Method for manufacturing an electricity storage device

Abstract

To provide a technique capable of suppressing thermal effect capable of being generated in laser welding.SOLUTION: A method for manufacturing a power storage device includes: preparing a bottomed case body 12 having an opening 12h, a sealing plate 14 mounted with a resin member, and an electrode body 20; storing the electrode body 20 inside the case body 12, and mounting the sealing plate 14 on the opening 12h of the case body 12; providing a shielding part between the resin member and a peripheral edge part 14c of the sealing plate 14, on an outer surface 14a of the sealing plate 14; and emitting a laser beam LA along the peripheral edge part 14c of the sealing plate 14, and laser welding the case body 12 and the sealing plate 14, in a state where the shielding part is provided. The method further includes: supplying assist gas AG containing non-oxidative gas and oxidative gas to at least the peripheral edge part 14c of the sealing plate 14 around the shielding part, and emitting the lase beam LA to a part to which the assist gas AG is supplied.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] Conventionally, there has been known an electric storage device including an electrode assembly, a case body that houses the electrode assembly, and a sealing body that seals the opening of the case body. The case body and sealing plate are sealed by welding, for example, using laser welding or the like. For example, Japanese Patent Application Laid-Open Publication No. 2013-54964 discloses a battery in which a shielding portion is provided between the seam (laser-welded portion) between the case body and the sealing plate and a resin member that separates the outer surface of the sealing plate from the terminals. This technology is said to suppress discoloration of the resin member (burning, scorching, etc. due to light) caused by, for example, reflected laser light from laser welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-54964 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even when a shielding portion is provided around the resin member, the shielding portion may become blackened and dirty. When the shielding portion becomes blackened, the heat of laser welding is more likely to be absorbed by the shielding portion, and the heat transfer may also affect the resin member.

[0005] Therefore, a main object of the present disclosure is to provide a technology that can suppress the thermal effects that can occur during laser welding. [Means for solving the problem]

[0006] One aspect of the technology disclosed herein is a method for manufacturing an electricity storage device, the method including: preparing a bottomed case body having an opening, a sealing plate to which a resin member is attached, and an electrode assembly; housing the electrode assembly inside the case body and attaching the sealing plate to the opening of the case body; providing a shielding portion on the outer surface of the sealing plate between the resin member and a peripheral portion of the sealing plate; and, with the shielding portion provided, irradiating a laser beam along the peripheral portion of the sealing plate to laser-weld the case body and the sealing plate. The method further includes supplying an assist gas containing a non-oxidizing gas and an oxidizing gas to at least the peripheral portion of the sealing plate around the shielding portion, and irradiating the laser beam to the portion to which the assist gas is supplied.

[0007] With this configuration, because an assist gas containing an oxidizing gas is used, the black color of the deposit on the shielding portion caused by laser welding is lighter than when a non-oxidizing gas is used. This makes it difficult for the reflected light of the laser beam LA to be absorbed by the deposit AD, preventing the deposit and the shielding portion from becoming too hot. As a result, the thermal impact on the resin member in contact with or adjacent to the shielding portion can be reduced. [Brief explanation of the drawings]

[0008] [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 plan view of FIG. [Figure 5] FIG. 5 is a flowchart illustrating a method for manufacturing an electricity storage device according to one embodiment. [Figure 6] FIG. 6 is a schematic perspective view for explaining the shielding step S30. [Figure 7] FIG. 7 is a schematic plan view for explaining the shielding step S30. [Figure 8] FIG. 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. 7 for illustrating the welding step S40. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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 an electricity storage device (e.g., a liquid injection process, a charging process, etc.) that do not characterize the technology disclosed herein) can be understood as design matters for a person skilled in the art based on prior art 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 illustration, and dimensional relationships (e.g., length, width, thickness, etc.) 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.

[0010] In this specification, when a numerical range is described as "A to B (where A and B are any numerical values)," it means "A or more and B or less," and also encompasses the meanings of "greater than A and less than B," "greater than A and B or less," and "greater than A and less than B."

[0011] In this specification, the term "electricity storage device" refers to a device in which charge and discharge reactions occur by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. Such electricity storage devices may include secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries; and capacitors (physical batteries) such as lithium-ion capacitors and electric double-layer capacitors. Hereinafter, a lithium ion secondary battery will be described as an example of a preferred embodiment of the power storage device disclosed herein, but it is not intended that the application be limited to such batteries.

[0012] FIG. 1 is a perspective view of a secondary battery 100 according to this embodiment. FIG. 2 is a diagram schematically illustrating the internal structure of the secondary battery 100. In the drawings, the symbols L, R, F, Rr, U, and D represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z represent the short side direction, long side direction perpendicular to the short side direction, and up and down direction of the secondary battery 100, respectively. However, these directions are merely used for convenience of explanation and do not limit the installation form of the secondary battery 100 in any way. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not necessarily reflect the actual dimensional relationships.

[0013] <Secondary battery> As shown in FIGS. 1 and 2, the secondary battery 100 includes an electrode assembly 20, an electrolyte (not shown), a case 10 that accommodates the electrode assembly 20 and the electrolyte, a positive electrode terminal 30, and a negative electrode terminal 40.

[0014] FIG. 3 is a schematic diagram illustrating the configuration of an 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 longitudinally 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. As shown in FIG. 2, the electrode assembly 20 has a so-called horizontal tab structure in which a positive electrode tab group 23 and a negative electrode tab group 25 are located on the left and right sides of the electrode assembly 20. However, the electrode assembly may also have a so-called upper tab structure in which a positive electrode tab group and a negative electrode tab group are located on the upper side of the electrode assembly.

[0015] As shown in Fig. 3, the positive electrode sheet 22 is a long, strip-shaped member. The configuration of the positive electrode sheet 22 is not particularly limited and may be the same as that used in conventionally known batteries. For example, the positive electrode sheet 22 has a positive electrode current collector 22c and a positive electrode active material layer 22a fixed to at least one surface of the positive electrode current collector 22c. The positive electrode sheet 22 may also have a positive electrode protective layer (not shown) configured to have lower electrical conductivity than the positive electrode active material layer 22a.

[0016] The positive electrode current collector 22c is a long, strip-shaped member. 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. The dimensions of the positive electrode current collector 22c are not particularly limited and may be determined appropriately depending on the battery design. A plurality of 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 current collector 22c. The positive electrode tabs 22t are part of the positive electrode current collector 22c and are made of a metal foil (e.g., aluminum foil). A positive electrode active material layer 22a is formed on a portion of the positive electrode tab 22t. At least a portion of the positive electrode tab 22t does not have the positive electrode active material layer 22a formed thereon, and the positive electrode current collector 22c is exposed. The 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 positive electrode tabs 22t are bent and curved so that their outer ends are aligned. The positive electrode tab group 23 is connected to the positive electrode terminal 30 via a positive electrode current collector 50.

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

[0018] As shown in Fig. 3, the 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 current collector 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode current collector 24c.

[0019] 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. The dimensions of the negative electrode current collector 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 current collector 24c. The negative electrode tab 24t is part of the negative electrode current collector 24c and is made of a metal foil (e.g., copper foil). The negative electrode active material layer 24a is formed on part of the negative electrode tab 24t. At least part of the negative electrode tab 24t does not have the negative electrode active material layer 24a formed thereon, exposing the negative electrode current collector 24c. The multiple negative electrode tabs 24t are stacked at one end (the right end in FIG. 2 ) in the long side direction Y to form a negative electrode tab group 25. The negative electrode tabs 24t are bent and curved so that their outer ends are aligned. The negative electrode tab group 25 is connected to the negative electrode terminal 40 via the negative electrode current collecting portion 60.

[0020] 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 current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material. The negative electrode active material is not particularly limited, but carbon materials such as graphite, hard carbon, and soft carbon can be used. The graphite may be natural graphite or artificial graphite, or may be amorphous carbon-coated graphite in which graphite is coated with an amorphous carbon material. The negative electrode active material layer 24a can contain components other than the negative electrode active material, such as a binder or a thickener. Examples of binders that can be used include styrene butadiene rubber (SBR) and polyvinylidene fluoride (PVDF). Examples of thickeners that can be used include carboxymethyl cellulose (CMC).

[0021] 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.

[0022] As described above, the secondary battery 100 includes an electrolyte solution. The electrolyte solution is not particularly limited and may be the same as that used in conventionally known batteries. The electrolyte solution may be, for example, a non-aqueous electrolyte solution containing a non-aqueous solvent (organic solvent) and an electrolyte salt (supporting salt). Examples of the non-aqueous solvent 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 electrolyte solution may contain various additives such as a film-forming agent, a gas generating agent, a dispersant, and a thickener.

[0023] As shown in FIGS. 1 and 2, the case 10 includes a case body 12 and a sealing plate 14. A positive electrode terminal 30 and a negative electrode terminal 40 are attached to the sealing plate 14. The positive electrode terminal 30 is attached to one end of the sealing plate 14 in the long side direction Y (the left end in FIGS. 1 and 2). The negative electrode terminal 40 is attached to the other end of the sealing plate 14 in the long side direction Y (the right end in FIGS. 1 and 2). The positive electrode terminal 30 and the negative electrode terminal 40 are inserted through terminal mounting holes 18 and 19 and extend from the outer surface 14a of the sealing plate 14 toward the inner surface 14b. The lower end of the positive electrode terminal 30 is connected to a positive electrode current collector 50 inside the case body 12. The positive electrode terminal 30 is connected to the positive electrode sheet 22 of the electrode assembly 20 via the positive electrode current collector 50. The lower end of the negative electrode terminal 40 is connected to a negative electrode current collector 60 inside the case body 12. The negative electrode terminal 40 is connected to the negative electrode sheet 24 of the electrode body 20 via the negative electrode current collector 60.

[0024] The positive electrode terminal 30 is preferably made of a metal, more preferably aluminum or an aluminum alloy, for example. The negative electrode terminal 40 is preferably made of a metal, more preferably copper or a copper alloy, for example. As shown in FIG. 1 , the positive electrode terminal 30 and the negative electrode terminal 40 are electrically connected to a plate-shaped external conductive member 35 on the outside of the case 10. The external conductive member 35 is a member to which a bus bar is attached when electrically connecting multiple secondary batteries to each other. The external conductive member 35 is preferably made of a metal, more preferably aluminum or an aluminum alloy, for example. However, the external conductive member 35 is not essential and may be omitted in other embodiments.

[0025] As shown in FIGS. 1 and 2 , the positive electrode terminal 30 and the negative electrode terminal 40 are each insulated from the sealing plate 14 by a resin member 70. In this embodiment, the resin member 70 includes a gasket 72 and an external insulating member 74. The gasket 72 is attached to the positive electrode terminal 30 and the negative electrode terminal 40. The gasket 72 is disposed between the outer surface 14a of the sealing plate 14 and the positive electrode terminal 30 or the negative electrode terminal 40. The gasket 72 is also disposed in the terminal attachment holes 18 and 19 of the sealing plate 14 between the positive electrode terminal 30 and the negative electrode terminal 40 and the sealing plate 14. This insulates the positive electrode terminal 30 and the negative electrode terminal 40 from the sealing plate 14. The external insulating member 74 is disposed between the external conductive member 35 and the outer surface of the sealing plate 14, and insulates the external conductive member 35 from the sealing plate 14. The resin member 70 may be made of a fluorine-based resin such as perfluoroalkoxyalkane (PFA) or polytetrafluoroethylene (PTFE), or a synthetic resin material such as polyphenylene sulfide (PPS) or polyphenylene ether (PPE). In an embodiment that does not include the external conductive member 35, the external insulating member 74 may also be omitted.

[0026] As shown in FIG. 1, case 10 has a rectangular parallelepiped (square) shape with a bottom. Any conventionally known material can be used for case 10 without any particular restrictions. Case 10 (case body 12 and sealing plate 14) can be made of, for example, aluminum, aluminum alloy, stainless steel, iron, iron alloy, etc. Among these, it is preferable that case 10 be made of aluminum.

[0027] The case body 12 is a housing that houses the electrode assembly 20 and the nonaqueous electrolyte. The case body 12 is a bottomed, rectangular container having an opening 12h on one side (here, the top). Here, the opening 12h is substantially rectangular. The case body 12 has long and short sides and includes a bottom surface 12a that is substantially rectangular in plan view, a pair of long side walls 12b that extend upward in the vertical direction Z from the long side of the bottom surface 12a and face each other, and a pair of short side walls 12c that extend upward in the vertical direction Z from the short side of the bottom surface 12a and face each other. The area of ​​the short side walls 12c is smaller than the area of ​​the long side walls 12b. While not particularly limited, the average thickness (average plate thickness) of the case body 12 is preferably approximately 0.5 mm or more, for example 1 mm or more, from the viewpoint of durability, etc., and may be approximately 5 mm or less, for example 3 mm or less, from the viewpoint of cost and energy density.

[0028] The sealing plate 14 has a generally rectangular shape in plan view and is a member that seals the opening 12h of the case body 12. The sealing plate 14 has an inner surface 14b (see FIG. 2 ), which is the surface facing the inside of the secondary battery 100 (the side facing the electrode body 20), and an outer surface 14a (see FIG. 2 ), which is the surface facing the outside. As shown in FIG. 1 , the sealing plate 14 faces the bottom surface 12a of the case body 12. The sealing plate 14 is provided with a liquid inlet 15 and a gas release valve 17. The liquid inlet 15 is a through-hole for injecting electrolyte into the 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 case 10 reaches or exceeds a predetermined value, thereby releasing gas inside the case 10 to the outside. Although not particularly limited, the average thickness (average plate thickness) of the 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 may be approximately 5 mm or less, for example 3 mm or less, or 2.5 mm or less, from the viewpoint of cost and energy density.

[0029] FIG. 4 is a plan view of FIG. 1. As shown in FIG. 4, peripheral edge 14c of sealing plate 14 and peripheral edge 12d of opening 12h of case body 12 are welded together, forming weld 10w along the boundary between case body 12 and sealing plate 14. This weld can be achieved, for example, by laser welding. Weld 10w is formed by laser welding the boundary between case body 12 and sealing plate 14, melting the constituent metals of case body 12 and sealing plate 14. Here, weld 10w is located on the outer surface 14a side of sealing plate 14. Weld 10w preferably connects the inner peripheral edge of opening 12h of case body 12 and peripheral edge 14c of sealing plate 14 so that they are flush with each other. In plan view, weld 10w is formed in a substantially annular, continuous shape along the boundary between sealing plate 14 and case body 12.

[0030] <Secondary battery manufacturing method> 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.

[0031] Fig. 5 is a flowchart outlining a method for manufacturing an electricity storage device according to one embodiment. Fig. 6 is a schematic perspective view illustrating the shielding step S30. Fig. 7 is a schematic plan view illustrating the shielding step S30. Fig. 8 is a schematic cross-sectional view taken along line VIII-VIII in Fig. 7 illustrating the welding step S40. This embodiment may include a preparation step S10 for preparing the case body 12, the sealing plate 14 to which the resin member 70 has been attached, and the electrode body 20, as described above; an assembly step S20 for assembling the electricity storage device by attaching the sealing plate 14 to the case body 12; a shielding step S30 for providing a shielding portion on the outer surface 14a of the sealing plate 14 between the resin member 70 and a peripheral edge 14c of the sealing plate 14; and a welding step S40 for irradiating the peripheral edge 14c of the sealing plate 14 with laser light LA ​​to laser-weld the case body 12 and the sealing plate 14 together. In the welding step S40, it is preferable to use an assist gas containing a non-oxidizing gas and an oxidizing gas. The manufacturing method disclosed herein may further include other steps at any stage, and steps may be omitted or their order may be changed as needed. For example, the shielding step S30 may be performed at any time before the welding step S40. For example, the shielding step S30 may be performed in parallel with the preparation step S10 or before the assembly step S20.

[0032] Laser welding of the case body and the sealing plate is typically performed while supplying a non-oxidizing gas (e.g., an inert gas atmosphere such as nitrogen or argon) to the weld. This is partly because the metals (e.g., aluminum) that make up the case body and the sealing plate are highly reactive with oxygen, which can lead to poor weldability when laser welding is performed in an oxidizing atmosphere. However, even when a non-oxidizing gas is supplied to the weld, the resulting plume can interfere with components (e.g., resin components) near the weld, resulting in the formation of black deposits on those components. Black deposits tend to absorb reflected laser light and become hot. Therefore, the component with the black deposits and other components in contact with them tend to be susceptible to thermal effects. Therefore, in one embodiment of the manufacturing method disclosed herein, a shielding member 200 is positioned as a shielding member between the peripheral edge 14c of the sealing plate 14 to be laser-welded and the component (e.g., resin component) attached to the sealing plate 14 (see FIG. 7). This reduces the interference of the plume PL generated by laser welding with the shielding member 200 and the components attached to the sealing plate 14 with the plume. In one embodiment of the manufacturing method disclosed herein, an assist gas AG containing a non-oxidizing gas and an oxidizing gas is supplied to the peripheral edge 14c of the sealing plate 14 around the shielding member 200 (see FIG. 8). The inventors' investigations have revealed that the black color of the deposit AD on the shielding member 200 produced when the assist gas AG is supplied is lighter (preferably, almost no black) than the black deposit produced when a non-oxidizing gas is supplied. The lighter black color of the deposit AD reduces the absorption of the reflected light of the laser beam LA by the deposit AD. This reduces the thermal impact on a resin component (external insulating component 74 in FIG. 8) in contact with or adjacent to the shielding member 200.

[0033] In the preparation step S10, the case body 12, the sealing plate 14, and the electrode assembly 20 are prepared as described above. 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 laminated so that they are insulated by two strip-shaped separators 26. At this time, the positive electrode tab 22t of the positive electrode sheet 22 and the negative electrode tab 24t of the negative electrode sheet 24 are overlapped so that they protrude in opposite directions from the ends of the two separators 26 in the long side direction Y. Next, the prepared laminate is wound in the longitudinal direction around the winding axis. The winding of the laminate can be performed according to a known method. The wound laminate is pressed to produce a flat wound electrode assembly. This pressing process may be carried out using any known pressing device that is used in the manufacture of general flat wound electrode bodies, and is not particularly limited. In this manner, the electrode body 20 can be prepared.

[0034] In the preparation step S10, for example, a gasket 72, which is an example of the resin member 70, is attached to the sealing plate 14 using a known method. For example, the gasket 72 is attached to the positive terminal 30 and inserted into the terminal attachment hole 18 of the sealing plate 14. When the positive terminal 30 is attached to the sealing plate 14, the gasket 72 is also attached to the sealing plate 14. The method of attachment is not particularly limited. For example, the lower end of the positive terminal 30, which is located inside the case body 12, is crimped to the sealing plate 14 via the gasket 72, thereby attaching the positive terminal 30 and the gasket 72 to the sealing plate 14. At this time, at least a portion of the gasket 72 is exposed on the outer surface 14a of the sealing plate 14. Furthermore, in the secondary battery 100 described above, an external conductive member 35 and an external insulating member 74, which is an example of the resin member 70, are attached to the outer surface 14a of the sealing plate 14. In this case, the external insulating member 74 is disposed as a resin member adjacent to the peripheral edge portion 14c of the sealing plate 14. Note that the attachment of the external insulating member 74 and the external conductive member 35 to the sealing plate 14 may be performed after the assembly step S20 described below. Similarly to the positive electrode terminal 30 described above, the gasket 72, the external insulating member 74, and the external conductive member 35 can also be attached to the sealing plate 14 on the negative electrode terminal 40 side.

[0035] In another embodiment, when the external insulating member 74 is not provided, the gasket 72 may be, for example, a resin member that is close to the peripheral edge portion 14c of the sealing plate 14. In another embodiment, the electrode terminal, the sealing plate 14, and the resin member 70 may be prepared as an integrally molded product.

[0036] In the assembly process S20, the prepared electrode body 20 is housed inside the case body 12, and the sealing plate 14 is attached to the case body 12 to assemble the secondary battery 100. For example, first, the electrode body 20 is attached to the sealing plate 14. The sealing plate 14 and the electrode body 20 are connected via the positive electrode current collector 50 and the negative electrode current collector 60. Next, the electrode body 20 is inserted into the case body 12. At this time, it is preferable to insert the electrode body 20 so that it is disposed inside the case body 12 with the winding axis WL oriented along the bottom surface 12a (i.e., the winding axis WL is oriented parallel to the long side direction Y).

[0037] The sealing plate 14 is attached to the opening 12h of the case body 12. In this embodiment, the outer diameter of the sealing plate 14 is formed to be slightly smaller than the inner diameter of the opening 12h of the case body 12, and the sealing plate 14 is fitted into the opening 12h. At this time, it is preferable that the peripheral edge 14c of the sealing plate 14 contacts the opening peripheral edge 12d of the case body 12.

[0038] In the shielding step S30, a shielding portion is provided on the outer surface 14a of the sealing plate 14 between a component attached to the sealing plate 14 and the peripheral edge 14c of the sealing plate 14. Examples of components attached to the sealing plate 14 include an electrode terminal (positive electrode terminal 30 or negative electrode terminal 40), a resin component 70 (e.g., a gasket 72 or an external insulating component 74), and an external conductive component 35. By providing a shielding portion, the thermal effects of laser welding on the component attached to the sealing plate 14 can be reduced and the component can be protected. In a preferred embodiment, a shielding portion is provided between the resin component 70 attached to the sealing plate 14 and the peripheral edge 14c of the sealing plate 14. This is because the resin component 70 is susceptible to deterioration due to thermal effects. In the following description, the external insulating component 74 is used as an example of a component attached to the sealing plate 14 (a component to be protected by the shielding portion), but the present invention is not limited thereto.

[0039] As shown in FIG. 6 , in this embodiment, a shielding member 200 is prepared as a shielding portion. As shown in FIG. 7 , the shielding member 200 is disposed on the outer surface 14 a of the sealing plate 14, between the external insulating member 74 and the peripheral edge portion 14 c of the sealing plate 14. Here, the shielding member 200 has a through hole 230. The through hole 230 is surrounded by a pair of first side walls 210 facing each other and a pair of second side walls 220 facing each other. The through hole 230 has a size that can surround a member (e.g., a resin member, specifically the external insulating member 74) disposed on the outer surface 14 a of the sealing plate 14. Here, the through hole 230 has a substantially rectangular shape in a plan view. The first side walls 210 are the long sides of the through hole 230, and the second side walls 220 are the short sides of the through hole 230. The first side wall 210 extends in the long side direction Y of the secondary battery 100, and the second side wall 220 is disposed so as to extend in the short side direction X of the secondary battery 100 (see FIG. 7). The first side wall 210 extends along (e.g., parallel to) the peripheral edge 14c of the sealing plate 14 in the long side direction Y of the secondary battery 100. The second side wall 220 extends along (e.g., parallel to) the peripheral edge 14c of the sealing plate 14 in the short side direction X of the secondary battery 100.

[0040] The second side wall 220 includes an outer side wall 222 that is disposed on the edge side of the sealing plate 14, and an inner side wall 224 that is disposed on the center side of the sealing plate 14. The outer side wall 222 is disposed between the peripheral edge portion 14c of the sealing plate 14 and the external insulating member 74. Although the inner side wall 224 can be omitted in other embodiments, providing the shielding member 200 with the inner side wall 224 makes it easier to fix the shielding member 200 to the outer surface 14a of the sealing plate 14.

[0041] It is preferable that the shielding member 200 is disposed so that at least a portion thereof contacts the external insulating member 74. For example, it is preferable that the first side wall 210 is disposed so as to sandwich the external insulating member 74. This allows the shielding member 200 to be fixed to the external insulating member 74, and the shielding member 200 to be disposed with good stability.

[0042] As shown in FIG. 8, the height H1 of the shielding member 200 (in FIG. 8, the first side wall 210 is shown as an example) is preferably higher than the height H2 (for example, the height of the end portion on the shielding member 200 side) of the external insulating member 74 from the outer surface 14a of the sealing plate 14. This makes it easier to prevent the plume PL generated by laser welding from interfering with the external insulating member 74. Furthermore, since it is possible to prevent the reflected light of the laser light LA ​​from being irradiated onto the external insulating member 74, it is possible to reduce the thermal effects.

[0043] The shielding member 200 is preferably configured to be detachable from the sealing plate 14. Preferably, after laser welding, the shielding member 200 is removed from the outer surface 14a of the sealing plate 14. This also removes any adhering matter AD on the shielding member 200, improving aesthetics. Furthermore, the shielding member 200 can be reused repeatedly, reducing costs.

[0044] The shielding member 200 can be made of, for example, metal, resin, etc., but is preferably made of metal from the viewpoint of heat resistance. Examples of metal that can be used include stainless steel and aluminum. Furthermore, the surface of the shielding member 200 facing the laser welded portion is preferably plated, and plating (mirror finishing) that improves the reflectivity of the surface of the shielding member 200 to the laser light LA ​​is preferable. This makes it difficult for the reflected light of the laser light LA ​​to be absorbed by the shielding member 200, thereby reducing the thermal effects. Examples of such plating include silver plating and chrome plating.

[0045] In the welding step S40, with the shielding portion in place, laser light LA ​​is applied along peripheral portion 14c of sealing plate 14 to laser-weld case body 12 and sealing plate 14. As a result, welded portion 10w is formed at the boundary between case body 12 and sealing plate 14, and case 10 is hermetically sealed.

[0046] An assist gas AG is preferably supplied to the portion (peripheral edge portion 14c of sealing plate 14) around the shielding portion (here, shielding member 200) that is irradiated with the laser light LA. The assist gas AG contains a non-oxidizing gas and an oxidizing gas. The assist gas AG may be a mixed gas in which a non-oxidizing gas and an oxidizing gas are pre-mixed. Alternatively, the non-oxidizing gas and the oxidizing gas may be supplied to the portion that is irradiated with the laser light LA ​​from separate supply ports.

[0047] In this specification, the "periphery of the sealing plate around the shielding portion" refers to the portion of the peripheral portion of the sealing plate where the shielding portion exists in a direction perpendicular to a tangent to the peripheral portion (or to the straight line in the case of a straight portion of the peripheral portion) in a plan view.

[0048] The direction in which the assist gas AG is supplied is not particularly limited, but for example, as shown in FIG. 8, the assist gas AG can be supplied from the side wall of the case body 12 toward the shielding portion (shielding member 200). This allows the assist gas AG to hit the shielding member 200, making the black color of the deposit AD lighter. Alternatively, for example, the assist gas AG may be flowed toward the outer surface 14a of the sealing plate 14. Furthermore, for example, the assist gas AG may be flowed in a direction along the peripheral edge portion 14c of the sealing plate 14. In this specification, "supplying assist gas AG to the part irradiated with laser light LA" may include not only a state in which assist gas AG directly hits the part irradiated with laser light LA, but also a state in which assist gas AG is supplied to the surrounding area (for example, the area above the part irradiated with laser light LA).

[0049] When laser welding the sealing plate 14 and the case body 12 around the shielding portion (shielding member 200), it is preferable to irradiate the laser beam LA with the assist gas AG supplied. This makes it possible to more reliably lighten the black color of the deposit AD, thereby reducing the thermal effect of the laser beam LA.

[0050] The proportion of oxidizing gas in the assist gas is, for example, 5 vol% or more, preferably 6 vol% or more, 7 vol% or more, or 7.5 vol% or more. The higher this proportion, the lighter the black color of the deposit AD can be. Furthermore, the proportion may be, for example, 10 vol% or less, and may be 9 vol% or less, or 8 vol% or less. If the proportion of oxidizing gas in the assist gas AG is too high, the weldability between the sealing plate 14 and the case body 12 may be reduced.

[0051] The oxidizing gas is preferably oxygen gas, and examples of the non-oxidizing gas include nitrogen gas and argon gas.

[0052] In at least a portion of the area (peripheral edge 14c of sealing plate 14) irradiated with laser light LA ​​at a position away from the shielding portion (shielding member 200), it is preferable to supply a gas with a lower proportion of oxidizing gas than the assist gas AG to the area (peripheral edge 14c of sealing plate 14) irradiated with laser light LA. Furthermore, it is more preferable that such gas be composed of a non-oxidizing gas. This improves the weldability between the sealing plate 14 and the case body 12. Here, the "periphery of the sealing plate at a position away from the shielding portion" may be, for example, a portion other than the "periphery of the sealing plate around the shielding portion" described above.

[0053] There are no limitations on the type of laser beam LA as long as it can weld the case body 12 and the sealing plate 14 together. The laser beam LA may be, for example, a solid-state laser (e.g., a YAG laser, a glass laser, a ruby ​​laser, etc.), a liquid laser (e.g., a dye laser, etc.), a gas laser (e.g., a CO2 laser, etc.), a fiber laser, a disk laser, a semiconductor laser, a free electron laser, a chemical laser, etc. The wavelength of the laser beam LA is preferably, for example, 300 nm to 1100 nm. This allows the case body 12 and the sealing plate 14 to be suitably welded together.

[0054] The laser conditions are not particularly limited as long as they are capable of welding case body 12 and sealing plate 14. The laser output value can be, for example, from 1000 W to 5000 W, and from 1500 W to 3000 W. The laser scanning speed can be, for example, from 100 mm / sec to 300 mm / sec, and from 150 mm / sec to 250 mm / sec.

[0055] <Modification> In the above embodiment, the shielding member 200 includes a pair of first side walls 210 and a pair of second side walls 220, but is not limited to this. For example, in another aspect, the inner side walls 224 of the second side walls 220 of the shielding member 200 may be omitted, and a shielding member that is U-shaped in plan view may be used.

[0056] In another embodiment, the shielding member 200 does not need to have the pair of second side walls 220. For example, in the secondary battery 100, the distance between the short side of the peripheral edge 14c of the sealing plate 14 (the short side at the end of the secondary battery 100 in the long side direction Y) and a member attached to the sealing plate 14 (e.g., the external insulating member 74) is longer than the distance between the long side of the peripheral edge 14c of the sealing plate 14 and a member attached to the sealing plate 14 (e.g., the external insulating member 74). This is because, in such a configuration, laser welding of the short side of the peripheral edge 14c of the sealing plate 14 has relatively little (or no) effect on the member attached to the sealing plate 14.

[0057] In another embodiment, the first side wall 210 and the second side wall 220 of the shielding member 200 may not be formed continuously. In this case, members (for example, plate-shaped members) corresponding to the individual side walls of the shielding member 200 may be prepared and used as the shielding portion.

[0058] In another embodiment, the shielding member 200 does not have to have a through hole 230. For example, the shielding member may be configured in the shape of a box with a bottom and an opening. In this case, the sidewall of such a shielding member may be similar to that of the above-described shielding member 200. Such a box-shaped shielding member may be placed on the outer surface 14a of the sealing plate 14 with the opening facing the outer surface 14a of the sealing plate 14, and a component attached to the sealing plate 14 (a component to be protected by the shielding member) may be placed in the opening.

[0059] In another embodiment, the shielding portion may be a part of the sealing plate 14. For example, a protruding portion that protrudes from the outer surface 14a of the sealing plate 14 may be provided as the shielding portion on the outer surface 14a of the sealing plate 14. Such a protruding portion can be formed, for example, by press working or the like.

[0060] <Battery uses> The above-mentioned battery can be used for various purposes, and can be suitably used, for example, as a power source (driving power source) for motors mounted on vehicles such as passenger cars and trucks. The type of vehicle is not particularly limited, and examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). The battery can also be suitably used in the construction of assembled batteries.

[0061] Although several embodiments of the present technology have been described above, the above embodiments are merely examples. The present technology can be implemented in various other forms. The present technology can be implemented based on the contents disclosed in this specification and the technical common sense 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 can also be deleted as appropriate.

[0062] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A method for manufacturing an electricity storage device, Preparing a case body having an opening and a bottom, a sealing plate to which a resin member is attached, and an electrode body; housing the electrode body inside the case body and attaching the sealing plate to the opening of the case body; providing a shielding portion on the outer surface of the sealing plate between the resin member and the peripheral edge of the sealing plate; and irradiating a laser beam along a peripheral edge of the sealing plate with the shielding portion provided, thereby laser welding the case body and the sealing plate; Including, Here, an assist gas containing a non-oxidizing gas and an oxidizing gas is supplied to at least the peripheral portion of the sealing plate around the shielding portion, and laser light is irradiated to the portion to which the assist gas is supplied. Item 2: The manufacturing method according to Item 1, wherein the ratio of the oxidizing gas in the assist gas is 5 vol % or more. Item 3: The manufacturing method according to Item 1 or 2, wherein the ratio of the oxidizing gas in the assist gas is 10 vol % or less. Item 4: The manufacturing method according to any one of Items 1 to 3, wherein the shielding part is a detachable member. Item 5: The manufacturing method according to Item 4, further comprising removing the shielding portion from the outer surface of the sealing plate after the laser welding. Item 6: The manufacturing method according to any one of items 1 to 5, wherein a gas having a lower proportion of oxidizing gas than the assist gas is supplied to the peripheral portion of the sealing plate at a position away from the shielding portion, and a laser beam is irradiated to the portion to which the gas is supplied. Item 7: The manufacturing method according to item 6, wherein the gas having a lower proportion of oxidizing gas than the assist gas is composed of a non-oxidizing gas. [Explanation of symbols]

[0063] 10 cases 12 Case body 14 Sealing plate 14a Outer surface 14b Inner surface 14c Periphery 20 Electrode body 22 Positive electrode sheet 24 Negative electrode sheet 26 Separator 30 Positive terminal 35 External conductive members 40 Negative terminal 50 Positive electrode current collector 60 Negative electrode current collector 70 Resin parts 72 Gasket 74 External insulating member 100 Secondary battery 200 Shielding member 210 First Side Wall 220 Second side wall

Claims

1. A method for manufacturing an electricity storage device, comprising: Preparing a case body having an opening and a bottom, a sealing plate to which a resin member is attached, and an electrode body; housing the electrode body inside the case body and attaching the sealing plate to the opening of the case body; a shielding portion is provided on the outer surface of the sealing plate between the resin member and a peripheral edge portion of the sealing plate; and irradiating a laser beam along a peripheral edge of the sealing plate with the shielding portion provided, thereby laser welding the case body and the sealing plate; Including, When laser welding the peripheral portion of the sealing plate around the shielding portion, an assist gas containing a non-oxidizing gas and an oxidizing gas is supplied to at least the peripheral portion of the sealing plate around the shielding portion, and a laser beam is irradiated to the portion to which the assist gas is supplied, When laser welding the peripheral edge portion of the sealing plate at a position away from the shielding portion, a gas having a lower ratio of oxidizing gas than the assist gas is supplied to the peripheral edge portion of the sealing plate at a position away from the shielding portion, and a laser beam is irradiated onto the portion to which the gas is supplied. A method for manufacturing an electricity storage device.

2. 2. The method according to claim 1, wherein the assist gas contains an oxidizing gas in an amount of 5 vol % or more.

3. 3. The method according to claim 2, wherein the ratio of the oxidizing gas in the assist gas is 10 vol % or less.

4. A manufacturing method as described in claim 1, wherein the shielding portion is a detachable member.

5. The manufacturing method according to claim 4 , further comprising removing the shielding portion from the outer surface of the sealing plate after the laser welding.

6. The manufacturing method according to claim 1 , wherein the gas having a lower proportion of oxidizing gas than the assist gas is composed of a non-oxidizing gas.

7. A manufacturing method described in any one of claims 1 to 6, wherein the height of the shielding portion is greater than the height of the resin member.

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