Electric power storage device, and method for manufacturing electric power storage device

Abstract

An electric power storage device (10) comprises: a case (15) that has an opening (15b) formed at one end, in a first direction, of a cylindrical portion (15a); an electrode body (14) that is accommodated in the case; and a lid (30) that closes the opening (15b). The lid has an outer peripheral portion (31) that is joined by welding to an opening-side end portion (15c) of the cylindrical portion (15a). The outer peripheral portion (31) has a first side wall portion that is positioned further toward the inside of the case than an inner peripheral surface (22) of the opening-side end portion (15c), a second side wall portion that is positioned further toward the outside of the case than an outer peripheral surface (23) of the opening-side end portion (15c), and a connecting portion that connects the first side wall portion and the second side wall portion. The first side wall portion includes a first abutting portion that abuts the inner peripheral surface (22), and the second side wall portion has a second abutting portion that abuts the outer peripheral surface (23). In the outer peripheral portion (31), a closed space (40) is formed between a region from the first abutting portion to the second abutting portion and the opening-side end portion (15c).

Description

Electricity storage device and method for manufacturing the same

[0001] The present disclosure relates to an electricity storage device and a method for manufacturing an electricity storage device.

[0002] As described in Patent Document 1, a conventional energy storage device includes a cylindrical battery can (case) with a bottom, an electrode assembly disposed within the battery can, and a sealing member fixed to the battery can to close the opening of the battery can. The sealing member includes a cap with a through hole, a sealing plate disposed within the through hole via an inner gasket, and a double-tube portion disposed on the outer periphery of the cap and protruding downward. After the double-tube portion is fitted to the open end of the battery can via an outer gasket, the outer tubular portion of the double-tube portion is crimped radially inward. This configuration reduces the diameter of the case near the opening to form an annular groove, and then places the sealing plate above the groove, eliminating the need to crimp the case to secure the sealing plate. This potentially allows for a higher battery capacity without increasing the battery height.

[0003] International Publication No. 2020 / 111275

[0004] The power storage device described in Patent Document 1 is expected to have improved reliability as a power storage device. However, in anticipation of future use in harsher environments and conditions, power storage devices need to have further improved reliability.

[0005] Therefore, an object of the present disclosure is to provide a highly reliable power storage device.

[0006] The energy storage device according to the present disclosure includes a case having a cylindrical portion and an opening formed at one end of the cylindrical portion in a first direction, an electrode body that is housed in the case together with an electrolyte and includes a first electrode and a second electrode, and a lid that closes the opening, the lid including an outer peripheral portion that is welded to the open-side end of the cylindrical portion, the outer peripheral portion including a first side wall portion that is located inward of the case from the inner peripheral surface of the open-side end and overlaps with the inner peripheral surface, a second side wall portion that is located outward of the case from the outer peripheral surface of the open-side end and overlaps with the outer peripheral surface, and a connecting portion that connects the first side wall portion and the second side wall portion outside the open-side end, the first side wall portion including a first abutting portion that abuts with the inner peripheral surface, and the second side wall portion including a second abutting portion that abuts with the outer peripheral surface, and an enclosed space is formed in the outer peripheral portion between the region from the first abutting portion to the second abutting portion and the open-side end.

[0007] A method for manufacturing an electricity storage device according to the present disclosure includes a case having a cylindrical portion and an opening formed at one end of the cylindrical portion in a first direction, an electrode body that is housed in the case together with an electrolyte and includes a first electrode and a second electrode, and a lid that closes the opening, the lid including an outer circumferential portion that is welded to the open-side end of the cylindrical portion, the outer circumferential portion including a first side wall portion that is located inward of the case from an inner circumferential surface of the open-side end and overlaps with the inner circumferential surface, a second side wall portion that is located outward of the case from the outer circumferential surface of the open-side end and overlaps with the outer circumferential surface, and a connecting portion that connects the first side wall portion and the second side wall portion outside the open-side end, the first side wall portion including a first abutting portion that abuts with the inner circumferential surface, and the second side wall portion including a second abutting portion that abuts with the outer circumferential surface. and a joining step, after the placing step, of joining the outer periphery and the opening side end. The placing step includes a first sealing step of abutting the first abutment portion and the second abutment portion against the opening side end to form a first closed space between the outer periphery and the opening side end, and a second sealing step, after the first sealing step, of moving the lid toward the inside of the case while the first abutment portion and the second abutment portion are in abutment against the opening side end to form a second closed space smaller than the first closed space between the outer periphery and the opening side end. In the second sealing step, the opening side end fills part of the first closed space to form the second closed space.

[0008] According to the present disclosure, the reliability of the peripheral power storage device can be increased.

[0009] 8 is an axial cross-sectional view of an energy storage device according to an embodiment of the present disclosure; FIG. 1A is an enlarged view of part A of FIG. 1A; FIG. 1B is a flowchart showing a manufacturing method of an energy storage device according to an embodiment of the present disclosure; FIG. 1C is a view corresponding to the upper part of FIG. 1A illustrating a lid arrangement preparation step (a) and a first sealing step (b) in a manufacturing method of an energy storage device according to an embodiment; FIG. 1D is a view corresponding to part B of FIG. 1A in an energy storage device according to another embodiment; FIG. 1E is a view corresponding to FIG. 1F in an energy storage device according to another embodiment; FIG. 1G is a view corresponding to a state in which the lid is omitted from FIG. 1B in an energy storage device according to another embodiment; FIG. 1H is a view corresponding to the lower part of FIG. 1A in an energy storage device according to another embodiment; and

[0010] Hereinafter, with reference to the drawings, an embodiment of a power storage device and a method for manufacturing a power storage device according to the present disclosure will be described in detail. Note that the power storage device according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a nonaqueous electrolyte. Hereinafter, a cylindrical nonaqueous electrolyte secondary battery will be described as the power storage device of the embodiment. However, the power storage device according to the present disclosure can be not only a battery but also a capacitor or other various configurations as long as it is a power storage device including a case including a tubular portion having an opening at one end in a first direction, an electrode assembly housed in the case together with an electrolyte solution, and a lid that closes the opening of the case.

[0011] It is anticipated from the beginning that new embodiments will be constructed by appropriately combining the features of the embodiments and variations described below. In the following embodiments, the same components are designated by the same reference numerals in the drawings, and redundant description will be omitted. Furthermore, the drawings include schematic diagrams, and the dimensional ratios of the length, width, height, and other dimensions of each component between different drawings do not necessarily match. In the embodiments shown in FIGS. 1A to 7, the opening side of the case 15 of the cylindrical battery 10 in the axial direction (first direction) is referred to as "top," and the bottom side of the axial direction is referred to as "bottom." That is, the bottom of the case 15 will be described as the bottom end. In the embodiments shown in FIGS. 8 and 9, the opening side of the case 70 of the cylindrical battery 10 in the axial direction (first direction) is referred to as "bottom," and the top panel side of the axial direction is referred to as "top." Furthermore, the present disclosure is not limited to the following embodiments and their variations, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0012] Fig. 1A is an axial cross-sectional view of a battery 10, which is an electricity storage device according to an embodiment of the present invention. Fig. 1B is an enlarged view of part A in Fig. 1A.

[0013] The battery 10 includes a wound electrode assembly 14, a non-aqueous electrolyte solution (not shown), a case 15 that is a metal can, and a lid 30. The wound electrode assembly 14 has a positive electrode, a negative electrode, and a separator, and the positive electrode and negative electrode are spirally wound with the separator interposed between them. The positive electrode, negative electrode, and separator are all in the form of a long, substantially rectangular strip. The non-aqueous electrolyte solution includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. In this embodiment, the positive electrode corresponds to the first electrode, and the negative electrode corresponds to the second electrode.

[0014] The case 15 has a cylindrical portion 15a and an opening 15b formed at the upper end, which is one end of the cylindrical portion 15a in the axial direction. The portion near the upper end of the cylindrical portion extends cylindrically with a smaller diameter than the other portions in the axial direction. Note that the case of the present disclosure does not necessarily have to have a smaller diameter. The upper end of the cylindrical portion 15a is an opening-side end 15c having the opening 15b. The lid 30 is attached to the case 15 so as to close the opening 15b of the case 15.

[0015] The nonaqueous electrolyte is a liquid electrolyte having ion conductivity (e.g., lithium ion conductivity). The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. The battery 10 is preferably a lithium ion battery. The electrolyte salt may be, for example, LiBF ４ , LiPF ６ Examples of the non-aqueous solvent include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine.

[0016] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP). From the viewpoint of suppressing a decrease in the charge-discharge cycle characteristics of a nonaqueous electrolyte secondary battery or improving input characteristics, the nonaqueous electrolyte preferably contains 5% by mass or more of FEC, and more preferably 5% by mass to 15% by mass of FEC, relative to the mass of the nonaqueous electrolyte.

[0017] The positive electrode has a positive electrode core and positive electrode active material layers formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode, or a film with such a metal disposed on the surface. The positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., to the positive electrode core, drying the coating, and then compressing it to form positive electrode active material layers on both sides of the positive electrode core. The positive electrode active material layer may be formed on only one side of the positive electrode core.

[0018] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0019] Examples of conductive agents contained in the positive electrode active material layer include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of binders contained in the positive electrode active material layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, and polyethylene oxide (PEO).

[0020] The negative electrode has a negative electrode core and negative electrode active material layers formed on both sides of the negative electrode core. The negative electrode core can be made of a metal foil, such as copper or a copper alloy, that is stable within the potential range of the negative electrode, or a film with such a metal disposed on the surface. The negative electrode active material layer contains a negative electrode active material and a binder. The negative electrode can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the negative electrode core, drying the coating, and then compressing it to form negative electrode active material layers on both sides of the negative electrode core. The negative electrode active material layer may be formed on only one side of the negative electrode core.

[0021] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials include natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode active material layer may contain a silicon (Si) material as the negative electrode active material. In addition, the negative electrode active material may include a metal other than Si that alloys with lithium, an alloy containing such a metal, or a compound containing such a metal.

[0022] As in the case of the positive electrode 11, the binder contained in the negative electrode active material layer may be a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, but is preferably styrene-butadiene rubber (SBR) or a modified product thereof. In addition to SBR or the like, the negative electrode active material layer may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0023] The separator is a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Preferred materials for the separator include polyolefin resins such as polyethylene and polypropylene, and cellulose. The separator may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13.

[0024] 1A , in the battery 10, insulating plates 18 and 19 are arranged above and below the electrode body 14 in the axial direction. A negative electrode tab 29, which is a conductive member electrically connected to the negative electrode core of the electrode body 14, is led downward through a through-hole formed in the insulating plate 19 and is bent to fit along the inner surface of the bottom of the case 15 and joined to this inner surface. In this way, the case 15, which is electrically connected to the negative electrode, serves as the negative electrode terminal.

[0025] A positive electrode tab 21 electrically connected to the positive electrode core of the electrode body 14 is led out to the upper side through a through-hole formed in the insulating plate 18 and is bent into a substantially U-shape and joined to the lower surface of a positive electrode terminal 50 (described below). The positive electrode tab 21 is a conductive member made of a metal containing aluminum as a main component, or the like.

[0026] As described above, the battery 10 includes the case 15 and the lid 30 that closes the opening 15b of the case 15. The lid 30 includes an outer peripheral portion 31 welded to the opening end 15c of the cylindrical portion 15a, a substantially annular annular plate portion 42 connected to the inner peripheral end of the outer peripheral portion 31, and a substantially truncated conical protrusion 43 connected to the inner peripheral side of the annular plate portion 42 and having a central portion that protrudes outward. The lid 30 is formed by plastic processing a metal plate. Note that, in the present disclosure, the protrusion is effective in suppressing an increase in internal pressure in the storage space that houses the electrode assembly within the case when the case is closed with the lid. However, the protrusion is not necessarily required.

[0027] A through-hole 44 is formed in the center of the disk portion provided at the upper end of the protrusion 43, penetrating in the vertical direction. The positive electrode terminal 50, which is an electrode terminal, is inserted into the through-hole 44 via a cylindrical resin gasket 45, and the positive electrode terminal 50 is attached to the protrusion 43. This positions the gasket 45 between the lid 30 and the positive electrode terminal 50. The positive electrode terminal 50 is formed, for example, by inserting a rivet having a head with a larger outer diameter at one end than the other portions into the through-hole 44 and crimping the other end of the rivet protruding from the through-hole 44 so as to press in the axial direction. An external positive electrode connection lead (not shown) is connected to the top surface of the positive electrode terminal 50 by welding or the like. The positive electrode terminal of the present disclosure does not necessarily have to include a rivet. The terminal constituting the positive electrode terminal may also be a negative electrode terminal.

[0028] 1B , the outer peripheral portion 31 includes a first side wall portion 32 that is a cylindrical portion, a second side wall portion 35 that is a cylindrical portion provided on the outer peripheral side of the first side wall portion 32, and an annular connecting portion 38 that connects the upper ends of the first side wall portion 32 and the second side wall portion 35 to each other.

[0029] The first side wall portion 32 has a substantially S-shaped cross section taken along a plane passing through the central axis of the lid 30. Note that the cross-sectional shape of the first side wall portion in the present disclosure is not limited to an S-shape. The first side wall portion 32 is located inward of the inner circumferential surface 22 of the opening end 15c of the case 15, and has a first abutment portion 33 that is a portion that overlaps with the inner circumferential surface 22. The first abutment portion 33 abuts against the inner circumferential surface 22. Specifically, the first abutment portion 33 abuts against the inner circumferential surface 22 over substantially the entire circumference.

[0030] The second side wall portion 35 has a substantially J-shaped cross section taken along a plane passing through the central axis of the lid 30. Note that the cross-sectional shape of the second side wall portion in the present disclosure is not limited to a J-shape. The lower end of the second side wall portion 35 is slightly inclined downward toward the outer periphery in accordance with the shape of the outer periphery of the case 15. The second side wall portion 35 is located outward of the outer periphery 23 of the opening end 15c of the case 15 and has a second abutment portion 36 that overlaps with the outer periphery 23. The second abutment portion 36 abuts against the outer periphery 23. Specifically, the second abutment portion 36 abuts against the outer periphery 23 over substantially the entire circumference.

[0031] The connecting portion 38 connects the upper end of the first side wall portion 32 and the upper end of the second side wall portion 35 outside the opening end 15c. The inner surface of the connecting portion 38 faces the tip 41 of the opening end 15c and is in contact with the tip 41 along substantially the entire circumference. A closed space 40 is formed on the inner surface of the outer peripheral portion 31 between a region 39 from the first contact portion 33 to the second contact portion 36 and the surface of the opening end 15c. The closed space 40 is provided along the entire circumference on the inner side of the opening end 15c, and is a sealed or substantially sealed space between the opening end 15c and the first side wall portion 32. This eliminates the need for a gasket at the sealing portion between the lid 30 and the case 15, as described below, and improves the reliability of the battery 10.

[0032] The first contact portion 33 and the second contact portion 36 are located on the lower end side, i.e., the other end side, of the tip 41 of the open end 15c of the case 15 in the axial direction of the tubular portion 15a (the vertical direction in FIG. 1A). This allows the lid 30 to be sufficiently pressed into the inner side of the open end 15c. This more reliably prevents the lid 30 from being separated from the case 15.

[0033] Furthermore, a joint G, where the open end 15c of the case 15 and the outer periphery 31 are joined, is located below the closed space 40 in the axial direction of the cylindrical portion 15a. The joint G is the portion where the second side wall 35 and the open end 15c are joined. The joint G is formed in an annular shape along the outer periphery of the case 15 by irradiating the entire outer surface of the second side wall 35 with laser light L, causing portions of the second side wall 35 and the open end 15c to melt and solidify. Because the joint G is formed by laser welding, which is joining using laser light, the open end 15c and the outer periphery 31 can be joined quickly and with high precision. Note that the joint between the open end 15c and the outer periphery 31 is not limited to being formed by laser welding and may be formed by, for example, resistance welding or friction stir welding.

[0034] The connecting portion 38 includes a third contact portion 38a that contacts a tip 41 of the opening-side end portion 15c. The closed space 40 is formed between a region 39 on the inner surface of the outer circumferential portion 31, the region 39 extending from the first contact portion 33 to the third contact portion 38a, and the inner circumferential surface 22 of the opening-side end portion 15c.

[0035] This eliminates the need to form a closed space between the inner surface of the outer peripheral portion 31 and the outer peripheral surface of the opening-side end 15 c, thereby increasing the contact area between the inner surface of the outer peripheral portion 31 and the outer peripheral surface of the opening-side end 15 c and further improving sealing. In addition, laser irradiation can be easily performed on the outer peripheral surface of the outer peripheral portion 31, improving joining workability.

[0036] 3 is a flowchart showing a method for manufacturing battery 10. As shown in FIG. 3, the method for manufacturing battery 10 includes a lid placement preparation step S10, which is a preparation step before placing lid 30 on open end 15 c of case 15, lid placement steps S11 and S12, in which lid 30 is placed on open end 15 c of case 15, and a joining step S13, which follows lid placement steps S11 and S12 and joins outer periphery 31 and open end 15 c. The lid placement steps S11 and S12 include a first sealing step S11 and a second sealing step S12, which will be described later.

[0037] First, in the method for manufacturing the battery 10, before the lid placement preparation step S10, the electrode assembly 14 is housed in the case 15 together with the insulating plates 18 and 19, and in this state, the lower end of the negative electrode tab 20 extending from below the electrode assembly 14 is overlapped with the bottom of the case 15, and the negative electrode tab 20 is joined to the case 15 by laser irradiation or the like from the outside of the bottom. Also, an electrolyte is injected into the case 15 through the opening 15b.

[0038] Then, as shown in FIG. 3( a), in the lid placement preparation step S10, the positive electrode terminal 50 and the gasket 45 are attached to the lid 30, and the upper end of the positive electrode tab 21 extending from above the electrode body 14 is joined to the lower surface of the positive electrode terminal 50 by welding or the like, and the lid 30 is placed apart from the upper side of the case 15.

[0039] 3(b), in a first sealing step S11 of the lid placement step, the first contact portion 33 and the second contact portion 36 are brought into contact with the opening end 15c to form a substantially sealed first closed space 40a between the inner surface of the outer peripheral portion 31 and the opening end 15c. At this time, the volume of the first closed space 40a is defined as V1, and the pressure within the first closed space 40a is defined as P1. Meanwhile, the volume of the first housing space 51a in the case 15, in which the electrode body 14 is housed, is defined as V2, and the pressure within the first housing space 51a is defined as P2.

[0040] Next, after the first sealing step, in the second sealing step S12 of the lid placement step, as shown in FIGS. 1A and 1B , with the first abutment portion 33 and the second abutment portion 36 abutting against the opening-side end 15c, the lid 30 is moved inward of the case 15, and the inner surface of the connecting portion 38 abuts against the opening-side end 15c, forming a closed space 40 as a second closed space smaller than the first closed space 40a between the outer periphery 31 and the opening-side end 15c. In the second sealing step S12, the opening-side end 15c fills a portion of the first closed space 40a, thereby forming the closed space 40. At this time, the volume of the closed space 40 is defined as V1', and the pressure within the closed space 40 is defined as P1'. Meanwhile, the volume of the second space 51b in the case 15 in which the electrode body 14 is accommodated is defined as V2', and the pressure within the second accommodation space 51b is defined as P2'.

[0041] 1A and 1B, the lid 30 is moved inward of the case 15 and fitted to the case 15. Then, the volume ratio (V1 / V1') of the first closed space 40a to the closed space 40 is set to be greater than the volume ratio (V2 / V2') of the first space 51a to the second space 51b ((V1 / V1') > (V2 / V2')). As a result, if the abutment of the first contact portion 33 and the second contact portion 36 with the opening-side end 15c in the first sealing step S11 is considered to be the initial abutment time, P1 can be considered to be approximately equal to P2, so that P1' > P2'. That is, the internal pressure P1' of the closed space 40 shown in FIG. 1A becomes higher than the internal pressure P2' of the second storage space 51b. As a result, when the lid 30 is fitted to the case 15, the high pressure within the closed space 40 prevents the electrolyte within the case 15 from seeping out of the case 15 due to capillary action. More specifically, when forming the joint G by welding, the timing at which the electrolyte seeps into the portion that will become the joint G can be delayed. This makes it easier to weld without electrolyte seeping into the joint G, reducing the risk of holes during welding. As described above, it is easy to increase the pressure within the closed space 40 formed between the outer periphery 31 and the open-side end 15c of the case 15.

[0042] Next, in the joining step S13, as shown in Figures 1A and 1B, laser light is irradiated from the outer periphery of the outer periphery 31 to join the outer periphery 31 and the opening side end 15c, thereby forming the battery 10.

[0043] The above-described battery 10 and its manufacturing method make it easy to increase the pressure in the closed space 40 between the outer periphery 31 and the open end 15c of the case 15, thereby preventing electrolyte from seeping out of the case 15 when the lid 30 is attached to the open end 15c. This prevents welding defects, thereby improving the reliability of the battery 10. Furthermore, even if the closed space 40 cannot be completely sealed, a high internal pressure similar to that of the closed space 40 can be maintained for a certain period of time. This is thought to delay the leakage of electrolyte from the case 15 to the outside of the case 15 due to capillary action when the lid 30 is fitted to the case 15. This also reduces poor welding holes.

[0044] In the configuration of this example, the closed space 40 is formed between the outer periphery 31 and the inner circumferential surface of the open end 15c of the case 15. Alternatively, a configuration in which a closed space is formed between the outer periphery and the outer circumferential surface of the open end of the case may be used. However, from the viewpoint of suppressing the seepage of the electrolyte into the joint, the configurations shown in Figures 1A to 3 are more effective because they make it easier to suppress the seepage of the electrolyte on the inner circumferential side of the open end 15c.

[0045] 4 is a view corresponding to part B in FIG. 1A of a battery according to another embodiment. In this configuration, a positive electrode terminal 50 is inserted into a through-hole 44 formed in the lid 30, and a first gasket 45a and a second gasket 45b, which are separated in the axial direction, are disposed between the lid 30 and the positive electrode terminal 50. The first gasket 45a is disposed above the second gasket 45b. A portion of the first gasket 45a enters the through-hole 44 and is interposed between the inner circumferential surface of the through-hole 44 and the outer circumferential surface of the positive electrode terminal 50. The lower surface of the first gasket 45a and the upper surface of the second gasket 45b are in contact with each other.

[0046] According to the configuration of this example, the upper first gasket 45a is placed from above the lid 30, and the lower second gasket 45b is placed from below the lid 30, which improves the workability of providing the gaskets between the lid 30 and the positive electrode terminal 50. In this example, other configurations and functions are the same as those of the configurations in Figures 1A to 3. The gasket of the present disclosure does not necessarily have to be divided into the first gasket 45a and the second gasket 45b.

[0047] FIG. 5 is a view corresponding to FIG. 1B of a secondary battery according to another embodiment. In this configuration, a flange-shaped protrusion 15d is formed around the entire periphery of the inner circumferential surface 22 of the open end 15c of the case 15. For example, the protrusion 15d can be formed by forming a groove inward on the outer circumferential surface of the open end 15c by spinning or the like. The first abutment portion 33 of the first side wall portion 32 provided on the outer periphery 31 of the lid 30 abuts against the protrusion 15d. The protrusions 15 may be arranged intermittently in the circumferential direction of the case.

[0048] Furthermore, the first abutment portion 33 is provided on the lower end side, which is the other end side of the protrusion 15d in the axial direction. A part of the first side wall portion 32, which has the first abutment portion 33 and is formed in an annular mountain shape toward the outer periphery, is positioned so that the protrusion 15d and an apex 34 overlap when viewed in the axial direction. As a result, when the lid 30 is fitted with the opening-side end portion 15c, the protrusion 15d and the apex 34 engage in the axial direction, thereby more reliably preventing the lid 30 from separating from the case 15.

[0049] Furthermore, when the direction perpendicular to the axial direction is the second direction, i.e., the horizontal direction (the radial direction of the battery 10), a flat surface 38b extending in the horizontal direction is formed on the outer surface of the connecting portion 38. This allows the external negative electrode connection lead 60 constituting the battery pack to be joined to the flat surface 38b by welding or the like. This makes it easier to provide the joint between the external negative electrode connection lead 60 and the case 15 and the joint between the positive electrode terminal and the external positive electrode connection lead on the same side in the axial direction. In this example, the other configurations and functions are similar to those of FIGS. 1A to 3.

[0050] Alternatively, a protrusion may be formed on the outer peripheral surface of the open end of the case, and a second abutment portion of the second side wall of the lid may abut against the protrusion. Alternatively, the second abutment portion may be provided axially lower than the protrusion, and a portion of the second side wall having the second abutment portion may be positioned so as to overlap the protrusion as viewed in the axial direction. This configuration is effective when a lid is used in which a closed space is formed between the outer peripheral portion and the outer peripheral surface of the open end of the case, because it facilitates engagement between the outer peripheral portion and the protrusion.

[0051] FIG. 6 is a diagram of a secondary battery according to another embodiment, with the lid omitted from FIG. 1B . In this example, similar to FIG. 5 , a protrusion 15d is formed on the inner circumferential surface 22 of the open end of the case 15. A sealant 61 is applied, for example, to the inner circumferential surface 22, distal to the protrusion 15d. A first abutment portion on the outer periphery of the lid abuts against the sealant 61. Examples of the sealant 61 include blown asphalt (called pitch) dissolved in mineral oil, and rubber such as butyl rubber. By providing the sealant 61 above the protrusion 15d, the sealant 61 is prevented from spreading below the protrusion 15d.

[0052] The configuration of this example improves the airtightness between the case 15 and the lid. Other configurations and functions of this example are the same as those of the configurations of Figures 1A to 3 or the configuration of Figure 5. Note that the sealant 61 may be provided in a configuration in which there is no protrusion on the inner circumferential surface 22 of the open-side end 15c of the case 15, as in the configuration of Figure 1B. Furthermore, the sealant 61 may be provided on the outer circumferential surface of the open-side end 15c, at a portion where the second abutment portion abuts.

[0053] 7 is a view corresponding to FIG. 1B of a secondary battery according to another embodiment. In this configuration, the tip of the opening end 15c of the case 15 is folded back inward along the entire circumference into a generally U-shaped cross section, forming a folded portion 15e. Note that the cross-sectional shape of the folded portion according to the present disclosure does not have to be U-shaped. Furthermore, the outer peripheral portion 31 of the lid 30 is pressed into the portion of the case 15 having the folded portion 15e, and the first abutment portion 33 abuts against the inner peripheral surface 22 of the opening end 15c below the folded portion 15e.

[0054] According to the configuration of this example, the closed space 40 formed between the inner surface of the outer peripheral portion 31 and the inner peripheral surface 22 of the open-side end 15c can be made smaller, thereby increasing the pressure within the closed space 40. Furthermore, the strength of the open-side end 15c can be improved. Other configurations and functions of this example are similar to those of the configurations of FIGS. 1A to 3. Alternatively, the tip of the open-side end of the case may be folded back around the entire circumference toward the outer periphery in a generally U-shaped cross section, thereby forming a folded portion. This configuration is effective when using a lid that forms a closed space between the outer periphery and the outer peripheral surface of the open-side end of the case.

[0055] Fig. 8 is a view corresponding to the lower part of Fig. 1A of a secondary battery according to another embodiment. Fig. 9 is an enlarged view of part C in Fig. 8. In the configuration of this example, a case 70 has a cylindrical portion 71 that is open at the bottom, and the top end of the cylindrical portion 71 is closed by a top plate portion (not shown). A through hole is formed in the top plate portion, and a positive electrode terminal is inserted into the through hole via a gasket, so that the positive electrode terminal protrudes from the top surface of the case.

[0056] The opening end 71c, which is the lower end of the cylindrical portion 71, has a cylindrical shape with a smaller diameter than the other portions. A lid 80 having an outer peripheral portion 81 is fitted to the opening end 71c. The configuration of the lid 80 is the same as that of the lid 30 in the configurations of FIGS. 1A to 3, except that the configuration without a through-hole is turned upside down. The negative electrode tab 20 is joined near the center of the upper surface of the lid 80. The outer peripheral portion 81 has a first side wall portion 82 having a first abutting portion 83, a second side wall portion 85 having a second abutting portion 86, and a connecting portion 88 that connects the lower ends of the first side wall portion 82 and the second side wall portion 85. A closed space 89 is formed between the inner surface of the first side wall portion 82 and the inner circumferential surface of the opening end 71c.

[0057] Furthermore, as shown in Figure 9, an annular groove 90 is formed around the entire circumference on the outer surface of the lid 80, thereby forming an annular thin-walled portion 91 on the lid 80. The thin-walled portion 91 forms an easily breakable portion that breaks to discharge gas when high-pressure gas is generated inside the secondary battery. The thin-walled portion for gas discharge may be formed on the lid 30 provided at the upper end in each of the configurations of Figures 1A to 8. In this example, the other configurations and functions are the same as those of Figures 1A to 3.

[0058] The present disclosure is further illustrated by the following embodiments. a case having a cylindrical portion and an opening formed at one end of the cylindrical portion in a first direction; an electrode body housed in the case together with an electrolyte and including a first electrode and a second electrode; and a lid covering the opening, wherein the lid includes an outer circumferential portion welded to the open-side end of the cylindrical portion, wherein the outer circumferential portion includes: a first side wall portion located inward of the case from an inner circumferential surface of the open-side end and overlapping with the inner circumferential surface; a second side wall portion located outward of the case from the outer circumferential surface of the open-side end and overlapping with the outer circumferential surface; and a connecting portion connecting the first side wall portion and the second side wall portion outside the open-side end, wherein the first side wall portion includes a first abutting portion abutting with the inner circumferential surface; and the second side wall portion includes a second abutting portion abutting with the outer circumferential surface, wherein an enclosed space is formed in the outer circumferential portion between the open-side end and a region from the first abutting portion to the second abutting portion. Configuration 2: The energy storage device according to Configuration 1, wherein the first abutment portion and the second abutment portion are located closer to the other end than a tip of the opening-side end in the first direction.Configuration 3: The energy storage device according to Configuration 1 or 2, wherein a joint portion at which the opening-side end and the outer circumferential portion are joined is provided closer to the other end than the closed space in the first direction.Configuration 4: The energy storage device according to any one of Configurations 1 to 3, wherein the connecting portion includes a third abutment portion that abuts against the tip of the opening-side end, and the closed space is formed between a region of the outer circumferential portion from the first abutment portion to the third abutment portion and the inner circumferential surface of the opening-side end.Configuration 5: The energy storage device according to any one of Configurations 1 to 4, wherein a through hole penetrating through in the first direction is formed in the lid, an electrode terminal is inserted into the through hole, and a first gasket and a second gasket separated in the first direction are disposed between the lid and the electrode terminal. Configuration 6: The energy storage device according to any one of Configurations 1 to 5, wherein a protrusion is formed on the inner circumferential surface or the outer circumferential surface of the opening-side end, and the first contact portion or the second contact portion abuts against the protrusion.Configuration 7: The energy storage device of Configuration 6, wherein the first abutment portion or the second abutment portion is provided on the other end side of the protrusion in the first direction, and a portion of the lid having the first abutment portion or the second abutment portion and the protrusion are arranged at a position where they overlap when viewed in the first direction.Configuration 8: The energy storage device of any one of Configurations 1 to 7, wherein, when a direction orthogonal to the first direction is defined as a second direction, a flat surface extending in the second direction is formed on an outer surface of the connecting portion.Configuration 9: The energy storage device of any one of Configurations 1 to 8, wherein a sealant is provided on the inner circumferential surface or the outer circumferential surface of the opening side end portion at a portion where the first abutment portion or the second abutment portion abuts. Configuration 10: A battery comprising: a case having a cylindrical portion and an opening formed at one end of the cylindrical portion in a first direction; an electrode body housed in the case together with an electrolyte and including a first electrode and a second electrode; and a lid closing the opening, wherein the lid includes an outer circumferential portion welded to the open-side end of the cylindrical portion, the outer circumferential portion including: a first side wall portion located inward of the case from an inner circumferential surface of the open-side end and overlapping with the inner circumferential surface; a second side wall portion located outward of the case from the outer circumferential surface of the open-side end and overlapping with the outer circumferential surface; and a connecting portion connecting the first side wall portion and the second side wall portion outside the open-side end, wherein the first side wall portion includes a first abutting portion abutting with the inner circumferential surface; and the second side wall portion includes a second abutting portion abutting with the outer circumferential surface, and wherein the battery comprises: an arrangement step of arranging the lid on the open-side end; and a joining step of joining the outer circumferential portion and the open-side end after the arrangement step. The arranging step includes: a first sealing step of abutting the first abutment portion and the second abutment portion against the opening-side end to form a first closed space between the outer periphery and the opening-side end; and a second sealing step of, after the first sealing step, moving the lid inward of the case with the first abutment portion and the second abutment portion in abutment against the opening-side end to form a second closed space smaller than the first closed space between the outer periphery and the opening-side end, wherein in the second sealing step, the opening-side end fills a part of the first closed space to form the second closed space.

[0059] 10, 10a Battery, 14 Electrode body, 15 Case, 18, 19 Insulating plate, 20 Negative electrode tab, 21 Positive electrode tab, 22 Inner peripheral surface, 23 Outer peripheral surface, 30 Lid, 31 Outer peripheral portion, 32 First side wall portion, 33 First abutment portion, 34 Top portion, 35 Second side wall portion, 36 Second abutment portion, 38 Connecting portion, 38a Third abutment portion, 38b Flat surface, 39 Area, 40 Closed space, 40a First closed space, 41 Tip, 42 Annular plate portion, 43 Protrusion, 44 Through hole, 45 Gasket, 45a First gasket, 45b Second gasket, 50 Positive electrode terminal, 51a First storage space, 51b Second storage space, 60 External negative electrode connection lead, 61 Sealing material, 70 Case, 71 Cylindrical portion, 89 Closed space.

Claims

1. An electricity storage device comprising: a case having a cylindrical portion and an opening formed at one end of the cylindrical portion in a first direction; an electrode body including a first electrode and a second electrode housed in the case together with an electrolyte solution; and a lid covering the opening, wherein the lid includes an outer periphery welded to the open-side end of the cylindrical portion, and the outer periphery includes a first side wall located inward of the case from the inner periphery of the open-side end and overlapping with the inner periphery, a second side wall located outward of the case from the outer periphery of the open-side end and overlapping with the outer periphery, and a connecting portion connecting the first side wall and the second side wall outside the open-side end, wherein the first side wall includes a first abutting portion abutting with the inner periphery, and the second side wall includes a second abutting portion abutting with the outer periphery, and an enclosed space is formed in the outer periphery between the region from the first abutting portion to the second abutting portion and the open-side end.

2. The energy storage device according to claim 1, wherein the first contact portion and the second contact portion are located closer to the other end of the tubular portion than the tip of the opening-side end in the first direction.

3. The energy storage device according to claim 1, wherein the joint where the opening end and the outer periphery are joined is provided closer to the other end of the tubular portion than the closed space in the first direction.

4. The energy storage device according to claim 1, wherein the connecting portion includes a third abutment portion that abuts against the tip of the opening-side end portion, and the closed space is formed between the region of the outer periphery from the first abutment portion to the third abutment portion and the inner periphery of the opening-side end portion.

5. The energy storage device according to claim 1, wherein a through-hole penetrating the lid in the first direction is formed in the lid, an electrode terminal is inserted into the through-hole, and a first gasket and a second gasket separated in the first direction are disposed between the lid and the electrode terminal.

6. The electricity storage device according to claim 1, wherein a protrusion is formed on the inner circumferential surface or the outer circumferential surface of the opening end, and the first contact portion or the second contact portion abuts against the protrusion.

7. The energy storage device according to claim 6, wherein the first contact portion or the second contact portion is provided on the other end side of the protrusion in the first direction, and a part of the lid having the first contact portion or the second contact portion and the protrusion are positioned so as to overlap when viewed in the first direction.

8. The energy storage device according to claim 1, wherein, when a direction perpendicular to the first direction is defined as a second direction, a flat surface extending in the second direction is formed on an outer surface of the connecting portion.

9. The electricity storage device according to claim 1, wherein a sealant is provided on the inner circumferential surface or the outer circumferential surface of the opening end portion at a portion where the first contact portion or the second contact portion contacts.

10. A battery comprising: a case having a cylindrical portion and an opening formed at one end of the cylindrical portion in a first direction; an electrode body housed in the case together with an electrolyte and including a first electrode and a second electrode; and a lid closing the opening, wherein the lid includes an outer periphery welded to the open end of the cylindrical portion, the outer periphery including a first side wall located inward of the case from the inner periphery of the open end and overlapping with the inner periphery, a second side wall located outward of the case from the outer periphery of the open end and overlapping with the outer periphery, and a connecting portion connecting the first side wall and the second side wall outside the open end, wherein the first side wall includes a first abutting portion abutting with the inner periphery, and the second side wall includes a second abutting portion abutting with the outer periphery, and wherein the battery comprises: an arrangement step of arranging the lid on the open end; and a joining step of joining the outer periphery and the open end after the arrangement step. The arranging step includes: a first sealing step of abutting the first abutment portion and the second abutment portion against the opening-side end to form a first closed space between the outer periphery and the opening-side end; and a second sealing step of, after the first sealing step, moving the lid inward of the case with the first abutment portion and the second abutment portion in abutment against the opening-side end to form a second closed space smaller than the first closed space between the outer periphery and the opening-side end, wherein in the second sealing step, the opening-side end fills a part of the first closed space to form the second closed space.

Images