the upper end of the interior of the case 20 where an explosion-proof mechanism is provided. This improves the reliability of the energy storage device 10.

[0037] As shown in FIGS. 4 and 5 , the second holding member 42 is located at the lower end of the interior of the case 20 and holds the lower axial end of the electrode assembly 14. The second holding member 42 is preferably formed of a non-conductive resin, ceramic, or the like. The second holding member 42 has a flat seat plate portion 42A facing the lower end surface of the electrode assembly 14 and wall portions 42B provided at the corners of the seat plate portion 42A. The wall portion 42B (the wall portion of the two holding members farther from the explosion-proof mechanism) has a cylindrical portion like the wall portion 42B, but the lower end surface of this cylindrical portion is closed by the seat plate portion 42A. Similarly to the wall portion 42B, the surface of the wall portion 42B facing the electrode assembly 14 is curved to conform to the shape of the outer circumferential surface of the electrode assembly 14, and the surface facing the cylindrical portion of the case 20 includes a flat surface along the surface of the cylindrical portion.

[0038] It is preferable that the wall portions 42B be provided in all of the corner spaces of the case 20. Since the case 20 of this embodiment has a rectangular shape, it has four corner spaces, and it is preferable that a wall portion 42B be formed in each of the corner spaces.

[0039] The second holding member 42 suppresses displacement of the electrode assembly 14 in the case 20. It also protects the lower end of the interior of the case 20, where no explosion-proof mechanism is provided, from gas when an abnormality occurs in the energy storage device 10, causing internal pressure to rise, and the corner spaces of the case 20, which are gaps between the electrode assembly 14 and the case 20, are used as exhaust paths. This prevents the case 20 from exploding before the explosion-proof mechanism is detected. As a result, the operational stability of the explosion-proof mechanism is improved, and the reliability of the energy storage device 10 is enhanced. Note that the cylindrical portion of the wall 42B does not need to be blocked to facilitate gas flow within the case 20. The second holding member 42 may also have a groove like the groove 41D of the first holding member 41, or a portion protruding downward (toward the bottom 20B of the case 20) from the lower surface of the seat plate 42A (the surface opposite the surface facing the electrode assembly 14 in the axial direction).

[0040] As shown in FIG. 6 , a groove 42D may be formed in the underside of the seat plate 42A of the second holding member 42. The groove 42D may be formed, for example, along a diagonal line of the seat plate 42A so as to communicate with the opening 42C and the through-holes of the wall 42B. The groove 42D does not necessarily have to communicate with the opening 42C or the through-holes of the wall 42B. The groove 42D allows gas to be more actively guided on the underside of the seat plate 42A in the case 20. The groove 42D also allows the electrolyte to be actively guided.

[0041] Another embodiment (explosion-proof mechanism on bottom surface) A power storage device 50 as another example of the embodiment will be described with reference to Fig. 7. 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.

[0042] In the power storage device 50, instead of the explosion-proof mechanism provided at the upper end of the power storage device 50 described above, an explosion-proof mechanism is provided at the lower end of the power storage device 50. The explosion-proof mechanism of this embodiment is formed as a groove-shaped thin-walled portion 21 on the bottom surface 20B of the case 20. The thin-walled portion 21 of this embodiment is formed along a diagonal line of the bottom surface 20B of the rectangular case 20. As a result, when an abnormality occurs in the power storage device 50 and the internal pressure increases, pushing the bottom surface 20B of the case 20 outward from the case 20, the thin-walled portion 21 breaks preferentially, forming an exhaust port in the bottom surface 20B of the case 20.

[0043] In the power storage device 50, a first holding member 41 is provided at the lower end where the explosion-proof mechanism is provided, and a second holding member 42 is provided at the upper end where the explosion-proof mechanism is not provided. This allows the reliability of the power storage device 50 to be improved, similar to the power storage device 10 described above.

[0044] 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. 8. 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. Note that the first holding member 41 and the second holding member 42 are omitted in Fig. 7.

[0045] 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.

[0046] A positive electrode lead 61 extends from the upper end of the electrode body 14. The positive electrode lead 61 is connected to, for example, the center portion of the positive electrode 11 in the longitudinal direction. The positive electrode lead 61 passes through a through-hole in the upper insulating plate 17 and 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.

[0047] On the other hand, a negative electrode lead 62 extends from the lower end of the electrode body 14. The negative electrode lead 62 is connected to, for example, a longitudinal end of the negative electrode 12. The negative electrode lead 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.

[0048] In the power storage device 60, similarly to the power storage device 10, an explosion-proof mechanism is provided on the upper end side of the power storage device 60, a first holding member 41 is provided at the upper end inside the case 20, and a second holding member 42 is provided at the lower end inside the case 20. This improves the reliability of the power storage device 60. Also, similarly to the power storage device 50, an explosion-proof mechanism may be provided at the lower end of the power storage device 60, a first holding member 41 is provided at the lower end inside the case 20, and a second holding member 42 is provided at the upper end inside the case 20.

[0049] 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. 9. 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. Note that the first holding member 41 and the second holding member 42 are omitted in Fig. 8.

[0050] 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.

[0051] 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.

[0052] In the power storage device 70, an explosion-proof mechanism is provided in the sealing body 75 of the power storage device 70, a first holding member 41 is provided at the lower end inside the case 20, and a second holding member 42 is provided at the upper end inside the case 20. This improves the reliability of the power storage device 60. Also, in the power storage device 70, similar to the power storage device 60, instead of the positive current collector plate 15 and the negative current collector plate 16, a positive electrode lead that electrically connects the positive electrode 11 and the rivet 72 and a negative electrode lead that electrically connects the negative electrode 12 and the case 71 may be provided.

[0053] 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.

[0054] 10, 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 plate, 15A Convex portion, 16 Negative electrode current collector plate, 16A Convex portion, 17 Upper insulating plate, 18 Lower insulating plate, 20, 71 Case, 20B Bottom portion, 21 Thin portion (explosion-proof mechanism), 30, 75 Sealing body, 31 Cover plate, 31A Ring portion, 32 Sealing plate, 32A Outer periphery, 32B Central portion, 32C Thin portion (second explosion-proof mechanism), 33 Gasket, 34 Thin portion (first explosion-proof mechanism), 41 First holding member, 41A, 42A Seat plate portion, 41B, 42B Wall portion, 41C Opening, 41E through hole, 41F through hole, 42 second holding member, 42D groove portion, 61 positive electrode lead, 62 negative electrode lead, 72 rivet, 73 insulating member, 74 positive electrode tab

Claims

1. an electrode assembly 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, the polygonal cylindrical case containing the electrode body and the electrolyte; the polygonal sealing body that closes the opening of the case; Equipped with a holding member is provided between the case and one axial end of the electrode body, The holding member has a wall portion located in a corner space between the electrode body and a corner portion of the cylindrical portion. Energy storage device.

2. The power storage device according to claim 1, The holding member has a seat plate portion facing an axial end surface of the electrode body, The seat plate portion has the wall portion provided on a corner side of the cylindrical portion, The wall portion has a through hole passing through in the axial direction. Energy storage device.

3. The power storage device according to claim 1 or 2, The holding members are provided on both ends inside the case. Energy storage device.

4. The power storage device according to any one of claims 1 to 3, an explosion-proof mechanism that releases gas inside the case to the outside from one end side of the axial direction of the electrode body; the through-hole in the wall portion of the holding member provided on the other axial end side of the electrode body is blocked; Energy storage device.

5. The power storage device according to claim 2, A groove extending toward the through hole of the wall portion is provided on one surface of the seat plate portion. Energy storage device.

6. The power storage device according to any one of claims 1 to 5, The wall portion protrudes from both sides of the seat plate in the axial direction, In the wall portion, a portion protruding in a direction away from the seat plate has a notch formed on a surface facing the center of the seat plate portion. Energy storage device.

7. The power storage device according to any one of claims 1 to 6, The negative electrode includes a metallic lithium foil. Energy storage device.

8. The power storage device according to any one of claims 1 to 7, The negative electrode active material of the negative electrode is a silicon-based material containing silicon in an amount of 10% by weight or more. Energy storage device.

9. The power storage device according to claim 8, The surface of the separator is uneven. Energy storage device.

10. The power storage device according to any one of claims 1 to 8, The electrode body has a polygonal winding core when viewed in the axial direction. Energy storage device.