Energy storage devices

Abstract

To provide a stable power storage device.SOLUTION: The power storage device disclosed herein includes: a case body 12; a sealing plate 14 having a terminal attachment hole; an electrode body stored in the case body 12; a power collecting terminal; and an insulating member 40 arranged between the sealing plate 14 and the power collecting terminal. In the power storage device, the insulating member 40 is arranged in a peripheral edge 18a of the terminal attachment hole 18 while the insulating member is being integrated with the edge part of the terminal attachment hole 18 of the sealing plate 14 and the power collecting terminal. The power collecting terminal of the sealing plate 14 is formed of a metal material of which 0.2% proof stress and the breaking elongation satisfy a predetermined range.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] In an electricity storage device in which the current collector terminal-sealing plate assembly and the case body are welded as described in Patent Document 1, 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, because the sealing plate and current collector terminal are each made of strong materials that satisfy a predetermined strength, it is thought that the rigidity of such integrally molded portions tends to be higher. According to studies by the present inventors, when stress is generated in the sealing plate under some circumstances, the stress is concentrated in portions with relatively low rigidity, and therefore, portions not involved in the integral molding (for example, the welded portion provided along the boundary between the sealing plate and the case body) are prone to fracture.

[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 electricity storage device disclosed herein is an electricity storage device comprising: a case body having an opening; a metal 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. The insulating member is disposed on the periphery of the terminal mounting hole in the sealing plate, integrally molded with the peripheral portion of the terminal mounting hole and the current collecting terminal. The sealing plate has a 0.2% proof stress A of 95 to 350 N / mm 2 and is made of a metal material having a breaking elongation X of 4 to 27%, and the current collecting terminal has a 0.2% yield strength B of 25 to 200 N / mm 2 and is made of a metal material having a breaking elongation Y of 20 to 45%. Here, the power storage device has a ratio (B / A) of the proof strength B to the proof strength A of 0.08 to 0.8, and a ratio (Y / X) of the breaking elongation Y to the breaking elongation X of 1.1 to 10.8.

[0008] This configuration makes it possible to suitably reduce the rigidity of the portion where the sealing plate, the current collecting terminal, and the insulating member are integrally molded, thereby reducing the difference in rigidity between the integrally molded portion and portions not involved in the integral molding (e.g., welded portions), thereby preventing stress concentration and realizing a highly safe electricity storage device.

[0009] In this specification, the term "0.2% yield strength (N / mm 2 Unless otherwise specified, "0.2% yield strength" and "breaking elongation (%)" refer to values ​​determined in accordance with JIS Z 2241 using a JIS No. 13 B test piece. Also, 0.2% yield strength is sometimes simply referred to as "yield strength." [Brief explanation of the drawings]

[0010] [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 diagram schematically showing a molding die according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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 houses the electrode body 20 and the electrolyte, a sealing plate 14, a positive electrode terminal 30, a negative electrode terminal 35, and an insulating member 40.

[0015] 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.

[0016] 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.

[0017] 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 terminal 30 via the positive electrode current collector 50.

[0018] 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).

[0019] 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.

[0020] 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.

[0021] 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 terminal 35 via the negative electrode current collector 60.

[0022] 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, and carbon materials such as graphite, hard carbon, and soft carbon can be used. Graphite may be natural graphite or artificial graphite, or amorphous carbon-coated graphite, in which graphite is coated with an amorphous carbon material. Materials other than carbon-based materials may also be used as the negative electrode active material. Examples of such materials other than carbon-based materials include lithium titanate (LTO) and silicon-based materials (SiO). The negative electrode active material layer 24a may 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).

[0023] 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.

[0024] 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.

[0025] 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) outer shape with a bottom. The case body 12 is a housing that houses the electrode assembly 20 and the electrolyte. The case body 12 is a square container with a bottom and an opening 12h (see FIG. 2) on one side (here, the top surface). Here, the opening 12h is approximately rectangular. As shown in FIG. 1, the case body 12 has long and short sides and includes a bottom surface 12a that is approximately 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 wall 12c is smaller than the area of ​​the long side wall 12b. Although 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 is preferably 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 seals the substantially rectangular opening 12h of the case body 12. The outer edge of the sealing plate 14 is welded to the peripheral edge of the opening 12h of the case body 12. As shown in FIG. 2, the sealing plate 14 has two terminal mounting holes 18, 19 that penetrate the sealing plate 14 in the thickness direction. The terminal mounting holes 18, 19 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 a positive electrode terminal 30, and the terminal mounting hole 19 on the other side (the right side in FIG. 2) is for a negative electrode terminal 35. The terminal mounting holes 18, 19 are substantially circular in plan view. However, the terminal mounting holes 18, 19 may have an elliptical shape or a polygonal shape such as a square shape or a hexagonal shape in a plan view. The shapes of the terminal mounting holes 18, 19 may be selected appropriately according to the shapes of the positive electrode terminal 30 and the negative electrode terminal 35.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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, and the insulating member 40 are integrally molded. As shown in Fig. 4, 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, and the insulating member 40 are integrally molded. Note that in Fig. 4, in addition to the sealing plate 14, the current collector terminal, and the insulating member 40, the positive electrode current collector 50 and the negative electrode current collector 60 are also integrally molded.

[0031] As shown in FIG. 2, the positive electrode terminal 30 is disposed so that one end is exposed on the outer surface side of the sealing plate 14, and the other end is connected to the positive electrode 22 of the electrode assembly 20 inside the case body 12. The positive electrode terminal 30 is connected to a positive electrode tab group 23 consisting of multiple positive electrode tabs 22t via a positive electrode current collector 50 inside the battery case 10. As shown in FIG. 2, the positive electrode 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 negative electrode terminal 35 is disposed so that one end is exposed on the outer surface side of the sealing plate 14, and the other end is connected to the negative electrode 24 of the electrode assembly 20 inside the case body 12. The negative electrode terminal 35 is connected to a negative electrode tab group 25 consisting of multiple negative electrode tabs 24t via a negative electrode current collector 60 inside the battery case 10. As shown in FIG. 2, the negative electrode current collector 60 has, for example, a first current collecting portion 61 extending along the long side direction Y and a second current collecting portion 62 extending along the short side wall 12c of the case body 12.

[0032] The positive electrode current collector 50 and the positive electrode terminal 30, and the negative electrode current collector 60 and the negative electrode terminal 35 are joined by welding, for example, ultrasonic welding, resistance welding, laser welding, or the like. Alternatively, the positive electrode current collector 50 and the negative electrode current collector 60 may be joined by being integrally molded with the sealing plate 14 together with the positive electrode terminal 30 and the negative electrode terminal 35 in an integral molding process described below. Furthermore, the positive electrode current collector 50 and the positive electrode terminal 30, and the negative electrode current collector 60 and the negative electrode terminal 35 may be joined by mechanical processing, such as riveting.

[0033] FIG. 5 is a schematic cross-sectional view of the vicinity of the positive electrode terminal. As shown in FIG. 5, the first current collecting portion 51 of the positive electrode current collector 50 is disposed between the sealing plate 14 and the electrode assembly 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 end of the positive electrode terminal 30 on the inner surface side. As shown in FIG. 2, one side of the second current collecting portion 52 of the positive electrode current collector 50 in the vertical direction Z (the upper side in FIG. 2) is connected to the first current collecting portion 51 of the positive electrode current collector 50, and the other side (the lower side in FIG. 2) is connected to the positive electrode tab group 23. Note that, although the structure of the positive electrode side has been described above, the negative electrode side may have a similar structure.

[0034] The insulating member 40 is a member that prevents conduction between the sealing plate 14 and the current collecting terminals (positive electrode terminal 30 and negative electrode terminal 35). As shown in FIG. 5, the insulating member 40 is disposed on the peripheral edge 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 positive electrode 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.

[0035] 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.

[0036] 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 side of the sealing plate 14 and insulates the end of the positive terminal 30 disposed on the outer side of the case body 12 (hereinafter also referred to as the “sealing plate outer surface side 31”) from the outer surface 14b of the sealing plate 14. As shown in FIG. 4 , the first flange portion 41 protrudes outward beyond the positive terminal 30 and the negative terminal 35 in a plan view and is exposed to the outside. 5, the second flange portion 42 is disposed on the inner surface side of the sealing plate 14, and insulates the end of the positive terminal 30 that is disposed inside the case body 12 (hereinafter also referred to as the "sealing plate inner surface side 32") 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 positive terminal 30.

[0037] The cylindrical portion 43 is located between the terminal mounting hole 18 and the shaft portion 33 of the positive 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 during use of the secondary battery 100.

[0038] As shown in FIG. 4 , the electricity storage device disclosed herein includes a current collector terminal-sealing plate assembly 14A in which a sealing plate 14, current collector terminals (positive electrode terminal 30 and negative electrode terminal 35), and insulating member 40 are integrally molded. In such current collector terminal-sealing plate assemblies, each component is typically designed to have a predetermined bonding strength, and the current collector terminal and sealing plate are firmly bonded together. For this reason, the portion where the sealing plate, current collector terminal, and insulating member are integrally molded tends to have a sharp increase in apparent rigidity. Meanwhile, portions not involved in the integral molding (e.g., welded portions) have relatively low rigidity. When such a difference in rigidity occurs in an electricity storage device, if some stress is generated inside the case, stress is concentrated 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), making the device particularly susceptible to fracture. Therefore, in the electricity storage device disclosed herein, the sealing plate 14, current collecting terminal, and insulating member 40 are integrally molded, and the sealing plate 14 and current collecting terminal are made of materials whose 0.2% proof stress and breaking elongation satisfy a predetermined relationship. This ensures a certain level of strength for the current collecting terminal-sealing plate assembly 14A, while preventing a sudden increase in the apparent rigidity of the portion where the sealing plate 14, current collecting terminal, and insulating member 40 are integrally molded. This reduces stress concentration in the portion with low rigidity, and makes it possible to suitably improve the breaking strength of the electricity storage device.

[0039] In metal materials, there is generally a trade-off between yield strength and breaking elongation. In the electricity storage device disclosed herein, the sealing plate 14 is made of a material with a high 0.2% yield strength and low breaking elongation, and the current collecting terminals are made of a material with a relatively low 0.2% yield strength and high breaking elongation. In other words, the sealing plate 14 is made of a material that is hard and difficult to deform, while the current collecting terminals are made of a material that is soft and easy to deform. Specifically, the sealing plate 14 has a yield strength A of 95 N / mm 2 ~350N / mm 2 The current collector terminal is made of a material with a breaking elongation X of 4% to 27%. The yield strength B is 25N / mm 2 ~200N / mm 2and is made of a material having a breaking elongation Y of 20% to 45%. The ratio of the yield strength B to the yield strength A (B / A) is 0.08 to 0.8, and the ratio of the breaking elongation Y to the breaking elongation X (Y / X) is 1.1 to 10.8. This ensures that the current collecting terminal-sealing plate assembly 14A has a predetermined strength, while preventing a sudden increase in rigidity.

[0040] The sealing plate 14 is not particularly limited as long as it is made of a metal material whose 0.2% yield strength and breaking elongation satisfy the above-mentioned ranges. The sealing plate 14 is a component that ensures a predetermined strength of the current collector terminal-sealing plate assembly 14A. The sealing plate 14 may be made of, for example, aluminum, an aluminum alloy, stainless steel, iron, an iron alloy, or the like. More specifically, the sealing plate 14 is preferably made of ferritic stainless steel, an Al-Mn alloy (e.g., A3003), or an Al-Fe alloy. The above-mentioned yield strength and breaking elongation change depending on the tempering (processing or heat treatment) even if the constituent elements are the same. Specifically, for example, the sealing plate 14 is preferably made of an H-type material (e.g., A3003-H18 material), an Al-Mn alloy that has been work-hardened.

[0041] The yield strength A of the metal material constituting the sealing plate 14 is set to 95 N / mm 2 or more, and 125N / mm 2 It may be more than 145N / mm 2 On the other hand, if the yield strength is too high, the breaking elongation becomes too low, making it difficult for the sealing plate 14 to deform, and the rigidity of the integrally molded portion becomes excessively high. From this perspective, the upper limit of the yield strength A is set to 350 N / mm 2 Less than or equal to 275N / mm 2 Preferably, it is less than 200N / mm 2 It is more preferable that it is less than 185N / mm 2In the electricity storage device disclosed herein, sealing plate 14 is integrally molded with the current collecting terminal and insulating member 40, and is therefore made of a material whose yield strength satisfies the above-mentioned range, thereby ensuring sufficient strength for current collecting terminal-sealing plate assembly 14A.

[0042] The breaking elongation X of the metal material that makes up the sealing plate 14 is at least 4% or more from the viewpoint of reducing the rigidity of the integrally molded portion. A higher breaking elongation X is preferable from the viewpoint of reducing rigidity, but from the viewpoint of ensuring sufficient strength of the current collector terminal-sealing plate assembly 14A, it is 27% or less. The breaking elongation X of the sealing plate 14 is 4% to 27%, and preferably, for example, 4% to 22%, and may be 4% to 10%.

[0043] The current collector terminal is not particularly limited as long as it is made of a metal material whose yield strength and breaking elongation satisfy the above-mentioned ranges. The current collector terminal may be made of, for example, aluminum, an aluminum alloy, copper, or a copper alloy. More specifically, the positive electrode terminal 30 is preferably made of pure aluminum. The negative electrode terminal 35 is preferably made of pure copper, such as tough pitch copper or oxygen-free copper, or pure aluminum. As described above, the yield strength and breaking elongation vary depending on the tempering, even if the constituent elements are the same. Specifically, for example, the positive electrode terminal 30 is preferably made of pure aluminum and an annealed O material (e.g., A1050-O material). The negative electrode terminal 35 is preferably made of pure aluminum or tough pitch copper and an annealed O material (e.g., A1050-O material or C1100-O material). In this specification, "pure aluminum" refers to aluminum whose constituent elements are 99% or more Al.

[0044] If the yield strength B of the material constituting the current collecting terminal is too low, the current collecting terminal will not be able to secure the required strength, which is undesirable. From this point of view, the yield strength B should be at least 25 N / mm 2 or more, and 30N / mm 2It is preferable that the yield strength B is 200 N / mm or more. On the other hand, if the yield strength B is too high, the breaking elongation tends to be small, and the rigidity of the portion where the sealing plate 14 and the insulating member 40 are integrally molded increases sharply. This is undesirable because it increases the difference in rigidity between the integrally molded portion and the non-integrally molded portion. From this perspective, it is preferable that the yield strength B is 200 N / mm or more. 2 Less than 150N / mm 2 Preferably, it is less than 100N / mm 2 It is more preferable that it is less than 70N / mm 2 As long as the above-mentioned range is satisfied, the positive electrode terminal 30 and the negative electrode terminal 35 may be made of materials having the same proof strength B or materials having different proof strengths B.

[0045] The high breaking elongation Y of the metal material constituting the current collecting terminals makes the current collecting terminals relatively deformable. This allows for a favorable reduction in the rigidity of the portion where the current collecting terminals, sealing plate 14, and insulating member 40 are integrally molded. From this perspective, the breaking elongation Y is 20% or more, preferably 28% or more, and more preferably 35% or more. From the perspective of reducing the rigidity of the integrally molded portion, a higher breaking elongation Y is preferable, but from the perspective of ensuring a certain level of strength of the current collecting terminals, it is 45% or less. The breaking elongation Y is preferably 43% or less, and may be 40% or less. Note that, as long as the above-mentioned range is satisfied, the positive electrode terminal 30 and the negative electrode terminal 35 may be made of materials with the same breaking elongation Y or materials with different breaking elongations Y.

[0046] In the electricity storage device disclosed herein, the aforementioned yield strength A and yield strength B are adjusted to satisfy a predetermined relationship, thereby preventing the apparent rigidity of the integrally molded portion from becoming excessively high. From this perspective, the ratio of yield strength B to yield strength A (B / A) is 0.8 or less, preferably 0.66 or less, and more preferably 0.38 or less. On the other hand, if the ratio of yield strength B to yield strength A is too small, it is undesirable because it may cause a rigidity difference between the sealing plate 14 and the current collecting terminal. From this perspective, the ratio of yield strength B to yield strength A (B / A) is 0.08 or more, may be 0.1 or more, and is preferably 0.24 or more. Note that when the positive electrode terminal 30 and the negative electrode terminal 35 are made of different materials with different yield strengths B, it is sufficient that the relationship between the yield strength A and the yield strength B of the material constituting the positive electrode terminal 30 and the relationship between the yield strength A and the yield strength B of the material constituting the negative electrode terminal 35 are adjusted to satisfy the above-mentioned ranges.

[0047] Furthermore, in the electricity storage device disclosed herein, the breaking elongation X and breaking elongation Y are adjusted to satisfy a predetermined relationship, thereby suitably reducing the apparent rigidity of the integrally molded portion. From this perspective, the ratio of breaking elongation Y to breaking elongation X (Y / X) is 1.1 or greater, preferably 1.29 or greater, and more preferably 1.59 or greater. If the ratio of breaking elongation Y to breaking elongation X is too large, this is undesirable because it may cause a difference in rigidity between the sealing plate 14 and the current collecting terminal. From this perspective, the ratio of breaking elongation Y to breaking elongation X (Y / X) is 10.8 or less, and may be 8.8 or less, 7 or less, or 4.3 or less. In addition, when the positive electrode terminal 30 and the negative electrode terminal 35 are made of materials with different breaking elongation Y, the relationship between the breaking elongation X and the breaking elongation Y of the material making up the positive electrode terminal 30, and the relationship between the breaking elongation X and the breaking elongation Y of the material making up the negative electrode terminal 35, may be adjusted so as to satisfy the above-mentioned ranges.

[0048] As a combination of materials in which the above-mentioned yield strength A and yield strength B, and the breaking elongation X and breaking elongation Y satisfy the predetermined relationship, for example, the sealing plate 14 is made of ferritic stainless steel (yield strength A: 275 N / mm 2 ~350N / mm 2 , breaking elongation: 27% to 30%), and the positive terminal 30 is made of pure aluminum (yield strength B: 30 N / mm 2 ~35N / mm 2 , breaking elongation Y: 35% to 43%), and the negative terminal 35 is made of tough pitch copper (yield strength B: 195 N / mm 2 The sealing plate 14 is preferably made of an Al-Mn alloy (proof strength A: 125 N / mm 2 ~185N / mm 2 The positive electrode terminal 30 and the negative electrode terminal 35 are preferably made of the above-mentioned pure aluminum.

[0049] Although not particularly limited, it is preferable that the Young's modulus of the material constituting the current collecting terminals is smaller than that of the material constituting sealing plate 14. The higher the Young's modulus value, the more difficult the material is to deform. Therefore, the current collecting terminals are made of a material that is more easily deformed than sealing plate 14. The Young's modulus of the material constituting the current collecting terminals may be less than half, or even less than one-tenth, of the Young's modulus of the material constituting sealing plate 14.

[0050] 5, in the current collecting terminal-sealing plate assembly 14A, it is preferable that at least a portion of the surface of the sealing plate 14 and / or the current collecting terminal be provided with a roughened area 30r. 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 30r is an area with more irregularities than its surroundings.

[0051] Although not particularly limited, it is preferable that at least a portion of the surface of the current collecting terminal that contacts the insulating member 40 be provided with a roughened area 30r. This advantageously improves the airtightness between the current collecting terminal and the insulating member 40. The roughened area 30r may be provided on the sealing plate outer surface 31 of the current collecting terminal, on the sealing plate inner surface 32, or on the shaft portion 33. Alternatively, it may be provided on all of the surfaces of the sealing plate outer surface 31, the sealing plate inner surface 32, and the shaft portion 33 that contact the insulating member 40. As described above, the location where the roughened area 30r is provided tends to exhibit an anchor effect and be particularly rigid. Therefore, when the roughened area 30r is provided on at least a portion of the surface of the current collecting terminal that contacts the insulating member 40, the effects of adjusting the yield strength and breaking strength of the sealing plate 14 and the current collecting terminal to fall within the above-described ranges can be more effectively achieved.

[0052] Although not particularly limited, roughened area 30r may be provided on sealing plate 14. Roughened area 30r is preferably provided on, for example, at least a portion of the surface of sealing plate 14 that comes into contact with insulating member 40. This can further improve the airtightness between sealing plate 14, the current collecting terminal, and insulating member 40.

[0053] <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.

[0054] The secondary battery 100 described above may include the steps of preparing the sealing plate 14, the positive electrode terminal 30, the negative electrode terminal 35, and other necessary components, integrally molding the sealing plate 14 and the current collector terminal, and assembling the integrally molded current collector terminal-sealing plate assembly 14A with the case body 12. Note that other steps may also be included at any stage.

[0055] In the preparation step, the sealing plate 14, the positive electrode terminal 30, the negative electrode terminal 35, and the electrode body 20 are prepared. The sealing plate 14, the positive electrode terminal 30, and the negative electrode terminal 35 are prepared to be made of materials whose 0.2% proof stress and breaking elongation satisfy the above-mentioned ranges. The positive electrode terminal 30 and the negative electrode terminal 35 are prepared so that the ends on the side placed inside the case body 12 can be inserted into the terminal mounting holes 18, 19.

[0056] 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.

[0057] FIG. 6 is a schematic diagram of a molding die 120. In the integral molding process, the sealing plate 14 and the current collector terminal 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. 6, 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.

[0058] In the part setting process, the sealing plate 14 and the current collecting terminals are attached to the molding die 120. First, the current collecting terminals are inserted into the terminal attachment holes 18 of the sealing plate 14. As described above, the current collecting terminals are configured with a size such that the sealing plate inner surface 32 can be inserted into the terminal attachment holes 18. Therefore, the current collecting terminals are inserted into the two terminal attachment holes 18 from the sealing plate inner surface 32. Then, the sealing plate 14, with the current collecting terminals inserted into the two terminal attachment holes 18, is attached to the recesses 121a of the lower die 121.

[0059] In the positioning process, the sealing plate 14 and the current collecting terminals are positioned. After the sealing plate 14 and the current collecting terminals 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 had been retracted to the rear, to the front. The slide members 123a and 123b then clamp the respective current collecting terminals. The current collecting terminals are supported by the slide members 123a and 123b and positioned at the desired positions.

[0060] In the upper mold setting step, upper mold 122 is set so as to sandwich sealing plate 14 and the current collector terminal 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, sandwiching sealing plate 14 and the current collector terminal therebetween.

[0061] 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. 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 the heating of the molding die 120 is complete, molten resin is supplied from the resin supply unit. The supplied resin is preferably a synthetic resin such as polyphenylene sulfide (PPS), polyetherimide (PEI), or polyamideimide (PAI). This allows for the formation of a stronger integrally molded part. The supplied resin fills the recesses of the upper die 122 and then passes through the terminal mounting holes 18 to fill the recesses 121a of the lower die 121. The molding die 120 and the molded product are then cooled. This allows for the sealing plate 14 and the current collecting terminal to be integrally molded.

[0062] 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 and the sealing plate 14 are molded integrally. Note that the component removal step may be followed by a step of removing burrs that may have occurred during molding.

[0063] 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 positive electrode tab group 23 of the electrode body 20 is connected to the second current collecting portion 52 of the positive electrode current collector 50, and the negative electrode tab group 25 of the electrode body 20 is connected to the second current collecting portion 62 of the negative electrode current collector 60. Next, the first current collecting portion 51 of the positive electrode current collector 50 is attached to the positive electrode terminal 30 of the current collector terminal-sealing plate assembly 14A, and the first current collecting portion 61 of the negative electrode current collector 60 is attached to the negative electrode terminal 35. Then, the first current collecting portion 51 and the second current collecting portion 52 of the positive electrode current collector 50 are connected, and the first current collecting portion 61 and the second current collecting portion 62 of the negative electrode current collector 60 are connected. This allows the current collector terminal-sealing plate assembly 14A and the electrode body 20 to be connected. 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 the winding axis WL of the electrode body 20 is oriented along the bottom surface 12a (i.e., the winding axis WL is oriented parallel to the long side direction Y) and is disposed inside the case body 12. 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, an electrolyte is injected through the liquid inlet 15, which is closed with the sealing member 16, thereby sealing the secondary battery 100. In this manner, the secondary battery 100 can be manufactured.

[0064] <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).

[0065] 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. [Explanation of symbols]

[0066] 10 Case (battery case) 12 Case body 12a Bottom 12b Long side wall 12c short side wall 12h opening 13 Welded parts 14 Sealing plate 14a Inner surface 14A Current collector terminal-sealing plate assembly 14b External surface 15 Liquid injection hole 16 Sealing member 17 Gas exhaust valve 18 Terminal mounting hole 18a Periphery 19 Terminal mounting hole 20 Electrode body 22 Positive electrode (positive electrode sheet) 22a Cathode active material layer 22c positive electrode core 22p positive electrode protective layer 22t Positive electrode tab 23 Positive electrode tab group 24 Negative electrode (negative electrode sheet) 24a Negative electrode active material layer 24c negative electrode core 24t negative electrode tab 25 Negative electrode tab group 26 Separator 30 Positive terminal 30r roughened area 31 Sealing plate outer side 32 Sealing plate inner side 33 Shaft 35 Negative terminal 40 Insulating material 40h through hole 41 First flange 42 Second flange 43 Cylindrical part 44 Protrusion 50 Positive electrode current collector 51 First current collector 52 Second current collector 60 Negative electrode current collector 61 First current collector 62 Second current collector 100 Secondary battery 120 Molding mold 121 Lower mold 121a Recess 122 Upper mold 123a Slide member 123b Slide member

Claims

1. a case body having an opening; a metal 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 has a 0.2% proof stress A of 95 to 350 N / mm ２ and is made of a metal material having a breaking elongation X of 4 to 27%; The current collecting terminal has a 0.2% yield strength B of 25 to 200 N / mm ２ and is made of a metal material having a breaking elongation Y of 20 to 45%; Here, the ratio (B / A) of the proof stress B to the proof stress A is 0.08 to 0.8, The ratio (Y / X) of the breaking elongation Y to the breaking elongation X is 1.1 to 10.

8.

2. At least a part of the surface of the collector terminal that comes into contact with the insulating member is made thicker than the surrounding surface. The power storage device according to claim 1 , further comprising an uneven roughened area.

3. An energy storage device as described in claim 1 or 2, wherein the sealing plate is made of at least one metal material selected from the group consisting of ferritic stainless steel, work-hardened Al-Mn alloy, and Al-Fe alloy.

4. The electrode body has a positive electrode and a negative electrode, the current collecting terminal has a positive electrode terminal connected to the positive electrode and a negative electrode terminal connected to the negative electrode, the positive electrode terminal is made of pure aluminum, the negative electrode terminal is made of tough pitch copper, The electricity storage device according to claim 3 , wherein the sealing plate is made of ferritic stainless steel.

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