Method for manufacturing a power storage device

Abstract

To provide a manufacturing method of a secondary battery which is higher in safety by suppressing incidence of laser light into a battery case.SOLUTION: A manufacturing method of a power storage device includes the steps of: preparing a bottomed case body 12 of which one side face is open, a sealing plate 14 sealing the opening, and an electrode body having a cathode and an anode; assembling the power storage device by accommodating the electrode body inside of the case body 12 and mounting the sealing plate 14 in the opening of the case body 12; and laser-welding the case body 12 and the sealing plate 14 by irradiating a boundary between the case body 12 and the sealing plate 14 with laser light IL from the side of an outer surface of the sealing plate 14. In the manufacturing method, in at least a part of a region in which an opening peripheral edge 12d of the case body 12 is opposed to the sealing plate 14, a light absorption rate of a laser used for a welding step is higher than that in the other portion.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a power storage device.

Background Art

[0002] Conventionally, a power storage device including an electrode body, a case body that houses the electrode body, and a sealing body that seals an opening of the case body has been known. The above-described case body and the sealing plate are welded and sealed by, for example, laser welding. For example, Japanese Patent Application Laid-Open No. 2018-202478 discloses a laser sealing device for such a power storage device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When manufacturing a power storage device, generally, the case body and the sealing plate are separately manufactured and prepared. For this reason, dimensional tolerances occur in each part, and as a result, a slight gap may occur between the case body and the sealing plate. If laser irradiation is performed in the welding process with such a gap present, so-called "laser leakage" may occur, where the laser light directly enters the case through such a gap. Even if the angle of the laser light is adjusted, the laser light may be reflected in the gap between the case body and the sealing plate and enter the case. Alternatively, the relative position and posture between the laser irradiation device and the case, that is, the irradiation angle of the laser light with respect to the laser light irradiation position, may vary due to errors in workpiece mounting and fixing for each manufacturing solid. Therefore, the appropriate irradiation angle of the laser light varies for each manufacturing solid, and it is quite difficult to adjust the irradiation angle every time. If the laser light inadvertently enters the case when the relationship between the relative position and posture of the case and the irradiation angle of the laser light is not appropriate, there is a risk of damaging the contents inside the case (for example, the electrode body housed in the case), which is not preferable. Also, even if the gap is crushed by a clamp or the like, there is a risk of a gap occurring depending on the combination of the case body and the sealing plate (it is difficult to eliminate all the gaps at all welding locations, such as eliminating the gap at one location but leaving a gap at another location). Therefore, there was still room for improvement from the perspective of manufacturing a more safe power storage device.

[0005] The present invention has been made in view of such a point, and an object thereof is to provide a method for manufacturing a secondary battery that suppresses the entry of laser light into the inside of a battery case and is more safe.

Means for Solving the Problems

[0006] The manufacturing method disclosed herein includes a step of preparing a bottomed case body with one side open, a sealing plate for sealing the opening, and an electrode body having a positive electrode and a negative electrode; a step of assembling a power storage device by housing the electrode body inside the case body and attaching the sealing plate to the opening of the case body; and a step of irradiating laser light from the outer surface side of the sealing plate with respect to the boundary between the case body and the sealing plate to laser-weld the case body and the sealing plate. In the manufacturing method disclosed herein, at least a part of the region where the peripheral edge of the opening of the case body and the sealing plate face each other has a higher light absorption rate of the laser used in the welding step than other parts.

[0007] According to such a configuration, laser light is preferably absorbed in the welding step, and it is possible to suppress the entry of laser light into the case from a slight gap between the case body and the sealing plate. Thereby, a power storage device with improved safety can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification and necessary for the implementation of the technology disclosed herein (for example, general configurations and manufacturing processes of power storage devices that do not characterize the technology disclosed herein) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field. Each drawing is schematically drawn, and dimensional relationships (length, width, thickness, etc.) do not necessarily reflect actual dimensional relationships. Also, in the drawings described below, members and parts having the same function are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified.

[0010] In this specification, the "power storage device" refers to a device in which a charge carrier moves between a pair of electrodes (a positive electrode and a negative electrode) through an electrolyte, thereby causing a charge-discharge reaction. Such power storage devices can include secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries; capacitors (physical batteries) such as lithium-ion capacitors and electric double-layer capacitors. Hereinafter, as a preferred embodiment of the power storage device disclosed herein, a lithium-ion secondary battery will be described as an example, but it is not intended to limit the application target to such batteries.

[0011] FIG. 1 is a perspective view of the secondary battery 100 according to this embodiment. FIG. 2 is a diagram schematically showing the internal structure of the secondary battery 100. In the drawings, the reference numerals L, R, F, Rr, U, and D represent left, right, front, rear, top, and bottom, respectively, and the reference numerals X, Y, and Z in the drawings represent the short-side direction, the long-side direction orthogonal to the short-side direction, and the up-down direction of the secondary battery 100, respectively. However, these are merely directions for convenience of explanation and do not limit the installation form of the secondary battery 100 in any way. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not necessarily reflect actual dimensional relationships.

[0012] <Secondary battery> As shown in FIGS. 1 and 2, the secondary battery 100 includes an electrode body 20, an electrolytic solution (not shown), a battery case 10 that houses the electrode body 20 and the electrolytic solution, a positive electrode terminal 30, and a negative electrode terminal 40.

[0013] FIG. 3 is a diagram schematically showing the configuration of the electrode body 20. Here, as shown in FIG. 3, the electrode body 20 is a wound electrode body in which a strip-shaped positive electrode sheet 22 and a strip-shaped negative electrode sheet 24 are laminated in an insulated state via two strip-shaped separators 26 and wound in the longitudinal direction around a winding axis WL. However, the electrode body may be a laminated electrode body 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 body may be a laminated electrode body in which a rectangular positive electrode sheet and a rectangular negative electrode sheet are stacked in an insulated state by a zigzag-folded separator. As shown in FIG. 2, here, the electrode body 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 body 20. However, the electrode body may have a so-called upper tab structure in which a positive electrode tab group and a negative electrode tab group are located above the electrode body.

[0014] The positive electrode sheet 22 is a long strip-shaped member as shown in FIG. 3. 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 on at least one surface of the positive electrode current collector 22c. Note that the positive electrode sheet 22 may have a positive electrode protection layer (not shown) configured to have lower electrical conductivity than the positive electrode active material layer 22a.

[0015] The positive current collector 22c is a long strip-shaped member. The positive current collector 22c is made of a conductive metal such as aluminum, an aluminum alloy, nickel, stainless steel, etc. Here, the positive current collector 22c is a metal foil, specifically an aluminum foil. The dimensions of the positive current collector 22c are not particularly limited and may be appropriately determined according to the battery design. At one end of the positive current collector 22c in the long side direction Y (the left end in FIG. 3), a plurality of positive tabs 22t are provided. The positive tab 22t is a part of the positive current collector 22c and is made of a metal foil (for example, an aluminum foil). A positive active material layer 22a is formed on a part of the positive tab 22t. In at least a part of the positive tab 22t, the positive current collector 22c is exposed without the formation of the positive active material layer 22a. The plurality of positive tabs 22t are laminated at one end in the long side direction Y (the left end in FIG. 2) to form a positive tab group 23. The plurality of positive tabs 22t are bent and curved so that the outer ends are aligned. The positive tab group 23 is connected to the positive terminal 30 via the positive current collecting part 50.

[0016] As shown in FIG. 3, the positive active material layer 22a is provided in a strip shape along the longitudinal direction of the strip-shaped positive current collector 22c. The positive active material layer 22a contains a positive active material. As the positive active material, a known positive active material used in a lithium-ion secondary battery may be used. Specifically, for example, as the positive active material, a lithium composite oxide, a lithium transition metal phosphate compound, etc. can be used. These positive active materials may be used alone or in combination of two or more. The positive active material layer 22a may contain components other than the positive active material, such as a conductive material, a binder, etc. As the conductive material, for example, carbon black such as acetylene black (AB) or other carbon materials (e.g., graphite) can be preferably used. As the binder, for example, polyvinylidene fluoride (PVDF) etc. can be used.

[0017] 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 on at least one surface of the negative electrode current collector 24c.

[0018] 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 appropriately determined according to the battery design. A plurality of 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 a part of the negative electrode current collector 24c and is made of a metal foil (for example, a copper foil). The negative electrode active material layer 24a is formed on a part of the negative electrode tab 24t. In at least a part of the negative electrode tab 24t, the negative electrode current collector 24c is exposed without the formation of the negative electrode active material layer 24a. The plurality of negative electrode tabs 24t are laminated at one end (the right end in FIG. 2) in the long side direction Y to form a negative electrode tab group 25. The plurality of negative electrode tabs 24t are bent and curved so that the 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.

[0019] 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, and for example, 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 the graphite is coated with an amorphous carbon material. The negative electrode active material layer 24a may contain components other than the negative electrode active material, such as a binder and a thickener. As the binder, for example, styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), etc. can be used. As the thickener, for example, carboxymethyl cellulose (CMC), etc. can be used.

[0020] The separator 26 is an insulating resin sheet in which a plurality of fine through-holes through which charge carriers can pass are formed. The configuration of the separator 26 is not particularly limited and may be the same as that used in conventionally known 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.

[0021] As described above, the secondary battery 100 includes an electrolytic solution. The electrolytic solution is not particularly limited and may be the same as that used in conventionally known batteries. The electrolytic solution may be, for example, a non-aqueous electrolytic solution containing a non-aqueous solvent (organic solvent) and an electrolyte salt (supporting salt). Examples of the non-aqueous solvent 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 lithium salts such as LiPF6 and LiBF4 are particularly suitable. The electrolytic solution may contain various additives such as a film-forming agent, a gas-generating agent, a dispersant, and a thickener.

[0022] As shown in FIGS. 1 and 2, the battery 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 (the left end in FIGS. 1 and 2) in the long-side direction Y of the sealing plate 14. The negative electrode terminal 40 is attached to the other end (the right end in FIGS. 1 and 2) in the long-side direction Y of the sealing plate 14. The positive electrode terminal 30 and the negative electrode terminal 40 are inserted through the terminal mounting holes 18 and 19 and extend from the outer surface side to the inner surface side of the sealing plate 14. The lower end of the positive electrode terminal 30 is connected to the 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 body 20 via the positive electrode current collector 50. The lower end of the negative electrode terminal 40 is connected to the 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.

[0023] The positive electrode terminal 30 is preferably made of metal, and more preferably made of, for example, aluminum or an aluminum alloy. The negative electrode terminal 40 is preferably made of metal, and more preferably made of, for example, copper or a copper alloy. 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 outside the battery case 10. The external conductive member 35 is a member to which a bus bar is attached when a plurality of secondary batteries are electrically connected to each other. The external conductive member 35 is preferably made of metal, and more preferably made of, for example, aluminum or an aluminum alloy. However, the external conductive member 35 is not essential and can be omitted in other embodiments.

[0024] As shown in FIGS. 1 and 2, the external conductive members 35 are insulated by external insulating members 70 respectively. Further, gaskets 72 are attached to the terminal mounting holes 18 and 19 of the sealing plate 14 respectively. Thereby, the electrode terminals (positive electrode terminal 30 and negative electrode terminal 40) inserted through the terminal mounting holes 18 and 19 and the sealing plate 14 are insulated from each other. The external insulating member 70 and the gasket 72 can be made of, for example, fluorine-based resins such as perfluoroalkoxy alkane (PFA) and polytetrafluoroethylene (PTFE), or synthetic resin materials such as polyphenylene sulfide (PPS).

[0025] As shown in FIG. 1, the battery case 10 has a rectangular parallelepiped shape (square shape) with a bottom here. Conventionally known materials can be used for the battery case 10 without particular limitation. The battery case 10 (case body 12 and sealing plate 14) can be made of, for example, aluminum, an aluminum alloy, stainless steel, iron, an iron alloy, or the like. Among them, the battery case 10 is preferably made of aluminum.

[0026] From the perspective of increasing the battery capacity, it is preferable to increase the size of the electrode body 20, and the battery case 10 also tends to increase in size. The battery case 10 of the secondary battery 100 disclosed herein is preferably sized to accommodate a relatively large electrode body 20. Although not particularly limited, for example, the length in the long side direction Y of the battery case 10 is preferably 100 mm or more and 500 mm or less, and more preferably 200 mm or more and 400 mm or less. Also, although not particularly limited, the length in the short side direction X of the battery case 10 is preferably 10 mm or more and 60 mm or less, and more preferably 20 mm or more and 50 mm or less. The height (length in the vertical direction Z) of the battery case 10 is not particularly limited, but for example, it is preferably about 70 mm or more and 120 mm or less.

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

[0028] The sealing plate 14 is substantially rectangular in plan view here and is a member for sealing the opening 12h of the case body 12. The sealing plate 14 has an inner surface 14a (see FIG. 5) which is the surface on the inner side (the side facing the electrode body 20) of the secondary battery 100 and an outer surface 14b (see FIG. 5) which is the surface on the outer side. 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 injection hole 15 and a gas discharge valve 17. The liquid injection hole 15 is a through hole for injecting an electrolytic solution into the battery case 10 after the sealing plate 14 is assembled to the case body 12. The liquid injection hole 15 is sealed by a sealing member 16 after the injection of the electrolytic solution. The gas discharge valve 17 is configured to break when the pressure in the battery case 10 reaches a predetermined value or more and discharge the gas in the battery case 10 to the outside. Although not particularly limited, the average thickness (average plate thickness) of the sealing plate 14 is preferably generally 0.3 mm or more, for example 0.5 mm or more, from the viewpoint of durability and the like, and may be generally 5 mm or less, for example 3 mm or less, or may be 2.5 mm or less from the viewpoints of cost and energy density.

[0029] FIG. 4 is a plan view of FIG. 1. As shown in FIG. 4, the sealing plate 14 and the peripheral edge portion of the opening 12h of the case body 12 (hereinafter referred to as "opening peripheral edge portion 12d") are welded and joined, and a welded portion 10w is formed along the boundary between the case body 12 and the sealing plate 14. Such welded joining can be realized by, for example, laser welding. The welded portion 10w is a portion formed by melting the constituent metal of the case body 12 and the constituent metal of the sealing plate 14 when the boundary between the case body 12 and the sealing plate 14 is laser welded. Here, the welded portion 10w is located on the outer surface side of the sealing plate 14. In the welded portion 10w, the inner peripheral edge of the opening 12h of the case body 12 and the outer peripheral edge of the sealing plate 14 are connected so as to be flush. The welded portion 10w is formed continuously in a substantially annular shape along the boundary between the sealing plate 14 and the case body 12 in plan view.

[0030] In the case body 12, support portions 12f (see FIG. 7) may be provided on the inner wall surfaces of a pair of short side portions among the opening peripheral edge portion 12d. The support portions 12f are formed so as to project in the inner direction of the case body 12. Thereby, the sealing plate 14 fitted into the opening 12h is placed on the support portions 12f, and does not sink deeply from the opening 12h. For this reason, the outer surface 14b of the sealing plate 14 is arranged to be substantially flush with the upper surface of the opening peripheral edge portion 12d adjacent thereto. Note that the support portions 12f may be provided on the short side portions of the opening peripheral edge portion 12d, or may be provided at the four corner portions.

[0031] FIG. 5 is a schematic cross-sectional view taken along the line V-V of FIG. 4. As shown in FIG. 5, in the secondary battery 100 disclosed herein, in at least a part of the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other, there is a surface treatment portion 80 that is surface-treated black so that the light absorption rate in the wavelength range of 300 nm to 1100 nm is higher than that of other portions. In this specification, the "light absorption rate" refers to a value calculated by the formula: light absorption rate A (%) = 100% - T (%) - R (%) from the transmittance T (%) and reflectance R (%) of a sample measured using a spectrophotometer. Also, in this specification, the "light absorption rate in the wavelength range of 300 nm to 1100 nm" shall refer to the minimum laser light absorption rate in the said wavelength range. In the following description, unless otherwise specified, the "light absorption rate" refers to the minimum light absorption rate in the wavelength range of 300 nm to 1100 nm as described above.

[0032] Although not particularly limited, the surface treatment portion 80 preferably has a light absorption rate of 60% or more in the wavelength range of 300 nm to 1100 nm. Such a light absorption rate may mean the ratio of the laser light absorbed by the surface treatment portion 80 among the laser light irradiated to the case body 12 and the sealing plate 14 in the welding step S40 described later. By providing such a surface treatment portion 80 in at least a part of the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other, the laser light during welding can be effectively absorbed. For this reason, for example, it is possible to suitably suppress the laser light from entering the case interior through the gap at the boundary between the sealing plate 14 and the case body 12.

[0033] Although not particularly limited, the light absorption rate of the surface treatment portion 80 in the wavelength range of 300 nm to 1100 nm may be more than 60%, may be 65% or more, may be 70% or more, or may be 80% or more. The light absorption rate of such a surface treatment portion 80 may be 100%, but practically, 95% or less is preferable, and 90% or less may also be acceptable. Such a light absorption rate can be appropriately adjusted according to the implementation time of the surface treatment (for example, anodizing treatment) and the type and amount of the black coloring agent described later.

[0034] Note that the transmittance T(%) and reflectance R(%) of the surface treatment portion 80 are not particularly limited. From the viewpoint of easily increasing the light absorption rate, in some embodiments, the surface treatment portion 80 has a transmittance of a specific laser light at the wavelength where the light absorption rate is minimized in the wavelength range of 300 nm to 1100 nm, which may be, for example, less than 35%, may be less than 20%, or may be less than 10%. The lower limit of the transmittance of the surface treatment portion 80 is not particularly limited and may be, for example, 1% or more, or may be 5% or more. Also, the surface treatment portion 80 has a reflectance of a specific laser light at the wavelength where the light absorption rate is minimized in the wavelength range of 300 nm to 1100 nm, which may be, for example, less than 20%, or may be less than 10%. The lower limit of the reflectance of the surface treatment portion 80 is not particularly limited and may be 0. From a practical viewpoint, usually, the reflectance of the surface treatment portion 80 is suitably 1% or more, and may be 3% or more.

[0035] The form of the surface treatment unit 80 is not particularly limited as long as it can improve the light absorption rate in the wavelength range of 300 nm to 1100 nm. The surface treatment unit 80 can improve the light absorption rate by being treated black. The surface treatment unit 80 may be surface-treated black, for example, by anodizing, coloring, chemical conversion treatment, plating treatment, coating treatment, or the like. The surface treatment unit 80 may be configured by performing a plurality of treatments.

[0036] Although not particularly limited, the surface treatment unit 80 may be composed of an anodic oxide film. That is, the battery case 10 (the case body 12 and the sealing plate 14) is made of aluminum, and it is preferable that an aluminum oxide layer formed by anodizing is formed at least in part of the region where the opening peripheral edge 12d and the side surface 14d of the sealing plate face each other. Thereby, the light absorption rate of the surface treatment unit 80 can be suitably improved.

[0037] Also, although not particularly limited, the surface treatment unit 80 may be composed of a black colored layer containing a black coloring agent. The black coloring agent is contained, for example, in a dispersed state in the black colored layer. As the black coloring agent, conventionally known pigments and dyes can be used. Examples of the pigment include inorganic pigments and organic pigments. Specific examples of the black coloring agent include carbon black, graphite, aniline black, titanium black, the inorganic pigment hematite, activated carbon, and the like. The black coloring agent can be used alone or in appropriate combination of two or more kinds.

[0038] As described above, the surface treatment portion 80 is formed in at least a part of the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other. The surface treatment portion 80 may be formed on either the opening peripheral edge portion 12d of the case body 12 or the sealing plate 14, or may be formed on both the opening peripheral edge portion 12d of the case body 12 and the sealing plate 14. When the surface treatment portion 80 is formed on the opening peripheral edge portion 12d, specifically, it is preferably formed on at least a part of the inner wall surface 12e of the opening peripheral edge portion 12d, and may be formed over the entire region of the inner wall surface 12e that faces the side surface 14d of the sealing plate 14. When the surface treatment portion 80 is formed on the opening peripheral edge portion 12d, its length in the vertical direction Z is preferably about the same as the average thickness of the sealing plate 14. Although not particularly limited, when the surface treatment portion 80 is formed on the opening peripheral edge portion 12d, such a surface treatment portion 80 is preferably formed from the upper end of the opening peripheral edge portion 12d toward the bottom surface side by about 0.1 mm to 6 mm (for example, 0.2 mm to 5 mm). Thereby, it is possible to suitably suppress the laser light from entering the case interior.

[0039] When the surface treatment portion 80 is formed on the sealing plate 14, specifically, it may be formed on at least a part of the side surface 14d of the sealing plate 14, or may be formed over the entire side surface 14d. When the surface treatment portion 80 is formed on the side surface 14d of the sealing plate 14, its length in the vertical direction Z may be about the same as the average thickness of the sealing plate 14 or may be different. For example, when butting against the inner wall surface 12e of the case body 12, it is preferable that the surface treatment portion 80 is provided in at least the lower region of the side surface 14d (that is, the region that is 50% or less from the inner surface side when the average thickness of the sealing plate 14 is 100%). Although not particularly limited, the surface treatment portion 80 is preferably formed from the inner surface side to the outer surface side of the sealing plate 14 by about 0.1 mm to 5 mm (for example, 0.2 mm to 4 mm). Thereby, it is possible to suitably suppress the laser light from entering the case interior during welding, and to provide a secondary battery 100 with higher safety.

[0040] <Method for manufacturing a secondary battery> Hereinafter, as a preferred embodiment of the method for manufacturing the power storage device disclosed herein, a lithium-ion secondary battery will be described as an example, but it is not intended to limit the application target to such batteries.

[0041] FIG. 6 is a flowchart diagram generally showing the method for manufacturing the power storage device disclosed herein. As shown in FIG. 6, the method for manufacturing the power storage device disclosed herein includes a preparation step S10 of preparing the case body 12, the sealing plate 14, and the electrode body 20 as described above, a surface treatment step S20 of forming the surface treatment portion 80, an assembly step S30 of accommodating the electrode body 20 inside the case body 12 and attaching the sealing plate 14 to the case body 12 to assemble the power storage device, and a welding step S40 of irradiating laser light from the outer surface side of the sealing plate 14 to the boundary between the case body 12 and the sealing plate 14 to laser-weld the case body 12 and the sealing plate 14. The welding step S40 may further include a temporary welding step S42 of irradiating laser light from the outer surface side of the sealing plate 14 to a predetermined portion of the boundary between the case body 12 and the sealing plate 14 to temporarily weld the case body 12 and the sealing plate 14, and a full-circumference welding step S44 of scanning laser light along the boundary between the case body 12 and the sealing plate 14 to fully weld the case body 12 and the sealing plate 14. In the manufacturing method disclosed herein, at least a part of the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other is characterized in that the light absorption rate of the laser used in the welding step S40 is higher than that of other parts, and the other processes may be the same as those in the prior art. Also, other steps may be further included at any stage.

[0042] Among the above-described preparation step S10 to welding step S40, the preparation step S10, the surface treatment step S20, and the assembly step S30 can be carried out in any order. The preparation step S10, the surface treatment step S20, and the assembly step S30 may be carried out one or more of them first, or two or more of them may be carried out simultaneously. For example, the surface treatment step S20 and the assembly step S30 can also be carried out in parallel.

[0043] When manufacturing a power storage device, the case body 12 and the sealing plate 14 are typically prepared separately. Therefore, dimensional tolerances occur in each component, and as a result, a slight gap may occur between the case body 12 and the sealing plate 14. Such a gap can be generally eliminated by pressing with a clamp in a state where the sealing plate 14 is attached to the case body 12, but a slight gap may occur between the case body 12 and the sealing plate 14 due to wear of the clamp and accompanying deformation. Also, there is a possibility that a slight gap may occur depending on the combination of the case body 12 and the sealing plate 14. Alternatively, the relative position and posture of the laser irradiation device and the battery case 10, that is, the irradiation angle of the laser light with respect to the laser light irradiation position, may vary due to errors in workpiece mounting and fixing for each manufactured solid. When laser irradiation is performed with such a gap occurring at any position at the boundary between the case body 12 and the sealing plate 14, so-called "laser leakage" may occur where the laser light directly enters the case interior from such a gap. Alternatively, even if the angle of the laser light is adjusted so that laser leakage does not occur, the laser light may be reflected in the gap between the opening peripheral edge portion 12d and the sealing plate 14, and secondary reflected light or tertiary reflected light may enter the case interior. When laser light enters the case interior, there is a risk of damaging the contents inside the case (for example, the electrode body housed in the case), which is not preferable. Therefore, in the manufacturing method disclosed herein, at least a part of the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other is configured such that the light absorption rate of the laser used in the welding process is higher than that of other parts. Thereby, it is possible to suppress the laser light from entering the case interior, and it is possible to provide a power storage device with higher safety.

[0044] In the preparation step S10, the case body 12, the sealing plate 14, and the electrode body 20 as described above are prepared. The electrode body 20 can be manufactured according to a known method. As shown in FIG. 3, when the electrode body 20 is a wound electrode body, such a wound electrode body 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 as to be 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 as to protrude in opposite directions from the ends of the two separators 26 in the longitudinal direction Y. Next, the prepared laminate is wound longitudinally around the winding axis. The winding of the laminate can be carried out according to a known method. The wound laminate is pressed to produce a flat wound electrode body. This pressing process may be carried out using a known pressing device used for manufacturing a general flat wound electrode body, and is not particularly limited. In this way, the electrode body 20 can be prepared.

[0045] In the surface treatment step S20, surface treatment is performed on at least a part of the prepared case body 12 and the sealing plate 14 so that the light absorption rate of the laser used in the welding step S40 described later is higher than that of other parts. Preferably, surface treatment is performed in black so that the light absorption rate in the wavelength range of 300 nm to 1100 nm is higher than that of other parts in at least a part of the region where the opening peripheral edge 12d and the sealing plate 14 face each other. Although not particularly limited, at least a part of the region where the opening peripheral edge 12d and the sealing plate 14 face each other is preferably surface-treated in black so that the light absorption rate in the wavelength range of 300 nm to 1100 nm is 60% or more, and more preferably surface-treated in black so that the light absorption rate is 75% or more. Such surface treatment may be carried out so that the light absorption rate is 100%, but practically, it is preferably surface-treated so that the light absorption rate is about 95% or less. The method of such surface treatment is not particularly limited, and examples thereof include methods such as anodizing treatment, coloring treatment, chemical conversion treatment, plating treatment, and coating treatment.

[0046] The surface treatment step S20 can be implemented, for example, by anodizing. The anodizing can be performed using a known method. By changing the time of such anodizing, the light absorption rate of the surface treatment unit 80 can be adjusted. For example, by performing anodizing for 1 minute or more and about 20 minutes (preferably 2 minutes or more and 15 minutes or less), the light absorption rate in the wavelength range of 300 nm to 1100 nm can be made 60% or more. In the surface treatment step S20, when performing black surface treatment by anodizing, in the preparation step S10, the case body 12 and the sealing plate 14 made of aluminum are prepared.

[0047] Also, the surface treatment step S20 can be implemented by coloring treatment. Specifically, a black coloring agent is applied to a desired position of the case body 12 and / or the sealing plate 14. The black coloring agent may be a conventionally known black inorganic pigment or black organic pigment. The surface treatment step S20 can be implemented, for example, using an aqueous ink in which a black pigment and a resin are dispersed in an aqueous solvent, or an organic ink in which a black pigment and a resin are dispersed in a highly volatile organic solvent. Note that both the above-described anodizing and coloring treatment may be performed.

[0048] When implementing the surface treatment step S20 by coloring treatment, it may be implemented simultaneously with the assembly step S30 described later. Specifically, when attaching the sealing plate 14 to the case body 12, ink containing a black coloring agent is supplied in advance to a gripping member 110 (see FIG. 7) that grips the sealing plate 14, and it is preferably configured such that when the sealing plate 14 is gripped by the gripping member 110, it is surface-treated black. Thereby, black surface treatment can be easily performed at a desired position. Also, the manufacturing process can be shortened, which is preferable from the viewpoint of manufacturing efficiency.

[0049] FIG. 7 is a diagram schematically showing the state of the assembly process S30. In the assembly process S30, 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. Specifically, 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 portion 50 and the negative electrode current collector portion 60. Next, as shown in FIG. 7, the sealing plate 14 (here, the side surface 14d) is gripped by the gripping member 110, and the electrode body 20 is inserted inside the case body 12. At this time, it is preferable to insert the electrode body 20 so that the winding axis WL is arranged inside the case body 12 in a direction along the bottom surface 12a (that is, a direction in which the winding axis WL is parallel to the long side direction Y).

[0050] The sealing plate 14 is attached to the opening 12h of the case body 12. In the example shown in FIG. 7, the outer diameter of the sealing plate 14 is formed 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. A part of the sealing plate 14 is placed on the support portion 12f of the case body 12 so that the inner wall surface 12e of the case body 12 and the side surface 14d of the sealing plate 14 face each other here. Such a support portion 12f can suppress the entry of laser light in the welding process S40 described later. On the other hand, in a pair of long side portions of the opening peripheral edge portion 12d, it is difficult to provide the support portion 12f because sufficient strength of the support portion 12f cannot be ensured. For this reason, in the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other, particularly in the long side portion, the surface is treated so that the light absorption rate of the laser used in the welding process S40 is higher than that of other portions, whereby the effects of the technology disclosed herein can be preferably exhibited. Further, in a power storage device that is relatively large (for example, the length in the long side direction Y is about 100 mm or more and 500 mm or less), it is particularly difficult to provide the support portion 14f in the long side portion from the above-described viewpoint. Therefore, in such a large power storage device, in the long side portion of the region where the opening peripheral edge portion 12d and the sealing plate 14 face each other, the surface is treated so that the light absorption rate of the laser used in the welding process S40 is higher than that of other portions, whereby the effects of the technology disclosed herein can be further exhibited.

[0051] FIG. 8 is a diagram schematically showing the state of the welding process S40. In FIG. 8, for the sake of explanation, the gap between the case body 12 and the sealing plate 14 is deliberately drawn large. In the welding process S40, after the electrode body 20 is accommodated inside the battery case 10, laser light IL is irradiated onto the boundary between the case body 12 and the sealing plate 14 using the laser irradiation device 120. As described above, the welding process S40 irradiates laser light IL onto a predetermined portion of the boundary between the case body 12 and the sealing plate 14 to temporarily weld the case body 12 and the sealing plate 14 in a temporary welding process S42, and scans the laser light IL along the boundary between the case body 12 and the sealing plate 14 to perform full-circumference welding of the case body 12 and the sealing plate 14 in a main welding process S44, and may include these processes.

[0052] The laser irradiation device 120 used in the welding process S40 (the temporary welding process S42 and the main welding process S44) may be the same as a conventionally known device and is not particularly limited. The laser irradiation device 120 includes, for example, a laser irradiation unit 122. Here, a fiber laser is adopted for the laser irradiation unit 122, and thus the laser irradiation unit 122 is configured as a fiber laser irradiator. However, the laser of the laser irradiation unit 122 is not limited to a fiber laser, and there is no limitation on its type as long as it can weld the case body 12 and the sealing plate 14. The laser may be, for example, a solid-state laser (e.g., YAG laser, glass laser, ruby laser, etc.), a liquid laser (e.g., dye laser, etc.), a gas laser (e.g., CO2 laser, etc.), a semiconductor laser, a free-electron laser, a chemical laser, etc.

[0053] It is preferable to use a laser irradiation device 120 in which the wavelength of the laser is 300 nm to 1100 nm. By using the laser irradiation device 120 in which the wavelength of the laser is in the above range, the case body 12 and the sealing plate 14 can be suitably welded. Note that the welding device used in the temporary welding process S42 and the welding device used in the main welding process S44 may be the same or different. From the viewpoint of manufacturing efficiency, it is preferable to use the same welding device in the temporary welding process S42 and the main welding process S44.

[0054] As described above, in a preferred embodiment, in the surface treatment step S20, at least a part of the region where the peripheral edge portion 12d of the opening and the sealing plate 14 face each other is surface-treated black so that the light absorption rate in the wavelength range of 300 nm to 1100 nm is higher than that of other parts. Therefore, in the welding step S40, by using the laser irradiation device 120 whose laser wavelength is 300 nm to 1100 nm, it is possible to preferably suppress the laser light from entering the inside of the case.

[0055] In the tack welding step S42, the laser light is irradiated to a predetermined part of the boundary between the case body 12 and the sealing plate 14. Thereby, the positional relationship between the case body 12 and the sealing plate 14 can be fixed. Further, by performing the tack welding step S42 in a step prior to the main welding step S44 described later, it is possible to suppress the sealing plate 14 from being deformed by heat, and a more accurate welded joint can be realized.

[0056] As shown in FIG. 8, the laser beam IL is irradiated from the outer surface side of the sealing plate 14 with respect to the boundary between the case body 12 and the sealing plate 14. In the tack welding step S42, laser welding is performed at a predetermined position (for example, about 4 or more and 20 or less, preferably 8 or more and 16 or less) such that the case body 12 and the sealing plate 14 are not completely melted. For example, the tack welding step S42 can be performed by scanning the laser beam from the center side to the outer edge side of the sealing plate 14 at a predetermined position. Alternatively, the tack welding step S42 can be performed by scanning the laser beam from the outer edge side to the center side of the sealing plate 14 at a predetermined position. The conditions for laser welding in the tack welding step S42 are not particularly limited. The angle of the laser beam (the smaller angle of the angle formed by the laser irradiation direction and the outer surface 14b (horizontal plane) of the sealing plate 14) is preferably, for example, 80° or more and 87° or less, and more preferably 80° or more and 85° or less. Also, the output value of the laser is preferably 1000W or more and 5000W or less, and more preferably 2000W or more and 4000W or less. Also, although not particularly limited, the scanning speed of the laser may be 100 mm / second to 200 mm / second, and preferably 150 mm / second to 180 mm / second.

[0057] In the manufacturing method disclosed herein, it is preferable that the portion to be tack welded in the tack welding step S42 has a higher light absorption rate of the laser used in the tack welding step than other portions. In the tack welding step S42, as described above, since the case body 12 and the sealing plate 14 are not completely melted, a molten pool is not formed. For this reason, laser leakage and the reflected light RL of the laser beam IL are likely to occur as described above. That is, in the tack welding step S42, the laser beam easily enters the case. Therefore, by providing the surface treatment portion 80 at least at the position to be welded in the tack welding step S42, it is possible to more preferably suppress the laser beam from entering the case.

[0058] In this welding step S44, a laser beam is scanned along the boundary between the case body 12 and the sealing plate 14 to weld the case body 12 and the sealing plate 14 over the entire circumference. As a result, a welded portion 10w is formed at the boundary between the case body 12 and the sealing plate 14, and the battery case 10 can be hermetically sealed.

[0059] As shown in FIG. 8, the laser beam IL is irradiated from the outer surface side of the case body 12 with respect to the boundary between the case body 12 and the sealing plate 14. In this welding step S44, the constituent metal of the case body 12 and the constituent metal of the sealing plate 14 are melted to form a molten pool. The conditions for laser welding in this welding step S44 are not particularly limited. The angle of the laser beam (the smaller of the angles formed by the laser irradiation direction and the outer surface 14b (horizontal plane) of the sealing plate 14) is preferably, for example, 80° or more and 87° or less, and more preferably 80° or more and 85° or less. Also, the output value of the laser is preferably 1000 W or more and 5000 W or less, and more preferably 2000 W or more and 4000 W or less. Further, although not particularly limited, the scanning speed of the laser may be 100 mm / second to 200 mm / second, and is preferably 150 mm / second to 180 mm / second.

[0060] <Modification Example> In the above-described embodiment, the sealing plate 14 is attached to the opening 12h of the case body 12 such that the inner wall surface 12e of the peripheral edge portion 12d of the opening of the case body 12 and the side surface 14d of the sealing plate 14 face each other. However, the technology disclosed herein is not limited to the above-described embodiment. FIG. 9 is a corresponding view of the secondary battery 200 according to a modified example with respect to FIG. 8. In FIG. 9, for the sake of explanation, the gap between the case body 212 and the sealing plate 214 is deliberately drawn large. In the secondary battery 200, the sealing plate 214 is attached to the case body 212 such that the upper end 212f of the peripheral edge portion 212d of the opening of the case body 212 and the inner surface 214a of the sealing plate 214 face each other. When the upper end 212f of the peripheral edge portion 212d of the opening of the case body 212 and the inner surface 214a of the sealing plate 214 are butted against each other, as shown in FIG. 9, in the welding step S40, the laser light IL is irradiated substantially horizontally with respect to the boundary between the case body 212 and the sealing plate 214. When there is a slight gap due to dimensional tolerances and the like as described above between the sealing plate 214 and the case body 212, the irradiated laser light IL may be reflected between the sealing plate 214 and the case body 212, and the reflected light RL may enter the case interior. Therefore, in the secondary battery 200, in at least a part of the region where the upper end 212f of the peripheral edge portion 212d and the inner surface 214a of the sealing plate 214 face each other, there is a surface treatment portion 280 that is surface-treated so that the light absorption rate of the laser used in the welding step S40 becomes high. The surface treatment portion 280 may be formed on either one of the upper end 212f of the peripheral edge portion 212d of the opening and the inner surface 214a of the sealing plate 214, or may be formed on both the upper end 212f of the peripheral edge portion 12d of the opening and the inner surface 214a of the sealing plate 214. Such a surface treatment portion 280 is preferably surface-treated black so that the light absorption rate in the wavelength range of 300 nm to 1100 nm is 60% or more, and more preferably surface-treated black so that the light absorption rate is 75% or more. Such a surface treatment portion 280 may be implemented so that the light absorption rate becomes 100%, but practically, it is preferably surface-treated so that the light absorption rate is about 95% or less. Such a surface treatment portion 280 can be formed by performing the above-described surface treatment step S20 in a step prior to the welding step S40.

[0061] <Battery Applications> The above-described battery can be used for various applications. For example, it can be suitably used 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), battery electric vehicles (BEVs), etc. The battery can also be suitably used in the construction of battery packs.

[0062] Hereinafter, test examples related to the present invention will be described, but the present invention is not intended to be limited to those shown in the following test examples.

[0063] <Example 1> First, lithium nickel cobalt manganese composite oxide (NCM) as a positive electrode active material, acetylene black (AB) as a conductive material, and PVdF as a binder were prepared. These were mixed in N-methylpyrrolidone (NMP) as a solvent to prepare a slurry for forming a positive electrode active material layer. This slurry was applied in a strip shape to both sides of a long aluminum foil and dried to produce a positive electrode sheet. Next, graphite (C) as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a dispersant were prepared. These were mixed in ion-exchanged water as a solvent to prepare a slurry for forming a negative electrode active material layer. This slurry was applied in a strip shape to both sides of a long copper foil and dried to produce a negative electrode sheet. And as separator sheets, two sheets each having a heat-resistant layer containing alumina and PVdF on the surface of a PE base material part were prepared. The produced positive electrode sheet and negative electrode sheet were opposed to each other with a separator sheet interposed therebetween and laminated, and wound to produce an electrode body.

[0064] Next, a bottomed case body having an opening on one side facing the bottom surface and a rectangular sealing plate for sealing the opening were prepared. In Example 1, the side surface of the sealing plate was colored black using an oil-based pen. The light absorption rate of the black-colored portion (i.e., the side surface of the sealing plate) was measured with a spectrophotometer. The results are shown in Table 1. Then, the wound electrode body prepared above was housed in the case body, and the sealing plate was attached to the case body such that the peripheral edge of the opening of the case body and the side surface of the sealing plate faced each other.

[0065] In Example 1, the distance (gap amount) between the side surface of the sealing plate and the inner wall surface of the peripheral edge of the opening was adjusted to be 0.1 mm. Specifically, a SUS plate was sandwiched between the case body and the sealing plate to adjust the gap amount. Then, a high-power fiber laser was used to temporarily weld the boundary between the peripheral edge of the opening and the peripheral edge of the sealing plate. Specifically, laser light was irradiated at a total of 16 locations under the conditions of oscillator output: 3000 W, welding speed: 150 mm / second, focal length: 0 mm, and angle: +7 deg (83°). After the temporary welding, the battery was disassembled to check for damage to the electrode body. The results are shown in Table 1. In the "angle (deg)" in Table 1, the angle from the center of the battery case to the outside is indicated by a minus (-), and the angle from the outside of the battery case to the center is indicated by a plus (+).

[0066] <Examples 2 and 3> The boundary between the peripheral edge of the opening and the peripheral edge of the sealing plate was temporarily welded in the same manner as in Example 1, except that the gap amount (mm) and the angle (deg) were changed as shown in Table 1. The results are shown in Table 1.

[0067] <Comparative Examples 1 to 3> In Comparative Examples 1 to 3, the side surface of the sealing plate was not colored black. Also, the gap amount (mm) and the irradiation angle (deg) were changed as shown in Table 1. The boundary between the peripheral edge of the opening and the peripheral edge of the sealing plate was temporarily welded in the same manner as in Example 1, except for these. The results are shown in Table 1.

[0068]

Table 1

[0069] As shown in Table 1, in Examples 1 to 3 in which the side surface of the sealing plate was colored black, it was found that the electrode body was not damaged. This is presumably because by coloring the side surface of the sealing plate black, the light absorption rate of the laser used in the welding process increased, and the laser light was preferably absorbed.

[0070] As described above, some embodiments of the present invention have been described, but 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 content disclosed in this specification and common general knowledge in the art. The technology described in the claims includes various modifications and changes of the above-exemplified embodiments. For example, it is also possible to replace a part of the above-described embodiments with other modified forms, and it is also possible to add other modified forms to the above-described embodiments. Further, if its technical features are not described as essential, they can be appropriately deleted.

[0071] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A method for manufacturing a power storage device, including a step of preparing a bottomed case body having an opening on one side, a sealing plate for sealing the opening, and an electrode body having a positive electrode and a negative electrode; a step of accommodating the electrode body inside the case body, attaching the sealing plate to the opening of the case body, and assembling the power storage device; and a step of irradiating laser light from the outer surface side of the sealing plate to the boundary between the case body and the sealing plate, and laser-welding the case body and the sealing plate, wherein at least a part of the region where the peripheral edge of the opening of the case body faces the sealing plate has a higher light absorption rate of the laser used in the welding step than other parts. Item 2: The welding process includes a temporary welding process in which laser light is irradiated from the outer surface side of the sealing plate onto a predetermined portion of the boundary between the case body and the sealing plate to temporarily weld the case body and the sealing plate, and a main welding process in which laser light is scanned along the boundary between the case body and the sealing plate to perform full-circumference welding of the case body and the sealing plate. In the region where the opening peripheral edge of the case body faces the sealing plate, the portion temporarily welded in the temporary welding process has a higher light absorption rate of the laser used in the temporary welding process than other portions. The manufacturing method according to Item 1. Item 3: At least a part of the region where the opening peripheral edge of the case body faces the sealing plate is surface-treated black so as to have a high light absorption rate for light with a wavelength of 300 nm to 1100 nm. The manufacturing method according to Item 1 or Item 2. Item 4: A storage device including a bottomed case body with one side open, a sealing plate welded to the opening peripheral edge of the case body, and an electrode body housed inside the case body. In at least a part of the region where the opening peripheral edge of the case body faces the sealing plate, there is a surface treatment portion that is treated black so as to have a higher light absorption rate for light with a wavelength of 300 nm to 1100 nm than other parts. Item 5: The storage device according to Item 4, wherein the surface treatment portion has a light absorption rate of 60% or more for light with a wavelength of 300 nm to 1100 nm. Item 6: The case body and the sealing plate are made of aluminum, and the surface treatment portion is made of an anodized film. The storage device according to Item 4 or Item 5. Item 7: The storage device according to any one of Items 4 to 6, wherein the surface treatment portion is a black coloring layer containing a black coloring agent.

Description of Reference Numerals

[0072] 10 Battery case 10w Welded portion 12 Case body 12a Bottom surface 12b Long side wall 12c Short side wall 12d Opening peripheral edge 12e Inner wall surface 12f support part 12h opening 14 sealing plate 14a inner surface 14b outer surface 14d side surface 14f support part 20 electrode body 22 positive electrode sheet 24 negative electrode sheet 26 separator 30 positive electrode terminal 40 negative electrode terminal 50 positive electrode current collector 60 negative electrode current collector 80 surface treatment part 100 secondary battery 110 gripping member 120 laser irradiation device 200 secondary battery 212 case body 212d opening peripheral part 212f upper end 214 sealing plate 214a inner surface 280 surface treatment part

Claims

1. A step of preparing a bottomed case body with one side open, a sealing plate for sealing the opening, and an electrode body having a positive electrode and a negative electrode; A step of assembling a power storage device by housing the electrode body inside the case body and attaching the sealing plate to the opening of the case body; A step of irradiating laser light from the outer surface side of the sealing plate to a boundary between the case body and the sealing plate to laser-weld the case body and the sealing plate; including In a region where the peripheral edge of the opening of the case body and the sealing plate are butted against each other, at least a part of the region extending along the inner surface of the case body or the sealing plate has a higher light absorption rate of the laser used in the welding step than other parts; A method for manufacturing a power storage device.

2. The welding step includes a temporary welding step of irradiating laser light from the outer surface side of the sealing plate to a predetermined part of the boundary between the case body and the sealing plate to temporarily weld the case body and the sealing plate; A main welding step of scanning laser light along the boundary between the case body and the sealing plate to perform full-circumference welding of the case body and the sealing plate; including In a region where the peripheral edge of the opening and the sealing plate are butted against each other, among the regions extending along the inner surface of the case body or the sealing plate, the part temporarily welded in the temporary welding step has a higher light absorption rate of the laser used in the temporary welding step than other parts; The manufacturing method according to Claim 1.

3. In a region where the peripheral edge of the opening and the sealing plate are butted against each other, at least a part of the region extending along the inner surface of the case body or the sealing plate is surface-treated black so as to have a high light absorption rate for light with a wavelength of 300 nm to 1100 nm; The manufacturing method according to Claim 1 or 2.

4. The part having a higher light absorption rate than other parts is provided to absorb the laser light reflected in the gap between the peripheral edge of the opening and the sealing plate in the welding step. The manufacturing method according to Claim 1 or 2.

5. A bottomed case body with one side open; A sealing plate welded to the peripheral edge of the opening of the case body; An electrode body housed inside the case body; comprising In a region where the peripheral edge of the opening of the case body and the sealing plate are butted against each other, and at least a part of a region extending along the inner surface of the case body or the sealing plate, there is a surface treatment portion that is blackened so that the light absorption rate for light with a wavelength of 300 nm to 1100 nm is higher than that of other parts. Power storage device.

6. The surface treatment portion has a light absorption rate of 60% or more for light with a wavelength of 300 nm to 1100 nm. The power storage device according to claim 5.

7. The case body and the sealing plate are made of aluminum, and the surface treatment portion is made of an anodized film. The power storage device according to claim 5 or 6.

8. The surface treatment portion is a black coloring layer containing a black coloring agent. The power storage device according to claim 5 or 6.

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