Energy storage devices

Abstract

To provide a power storage device with a higher level of safety.SOLUTION: A power storage device disclosed herein includes: a case body having an opening part; a sealing plate 14 having a terminal fit hole 18 and sealing the opening part; an electrode body accommodated inside the case body; a collector terminal 30 having one end electrically connected to the electrode body inside the case body and the other end exposed on an outer surface side of the sealing plate 14 through the terminal fit hole; and an insulating member 40 arranged between the sealing plate 14 and the collector terminal 30. In such power storage device, the insulating member 40 is arranged at a periphery 18a of the terminal fit hole 18 of the sealing plate 14 while being molded integrally with a peripheral portion of the terminal fit hole 18 and the collector terminal 30, and at least one part of the periphery 18a of the terminal fit hole 18 of the sealing plate 14 forms a thin part 14s thinner than a surrounding of the one part.SELECTED DRAWING: Figure 5

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). An example of an electricity storage device for such applications is one in which an electrode assembly having positive and negative electrodes is housed in a so-called square-shaped metal case that is a hexahedron consisting of six rectangular faces. A typical example of such an electricity storage device is one that includes a square-shaped case body with one open face and a rectangular sealing plate (lid) that covers the opening, and in which current collecting terminals for positive and negative electrodes electrically connected to the positive and negative electrodes of the electrode assembly housed in the case are disposed on the outer surface of the sealing plate through terminal mounting holes for the positive and negative electrodes provided in the sealing plate.

[0003] An example of this type of electricity storage device is a sealed electricity storage device in which an assembly of the sealing plate and the current collector terminal (hereinafter referred to as the "current collector terminal-sealing plate assembly") is integrally molded using a predetermined mold, with a synthetic resin insulating member placed around the periphery of the terminal mounting hole in advance, and the current collector terminal is attached to the sealing plate while part of the current collector terminal is passed through the mounting hole; this integrally molded current collector terminal-sealing plate assembly is connected to an electrode body of a predetermined shape, and the assembly is then housed in a case body; and a sealing plate is then joined to the opening of the case. For example, Patent Document 1 describes an example of a sealed electricity storage device (lithium ion secondary battery) manufactured using such an integrally molded current collector terminal-sealing plate assembly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-86813 Summary of the Invention [Problem to be solved by the invention]

[0005] The current collector terminal-sealing plate assembly described in Patent Document 1 raises the following concerns. Specifically, the rigidity of the sealing plate portion integrally molded with the current collector terminal and insulating member tends to be higher than the rigidity of the sealing plate portion alone (i.e., portions not involved in the integral molding) due to the integral molding. More specifically, the sealing plate is often fitted into the opening of the case body, and the periphery of the sealing plate is welded to seal the opening. The rigidity of the welded sealing plate at its periphery is not uniform around the sealing plate; the rigidity of the portion close to the portion where the current collector terminal is integrally molded with the insulating member tends to be higher than the rigidity of the portion away from the portion where the current collector terminal is integrally molded with the insulating resin. In other words, the rigidity of the sealing plate at its periphery after welding is thought to be distributed in a manner that includes relatively high and low rigidity portions depending on the position.

[0006] When stress is generated in the sealing plate for some reason, such as when the case bulges during use of the electricity storage device or when a load is applied from outside the electricity storage device, the stress may be concentrated in a portion with relatively low rigidity, reducing the breaking strength of that portion. For this reason, when viewed along the periphery of the sealing plate, it is undesirable for there to be excessive differences in rigidity (differences that exceed the allowable range) between different locations. The present invention was created to prevent such problems from occurring, and aims to provide a current collector terminal-sealing plate assembly in which the current collector and insulating member as described above are integrally molded with the sealing plate (specifically, the portion encompassing the peripheral portion of the terminal mounting hole), in which the difference in rigidity between the integrally molded portion and the portion of the sealing plate that is not involved in the integral molding is reduced, as well as an electricity storage device constructed using the current collector terminal-sealing plate assembly. [Means for solving the problem]

[0007] The disclosed electricity storage device includes a case body having an opening, a sealing plate having a terminal mounting hole and sealing the opening, an electrode assembly housed inside the case body, a current collector terminal having one end electrically connected to the electrode assembly inside the case body and the other end passing through the terminal mounting hole and exposed on the outer surface of the sealing plate, and an insulating member disposed between the sealing plate and the current collector terminal. The insulating member is disposed on the periphery of the terminal mounting hole in a state where it is integrally molded with the peripheral portion of the terminal mounting hole in the sealing plate and the current collector terminal, and at least a portion of the periphery of the terminal mounting hole in the sealing plate forms a thin-walled portion that is thinner than the surrounding area of ​​that portion. To solve this problem, measures must be taken to ensure that the difference in rigidity between a point relatively close to the point where the collector terminal is integrally molded into the terminal mounting hole using an insulating material and a point relatively far from it, when viewed along the outer periphery of the sealing plate, falls within the standard difference (tolerance).

[0008] According to the electricity storage device having the above configuration, it is possible to reduce the difference in rigidity between the portion where the sealing plate, the current collecting terminal, and the insulating member are integrally molded and the portion not involved in the integral molding. This makes it possible to suppress stress concentration and improve breaking strength. Therefore, it is possible to provide an electricity storage device with higher safety. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view schematically showing a battery according to one embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating the internal structure of a battery according to one embodiment. [Figure 3] FIG. 3 is a diagram schematically illustrating the configuration of the electrode body. [Figure 4] FIG. 4 is a diagram showing a schematic diagram of a current collector terminal-sealing plate assembly in which the sealing plate, current collector terminal, and insulating member are integrally molded. [Figure 5] FIG. 5 is a cross-sectional view schematically showing the vicinity of a current collecting terminal according to the first embodiment. [Figure 6]FIG. 6 is a diagram schematically showing an electrode body to which a second current collecting portion is attached. [Figure 7] FIG. 7 is a diagram schematically showing a molding die according to one embodiment. [Figure 8] FIG. 8 is a view corresponding to FIG. 5 according to the second embodiment. [Figure 9] FIG. 9 is a view corresponding to FIG. 5 according to the third embodiment. [Figure 10] FIG. 10 is a view corresponding to FIG. 5 according to the fourth embodiment. [Figure 11] FIG. 11 is a plan view schematically showing a sealing plate according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that 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 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 drawings described below, components and parts that perform the same function are given the same reference numerals, and redundant explanations may be omitted or simplified. In addition, in this specification, the notation "A to B" (A and B are arbitrary numbers) indicating a range means A or more and B or less.

[0011] In this specification, the term "electricity storage device" refers to a device in which charge and discharge reactions occur as charge carriers move between a pair of electrodes (positive and negative electrodes) via an electrolyte. Such electricity storage devices include secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries; and capacitors (i.e., physical batteries) such as lithium-ion capacitors and electric double-layer capacitors. Hereinafter, one embodiment of the technology disclosed herein will be described using a lithium ion secondary battery as an example of the above-mentioned power storage devices.

[0012] First Embodiment FIG. 1 is a perspective view of a secondary battery 100 according to this embodiment. FIG. 2 is a diagram schematically illustrating the internal structure of the secondary battery 100. In the following description, the symbols 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 secondary battery 100, respectively. Furthermore, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom. However, these directions are defined for the sake of convenience and do not limit the installation form of the secondary battery 100 in any way. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not necessarily reflect the actual dimensional relationships.

[0013] As shown in Figures 1 and 2, the secondary battery 100 includes an electrode body 20, an electrolyte (not shown), a case body 12 that accommodates the electrode body 20 and the electrolyte, a sealing plate 14, a collector terminal 30, and an insulating member 40.

[0014] FIG. 3 is a diagram schematically illustrating the configuration of the electrode assembly 20. As shown in FIG. 3, 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 separators 26, and wound in the longitudinal direction around a winding axis WL. However, the electrode assembly may also be a laminated electrode assembly in which a rectangular positive electrode sheet and a rectangular negative electrode sheet are stacked in an insulated state by a rectangular separator. Alternatively, the electrode assembly may be a laminated electrode assembly in which a rectangular positive electrode sheet and a rectangular negative electrode sheet are stacked in an insulated state by a zigzag-folded separator.

[0015] As shown in FIG. 3, the positive electrode sheet 22 is a long, strip-shaped member. The configuration of the positive electrode sheet 22 is not particularly limited and may be similar to that used in conventionally known batteries. For example, the positive electrode sheet 22 has a strip-shaped positive electrode core 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed to at least one surface of the positive electrode core 22c. However, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments.

[0016] The positive electrode core 22c is a long, strip-shaped member. The positive electrode core 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode core 22c is a metal foil, specifically, an aluminum foil. The dimensions of the positive electrode core 22c are not particularly limited and may be determined appropriately depending on the battery design. Multiple positive electrode tabs 22t are provided at one end (the left end in FIG. 3 ) in the long side direction Y of the positive electrode core 22c. The multiple positive electrode tabs 22t protrude beyond the separator 26 in the long side direction Y. The multiple positive electrode tabs 22t protrude beyond the separator 26 in the long side direction Y. The multiple positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the positive electrode core 22c. The positive electrode tabs 22t are part of the positive electrode core 22c and are made of metal foil (aluminum foil). A positive electrode active material layer 22a is formed on a portion of the positive electrode tab 22t. In at least a portion of the positive electrode tab 22t, the positive electrode active material layer 22a is not formed, and the positive electrode core 22c is exposed. The multiple positive electrode tabs 22t are stacked at one end in the long side direction Y (the left end in FIG. 2 ) to form a positive electrode tab group 23. The multiple positive electrode tabs 22t are bent and curved so that their outer ends are aligned. The positive electrode tab group 23 is electrically connected to the positive electrode collector terminal 30 via the current collector 50.

[0017] As shown in FIG. 3, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the positive electrode substrate 22c. The positive electrode active material layer 22a contains a positive electrode active material. Known positive electrode active materials used in lithium-ion secondary batteries may be used as the positive electrode active material. Specific examples of the positive electrode active material include lithium composite oxides and lithium transition metal phosphate compounds. These positive electrode active materials may be used alone or in combination of two or more. The positive electrode active material layer 22a may contain components other than the positive electrode active material, such as a conductive material and a binder. Suitable conductive materials include carbon black, such as acetylene black (AB), and other carbon materials (e.g., graphite). Suitable binders include polyvinylidene fluoride (PVDF).

[0018] As shown in FIG. 3, the positive electrode protective layer 22p is provided at the boundary between the positive electrode core 22c and the positive electrode active material layer 22a in the long side direction Y. The positive electrode protective layer 22p may be a layer configured to have lower electrical conductivity than the positive electrode active material layer 22a. Here, the positive electrode protective layer 22p is provided at one end (the left end in FIG. 3) of the positive electrode core 22c in the long side direction Y. However, the positive electrode protective layer 22p may also be provided at both end portions in the long side direction Y. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additive components.

[0019] As shown in Fig. 3, the negative electrode sheet 24 is a long, strip-shaped member. The configuration of the negative electrode sheet 24 is not particularly limited and may be the same as that used in conventionally known batteries. For example, the negative electrode sheet 24 has a negative electrode core 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode core 24c.

[0020] The negative electrode core 24c is a long, strip-shaped member. The negative electrode core 24c is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. Here, the negative electrode core 24c is a metal foil, specifically a copper foil. The dimensions of the negative electrode core 24c are not particularly limited and may be determined appropriately depending on the battery design. Multiple negative electrode tabs 24t are provided at one end (the right end in FIG. 3 ) in the long side direction Y of the negative electrode core 24c. The multiple negative electrode tabs 24t protrude beyond the separator 26 in the long side direction Y. The multiple negative electrode tabs 24t protrude beyond the separator 26 in the long side direction Y. The multiple negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the negative electrode sheet 24. The negative electrode tabs 24t are part of the negative electrode core 24c and are made of metal foil (copper foil). A negative electrode active material layer 24a is formed on a portion of the negative electrode tab 24t. In at least a portion of the negative electrode tab 24t, the negative electrode active material layer 24a is not formed, and the negative electrode core 24c is exposed. The multiple negative electrode tabs 24t are stacked at one end in the long side direction Y (the right end in FIG. 2 ) to form a negative electrode tab group 25. The multiple negative electrode tabs 24t are bent and curved so that their outer ends are aligned. The negative electrode tab group 25 is electrically connected to the negative electrode collector terminal 30 via the current collector 50.

[0021] As shown in FIG. 3, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the strip-shaped negative electrode substrate 24c. The negative electrode active material layer 24a contains a negative electrode active material. The negative electrode active material is not particularly limited, but carbon materials such as graphite, hard carbon, and soft carbon can be used. The graphite may be natural graphite or artificial graphite, or may be amorphous carbon-coated graphite in which graphite is coated with an amorphous carbon material. The negative electrode active material layer 24a can contain components other than the negative electrode active material, such as a binder or a thickener. Examples of binders that can be used include styrene butadiene rubber (SBR) and polyvinylidene fluoride (PVDF). Examples of thickeners that can be used include carboxymethyl cellulose (CMC).

[0022] The separator 26 is an insulating resin sheet having a plurality of fine through-holes formed therein through which charge carriers can pass. The configuration of the separator 26 is not particularly limited and may be the same as that used in conventional batteries. Examples of the separator 26 include porous sheets (films) made of resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. A heat-resistant layer (HRL) may be provided on the surface of the separator 26.

[0023] As described above, the secondary battery 100 includes an electrolyte. The electrolyte is not particularly limited and may be the same as that used in conventionally known batteries. The electrolyte may contain, for example, a non-aqueous solvent (organic solvent) and an electrolyte salt (supporting salt). Examples of non-aqueous solvents that can be used include ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). Various lithium salts can be used as the supporting salt, and among these, lithium salts such as LiPF6 and LiBF4 are preferred. The electrolytic solution may contain various additives such as a film-forming agent, a gas generating agent, a dispersant, and a thickener.

[0024] As shown in FIG. 1, the case 10 (here, the battery case 10) includes a case body 12 and a sealing plate 14. Here, the battery case 10 has a rectangular parallelepiped (square) shape with a bottom. The battery case 10 can be made of any conventionally known material without any particular restrictions. The battery case 10 (case body 12 and sealing plate 14) can be made of, for example, aluminum, aluminum alloy, stainless steel, iron, iron alloy, etc.

[0025] The case body 12 is a housing that houses the electrode assembly 20 and the electrolyte. The case body 12 is a bottomed, rectangular container having an opening 12h (see FIG. 2) on one side (here, the top surface). Here, the opening 12h is substantially rectangular. As shown in FIG. 1, the case body 12 has long and short sides and includes a bottom surface 12a that is substantially rectangular in plan view, a pair of long side walls 12b that extend upward in the vertical direction Z from the long side of the bottom surface 12a and face each other, and a pair of short side walls 12c that extend upward in the vertical direction Z from the short side of the bottom surface 12a and face each other. The area of ​​the short side walls 12c is smaller than the area of ​​the long side walls 12b. While not particularly limited, the average thickness (average plate thickness) of the case body 12 is preferably approximately 0.5 mm or more, for example, 1 mm or more, from the viewpoint of durability, etc., and approximately 3 mm or less, for example, 2 mm or less, from the viewpoint of cost and energy density.

[0026] The sealing plate 14 has a generally rectangular shape in plan view and is a member that seals the opening 12h of the case body 12. The outer edge of the sealing plate 14 and the peripheral edge of the opening 12h of the case body 12 are joined (for example, welded together). The sealing plate 14 has an inner surface 14a (see FIG. 5) that is the surface facing the inside of the secondary battery 100 (the side facing the electrode body 20), and an outer surface 14b (see FIG. 5) that is the surface facing the outside. As shown in FIG. 1, the sealing plate 14 faces the bottom surface 12a of the case body 12.

[0027] As shown in FIG. 2, the sealing plate 14 has two terminal mounting holes 18 that penetrate the sealing plate 14 in the thickness direction. The terminal mounting holes 18 are provided at both ends of the sealing plate 14 in the long side direction Y. The terminal mounting hole 18 on one side (the left side in FIG. 2) is for the positive electrode, and the terminal mounting hole 18 on the other side (the right side in FIG. 2) is for the negative electrode. Here, the shape of the terminal mounting holes 18 is approximately circular in plan view. However, the terminal mounting holes 18 may also be elliptical or polygonal, such as rectangular or hexagonal, in plan view. The shape of the terminal mounting holes 18 may be selected appropriately to match the shape of the current collecting terminal 30.

[0028] The sealing plate 14 is also provided with a liquid inlet 15 and a gas release valve 17. The liquid inlet 15 is a through-hole for injecting the electrolyte into the battery case 10 after the sealing plate 14 is assembled to the case body 12. The liquid inlet 15 is sealed with a sealing member 16 after the electrolyte is injected. The gas release valve 17 is configured to break when the pressure inside the battery case 10 reaches or exceeds a predetermined value, thereby releasing gas inside the battery case 10 to the outside.

[0029] Although not particularly limited, the average thickness t1 of sealing plate 14 (the average thickness of the sealing plate excluding the thin-walled portion described below; the same applies below) is preferably approximately 0.3 mm or more, for example 0.5 mm or more, from the viewpoint of durability, etc., and is preferably approximately 4.0 mm or less, for example 3.0 mm or less, from the viewpoint of cost and energy density. The average thickness of sealing plate 14 may be thinner than the average thickness of case body 12.

[0030] As shown in FIG. 1 , the outer edge of the sealing plate 14 and the periphery of the opening 12h of the case body 12 are welded together, forming a weld 13 along the boundary (fitting portion) between the case body 12 and the sealing plate 14. This allows the sealing plate 14 to seal the opening 12h of the case body 12 without any gaps, thereby sealing the battery case 10. The weld 13 can be formed by welding, for example, laser welding. The weld 13 is formed by laser welding the fitting portion between the case body 12 and the sealing plate 14, melting the constituent metals of the case body 12 and the sealing plate 14. The weld 13 is located on the outer surface side of the sealing plate 14. The weld 13 connects the inner peripheral edge of the opening 12h of the case body 12 and the outer peripheral edge of the sealing plate 14 so that they are flush with each other. The weld 13 is formed around the entire periphery along the fitting portion between the sealing plate 14 and the case body 12.

[0031] As shown in FIG. 2, the current collecting terminals 30 are provided on both ends of the sealing plate 14 in the long side direction Y, one at a time. The current collecting terminal 30 located on one side of the sealing plate 14 in the long side direction Y (the left side in FIG. 2) is for the positive electrode, and the current collecting terminal 30 located on the other side (the right side in FIG. 2) is for the negative electrode. The current collecting terminals 30 are inserted through the terminal mounting holes 18 in the sealing plate 14. The current collecting terminals 30 are preferably made of metal. The current collecting terminal 30 for the positive electrode (i.e., the positive electrode terminal) is preferably made primarily of aluminum. Specifically, the current collecting terminal 30 for the positive electrode is more preferably made of aluminum or an aluminum alloy. On the other hand, the current collecting terminal 30 for the negative electrode (i.e., the negative electrode terminal) is preferably made primarily of copper. Specifically, the current collecting terminal 30 for the negative electrode is more preferably made of copper or a copper alloy. However, the current collecting terminal 30 may also be made by joining two conductive members together. For example, the positive electrode current collecting terminal 30 may be made of two different types of aluminum joined together. The negative electrode current collecting terminal 30 may have a portion connected to the current collector 50 made of copper or a copper alloy, and a portion exposed on the outer surface 14b of the sealing plate 14 made of aluminum or an aluminum alloy. The current collecting terminal 30 may be made of, for example, a clad material made of two metals. In this specification, "A is the main component" means that A is the largest component by mass among the components constituting the current collecting terminal.

[0032] The current collecting terminal 30 is electrically connected to a plate-shaped external conductive member 35 on the outside of the battery case 10. The external conductive member 35 is a member to which a bus bar is attached when electrically connecting multiple secondary batteries to each other. The external conductive member 35 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy, for example. However, the external conductive member 35 is not essential and can be omitted in other embodiments.

[0033] FIG. 4 is a diagram schematically illustrating a current collector terminal-sealing plate assembly 14A in which the sealing plate 14, the current collector terminal 30, and the insulating member 40 are integrally molded. FIG. 5 is a schematic cross-sectional view of the vicinity of the current collector terminal according to the first embodiment. FIG. 6 is a diagram schematically illustrating an electrode body 20 to which a second current collector 52 is attached. The electricity storage device disclosed herein includes a current collector terminal-sealing plate assembly 14A in which the sealing plate 14, the current collector terminal 30, and the insulating member 40 are integrally molded, as shown in FIG. 4. Note that in FIG. 4, in addition to the sealing plate 14, the current collector terminal 30, and the insulating member 40, the current collector 50 is also integrally molded.

[0034] As shown in FIG. 5 , the current collecting terminal 30 is arranged so that the sealing plate outer surface side 31 is exposed on the outer surface of the sealing plate 14. The current collecting terminal 30 is also arranged so that the sealing plate inner surface side 32 faces the inner surface of the sealing plate 14. In the example shown in FIG. 5 , the sealing plate inner surface side 32 of the current collecting terminal 30 is configured to be large enough to be inserted into the terminal mounting hole 18. This allows for favorable implementation of the integrated molding (insert molding) described below. However, the sealing plate outer surface side 31 may also be large enough to be inserted into the terminal mounting hole 18. The shape of the sealing plate outer surface side 31 of the current collecting terminal 30 in a planar view is not particularly limited. The shape of the sealing plate outer surface side 31 in a planar view may be a polygonal shape, such as a triangle, a rectangle, or a hexagon, or may be a perfect circle or an ellipse.

[0035] The current collecting terminal 30 is connected to the electrode assembly 20 via a current collector 50 inside the battery case 10. Specifically, the positive electrode side current collector 50 connects a positive electrode tab group 23 consisting of a plurality of positive electrode tabs 22t to the positive electrode side current collecting terminal 30. Furthermore, the negative electrode side current collector 50 connects a negative electrode tab group 25 consisting of a plurality of negative electrode tabs 24t to the negative electrode side current collecting terminal 30. As shown in FIG. 2 , the current collector 50 includes a first current collecting portion 51 and a second current collecting portion 52. The first current collecting portion 51 and the second current collecting portion 52 may be made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel.

[0036] As shown in FIG. 5 , the first current collecting portion 51 is disposed on the inner surface side of the sealing plate 14. The first current collecting portion 51 has a first region 51a and a second region 51b. The first current collecting portion 51 may be formed by bending a single member, for example, by pressing or by integrating multiple members by welding or the like. The first current collecting portion 51 is joined to the lower end of the current collecting terminal 30. The first current collecting portion 51 and the current collecting terminal 30 are joined by welding, for example, by ultrasonic welding, resistance welding, laser welding, or the like. Alternatively, the first current collecting portion 51 may be joined to the sealing plate 14 by being integrally molded together with the current collecting terminal 30 in an integral molding process described below. The first current collecting portion 51 and the current collecting terminal 30 may also be joined by mechanical processing, such as riveting.

[0037] The first region 51a of the first current collecting portion 51 is a region disposed between the sealing plate 14 and the electrode body 20. The first region 51a extends along the long side direction Y. The first region 51a extends horizontally along the inner surface 14a of the sealing plate 14. As shown in FIG. 5, an insulating member 40 is disposed between the sealing plate 14 and the first region 51a. The first region 51a is insulated from the sealing plate 14 by the insulating member 40. The first region 51a is connected to the sealing plate inner surface side 32 of the current collecting terminal 30. The second region 51b extends downward in the up-down direction Z from one end of the first region 51a in the long side direction Y (the left end in FIG. 5) along the short side wall 12c of the case body 12. As shown in FIG. 2, the second region 51b is connected to the second current collecting portion 52.

[0038] As shown in FIG. 2, the second current collecting portion 52 extends along the short side wall 12c of the case body 12. As shown in FIG. 6, the second current collecting portion 52 has a first connection portion 52a connected to the first current collecting portion 51 and a second connection portion 52b connected to the positive electrode tab group 23 or the negative electrode tab group 25. The first connection portion 52a and the first current collecting portion 51 are welded together by, for example, ultrasonic welding, resistance welding, laser welding, or the like. The second connection portion 52b is attached to the positive electrode tab group 23 or the negative electrode tab group 25 and is electrically connected to the multiple positive electrode tabs 22t or the negative electrode tabs 24t. As shown in FIG. 6, the second connection portion 52b extends along the up-down direction Z. The second connection portion 52b is disposed substantially perpendicular to the winding axis WL of the electrode assembly 20. The surface of the second connection portion 52b that is connected to the multiple positive electrode tabs 22t is disposed approximately parallel to the short side wall 12c of the case body 12. The second connection portion 52b is welded to the positive electrode tab group 23 or the negative electrode tab group 25 by ultrasonic welding, resistance welding, laser welding, or the like.

[0039] The insulating member 40 is a member that prevents electrical conduction between the sealing plate 14 and the current collecting terminal 30. As shown in Fig. 5, the insulating member 40 is disposed on the periphery 18a of the terminal mounting hole 18 in a state where it is integrally molded with the peripheral portion of the terminal mounting hole 18 of the sealing plate 14 and the current collecting terminal 30. In this specification, the "periphery of the terminal mounting hole" includes not only the edge of the terminal mounting hole but also the area surrounding it. Specifically, the periphery of the terminal mounting hole includes an area 5 mm to 10 mm from the end (edge) of the terminal mounting hole.

[0040] The insulating member 40 is made of a fluorine-based resin such as perfluoroalkoxyalkane (PFA) or polytetrafluoroethylene (PTFE), or a synthetic resin material such as polyphenylene sulfide (PPS). Of these, it is preferable that the insulating member 40 be made of polyphenylene sulfide, from the viewpoint of ensuring sufficient bonding strength.

[0041] As shown in FIG. 5 , the insulating member 40 has a first flange portion 41, a second flange portion 42, a cylindrical portion 43, and a protruding portion 44. The first flange portion 41, the second flange portion 42, the cylindrical portion 43, and the protruding portion 44 are integrally formed. The insulating member 40 also has a through-hole 40h penetrating in the up-down direction Z at a position corresponding to the terminal mounting hole 18 of the sealing plate 14. The first flange portion 41 is disposed on the outer surface of the sealing plate 14 and insulates the sealing plate outer surface 31 of the current collecting terminal 30 from the outer surface 14b of the sealing plate 14. As shown in FIG. 4 , the first flange portion 41 protrudes outward beyond the current collecting terminal 30 in a plan view and is exposed to the outside. The second flange portion 42 is disposed on the inner surface of the sealing plate 14 and insulates the sealing plate inner surface 32 of the current collecting terminal 30 from the inner surface 14a of the sealing plate 14. The second flange portion 42 extends horizontally along the inner surface 14a of the sealing plate 14. The outer shapes of the first flange portion 41 and the second flange portion 42 are larger than the outer shapes of the sealing plate outer surface side 31 and the sealing plate inner surface side 32 of the current collecting terminal 30.

[0042] The cylindrical portion 43 is located between the terminal mounting hole 18 and the shaft portion 33 of the current collecting terminal 30. The cylindrical portion 43 insulates the terminal mounting hole 18 from the shaft portion 33. As shown in FIG. 5, the protruding portion 44 is provided closer to the center of the sealing plate 14 than the second flange portion 42 in the long side direction Y. The protruding portion 44 extends downward in the up-down direction Z from one end of the second flange portion 42 in the long side direction Y (the right end portion in FIG. 5). The protruding portion 44 can face the curved portion of the electrode body 20. This prevents the electrode body 20 from coming into direct contact with the sealing plate 14 even if it moves slightly due to vibration or impact when the secondary battery 100 is in use.

[0043] The electricity storage device disclosed herein includes a current collector terminal-sealing plate assembly 14A in which a sealing plate 14, a current collector terminal 30, and an insulating member 40 are integrally molded, and in this current collector terminal-sealing plate assembly 14A, the insulating member 40 is disposed on the periphery 18a of the terminal mounting hole 18 in the sealing plate 14 while being integrally molded with the periphery of the terminal mounting hole 18 and the current collector terminal 30, and at least a portion of the periphery 18a of the terminal mounting hole 18 in the sealing plate 14 has a thin-walled portion 14s that is thinner than the surrounding area of ​​that portion. This increases the breaking strength of the entire battery, making it possible to provide a secondary battery 100 that is safer. While not intending to limit the technology disclosed herein, the reason for this effect is presumed to be as follows. The current collector terminal-sealing plate assembly 14A is firmly bonded so that the bond strength meets a predetermined standard. The portion of the sealing plate 14 that is integrally molded with the current collector terminal 30 and the insulating member 40 exhibits a sharp increase in apparent rigidity. That is, the portion integrally molded with the current collector terminal 30 and the insulating member 40 exhibits high rigidity, while the portion not involved in the integral molding (the portion containing only the sealing plate 14) exhibits relatively low rigidity. The inventors' investigations have revealed that stress is concentrated in the low-rigidity portion at the boundary between the high-rigidity portion and the low-rigidity portion, making the assembly particularly susceptible to fracture. More specifically, at the boundary between the case body 12 and the sealing plate 14 (e.g., the weld 13 described above), a difference in rigidity is likely to occur between the portion close to the integrally molded portion and the portion far from it. The portion close to the integrally molded portion exhibits a large difference in rigidity from the integrally molded portion, making it more susceptible to fracture. Therefore, in the secondary battery 100 disclosed herein, at least a portion of the periphery 18a of the terminal mounting hole 18 is configured as a thin portion that is thinner than the surrounding area of ​​that portion, in order to reduce the difference in rigidity between the integrally molded portion and the non-integrally molded portion and increase the breaking strength of the secondary battery 100. This suppresses stress concentration, making it possible to provide a secondary battery 100 with higher safety.

[0044] The thin-walled portion 14s is provided at the periphery 18a of the terminal mounting hole 18 of the sealing plate 14. The thin-walled portion 14s is formed in a region where the sealing plate 14 and the insulating member 40 contact each other. The thin-walled portion 14s is a portion where the thickness of the sealing plate 14 is thinner than the region adjacent to the thin-walled portion 14s. The thin-walled portion 14s can be a portion with a relatively small volume in the sealing plate 14.

[0045] The thin-walled portion 14s can be formed continuously or intermittently. The thin-walled portion 14s may be formed in a dashed line shape or may be formed by being divided into a plurality of parts. The thin-walled portion 14s can be a portion formed with a smaller cross-sectional area than its surroundings in the sealing plate 14. By providing the thin-walled portion 14s at at least a part of the periphery 18a of the terminal mounting hole 18 in the sealing plate 14, the difference in rigidity between the integrally molded portion and the portion not involved in the integral molding can be reduced. Thereby, it is possible to suppress stress from concentrating in a region with relatively low rigidity and suppress the battery case 10 from breaking, and it is possible to improve the breaking strength of the battery.

[0046] In the example shown in FIG. 5, the thin-walled portion 14s is a region having a predetermined thickness t2 at the periphery 18a of the terminal mounting hole 18. The thickness t of the thin-walled portion 14s is not particularly limited, but is preferably, for example, (1 / 10)×t1≦t2<t1, more preferably (1 / 8)×t1≦t2<t1, and even more preferably (1 / 5)×t1≦t2<(4 / 5)×t1 with respect to the average thickness t1 of the sealing plate 14. Specifically, for example, the thickness t2 of the thin-walled portion 14s is preferably 0.1 mm to 1 mm, and for example, it is good to be 0.1 mm to 0.5 mm.

[0047] In the first embodiment, as shown in FIG. 5 , the thin-walled portion 14s includes a groove-shaped portion (hereinafter referred to as the “first groove portion 14e”) recessed from the outer surface of the sealing plate 14 relative to its surroundings. As shown in FIG. 5 , the first groove portion 14e is recessed from the outer surface of the sealing plate 14 toward the inner surface thereof by a predetermined groove depth d1. The first groove portion 14e may be formed in a substantially annular shape along the edge of the terminal mounting hole 18. The first groove portion 14e is a region having the predetermined groove depth d1 and extending a predetermined length L1 radially along the periphery 18a of the terminal mounting hole 18. By providing the first groove portion 14e recessed from the periphery on the outer surface of the sealing plate 14, the rigidity of the integrally molded portion can be reduced. This reduces the difference in rigidity between the integrally molded portion and the portion not involved in the integral molding.

[0048] As shown in Figure 5, it is preferable that a portion of the sealing plate outer surface 31 of the current collecting terminal 30 is disposed in the groove-shaped first groove 14e. The portion of the sealing plate outer surface 31 of the current collecting terminal 30 is disposed in a position facing the first groove 14e of the sealing plate 14, with the insulating member 40 sandwiched between them. In the current collecting terminal-sealing plate assembly 14A, the area where the sealing plate 14 and the current collecting terminal 30 face each other tends to have particularly high apparent rigidity. By providing the first groove 14e in the sealing plate 14 in this area and reducing the total volume of the sealing plate 14 and the current collecting terminal 30, the apparent rigidity can be reduced. Therefore, by providing a thin-walled portion 14s including a first groove portion 14e on the outer surface 14b of the sealing plate 14 at the periphery 18a of the terminal mounting hole 18 and arranging a part of the collector terminal 30 in the first groove portion 14e, the rigidity difference in the collector terminal-sealing plate assembly 14A can be reduced and the breaking strength can be improved.

[0049] When the secondary battery 100 has an external conductive member 35 and the current collecting terminal 30 and the external conductive member 35 are connected, it is preferable that at least a portion of the external conductive member 35 be disposed in the first groove 14e described above, as shown in Fig. 5. It is more preferable that the entire area of ​​the external conductive member 35 where the external conductive member 35 and the sealing plate 14 face each other be disposed in the first groove 14e. This reduces the total volume of the sealing plate 14 and the external conductive member 35, even when the external conductive member 35 is present, and makes it possible to reduce the difference in rigidity within the current collecting terminal-sealing plate assembly 14A.

[0050] The maximum groove depth d1 (maximum length along the thickness direction of the sealing plate 14) of the first groove portion 14e may be appropriately set depending on the battery design and is not particularly limited. For example, when the average thickness (average length in the vertical direction Z) of the sealing plate outer surface 31 of the current collecting terminal 30 is thickness t3, the groove depth d1 of the first groove portion 14e preferably satisfies d1≧(1 / 5)×t3, more preferably d1≧(1 / 2)×t3, or may be d1=t3 (i.e., the groove depth d1 of the first groove portion 14e and the thickness t1 of the sealing plate outer surface 31 are the same). By setting the groove depth d1 of the first groove portion 14e to a depth equal to or greater than 1 / 5 of the thickness t3 of the sealing plate outer surface 31, the effect of reducing the total volume as described above is fully exerted, and an increase in apparent rigidity can be suitably suppressed. On the other hand, if the groove depth is too deep, it becomes difficult to connect the current collecting terminal 30 (or the external conductive member 35) to the bus bar, which is undesirable. From this perspective, it is preferable that d1≦t3, and more preferably that d1≦(3 / 4)t3. Specifically, for example, the groove depth d1 of the first groove portion 14e is about 0.2 mm to 1.9 mm (preferably 0.5 mm to 1 mm).

[0051] The maximum radial length L1 of the first groove 14e is not particularly limited, but is preferably a length that allows placement of the sealing plate outer surface 31 of the current collector terminal 30. Furthermore, when the secondary battery 100 has an external conductive member 35 and the current collector terminal 30 is connected to the external conductive member 35, the maximum radial length L1 of the first groove 14e is preferably a length that allows placement of the sealing plate outer surface 31 of the current collector terminal 30 and the external conductive member 35. Specifically, for example, the maximum radial length L1 of the first groove 14e may be approximately 1 mm to 10 mm (preferably 2 mm to 8 mm).

[0052] In the current collector terminal-sealing plate assembly 14A, it is preferable that a roughened area 14r is provided on at least a portion of the surfaces of the sealing plate 14 and the current collector terminal 30. Roughening 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 between the insulating member 40 and the sealing plate 14. Therefore, the roughened area 14r is an area with more irregularities than its surroundings.

[0053] The roughened area 14r may be provided on the sealing plate 14. For example, the roughened area 14r is preferably provided on at least a portion of the surface of the thin-walled portion 14s that contacts the insulating member 40. The roughened area 14r may be provided on the entire surface of the thin-walled portion 14s that contacts the insulating member 40. As described above, the roughened area 14r exhibits an anchoring effect and tends to have particularly high rigidity. By arranging such a roughened area 14r and the thin-walled portion 14s so that they overlap, the rigidity difference within the current collector terminal-sealing plate assembly 14A can be reduced. Therefore, the fracture strength of the current collector terminal-sealing plate assembly 14A can be improved while ensuring sufficient bondability and airtightness, thereby providing a safer electricity storage device.

[0054] The roughened area 14r may be provided on the current collecting terminal 30. When the current collecting terminal 30 is provided with the roughened area 14r, the portion where the roughened area 14r is provided is preferably positioned so as to overlap at least the thin-walled portion 14s in the up-down direction Z. For example, the roughened area 14r is preferably provided on the surface of the sealing plate outer surface 31 of the current collecting terminal 30, in a position facing the sealing plate 14 with the insulating member 40 sandwiched therebetween. This can improve the airtightness of the current collecting terminal-sealing plate assembly 14A and the breaking strength of the battery.

[0055] Although not particularly limited, the roughened area 14r may be provided on both the sealing plate 14 and the current collecting terminal 30. For example, the roughened area 14r is preferably provided on the surface of the thin portion 14s that contacts the insulating member 40 and the surface of the sealing plate outer surface 31 of the current collecting terminal 30, at positions that face each other across the thin portion 14s and the insulating member 40. This makes it possible to further ensure the bondability and airtightness between the current collecting terminal 30 and the sealing plate 14, while reducing the difference in rigidity within the current collecting terminal-sealing plate assembly 14A.

[0056] Although not particularly limited, roughened area 14r may be provided on current collector 50. Specifically, roughened area 14r is preferably provided on the surface of first current collecting part 51 at a position facing thin portion 14s with insulating member 40 interposed therebetween. This improves the bond between current collector 50 and insulating member 40, while suitably reducing the rigidity of the region where current collecting terminal 30, sealing plate 14, and current collector 50 overlap, thereby improving breaking strength.

[0057] The thin-walled portion 14s is preferably provided on the periphery 18a of each of the two terminal mounting holes 18. This more appropriately reduces the difference in rigidity within the sealing plate 14. Although not particularly limited, when the negative electrode side current collector terminal 30 is primarily made of copper and the positive electrode side current collector terminal 30 is primarily made of aluminum, the thin-walled portion provided on the periphery 18a of the negative electrode side terminal mounting hole 18 is preferably thinner (thicker) than the thin-walled portion provided on the periphery 18a of the positive electrode side terminal mounting hole 18. According to the results of studies by the present inventors, the negative electrode side current collector terminal 30, which is primarily made of copper, tends to have higher strength than the positive electrode side current collector terminal 30, which is primarily made of aluminum. Therefore, the periphery 18a of the negative electrode side terminal mounting hole 18 tends to have higher apparent rigidity than the periphery 18a of the positive electrode side terminal mounting hole 18. Therefore, in order to reduce the difference in rigidity within the sealing plate 14, it is preferable that the thin-walled portion provided on the periphery 18a of the terminal mounting hole 18 on the negative electrode side is thinner than the thin-walled portion provided on the periphery 18a of the terminal mounting hole 18 on the positive electrode side.

[0058] <Method of manufacturing an electricity storage device> Hereinafter, a lithium ion secondary battery will be described as an example of a preferred embodiment of the method for manufacturing an electricity storage device disclosed herein, but it is not intended that the application be limited to such batteries.

[0059] The secondary battery 100 described above may include the steps of preparing the sealing plate 14, the current collecting terminal 30, and other necessary components, integrally molding the sealing plate 14 and the current collecting terminal 30, and assembling the integrally molded current collecting terminal-sealing plate assembly 14A with the case body 12. Note that other steps may also be included at any stage.

[0060] In the preparation step, the sealing plate 14, the current collecting terminal 30, and the electrode body 20 are prepared. Here, the current collecting terminal 30 is prepared so that the inner surface 32 of the sealing plate can be inserted into the terminal mounting hole 18. The thin-walled portion 14s described above can be formed by a conventionally known method such as press working, cutting, or laser processing.

[0061] The electrode assembly 20 can be fabricated according to a known method. When the electrode assembly 20 is a wound electrode assembly as shown in FIG. 3 , the wound electrode assembly can be prepared, for example, as follows. First, a strip-shaped positive electrode sheet 22 and a strip-shaped negative electrode sheet 24 are stacked so that they are insulated by two strip-shaped separators 26. The positive electrode tab 22t of the positive electrode sheet 22 and the negative electrode tab 24t of the negative electrode sheet 24 are overlapped so that they protrude in opposite directions from the ends of the two separators 26 in the long side direction Y. Next, the prepared laminate is wound in the longitudinal direction around the winding axis. The winding of the laminate can be performed according to a known method. The wound laminate is pressed to produce a flat wound electrode assembly. This pressing can be performed using a known press device commonly used to manufacture flat wound electrodes, and is not particularly limited. In this manner, the electrode assembly 20 can be prepared.

[0062] FIG. 7 is a schematic diagram of a molding die 120. In the integral molding process, the sealing plate 14 and the current collector terminal 30 are integrated by insert molding to produce a current collector terminal-sealing plate assembly 14A. Insert molding can be performed according to a conventionally known method. Specifically, insert molding can be performed using a molding die 120 having a lower die 121 and an upper die 122 as shown in FIG. 7, by a method including a part setting step, a positioning step, an upper die setting step, an injection molding step, an upper die release step, and a part removal step.

[0063] In the part setting process, the sealing plate 14 and the current collecting terminal 30 are attached to the molding die 120. First, the current collecting terminal 30 is inserted into the terminal mounting hole 18 of the sealing plate 14. As described above, the current collecting terminal 30 is configured with a size that allows the sealing plate inner surface 32 to be inserted into the terminal mounting hole 18. Therefore, the current collecting terminal 30 is inserted into each of the two terminal mounting holes 18 from the sealing plate inner surface 32. Then, the sealing plate 14 with the current collecting terminals 30 inserted into the two terminal mounting holes 18 is attached to the recess 121a of the lower die 121.

[0064] In the positioning process, the sealing plate 14 and the current collecting terminal 30 are positioned. After the sealing plate 14 and the current collecting terminal 30 are attached to the lower mold 121, the positioning process begins when a predetermined operation, such as pressing a switch, is performed. Specifically, the predetermined operation, such as pressing a switch, moves the slide members 123a and 123b, which have been retracted to the rear side, to the front side. Then, the slide members 123a and 123b clamp the respective current collecting terminals 30. The slide members 123a and 123b support the current collecting terminals 30 and position them in the desired positions.

[0065] In the upper mold setting step, upper mold 122 is set so as to sandwich sealing plate 14 and current collecting terminal 30 set in lower mold 121 in the vertical direction Z. Although not shown, upper mold 122 may have a sealing portion that abuts against lower mold 121, a resin supply portion that supplies resin, and a recess into which the supplied resin flows. The recess of upper mold 122 is positioned so as to face recess 121a of lower mold 121 with sealing plate 14 and current collecting terminal 30 sandwiched therebetween.

[0066] In the injection molding process, resin is supplied (injected) from a resin supply unit to integrally mold the sealing plate 14 and the current collecting terminal 30. In the injection molding process, first, the molding die 120 is heated. The heating temperature varies depending on the type of resin and is not particularly limited, but may be, for example, approximately 100°C to 200°C. Once heating of the molding die 120 is complete, molten resin is supplied from the resin supply unit. The supplied resin fills the recesses in the upper die 122 and then passes through the terminal mounting hole 18 to fill the recesses 121a in the lower die 121. Thereafter, the molding die 120 and the molded product are cooled. This allows the sealing plate 14 and the current collecting terminal 30 to be integrally molded.

[0067] In the upper die release step, the upper die 122 rises and separates from the lower die 121. Then, in the component removal step, the molded product is removed from the lower die 121. This makes it possible to produce a current collector terminal-sealing plate assembly 14A in which the current collector terminal 30 and the sealing plate 14 are molded integrally. Note that a step of removing burrs that occurred during molding may be included after the component removal step.

[0068] In the assembly process, with the prepared electrode body 20 housed inside the case body 12, the current collector terminal-sealing plate assembly 14A is attached to the case body 12 and sealed. Specifically, first, the second current collector 52 is connected to the electrode body 20. Next, the first current collector 51 is attached to the current collector terminal 30 of the current collector terminal-sealing plate assembly 14A. Then, the first current collector 51 is connected to the second current collector 52. This completes the connection between the current collector terminal-sealing plate assembly 14A and the electrode body 20. The electrode body 20 attached to the current collector terminal-sealing plate assembly 14A is inserted through the opening 12h of the case body 12. At this time, it is preferable to insert the electrode body 20 so that its winding axis WL is oriented along the bottom surface 12a (i.e., the winding axis WL is oriented parallel to the long side direction Y). With the electrode body 20 housed inside the case body 12, the current collector terminal-sealing plate assembly 14A is joined to the periphery of the opening 12h of the case body 12 by laser welding or the like. Then, the electrolyte is poured through the liquid filling hole 15, and the liquid filling hole 15 is closed with the sealing member 16, thereby sealing the secondary battery 100. In this manner, the secondary battery 100 can be manufactured.

[0069] <Battery uses> The above-described power storage device 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 an electric vehicle (BEV). Such a power storage device can also be suitably used in a configuration in which a plurality of the power storage devices are arranged in a predetermined arrangement direction and a load is applied along the arrangement direction by a restraining mechanism (for example, an assembled battery in which a plurality of lithium-ion secondary batteries are arranged in a predetermined direction).

[0070] The above-described embodiment is merely one example of the power storage device disclosed herein. The technology disclosed herein can be embodied in various other forms. Other embodiments of the technology disclosed herein will be described below.

[0071] Second Embodiment For example, in the first embodiment described above, the thin-walled portion 14s includes a groove-shaped portion (first groove portion 14e) on the outer surface side of the sealing plate 14 that is recessed from its surroundings. However, the shape of the thin-walled portion is not limited to this. FIG. 8 is a view corresponding to FIG. 5 according to the second embodiment. As shown in FIG. 8, in the second embodiment, the thin-walled portion 214s includes a groove-shaped portion (hereinafter referred to as "second groove portion 214f") on the inner surface side of the sealing plate 214 that is recessed from its surroundings. Note that other than this, the second embodiment may be the same as the first embodiment described above, and detailed description thereof will be omitted.

[0072] As shown in FIG. 8 , the second groove 214f ​​is recessed from the inner surface of the sealing plate 214 toward the outer surface by a predetermined groove depth d2. The second groove 214f ​​may be formed in a substantially annular shape along the edge of the terminal mounting hole 218. The second groove 214f ​​is a region having the predetermined groove depth d2 and extending a predetermined length L2 in the radial direction on the periphery 218a of the terminal mounting hole 218. By providing the second groove 214f, which is recessed from the surrounding area on the inner surface of the sealing plate at the periphery 218a of the terminal mounting hole 218 of the sealing plate 214, the rigidity of the integrally molded portion can be reduced. This reduces the difference in rigidity between the integrally molded portion and the portion not involved in the integral molding.

[0073] 8, it is preferable that a portion of the sealing plate inner surface side 232 of the current collecting terminal 230 is disposed in the groove-shaped second groove 214f. The portion of the sealing plate inner surface side 232 of the current collecting terminal 230 is disposed in a position facing the second groove 214f ​​of the sealing plate 214, with the insulating member 240 sandwiched between them. In the current collecting terminal-sealing plate assembly, the area where the sealing plate 214 and the current collecting terminal 230 face each other tends to have particularly high apparent rigidity. By providing the second groove 214f ​​in the sealing plate 214 in this area and reducing the total volume of the sealing plate 214 and the current collecting terminal 230, it is possible to reduce the apparent rigidity. Therefore, by providing a thin-walled portion 214s including a second groove portion 214f ​​on the inner surface 214a of the sealing plate 214 around the periphery of the terminal mounting hole 218 and arranging a part of the current collecting terminal 230 in the second groove portion 214f, the rigidity difference in the current collecting terminal-sealing plate assembly can be reduced and the breaking strength can be improved.

[0074] 8, when the secondary battery 200 has a current collector 250 extending along the long side direction Y, it is preferable that at least a portion of the current collector (more specifically, the first current collecting portion 251) be disposed in the second groove 214f. It is more preferable that the entire area of ​​the first current collecting portion 251 where the first current collecting portion 251 and the sealing plate 214 face each other be disposed in the second groove 214f. This reduces the total volume of the sealing plate 214 and the current collector 250, even in the area where the current collector 250 and the sealing plate 214 face each other, and makes it possible to reduce the difference in rigidity within the current collecting terminal-sealing plate assembly.

[0075] The groove depth d2 (maximum length in the thickness direction of the sealing plate 214) of the second groove portion 214f ​​may be appropriately set depending on the battery design and is not particularly limited. For example, when the average thickness (average length in the vertical direction Z) of the sealing plate inner surface 232 of the current collecting terminal 230 is thickness t4, the groove depth d2 of the second groove portion 214f ​​preferably satisfies d2≧(1 / 5)×t4, more preferably d2≧(1 / 2)×t4, or may be d2=t4 (i.e., the groove depth d2 of the second groove portion 214f ​​and the thickness t4 of the sealing plate inner surface 232 are the same). By setting the groove depth d2 of the second groove portion 214f ​​to a depth equal to or greater than 1 / 5 of the thickness t4 of the sealing plate inner surface 232, the effect of reducing the total volume as described above is fully exerted, and an increase in apparent rigidity can be suitably suppressed. Although there is no particular upper limit to the groove depth d2, it is preferable that d2≦2×t4, and more preferably that d2≦1.5×t4.

[0076] Furthermore, although not particularly limited, when the average thickness (average length in the vertical direction Z) of the current collector 250 (more specifically, the first current collecting portion 251) is defined as thickness t5, the groove depth d2 of the second groove 214f ​​is preferably at least 1 / 5 of the sum of the thickness t4 of the sealing plate inner surface 232 and the thickness t5 of the first current collecting portion 51. That is, it is preferable that d2≧(1 / 5)×(t4+t5). The groove depth d2 of the second groove 214f ​​is preferably, for example, (1 / 5)×(t4+t5)≦d2≦(t4+t5), and more preferably (1 / 2)×(t4+t5)≦d2≦(t4+t5). This allows the rigidity difference within the current collecting terminal-sealing plate assembly to be suitably reduced. Specifically, for example, the groove depth d2 of the second groove 214f ​​is preferably approximately 0.2 mm to 1.9 mm (preferably 0.5 mm to 1 mm).

[0077] The maximum radial length L2 of the second groove 214f ​​is not particularly limited, but is preferably a length that allows the sealing plate inner surface side 232 of the current collector terminal 230 to be arranged therein. Furthermore, when the secondary battery 200 has a current collector 250 that extends along the long side direction Y, the maximum radial length L2 of the second groove 214f ​​is preferably a length that allows the sealing plate inner surface side 232 of the current collector terminal 230 and the current collector 250 to be arranged therein. Specifically, for example, the maximum radial length L2 of the second groove 214f ​​may be approximately 1 mm to 10 mm (preferably 2 mm to 8 mm).

[0078] In a current collecting terminal-sealing plate assembly in which the current collecting terminal 230 and the sealing plate 214 are integrally molded, at least a portion of the surfaces of the sealing plate 214 and the current collecting terminal 230 is preferably provided with a roughened area 214r. The roughened area 214r may be provided on the sealing plate 214. For example, the roughened area 214r is preferably provided on at least a portion of the surface of the thin-walled portion 214s that contacts the insulating member 240. The roughened area 214r may be provided on the entire surface of the thin-walled portion 214s that contacts the insulating member 240. As described above, the roughened area 214r exhibits an anchoring effect and tends to have particularly high rigidity. By arranging such a roughened area 214r and the thin-walled portion 214s so that they overlap, the rigidity difference within the current collecting terminal-sealing plate assembly can be reduced. Therefore, the breaking strength can be improved while the bonding strength and airtightness of the current collector terminal-sealing plate assembly are sufficiently ensured, and an electricity storage device with even greater safety can be provided.

[0079] The roughened area 214r may be provided on the current collecting terminal 230. When the current collecting terminal 230 has the roughened area 214r, the portion where the roughened area 214r is provided is preferably positioned so as to overlap at least the thin-walled portion 214s in the up-down direction Z. For example, the roughened area 214r is preferably provided on the surface of the sealing plate inner surface 232 of the current collecting terminal 30, in a position facing the sealing plate 214 with the insulating member 240 sandwiched therebetween. This can improve the airtightness of the current collecting terminal-sealing plate assembly and the breaking strength of the battery.

[0080] Although not particularly limited, roughened area 214r may be provided on both sealing plate 214 and current collecting terminal 230. For example, roughened area 214r is preferably provided on the surface of thin portion 214s that comes into contact with insulating member 240 and the surface of sealing plate inner surface 232 of current collecting terminal 230, at positions that face each other across thin portion 214s and insulating member 240. This makes it possible to further ensure the bondability and airtightness between current collecting terminal 230 and sealing plate 214, while reducing the difference in rigidity within the current collecting terminal-sealing plate assembly.

[0081] Although not particularly limited, roughened area 214r may be provided on current collector 250. Specifically, roughened area 214r is preferably provided on the surface of first current collecting part 251 at a position facing thin portion 214s across insulating member 240. This makes it possible to suitably reduce the rigidity of the region where current collecting terminal 230, sealing plate 214, and current collector overlap, thereby improving the breaking strength.

[0082] Such a secondary battery 200 can be fabricated in substantially the same manner as in the first embodiment. Specifically, the fabrication process may include the steps of preparing the sealing plate 214, the current collecting terminal 230, and other necessary components, integrally molding the sealing plate 214 and the current collecting terminal 230, and assembling the integrally molded current collecting terminal-sealing plate assembly with the case body. When attaching the current collecting terminal 230 to the terminal mounting hole 218 of the sealing plate 214, it is preferable to insert the terminal mounting hole 218 from the outer surface 231 of the sealing plate.

[0083] <Third embodiment> For example, in the first embodiment described above, the thin-walled portion 14s includes a groove-shaped portion (first groove portion 14e) on the outer surface of the sealing plate 14 that is recessed from its surroundings. Furthermore, in the second embodiment described above, the thin-walled portion 214s includes a groove-shaped portion (second groove portion 214f) on the inner surface of the sealing plate 14 that is recessed from its surroundings. However, the configuration of the thin-walled portion is not limited thereto. FIG. 9 is a view corresponding to FIG. 5 according to the third embodiment. As shown in FIG. 9, in the third embodiment, the thin-walled portion 314s includes a groove-shaped portion (first groove portion 314e) on the outer surface of the sealing plate 314 that is recessed from its surroundings, and a groove-shaped portion (second groove portion 314f) on the inner surface of the sealing plate 314 that is recessed from its surroundings. Note that other than this, the third embodiment may be similar to the first embodiment and / or the second embodiment described above, and detailed description thereof will be omitted.

[0084] As shown in FIG. 8, the first groove 314e is recessed from the outer surface toward the inner surface of the sealing plate 314. The second groove 314f is recessed from the inner surface toward the outer surface of the sealing plate 314. By providing the first groove 314e and the second groove 314f, which are recessed more than their surroundings, on both the inner surface 314a and the outer surface 314b of the sealing plate 314, the insulating member 340 can further reduce the total volume of the portion where the sealing plate 314 and the current collecting terminal 330 are integrally molded. This can further reduce the difference in rigidity between the integrally molded portion and the portion not involved in the integral molding, thereby improving the breaking strength.

[0085] The first groove portion 314e formed on the outer surface side of the sealing plate 314 and the second groove portion 314f formed on the inner surface side may be formed in an overlapping region in the vertical direction Z. In that case, the sum of the maximum groove depth d3 of the first groove portion 314e (the maximum length in the direction along the thickness direction of the sealing plate 314) and the maximum groove depth d4 of the second groove portion 314f (the maximum length in the direction along the thickness direction of the sealing plate 314) is formed so as to be less than the average thickness t6 of the sealing plate 314. For example, it is preferable that (d3 + d4) < t6 and (d3 + d4) ≦ (2 / 3) × t6. Within such a range, it is also preferable from the viewpoint of ensuring the strength of the periphery 318a of the terminal mounting hole 318 to be a certain level or more. Also, from the viewpoint of reducing the total volume, it is preferable that (d3 + d4) ≧ (2 / 5) × t6, and it is more preferable that (d3 + d4) ≧ (1 / 2) × t6. By providing the thin-walled portion 314s including the first groove portion 314e and the second groove portion 314f at the periphery 318a of the terminal mounting hole 318 so as to be within the above-described range, a more safe power storage device can be provided. Note that the groove depth d3 of the first groove portion 314e and the groove depth d4 of the second groove portion 314f may be the same depth or different depths. Also, the maximum length L3 in the radial direction of the first groove portion 314e and the maximum length L4 in the radial direction of the second groove portion 314f are not particularly limited. Such maximum length L3 and maximum length L4 may be the same length or different lengths. The groove depths and maximum lengths of such first groove portion 314e and second groove portion 314f can be appropriately changed according to the shape of the current collecting terminal 330 and the like.

[0086] In a current collecting terminal-sealing plate assembly in which the current collecting terminal 330 and the sealing plate 314 are integrally molded, it is preferable that a roughened area 314r be provided on at least a portion of the surfaces of the sealing plate 314 and the current collecting terminal 330. In the example shown in Fig. 9, the roughened area 314r is provided on both the sealing plate 314 and the current collecting terminal 330 around the periphery of the terminal mounting hole 318. Specifically, it is preferable that the roughened area 314r be provided on the surface of the thin portion 314s that comes into contact with the insulating member 40, on the surface of the sealing plate outer surface 331 of the current collecting terminal 330 at a position facing the thin portion 314s with the insulating member 40 interposed therebetween, and on the surface of the sealing plate inner surface 332 of the current collecting terminal 330 at a position facing the thin portion 314s with the insulating member 340 interposed therebetween. By arranging the first groove portion 314e and the second groove portion 314f in an area where the roughened area 314r overlaps, the difference in rigidity between the integrally molded portion and the portion not involved in the integral molding can be suitably reduced.

[0087] Such a secondary battery 300 can be fabricated in substantially the same manner as in the first embodiment. Specifically, the fabrication process may include the steps of preparing a sealing plate 314, a current collecting terminal 330, and other necessary components, integrally molding the sealing plate 314 and the current collecting terminal 330, and assembling the integrally molded current collecting terminal-sealing plate assembly with the case body. When attaching the current collecting terminal 330 to the terminal mounting hole 318 of the sealing plate 314, the current collecting terminal 330 can be inserted into the terminal mounting hole 318 by passing it through the terminal mounting hole 318 while tilting the sealing plate outer surface 331 or the sealing plate inner surface 332, as shown in FIG. 9 .

[0088] <Fourth embodiment> For example, in the first to third embodiments described above, the thin-walled portion includes a groove-shaped portion (first groove portion) on the outer surface of the sealing plate that is recessed from its surroundings, and / or a groove-shaped portion (second groove portion) on the inner surface of the sealing plate that is recessed from its surroundings. However, the form of the thin-walled portion is not limited to this. FIG. 10 is a view corresponding to FIG. 5 according to the fourth embodiment. As shown in FIG. 10, in the fourth embodiment, the thin-walled portion 414s has non-through holes 414j or through holes 414h on the outer surface and / or inner surface of the sealing plate 414. Note that other than this, the fourth embodiment may be similar to the first embodiment described above, and detailed description thereof will be omitted.

[0089] Fig. 11 is a schematic plan view of a current collecting terminal-sealing plate assembly 414A according to the fifth embodiment. As shown in Figs. 10 and 11, in the fourth embodiment, the thin-walled portion 414s is configured by non-through holes 414j and / or through holes 414h formed around the periphery of the terminal mounting hole 18. Due to the formation of the non-through holes 414j and / or through holes 414h, the volume of the thin-walled portion 414s is relatively small within the sealing plate 414. This prevents stress from concentrating in an area with relatively low rigidity, thereby preventing the battery case from breaking.

[0090] In the fourth embodiment, the thin-walled portion 414s may be formed only with non-through holes 414j, or only with through holes 414h, or may be formed with both non-through holes 414j and through holes 414h. The non-through holes 414j and the through holes 414h are formed in the region where the sealing plate 414 and the insulating member 440 contact each other. Although there may be only one non-through hole 414j, it is preferable that a plurality of non-through holes 414j are formed in the region where the sealing plate 414 and the insulating member 440 contact each other. Furthermore, although there may be only one through hole 414h, it is preferable that a plurality of non-through holes 414h are formed in the region where the sealing plate 414 and the insulating member 440 contact each other. This more suitably reduces the difference in rigidity between the integrally molded portion and the portion not involved in the integral molding of the current collecting terminal-sealing plate assembly.

[0091] When a plurality of non-through holes 414j and through holes 414h are formed, their formation positions are not particularly limited as long as they are in the region where the sealing plate 414 and the insulating member 440 contact each other. Preferably, the non-through holes 414j and / or the through holes 414h are arranged approximately evenly in the region where the sealing plate 414 and the insulating member 440 contact each other. Specifically, as shown in FIG. 11 , the non-through holes 414j and / or the through holes 414h are arranged symmetrically with respect to the center line CL in the short-side direction of the sealing plate 414. This prevents stress from concentrating in portions where the non-through holes 414j or the through holes 414h are not formed.

[0092] Preferably, a plurality of non-through holes 414j are formed around the terminal mounting hole 418 at a predetermined depth d5 ​​and at a predetermined interval (pitch). In the example shown in FIG. 10, the non-through holes 414j are provided on the inner surface side of the sealing plate 414. However, the non-through holes 414j may also be provided on the outer surface side of the sealing plate 414. The non-through holes 414j may have a perfect circular shape, an elliptical shape, a rectangular shape, a hexagonal shape, or the like in a plan view. In particular, a perfect circular shape is preferable from the viewpoint of suitably reducing the volume of the sealing plate 414. The maximum diameter L5 of the non-through holes 414j is not particularly limited, but may be, for example, approximately 0.05 mm to 0.5 mm. The maximum depth d5 ​​of the non-through holes 414j (the maximum length in the direction along the terminal mounting hole 418) is not particularly limited as long as it is shorter than the average thickness t5 of the sealing plate 414. The maximum depth d5 ​​of non-through holes 414j may be adjusted as appropriate to achieve the desired strength of sealing plate 414. As an example, the maximum depth d5 ​​of non-through holes 414j may be approximately 0.1 mm to 1 mm.

[0093] The through holes 414h are portions that penetrate from the outer surface side to the inner surface side along the thickness direction of the sealing plate 414. It is preferable that a plurality of the through holes 414h are formed at a predetermined interval (pitch) around the terminal mounting hole 418. The maximum diameter L6 of the through holes 414h is not particularly limited. The maximum diameter L6 of the through holes 414h may be approximately the same as the maximum diameter L5 of the non-through holes 414j described above. Specifically, the maximum diameter L6 of the through holes 414h may be, for example, approximately 0.05 mm to 0.5 mm.

[0094] In an embodiment in which the thin-walled portion 414s includes the non-through holes 414j and / or the through holes 414h, a roughened area 414r is preferably provided on at least a portion of the surface of the current collecting terminal 430. The roughened area 414r is preferably provided, for example, on the surface of the inner surface 432 of the sealing plate of the current collecting terminal 430, at a position where the current collecting terminal 430 and the sealing plate 414 face each other with the insulating member 440 interposed therebetween. Alternatively, the roughened area 414r is preferably provided, for example, on the surface of the inner surface 432 of the sealing plate of the current collecting terminal 430, at a position where the current collecting terminal 430 and the sealing plate 414 face each other with the insulating member 440 interposed therebetween. The roughened area 414r may be provided so as to surround each of the non-through holes 414j and / or the through holes 414h. By overlapping the positions of the thin-walled portion 414s and the roughened area 414r, the breaking strength can be improved while sufficiently ensuring the bonding and airtightness of the collector terminal-sealing plate assembly, thereby providing an electricity storage device with superior safety.

[0095] In the fourth embodiment, the non-through holes 414j and / or the through holes 414h may be provided in a portion other than the roughened area 414r. Specifically, the non-through holes 414j and / or the through holes 414h may be provided in a portion other than the roughened area 414r where the insulating member 440 and the sealing plate 414 are in contact. By arranging the non-through holes 414j and / or the through holes 414h in a portion other than the roughened area 414r, it is possible to distribute the locations where the rigidity changes suddenly. This reduces the concentration of stress.

[0096] Such a secondary battery 400 can be fabricated in substantially the same manner as in the first embodiment. Specifically, the fabrication process may include the steps of preparing the sealing plate 414, the current collecting terminal 430, and other necessary components, integrally molding the sealing plate 414 and the current collecting terminal 430, and assembling the integrally molded current collecting terminal-sealing plate assembly with the case body. The blind holes 414j and the through holes 414h can be fabricated by conventional methods such as laser processing, drilling, and etching.

[0097] 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.

[0098] 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 case body having an opening; a sealing plate having a terminal mounting hole and sealing the opening; an electrode body housed inside the case body; a current collecting terminal having one end electrically connected to the electrode body inside the case body and the other end passing through the terminal mounting hole and exposed on the outer surface of the sealing plate; and an insulating member arranged between the sealing plate and the current collecting terminal, wherein the insulating member is arranged on the periphery of the terminal mounting hole in a state where it is integrally molded with the peripheral portion of the terminal mounting hole in the sealing plate and the current collecting terminal, and at least a portion of the periphery of the terminal mounting hole in the sealing plate forms a thin-walled portion that is thinner than the surrounding area of ​​that portion. Item 2: The electricity storage device according to Item 1, wherein the thin portion includes a groove-shaped portion on the outer surface side of the sealing plate that is recessed from its surroundings, and a portion of the outer surface side of the sealing plate of the current collecting terminal is disposed in the recessed groove-shaped portion. Item 3: The electricity storage device according to Item 1 or 2, wherein the thin portion includes a groove-shaped portion on the inner surface of the sealing plate that is recessed from its surroundings, and a portion of the collector terminal on the inner surface of the sealing plate is disposed in the recessed groove-shaped portion. Item 4: The electricity storage device according to any one of Items 1 to 3, wherein the thin portion has blind holes or through holes on the outer surface side and / or the inner surface side of the sealing plate. Item 5: The electricity storage device according to any one of Items 1 to 4, wherein the surface of the thin-walled portion that contacts the insulating member and / or the surface of the current collecting terminal that faces the thin-walled portion across the insulating member has a roughened area that is rougher than the surrounding surface. [Explanation of symbols]

[0099] 10 Battery case 12 Case body 12h opening 14 Sealing plate 14A Current collector terminal-sealing plate assembly 14e 1st groove 14r Roughened area 14s Thin section 18 Terminal mounting hole 20 Electrode body 30 Current collector terminal 31 Sealing plate outer side 32 Sealing plate inner side 33 Shaft 35 External conductive members 40 Insulating material 50 current collector 100 Secondary battery 120 Molding mold 200 Secondary battery 214 Sealing plate 214f Second groove 214r Roughened area 214s Thin section 218 Terminal mounting hole 230 Current collector terminal 240 Insulating materials 250 current collector 300 Secondary battery 314 Sealing plate 314e 1st groove 314f 2nd groove part 314r roughened area 314s thin section 318 Terminal mounting hole 330 Current collector terminal 340 Insulating materials 400 Secondary battery 414 Sealing plate 414h Through hole 414j Non-through hole 414r Roughened area 414s Thin section 418 Terminal mounting hole 430 Current collector terminal 440 Insulating materials

Claims

1. a case body having an opening; a sealing plate having a terminal mounting hole and sealing the opening; an electrode body housed inside the case body; a current collecting terminal having one end electrically connected to the electrode body inside the case body and the other end passing through the terminal mounting hole and exposed on the outer surface side of the sealing plate; an insulating member disposed between the sealing plate and the current collecting terminal; An electricity storage device comprising: the insulating member is disposed on the periphery of the terminal mounting hole in a state where the insulating member is integrally molded with the periphery of the terminal mounting hole of the sealing plate and the current collecting terminal, At least a portion of the periphery of the terminal mounting hole in the sealing plate forms a thin-walled portion that is thinner than the surrounding area of ​​the portion, The thin portion is a groove-shaped portion recessed from its surroundings on the outer surface side of the sealing plate. a portion of the current collecting terminal on the outer surface side of the sealing plate is disposed in the recessed groove-like portion, Here, when the average thickness of the current collecting terminal on the outer surface side of the sealing plate is t 3 and the maximum groove depth of the groove-shaped portion is d 1 , the electricity storage device satisfies the formula: d 1 ≧(1 / 5)×t 3 .

2. A case body having an opening; a sealing plate having a terminal mounting hole and sealing the opening; an electrode body housed inside the case body; a current collecting terminal having one end electrically connected to the electrode body inside the case body and the other end passing through the terminal mounting hole and exposed on the outer surface side of the sealing plate; an insulating member disposed between the sealing plate and the current collecting terminal; An electricity storage device comprising: the insulating member is disposed on the periphery of the terminal mounting hole in a state where the insulating member is integrally molded with the periphery of the terminal mounting hole of the sealing plate and the current collecting terminal, At least a portion of the periphery of the terminal mounting hole in the sealing plate forms a thin-walled portion that is thinner than the surrounding area of ​​the portion, The thin-walled portion is a groove-shaped portion recessed from its surroundings on the inner surface side of the sealing plate. a portion of the current collecting terminal on the inner surface side of the sealing plate is disposed in the recessed groove-like portion, Here, when the average thickness of the current collecting terminal on the inner surface side of the sealing plate is t 4 and the maximum groove depth of the groove-shaped portion is d 2 , the electricity storage device satisfies the formula: d 2 ≧(1 / 5)×t 4 .

3. A case body having an opening; a sealing plate having a terminal mounting hole and sealing the opening; an electrode body housed inside the case body; a current collecting terminal having one end electrically connected to the electrode body inside the case body and the other end passing through the terminal mounting hole and exposed on the outer surface side of the sealing plate; an insulating member disposed between the sealing plate and the current collecting terminal; An electricity storage device comprising: the insulating member is disposed on the periphery of the terminal mounting hole in a state where the insulating member is integrally molded with the periphery of the terminal mounting hole of the sealing plate and the current collecting terminal, At least a portion of the periphery of the terminal mounting hole in the sealing plate forms a thin-walled portion that is thinner than the surrounding area of ​​the portion, The thin portion has a plurality of non-through holes on the outer surface side and / or the inner surface side of the sealing plate.

4. The surface of the thin-walled portion that comes into contact with the insulating member and / or the surface of the current collecting terminal that faces the thin-walled portion across the insulating member has a roughened area that is rougher than the surrounding surface. The electricity storage device according to any one of claims 1 to 3.

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