Energy storage devices

Abstract

To provide a power storage device with suitably improved safety.SOLUTION: A power storage device disclosed herein comprises: an electrode body having a positive electrode and a negative electrode; a case which has an opening and houses the electrode body; a sealing plate 14 which has a terminal attachment hole and seals the opening; an electrode terminal having one end electrically connected to the electrode body inside the case and the other end inserted through the terminal attachment hole so as to be exposed to the outside of the sealing plate 14; and a resin insulation member 50 for insulating the electrode terminal from an outer surface 14A, which is a surface of the sealing plate 14, located outside the case while sealing the opening. The sealing plate 14, the electrode terminal, and the insulation member 50 are formed by insert-molding. On the outer surface 14A side of the sealing plate 14, the sealing plate 14 has a groove 14t on a boundary between itself and the insulation member 50. The groove 14t is provided over the entire perimeter of the electrode terminal.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device. [Background technology]

[0002] So-called power storage devices, which include secondary batteries such as lithium-ion secondary batteries and capacitors such as lithium-ion capacitors, are becoming increasingly popular as portable power sources for personal computers and mobile devices, as well as power sources for driving vehicles such as BEVs (electric vehicles), HEVs (hybrid electric vehicles), and PHEVs (plug-in hybrid electric vehicles).

[0003] One example of this type of electricity storage device is an electricity storage device in which an electrode body of a predetermined shape is connected to a member (hereinafter referred to as a "sealing plate assembly") in which a sealing plate, electrode terminals, and an insulating member are previously integrated by insert molding, and the assembly is housed in an exterior body. Such an electricity storage device can be manufactured by housing the electrode body in the exterior body and then welding the opening of the exterior body to the sealing plate. The sealing plate assembly is manufactured by inserting electrode terminals into terminal mounting holes, setting the assembly in a mold, pouring molten resin into the mold, and allowing it to cool. For example, Patent Document 1 describes an example of a sealed electricity storage device (a lithium ion secondary battery) manufactured using an integrally molded member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-086813 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the results of investigations conducted by the present inventors, when components such as electrode terminals and sealing plates are set into a mold during insert molding, small gaps occur due to component tolerances. Molten resin easily seeps into such small gaps, leaking into unintended locations and generating resin burrs (also simply referred to as "flash") after cooling. The inventors found that molten resin is particularly prone to leaking into unintended locations between the electrode terminals and the terminal mounting holes in the sealing plate, generating burrs over a wide area even when the electrode terminals and other components are fixed in place with a mold. The presence of such burrs can result in scorching when the sealing plate and exterior body are welded together, potentially scorching the insulating material.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electricity storage device with suitably improved safety. [Means for solving the problem]

[0007] The disclosed power storage device includes an electrode assembly having a positive electrode and a negative electrode, a case having an opening and accommodating the electrode assembly, a sealing plate having a terminal mounting hole and sealing the opening, an electrode terminal having one end electrically connected to the electrode assembly inside the case and the other end inserted into the terminal mounting hole and exposed outside the sealing plate, and an insulating member made of resin that insulates the electrode terminal from the outer surface of the sealing plate that is on the outside of the case when the opening is sealed. The sealing plate, the electrode terminal, and the insulating member are insert-molded, and the sealing plate has a groove on the outer surface side of the sealing plate at the boundary with the insulating member, the groove being provided around the entire periphery of the electrode terminal.

[0008] This configuration can prevent burrs from forming on the outer surface of the sealing plate excluding the grooves, thereby effectively preventing the insulating member from burning and providing a safer electricity storage device. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a partial cross-sectional view schematically showing a battery according to one embodiment. [Figure 2] FIG. 2 is an exploded perspective view of FIG. [Figure 3] FIG. 3 is a schematic plan view of the sealing plate of FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of the vicinity of the negative electrode terminal. [Figure 5] FIG. 5 is a perspective view showing the vicinity of the negative electrode terminal. [Figure 6] FIG. 6 is a diagram schematically illustrating an injection molding process according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. Matters necessary for implementing the technology disclosed herein, other than those specifically mentioned in this specification (e.g., the general configuration and manufacturing process of a battery that do not characterize the technology disclosed herein), can be understood as design matters for a person skilled in the art based on conventional technology 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. In the following description, components and parts that perform the same function are designated by the same reference numerals, and redundant descriptions may be omitted or simplified. In the following description, the reference numerals L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom. In the drawings, the reference numeral X indicates the "short side direction of the power storage device," the reference numeral Y indicates the "long side direction of the power storage device," and the reference numeral Z indicates the "height direction of the power storage device." However, these directions are merely used for convenience of explanation and do not limit the installation form of the power storage device 100 in any way. In this specification, the expression "A to B" indicating a range means "A or more and B or less."

[0011] In this specification, the term "electricity storage device" refers to a general device that can be repeatedly charged and discharged by the movement of charge carriers between a positive electrode and a negative electrode via an electrolyte. The concept of electricity storage device 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.

[0012] FIG. 1 is a partial cross-sectional view of the electricity storage device 100. FIG. 2 is a schematic exploded perspective view of the electricity storage device 100. As shown in FIGS. 1 and 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 an insulating member 50. The positive electrode terminal 30 and / or the negative electrode terminal 40 are examples of electrode terminals. Although not shown, the electricity storage device 100 further includes an electrolyte. The electricity storage device 100 is preferably a secondary battery, and more preferably a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

[0013] Case 10 includes an exterior body 12 and a sealing plate 14. Exterior body 12 and sealing plate 14 are examples of case components that make up case 10. Here, case 10 has a flattened rectangular parallelepiped (square) outer shape. Case 10 is integrated, for example, by joining (e.g., welding) sealing plate 14 to the periphery of opening 12h of exterior body 12. Exterior body 12 and sealing plate 14 are formed, for example, from aluminum or an aluminum alloy.

[0014] The exterior body 12 is a housing that contains the electrode assembly 20 and the electrolyte. The exterior body 12 is a bottomed, square-shaped container having an opening 12h on its top surface. The opening 12h is approximately rectangular. As shown in FIGS. 1 and 2, the exterior body 12 includes a bottom wall 12a, a pair of long side walls 12b extending from the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the bottom wall 12a and facing each other. The bottom wall 12a is approximately rectangular. The bottom wall 12a faces the opening 12h.

[0015] FIG. 3 is a schematic plan view of the sealing plate 14. The sealing plate 14 is a plate-shaped member that seals the opening 12h of the exterior body 12. As shown in FIG. 3, the sealing plate 14 has a substantially rectangular shape in a plan view. The size of the sealing plate is not particularly limited and can be appropriately changed depending on the desired battery capacity, etc. As an example, the length of the short side direction X of the sealing plate 14 may be approximately 10 mm to 50 mm (preferably 20 mm to 40 mm), and the length of the long side direction Y of the sealing plate 14 may be approximately 100 mm to 450 mm (preferably 120 mm to 400 mm). In addition, the thickness of the sealing plate 14 (length in the vertical direction Z) is preferably 0.3 mm to 2 mm, and may be 0.5 mm to 1.5 mm. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. As shown in FIG. 2, the sealing plate 14 has an outer surface 14A that faces the outside and is located outside the case 10 when the opening 12h is sealed, and an inner surface 14B that faces the inside of the electricity storage device 100 and faces the electrode assembly 20. The sealing plate 14 also has terminal mounting holes 18 and 19 that penetrate the outer surface 14A and the inner surface 14B (see FIG. 1). The terminal mounting holes 18 and 19 are provided at both ends of the sealing plate 14 in the long side direction Y. Here, the terminal mounting hole 18 is for the positive electrode terminal 30, and the terminal mounting hole 19 is for the negative electrode terminal 40. The sealing plate 14 is provided with a gas release valve 15 and a liquid injection hole 16 for injecting the electrolyte. The gas release valve 15 is a thin-walled portion that breaks when the pressure inside the case 10 exceeds a predetermined value, thereby discharging gas inside the case 10 to the outside. The liquid injection hole 16 is sealed with a sealing member 17.

[0016] The case 10 can accommodate an electrolyte solution together with the electrode assembly 20 as described above. Any electrolyte solution used in conventionally known batteries can be used without particular limitation. As an example, a non-aqueous electrolyte solution in which a supporting salt is dissolved in a non-aqueous solvent can be used. Examples of non-aqueous solvents include carbonate-based solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorine-containing lithium salts such as LiPF6.

[0017] As shown in FIG. 2, the electricity storage device 100 includes a sealing plate assembly 60. The sealing plate assembly 60 is an assembly component in which electrode terminals (positive electrode terminal 30 and negative electrode terminal 40) and an insulating member 50 are assembled to the sealing plate 14 by insert molding (integral molding). The electrode terminals are each firmly fixed to the sealing plate 14 by the insulating member 50. As a result, the electrode terminals are assembled to the sealing plate 14 without being subjected to a crimping process. Furthermore, the electrode terminals are fixed by the insulating member 50 without coming into direct contact with the sealing plate 14. The sealing plate 14 and the electrode terminals are in close contact with the insulating member 50, and therefore the terminal mounting holes 18 and 19 are sealed by the insulating member 50. In other words, the electrode terminals are immovably fixed to the sealing plate 14 by the insulating member 50.

[0018] As shown in FIG. 1 , the electrode assembly 20 is housed inside the exterior housing 12. The electrode assembly 20 is housed inside the exterior housing 12 while covered, for example, with an insulating film (not shown). Here, the electrode assembly 20 is a wound electrode assembly in which a strip-shaped positive electrode sheet 22 and a strip-shaped negative electrode sheet 24 are stacked in an insulated state via two strip-shaped separator sheets 70, and wound in the longitudinal direction around the winding axis. However, the electrode assembly 20 may also be a stacked electrode assembly in which rectangular positive electrode sheets and rectangular negative electrode sheets are alternately stacked with rectangular separator sheets interposed therebetween. Alternatively, the electrode assembly 20 may be a zigzag-folded stacked electrode assembly formed by sandwiching multiple positive electrode sheets and multiple negative electrode sheets between zigzag-folded separator sheets.

[0019] The positive electrode sheet 22 includes a strip-shaped positive electrode current collector 22c and a positive electrode active material layer 22a fixed to at least one surface of the positive electrode current collector 22c (see FIG. 1). The components constituting the positive electrode sheet 22 may be made of conventionally known materials that can be used in general batteries (e.g., lithium-ion secondary batteries) without any particular restrictions. For example, the positive electrode current collector 22c is preferably made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode active material layer 22a contains a positive electrode active material (e.g., a lithium transition metal composite oxide such as a lithium-nickel-cobalt-manganese composite oxide) that can reversibly store and release charge carriers. The positive electrode active material layer 22a may also contain optional components other than the positive electrode active material, such as a conductive material, a binder, or various additives.

[0020] The negative electrode sheet 24 includes a strip-shaped negative electrode current collector 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector 24c (see FIG. 1). The components constituting the negative electrode sheet 24 may be made of conventionally known materials that can be used in general batteries (e.g., lithium-ion secondary batteries) without any particular restrictions. For example, the negative electrode current collector 24c is preferably made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode active material layer 24a contains a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly store and release charge carriers. The negative electrode active material layer 24a may also contain optional components other than the negative electrode active material, such as a conductive material, a binder, a dispersant, or various additives.

[0021] The separator sheet 70 is an insulating sheet having a plurality of fine through-holes formed therein through which charge carriers can pass. The separator sheet 70 is made of, for example, a porous resin substrate. Examples of the resin substrate include sheets (films) made of resins such as polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters, polyamides, and cellulose. The separator sheet 70 may have a single-layer structure, or may have a laminated structure of two or more porous resin sheets having different properties and characteristics (thickness, porosity, etc.) (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). The separator sheet 70 may also have a heat-resistant layer (HRL) made of ceramic particles or the like on its surface.

[0022] As shown in FIG. 1 , the electrode assembly 20 housed inside the exterior housing 12 is arranged so that one end of the positive electrode current collector 22c is near the left end of the long side direction Y of the electricity storage device 100, and one end of the negative electrode current collector 24c is near the right end of the long side direction Y of the electricity storage device 100. The positive electrode terminal 30 is attached to one end of the sealing plate 14 in the long side direction Y (the left end in FIG. 1 ). The negative electrode terminal 40 is attached to the other end of the sealing plate 14 in the long side direction Y (the right end in FIG. 1 ). In the electricity storage device 100, one end of the positive electrode terminal 30 and the negative electrode terminal 40 is electrically connected to the electrode assembly 20 inside the case 10 as described above, and the other end is inserted into the terminal mounting holes 18, 19 and exposed to the outside of the sealing plate 14. The positive electrode terminal 30 is preferably formed of a metal with excellent conductivity, such as aluminum or an aluminum alloy. The negative electrode terminal 40 is preferably made of a metal with excellent electrical conductivity, such as copper or a copper alloy.

[0023] FIG. 4 is a schematic cross-sectional view of the vicinity of the negative electrode terminal. As shown in FIGS. 2 and 4, the negative electrode terminal 40 has an external connection portion 41, a base portion 42, and an electrode body connection portion 43. The negative electrode terminal 40 may have a shaft portion (not shown) between the external connection portion 41 and the base portion 42. In the following description, the negative electrode terminal 40 is used as the electrode terminal and the insulating member 50 on the negative electrode terminal 40 side is used as the insulating member, but this description is not intended to limit the application of the technology disclosed herein to the structure on the negative electrode terminal side. In other words, the technology disclosed herein encompasses a configuration including a positive electrode terminal having a configuration substantially equivalent to the negative electrode terminal 40 described below.

[0024] As shown in FIG. 4, the external connection portion 41 is configured to have a size that allows it to be inserted into the terminal mounting hole 19. The upper end of the external connection portion 41 is arranged so as to be exposed to the outside of the case 10. The external connection portion 41 is provided above the base portion 42. Here, the base portion 42 is formed in a plate shape. The base portion 42 is arranged inside the case 10. The outer shape of the base portion 42 is configured to be larger than the terminal mounting hole 19. The electrode body connection portion 43 is arranged inside the case 10. The electrode body connection portion 43 extends downward from one end of the base portion 42. An end of the electrode body connection portion 43 is connected to the electrode body 20 (more specifically, the negative electrode sheet 24) inside the case 10. Note that in the example shown in FIG. 4, the external connection portion 41 is configured to have a size that allows it to be inserted into the terminal mounting hole 19, but the configuration of the electrode terminal is not limited to this. For example, the electrode terminal may be configured to have a size that allows the electrode body connection portion 43 and the base portion 42 to be inserted into the terminal mounting hole 19 .

[0025] The insulating member 50 is disposed between the sealing plate 14 and the positive electrode terminal 30 and the negative electrode terminal 40, and prevents electrical conduction between the sealing plate 14 and the positive electrode terminal 30 and the negative electrode terminal 40. The insulating member 50 is mainly composed of a resin material. Examples of resin materials include fluorinated resins such as perfluoroalkoxy fluorine resin (PFA), polyphenylene sulfide resin (PPS), and aliphatic polyamide. It is particularly preferable that the insulating member 50 be mainly composed of PPS. In addition to the resin materials such as PFA and PPS, inorganic fillers may be added to the insulating member 50. Examples of inorganic fillers that can be used include inorganic oxides and glass having insulating properties. Specific examples of inorganic fillers include alumina, magnesia, silica, and titania. The phrase "A is mainly composed of B" means that, among the components constituting A, B is the largest component by weight.

[0026] As shown in FIG. 4 , the insulating member 50 has a cylindrical portion 51 and a flange portion 52. The cylindrical portion 51 and the flange portion 52 are integrally formed. The cylindrical portion 51 is located between the external connection portion 41 and the terminal mounting hole 19. The cylindrical portion 51 insulates the negative electrode terminal 40 from the terminal mounting hole 19. The upper end of the cylindrical portion 51 is exposed to the outside of the case 10. The flange portion 52 extends horizontally from the cylindrical portion 51 along the inner surface 14B of the sealing plate 14. The flange portion 52 insulates the inner surface 14B of the sealing plate 14 from the base portion 42. The outer shape of the flange portion 52 is configured to be larger than the outer shape of the base portion 42.

[0027] FIG. 5 is an enlarged perspective view of the periphery of the negative electrode terminal 40. As shown in FIGS. 3 to 5, the electricity storage device 100 disclosed herein has a groove 14t on the outer surface side of the sealing plate 14 at a boundary 14N with the insulating member 50. The groove 14t is provided around the entire circumference of the electrode terminals (the positive electrode terminal 30 and the negative electrode terminal 40). This configuration makes it possible to provide an electricity storage device 100 with higher safety. As will be described in detail later, insert molding is performed by setting each component in a mold and pouring molten resin into it. At this time, small gaps exist between each component due to component tolerances. The molten resin easily penetrates even these small gaps. The molten resin then leaks into unintended locations, resulting in resin burrs (also simply referred to as "flash") after cooling. In particular, the molten resin is likely to leak into unintended locations between the electrode terminals and the terminal mounting holes 18, 19 of the sealing plate 14, and burrs can occur over a wide area even when the electrode terminals are fixed in place using a mold. If such burrs exist, they may scorch when the sealing plate 14 and the exterior body 12 are welded together, and further, the insulating member 50 may scorch. Therefore, in the electricity storage device 100 disclosed herein, the sealing plate 14 has the groove 14t as described above. By providing such groove 14t, there is room for the molten resin to flow, and the molten resin is prevented from spreading beyond the groove 14t onto the outer surface 14A of the sealing plate 14. This prevents burrs from forming over a wide area on the outer surface 14A of the sealing plate 14 after insert molding. This configuration prevents the insulating member 50 from scorching, making it possible to provide an electricity storage device 100 with greater safety.

[0028] The groove 14t is configured so that even if the molten resin flows in, it will not exceed the groove 14t and cause burrs on the outer surface 14A of the sealing plate 14. The groove 14t is located on the outer surface 14A side of the sealing plate 14. The groove 14t is a recess that is recessed from the outer surface 14A toward the inner surface 14B of the sealing plate 14. Here, the groove 14t has a rectangular cross section. The sidewalls of the groove 14t are perpendicular to the bottom surface of the groove 14t. However, the cross section of the groove 14t may also be polygonal or semicircular.

[0029] In plan view, the groove 14t is formed continuously in a substantially annular shape along the boundary 14N between the sealing plate 14 and the insulating member 50. The groove 14t is formed in a substantially rectangular shape around the entire circumference of the electrode terminal (here, the negative electrode terminal 40) as shown in FIG. 5. This prevents molten resin from leaking between the electrode terminal and the terminal mounting hole 19 and causing burrs in unintended positions. The grooves 14t are preferably provided at substantially equal intervals with respect to the center of the electrode terminal.

[0030] Although not particularly limited, groove portion 14t is preferably configured so that, when groove width 14t is X mm and groove depth 14t is Y mm, the sum of groove width X and groove depth Y is 1 mm or more. That is, the cross-sectional shape of groove portion 14t is preferably configured to satisfy the formula: (X + Y) ≥ 1. This prevents molten resin from leaking beyond groove portion 14t, thereby preventing burrs from forming on outer surface 14A of sealing plate 14. The sum of groove width X and groove depth Y is preferably 3 mm or less, for example, and may be 2.5 mm or less. This ensures sufficient strength of sealing plate 14.

[0031] By having the groove depth Y of the groove portion 14t be a predetermined depth, even if the molten resin leaks, it can be contained appropriately. Although not particularly limited, the groove depth Y of the groove portion 14t is preferably 0.1 mm or greater. According to the results of studies by the present inventors, the thickness tolerance of the sealing plate 14 is less than 0.1 mm. Therefore, by setting the groove depth Y to 0.1 mm or greater, it is possible to sufficiently prevent the molten resin from leaking beyond the groove portion 14t onto the outer surface 14A of the sealing plate 14. In particular, insert molding using a mold with protrusions, as described below, can effectively prevent the molten resin from spilling out of the groove portion 14t. The upper limit of the groove depth Y of the groove portion 14t is not particularly limited, but is preferably ½ or less, and may be ⅓ or less, of the thickness t of the sealing plate 14. More specifically, it is preferably 1 mm or less, and may be 0.7 mm or less, or may be 0.5 mm or less. The groove depth Y refers to the length in the vertical direction Z from the upper end to the lower end of the groove portion 14t.

[0032] By ensuring that the groove width X of the groove portion 14t has a predetermined length, it is possible to prevent resin from leaking onto the outer surface 14A of the sealing plate 14. The groove width X is preferably 0.1 mm or more, for example, and may be 0.5 mm or more. This ensures sufficient space to accommodate the molten resin. On the other hand, if the groove portion 14t is too wide, the strength of the sealing plate 14 may be reduced, and the adhesive strength between the electrode terminal and the sealing plate 14 may be reduced. From this perspective, the groove width X is preferably 2 mm or less, and more preferably 1.5 mm or less. The groove width X is the length in the short side direction X and the length in the long side direction Y.

[0033] In a preferred embodiment, the insulating member 50 is not disposed on the outer surface 14A of the sealing plate 14 (more specifically, the outer surface 14A excluding the grooves 14t). This makes it possible to preferably prevent the insulating member 50 from being burned during welding or the like. The insulating member 50 may or may not be disposed in the grooves 14t. Preferably, as shown in FIG. 4, the insulating member 50 is not disposed in the grooves 14t. For example, by performing insert molding using a mold having protrusions, which will be described later, it is possible to manufacture an electricity storage device 100 in which the insulating member 50 is not disposed in the grooves 14t.

[0034] It is preferable that at least a portion of the surface of the sealing plate 14 that comes into contact with the insulating member 50 is roughened. The roughening treatment is a surface treatment that increases the surface area and enhances the anchoring effect by forming irregularities on the surface, thereby improving the bonding and adhesion with the insulating member 50. The roughening treatment can be performed, for example, by laser irradiation or sandblasting. The roughened portion of the sealing plate 14 constitutes a roughened surface treatment portion 14s (see FIG. 4). It is preferable that the sealing plate 14 has the roughened surface treatment portion 14s in at least a portion of the boundary portion 14N with the insulating member 50.

[0035] The roughened surface portion 14s is preferably disposed so as to block a leakage path of the electrolyte (i.e., a path through which the electrolyte leaks from the inside of the electricity storage device 100). For example, the roughened surface portion 14s is provided on the inner surface 14B around the terminal mounting hole 19 and on the surface of the side surface 14c that constitutes the terminal mounting hole 19 and is in contact with the insulating member 50. The roughened surface portion 14s on the inner surface 14B of the sealing plate 14 is preferably provided over the entire area surrounding the terminal mounting hole 19. Although not particularly limited, the width W1 of the roughened surface portion 14s on the inner surface 14B of the sealing plate 14 is preferably 1 mm or more, and more preferably 3 mm or more. This increases the adhesive strength between the sealing plate 14 and the insulating member 50, enabling more secure sealing. More preferably, the sealing plate 14 has the roughened surface portion 14s over the entire surface that is in contact with the insulating member 50.

[0036] Although not particularly limited, it is preferable that at least a portion of the surface of the electrode terminal that comes into contact with the insulating member 50 be roughened, similar to the roughened surface-treated portion 14s of the sealing plate 14. As shown in Fig. 4, the roughened portion of the electrode terminal (here, the negative electrode terminal 40) constitutes the roughened surface-treated portion 40s. It is preferable that the negative electrode terminal 40 has the roughened surface-treated portion 40s in at least a portion of the boundary portion 40N with the insulating member 50.

[0037] Similar to the above-described roughening portion 14s, the roughening portion 40s of the negative electrode terminal 40 is preferably disposed so as to block a leakage path for the electrolyte. For example, the roughening portion 40s is provided on the side surface 41c of the external connection portion 41 and the upper surface 42a of the base portion 42. The length L1 of the roughening portion 40s on the side surface 41c of the external connection portion 41 is preferably 1 mm or more along the side surface 41c, and may be 3 mm or more. The length L2 of the roughening portion 40s on the upper surface 42a of the base portion 42 is preferably 1 mm or more along the upper surface 42a, and may be 3 mm or more. This increases the adhesive strength between the electrode terminal and the insulating member 50, enabling a more secure seal. More preferably, the electrode terminal has the roughening portion 40s over the entire surface that contacts the insulating member 50.

[0038] Both the sealing plate 14 and the electrode terminal may have the roughened surface-treated portion 14s and the roughened surface-treated portion 40s, respectively, which more firmly seals the sealing plate 14, the electrode terminal, and the insulating member 50, thereby realizing an electricity storage device 100 with high safety.

[0039] <Method of manufacturing an electricity storage device> Next, a description will be given of an example of a method for manufacturing the electricity storage device 100. The manufacturing method disclosed herein includes, for example, (1) a preparation step and (2) a sealing step. Here, the (1) preparation step includes an (1A) insert molding step.

[0040] (1) In the preparation step, at least the exterior body 12, the sealing plate 14, the positive electrode terminal 30, the negative electrode terminal 40, and the electrode body 20 are prepared. Here, the sealing plate 14 is prepared so that grooves 14t are provided around the terminal mounting holes 18, 19.

[0041] (1A) In the insert molding process, the sealing plate 14, positive electrode terminal 30, negative electrode terminal 40, and insulating member 50 are integrated to create an assembly part (e.g., sealing plate assembly 60). The sealing plate assembly 60 can be produced by insert molding the sealing plate 14, positive electrode terminal 30, negative electrode terminal 40, and insulating member 50. This reduces the number of parts and makes it easier to form a conductive path than conventional methods using rivets. Insert molding can be performed according to conventionally known methods, such as those described in JP 2021-086813 A, JP 2021-086814 A, Japanese Patent No. 03986368 A, and Japanese Patent No. 6648671 A. For example, the insert molding process can be carried out using a molding die having an upper die and a lower die, by a method including a part setting process, a positioning process, an upper die setting process, an injection molding process, an upper die release process, and a part removal process.

[0042] In the component setting process, the positive electrode terminal 30 and the negative electrode terminal 40 are inserted into the terminal mounting holes 18, 19 of the sealing plate 14, respectively, and then the sealing plate 14 is attached to the lower mold. In the positioning process, the positive electrode terminal 30 and the negative electrode terminal 40 are positioned and fixed. In the upper mold setting process, the upper mold is attached together with the lower mold so that the sealing plate 14 and the positive electrode terminal 30 and the negative electrode terminal 40 are sandwiched between them in the vertical direction. In the injection molding process, first, the molding die is heated. Next, molten resin is injected into the molding die. The molten resin flows from the upper mold through the terminal mounting holes 18, 19 and into the lower mold. Then, the molding die and the molded product are cooled. This integrates the insulating member 50, the sealing plate 14, and the electrode terminals. In the upper mold release process, the upper mold is separated from the lower mold. In the component removal process, the molded product is removed from the lower mold.

[0043] FIG. 6 is a schematic diagram illustrating the injection molding process. As shown in FIG. 6, the upper mold 210 of the molding die 200 may have protrusions 212 that can fit into the grooves 14t. By performing the injection molding process with the protrusions 212 of the upper mold 210 fitting into the grooves 14t, the injected molten resin is prevented from spilling out of the grooves 14t and adhering to the outer surface 14A of the sealing plate 14. This further reduces the occurrence of burrs. Although not particularly limited, the length of the protrusions 212 in the vertical direction Z is preferably 0.05 mm to 0.3 mm (preferably 0.1 mm). As described above, the thickness tolerance of the sealing plate 14 is less than 0.1 mm, so protrusions 212 with lengths within the above-mentioned range can accommodate the thickness tolerance of the sealing plate 14. Therefore, the injection molding process can be performed with the upper mold 210 and the sealing plate 14 in close contact with each other, which more effectively prevents the molten resin from leaking out.

[0044] (2) In the sealing process, the exterior housing 12 is sealed with the sealing plate assembly 60 while the electrode assembly 20 and electrolyte are contained in the exterior housing 12. Specifically, first, the electrode assembly connecting portion 43 of the sealing plate assembly 60 is connected to the electrode assembly 20. Next, the electrode assembly 20 is inserted through the opening 12h of the exterior housing 12, and the periphery of the sealing plate 14 of the sealing plate assembly 60 is joined to the opening 12h of the exterior housing 12 by laser welding or the like. Then, the electrolyte is injected through the liquid injection hole 16, and the liquid injection hole 16 is closed with the sealing member 17, thereby sealing the electricity storage device 100. In this manner, the electricity storage device 100 can be manufactured. In the electricity storage device 100 disclosed herein, the sealing plate 14 has the groove portion 14t, which reduces the occurrence of burrs. Therefore, even if welding is performed in the sealing process, the burrs do not burn. Therefore, an electricity storage device 100 with improved safety can be provided.

[0045] <Battery uses> 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 or truck. The type of vehicle is not particularly limited, and examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV). The electricity storage device 100 has improved safety and can therefore be suitably used to construct a battery pack.

[0046] Although several embodiments of the present invention have been described above, the above embodiments are merely examples. 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 common general technical knowledge in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiments. For example, it is possible to replace part of the above-described embodiments with other modified embodiments, and it is also possible to add other modified embodiments to the above-described embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0047] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: An electricity storage device comprising: an electrode assembly having a positive electrode and a negative electrode; a case having an opening and accommodating the electrode assembly; a sealing plate having a terminal mounting hole and sealing the opening; an electrode terminal having one end electrically connected to the electrode assembly inside the case and the other end inserted into the terminal mounting hole and exposed to the outside of the sealing plate; and an insulating member made of resin that insulates the electrode terminal from an outer surface of the sealing plate that is on the outside of the case when the opening is sealed; wherein the sealing plate, the electrode terminal, and the insulating member are insert-molded; and the sealing plate has a groove at the boundary with the insulating member on the outer surface side of the sealing plate, the groove being provided around the entire periphery of the electrode terminal. Item 2: The electricity storage device according to item 1, wherein, when the groove width is X mm and the groove depth is Y mm, the sum of the groove width X and the groove depth Y is 1 mm or more. Item 3: The electricity storage device according to Item 2, wherein the groove depth Y is 0.1 mm or more. Item 4: The electricity storage device according to any one of Items 1 to 3, wherein the sealing plate has a roughened surface on at least a part of the boundary between the sealing plate and the insulating member. Item 5: The electricity storage device according to any one of items 1 to 4, wherein the electrode terminal has a surface-roughened portion at least in a part of the boundary between the electrode terminal and the insulating member. [Explanation of symbols]

[0048] 10 cases 12 Exterior body 12a Bottom wall 12b Long side wall 12c short side wall 12h opening 14 Sealing plate 14A outer surface 14B Inner surface 14c side 14N Boundary part 14s roughening treatment area 14t groove 15 Gas exhaust valve 16 Liquid injection hole 17 Sealing member 18 Terminal mounting hole 19 Terminal mounting hole 20 Electrode body 22 Positive electrode sheet 24 Negative electrode sheet 30 Positive terminal 40 Negative terminal 40N boundary part 40s roughening treatment area 41 External connection part 41c side 42 Base 42a Top side 43 Electrode body connection part 50 Insulating material 51 Cylindrical part 52 flange 60 Sealing plate assembly 70 Separator Sheet 100 Energy storage device 200 molding dies 210 Upper mold 212 Protrusion

Claims

1. an electrode assembly having a positive electrode and a negative electrode; a case having an opening and accommodating the electrode assembly; a sealing plate having a terminal mounting hole and sealing the opening; an electrode terminal having one end electrically connected to the electrode body inside the case and the other end inserted into the terminal mounting hole and exposed to the outside of the sealing plate; a resin insulating member that insulates the electrode terminal from an outer surface of the sealing plate that is on the outside of the case when the opening is sealed, the sealing plate, the electrode terminals, and the insulating member are insert-molded, the sealing plate has a groove at a boundary between the outer surface of the sealing plate and the insulating member, the groove is provided around the entire periphery of the electrode terminal, The electrical storage device, wherein the insulating member is not disposed in the groove portion.

2. The electricity storage device according to claim 1 , wherein when the groove portion has a groove width of X mm and a groove depth of Y mm, the sum of the groove width X and the groove depth Y is 1 mm or more.

3. The electricity storage device according to claim 2 , wherein the groove depth Y is 0.1 mm or more.

4. The electricity storage device according to claim 1 , wherein the sealing plate has a roughened surface at least in part of a boundary between the sealing plate and the insulating member.

5. The power storage device according to claim 1 , wherein the electrode terminal has a surface-roughened portion at least in part of a boundary between the electrode terminal and the insulating member.

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