Electricity storage device and method for manufacturing the same

Abstract

To provide a power storage device in which the generation of weld defect in a weld connection part is suppressed.SOLUTION: A power storage device disclosed here, comprises: a seal plate 14 that includes a terminal leading hole 18, and seals an open of a case main body; a collector part 50 that is electrically connected to an electrode in an inner part of the case main body, and includes a penetration hole 51h; a terminal 30 that includes a shaft part 30a that inserts the terminal leading hole 18 and the penetration hole 51h and a calking part 30c that is provided to one end part on the case main body side of the shaft part 30a and is calked to a peripheral edge of the penetration hole 51h; a step part that is provided to a side surface of the penetration hole 51h of the collector part 50, and into which at least part of the calking part 30c of the terminal 30 is arranged; and a weld bonding part J of a peripheral edge part of the penetration hole 51h of the collector part 50 and the calking part 30c of the terminal 30. At the neighbor of the weld bonding part J, a gap S is provided to between the collector part 50 and the terminal 30.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] A known configuration of an electric storage device, such as a lithium-ion battery, includes an electrode assembly having an electrode, a case body having an opening and housing the electrode assembly, a sealing plate having a terminal outlet hole and sealing the opening of the case body, a current collector having a through hole and electrically connected to the electrode, and a terminal inserted into the terminal outlet hole and the through hole and electrically connected to the electrode via the current collector. Patent Document 1, for example, discloses a conventional technique for electrically connecting the terminal and the current collector, in which a counterbore hole is formed around the through hole of the current collector, the terminal is crimped into the counterbore hole, and the crimped portion is welded to the edge of the counterbore hole. Patent Document 1 describes that crimping the terminal into the counterbore hole deforms the crimped terminal so that it contacts the bottom and side surfaces of the counterbore hole, reducing the likelihood of a gap occurring between the crimped portion of the terminal and the current collector, thereby improving crimping strength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-136105 [Patent Document 2] International Publication No. 2010-089852 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors' research has revealed that high adhesion between the crimped portion and current collecting portion of a terminal, as in the technology of Patent Document 1, for example, can easily cause welding defects at the welded joint. Specifically, during welding, high-temperature gas (fumes) can be generated due to the expansion of air and the vaporization of organic matter caused by the heat of welding. If the adhesion between the terminal and current collecting portion is high, the generated gas has no escape route and can accumulate at the welded joint. As a result, although the crimping strength can be improved, welding defects such as blowholes (see FIG. 12) and pits (open defects) are more likely to occur at the welded joint. Note that blowholes are internal defects and are extremely difficult to detect visually. Weld defects at the welded joint can lead to unstable electrical connections and increased electrical resistance.

[0005] The present invention has been made in view of the above circumstances, and aims to provide an electricity storage device in which the occurrence of welding defects at the welded joint between the terminal and the current collector is suppressed, and a method for manufacturing the same. [Means for solving the problem]

[0006] The present invention provides an electricity storage device comprising: an electrode body having an electrode; a case body having an opening and accommodating the electrode body; a sealing plate having a terminal pull-out hole and sealing the opening of the case body; a current collecting portion electrically connected to the electrode inside the case body and having a through hole; a shaft portion inserted through the terminal pull-out hole and the through hole; and a terminal having a crimping portion provided at one end of the shaft portion on the case body side and crimped to the periphery of the through hole; a step portion provided on a side surface of the through hole in the current collecting portion and at least a part of the crimping portion of the terminal is disposed; and a welded joint between the periphery of the through hole in the current collecting portion and the crimping portion of the terminal, wherein a gap is provided between the current collecting portion and the terminal near the welded joint.

[0007] In the above configuration, a step is provided on the side surface of the through hole of the current collector, and at least a portion of the crimping portion is disposed on the step. This improves the crimping strength. Furthermore, in the above configuration, a gap is provided near the welded joint, ensuring a space for gas to escape during welding. By ensuring a gas escape route in this way, the occurrence of welding defects in the welded joint can be suppressed. Consequently, a low-resistance welded joint can be stably formed, improving the reliability of electrical continuity.

[0008] Although not directly related to the technology disclosed herein, Patent Document 2 discloses that a groove portion that connects the inside and outside of the case body is provided at the fitting portion between the opening of the case body and the sealing plate. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view schematically illustrating an electricity storage device according to one embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a perspective view that schematically shows a combination of a sealing plate and an electrode assembly. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a wound electrode body. [Figure 5] FIG. 5 is a perspective view that schematically shows a sealing plate assembly. [Figure 6] FIG. 6 is a perspective view of the sealing plate of FIG. 5 turned upside down. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a partially enlarged cross-sectional view schematically showing the vicinity of the welded joint in FIG. [Figure 9] FIG. 9 is an exploded view of FIG. 7, which schematically shows the members before the crimping process. [Figure 10] FIG. 10 is a cross-sectional SEM image of the vicinity of the welded joint according to one example. [Figure 11] FIG. 11 is an X-ray CT image of the vicinity of the welded joint according to one example. [Figure 12] FIG. 12 is a cross-sectional SEM image of the vicinity of a welded joint according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the technology disclosed herein will be described below with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the present invention (for example, the general configuration and manufacturing process of an electricity storage device that do not characterize the present invention) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

[0011] In this specification, the term "electricity storage device" refers to a general device that can be repeatedly charged and discharged by the movement of charge carriers between a positive electrode and a negative electrode via an electrolyte. The electrolyte may be a liquid electrolyte (electrolytic solution), a gel electrolyte, or a solid electrolyte. Electricity storage devices include secondary batteries such as lithium ion batteries and nickel-metal hydride batteries, and capacitors such as lithium ion capacitors and electric double layer capacitors. In addition, in this specification, the expression "A to B" indicating a range means not less than A and not more than B, but also includes the meanings of "greater than A (exceeds A)" and "smaller than B (less than B)."

[0012] <Electricity storage device> Fig. 1 is a perspective view of the electricity storage device 100. Fig. 2 is a schematic longitudinal cross-sectional view taken along line II-II in Fig. 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction of the electricity storage device 100, the long side direction perpendicular to the short side direction, and the up-down direction perpendicular to the short side direction and the long side direction, respectively. However, these directions are merely used for the convenience of description and do not limit the installation form of the electricity storage device 100 in any way.

[0013] As shown in Fig. 2, the electricity storage device 100 includes a battery case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, and a negative electrode current collector 60. Although not shown, the electricity storage device 100 further includes a non-aqueous electrolyte. The electricity storage device 100 is configured by accommodating the electrode assembly 20 and a non-aqueous electrolyte (not shown) in the battery case 10. The electricity storage device 100 is a non-aqueous electrolyte secondary battery. More specifically, it is a lithium-ion secondary battery.

[0014] The battery case 10 is a housing that houses the electrode assembly 20 and the nonaqueous electrolyte. Here, the battery case 10 has a flat, bottomed, rectangular parallelepiped (rectangular) outer shape. The material of the battery case 10 may be the same as that conventionally used, and is not particularly limited. The battery case 10 is preferably made of metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like. As shown in FIG. 2, the battery case 10 includes a case body 12 having an opening 12h, and a sealing plate (lid) 14 that closes the opening 12h.

[0015] As shown in Fig. 1, the case body 12 includes a substantially rectangular bottom wall 12a, a pair of long side walls 12b extending from the long sides of the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the short sides of the bottom wall 12a and facing each other. The area of ​​the short side walls 12c is smaller than the area of ​​the long side walls 12b. An electrode assembly 20 and a nonaqueous electrolyte are housed inside the case body 12. In this specification, the term "substantially rectangular" is intended to encompass not only a perfect rectangular shape (rectangular shape) but also shapes in which the corners connecting the long and short sides of the rectangle are rounded or have notches at the corners.

[0016] The sealing plate 14 is a plate-like member having a predetermined thickness. The sealing plate 14 is attached to the case body 12 so as to close the opening 12h of the case body 12. The sealing plate 14 faces the bottom wall 12a of the case body 12. The sealing plate 14 has a substantially rectangular shape in a plan view. The battery case 10 is integrated by joining (for example, welding) the sealing plate 14 to the periphery of the opening 12h of the case body 12. The battery case 10 is hermetically sealed (sealed).

[0017] As shown in FIG. 2 , the sealing plate 14 is provided with a liquid inlet 15, a gas release valve 17, and two terminal outlet holes 18 and 19. The liquid inlet 15 is for injecting nonaqueous 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. 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. The terminal outlet holes 18 and 19 are formed at both ends of the sealing plate 14 in the long side direction Y. The terminal outlet holes 18 and 19 penetrate the sealing plate 14 in the up-down direction Z. Here, the terminal outlet holes 18 and 19 are cylindrical. The terminal pull-out holes 18 and 19 each have an inner diameter large enough to allow the insertion of the positive electrode terminal 30 and the negative electrode terminal 40 before they are attached to the sealing plate 14 (before crimping). For example, the terminal pull-out hole 18 is formed smaller than the shaft portion 30a of the positive electrode terminal 30 before crimping, which will be described later.

[0018] FIG. 3 is a perspective view that schematically shows an assembly of a sealing plate 14 (more specifically, a sealing plate assembly described later) and an electrode assembly group 20. Here, the electrode assembly group 20 has three electrode bodies 20a, 20b, and 20c. However, the number of electrode bodies arranged inside one battery case 10 is not particularly limited, and may be one, or two or more (plural). Furthermore, the configuration of the electrode bodies 20a, 20b, and 20c is not particularly limited, and may be the same as conventional ones.

[0019] FIG. 4 is a schematic diagram showing the configuration of the electrode assembly 20a. While the electrode assembly 20a will be described in detail below as an example, the electrode assemblies 20b and 20c may also have a similar configuration. The electrode assembly 20a has a positive electrode 22 and a negative electrode 24. The positive electrode 22 and / or the negative electrode 24 are examples of the electrodes disclosed herein. The electrode assembly 20a here is a flat wound electrode assembly formed by stacking a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 with two strip-shaped separators 26 interposed therebetween and winding the stack around a winding axis WL. However, the electrode assemblies 20a, 20b, and 20c may also be laminated electrode assemblies formed by stacking a square-shaped (typically rectangular) positive electrode and a square-shaped (typically rectangular) negative electrode in an insulated state.

[0020] 2 and 4, the electrode body 20a is disposed inside the battery case 10 with the winding axis WL oriented parallel to the long side direction Y. In other words, the electrode body 20a is disposed inside the battery case 10 with the winding axis WL oriented parallel to the bottom wall 12a and perpendicular to the short side wall 12c. As shown in FIG. 2, the electricity storage device 100 has a so-called horizontal tab structure in which a positive electrode tab group 23 and a negative electrode tab group 25, which will be described later, are located on the left and right sides of the electrode body group 20. However, the electricity storage device 100 may also have a so-called top tab structure in which the positive electrode tab group 23 and the negative electrode tab group 25, which will be described later, are located above and below the electrode body group 20.

[0021] As shown in FIG. 4, the positive electrode 22 includes a positive electrode current collector 22c, a positive electrode active material layer 22a, and a positive electrode protective layer 22p adhered to at least one surface of the positive electrode current collector 22c. However, the positive electrode protective layer 22p is not essential and may be omitted in other embodiments. The positive electrode current collector 22c is strip-shaped. The positive electrode current collector 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode current collector 22c is a metal foil, specifically, an aluminum foil.

[0022] A plurality of positive electrode tabs 22t are provided at one end of the positive electrode current collector 22c in the long side direction Y (the left end in FIG. 4). Each of the plurality of positive electrode tabs 22t is convex and protrudes toward one side in the long side direction Y (the left side in FIG. 4). The plurality of positive electrode tabs 22t are provided at intervals (intermittently) along the longitudinal direction of the positive electrode 22. Here, the positive electrode tabs 22t are part of the positive electrode current collector 22c and are made of metal foil (aluminum foil). The positive electrode tab 22t is a portion of the positive electrode current collector 22c where the positive electrode active material layer 22a and the positive electrode protective layer 22p are not formed (exposed current collector portion). However, the positive electrode tab 22t may be a member separate from the positive electrode current collector 22c. The plurality of positive electrode tabs 22t are stacked at one end of the long side direction Y (the left end in FIG. 4) to form a positive electrode tab group 23, as shown in FIG. 2. The positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collector 50. A positive electrode second current collector 52, which will be described later, is attached to the positive electrode tab group 23.

[0023] 4, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the strip-shaped positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material (e.g., a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide) that can reversibly store and release charge carriers. The positive electrode active material layer 22a may further contain optional components other than the positive electrode active material, such as a conductive material, a binder, and various additive components.

[0024] As shown in Fig. 4, the positive electrode protective layer 22p is provided at the boundary between the positive electrode current collector 22c and the positive electrode active material layer 22a in the long side direction Y. Here, the positive electrode protective layer 22p is provided at one end of the positive electrode current collector 22c in the long side direction Y (the left end in Fig. 4). 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 further contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additive components.

[0025] As shown in FIG. 4, the negative electrode 24 includes a negative electrode current collector 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector 24c. The negative electrode current collector 24c is strip-shaped. The negative electrode current collector 24c is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. Here, the negative electrode current collector 24c is a metal foil, specifically, a copper foil.

[0026] A plurality of negative electrode tabs 24t are provided at one end of the negative electrode current collector 24c in the long side direction Y (the right end in FIG. 4). Each of the plurality of negative electrode tabs 24t is convex and protrudes toward one side in the long side direction Y (the right side in FIG. 4). The plurality of negative electrode tabs 24t are provided at intervals (intermittently) along the longitudinal direction of the negative electrode 24. Here, the negative electrode tabs 24t are part of the negative electrode current collector 24c and are made of metal foil (copper foil). The negative electrode tab 24t is a portion of the negative electrode current collector 24c where the negative electrode active material layer 24a is not formed (exposed current collector portion). However, the negative electrode tab 24t may be a member separate from the negative electrode current collector 24c. The plurality of negative electrode tabs 24t are stacked at one end of the long side direction Y (the right end in FIG. 4) to form a negative electrode tab group 25 as shown in FIG. 2. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via the negative electrode current collector 60. The negative electrode tab group 25 is provided with a negative electrode second current collector 62, which will be described later.

[0027] As shown in Fig. 4, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the strip-shaped negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material (e.g., a carbon material such as graphite) that can reversibly store and release charge carriers. The negative electrode active material layer 24a may further contain optional components other than the negative electrode active material, such as a binder, a dispersant, and various additive components.

[0028] The separator 26 is a member that insulates the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. A porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable as the separator 26. Note that a functional layer, such as an adhesive layer containing a binder or a heat resistance layer (HRL) containing an inorganic filler, may be provided on the surface of the separator 26.

[0029] The non-aqueous electrolyte may be the same as conventional ones and is not particularly limited. The non-aqueous electrolyte typically contains a non-aqueous solvent and a supporting salt. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as LiPF6. However, in other embodiments, the electricity storage device 100 may include, as the electrolyte, an aqueous electrolyte, a gel electrolyte, a solid electrolyte (solid electrolyte), or the like, instead of a non-aqueous electrolyte.

[0030] FIG. 5 is a perspective view schematically illustrating a sealing plate assembly. FIG. 6 is a perspective view of the sealing plate 14 of FIG. 5 turned upside down. FIG. 6 shows the surface (inner surface) of the sealing plate 14 facing the case body 12. The sealing plate assembly here is a combination of the sealing plate 14, a positive electrode terminal 30, a negative electrode terminal 40, a first positive electrode current collecting portion 51 of the positive electrode current collecting portion 50, a first negative electrode current collecting portion 61 of the negative electrode current collecting portion 60, two resin members 70, and two gaskets 90. The positive electrode terminal 30, the gasket 90, the first positive electrode current collecting portion 51 of the positive electrode current collecting portion 50, and the resin members 70 are integrated into the sealing plate 14 by crimping the positive electrode terminal 30 and welding it to the first positive electrode current collecting portion 51. Similarly, the negative electrode terminal 40, the gasket 90, the negative electrode first current collecting portion 61 of the negative electrode current collecting portion 60, and the resin member 70 are integrated into the sealing plate 14 by crimping the negative electrode terminal 40 and welding it to the negative electrode first current collecting portion 61.

[0031] As shown in FIGS. 5 and 6, the positive electrode terminal 30 and the negative electrode terminal 40 are each attached to the sealing plate 14. The positive electrode terminal 30 is disposed on one side of the sealing plate 14 in the long side direction Y (the left side in FIGS. 5 and 6). The negative electrode terminal 40 is disposed on the other side of the sealing plate 14 in the long side direction Y (the right side in FIGS. 5 and 6). The positive electrode terminal 30 and / or the negative electrode terminal 40 are examples of the terminals disclosed herein. In particular, the positive electrode terminal 30 is preferably a terminal disclosed herein. Note that the positive electrode terminal 30 will be described in detail below as an example, but the negative electrode terminal 40 can also have a similar configuration.

[0032] As shown in FIG. 2 , the positive electrode terminal 30 is electrically connected to each of the positive electrodes 22 (more specifically, the positive electrode tab group 23) of the electrode bodies 20a, 20b, and 20c inside the battery case 10 via a positive electrode current collector 50. The positive electrode terminal 30 is electrically connected to the positive electrode first current collector 51 of the positive electrode current collector 50 by crimping (mechanical fastening) and welding (metallurgical joining). The positive electrode terminal 30 is preferably made of metal, more preferably aluminum or an aluminum alloy. According to the inventors' investigations, when the positive electrode terminal 30 is made of aluminum or an aluminum alloy, welding defects tend to occur more frequently due to, for example, high metal fluidity during welding. Therefore, applying the technology disclosed herein is particularly effective.

[0033] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 5, and is a partially enlarged cross-sectional view schematically illustrating the vicinity of the positive electrode terminal 30. FIG. 8 is a partially enlarged cross-sectional view schematically illustrating the vicinity of the welded joint J in FIG. 7. FIG. 9 is an exploded view of FIG. 7, schematically illustrating the components before crimping. Note that in FIGS. 7 and 9, the central axis CL of the positive electrode terminal 30 is indicated by a dashed line. As shown in FIG. 7, the positive electrode terminal 30 is inserted through the terminal lead-out hole 18 of the sealing plate 14 and extends from the inside to the outside of the sealing plate 14. The positive electrode terminal 30 has a shaft portion 30a, a flange portion 30f whose diameter is enlarged from the upper end of the shaft portion 30a, and a crimping portion 30c provided at the lower end of the shaft portion 30a.

[0034] As shown in Fig. 7, the shaft portion 30a extends in the up-down direction Z along the central axis CL. The shaft portion 30a is inserted through the terminal lead-out hole 18 of the sealing plate 14 and a through-hole 51h (see Fig. 9) of the positive electrode first current collecting portion 51, which will be described later. Here, the shaft portion 30a has a cylindrical shape. As shown in Fig. 9, before the crimping process, the lower end of the shaft portion 30a, i.e., the end opposite to the side where the flange portion 30f is located, is hollow.

[0035] As shown in FIG. 7, the flange portion 30f is connected to the upper end of the shaft portion 30a and extends upward. The flange portion 30f has a larger outer shape than the shaft portion 30a. The flange portion 30f has a larger outer shape than the terminal outlet hole 18 of the sealing plate 14. The flange portion 30f protrudes from the terminal outlet hole 18 to the outside of the battery case 10 (more specifically, to the outer surface of the sealing plate 14). In this example, the flange portion 30f has a circular shape in a plan view. In this example, the flange portion 30f has a substantially cylindrical outer shape. The axis of the flange portion 30f coincides with the axis of the shaft portion 30a.

[0036] As shown in FIG. 7, the crimping portion 30c is provided at the end of the shaft portion 30a inside the battery case 10 (the lower end in FIG. 7). The crimping portion 30c is provided on the periphery of the terminal outlet hole 18 of the sealing plate 14. The crimping portion 30c is a portion where the lower end of the shaft portion 30a is expanded by crimping when the positive terminal 30 is attached to the sealing plate 14. The crimping portion 30c is preferably provided symmetrically with respect to the central axis CL of the positive terminal 30. This ensures stable electrical connection between the positive terminal 30 and the positive current collecting portion 50, improving the reliability of electrical continuity of the positive terminal 30, even if vibrations or impacts are applied during use of the power storage device 100. Here, the crimping portion 30c is annular (e.g., circular) and provided around the entire periphery of the terminal outlet hole 18.

[0037] 7, the gasket 90 is an insulating member disposed between the sealing plate 14 and the positive electrode terminal 30. Here, the gasket 90 has the function of insulating the sealing plate 14 from the positive electrode terminal 30 and closing the terminal withdrawal hole 18. The gasket 90 is made of an electrically insulating and elastically deformable resin material, for example, a fluorinated resin such as perfluoroalkoxy fluorine resin (PFA), polyphenylene sulfide resin (PPS), aliphatic polyamide, or the like. Here, the gasket 90 has a tubular portion 90a and a base portion 90b.

[0038] The tubular portion 90a is a portion that prevents direct contact between the sealing plate 14 and the shaft portion 30a of the positive electrode terminal 30. The tubular portion 90a has a hollow cylindrical shape. The tubular portion 90a has a through-hole 90h (see FIG. 9 ) that penetrates in the up-down direction Z at a position corresponding to the terminal lead-out hole 18 of the sealing plate 14. The through-hole 90h has an inner diameter large enough to allow the shaft portion 30a of the positive electrode terminal 30 to be inserted therethrough before crimping. The tubular portion 90a is inserted into the terminal lead-out hole 18 of the sealing plate 14. The base 90b is a portion that prevents direct contact between the sealing plate 14 and the flange portion 30f of the positive electrode terminal 30. The base 90b is connected to the upper end of the tubular portion 90a. Here, the base 90b is provided in an annular shape so as to surround the terminal lead-out hole 18 of the sealing plate 14. The base portion 90b is sandwiched between the lower surface of the flange portion 30f of the positive electrode terminal 30 and the sealing plate 14, and is compressed in the up-down direction Z by crimping.

[0039] As shown in FIG. 2 , the positive electrode current collector 50 forms a conductive path electrically connecting the positive electrode tab group 23, which is composed of multiple positive electrode tabs 22t, to the positive electrode terminal 30. The positive electrode current collector 50 is an example of a current collector disclosed herein. The positive electrode current collector 50 may be made of the same metal as the positive electrode current collector 22c, such as a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode current collector 50 is preferably made of aluminum or an aluminum alloy. According to the inventors' investigations, when the positive electrode current collector 50 is made of aluminum or an aluminum alloy, welding defects tend to occur more frequently due to, for example, high metal fluidity during welding. Therefore, applying the technology disclosed herein is particularly effective. Here, the positive electrode current collecting portion 50 includes a positive electrode first current collecting portion 51 (see also Figure 6) extending along the inner surface of the sealing plate 14, and a positive electrode second current collecting portion 52 (see also Figure 3) extending along the short side wall 12c of the case body 12.

[0040] As shown in FIG. 7, the positive electrode first current collecting portion 51 is fixed to the sealing plate 14 by a crimping portion 30c and a welded joint J. As shown in FIG. 6, the positive electrode first current collecting portion 51 is generally L-shaped. The positive electrode first current collecting portion 51 may be formed by bending a single member, for example, by pressing or the like, or by integrating multiple members by welding or the like. The positive electrode first current collecting portion 51 has a first portion 511 that extends horizontally along the inner surface of the sealing plate 14, and a second portion 512 that extends in the up-down direction Z from one end of the first portion 511 in the long side direction Y (the left end in FIG. 6).

[0041] As shown in FIG. 7, the first portion 511 is electrically connected to the positive electrode terminal 30 via the crimped portion 30c and the welded joint J. The first portion 511 is flat and has a thickness T (see FIG. 9). Although not particularly limited, the thickness T is typically 0.5 to 5 mm, for example, approximately 1 to 3 mm, or 1.5 to 2 mm. In one example, the thickness T of the first portion 511 is 1.5 mm. As shown in FIG. 9, the first portion 511 has an upper surface 51u and a lower surface 51d. A resin member 70 is disposed between the sealing plate 14 and the upper surface 51u of the first portion 511. The first portion 511 is insulated from the sealing plate 14 by the resin member 70. A through-hole 51h penetrating the first portion 511 in the up-down direction Z is provided at a position corresponding to the terminal lead-out hole 18 of the sealing plate 14.

[0042] As shown in FIG. 9, the through hole 51h has an upper end formed in a cylindrical shape and a lower end formed in an inverted tapered shape that increases in diameter toward the lower surface 51d (in other words, as it moves away from the upper surface 51u). The taper angle is preferably, for example, 60°±15°, and more preferably 60°±10°. However, the through hole 51h may be formed in a cylindrical shape as a whole. As shown in FIG. 6, the positive electrode terminal 30 (more specifically, the shaft portion 30a) is inserted through the through hole 51h. As shown in an enlarged view in FIG. 8, a step portion 51g is provided on a part of the side surface of the through hole 51h.

[0043] The step portion 51g is a portion that is narrowed inward from the side surface of the through hole 51h. The step portion 51g is provided near the end portion on the lower surface 51d side of the through hole 51h. Providing the step portion 51g can improve the strength and robustness of the crimped portion 30c. The step portion 51g is preferably formed symmetrically with respect to the central axis CL of the positive electrode terminal 30. This can ensure stable electrical connection between the positive electrode terminal 30 and the positive electrode current collecting part 50, for example, even if vibrations or impacts are applied during use of the electricity storage device 100, thereby improving the conduction reliability of the positive electrode terminal 30. Although not shown, the step portion 51g here has a substantially cylindrical shape.

[0044] As shown in FIG. 8, the step portion 51g has a bottom surface 51b and a side surface 51s. The bottom surface 51b extends substantially parallel (within ±5°) to the lower surface 51d and the upper surface 51u of the first portion 511. Here, the bottom surface 51b is a flat surface (linear in cross section). However, it may also be a curved surface (curved in cross section). Here, the bottom surface 51b does not abut the crimped portion 30c. However, in other embodiments, the bottom surface 51b may abut the crimped portion 30c. The side surface 51s extends substantially perpendicular (within ±5°) along the central axis CL of the positive terminal 30. At least a portion of the crimped portion 30c of the positive terminal 30 is disposed (housed) in the step portion 51g. It is preferable that the side surface 51s abuts the crimped portion 30c.

[0045] The size and shape of the stepped portion 51g are preferably adjusted as appropriate depending on, for example, the material (fluidity when melted) of the positive electrode terminal 30 and the shape (length, etc.) of the shaft portion 30a. Therefore, although not particularly limited, in some embodiments, the depth D1 of the stepped portion 51g (maximum length in the vertical direction Z, the vertical length from the lower surface 51d to the bottom surface 51b) is typically 0.1 to 2 mm, for example, 0.2 to 1.5 mm, 0.3 to 1 mm, or even 0.4 to 0.5 mm. In one example, the depth D1 of the stepped portion 51g is 0.45 mm.

[0046] In some embodiments, the ratio (D1 / T) of the depth D1 of the stepped portion 51g to the thickness T (see FIG. 9 ) of the positive electrode first current collecting portion 51 (specifically, the first portion 511) is preferably 1 / 2 or less, more preferably 1 / 3 or less. This makes it easier to ensure the gap S (described later) even after the crimping process (in other words, during the welding process to form the welded joint J). In some embodiments, the ratio (D1 / T) is preferably 1 / 20 or more, more preferably 1 / 10 or more, more preferably 1 / 5 or more, and even more preferably 1 / 4 or more. This facilitates contact between the crimped portion 30c and the stepped portion 51g, improving crimping strength and electrical connection reliability while reducing electrical resistance. In one example, the ratio (D1 / T) is 0.3 (=0.45 / 1.5).

[0047] In this embodiment, bottom surface 51b of step portion 51g is provided with recessed portion 51r (including a groove, a notch, etc.) recessed toward top surface 51u (upward in FIG. 8). Providing recessed portion 51r can prevent void S, which will be described later, from being closed during the crimping process, and makes it easier to maintain void S, which will be described later, even after the crimping process (in other words, during the welding process to form welded joint J).

[0048] Here, recess 51r is provided near the outer peripheral edge of bottom surface 51b of stepped portion 51g. Here, recess 51r is provided at the boundary between bottom surface 51b and side surface 51s. Recess 51r is preferably provided, for example, on bottom surface 51b within a range of length from the outer peripheral edge to within ½ of width W1 of stepped portion 51g. The area near the outer peripheral edge of bottom surface 51b is a location into which the material of the tip portion of shaft portion 30a is less likely to flow during the crimping process described below. Therefore, by providing recess 51r at the boundary, it becomes easier to ensure gap S, described later, even after crimping (in other words, during welding to form welded joint J).

[0049] The size, shape, and arrangement of the recess 51r are preferably adjusted as appropriate, depending on, for example, the material (fluidity when melted) of the positive electrode terminal 30 and the shape (length, etc.) of the shaft portion 30a. Therefore, although not particularly limited, in some embodiments, the width W2 of the recess 51r (maximum length in the long side direction Y) is typically smaller than the width W1 of the stepped portion 51g. Furthermore, the depth D2 of the recess 51r (maximum length in the vertical direction Z, i.e., the vertical length from the bottom surface 51b of the stepped portion 51g to the end of the recess 51r on the upper surface 51u side) is typically 1 mm or less, for example, approximately 0.01 to 0.5 mm, 0.05 to 0.3 mm, or even 0.1 to 0.2 mm. In one example, the depth D2 of the recess 51r is 0.1 mm.

[0050] In some embodiments, the depth D2 of the recess 51r is preferably smaller than the depth D1 of the stepped portion 51g. The ratio (D2 / D1) of the depth D2 of the recess 51r to the depth D1 of the stepped portion 51g is preferably 1 / 2 or less, more preferably 1 / 3 or less, or even 1 / 4 or less. This facilitates contact between the crimping portion 30c and the stepped portion 51g, improving crimping strength and electrical reliability while reducing electrical resistance. The ratio (D2 / D1) is preferably 1 / 20 or more, more preferably 1 / 10 or more, and even more preferably 1 / 5 or more. This makes it easier to maintain the gap S (described later) even after crimping (in other words, during welding to form the welded joint J). In one example, the ratio (D2 / D1) is approximately 0.22 (=0.1 / 0.45).

[0051] Here, the recess 51r is a trapezoidal groove that is approximately trapezoidal in cross section. However, the recess 51r may have other shapes, such as an approximately semicircular, rectangular, or triangular shape in cross section. The recess 51r may also be a round groove, a square groove, a triangular groove, or the like. Also, although there is only one recess 51r here, two or more recesses 51r may be provided on the bottom surface 51b. Furthermore, in other embodiments, the recess 51r may be provided on the side surface 51s, or on both the bottom surface 51b and the side surface 51s.

[0052] The recess 51r is preferably provided symmetrically with respect to the central axis CL of the positive electrode terminal 30. This makes it possible to maintain stable electrical connection between the positive electrode terminal 30 and the positive electrode current collecting part 50, even when vibrations, shocks, or the like are applied during use of the electricity storage device 100, thereby improving the conduction reliability of the positive electrode terminal 30. The recess 51r is preferably provided continuously in the circumferential direction of the through-hole 51h. In plan view, the recess 51r is preferably provided in a ring-shaped (e.g., circular ring), U-shaped, C-shaped (semi-ring) or other shape on the periphery of the through-hole 51h, and is particularly preferably provided in a ring-shaped (e.g., circular ring) shape.

[0053] 7 and 8, a welded joint J is formed at the boundary between the periphery of the through-hole 51h of the first portion 511 and the crimped portion 30c of the positive terminal 30. The presence of the welded joint J makes it possible to maintain a stable electrical connection between the positive terminal 30 and the positive current collecting part 50, thereby improving the reliability of conduction. The welded joint J is formed by, for example, laser welding, electron beam welding, ultrasonic welding, resistance welding, TIG (Tungsten Inert Gas) welding, or the like.

[0054] The welded joint J is preferably provided symmetrically with respect to the central axis CL of the positive electrode terminal 30. This makes it possible to maintain a stable electrical connection between the positive electrode terminal 30 and the positive electrode current collecting part 50, even if vibrations, shocks, or the like are applied during use of the electricity storage device 100, thereby improving the conduction reliability of the positive electrode terminal 30. As shown in Fig. 6, the welded joint J here has an annular (e.g., circular) shape and is provided around the entire periphery of the through-hole 51h.

[0055] As shown in FIG. 8, the welded joint J extends from the lower surface 51d of the first portion 511 to a portion of the side surface 51s of the stepped portion 51g. Preferably, the welded joint J is not provided in the recess 51r. The depth D3 of the welded joint J (the maximum length in the vertical direction Z, the vertical length from the lower surface 51d of the first portion 511 to the end of the welded joint J on the upper surface 51u side) is preferably smaller than the depth D1 of the stepped portion 51g. The depth D3 of the welded joint J is typically 0.15 mm or more, for example, 0.15 to 0.5 mm, 0.3 to 0.4 mm, or even approximately 0.32±0.014 mm. In one example, the depth D3 of the welded joint J is 0.32 mm.

[0056] In some embodiments, the ratio (D3 / D1) of the depth D3 of the welded joint J to the depth D1 of the stepped portion 51g is preferably 2 / 3 or less, and more preferably 1 / 2 or less. This makes it easier to ensure a gap S, which will be described later, even after the crimping process (in other words, during the welding process to form the welded joint J). The ratio (D3 / D1) is preferably 1 / 5 or more, and more preferably 1 / 4 or more, or 1 / 3 or more. This allows for an even higher level of improvement in electrical conductivity reliability.

[0057] In the technology disclosed herein, as shown in FIGS. 7 and 8 , a gap S is provided between the first portion 511 and the positive electrode terminal 30 near the welded joint J, typically so as to be in contact with the welded joint J. This gap S indicates that a space was provided as an escape route for gas during the welding process to form the welded joint J. FIG. 10 is a cross-sectional SEM image of the vicinity of the welded joint J according to one example. By providing a gap (an escape route for gas) between the terminal and the current collector near the welded joint J in this manner, it is possible to prevent welding defects such as blowholes and pits from occurring in the welded joint J. This in turn allows a low-resistance welded joint J to be formed reliably, improving electrical conductivity reliability.

[0058] The size, shape, arrangement, etc. of the void S are not particularly limited. In some embodiments, the void S is preferably provided in a portion including the recess 51r, and more preferably provided across the recess 51r and a portion (typically the upper end) of the step portion 51g. The height (maximum length in the vertical direction Z) of the void S is typically smaller than the depth D1 of the step portion 51g. The height of the void S may be smaller than the depth D3 of the welded joint J. The height of the void S is preferably equal to or larger than the depth D2 of the recess 51r. The width (maximum length in the long side direction Y) of the void S is typically smaller than the width W1 of the step portion 51g. The width of the void S is preferably equal to or larger than the width W2 of the recess 51r. By setting the size of the void S to a predetermined value or greater, the effects of the technology disclosed herein can be stably exhibited. By setting the size of the void S to a predetermined value or less, the electrical resistance can be reduced.

[0059] As shown in FIG. 10, the void S is preferably provided near the outer periphery of the bottom surface 51b of the stepped portion 51g. The void S is preferably provided at the boundary between the bottom surface 51b and the side surface 51s. For example, the void S is preferably provided on the bottom surface 51b within a range of a length from the outer periphery to within half the width W1 of the stepped portion 51g. This portion is less likely to be filled with excess material during the crimping process. Therefore, the void S can be reliably secured. The presence or absence, shape, and position of the void S can be determined, for example, from an X-ray CT image. The X-ray CT image allows the void S to be clearly distinguished from internal defects such as blowholes.

[0060] The gap S is preferably provided symmetrically with respect to the central axis CL of the positive terminal 30. This allows a stable electrical connection between the positive terminal 30 and the positive current collecting part 50 to be maintained even if vibrations, shocks, or the like are applied during use of the electricity storage device 100, thereby improving the conduction reliability of the positive terminal 30. The gap S is preferably provided continuously in the circumferential direction of the through hole 51h. This allows the effects of the technology disclosed herein to be exerted to a higher level, and the occurrence of welding defects can be significantly reduced.

[0061] Fig. 11 is an X-ray CT image of the vicinity of the welded joint according to one example. In plan view, the gap S is preferably provided around the periphery of the through hole 51h in a ring-like shape (e.g., a circular ring), a U-shape, a C-shape (semi-ring), or the like, and among these, it is particularly preferable that the gap S be provided in a ring-like shape (e.g., a circular ring) as shown in Fig. 11. In other words, it is particularly preferable that the gap S be provided continuously around the entire circumference of the through hole 51h.

[0062] As shown in Fig. 2, the positive electrode second current collecting portion 52 extends along the short side wall 12c of the case body 12. One end (the upper end in Fig. 2) of the positive electrode second current collecting portion 52 is electrically connected to the positive electrode first current collecting portion 51 (more specifically, the second portion 512 (see Fig. 6)). The other end (the lower end in Fig. 2) of the positive electrode second current collecting portion 52 is attached to the positive electrode tab group 23 and electrically connected to the plurality of positive electrode tabs 22t. The positive electrode second current collecting portion 52 and the positive electrode tab group 23 are joined by welding, for example, with the plurality of positive electrode tabs 22t overlapping each other.

[0063] 7, the resin member 70 is an insulating member disposed between the lower surface (inner surface) of the sealing plate 14 and the first portion 511 of the positive electrode first current collecting portion 51. The resin member 70 is made of an elastically deformable resin material that has electrical insulation and resistance to the nonaqueous electrolyte solution used, such as a fluorinated resin such as perfluoroalkoxy fluorine resin (PFA) or polyphenylene sulfide resin (PPS). As shown in FIGS. 7 and 8, the resin member 70 has a base portion 70a and a plurality of protrusions 70b.

[0064] As shown in FIG. 7, the base portion 70a is a portion that prevents direct contact between the sealing plate 14 and the positive electrode first current collecting portion 51. The base portion 70a extends horizontally along the inner surface of the sealing plate 14. The base portion 70a has a through-hole 70h (see FIG. 9) that penetrates in the up-down direction Z at a position corresponding to the terminal lead-out hole 18 of the sealing plate 14. The shaft portion 30a of the positive electrode terminal 30 and the tubular portion 90a of the gasket 90 are inserted into the through-hole 70h. The protrusion 70b protrudes toward the electrode assembly group 20 beyond the base portion 70a. The number of protrusions 70b is the same as the number of electrode bodies 20a, 20b, and 20c that make up the electrode assembly group 20. That is, there are three protrusions.

[0065] As shown in FIG. 2 , the negative electrode terminal 40 is electrically connected to the negative electrode 24 (more specifically, the negative electrode tab group 25) of the electrode bodies 20a, 20b, and 20c inside the battery case 10 via the negative electrode current collecting portion 60. The configuration of the negative electrode terminal 40 may be the same as or different from the configuration of the positive electrode terminal 30 described above. Like the positive electrode terminal 30, the negative electrode terminal 40 is electrically connected to the negative electrode first current collecting portion 61 of the negative electrode current collecting portion 60 by crimping (mechanical fastening) and welding (metallurgical joining). The negative electrode terminal 40 extends from the inside to the outside of the sealing plate 14 through the terminal lead-out hole 19 of the sealing plate 14. The negative electrode terminal 40 is provided symmetrically to the positive electrode terminal 30 and includes a flange portion (reference numeral omitted), a shaft portion 40a, and a crimped portion 40c.

[0066] The negative electrode terminal 40 is preferably made of metal, and more preferably made of copper or a copper alloy, for example. The negative electrode terminal 40 may be configured by joining two conductive members together. For example, the shaft portion 40a and the clamping portion 40c of the negative electrode terminal 40, which are connected to the negative electrode current collecting portion 60, may be made of copper or a copper alloy, and the flange portion that protrudes from the terminal pull-out hole 19 to the outside of the battery case 10 (more specifically, to the outer surface of the sealing plate 14) may be made of aluminum or an aluminum alloy.

[0067] As shown in FIG. 2 , the negative electrode current collector 60 forms a conductive path that electrically connects the negative electrode tab group 25, which is composed of multiple negative electrode tabs 24t, to the negative electrode terminal 40. The negative electrode current collector 60 is an example of a current collector disclosed herein. The negative electrode current collector 60 may be made of the same metal as the negative electrode current collector 24c, such as a conductive metal such as copper, a copper alloy, nickel, or stainless steel. Here, the negative electrode current collector 60 includes a negative electrode first current collector 61 and a negative electrode second current collector 62. The configurations of the negative electrode first current collector 61 and the negative electrode second current collector 62 may be the same as those of the positive electrode first current collector 51 and the positive electrode second current collector 52 of the positive electrode current collector 50. As shown in FIG. 6 , the negative electrode first current collector 61 is welded to the crimped portion 40c of the negative electrode terminal 40. A welded joint J is formed at the boundary between the negative electrode first current collecting portion 61 and the crimping portion 40c, similar to the positive electrode side.

[0068] <Method for manufacturing sealing plate assembly> The sealing plate assembly shown in FIGS. 5 and 6 can be produced by fixing a positive electrode terminal 30, a positive electrode current collector 50 (specifically, the positive electrode first current collector 51), a negative electrode terminal 40, and a negative electrode current collector 60 (specifically, the negative electrode first current collector 61) to the sealing plate 14 while insulated from the sealing plate 14. Although not particularly limited, the sealing plate assembly can be produced by a manufacturing method including, for example, a current collector preparation step (step S1) for preparing the current collector, a component assembly step (step S2), a crimping step (step S3) for forming a crimped portion at one end of the shaft, and a welding joining step (step S4) for forming a welded joint at the boundary between the crimped portion and the current collector. While the positive electrode side will be described in detail below, the negative electrode side may be similarly produced. In this case, the term "positive electrode" can be appropriately replaced with "negative electrode." The manufacturing method disclosed herein may further include other processes at any stage. For example, after the crimping process, an inspection process of the crimped portion (e.g., a crimp diameter inspection process) may be included, and only those crimped portions that meet a predetermined standard may be subjected to the welding and joining process.

[0069] In the current collector preparation step (step S1), a positive electrode current collector 50 and a negative electrode current collector 60 are prepared. As described above, the positive electrode current collector 50 has a first portion 511 including a through hole 51h, a step portion 51g, and a recess 51r. Such a first portion 511 can be fabricated by processing a plate-shaped metal sheet. The through hole 51h can be formed, for example, by punching using a conventionally known stripper. The step portion 51g and the recess 51r can be formed, for example, by conventionally known press processing. More specifically, for example, the step portion 51g and the recess 51r can be formed by preparing a mold having protrusions corresponding to the step portion 51g and the recess 51r, clamping the metal sheet between the mold, and plastically deforming the metal sheet using a press. The negative electrode current collector 60 can be fabricated in a similar manner.

[0070] In the assembling process (step S2), the positive electrode terminal 30, the positive electrode current collector 50, the negative electrode terminal 40, and the negative electrode current collector 60 are each assembled to the sealing plate 14, typically while being insulated from the sealing plate 14. The positive electrode terminal 30 and the positive electrode current collector 50 are assembled by, for example, placing the flange portion 30f of the positive electrode terminal 30 on the outer surface of the sealing plate 14 with a gasket 90 interposed therebetween, and placing the positive electrode current collector 50 on the inner surface of the sealing plate 14 with a resin member 70 interposed therebetween, as shown in FIG. Specifically, the components are assembled by inserting the shaft portion 30a of the positive terminal 30 before crimping through the cylindrical portion 90a of the gasket 90, the terminal lead-out hole 18 of the sealing plate 14, the through-hole 70h of the resin member 70, and the through-hole 51h of the first portion 511 of the positive current collector 50, in that order, so that the shaft portion 30a protrudes downward below the lower surface 51d of the through-hole 51h. The negative terminal 40 and the negative current collector 60 are similarly assembled to the sealing plate 14.

[0071] In the crimping process (step S3), one end of the shaft portion 30a of the positive electrode terminal 30 attached to the sealing plate 14 is deformed by crimping (riveting) to form the crimped portion 30c. Specifically, for example, the lower surface 51d of the first portion 511 is placed on a fixed die, and a compression punch is used to apply a compressive force in the vertical direction Z to the shaft portion 30a from above the flange portion 30f of the positive electrode terminal 30. As a result, the tip portion of the shaft portion 30a that protrudes downward from the lower surface 51d of the first portion 511 is pressed against the inner surface of the through-hole 51h of the positive electrode current collector 50, specifically, against the side surface 51s of the stepped portion 51g. As a result, the material at the tip portion of the shaft portion 30a moves upward along the stepped portion 51g. As a result, the tip portion of the shaft portion 30a is pushed and spread so as to enter the stepped portion 51g, forming the crimped portion 30c. This crimping process fixes the positive electrode terminal 30 and the positive electrode current collecting part 50 to the sealing plate 14 and seals the terminal pull-out hole 18. Similarly, a crimping part 40c can be formed on the negative electrode terminal 40, so that the negative electrode terminal 40 and the negative electrode current collecting part 60 can be fixed to the sealing plate 14.

[0072] In this embodiment, since the recess 51r is formed in the current collecting part preparation step (step S1), even if the amount of material from the tip of the shank 30a that flows into the step 51g varies greatly due to, for example, variations in the processing accuracy of the shank 30a, the material from the tip of the shank 30a does not completely fill the recess 51r, preventing blockage of the gap S between the positive terminal 30 and the positive current collecting part 50. Therefore, a stable air escape route can be ensured in the welding joining step (step S4) described below.

[0073] In the welding and joining step (step S4), the crimped portion 30c is welded to the periphery of the through hole 51h of the positive current collector 50. The welding is preferably performed along the crimping line. This forms a welded joint J at the boundary between the positive terminal 30 and the positive current collector 50. The welded joint J is preferably formed around the entire periphery of the through hole 51h (annular). The welded joint J can be formed by a conventionally known welding method, such as laser welding, electron beam welding, ultrasonic welding, resistance welding, or TIG (Tungsten Inert Gas) welding. This improves electrical conductivity reliability. Note that the crimped portion 40c can also be welded to the periphery of the through hole of the negative current collector 60, thereby forming a welded joint J at the boundary between the negative terminal 40 and the negative current collector 60.

[0074] Although not particularly limited, when laser welding is employed, the following conditions can be used in some embodiments. Laser oscillator: Trumpf Laser output: 3300W Laser core diameter: 200 μm Laser spot diameter: 460 μm Optical magnification: 2.3x Focus: Just focus Scanning method: Galvano Scanning speed: 550mm / s Assist gas (N2 gas): 50L / min

[0075] In this embodiment, in the welding and joining process, no crimped portion 30c is formed near the portion where the welded joint J is formed, for example, near the outer peripheral edge of the bottom surface 51b of the stepped portion 51g, and a gap S is secured. This allows gas generated during welding to escape into the gap S, preventing gas from accumulating at the welded joint J. This significantly improves the robustness of the welding quality in the production process and prevents welding defects from occurring. Consequently, a high-strength welded joint J can be stably formed, improving electrical conductivity reliability. It is preferable that the gap S be secured continuously around the entire circumference of the through hole 51h.

[0076] <Method of manufacturing an electricity storage device> The electricity storage device 100 can be manufactured, for example, by preparing the sealing plate assembly, the electrode group 20, the non-aqueous electrolyte, and the case body 12 as described above, and by a manufacturing method including an attachment process and a construction process.

[0077] In the attachment step, the electrode body group 20 is attached to the sealing plate 14 to produce a combination (sealing plate assembly) of the sealing plate 14 and electrode body group 20 as shown in FIG. 3. Specifically, a positive electrode second current collecting portion 52 is attached to each of the positive electrode tab groups 23 of the electrode bodies 20a, 20b, and 20c, and the positive electrode second current collecting portion 52 is joined (e.g., welded) to the positive electrode first current collecting portion 51 of the sealing plate assembly. This electrically connects the positive electrodes 22 of the electrode bodies 20a, 20b, and 20c to the positive electrode terminal 30. Similarly, a negative electrode second current collecting portion 62 is attached to each of the negative electrode tab groups 25 of the electrode bodies 20a, 20b, and 20c, and the negative electrode second current collecting portion 62 is joined (e.g., welded) to the negative electrode first current collecting portion 61 of the sealing plate assembly. As a result, the negative electrodes 24 of the electrode bodies 20a, 20b, 20c are electrically connected to the negative electrode terminal 40. As a result, the sealing plate assembly and the electrode body group 20 are integrated together.

[0078] In the construction step, as shown in FIGS. 1 and 2, the electrode assembly 20 integrated with the sealing plate 14 is housed in the internal space of the case body 12, and the case body 12 and the sealing plate 14 are sealed together. Sealing can be performed by welding, for example, laser welding. Thereafter, a nonaqueous electrolyte is injected through the liquid injection hole 15 in the sealing plate 14, and the liquid injection hole 15 is closed with a sealing member 16, thereby sealing the electricity storage device 100. In this manner, the electricity storage device 100 can be manufactured.

[0079] <Applications of electricity storage devices> The power storage device 100 can also be suitably used as an assembled battery in which a plurality of power storage devices 100 are electrically connected to one another via a bus bar. In this case, the plurality of power storage devices 100 can be electrically connected by, for example, bridging a conductive member such as a bus bar between the positive electrode terminals 30 and negative electrode terminals 40 of adjacent power storage devices 100. The power storage device 100 can be used for a variety of purposes, but is suitably used in applications requiring high bonding strength, such as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car or truck. The type of vehicle is not particularly limited, and examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

[0080] 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.

[0081] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: A battery device comprising an electrode body having an electrode, a case body having an opening and accommodating the electrode body, a sealing plate having a terminal lead-out hole and sealing the opening of the case body, a current collecting part electrically connected to the electrode inside the case body and having a through-hole, a shaft part inserted through the terminal lead-out hole and the through-hole, a caulking part provided at one end of the shaft part on the case body side and caulked to the periphery of the through-hole, a step part provided on the side surface of the through-hole of the current collecting part and at least a part of the caulking part of the terminal being disposed thereon, and a welded joint part between the peripheral part of the through-hole of the current collecting part and the caulking part of the terminal, wherein a gap is provided between the current collecting part and the terminal in the vicinity of the welded joint part. Item 2: The battery device according to Item 1, wherein the welded joint part is provided in an annular shape, and the gap is provided continuously in the circumferential direction along the annular welded joint part. Item 3: The battery device according to Item 1 or Item 2, wherein the gap is provided in the vicinity of the outer peripheral edge of the bottom surface of the step part. Item 4: The battery device according to any one of Items 1 to 3, wherein the current collecting part has a recess in the vicinity of the outer peripheral edge of the bottom surface of the step part. Item 5: The battery device according to Item 4, wherein the ratio (D2 / D1) of the depth D2 of the recess to the depth D1 of the step part is 1 / 10 or more. Item 6: The battery device according to any one of Items 1 to 5, wherein the depth D3 of the welded joint part is smaller than the depth D1 of the step part (D3 < D1). Item 7: The battery device according to any one of Items 1 to 6, wherein the current collecting part is made of aluminum or an aluminum alloy. <​​Item 9: An electrode body having an electrode, a case body having an opening and accommodating the electrode body, a sealing plate having a terminal pull-out hole and sealing the opening of the case body, a current collector part electrically connected to the electrode inside the case body and having a through hole, a shaft part inserted through the terminal pull-out hole and the through hole, a crimping part provided at one end of the shaft part on the case body side and crimped to a periphery of the through hole, a step part provided on a side surface of the through hole of the current collector and at least a part of the crimping part of the terminal is disposed, and a welding connection between the periphery of the through hole of the current collector and the crimping part of the terminal. and a joint portion, the method comprising: an assembling step of inserting the shank portion of the terminal into the terminal pull-out hole of the sealing plate and the through hole of the current collector to assemble the terminal, the sealing plate, and the current collector; a crimping step of deforming one end of the shank portion of the terminal to form the crimped portion after the assembling step; and a welding joining step of welding the crimped portion to a periphery of the through hole of the current collector to form the welded joint after the crimping step, wherein in the welding joining step, a gap is provided between the current collector and the terminal near the welded joint. [Explanation of symbols]

[0082] 10 Battery case 12 Case body 14 Sealing plate 18, 19 Terminal extraction hole 20a, 20b, 20c electrode body 22 Positive electrode 24 negative electrode 30 Positive terminal (terminal) 30a Shaft 30c Crimping part 40 Negative terminal (terminal) 50 Positive electrode current collector (current collector) 511 Part 1 51g step 51h through hole 51r recess 60 Negative electrode current collector (current collector) 100 Energy storage device J Welded joint S void

Claims

1. an electrode body having electrodes; a case body having an opening and accommodating the electrode body; a sealing plate having a terminal lead-out hole and sealing the opening of the case body; a current collecting portion electrically connected to the electrode inside the case body and having a through hole; a terminal having a shaft portion that is inserted through the terminal lead-out hole and the through hole, and a crimping portion that is provided at one end of the shaft portion on the case body side and is crimped to a periphery of the through hole; a step portion provided on a side surface of the through hole of the current collecting portion, on which at least a part of the crimping portion of the terminal is disposed; a welded joint between a peripheral portion of the through hole of the current collecting portion and the crimped portion of the terminal; Equipped with the current collecting portion has a recess in a range from an outer peripheral edge of a bottom surface of the step portion to within ½ of the width of the bottom surface, a gap is provided between the current collecting portion and the terminal so as to include the recess and to be in contact with the welded joint; Energy storage device.

2. the weld joint is annular; and The gap is provided continuously in a circumferential direction along the annular welded joint. The electricity storage device according to claim 1 .

3. The gap is provided at least within a range of ½ of the width of the bottom surface from the outer periphery of the bottom surface of the step portion. The electricity storage device according to claim 1 or 2.

4. The welded joint is provided over a portion of the side surface of the stepped portion. The electricity storage device according to claim 1 or 2.

5. a ratio (D2 / D1) of a depth D2 to a bottom surface of the recess to a depth D1 to a bottom surface of the step portion is 1 / 10 or more; The electricity storage device according to claim 1 or 2.

6. a depth D3 of the welded joint to the bottom surface is smaller than a depth D1 of the stepped portion to the bottom surface (D3<D1); The electricity storage device according to claim 1 or 2.

7. The current collecting portion is made of aluminum or an aluminum alloy. The electricity storage device according to claim 1 or 2.

8. The terminal is made of aluminum or an aluminum alloy. The electricity storage device according to claim 1 or 2.

9. a terminal having a shaft portion that passes through the terminal pull-out hole and the through hole, and a crimping portion that is provided at one end of the shaft portion on the case body side and is crimped to a periphery of the through hole; a step portion that is provided on a side surface of the through hole in the current collector portion and at which at least a part of the crimping portion of the terminal is disposed; and a welded joint between a periphery of the through hole in the current collector portion and the crimping portion of the terminal, an assembling process of inserting the shaft portion of the terminal into the terminal pull-out hole of the sealing plate and the through-hole of the current collecting portion to assemble the terminal, the sealing plate, and the current collecting portion together; a crimping step of deforming one end of the shank of the terminal to form the crimped portion after the assembling step; a welding and joining step of welding the crimped portion to a periphery of the through hole of the current collecting portion after the crimping step to form the welded joint; and the current collecting portion has a recess in a range from an outer peripheral edge of a bottom surface of the step portion to within ½ of the width of the bottom surface, In the welding and joining step, a gap is provided between the current collecting portion and the terminal so as to include the recess and to be in contact with the welding joint portion. A method for manufacturing an electricity storage device.

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