Power storage device and manufacturing method for the same

Abstract

To provide a power storage device reduced in costs and improved in workability.SOLUTION: A power storage device 100 disclosed herein includes a case 10 including an electrolyte injection hole 15, and a sealing member 16 sealing the electrolyte injection hole 15. The sealing member 16 includes at least: a resin pedestal part 16b formed integrally with the case 10 so as to continuously cover an inner wall of the electrolyte injection hole 15 and a peripheral part of the electrolyte injection hole 15 on an outer surface 14u of the case 10; and a resin gas permeable membrane 16m heat-welded to the pedestal part 16b at the outside of the case 10 so as to cover the electrolyte injection hole 15.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device and a method for manufacturing the same. [Background technology]

[0002] Conventionally, there has been known an electricity storage device that includes a case, an electrode assembly housed in the case, and a gas permeable membrane provided on the case. Related prior art documents include Patent Documents 1 to 3. For example, Patent Document 1 discloses an electricity storage device that includes a case having a gas vent hole and an alloy valve membrane (alloy gas permeable membrane) that blocks the gas vent hole and selectively allows hydrogen gas to permeate. Patent Document 1 also describes that an amorphous alloy membrane containing Zr and Ni, a Pd-based alloy membrane, or the like can be used as the alloy valve membrane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-228019 [Patent Document 2] Japanese Patent Application Publication No. 2017-010946 [Patent Document 3] International Publication No. 2021 / 117408 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the findings of the present inventors, the alloy valve membrane disclosed in Patent Document 1 generally tends to be expensive in terms of materials, and the installation work to the case can be complicated. Therefore, from the viewpoints of cost reduction and improved workability, a new configuration of electricity storage device is desired. [Means for solving the problem]

[0005] The present invention provides an electricity storage device comprising: a metal case having a through hole; an electrode body housed in the case; and a sealing member that seals the through hole, wherein the sealing member has a resin base portion integrated with the case so as to continuously cover at least the inner wall of the through hole and the peripheral portion of the through hole on the outer surface of the case; and a resin gas-permeable membrane heat-welded to the base portion on the outside of the case so as to cover the through hole.

[0006] The present invention does not require the alloy valve membrane disclosed in Patent Document 1, and can reduce material costs compared to Patent Document 1. Furthermore, in the present invention, a resin base is integrated with the case, and the gas-permeable membrane is heat-welded to the base. This configuration allows the gas-permeable membrane to be easily attached to the case, improving workability. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view schematically illustrating an electricity storage device 100 according to one embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a vertical cross-sectional view schematically showing the vicinity of the electrolyte injection hole in FIG. [Figure 4] FIG. 4 is a view equivalent to FIG. 3 in the sealing step. [Figure 5] FIG. 5 is a perspective view schematically showing the vicinity of the electrolyte injection hole in the sealing step. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the technology disclosed herein will be described below with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of an electricity storage device that does not characterize the technology disclosed herein) can be understood as design matters for a person skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Furthermore, the expression "A to B" indicating a range in this specification means greater than or equal to A and less than or equal to B, and also includes the meanings "preferably greater than A" and "preferably smaller than B."

[0009] <Electricity storage device 100> FIG. 1 is a perspective view of the energy storage device 100. FIG. 2 is a schematic longitudinal cross-sectional view taken along line II-II in FIG. 1. In the following description, the same reference numerals are used to designate components and parts that perform the same functions, and redundant description may be omitted or simplified. In addition, the reference numerals F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, top, and bottom, and the reference numerals X, Y, and Z in the drawings represent the short side direction, the long side direction perpendicular to the short side direction, and the up-down direction of the energy storage device 100, respectively. The up-down direction Z typically coincides with the vertical direction. However, these directions are merely used for the convenience of description and do not limit the installation form of the energy storage device 100 in any way.

[0010] As shown in FIG. 2, the electricity storage device 100 includes a case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, and a sealing member 16. Here, the electricity storage device 100 further includes an electrolyte (not shown). Here, the electricity storage device 100 is a non-aqueous electrolyte secondary battery. The electricity storage device 100 is preferably a lithium ion secondary battery. In this specification, the term "electricity storage device" refers to a device in general that can be repeatedly charged and discharged, and is a concept that encompasses secondary batteries such as lithium ion secondary batteries and nickel-metal hydride batteries, and capacitors such as lithium ion capacitors and electric double layer capacitors.

[0011] The case 10 is a housing that houses the electrode assembly 20 and the electrolyte. As shown in FIG. 1, the case 10 has a flat, bottomed, rectangular parallelepiped (rectangular) outer shape. The material of the case 10 may be the same as that conventionally used, and is not particularly limited. The case 10 is made of metal, and is preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0012] 2, in this embodiment, case 10 includes a bottomed, rectangular (box-shaped) case body 12 having an opening 12h on one surface (here, the upper surface), and a sealing plate (lid) 14 that seals opening 12h of case body 12. Case 10 is integrated by joining (for example, welding) sealing plate 14 to the periphery of opening 12h of case body 12. Case 10 is hermetically sealed.

[0013] 1, the case body 12 has a substantially rectangular bottom surface 12a having a pair of short sides and a pair of long sides, a pair of long side surfaces 12b extending from the pair of long sides of the bottom surface 12a and facing each other, and a pair of short side surfaces 12c extending from the pair of short sides of the bottom surface 12a and facing each other. The bottom surface 12a faces the opening 12h. In a plan view, the area of ​​the long side surfaces 12b is larger than the area of ​​the short side surfaces 12c.

[0014] In this specification, the term "approximately rectangular" refers not only to a perfect rectangular shape (rectangular shape), but also to shapes such as those in which the corners connecting the long and short sides of the rectangle are rounded, or those in which the corners have notches.

[0015] As shown in FIG. 2 , the sealing plate 14 is a plate-shaped member that closes the opening 12h of the case body 12. The sealing plate 14 faces the bottom surface 12a of the case body 12. Here, the sealing plate 14 constitutes the upper wall of the case 10. The sealing plate 14 is generally rectangular in plan view. The sealing plate 14 is provided with an electrolyte injection hole 15, a discharge valve 17, and two terminal outlet holes 18 and 19. The discharge valve 17 is configured to break when the pressure inside the case 10 reaches or exceeds a predetermined value, thereby discharging gas inside the case 10 to the outside. The terminal outlet holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. The terminal outlet holes 18 and 19 each have an inner diameter large enough to insert the positive electrode terminal 30 and the negative electrode terminal 40 before they are attached to the sealing plate 14 (before crimping).

[0016] FIG. 3 is a vertical cross-sectional view schematically showing the vicinity of the electrolyte injection hole 15. The sealing plate 14 has an upper surface 14u and a lower surface 14d. The upper surface 14u side of the sealing plate 14 is outside the case 10, and the lower surface 14d side of the sealing plate 14 is inside the case 10. Although not particularly limited, from the viewpoint of cost reduction and weight reduction, the thickness (plate thickness) Ta of the sealing plate 14 (the surface of the case 10 where the electrolyte injection hole 15 is provided) is preferably 5 mm or less, and more preferably 1 to 5 mm (e.g., 2 mm). As described in more detail below, the thin-walled case 10 as described above is easily deformed by internal pressure, and is therefore particularly prone to battery swelling. Therefore, application of the technology disclosed herein is highly effective.

[0017] The electrolyte injection hole 15 is for injecting electrolyte after the sealing plate 14 is assembled to the case body 12. The electrolyte injection hole 15 is a through-hole that penetrates the sealing plate 14 in the up-down direction Z. In this case, the electrolyte injection hole 15 is provided between the positive electrode terminal 30 and the discharge valve 17 in the long side direction Y. In this case, the electrolyte injection hole 15 has a substantially circular shape in a plan view. After the electrolyte is injected, the electrolyte injection hole 15 is sealed with a sealing member 16. The sealing member 16 will be described later. In this embodiment, the electrolyte injection hole 15 is provided in the sealing plate 14. However, in other embodiments, the electrolyte injection hole 15 may be provided in the case body 12 (for example, in any one of the bottom surface 12a, the long side surface 12b, and the short side surface 12c). The electrolyte injection hole 15 is an example of a through-hole.

[0018] In this specification, the term "approximately circular" is not limited to a perfect circle (true circle), but also includes circular shapes (e.g., ellipses) whose arc curvature varies locally, and other shapes derived from perfect circles and circles.

[0019] The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the long side direction Y (the left end in FIGS. 1 and 2). As shown in FIG. 2, the positive electrode terminal 30 extends from the inside to the outside of the sealing plate 14 through the terminal outlet hole 18. Here, the positive electrode terminal 30 is crimped to the peripheral portion of the sealing plate 14 surrounding the terminal outlet hole 18 by crimping. A crimped portion 30c is formed at the end of the positive electrode terminal 30 on the case body 12 side (the lower end in FIG. 2). The positive electrode terminal 30 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy. Inside the case 10, the positive electrode terminal 30 is electrically connected to the positive electrode tab 23 of the electrode assembly 20 via the positive electrode current collector 50. The positive electrode terminal 30 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90.

[0020] The negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIGS. 1 and 2). As shown in FIG. 2, the negative electrode terminal 40 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 19. Here, the negative electrode terminal 40 is crimped to the peripheral portion of the sealing plate 14 surrounding the terminal lead-out hole 19 by crimping. A crimped portion 40c is formed at the end of the negative electrode terminal 40 on the side of the case body 12 (the lower end in FIG. 2). The negative electrode terminal 40 is preferably made of metal, and more preferably made of copper or a copper alloy, for example. Inside the case 10, the negative electrode terminal 40 is electrically connected to the negative electrode tab 25 of the electrode assembly 20 via the negative electrode current collector 60. The negative electrode terminal 40 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90.

[0021] The electrode assembly 20 is housed inside the case 10. The configuration and shape of the electrode assembly 20 may be the same as conventional ones and are not particularly limited. The number of electrode assemblies 20 housed inside one case 10 is not particularly limited and may be one or two or more (plural). Although not shown, the electrode assembly 20 typically has a positive electrode and a negative electrode. The positive electrode typically has a positive electrode current collector and a positive electrode active material layer fixed to the positive electrode current collector. The negative electrode typically has a negative electrode current collector and a negative electrode active material layer fixed to the negative electrode current collector. The electrode assembly 20 may be housed inside the case 10 covered with a resin insulating sheet (electrode assembly holder).

[0022] Here, the electrode assembly 20 is a wound electrode assembly formed by stacking a strip-shaped positive electrode and a strip-shaped negative electrode with a strip-shaped separator interposed therebetween and winding them in the longitudinal direction around a winding axis. However, in other embodiments, the electrode assembly 20 may be a laminated electrode assembly formed by stacking a plurality of square-shaped (typically rectangular) positive electrodes and a plurality of square-shaped (typically rectangular) negative electrodes in an insulated state. Also, in this embodiment, the electrode assembly 20 is disposed inside the case 10 with the winding axis oriented substantially parallel to the long-side direction Y. However, in other embodiments, the electrode assembly 20 may be disposed inside the case 10 with the winding axis oriented substantially parallel to the up-down direction Z, for example.

[0023] As shown in FIG. 2, a positive electrode tab 23 is provided on the positive electrode of the electrode assembly 20. Here, the positive electrode tab 23 is part of the positive electrode current collector. Here, the positive electrode tab 23 is convex and protrudes from the electrode assembly 20 toward one side in the long side direction Y (the left side in FIG. 2). Here, the positive electrode tab 23 is electrically connected to the positive electrode terminal 30 via a positive electrode current collector 50. In addition, a negative electrode tab 25 is provided on the negative electrode of the electrode assembly 20. Here, the negative electrode tab 25 is part of the negative electrode current collector. Here, the negative electrode tab 25 is convex and protrudes from the electrode assembly 20 toward the other side in the long side direction Y (the right side in FIG. 2). Here, the negative electrode tab 25 is electrically connected to the negative electrode terminal 40 via a negative electrode current collector 60.

[0024] The electrolyte may be the same as conventional ones and is not particularly limited. The electrolyte is typically a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt (electrolyte salt). However, it may also be an aqueous electrolyte containing a water solvent. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The non-aqueous solvent preferably contains a carbonate. In particular, it is preferable that the non-aqueous solvent contains a cyclic carbonate and a chain carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as lithium hexafluorophosphate (LiPF6). The electrolyte may further contain additives as necessary.

[0025] The sealing member 16 is a member that seals the electrolyte injection hole (through-hole) 15. As shown in FIG. 3, the sealing member 16 has a base portion 16b, a gas-permeable membrane 16m, and a heat-sealed portion PF between the base portion 16b and the gas-permeable membrane 16m. From the upper surface (outer surface) 14u of the case 10, a protruding height T1 of the sealing member 16 is preferably smaller than the thickness (average length in the vertical direction Z) of the positive electrode terminal 30 and / or the negative electrode terminal 40. By reducing the protruding height of the sealing member 16, it is possible to prevent the sealing member 16 (particularly the gas-permeable membrane 16m) from interfering with other members and thus damaging or breaking the sealing member 16.

[0026] The base portion 16b is integrated with the case 10. In this embodiment, the base portion 16b is attached to the sealing plate 14 and is integrated with the sealing plate 14. The base portion 16b is attached to the sealing plate 14 so that it cannot be removed. As will be described in detail later in the section on the manufacturing method, in this embodiment, the sealing member 16 is attached to the case 10 (here, the sealing plate 14) by insert molding (integral molding). This increases the adhesion between the case 10 and the base portion 16b, improving the sealing performance and reliability of the sealing member 16. Another advantage is that the structure is simplified, requiring fewer parts. However, in other embodiments, the base portion 16b may be joined to the case 10 by, for example, friction stir welding or the like, or may be bonded to the case 10 via an adhesive layer (adhesive or the like).

[0027] The base 16b is made of resin. The base 16b is preferably made of a resin material that has excellent formability and integration with the case 10, resistance to the electrolyte used (electrolyte resistance), and electrical insulation. Specific examples include polyethylene (PE), polypropylene (PP), polyamide (PA), polyphenylene sulfide (PPS), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), and polyethylene terephthalate (PET). Among these, the base 16b is preferably made of at least one resin material selected from the group consisting of polyethylene (PE), polypropylene (PP), polyamide (PA), and polyphenylene sulfide (PPS). These resins have excellent integration with the metal case 10 and / or the gas-permeable membrane 16m, thereby enhancing the sealing performance and reliability of the sealing member 16. Furthermore, these resins have relatively superior electrolyte resistance compared to, for example, polybutylene terephthalate (PBT) or ABS resin, thereby enhancing the chemical durability of the sealing member 16. The resin material is preferably a thermoplastic resin. The resin material may contain conventionally known additives and fillers such as ceramics.

[0028] 3, the base portion 16b continuously covers at least the inner wall of the electrolyte injection hole (through-hole) 15 and the peripheral edge of the electrolyte injection hole 15 on the upper surface (outer surface) 14u of the case 10 (specifically, the sealing plate 14). Here, the base portion 16b also continuously covers the peripheral edge of the electrolyte injection hole 15 on the lower surface (inner surface) 14d of the case 10 (specifically, the sealing plate 14). That is, the base portion 16b essentially includes a hollow stem 16s that covers the inner wall of the electrolyte injection hole 15 and an outer flange 16f1 that is formed integrally with the stem 16s and covers the peripheral edge of the electrolyte injection hole 15 on the upper surface 14u of the case 10. Here, the base portion 16b further includes an inner flange 16f2 that is formed integrally with the stem 16s and covers the peripheral edge of the electrolyte injection hole 15 on the lower surface 14d of the case 10. The outer flange 16f1 and the inner flange 16f2 also function as locking portions that prevent the pedestal portion 16b from being detached, thereby enhancing the unity between the case 10 and the pedestal portion 16b and improving the sealing performance and reliability of the sealing member 16.

[0029] The shaft portion 16s extends along the electrolyte injection hole 15. In this embodiment, the axis of the shaft portion 16s extends along the vertical direction Z. It is preferable that the shaft portion 16s covers the entire inner wall of the electrolyte injection hole 15. In this embodiment, the shaft portion 16s has a hollow, approximately cylindrical shape. The shaft portion 16s has a through-hole 16h extending along the vertical direction Z on the radially inner side of the shaft portion 16s. The upper end portion of the shaft portion 16s is connected to the outer flange portion 16f1. The lower end portion of the shaft portion 16s, i.e., the end portion opposite to the side where the outer flange portion 16f1 is located, is connected to the inner flange portion 16f2.

[0030] The outer flange 16f1 extends from a first end of the shaft 16s and is disposed outside the case 10. In this embodiment, the outer flange 16f1 extends continuously from the upper end of the shaft 16s and protrudes to the outside of the case 10 through the electrolyte injection hole 15 of the sealing plate 14. In this embodiment, the outer flange 16f1 is molded integrally with the shaft 16s (as a single member). Therefore, there is no clear boundary between the outer flange 16f1 and the shaft 16s. The outer shape of the outer flange 16f1 is annular and conforms to the electrolyte injection hole 15 (see also FIG. 5). The outer flange 16f1 is provided with a heat-sealed portion PF where it is bonded to the gas permeable membrane 16m.

[0031] The inner flange 16f2 extends from the second end of the shaft 16s and is disposed inside the case 10. Here, the inner flange 16f2 extends continuously from the lower end of the shaft 16s and protrudes toward the inside of the sealing plate 14 (toward the electrode body 20). In this embodiment, the inner flange 16f2 is molded integrally with the shaft 16s (as a single member). Therefore, there is no clear boundary between the inner flange 16f2 and the shaft 16s. The outer shape of the inner flange 16f2 is annular and conforms to the electrolyte injection hole 15. Here, the inner flange 16f2 has the same shape as the outer flange 16f1. Here, the outer diameter of the inner flange 16f2 is approximately the same as the outer diameter of the outer flange 16f1. However, the shape or outer diameter of the inner flange 16f2 may differ from that of the outer flange 16f1.

[0032] Although not particularly limited, it is preferable that at least one of the peripheral portion (portion where the outer flange 16f1 is provided) of the electrolyte injection hole (through hole) 15 on the upper surface (outer surface) 14u of the case 10 and the peripheral portion (portion where the inner flange 16f2 is provided) of the electrolyte injection hole (through hole) 15 on the lower surface (inner surface) 14d of the case 10 be roughened. This can further improve the adhesion between the case 10 and the base portion 16b, and can improve the sealing performance and reliability of the sealing member 16. From the viewpoint of achieving this effect at a high level, it is more preferable that the roughening be formed continuously in the circumferential direction of the electrolyte injection hole (through hole) 15.

[0033] The gas-permeable membrane 16m is a breathable membrane that covers the electrolyte injection hole (through-hole) 15 on the outside of the case 10. Air can pass between the inside and outside of the case 10 through the gas-permeable membrane 16m. The gas-permeable membrane 16m is configured to be impermeable to liquids (e.g., moisture and nonaqueous electrolyte) but permeable to vapor derived from the nonaqueous electrolyte (e.g., hydrocarbon gases such as methane gas and ethane gas, carbon dioxide, hydrogen, etc.). According to the findings of the inventors, in the electricity storage device 100, the nonaqueous electrolyte may decompose due to, for example, temperature degradation or repeated charge / discharge cycles, generating gas inside the case 10. Therefore, by providing the gas-permeable membrane 16m as in the technology disclosed herein, the gasified nonaqueous electrolyte can be released, thereby suppressing battery swelling. As a result, the thickness of the case 10 can be reduced, resulting in lower costs and a lighter weight. Furthermore, by attaching the gas-permeable membrane 16m to the electrolyte injection hole 15, there is no need to drill any other holes, improving workability and productivity. The gas-permeable membrane 16m preferably has a higher permeability to vapor derived from the non-aqueous electrolyte than to water vapor, and more preferably is configured to be impermeable to water vapor.

[0034] Although details will be described later in the section on the manufacturing method, in this embodiment, the gas permeable membrane 16m is heat-welded to the base portion 16b so as to cover the electrolyte injection hole (through-hole) 15. By employing heat welding, the gas permeable membrane 16m can be easily attached to the case 10, improving workability. In addition, the configuration of the sealing member 16 can be simplified. In this specification, the term "membrane" refers to a structure that extends in a planar shape. The thickness of the "membrane" is typically 1000 μm or less, and may be, for example, 500 μm or less, or 250 μm or less.

[0035] The gas-permeable membrane 16m is made of a resin. The gas-permeable membrane 16m is preferably made of a resin material that has excellent thermal weldability to the base portion 16b, excellent permeability to vapor derived from the nonaqueous electrolyte, resistance to the electrolyte used (electrolyte resistance), and electrical insulation. Specific examples include polyethylene (PE), polypropylene (PP), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE). Among these, the gas-permeable membrane 16m is preferably made of at least one resin material selected from the group consisting of polyethylene (PE) and polytetrafluoroethylene (PTFE). Examples of commercially available PTFE gas-permeable membranes 16m include TEMISH (registered trademark) manufactured by Nitto Denko Corporation and POREFLON (registered trademark) manufactured by Sumitomo Electric Industries, Ltd. The PE gas-permeable membrane 16m may be a nonwoven fabric commercially available as a moisture-permeable waterproof sheet. The gas-permeable membrane 16m may be made of the same resin material as the base portion 16b. The gas-permeable membrane 16m may have a lower melting point than the resin material constituting the base portion 16b.

[0036] The gas permeable membrane 16m is fixed to the base portion 16b (more specifically, the outer flange portion 16f1) via a heat-sealed portion PF, which will be described later. The gas permeable membrane 16m here has a substantially circular shape in a plan view (see also FIG. 5). The outer diameter of the gas permeable membrane 16m is larger than the diameter of the electrolyte injection hole 15. The gas permeable membrane 16m covers the upper side of the electrolyte injection hole 15 and further extends to the periphery of the electrolyte injection hole 15 on the upper surface 14u of the sealing plate 14.

[0037] The heat-sealed portion PF is a joining portion between the base portion 16b (specifically, the outer flange portion 16f1) and the gas-permeable membrane 16m. The heat-sealed portion PF enables the gas-permeable membrane 16m to be stably fixed to the base portion 16b, improving adhesion. The heat-sealed portion PF is provided in the portion where the outer flange portion 16f1 and the gas-permeable membrane 16m overlap in a plan view. Here, the heat-sealed portion PF is provided on the outer periphery of the annular outer flange portion 16f1. The heat-sealed portion PF has an annular shape in a plan view. The heat-sealed portion PF typically has a melting mark formed when the resin melts and solidifies.

[0038] <Method of manufacturing the electricity storage device 100> The above-described power storage device 100 can be manufactured by a manufacturing method including, for example, an integration step (step S1), a preparation step (step S2), a liquid injection step (step S3), and a sealing step (step S4). The rest of the manufacturing process may be the same as conventional methods. Furthermore, the manufacturing method disclosed herein may further include other steps at any stage. Each step will be described below.

[0039] The integration step (step S1) involves preparing a metal case 10 having an electrolyte injection hole (through-hole) 15, and integrating a resin base 16b with the case 10 so as to continuously cover at least the inner wall of the electrolyte injection hole (through-hole) 15 and the periphery of the electrolyte injection hole (through-hole) 15 on the outer surface of the case 10. This allows the base 16b to be firmly attached to the case 10. In a preferred embodiment, the base 16b is integrated with the case 10 (e.g., the sealing plate 14) by insert molding (integral molding). This makes it easy to stably attach the base 16b to the case 10 (e.g., the sealing plate 14) even when the thickness Ta (see FIG. 3 ) of the case 10 (e.g., the sealing plate 14) is thin, e.g., 5 mm or less. This also improves adhesion between the case 10 and the base 16b, improving the sealing performance and reliability of the sealing member 16. Furthermore, the simple structure reduces the number of parts, leading to lower costs.

[0040] The preparation step (step S2) is a step of preparing an assembly including the case 10 with the base portion 16b integrated therewith and the electrode body 20 housed in the case 10. Specifically, for example, first, the electrode body 20 is prepared, and the positive electrode current collector 50 is attached to the positive electrode tab 23 of the electrode body 20, and the negative electrode current collector 60 is attached to the negative electrode tab 25. Next, the sealing plate 14 with the base portion 16b attached, the positive electrode terminal 30, and the negative electrode terminal 40 are prepared, and the positive electrode terminal 30, the negative electrode terminal 40, the positive electrode current collector 50, and the negative electrode current collector 60 are attached to the sealing plate 14. In this way, the sealing plate 14, the positive electrode terminal 30, the negative electrode terminal 40, and the electrode body 20 are integrated together. Next, the case body 12 is prepared, the electrode body 20 integrated with the sealing plate 14 is housed in the internal space of the case body 12, and the opening 12h of the case body 12 is sealed with the sealing plate 14. The sealing can be performed by welding, for example, laser welding. In this manner, an assembly is prepared.

[0041] The liquid injection step (step S3) is a step of injecting the electrolyte into the case 10 through the electrolyte injection hole (through-hole) 15. In a preferred embodiment, the injection is performed using a conventionally known electrolyte injection device (not shown) that includes a liquid injection nozzle for injecting the electrolyte, an electrolyte reservoir communicating with the liquid injection nozzle, and a liquid delivery means (e.g., a pressure pump) for delivering the electrolyte from the electrolyte reservoir to the liquid injection nozzle. In this case, the liquid injection nozzle is inserted into the electrolyte injection hole 15 to inject the electrolyte, and the liquid injection nozzle is then removed from the electrolyte injection hole 15 after the injection. However, in other embodiments, the liquid injection may be performed using, for example, a dispenser or the like.

[0042] The sealing step (step S4) is a step of thermally welding a resin gas-permeable membrane 16m to the base portion 16b on the outside of the case 10 along the radial direction of the electrolyte injection hole (through-hole) 15 to close the electrolyte injection hole (through-hole) 15. In this embodiment, at least the gas-permeable membrane 16m (preferably the gas-permeable membrane 16m and the outer flange portion 16f1 of the base portion 16b) is melted on the outside of the case 10 (here, on the upper surface 14u of the sealing plate 14) to bond the gas-permeable membrane 16m to the base portion 16b. By employing thermal welding, the gas-permeable membrane 16m can be attached to the case 10 more easily than in the past, improving workability and productivity. Furthermore, the configuration of the sealing member 16 can be simplified.

[0043] The means for melting the gas permeable membrane 16m and / or the base portion 16b is not particularly limited. One example is a contact-type heating means in which a heating medium is brought into direct contact with the overlapping portion of the gas permeable membrane 16m and the base portion 16b on the outside of the case 10. This makes it easier to locally melt and flow at least the gas permeable membrane 16m. Examples of contact-type heat treatment means include heat pressing, ultrasonic heating, and impulse welding. In a preferred embodiment, the gas permeable membrane 16m and / or the base portion 16b are melted by heat pressing. However, the heat treatment means may also be a non-contact heat treatment means such as laser heating.

[0044] FIG. 4 is a view corresponding to FIG. 3 in this step, and FIG. 5 is a perspective view schematically showing the vicinity of the electrolyte injection hole 15. As shown in FIGS. 4 and 5, in this embodiment, first, on the upper surface 14u of the case 10 (here, the sealing plate 14), the gas permeable membrane 16m is placed on the outer flange 16f1 of the base portion 16b. The outer flange 16f1 and the gas permeable membrane 16m have approximately the same outer shape. As shown in FIG. 5, the gas permeable membrane 16m is circular, and the outer flange 16f1 is annular.

[0045] Next, as shown in FIG. 4, a heated annular metal plate (heating medium) HP is pressed from above against the outer periphery of the gas permeable membrane 16m to perform heat pressing. The temperature of the metal plate HP is preferably set to a temperature equal to or higher than the melting point of the resin material constituting the gas permeable membrane 16m (e.g., melting point + 5°C or higher) so that the gas permeable membrane 16m is easily melted. The temperature of the metal plate HP is more preferably set to a temperature equal to or higher than the melting point of the resin material constituting the outer flange portion 16f1 (e.g., melting point + 5°C or higher). In this manner, the gas permeable membrane 16m is heat-welded to the base portion 16b, forming a heat-welded portion PF at the interface between the gas permeable membrane 16m and the base portion 16b, and sealing the electrolyte injection hole (through-hole) 15.

[0046] <Uses of the electricity storage device 100> The electricity storage device 100 can be used for various purposes, and can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, a truck, etc. The type of vehicle is not particularly limited, and examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

[0047] Although the preferred embodiment of the present invention has been described above, the above embodiment is merely an example. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modifications, or to add other modifications to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0048] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: An electricity storage device comprising: a metal case having a through hole; an electrode assembly housed in the case; and a sealing member that seals the through hole, wherein the sealing member has a resin base portion integrated with the case so as to continuously cover at least the inner wall of the through hole and the peripheral portion of the through hole on the outer surface of the case; and a resin gas-permeable membrane heat-welded to the base portion on the outside of the case so as to cover the through hole. Item 2: The electricity storage device according to item 1, wherein the base portion further continuously covers a peripheral portion of the through-hole on the inner surface of the case. Item 3: The electricity storage device according to item 1 or 2, wherein at least one of the peripheral edge of the through hole on the outer surface of the case and the peripheral edge of the through hole on the inner surface of the case is roughened. Item 4: The electricity storage device according to Item 3, wherein the roughened surface is formed continuously in the circumferential direction of the through hole. Item 5: The electricity storage device according to any one of Items 1 to 4, wherein the thickness of the surface of the case where the through holes are provided is 5 mm or less. Item 6: The electricity storage device according to any one of Items 1 to 5, wherein the base is made of at least one resin material selected from the group consisting of polyethylene, polypropylene, polyamide, and polyphenylene sulfide. Item 7: The electricity storage device according to any one of Items 1 to 6, wherein the gas-permeable film is made of at least one resin material selected from the group consisting of polyethylene and polytetrafluoroethylene. Item 8: A method for manufacturing an electricity storage device, comprising: an integration step of preparing a metal case having a through hole, and integrating a resin base with the case so as to continuously cover at least the inner wall of the through hole and the peripheral portion of the through hole on the outer surface of the case; a preparation step of preparing an assembly including the case with the base integrated therewith and an electrode body housed in the case; and a sealing step of heat-welding a resin gas-permeable membrane to the base on the outside of the case along the radial direction of the through hole, thereby sealing the through hole. Item 9: The manufacturing method according to Item 8, further comprising, after the preparing step, a liquid injection step of injecting an electrolyte into the case through the through-hole. Item 10: The manufacturing method according to Item 8 or 9, wherein in the integration step, the base portion is integrated with the case by insert molding. [Explanation of symbols]

[0049] 10 cases 14 Sealing plate 14u top surface (outside surface) 14d Bottom surface (inner surface) 15 Electrolyte injection hole (through hole) 16 Sealing member 16b Base 16s shaft 16f1 Outer flange 16f2 Inner flange 16m gas permeable membrane 20 Electrode body 100 Energy storage device

Claims

1. a metal case having a through hole; an electrode body housed in the case; a sealing member that seals the through hole; Equipped with The sealing member is a resin base portion integrated with the case so as to continuously cover at least an inner wall of the through hole and a peripheral portion of the through hole on an outer surface of the case; a gas-permeable membrane made of resin and heat-welded to the base portion on the outside of the case so as to cover the through-hole; An electricity storage device comprising:

2. The base portion further continuously covers a peripheral portion of the through hole on the inner surface of the case. The electricity storage device according to claim 1 .

3. a roughened surface is applied to at least one of a peripheral portion of the through hole on the outer surface of the case and a peripheral portion of the through hole on the inner surface of the case; The electricity storage device according to claim 1 or 2.

4. The roughened surface is formed continuously in the circumferential direction of the through hole. The electricity storage device according to claim 3 .

5. The thickness of the surface of the case where the through hole is provided is 5 mm or less. The electricity storage device according to claim 1 or 2.

6. The base is made of at least one resin material selected from the group consisting of polyethylene, polypropylene, polyamide, and polyphenylene sulfide. The electricity storage device according to claim 1 or 2.

7. The gas-permeable membrane is made of at least one resin material selected from the group consisting of polyethylene and polytetrafluoroethylene. The electricity storage device according to claim 1 or 2.

8. an integration step of preparing a metal case having a through hole, and integrating a resin base with the case so as to continuously cover at least an inner wall of the through hole and a peripheral portion of the through hole on an outer surface of the case; a preparation step of preparing an assembly including the case integrated with the base portion and an electrode body housed in the case; a sealing step of thermally welding a gas-permeable membrane made of resin to the base portion along a radial direction of the through hole on the outside of the case to close the through hole; Including, A method for manufacturing an electricity storage device.

9. After the preparing step, the liquid injection step of injecting an electrolyte into the case through the through hole is further included. The method of claim 8.

10. In the integration step, the base portion is integrated with the case by insert molding. The method of claim 8.

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