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 12; a sealing plate 14 having a terminal fit hole; an electrode body accommodated inside the case body 12; a collector terminal 30; and an insulating member 40 arranged between the sealing plate 14 and the collector terminal 30. In the 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. The power storage device has a substantially rectangular welded part 13 provided along a boundary between the case body 12 and the sealing plate 14. The welded part 13 has a high-strength region 13a formed in a part of a long side portion 13s and in a neighborhood of a part where the sealing plate 14, the collector terminal 30, and the insulating member 40 are molded integrally, and having a penetration depth relatively greater than that in the other welded portion.SELECTED DRAWING: Figure 6

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] According to the inventors' investigations, in an electricity storage device in which the current collector terminal-sealing plate assembly as described in Patent Document 1 is welded to the case body, the rigidity of the portion where the sealing plate, current collector terminal, and insulating member are integrally molded tends to be higher than the rigidity of other portions (portions not involved in the integral molding) due to the integral molding. In particular, the welded portion provided along the boundary between the sealing plate and the case body tends to have lower rigidity. This results in a large difference in rigidity between the welded portion and the integrally molded portion. The inventors have found that when stress is generated in the sealing plate under some circumstances, the stress is concentrated in the portion with relatively lower rigidity, and therefore fracture is more likely to occur at the welded portion near the integrally molded portion.

[0006] The present invention has been made in consideration of these points, and aims to further improve the safety of an electricity storage device in which a collector terminal-sealing plate assembly, in which the collector terminal and insulating member as described above are integrally molded with the sealing plate (specifically, the portion including the peripheral portion of the terminal mounting hole), is welded to a case body. [Means for solving the problem]

[0007] The disclosed power 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 within 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 integrally molded with the periphery of the terminal mounting hole in the sealing plate and the current collector terminal. The sealing plate is a substantially rectangular plate having a pair of opposing long sides and a pair of opposing short sides. The opening of the case body has a substantially rectangular shape corresponding to the sealing plate, and a substantially rectangular weld is formed along the boundary between the case body and the sealing plate. Here, the welded portion is a part of the long side portion, and has a high-strength region near the part where the sealing plate, the collector terminal, and the insulating member are integrally molded, which has a relatively deeper penetration depth than other welded portions.

[0008] With this configuration, the sealing plate, the current collecting terminal, and the insulating member are integrally molded, and the weld has a high-strength region near the location where the apparent rigidity is high. This makes it possible to partially improve the strength of the weld, particularly in the region where fracture is likely to occur. This makes it possible to provide a highly safe electricity storage device. [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 one embodiment. [Figure 6] FIG. 6 is a plan view of FIG. [Figure 7] FIG. 7 is a diagram showing a schematic view of the shape of the welded portion, and is a cross-sectional view taken along a cross section perpendicular to the boundary surface between the sealing plate and the case body. [Figure 8] FIG. 8 is a diagram schematically showing a molding die according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. Matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (e.g., the general configuration and manufacturing process of a battery that do not characterize the technology disclosed herein) can be understood as design matters for a person skilled in the art based on conventional technology in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Each drawing is a schematic representation, and dimensional relationships (e.g., length, width, thickness) do not necessarily reflect actual dimensional relationships. In the drawings described below, components and parts that perform the same function are designated by the same reference numerals, and redundant descriptions may be omitted or simplified. In this specification, the notation "A to B" (A and B are arbitrary numbers) indicating a range means A or greater 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] 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 is a substantially rectangular plate member having a pair of opposing long sides and a pair of opposing short sides. The sealing plate 14 is a member that seals the substantially rectangular 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 welded together. The sealing plate 14 has an inner surface 14a (see FIG. 5) that faces the inside of the secondary battery 100 (the side facing the electrode body 20) and an outer surface 14b (see FIG. 5) that faces 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 (not shown). 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 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 of sealing plate 14 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] Case body 12 may be provided with sealing plate support portions (not shown) on the inner wall surfaces of a pair of short sides of the periphery of opening 12h. The sealing plate support portions are formed to protrude inward of case body 12. As a result, sealing plate 14 fitted into opening 12h rests on the sealing plate support portions and does not sink too deeply into opening 12h. Therefore, outer surface 14b of sealing plate 14 is positioned so as to be substantially flush with the upper surface of the periphery of adjacent opening 12h. Note that sealing plate support portions may be provided on the short sides of the periphery of opening 12h, or may be provided at the four corners.

[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] 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. 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.

[0033] 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. Furthermore, the sealing plate inner surface side 32 of the current collecting terminal 30 is arranged on the inner surface of the sealing plate 14. As shown in FIG. 5, the sealing plate outer surface side 31 of the current collecting terminal 30 is configured to be large enough to be inserted through the terminal mounting hole 18. On the other hand, the sealing plate inner surface side 32 of the current collecting terminal 30 is configured to have a larger outer diameter than the terminal mounting hole 18. This makes it possible to suitably perform the integrated molding (insert molding) described below. Furthermore, the outer diameter of the sealing plate inner surface side 32 is larger than the outer diameter of the sealing plate outer surface side 31. There are no particular limitations on the shapes of the sealing plate outer surface side 31 and the sealing plate inner surface side 32 of the current collecting terminal 30 in a plan view. The shape of the sealing plate outer surface 31 and the sealing plate inner surface 32 in plan view may be a polygonal shape such as a triangle, a rectangle, or a hexagon, or may be a perfect circle or an ellipse.

[0034] 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 multiple positive electrode tabs 22t to the positive electrode side current collecting terminal 30. The negative electrode side current collector 50 connects a negative electrode tab group 25 consisting of multiple negative electrode tabs 24t to the negative electrode side current collecting terminal 30. As shown in FIG. 2 , the current collector 50 has, for example, a first current collecting portion 51 extending along the long side direction Y and a second current collecting portion 52 extending along the short side wall 12c of the case body 12. The current collector 50 can be made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The current collector 50 and the current collecting terminal 30 are joined by welding, for example, ultrasonic welding, resistance welding, or laser welding. Alternatively, the current collector 50 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 current collector 50 and the current collecting terminal 30 may also be joined by mechanical processing such as riveting.

[0035] The first current collecting portion 51 is disposed between the sealing plate 14 and the electrode body 20. The first current collecting portion 51 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 current collecting portion 51. The first current collecting portion 51 is insulated from the sealing plate 14 by the insulating member 40. The first current collecting portion 51 is connected to the inner surface 32 of the sealing plate of the current collecting terminal 30. As shown in FIG. 2, one side of the second current collecting portion 52 in the vertical direction Z (the upper side in FIG. 2) is connected to the first current collecting portion 51, and the other side (the lower side in FIG. 2) is connected to the positive electrode tab group 23 or the negative electrode tab group 25.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Fig. 6 is a plan view of Fig. 1. Fig. 7 is a diagram schematically showing the shape of the welded portion, and is a cross-sectional view of a section perpendicular to the boundary surface 85 between the sealing plate 14 and the case body 12. As shown in Fig. 6, the outer edge of the sealing plate 14 and the periphery of the opening 12h of the case body 12 are welded together, and a welded portion 13 is formed along the boundary (fitting portion) between the case body 12 and the sealing plate 14. As a result, the opening 12h of the case body 12 is tightly sealed by the sealing plate 14, and the battery case 10 can be sealed.

[0041] The welded portion 13 can be formed by welding, for example, laser welding. The welded portion 13 is formed by laser welding the mating portion between the case body 12 and the sealing plate 14, thereby melting the constituent metals of the case body 12 and the sealing plate 14. The welded portion 13 is located on the outer surface side of the sealing plate 14. The welded portion 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 welded portion 13 is formed around the entire periphery of the mating portion between the sealing plate 14 and the case body 12. In a plan view, the welded portion 13 is formed continuously in a substantially rectangular shape along the mating portion between the sealing plate 14 and the case body 12, and has a pair of opposing long sides 13s and a pair of opposing short sides 13t.

[0042] As shown in FIG. 6 , the welded portion 13 of the electricity storage device disclosed herein is a part of the long side 13s, and has a high-strength region 13a near the portion where the sealing plate 14, the current collecting terminal 30, and the insulating member 40 are integrally molded. The high-strength region 13a has a relatively deeper penetration depth than the other welded portions. The high-strength region 13a has a greater strength due to its deeper penetration depth (greater welding depth) than the other welded portions. The electricity storage device disclosed herein includes a current collecting terminal-sealing plate assembly 14A in which the sealing plate 14, the current collecting terminal 30, and the insulating member 40 are integrally molded. The current collecting terminal-sealing plate assembly 14A firmly joins each component so that the joint strength meets a predetermined standard. Therefore, the portion of the sealing plate 14 that is integrally molded with the current collecting terminal 30 and the insulating member 40 has a sharp increase in apparent rigidity. On the other hand, the welded portion 13 that is not involved in the integral molding has a relatively low rigidity. When such a difference in rigidity occurs in an electricity storage device, stress concentrates in the low-rigidity portion at the boundary between the high-rigidity portion (i.e., the integrally molded portion) and the low-rigidity portion (i.e., the welded portion 13), making the device particularly susceptible to fracture. Therefore, by providing the high-strength region 13a in the welded portion 13 near the portion where the sealing plate 14, the current collecting terminal 30, and the insulating member 40 are integrally molded, the strength of the region prone to fracture can be partially increased. This effectively increases the fracture strength of the electricity storage device, making it possible to provide a safer electricity storage device.

[0043] The high-strength region 13a of the welded portion 13 is a region provided in a portion of the welded portion 13 where stress concentration due to the above-described difference in rigidity is likely to occur. The high-strength region 13a has a higher strength than other welded portions. Specifically, the high-strength region 13a has a relatively deeper penetration depth than regions of the welded portion 13 other than the high-strength region 13a. For example, the high-strength region 13a is a region formed to have a deeper penetration depth than the average penetration depth of the entire periphery of the welded portion 13. Furthermore, the high-strength region 13a may be a region formed to have a deeper penetration depth than the short side portion 13t of the welded portion 13. This can partially improve the strength of the portion of the welded portion 13 where stress concentration is likely to occur, effectively preventing the secondary battery 100 from breaking.

[0044] The penetration depth (welding depth) refers to the length in the direction along the boundary surface 85 between the sealing plate 14 and the case body 12 (the length along the vertical direction Z in FIG. 7). The penetration depth can be measured, for example, by observing the cross section of the welded portion with a microscope or the like. The penetration depth can be adjusted by changing the welding conditions. For example, when welding the high-strength region 13a, the penetration depth can be increased by increasing the irradiation output of the laser light or by lengthening the irradiation time compared to other welded portions. Alternatively, the penetration depth can be increased by adjusting the depth and width of the groove portion 80, which will be described later.

[0045] Although not particularly limited, the ratio (D1 / D2) of the penetration depth D1 of the high strength region 13a to the penetration depth D2 of the welded portion other than the high strength region 13a is preferably 1.1 or greater. This appropriately improves the strength of the high strength region 13a and prevents fracture in the vicinity of the portion where the sealing plate 14, the current collecting terminal 30, and the insulating member 40 are integrally molded. The ratio (D1 / D2) of the penetration depth D1 of the high strength region 13a to the penetration depth D2 of the welded portion other than the high strength region 13a is preferably 1.2 or greater, and more preferably 1.3 or greater. Furthermore, although not particularly limited, the ratio (D1 / D2) of the penetration depth D1 of the high strength region 13a to the penetration depth D2 of the welded portion other than the high strength region 13a is preferably 1.5 or less. For example, the ratio (D1 / D3) of the penetration depth D of the high strength region 13a to the penetration depth D3 of the short side of the weld is preferably 1.1 to 1.5.

[0046] Although not particularly limited, the high-strength region 13a may be provided in only one of the vicinity of the portion where the positive electrode side current collector terminal 30, sealing plate 14, and insulating member 40 are integrally molded with the sealing plate 14 and the vicinity of the portion where the negative electrode side current collector terminal 30, sealing plate 14, and insulating member 40 are integrally molded with the sealing plate 14. Preferably, the high-strength region 13a is provided both in the vicinity of the portion where the positive electrode side current collector terminal 30, sealing plate 14, and insulating member 40 are integrally molded with the sealing plate 14 and the vicinity of the portion where the negative electrode side current collector terminal 30, sealing plate 14, and insulating member 40 are integrally molded with the sealing plate 14.

[0047] The high-strength region 13a in the welded portion 13 is provided on a portion of the long side 13s of the welded portion 13, which is formed in a substantially rectangular shape. The high-strength region 13a in the welded portion 13 is preferably located near the end of the long side direction Y of the sealing plate inner surface 32 of the current collector terminal 30. The area near the end of the long side direction Y of the sealing plate inner surface 32 is where the integrally molded portion transitions to the area not involved in the integral molding. For this reason, stress concentration is likely to occur in the area near the end of the long side direction Y of the sealing plate inner surface 32, making the welded portion 13 more likely to break. By providing the high-strength region 13a, which has a partially high strength, in the area near the end of the sealing plate inner surface 32, the fracture strength can be more suitably improved.

[0048] As described above, the high-strength regions 13a are preferably located on the long sides 13s of the welded portion 13 near both ends in the long side direction Y of the sealing plate inner surface 32. More specifically, on the long sides 13s of the welded portion 13, a region that is 0.8 times the length of the sealing plate inner surface 32 of the current collecting terminal 30 in the long side direction Y is defined as region A, a region that extends from the central end of region A in the long side direction Y toward the center of the sealing plate 14 and is 0.2 times the length of region A is defined as region B, and a region that extends from the outer edge end of region A in the long side direction Y toward the outer edge of the sealing plate 14 and is 0.2 times the length of region A in the long side direction Y is defined as region C. The high-strength regions 13a are preferably located in region B and / or region C.

[0049] The high-strength region 13a may be disposed only in region B or only in region C. Preferably, the high-strength region 13a is disposed in both region B and region C. Although not particularly limited, when the high-strength region 13a is disposed in either region B or region C from the viewpoint of production costs, etc., the high-strength region 13a is preferably disposed in region B (i.e., the long side portion 13s of the welded portion 13, near the end portion on the central side in the long side direction Y of the sealing plate inner surface side 32). When the pressure inside the case increases due to some factor, stress concentration is more likely to occur at the central side than at the outer edge side in the long side direction Y of the sealing plate 14. Therefore, by disposing the high-strength region 13a in the above-described region B, the breaking strength can be more suitably improved.

[0050] Although not particularly limited, the length L2 of the high-strength region 13a along the long-side direction Y is preferably 5% or more when the length L1 of the long side portion 13s of the welded portion 13 is taken as 100%. If the length L2 of the high-strength region 13a is shorter than 5% of the length L1 of the long side portion 13s of the welded portion 13, sufficient strength cannot be ensured when stress is concentrated, which is undesirable because there is a risk of fracture. Increasing the penetration depth of the entire welded portion (increasing the laser output) to ensure strength can increase the probability of welding defects such as spatter, voids, and burns. Furthermore, preparing such a high-power laser is necessary, which is undesirable from the standpoint of production costs. Although not particularly limited, from the standpoint of reducing the occurrence of welding defects and reducing production costs, the length L2 of the high-strength region 13a is preferably 15% or less when the length L1 of the long side portion 13s of the welded portion 13 is taken as 100%. The length L2 of the high-strength region 13a along the long side direction Y is preferably, for example, 5% or more and 15% or less, and more preferably 5% or more and 10% or less, when the length L1 of the long side portion 13s of the welded portion 13 is 100%.

[0051] As shown in Figures 6 and 7, sealing plate 14 preferably has a groove 80 that is located radially inward of weld 13. Groove 80 is continuously formed so as to have a generally rectangular shape that is smaller than weld 13 in a plan view. The heat of the laser beam irradiated when welding case body 12 and sealing plate 14 tends to escape from the desired position (here, the boundary between case body 12 and sealing plate 14) to other locations, making it difficult for the energy to remain at the boundary. By providing groove 80 radially inward of weld 13 on sealing plate 14, it is possible to more easily retain the energy of the laser beam at the desired position when welding.

[0052] The deeper the groove depth of the groove portion 80 (the length along the thickness direction of the sealing plate 14; the length in the vertical direction Z in FIG. 7), the more effective it is at retaining the energy of the laser light as described above. Therefore, it is preferable that the groove depth near the high strength region is deeper than other parts. This allows the penetration depth of the high strength region 13a to be suitably deep. Although not particularly limited, the ratio (H1 / H2) of the groove depth H1 of the groove portion 80 near the high strength region to the groove depth H2 of the groove portion 80 near the short side portion of the weld is preferably 1.05 to 1.2.

[0053] 5 and 7, 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.

[0054] The roughened area 14r may be provided on the sealing plate 14. Preferably, the roughened area 14r is provided on at least a portion of the surface that contacts the insulating member 40. Alternatively, the roughened area 14r may be provided on the current collecting terminal 30. Preferably, the roughened area 14r is provided on the surface where the current collecting terminal 30 and the insulating member 40 contact each other. The roughened area 14r may be provided on the sealing plate outer surface 31 of the current collecting terminal 30, on the sealing plate inner surface 32, or on both. As described above, the anchor effect is exerted in the areas where the roughened area 14r is provided, and the rigidity tends to be particularly high. That is, the rigidity is particularly high in areas where the roughened area 14r is provided on the sealing plate 14 and / or the current collecting terminal 30 and is integrally molded with the insulating member 40.

[0055] Although not particularly limited, the high-strength region 13a of the weld 13 is preferably located in the area where the sealing plate 14, the current collecting terminal 30, and the insulating member 40 are integrally molded, near the location where the roughened area 14r is provided on the sealing plate 14 and / or the current collecting terminal 30. Stress tends to concentrate locally at the transition between the roughened and non-roughened areas, making such transitions prone to fracture. Therefore, by providing the high-strength region 13a, which has a locally high strength, at such transitions, the fracture strength can be suitably improved.

[0056] <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.

[0057] The secondary battery 100 as 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 welding the integrally molded current collecting terminal-sealing plate assembly 14A to the case body 12. Note that other steps may also be included at any stage.

[0058] In the preparation step, a sealing plate 14, a current collecting terminal 30, and an electrode assembly 20 are prepared. The electrode assembly 20 can be produced 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 laminated so that they are insulated by two strip-shaped separators 26. At this time, 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 pressing device commonly used in the manufacture of flat wound electrode assembly, and is not particularly limited. In this manner, the electrode body 20 can be prepared.

[0059] FIG. 8 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. 8, by a method including a part setting process, a positioning process, an upper die setting process, an injection molding process, an upper die release process, and a part removal process.

[0060] 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 outer surface 31 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 outer surface 31. 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] In the welding process, the secondary battery 100 is sealed by welding the current collector terminal-sealing plate assembly 14A to the case body 12 with the prepared electrode body 20 housed inside the case body 12. 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).

[0066] Next, with the electrode body 20 housed inside the case body 12, the current collector terminal-sealing plate assembly 14A and the periphery of the opening 12h of the case body 12 are joined by laser welding. The upper edge of the periphery of the opening of the case body 12 and the outer surface 14b of the sealing plate 14 are fitted together so that they are flush with each other. Then, a laser beam is irradiated from the outer surface of the battery case 10 toward the boundary (fitting portion) between the case body 12 and the sealing plate 14. The type of laser beam used for laser welding and the laser welding conditions are not particularly limited and may be the same as those used in the past. The angle between the laser irradiation direction and the outer surface 14b (horizontal plane) of the sealing plate 14 is, for example, approximately 90±10°, or may be approximately 90±5°. During laser welding, the irradiation power is increased near the portion where the sealing plate 14, current collector terminal 30, and insulating member 40 are integrally molded, so that the penetration depth is deeper than in other welded portions. This makes it possible to suitably form high-strength region 13a in the vicinity of the portion where sealing plate 14, current collecting terminal 30, and insulating member 40 are integrally molded. By welding the boundary (fitting portion) between case body 12 and sealing plate 14 around the entire periphery, case body 12 and sealing plate 14 are sealed without any gaps.

[0067] After the welding step, the electrolyte is poured through the liquid pouring hole 15, and the liquid pouring hole 15 is closed with a sealing member 16, thereby sealing the secondary battery 100. In this manner, the secondary battery 100 can be manufactured.

[0068] <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).

[0069] 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.

[0070] 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 assembly housed inside the case body; a current collecting 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 collecting terminal, wherein the insulating member is disposed around the periphery of the terminal mounting hole in a state where it is integrally molded with the periphery of the terminal mounting hole in the sealing plate and the current collecting terminal. the sealing plate is a substantially rectangular plate having a pair of long sides facing each other and a pair of short sides facing each other, the opening of the case body has a substantially rectangular shape corresponding to the sealing plate, and has a substantially rectangular weld along the boundary between the case body and the sealing plate, wherein the weld is part of the long sides and has a high-strength region near a portion where the sealing plate, the current collecting terminal, and the insulating member are integrally molded, the high-strength region having a penetration depth relatively deeper than other welded regions. Item 2: The electricity storage device according to item 1, wherein a ratio (D1 / D2) of a penetration depth D1 of the high strength region of the welded portion to a penetration depth D2 of a welded portion other than the high strength region of the welded portion is 1.1 to 1.5. Item 3: The electricity storage device according to item 1 or 2, wherein the high-strength region is located on the long side of the welded portion near the end of the current collector terminal in the long side direction on the inner surface of the sealing plate. Item 4: The electricity storage device according to any one of items 1 to 3, wherein the length of the high-strength region along the long side direction is 5% to 15% when the length of the long side portion of the weld is taken as 100%. Item 5: The electricity storage device according to any one of Items 1 to 4, wherein the sealing plate has a groove portion radially inward of the welded portion, and a ratio (H1 / H2) of a groove depth H1 of the groove portion near the high strength region to a groove depth H2 of the groove portion near the short side of the welded portion is 1.05 to 1.2. [Explanation of symbols]

[0071] 10 Battery case 12 Case body 12a Bottom 12b Long side wall 12c short side wall 12h opening 13 Welded parts 13a High intensity area 13s Long side 13t short side 14 Sealing plate 14A Current collector terminal-sealing plate assembly 14r Roughened area 18 Terminal mounting hole 18a Periphery 20 Electrode body 22 Positive electrode sheet 24 Negative electrode sheet 26 Separator 30 Current collector terminal 31 Sealing plate outer side 32 Sealing plate inner side 33 Shaft 40 Insulating material 40h through hole 41 First flange 42 Second flange 43 Cylindrical part 44 Protrusion 50 current collector 80 Groove 85 Boundary 100 Secondary battery 120 Molding mold

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, the sealing plate is a substantially rectangular plate having a pair of long sides facing each other and a pair of short sides facing each other, the opening of the case body has a substantially rectangular shape corresponding to the sealing plate, a substantially rectangular welded portion is provided along the boundary between the case body and the sealing plate, Here, the welded portion is a part of a long side portion, and has a high-strength region in the vicinity of a portion where the sealing plate, the current collecting terminal, and the insulating member are integrally molded, the high-strength region having a penetration depth relatively deeper than other welded portions, the sealing plate has a groove portion located radially inward of the welded portion, a ratio (H1 / H2) of a groove depth H1 of the groove portion near the high strength region to a groove depth H2 of the groove portion near the short side portion of the weld is 1.05 to 1.

2.

2. The storage device according to claim 1, wherein a ratio (D1 / D2) of a penetration depth D1 of the high strength region of the weld to a penetration depth D2 of a weld portion other than the high strength region of the weld is 1.1 to 1.

5.

3. The electricity storage device according to claim 1 , wherein the high-strength region is located on the long side of the welded portion, near an end of the current collector terminal in the long side direction on an inner surface side of the sealing plate.

4. 3 . The electricity storage device according to claim 1 , wherein a length of the high-strength region along a long side direction is 5% to 15% when a length of a long side portion of the weld is taken as 100%.

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