Method for manufacturing an electricity storage device and an electricity storage device

Abstract

To provide a manufacturing method of a power storage device in which an electrode body is hardly damaged even if laser omission occurs.SOLUTION: The present invention discloses a manufacturing method of a power storage device 100 comprising a case main body 12, a sealing plate 14, an electrode body 20 and an insulating film body 70 interposed between the electrode body 20 and the case main body 12. The film body 70 includes a long side face 70b, which is interposed between a long side wall 12b of the case main body 12 and a wide face 20f of the electrode body 20, and a folding part 72 extending from the long side face 70b to the side of the sealing plate 14 and being folded closer to the electrode body 20. A light scattering part LS which scatters a laser beam is provided in the folding part 72. The manufacturing method includes: a preparation step of preparing the film body 70; a storage step of storing the electrode 20 and the film body 70 inside of the case main body 12; and a laser welding step of performing laser welding on an outer peripheral edge of the sealing plate 14 to an inner peripheral edge of an opening 12h of the case main body 12.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, there is known an electric storage device that includes a case body having an opening, a sealing plate (lid) that seals the opening of the case body, and an electrode body housed in the case body. This type of electric storage device is manufactured, for example, by housing the electrode body inside the case body through the opening, arranging the sealing plate in the opening of the case body, and laser welding the inner peripheral edge of the opening of the case body and the outer peripheral edge of the sealing plate. Patent documents 1 to 4 are related prior art documents.

[0003] For example, Patent Document 1 discloses a configuration in which a box-shaped insulating film (film body) is disposed between the case body and the electrode body, and an inclined surface that inclines toward the electrode body is formed at the end of the film body on the sealing plate side. Patent Document 1 describes that with this configuration, even if metallic foreign matter gets into the inside of the case body during laser welding or the like, the mixed metallic foreign matter can be trapped on the outside of the film body and prevented from entering the electrode body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-095836 A [Patent Document 2] JP 2014-29823 A [Patent Document 3] JP 2019-110036 A [Patent Document 4] JP 2016-91716 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to the study of the present inventor, a gap of about several tens of μm may occur between the opening of the case body and the sealing plate due to processing errors, etc. Therefore, during laser welding, the laser light may enter the case body through this gap, which is called laser leakage. Since the laser light has high linearity and focusing ability, if the laser light that has entered the case body hits the film body, the film body may melt due to the heat of the laser light. In addition, the electrode body may be burned or internally short-circuited when the laser light hits the electrode body.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a manufacturing method for an electricity storage device in which an electrode body is less likely to be damaged even if laser leakage occurs, and the electricity storage device. [Means for solving the problem]

[0007] The present invention provides a method for manufacturing an electricity storage device, comprising: a metal case body having a rectangular bottom wall, a pair of long side walls extending from a long side of the bottom wall and facing each other, a pair of short side walls extending from a short side of the bottom wall and facing each other, and an opening facing the bottom wall; a metal sealing plate disposed within the opening of the case body and having an outer peripheral edge portion laser welded to an inner peripheral edge portion of the opening of the case body; an electrode body contained in the case body and having a pair of wide surfaces facing the long side walls; and an insulating film body interposed between the electrode body and the case body, wherein the film body is interposed between the pair of long side walls of the case body and the pair of wide surfaces of the electrode body, respectively, and has a pair of long side surfaces extending along the long side walls, and a folding portion extending from each of the pair of long side surfaces toward the sealing plate and folded so as to approach the electrode body, and at least the folding portion is provided with a light diffusing portion that diffuses laser light. The manufacturing method includes a preparation step of preparing the film body, a accommodating step of accommodating the electrode body and the film body inside the case body, and a laser welding step of placing the sealing plate in the opening of the case body and laser welding the outer peripheral edge portion of the sealing plate to the case body.

[0008] In the above manufacturing method, a light diffusion section is provided at the folded portion of the film body. As a result, even if laser leakage occurs during laser welding and the laser light enters the case body through the gap between the case body and the sealing plate, the laser light can be diffused by the light diffusion section, and the beam density of the laser light can be reduced. As a result, the film body is less likely to melt due to the heat of the laser light. Therefore, the laser light is less likely to hit the electrode body, and thus the electrode body can be prevented from being burned or having an internal short circuit. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view that illustrates a schematic diagram of an electricity storage device according to an embodiment. [Diagram 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a schematic vertical cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view illustrating a film body according to an embodiment. [Diagram 5] FIG. 5 is a schematic diagram of an insulating film constituting the film body of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, some preferred embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of an electricity storage device that does not characterize the technology disclosed herein) can be understood as design matters of a person skilled in the art based on the conventional technology in the field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and the technical common sense in the field. It should be noted that the expression "A to B" indicating a range in this specification includes the meaning of "A or more and B or less", as well as "greater than A" and "less than B".

[0011] <Electricity storage device> FIG. 1 is a schematic perspective view of the electricity storage device 100. FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a schematic vertical cross-sectional view taken along line III-III in FIG. 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom. In the drawings, the symbol X represents the short side direction (thickness direction) of the electricity storage device 100, the symbol Y represents the long side direction perpendicular to the short side direction, and the symbol Z represents the height direction of the electricity storage device 100. However, these directions are merely for the sake of convenience in the description, and do not limit the installation form of the electricity storage device 100 in any way.

[0012] The power storage device 100 may be, for example, a secondary battery such as a lithium ion secondary battery or a nickel-hydrogen battery, or may be a lithium ion capacitor or an electric double layer capacitor, etc. Here, the power storage device 100 is a secondary battery, specifically a lithium ion secondary battery.

[0013] As shown in Fig. 2, the electricity storage device 100 includes a battery case 10, an electrode body 20 (see also Fig. 3), and a film body 70. Although not shown, the electricity storage device 100 further includes a nonaqueous electrolyte. As the nonaqueous electrolyte, any electrolyte used in a general nonaqueous electrolyte secondary battery (e.g., a lithium ion secondary battery) can be used without any particular limitation. However, in other embodiments, the electrolyte may be in a solid state (solid electrolyte) and integrated with the electrode body 20.

[0014] The battery case 10 is a housing that contains the electrode assembly 20 and the non-aqueous electrolyte. As shown in FIG. 1, the battery case 10 has a flat, bottomed rectangular parallelepiped (rectangular) outer shape. The material of the battery case 10 may be the same as that used conventionally, and is not particularly limited. The battery case 10 is made of metal, and is preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like. As shown in FIG. 2, the battery case 10 includes a case body 12 and a sealing plate (lid) 14.

[0015] The case body 12 is a container with a bottom and a rectangular cylindrical shape. As shown in FIG. 1, the case body 12 includes a rectangular bottom wall 12a, a pair of long side walls 12b extending from the long side of the bottom wall 12a and facing each other, a pair of short side walls 12c extending from the short side of the bottom wall 12a and facing each other, and an opening 12h (see FIG. 2) facing the bottom wall 12a. The opening 12h is rectangular. The long side wall 12b has a larger area than the short side wall 12c. In this specification, the term "rectangular" includes not only a perfect rectangular shape (rectangular shape), but also a shape in which the corners connecting the long side and short side of the rectangle are rounded or a shape in which a notch is formed at the corner. In the following description, the opening 12h side of the case body 12 may be referred to as "upper", and the bottom wall 12a side of the case body 12 may be referred to as "lower".

[0016] The sealing plate 14 is a plate-like member that seals the opening 12h of the case body 12. As shown in FIG. 2, the sealing plate 14 is disposed in the opening 12h of the case body 12. The sealing plate 14 faces the bottom wall 12a of the case body 12. The sealing plate 14 is rectangular. In a plan view, the outer shape of the sealing plate 14 is smaller than the opening 12h. The outer peripheral edge of the sealing plate 14 is laser welded to the inner peripheral edge of the opening 12h of the case body 12 over the entire circumference. A laser weld W is formed over the entire circumference of the outer peripheral edge of the sealing plate 14. This allows the battery case 10 to be integrated and hermetically sealed (sealed). Note that the laser weld W is not shown in FIG. 1.

[0017] As shown in Figs. 1 and 2, a positive electrode terminal 30 and a negative electrode terminal 40 are attached to the sealing plate 14. The positive electrode terminal 30 and the negative electrode terminal 40 are fixed to the sealing plate 14 by crimping. The positive electrode terminal 30 and the negative electrode terminal 40 are insulated from the sealing plate 14 by an insulating member (not shown). As shown in Fig. 2, the positive electrode terminal 30 is electrically connected to the positive electrode of the electrode body 20 via a positive electrode current collector 50 inside the battery case 10. The negative electrode terminal 40 is electrically connected to the negative electrode of the electrode body 20 via a negative electrode current collector 60 inside the battery case 10.

[0018] As shown in FIG. 2, the electrode body 20 is accommodated inside the battery case 10. The electrode body 20 may be the same as a conventional one and is not particularly limited. Although not shown, the electrode body 20 has a positive electrode and a negative electrode. The outer surface of the electrode body 20 is covered with a separator 26. The electrode body 20 is a flat wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked in an insulated state via the strip-shaped separator 26 and wound in the longitudinal direction around the winding axis. However, in other embodiments, the electrode body 20 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.

[0019] The electrode body 20 is housed inside the battery case 10 with its winding axis substantially parallel to the bottom wall 12a and the sealing plate 14 and substantially perpendicular to the long side wall 12b and the short side wall 12c. Both end faces (laminated surfaces where the positive electrode and the negative electrode are laminated) of the electrode body 20 in the winding axis direction face the pair of short side walls 12c. As shown in FIG. 3, the electrode body 20 has a pair of wide surfaces 20f having flat outer surfaces. The pair of wide surfaces 20f face the pair of long side walls 12b of the case body 12. The wide surfaces 20f and the lower end of the electrode body 20 are entirely covered with a film body 70 described later.

[0020] As shown in FIG. 2, a positive electrode current collecting part 22 is provided at one end of the electrode body 20 in the winding axis direction (long side direction Y in FIG. 2). A negative electrode current collecting part 24 is provided at the other end. A positive electrode current collecting member 50 is attached to the positive electrode current collecting part 22. A negative electrode current collecting member 60 is attached to the negative electrode current collecting part 24. The positive electrode current collecting member 50 constitutes a conductive path that electrically connects the positive electrode terminal 30 and the positive electrode of the electrode body 20. The negative electrode current collecting member 60 constitutes a conductive path that electrically connects the negative electrode terminal 40 and the negative electrode of the electrode body 20.

[0021] The film body 70 is disposed inside the case body 12 between the case body 12 and the electrode body 20. The film body 70 is insulating. The film body 70 has a volume resistivity of, for example, 1×10 13The film body 70 is made of a resin material having a volume resistivity of 1×10 15 It may be 1×10 Ωcm or more. 18 The film body 70 may have a resistivity of Ωcm or more. The material of the film body 70 may be the same as that of the conventional one, and is not particularly limited. The material of the film body 70 is preferably made of a resin material such as polypropylene (PP) or polyethylene (PE). The thickness (average thickness) of the film body 70 is not particularly limited, but is preferably 100 μm (0.1 mm) or more, and is preferably, for example, 110 to 200 μm.

[0022] FIG. 4 is a schematic perspective view of the film body 70. As shown in FIG. 4, the shape of the film body 70 here is a rectangular cylinder with one side (top) open and closed at the bottom. The film body 70 is formed, for example, by folding a single resin insulating sheet. The film body 70 has a rectangular bottom surface 70a, a pair of long side surfaces 70b extending from the long side of the bottom surface 70a and facing each other, and a pair of short side surfaces 70c extending from the short side of the bottom surface 70a and facing each other. The bottom surface 70a is a portion interposed between the bottom wall 12a of the case body 12 and the lower end of the electrode body 20. The long side of the bottom surface 70a is shorter than the long side of the bottom wall 12a of the case body 12.

[0023] The pair of long side surfaces 70b are portions interposed between the pair of long side walls 12b of the case body 12 and the pair of wide surfaces 20f of the electrode body 20. The pair of long side surfaces 70b extend along the long side walls 12b of the case body 12. It is preferable that a gap is provided between the long side surface 70b of the film body 70 and the long side wall 12b of the case body 12 (see FIG. 3). The pair of short side surfaces 70c are portions interposed between the pair of short side walls 12c of the case body 12 and both ends of the electrode body 20 in the winding axis direction. The pair of short side surfaces 70c extend along the short side walls 12c of the case body 12.

[0024] A notch N is provided at the upper end of the long side surface 70b along the long side direction Y. Here, the notch N is a half-cut process in which a notch is provided up to the middle of the thickness of the film body 70. The area above the notch N (i.e., the sealing plate 14 side) forms the folded portion 72. The notch N is a boundary line between the long side surface 70b and the folded portion 72. The provision of the notch N allows the folded portion 72 to be stably formed. However, the notch N is not essential, and in other embodiments, for example, a crease process that creates a crease for folding may be used. Furthermore, the boundary between the long side surface 70b and the folded portion 72 may be bent into an R-shape with a predetermined radius of curvature.

[0025] The bent portion 72 is bent so as to approach the electrode body 20. In other words, the bent portion 72 is bent toward the center of the short side direction X of the battery case 10. As shown in FIG. 3, the bent portion 72 extends obliquely upward (toward the sealing plate 14) from the long side surface 70b at a predetermined inclination angle θ. The bent portion 72 may have a length that does not interfere with the sealing plate 14. The bent portions 72 facing each other in the short side direction X may have a length that does not interfere with each other. The height H (length in the height direction Z in FIG. 3) of the bent portion 72 extending from the long side surface 70b may be, for example, 2 to 4 mm. The bent portion 72 is preferably spaced apart from the upper end of the electrode body 20. The bent portion 72 is a flat surface (inclined surface) here. The bent portion 72 is inclined so that the position of the bent portion 72 is toward the center of the short side direction X of the battery case 10 as it approaches the sealing plate 14 side. 3, the bent portion 72 is generally V-shaped, with the spacing narrowing toward the upper side (i.e., the sealing plate 14 side). One surface (outer surface) of the bent portion 72 faces the battery case 10 (more specifically, the sealing plate 14 or the long side wall 12b), and the other surface (inner surface) faces the electrode body 20.

[0026] Although details will be described later in the section on the manufacturing method, by providing the bent portion 72, even if high-temperature molten metal is generated as fine particles (so-called spatter) from the welded portion during laser welding and falls into the case body 12, the fallen molten metal can be isolated from the electrode body 20. In more detail, for example, the molten metal can be trapped on the outer surface of the film body 70, or sandwiched between the outer surface of the film body 70 and the inner surface of the long side wall 12b, to render it harmless. This makes it possible to prevent the molten metal from entering the electrode body 20 and causing the electrode body 20 to short-circuit.

[0027] In this embodiment, at least the folded portion 72 of the film body 70 is provided with a light diffusion portion (light scattering portion) LS that diffuses laser light. As shown in Fig. 3, the light diffusion portion LS is provided only on the surface (outer surface) of the film body 70 that faces the battery case 10. However, in other embodiments, the light diffusion portion LS may be provided only on the surface (inner surface) of the film body 70 that faces the electrode body 20, or may be provided on both sides of the film body 70.

[0028] As shown in FIG. 4, the light diffusion portion LS is provided from the bent portion 72 to a part of the long side surface 70b (near the bent portion 72). The light diffusion portion LS is not provided on the bottom surface 70a, the central to lower end portions of the long side surface 70b, and the short side surface 70c of the film body 70. Therefore, the bent portion 72 has a relatively high light diffusion property (e.g., a haze value measured by a haze meter) compared to the bottom surface 70a, the central to lower end portions of the long side surface 70b, and the short side surface 70c. However, in other embodiments, the light diffusion portion LS may be formed over the entire film body 70 by forming a composite material, for example, made of a resin and fine particles (such as inorganic filler) having a refractive index different from that of the resin, into a film shape by a conventionally known method.

[0029] By providing the light diffusion portion LS in the bent portion 72, even if the laser beam is lost during laser welding and enters the case body 12 through the gap between the case body 12 and the sealing plate 14, the laser beam is diffused by the light diffusion portion LS and changes its traveling direction in various directions. This reduces the beam density of the laser beam and disperses the heat of the laser beam. As a result, the film body 70 is less likely to melt due to the heat of the laser beam. Therefore, the laser beam is less likely to hit the electrode body 20, and the electrode body 20 is prevented from being burned or having an internal short circuit. In addition, when the bent portion 72 is separated from the electrode body 20, the heat of the laser beam can be prevented from being transmitted to the electrode body 20 at a high level.

[0030] In the evaluation of the diffusion of transmitted light by bringing a laser pointer into contact with the light diffusion section LS and irradiating it with red visible light (wavelength 600 nm), the diameter Φ2 of the light (transmitted light) transmitted through the light diffusion section LS is preferably 5 times or more, more preferably 10 times or more, of the diameter Φ1 of the incident light, when the diameter Φ1 (for example, Φ1 = 0.5 mm) of the light emitted from the laser pointer (incident light incident on the light diffusion section LS) is taken as a reference. This allows the heat of the laser light to be suitably dispersed, effectively reducing the amount of heat per unit area. Therefore, the film body 70 can be suppressed from melting at a high level, and the laser light can be prevented from hitting the electrode body 20. The diameter Φ2 of the transmitted light may be 20 times or less, or 15 times or less, of the diameter Φ1 of the incident light.

[0031] The light diffusion portion LS is a surface-roughened portion obtained by roughening the surface of the insulating film. In this specification, the term "roughening" refers to any process for forming fine irregularities (texture) on the film surface, including, for example, a process for roughening the surface with sandpaper or sandblasting, a process for irregularly scratching the surface with a sharp blade, an embossing process for imparting irregularities to the surface with an embossing roll, and a coating process for forming a layer containing inorganic filler by applying a paint containing inorganic filler and binder to the surface. By roughening the surface of the insulating film, the manufacturing process becomes easier and the manufacturing cost can be reduced, compared to the complicated configurations disclosed in, for example, Patent Documents 3 and 4.

[0032] The recesses are preferably nonlinear so as to randomly change the traveling direction of light. The protrusions may have various shapes such as semicircular or pyramidal. Although not particularly limited, the roughened surface portion has a ten-point average roughness Rz based on JIS B601-1994 of preferably 10 to 100 μm, more preferably 20 to 30 μm.

[0033] The light diffusion portion LS has a relatively large ten-point average roughness Rz compared to the bottom surface 70a, the central to lower end portions of the long side surfaces 70b, and the short side surfaces 70c. The light diffusion portion LS also has a relatively large surface roughness ratio (surface area ratio) compared to the bottom surface 70a, the central to lower end portions of the long side surfaces 70b, and the short side surfaces 70c. The surface roughness ratio is expressed as the ratio (surface area / area) of the area of ​​a specified region of the sample to the surface area caused by the surface shape.

[0034] In this embodiment, the light diffusion portion LS is a surface-roughened portion, but in other embodiments, the light diffusion portion LS may be other than a surface-roughened portion. The light diffusion portion LS may be, for example, a colored portion obtained by coloring (e.g., blackening) the surface of the insulating film, or may be provided by attaching a separate member having light diffusion properties (e.g., a commercially available laminate film, embossed film, reflective material, etc.) to the surface of the insulating film with an adhesive or the like. In this case, the thickness of the bent portion 72 after the separate member is attached may be, for example, 110 to 200 μm. This can suppress bending of the bent portion 72 and favorably maintain a state of being separated from the electrode body 20 during laser welding.

[0035] 3, in the height direction Z, the upper end of the bent portion 72 is located above the upper end of the electrode body 20 (i.e., on the sealing plate 14 side). The lower end (notch N) of the bent portion 72 is located below the upper end of the electrode body 20. However, for example, as disclosed in Patent Document 1, in cases where the electrode body 20 is a laminated electrode body, the notch N may be located above the upper end of the electrode body 20.

[0036] The inclination angle (bending angle) θ of the bent portion 72 with respect to the long side surface 70b is not particularly limited, but is preferably about 1° to 90°. In particular, it is preferably 5° or more, more preferably 10° or more, and further preferably 30° or more, 45° or more. The inclination angle θ may be 60° or more. By setting the inclination angle θ to a predetermined value or more, the upper end portion of the electrode body 20 can be widely covered by the bent portion 72. As a result, even if laser leakage occurs during laser welding and the laser light enters the case body 12 through the gap between the case body 12 and the sealing plate 14, the electrode body 20 can be protected from the laser light at a high level. In addition, even if the laser light is reflected inside the metal case body 12, the electrode body 20 can be protected from the reflected laser light.

[0037] The inclination angle θ is preferably less than 90° (acute angle). The inclination angle θ may be 80° or less, or 75° or less. By setting the inclination angle θ to a predetermined value or less, even if a metal foreign matter is mixed into the case body 12 during manufacturing, the mixed metal foreign matter is easily trapped on the outer surface of the film body 70, or between the outer surface of the film body 70 and the inner surface of the long side wall 12b. In other words, it is possible to prevent the metal foreign matter mixed into the case body 12 from rolling around the bent portion 72 and being mixed into the electrode body 20 through the gap between the bent portions 72 facing each other in the short side direction X.

[0038] <Method of manufacturing electricity storage device> The above-described power storage device 100 can be manufactured by a manufacturing method including, for example, a preparation step (S1), a housing step (S2), a laser welding step (S3), and a liquid injection step (S4), typically in this order. However, the liquid injection step is not essential, and can be omitted, for example, when a solid electrolyte is used instead of a nonaqueous electrolyte. The order of the housing step, the laser welding step, and the liquid injection step may be, for example, that the liquid injection step comes first. The manufacturing method of this embodiment may also include steps other than those described above at any stage. Each step will be described below.

[0039] In the preparation step (S1), a battery case 10 (case body 12 and sealing plate 14), an electrode body 20, a non-aqueous electrolyte, and a film body 70 are prepared. The battery case 10, the electrode body 20, and the non-aqueous electrolyte are as described above. The sealing plate 14 of the battery case 10 is integrated with the electrode body 20 in advance. That is, the positive electrode terminal 30 and the negative electrode terminal 40 are attached to the sealing plate 14 by crimping. A positive electrode current collecting member 50 is attached to the positive electrode current collecting portion 22 of the electrode body 20, and a negative electrode current collecting member 60 is attached to the negative electrode current collecting portion 24. The positive electrode current collecting member 50 is welded to the positive electrode terminal 30, and the negative electrode current collecting member 60 is welded to the negative electrode terminal 40.

[0040] According to the knowledge of the present inventor, processing errors may occur in the case body 12 and the sealing plate 14 prepared in this step. For example, the case body 12 may have a deviation in plate thickness, or may bend due to stress when forming the opening 12h (at the time of trimming). The sealing plate 14 may have a deviation in plate thickness, or may bend due to stress when cutting, or may be crushed and expanded when the positive electrode terminal 30 and the negative electrode terminal 40 are crimped. These processing errors may easily cause laser chipping in the laser welding step (S3) described later.

[0041] FIG. 5 is a schematic diagram of an insulating film constituting the film body 70 of FIG. 4. That is, it is a development view of the film body 70 of FIG. 4. The film body 70 of FIG. 4 is composed of the insulating film of FIG. 5. The insulating film of FIG. 5 can be prepared, for example, as follows. That is, first, an insulating film is cut out from a single strip-shaped resin sheet into a shape (outer dimensions) that conforms to the outer shape of FIG. 5. This outer dimension may be the same as that of a conventional one. Next, a crease process (for example, a groove process or a perforation process) for folding molding is performed at the positions of the broken lines in FIG. 5. In addition, a linear half-cut process is performed at the upper end and lower end of FIG. 5, at positions that will be positioned upward after folding, to form a cut N. In the upper end and lower end of FIG. 5, the height H from the cut N to the upper end or lower end is 3 mm here.

[0042] Furthermore, the region from the cut N of the insulating film to the upper end or lower end is roughened to form a roughened surface portion (light diffusion portion LS). The roughening treatment may be performed on the strip-shaped resin sheet or before the above-mentioned crease processing or half-cut processing is performed. By providing a roughened surface portion by performing surface processing on a single insulating film in this way, manufacturing is easier and manufacturing costs can be reduced compared to methods using a separate member as described in, for example, Patent Documents 3 and 4. In this manner, an insulating film (film body 70) as shown in FIG. 5 can be prepared.

[0043] Next, with the bottom surface portion B of the insulating film facing the lower end portion of the electrode body 20, the insulating film is folded along the dotted line to cover both end surfaces of the electrode body 20 and the pair of wide surfaces 20f with the film body 70. Then, the folding portion 72 (light diffusion portion LS) is folded along the cut N toward the electrode body 20 at a predetermined inclination angle θ to form the folding portion 72. Although not particularly limited, the inclination angle of the folding portion 72 is preferably an acute angle (less than 90°), particularly 45° or more and less than 90°. As a result, the folding portion 72 is in a position extending from the long side surface 70b of the film body 70 toward the sealing plate 14 side in the height direction Z of the case body 12 and toward the inside of the short side direction X of the case body 12. In this manner, the insulating film of FIG. 5 can be formed into the film body 70 having the outer shape as shown in FIG. 4 and integrated with the electrode body 20.

[0044] In the accommodation step (S2), the electrode body 20 and the film body 70 are accommodated inside the case body 12. Specifically, the electrode body 20 covered with the film body 70 and fixed to the sealing plate 14 is inserted into the internal space of the case body 12 from the opening 12h. This allows the film body 70 to be interposed between the case body 12 and the electrode body 20. For example, the long side surfaces 70b of the film body 70 can be interposed between the long side walls 12b of the case body 12 and a pair of wide surfaces 20f of the electrode body 20.

[0045] When the electrode body 20 and the film body 70 are housed in the case body 12, the sealing plate 14 may come into contact with the inner wall of the case body 12, causing edges of the sealing plate 14 or the case body 12 to be scraped off, resulting in the generation of metallic foreign matter. However, with the technology disclosed herein, even if the generated metallic foreign matter falls into the case body 12, the fallen metallic foreign matter can be trapped on the outer surface of the film body 70, or sandwiched between the outer surface of the film body 70 and the inner surface of the long side wall 12b, and isolated from the electrode body 20. This makes it possible to prevent the metallic foreign matter from entering the electrode body 20 and causing the electrode body 20 to short-circuit.

[0046] In the laser welding step (S3), the sealing plate 14 is placed in the opening 12h of the case body 12. Then, the outer peripheral edge of the sealing plate 14 is laser-welded to the inner peripheral edge of the opening 12h of the case body 12 over the entire circumference. The conditions for irradiating the laser light (for example, the output, the beam diameter, the processing speed (the scanning speed of the laser light), etc.) may be the same as those in the past. When irradiating the laser light, a gap of about several tens of μm may be generated between the outer peripheral edge of the sealing plate 14 and the inner peripheral edge of the opening 12h of the case body 12 due to processing errors, etc. However, in the technology disclosed herein, at least the bending portion 72 is provided with a light diffusion portion LS. As a result, even if laser leakage occurs during laser welding and the laser light enters the case body 12 through the gap between the case body 12 and the sealing plate 14, the laser light can be diffused by the light diffusion portion LS. As a result, the beam density of the laser light is reduced and the heat of the laser light is dispersed, so that the film body 70 is less likely to melt. As a result, the electrode body 20 is less likely to be hit by the laser light, and the electrode body 20 can be prevented from being burned or having an internal short circuit.

[0047] Furthermore, when the bent portion 72 is spaced apart from the upper end of the electrode body 20, it is possible to prevent, to a high degree, the heat of the laser from being transmitted to the electrode body 20. Furthermore, in the technology disclosed herein, even if high-temperature molten metal is generated as fine particles (so-called sputters) from the welded portion during laser welding and falls into the case body 12, the fallen molten metal can be isolated from the electrode body 20. Therefore, without using a separate member as described in, for example, Patent Documents 3 and 4, the film body 70 alone can simultaneously suppress the occurrence of scorching of the electrode body 20 due to laser penetration and the occurrence of a short circuit due to the inclusion of molten metal.

[0048] The technology disclosed herein is particularly effective when there is a large gap (e.g., 70 μm or more, or even 90 μm or more) that exceeds the beam diameter between opening 12h of case body 12 and sealing plate 14. Alternatively, it is particularly effective when a high-output laser beam (e.g., 1000 W or more laser beam) is used to shorten the time required for laser welding.

[0049] In the liquid injection step (S4), a nonaqueous electrolyte is injected into the inside of the case body 12 through an injection hole (not shown) provided in the sealing plate 14. Then, the injection hole is sealed with a liquid injection plug or the like. In this manner, the electricity storage device 100 as shown in FIGS. 1 to 3 can be manufactured.

[0050] Note that after the laser welding process (for example, the state of the electricity storage device 100 after this process), the inclination angle θ may have become smaller since the laser welding due to changes over time, or may have increased since the laser welding due to the weight of the nonaqueous electrolyte, etc.

[0051] <Applications of electricity storage devices> The electricity storage device 100 can be used for various purposes, but is particularly preferably used as a large-scale (large-capacity) electricity storage device having a large battery case 10 and high energy density. Suitable applications include, for example, a power source for a motor (power source for driving a vehicle) mounted on a vehicle such as a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), or a battery electric vehicle (BEV).

[0052] Although the specific examples of the present invention have been described in detail above, the above-mentioned embodiments are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

[0053] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A metal case body having a rectangular bottom wall, a pair of long side walls extending from a long side of the bottom wall and facing each other, a pair of short side walls extending from a short side of the bottom wall and facing each other, and an opening facing the bottom wall; a metal sealing plate disposed within the opening of the case body and having an outer periphery portion laser-welded to an inner periphery portion of the opening of the case body; an electrode body housed in the case body and having a pair of wide surfaces facing the long side walls; and an insulating film body interposed between the electrode body and the case body, wherein the film body is disposed between the pair of long side walls of the case body and the pair of wide surfaces of the electrode body, a film body having a pair of long side surfaces interposed between the film body and extending along the long side walls, and folding portions extending from each of the pair of long side surfaces toward the sealing plate and folded so as to approach the electrode body, wherein at least the folding portions are provided with a light diffusion portion that diffuses laser light, the method for manufacturing an electricity storage device including: a preparation step of preparing the film body; an accommodating step of accommodating the electrode body and the film body inside the opening of the case body; and a laser welding step of placing the sealing plate in the opening of the case body and laser welding the outer peripheral edge portion of the sealing plate to the case body. Item 2: The method for producing an electricity storage device according to item 1, wherein in the preparation step, an insulating film is prepared as the film body, and the light diffusion portion is formed by roughening a surface of the insulating film. Item 3: The method for producing an electricity storage device according to item 1 or 2, wherein in the preparing step, an inclination angle of the bent portion with respect to the long side surface is set to be equal to or greater than 45° and less than 90°. Clause 4: An electricity storage device comprising: a metal case body having a rectangular bottom wall, a pair of long side walls extending from a long side of the bottom wall and facing each other, a pair of short side walls extending from a short side of the bottom wall and facing each other, and an opening facing the bottom wall; a metal sealing plate disposed in the opening of the case body and having an outer peripheral edge portion laser welded to an inner peripheral edge portion of the opening of the case body; an electrode body housed in the case body and having a pair of wide surfaces facing the long side walls; and an insulating film body interposed between the electrode body and the case body, wherein the film body is interposed between the pair of long side walls of the case body and the pair of wide surfaces of the electrode body, respectively, and has a pair of long side surfaces extending along the long side walls, and a folding portion extending from each of the pair of long side surfaces toward the sealing plate and folded so as to approach the electrode body, and at least the folding portion is provided with a light diffusion portion that diffuses laser light. Item 5: The electricity storage device according to item 4, wherein the film body is made of an insulating film, and the light diffusion portion is a roughened surface portion obtained by roughening the surface of the insulating film. Item 6: The electricity storage device according to item 4 or 5, wherein an inclination angle of the bent portion with respect to the long side surface is equal to or greater than 45° and less than 90°. [Explanation of symbols]

[0054] 10 Battery case 12 Case body 12b Long side wall 12h opening 14 Sealing plate 20 Electrode body 20f Wide surface 70 Film body 70b long side 72 Bending section 100 Energy storage device

Claims

1. a metal case body having a rectangular bottom wall, a pair of long side walls extending from long sides of the bottom wall and facing each other, a pair of short side walls extending from short sides of the bottom wall and facing each other, and an opening facing the bottom wall; a metal sealing plate disposed within the opening of the case body, the outer peripheral edge of which is laser welded to an inner peripheral edge of the opening of the case body; an electrode body housed in the case body and having a pair of wide surfaces facing the long side wall; an insulating film body interposed between the electrode body and the case body; Equipped with The film body is a pair of long side surfaces respectively interposed between the pair of long side walls of the case body and the pair of wide surfaces of the electrode body and extending along the long side walls; Bending portions extending from the pair of long side surfaces toward the sealing plate and bending the electrode assembly toward the sealing plate; having At least the bent portion is provided with a light diffusion portion for diffusing the laser light. A method for manufacturing an electricity storage device, comprising: a preparation step of preparing the film body; a housing step of housing the electrode body and the film body inside the case main body; a laser welding step of placing the sealing plate in the opening of the case body and laser welding the outer peripheral edge portion of the sealing plate to the case body; Including, In the preparation step, an insulating film is prepared as the film body, and the light diffusion portion is formed by roughening a surface of the insulating film. A method for manufacturing an electricity storage device.

2. In the preparation step, an inclination angle of the bent portion with respect to the long side surface is set to be equal to or greater than 45° and less than 90°. A method for producing the electricity storage device according to claim 1 .

3. a metal case body having a rectangular bottom wall, a pair of long side walls extending from long sides of the bottom wall and facing each other, a pair of short side walls extending from short sides of the bottom wall and facing each other, and an opening facing the bottom wall; a metal sealing plate disposed within the opening of the case body, the outer peripheral edge of which is laser welded to an inner peripheral edge of the opening of the case body; an electrode body housed in the case body and having a pair of wide surfaces facing the long side wall; an insulating film body interposed between the electrode body and the case body; Equipped with The film body is made of an insulating film, a pair of long side surfaces respectively interposed between the pair of long side walls of the case body and the pair of wide surfaces of the electrode body and extending along the long side walls; Bending portions extending from the pair of long side surfaces toward the sealing plate and bending the electrode assembly toward the sealing plate; having At least the bent portion is provided with a light diffusion portion that diffuses the laser light, The light diffusion portion is a surface roughened portion obtained by roughening the surface of the insulating film. Energy storage device.

4. The inclination angle of the bent portion with respect to the long side surface is equal to or greater than 45° and less than 90°. The electricity storage device according to claim 3 .

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