Power storage device and method for manufacturing the same

Abstract

To provide a power storage device manufacturing method and a power storage device that have reliability of dimensional accuracy by suppressing protrusion of a fusion solidified part to outward of the outer package.SOLUTION: A power storage device 100 disclosed here comprises: an outer package 12 that has an electrode body having an electrode, a bottom part, a side wall 12a extending from a peripheral edge of the bottom part, and an opening 15 enclosed by the side wall 12a and that accommodates the electrode body; an aperture sealing plate 18 that seals the opening 15; and an annular fusion solidified part 50 that is formed in a fitting part 11 of the opening 15 of the outer package 12 and the aperture sealing plate 18. Meanwhile, as the power storage device 100 has a protrusion preventing layer 60 in at least some of the peripheral edges of the opening 15 of the outer package 12, it can be prevented that the fusion solidified part 50 is formed outward of the outer package 12.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a power storage device and a method for manufacturing the power storage device.

Background Art

[0002] In recent years, power storage devices such as lithium-ion secondary batteries have been suitably used for portable power sources such as personal computers and mobile terminals, and power sources for vehicle drive such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). Conventionally, there is known a power storage device having an exterior body having a bottom, side walls extending from the periphery of the bottom, and an opening surrounded by the side walls, and a sealing plate for sealing the opening, and having a molten solidified portion at a fitting portion between the exterior body and the sealing plate. For example, Patent Document 1 discloses a manufacturing method characterized by offsetting the spot center of a laser beam inside the fitting portion. Further, Patent Document 2 discloses a technique characterized in that, for the purpose of the stability of the shape of a bead (molten solidified portion), the thickness of the upper part of the side wall of a case (exterior body) is partially thickened in advance so as to project toward the inside of the case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a conventional power storage device, the dimensions of the power storage device become unstable due to the protrusion of the melt-solidified portion outside the outer casing. As the power storage device becomes more widespread, stability of dimensional accuracy is required, and high reliability such as stability of welding quality and increased energy is demanded. Therefore, the inventor believes that it is desirable to suppress the protrusion of the melt-solidified portion of the power storage device outside the outer casing without changing the welding conditions or the inner dimensions of the outer casing.

[0005] The technology disclosed herein has been made in view of the above circumstances, and its object is to provide a power storage device and a method for manufacturing a power storage device that have reliability of dimensional accuracy by suppressing the protrusion of the melt-solidified portion outside the outer casing.

Means for Solving the Problems

[0006] The technology disclosed herein relates to a power storage device including an electrode body having an electrode, a bottom portion, a side wall extending from a periphery of the bottom portion, and an opening surrounded by the side wall, an outer casing that houses the electrode body, a sealing plate that seals the opening, and an annular melt-solidified portion formed at a fitting portion between the opening of the outer casing and the sealing plate. And the power storage device disclosed herein has a protrusion preventing layer that prevents the melt-solidified portion from being formed outside the outer casing at at least a part of the periphery of the opening of the outer casing.

[0007] According to such a configuration, when the melt-solidified portion is formed, the protrusion of the melt-solidified portion outside the outer casing is suppressed by the protrusion preventing layer. Therefore, a power storage device having reliability of dimensional accuracy is provided.

Brief Description of the Drawings

[0008]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments according to the technology disclosed herein will be described with reference to the drawings. Matters not mentioned in this specification but necessary for the implementation of 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 the common general knowledge in the relevant field. Also, in the following drawings, members and parts having the same function are denoted by the same reference numerals and described. In addition, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. In this specification, a numerical range expressed as "A to B" includes A and B, and also includes the meaning of "preferably greater than A" and "preferably less than B". Also, in this specification, the "main component" refers to a component that occupies 70% by weight or more of all components.

[0010] As used herein, the term "electric energy storage device" refers to a device that can be charged and discharged. Electric energy storage devices generally include batteries such as lithium ion batteries and lithium secondary batteries, as well as lithium polymer batteries, lithium ion capacitors, and the like. A secondary battery generally refers to a battery that can be repeatedly charged and discharged with the movement of charge carriers between the positive and negative electrodes. Here, as an example of an electric energy storage device, a lithium ion secondary battery is illustrated.

[0011] <Electric energy storage device 100> FIG. 1 is a perspective view schematically showing an electric energy storage device 100 according to the first embodiment. FIG. 2 is a schematic longitudinal sectional view taken along line II-II in FIG. 1. FIG. 3 is a top view schematically showing the outer package 12 and the sealing plate 18. In FIGS. 2 and 3, the outer package 12 and the sealing plate 18 are before being welded (before the molten solidified portion 50 is formed). In the following description, the reference signs L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, upper, and lower, respectively. The reference sign X in the drawings indicates the short side direction (also referred to as the thickness direction) of the electric energy storage device 100, the reference sign Y indicates the long side direction of the electric energy storage device 100, and the reference sign Z indicates the vertical direction (also referred to as the height direction) of the electric energy storage device 100. However, these are merely directions for convenience of explanation and do not limit the installation form of the electric energy storage device 100 in any way.

[0012] As shown in FIGS. 1 and 2, the electric energy storage device 100 includes a case 1, an electrode body 20, a positive electrode terminal 6, a negative electrode terminal 8, a positive electrode current collecting member 35, and a negative electrode current collecting member 45. Although not shown, the electric energy storage device 100 further includes an electrolytic solution here. The electric energy storage device 100 is characterized by including the anti-overflow layer 60 disclosed herein, and the other configurations may be the same as those of the prior art. The electric energy storage device 100 is preferably a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

[0013] Case 1 is a housing that houses the electrode body 20. As shown in FIGS. 1 and 2, Case 1 includes an exterior body 12 having an opening 15 and a sealing plate 18 that seals the opening 15. The exterior body 12 and the sealing plate 18 have sizes corresponding to the number (one or more) of electrode bodies 20 to be housed, the size, etc. Case 1 is preferably made of metal, and more preferably made of aluminum or an aluminum alloy mainly composed of aluminum. Here, Case 1 is made of aluminum. As shown in FIG. 1, Case 1 has a substantially rectangular parallelepiped shape (square shape) that is flat and bottomed here. However, it is not limited to this, and the shape of Case 1 may be, for example, a cylindrical shape or the like.

[0014] As shown in FIGS. 1 and 2, the exterior body 12 is a bottomed and substantially rectangular parallelepiped container having an opening 15 on one side (here, the upper surface). As shown in FIG. 1, the exterior body 12 includes a substantially rectangular bottom 12d having a pair of short sides and a pair of long sides, a pair of short side walls 12a and 12b that extend upward from the short sides of the bottom 12d and face each other, and a pair of long side walls 12e and 12f that extend upward from the long sides of the bottom 12d and face each other. In addition, in this specification, the term "substantially rectangular shape" includes, in addition to a perfect rectangular shape (rectangular shape), for example, a shape in which the corners connecting the long side and the short side of the rectangular shape are R-shaped, a shape having a notch at the corner, and the like. The short side walls 12a and 12b and the long side walls 12e and 12f are an example of the "side walls" disclosed here.

[0015] An opening 15 surrounded by a pair of short side walls 12a and 12b and a pair of long side walls 12e and 12f is formed on one side surface of the exterior body 12. As shown in FIG. 2, the bottom 12d faces the opening 15. As shown in FIG. 2, here, the exterior body 12 has an upper end surface 13. The upper end surface 13 has a pair of short side portions 13a and 13b and a pair of long side portions 13e and 13f (see FIG. 3). The short side portions 13a and 13b are the upper edges of the short side walls 12a and 12b. The long side portions 13e and 13f are the upper edges of the long side walls 12e and 12f. Further, here, the exterior body 12 has a peripheral edge portion 16 where the outer surfaces of the short side walls 12a and 12b and the long side walls 12e and 12f intersect with the upper end surface 13.

[0016] As shown in FIGS. 1 and 2, the sealing plate 18 is a member that seals the opening 15 of the exterior body 12. Here, the sealing plate 18 is a plate-shaped member with a substantially rectangular plane. As shown in FIG. 2, the sealing plate 18 is provided with a liquid injection hole 71, a gas discharge valve 73, and terminal lead-out holes 74 and 75. The sealing plate 18 faces the bottom 12d of the exterior body 12. Although details will be described later, in the case 1, the opening 15 of the exterior body 12 and the sealing plate 18 are fitted together, and the fitting portion 11 is welded and joined, thereby being integrated. As a result, the case 1 is hermetically sealed.

[0017] The liquid injection hole 71 is a through hole for injecting an electrolytic solution into the case 1 after the sealing plate 18 is assembled to the exterior body 12. Here, the liquid injection hole 71 is sealed by a sealing member 72 after the injection of the electrolytic solution. The gas discharge valve 73 is a thin-walled portion configured to break when the pressure in the case 1 reaches a predetermined value or more and discharge the gas in the case 1 to the outside.

[0018] As the electrolytic solution, those conventionally known and used can be used without particular limitation. As an example, a non-aqueous electrolytic solution in which a supporting salt (electrolyte salt) is dissolved in a non-aqueous solvent (organic solvent) is preferably used. As an example of the non-aqueous solvent, carbonate solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate can be mentioned. As an example of the supporting salt, fluorine-containing lithium salts such as LiPF6 can be mentioned. The electrolytic solution may contain additives as necessary.

[0019] The positive electrode terminal 6 is attached to one end (the left end in FIG. 2) in the long side direction Y of the sealing plate 18. The negative electrode terminal 8 is attached to the other end (the right end in FIG. 2) in the long side direction Y of the sealing plate 18. As shown in FIG. 2, the positive electrode terminal 6 and the negative electrode terminal 8 are inserted through the terminal lead-out holes 74 and 75 and exposed on the outer surface of the sealing plate 18. As shown in FIG. 2, the positive electrode terminal 6 is electrically connected to the positive electrode 3 of the electrode body 20 via the positive electrode current collecting member 35 inside the outer package 12. The negative electrode terminal 8 is electrically connected to the negative electrode 4 of the electrode body 20 via the negative electrode current collecting member 45 inside the outer package 12. The positive electrode terminal 6 and the negative electrode terminal 8 are insulated from the sealing plate 18 by the gasket 76 and the insulator 78. Also, a current interruption mechanism (CID) may be installed between the positive electrode terminal 6 and the positive electrode current collecting member 35 or between the negative electrode terminal 8 and the negative electrode current collecting member 45.

[0020] The positive electrode terminal 6 is preferably made of metal, more preferably made of, for example, aluminum or an aluminum alloy. The negative electrode terminal 8 is preferably made of metal, more preferably made of, for example, copper or a copper alloy. The negative electrode terminal 8 may be configured by joining and integrating two conductive members. For example, the portion connected to the negative electrode current collecting member 45 may be made of copper or a copper alloy, and the portion exposed on the outer surface of the sealing plate 18 may be made of aluminum or an aluminum alloy.

[0021] For the gasket 76 and the insulator 78, a material excellent in chemical resistance and weather resistance is preferably used. The gasket 76 and the insulator 78 may be made of a resin material having electrical insulation properties and capable of elastic deformation, for example, a fluorinated resin such as perfluoroalkoxy fluororesin (PFA), polyphenylene sulfide resin (PPS), aliphatic polyamide, etc.

[0022] Here, the positive electrode terminal 6 is electrically connected to the plate-shaped positive electrode external conductive member 36 outside the case 1. Similarly, the negative electrode terminal 8 is electrically connected to the plate-shaped negative electrode external conductive member 46 outside the case 1. The positive electrode external conductive member 36 and the negative electrode external conductive member 46 are connected to other power storage devices or external devices via an external connection member such as a bus bar. The positive electrode external conductive member 36 and the negative electrode external conductive member 46 are preferably made of a metal excellent in conductivity such as aluminum, aluminum alloy, copper, or copper alloy. However, the positive electrode external conductive member 36 and the negative electrode external conductive member 46 are not essential and can be omitted in other embodiments.

[0023] The electrode body 20 may be the same as in the prior art and is not particularly limited. As shown in FIG. 2, the electrode body 20 has a positive electrode 3 and a negative electrode 4. Here, the electrode body 20 is a flat wound electrode body in which a strip-shaped positive electrode 3 and a strip-shaped negative electrode 4 are laminated in an insulated state via a strip-shaped separator 7 and wound around a winding axis. However, the electrode body 20 may be a laminated electrode body in which a rectangular (typically rectangular) positive electrode 3 and a rectangular (typically rectangular) negative electrode 4 are stacked in an insulated state. Also, the number of electrode bodies 20 disposed inside one exterior body 12 is not particularly limited and may be two or more (plural). Note that the positive electrode 3 and the negative electrode 4 are examples of the "electrode" in the technology disclosed herein.

[0024] As shown in FIG. 2, the positive electrode 3 has a positive electrode current collector 30 and a positive electrode active material layer 31 fixed on the positive electrode current collector 30. The positive electrode current collector 30 is made of a conductive metal such as aluminum, aluminum alloy, nickel, or stainless steel, for example. The positive electrode active material layer 31 is a layer containing a positive electrode active material (for example, a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide) capable of reversibly occluding and releasing charge carriers.

[0025] The negative electrode 4 has a negative electrode current collector 40 and a negative electrode active material layer 41 fixed on the negative electrode current collector 40. The negative electrode current collector 40 is made of a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode active material layer 41 is a layer containing a negative electrode active material (such as a carbon material like graphite) that can reversibly occlude and release charge carriers.

[0026] The separator 7 is a member that insulates the positive electrode active material layer 31 of the positive electrode 3 and the negative electrode active material layer 41 of the negative electrode 4. As the separator 7, for example, a porous resin sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. Note that a heat resistance layer (HRL) containing an inorganic filler may be provided on the surface of the separator 7.

[0027] As shown in FIG. 2, at the left end of the electrode body 20 in the long side direction Y, a part of the positive electrode current collector 30 where the positive electrode active material layer 31 is not formed (positive electrode current collector exposed portion) protrudes from the laminated portion. A positive electrode current collecting member 35 is attached to the positive electrode current collector exposed portion. The positive electrode current collecting member 35 may be made of the same metal material as the positive electrode current collector 30, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Also, at the right end of the electrode body 20 in the long side direction Y, a part of the negative electrode current collector 40 where the negative electrode active material layer 41 is not formed (negative electrode current collector exposed portion) protrudes from the laminated portion. A negative electrode current collecting member 45 is attached to the negative electrode current collector exposed portion. The material (metal type) of the negative electrode current collecting member 45 may be different from that of the positive electrode current collecting member 35. The negative electrode current collecting member 45 may be made of the same metal type as the negative electrode current collector 40, for example, a conductive metal such as copper, a copper alloy, nickel, or stainless steel.

[0028] The power storage device 100 is configured by fitting an exterior body 12 and a sealing plate 18 and welding such a fitting portion 11. Here, the sealing plate 18 and the exterior body 12 (upper end surface 13) are flush in a plan view. Specifically, as shown in FIG. 3, the outer peripheral surface of the sealing plate 18 and the inner surface of the exterior body 12 (opening 15) are arranged (fitted) so as to face each other at the fitting portion 11. Then, by laser-welding the fitting portion 11 over the entire circumference, an annular fusion-solidified portion 50 is formed and the sealing plate 18 and the exterior body 12 are joined (see FIGS. 4 and 9).

[0029] FIG. 9 is a longitudinal sectional view showing the vicinity of the fusion-solidified portion 50 according to the conventional example. By the way, when performing the above welding, as shown in FIG. 9, a part of the sealing plate 18 and the exterior body 12 (shown by a virtual line) melts, and the fusion-solidified portion 50 is formed by the solidification of such a molten portion. The shape of the fusion-solidified portion 50 is determined by, for example, the flow of the molten metal and the influence of surface tension. More specifically, the fusion-solidified portion 50 is formed by solidifying in a shape swelled by the surface tension of the molten metal. Therefore, as shown in FIG. 9, there is a possibility that a part of the fusion-solidified portion 50 protrudes outward (projects) from the exterior body 12. Due to such protrusion of the fusion-solidified portion 50, there is a variation in the size of the power storage device 100 (case 1) in the long side direction Y and the short side direction X. Note that “formed (protruding) outside the exterior body” in this specification means that at least a part of the fusion-solidified portion 50 protrudes in the long side direction Y or the short side direction X from the exterior body 12. The protrusion of at least a part of the fusion-solidified portion 50 in the up-down Z direction is not included in “protruding outward”.

[0030] The power storage device 100 disclosed here is created in view of the above-described problems and is characterized by including a protrusion prevention layer 60. FIG. 4 is a longitudinal sectional view showing the vicinity of the fusion-solidified portion 50 according to an embodiment. FIG. 4 is a figure corresponding to FIG. 9 showing the conventional example. In FIG. 4, for convenience of explanation, the exterior body 12 and the sealing plate 18 before the formation of the fusion-solidified portion 50 (before laser irradiation) are shown by virtual lines.

[0031] In the technology disclosed herein, the power storage device 100 includes a protrusion prevention layer 60 at at least a part of the periphery of the opening 15. The protrusion prevention layer 60 is a layer having a melting point higher than that of the melt solidified portion 50. As shown in FIG. 4, the protrusion prevention layer 60 is formed here on the outer surface of the short side wall 12a of the outer package 12. The upper end (U side) of the protrusion prevention layer 60 is arranged here so as to reach the peripheral portion 16. In the present specification, the "periphery of the opening" refers to a part of the outer surfaces of the short side walls 12a, 12b and the long side walls 12e, 12f of the outer package 12 and a part of the upper end surface 13.

[0032] As described above, when the power storage device 100 in the present embodiment is configured, by irradiating the fitting portion 11 between the outer package 12 and the sealing plate 18 with the laser L (see FIG. 6), a part of the outer package 12 and the sealing plate 18 melts (see FIG. 4). When the melt solidified portion 50 is formed from such a melted portion, a part of the melt solidified portion 50 tends to be formed (protrude) outward of the outer package 12 due to the surface tension of the melted portion or the like. On the other hand, the melting point of the protrusion prevention layer 60 is higher than the melting point of the melt solidified portion 50. Thereby, the protrusion prevention layer 60 has a role of suppressing the melt solidified portion 50 from protruding outward (in the long side direction Y in FIG. 4) from the outer package 12. Therefore, it is possible to prevent a part of the melt solidified portion 50 from protruding outward from the outer package 12.

[0033] The material of the overflow prevention layer 60 can be appropriately selected according to the material (melting point) of the case 1 (the exterior body 12 and the sealing plate 18), the irradiation intensity of the laser, etc. Although not limited thereto, for example, when the case 1 is made of aluminum or an aluminum alloy, the overflow prevention layer 60 can have a melting point of about 800 °C or higher, preferably about 850 °C or higher. For example, the overflow prevention layer 60 can be made of aluminum oxide (e.g., alumina, boehmite, bayerite, etc.), ceramic, electroless nickel plating, electroless nickel-ceramics plating, diamond-like carbon (DLC) coating, intrinsic carbon film (ICF) coating, cermet spraying, cemented carbide spraying (WC), iron-based amorphous spraying, etc. Preferably, aluminum oxide, ceramic, electroless nickel plating, diamond-like carbon (DLC) coating, intrinsic carbon film (ICF) coating, etc. can be adopted. More preferably, aluminum oxide, electroless nickel plating can be adopted.

[0034] From the viewpoint of exhibiting the effect of suppressing the overflow of the molten solidified portion 50, the thickness of the overflow prevention layer 60 is preferably 0.1 μm or more, more preferably 1.0 μm or more. On the other hand, from the viewpoint of the dimensional accuracy of the exterior body 12, it is preferably 100 μm or less, more preferably 50 μm or less. Also, the height of the overflow prevention layer 60 as viewed from the thickness direction (vertical direction Z) of the sealing plate 18 can be appropriately adjusted according to the laser intensity during laser welding and the material (melting point) of the case 1. From the viewpoint of exhibiting the effect of suppressing the overflow of the molten solidified portion 50 to the outside of the exterior body 12, the height of the overflow prevention layer is preferably 0.8 mm or more, more preferably 0.9 mm or more.

[0035] Here, as shown in FIG. 3, the exterior body 12 has R portions 12g, 12h, 12i, 12j provided between the short side walls 12a, 12b and the long side walls 12e, 12f. Here, the overflow prevention layer 60 is also arranged on the R portions 12g, 12h, 12i, 12j of the exterior body 12. Even in the case of adopting such a configuration, the effect of suppressing the overflow of the molten solidified portion 50 to the outside of the exterior body 12 can be exhibited. However, such a configuration is not essential and can be omitted.

[0036] The overflow prevention layer 60 is disposed here along the entire circumference of the periphery of the opening 15. However, it is not limited to this, and it is not necessarily required to dispose the overflow prevention layer 60 along the entire circumference. For example, the overflow prevention layer 60 may be disposed only on the short side walls 12a and 12b of the exterior body 12. According to such a configuration, the overflow of the melt-solidified portion 50 in the long side direction Y with respect to the exterior body 12 is suppressed. Thereby, the dimensional deviation of the power storage device 100 due to the melt-solidified portion 50 in the long side direction Y can be preferably suppressed. Further, the overflow prevention layer 60 may be disposed only on the long side walls 12e and 12f of the exterior body 12. According to such a configuration, the overflow of the melt-solidified portion 50 in the long side direction Y with respect to the exterior body 12 is suppressed. Thereby, the dimensional deviation of the power storage device 100 due to the melt-solidified portion 50 in the short side direction X can be preferably suppressed.

[0037] <Manufacturing Method of Power Storage Device 100> As described above, the structure of the power storage device 100 according to the present embodiment has been described. On the other hand, as another aspect of the technology disclosed herein, a manufacturing method of the power storage device 100 is provided. FIG. 5 is a flowchart showing a manufacturing method of the power storage device 100 according to an embodiment. The manufacturing method of the power storage device 100 is characterized by performing an anti-layer formation step S10. The power storage device 100 disclosed herein can be manufactured by a manufacturing method including an anti-layer formation step S10, a sealing plate fitting step S20, and a laser welding step S30. In the manufacturing method of the power storage device 100 disclosed herein, in addition to the above steps, other steps may be further included at an arbitrary stage, and other manufacturing processes may be the same as those in the prior art.

[0038] (Anti-layer Formation Step S10) In the anti-overhang layer forming step S10, an anti-overhang layer 60 is formed on at least a part of the periphery of the opening 15 of the exterior body 12. The process that can be used to form the anti-overhang layer 60 in the anti-overhang layer forming step is not particularly limited. For example, it includes aluminum oxide film treatment such as anodizing treatment, boehmite treatment, or bayrite treatment, ceramic coating treatment such as ceramic spraying, glass coating treatment, DLC (Diamond-like Carbon) coating treatment, true carbon film (ICF) coating treatment, electroless nickel plating treatment, and the like. When the exterior body 12 is made of aluminum or an aluminum alloy, the anti-overhang layer forming step S10 can preferably employ anodizing treatment. By performing anodizing treatment, an aluminum oxide film as the anti-overhang layer 60 having a high melting point (about 2000 °C) can be formed.

[0039] The method of anodizing treatment may be the same as the conventionally known treatment. For example, first, masking is performed on the portion of the exterior body 12 where the anti-overhang layer 60 is not to be formed. Here, masking is performed on the inner surface and the upper end surface 13 of the opening 15. Next, the periphery of the opening 15 of the exterior body 12 is immersed in an anodizing treatment solution to perform aluminum anodizing treatment. Thereafter, the anti-overhang layer 60 can be formed by removing the masking portion. Note that the thickness of the anti-overhang layer 60 can be adjusted by controlling factors such as the anodizing treatment solution, temperature, voltage, and treatment time. Also, the formation region of the anti-overhang layer 60 can be adjusted, for example, by the masking location of the exterior body 12 or the immersion depth of the anodizing treatment solution with respect to the exterior body 12.

[0040] The anodizing treatment liquid can be used without particular limitation from those generally used for anodizing treatment. As an example, sulfuric acid, ammonium sulfate, sodium bisulfate, ammonium bisulfate, phosphoric acid, sodium phosphate, boric acid, borax, ammonium carbonate, chromic acid, dichromic acid, sulfamic acid, oxalic acid, tartaric acid, maleic acid, citric acid, ammonium citrate, formic acid, aqueous ammonia, sodium hydroxide, ammonium fluoride, potassium ferricyanide, dimethyl sulfoxide, formamide, hydrogen peroxide solution, potassium oxalate titanate, sulfosalicylic acid, sulfophthalic acid, sulfoisophthalic acid, phenolsulfonic acid, etc. can be mentioned.

[0041] (Sealing plate fitting step S20) In the sealing plate fitting step S20, the electrode body 20 is accommodated in the exterior body 12, and the sealing plate 18 is fitted into the opening 15 of the exterior body 12. Thereby, the exterior body 12 (upper end surface 13) and the sealing plate 18 become flush. Also, the outer peripheral surface of the sealing plate 18 and the inner surface of the exterior body 12 (opening 15) face each other, and a fitting portion 11 is formed.

[0042] (Laser welding step S30) In the laser welding step S30, the fitting portion 11 between the exterior body 12 and the sealing plate 18 formed in the sealing plate fitting step S20 is laser welded. More specifically, by laser welding the fitting portion 11 over the entire circumference, an annular fusion-solidified portion 50 is formed. FIG. 6 is a longitudinal sectional view schematically showing the laser welding step S30 according to the embodiment. FIG. 6 corresponds to FIG. 4. As shown in FIG. 6, in the laser welding step S30, the fitting portion 11 is irradiated with a laser L. By the irradiation of the laser L, a part of the exterior body 12 and the sealing plate 18 melts. Then, the protrusion prevention layer 60 formed at the periphery of the opening 15 in the prevention layer forming step S10 suppresses the outward protrusion of the above-mentioned molten portion from the exterior body 12, and the molten portion solidifies in this state, and the fusion-solidified portion 50 is formed. Note that the type of laser light used for laser welding and the conditions of laser welding are not particularly limited, as well as in the conventional case. Also, the angle formed by the laser irradiation direction and the exterior body 12 (upper end surface 13) and the sealing plate 18 (horizontal plane) is typically about 90 ± 10°, for example, about 90 ± 5°.

[0043] As described above, the manufacturing method of the power storage device 100 disclosed herein provides a power storage device 100 that preferably suppresses the outward protrusion from the exterior body 12 of the fusion solidification part 50.

[0044] The power storage device 100 disclosed herein can be used for various applications, and typically, it can be preferably used as a power source (driving power source) for motors mounted on various vehicles, such as passenger cars, trucks, etc. The type of vehicle is not particularly limited, and examples include plug-in hybrid vehicles (PHEVs), hybrid vehicles (HEVs), battery electric vehicles (BEVs), etc.

[0045] Some embodiments of the technology disclosed herein have been described above, but the above embodiments are merely examples. The technology disclosed herein can be implemented in various other forms. The technology disclosed herein 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 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. Also, if its technical features are not described as essential, it can be appropriately deleted.

[0046] In the above-described embodiment, the overflow prevention layer 60 was disposed on the outer surface of the side wall of the exterior body 12, but not on the upper end surface 13. However, the present invention is not limited to this. FIG. 7 is a view corresponding to FIG. 4 of the power storage device 200 according to the first modification. Here, the power storage device 200 may be the same as the power storage device 100 except that it includes an overflow prevention layer 260. As shown in FIG. 7, the overflow prevention layer 260 is disposed not only on the outer surface of the short side wall 12a of the exterior body 12 but also on a part of the upper end surface 13. In other words, here, the overflow prevention layer 260 has an inverted L shape. Thereby, among the overflow prevention layer 260, the portion provided on the upper end surface 13 side serves as a return. Therefore, the overflow of the melt-solidified portion 50 can be more preferably suppressed. When disposing the overflow prevention layer 260 on the upper end surface 13, it is preferable not to form the overflow prevention layer 260 at the planned irradiation site of the laser L (for example, the opening 15).

[0047] Further, in the above-described embodiment, the upper end of the overflow prevention layer 60 was disposed so as to reach the peripheral edge portion 16 of the exterior body 12. However, the present invention is not limited to this. The upper end of the overflow prevention layer 60 does not necessarily have to reach the peripheral edge portion 16 of the exterior body 12. FIG. 8 is a view corresponding to FIG. 4 of the power storage device 300 according to the second modification. Here, the power storage device 300 may be the same as the power storage device 100 except that it includes an overflow prevention layer 360. As shown in FIG. 8, the upper end portion of the overflow prevention layer 360 does not reach the peripheral edge portion 16. As shown in FIG. 8, in the modification shown here, while the peripheral edge portion 16 is melted by laser irradiation, the formation of the melt-solidified portion 50 outside the exterior body 12 is suppressed. That is, even when the upper end of the overflow prevention layer 360 is not formed up to the peripheral edge portion 16, the effect of suppressing the formation of the melt-solidified portion 50 outside the exterior body 12 is exhibited.

[0048] Note that the overflow prevention layers 260 and 360 according to the above-described modifications can be formed, for example, by adjusting the masking location on the exterior body 12 in the above-described prevention layer formation step S10. However, the formation method is not limited to this.

[0049] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Item 1: A power storage device comprising: an electrode body having an electrode; a bottom portion; a side wall extending from the periphery of the bottom portion; an opening surrounded by the side wall; an exterior body for housing the electrode body; a sealing plate for sealing the opening; and an annular molten and solidified portion formed at a fitting portion between the opening of the exterior body and the sealing plate, wherein at least a part of the periphery of the opening of the exterior body has a protrusion prevention layer for preventing the molten and solidified portion from being formed outside the exterior body. Item 2: The power storage device according to Item 1, wherein the sealing plate is substantially rectangular and plate-shaped, the bottom portion is substantially rectangular having a pair of short sides and a pair of long sides, and the side wall includes a pair of long side walls extending from the long side of the bottom portion and facing each other, and a pair of short side walls extending from the short side of the bottom portion and facing each other. Item 3: The power storage device according to Item 2, wherein the protrusion prevention layer is disposed on at least a pair of the short side walls. Item 4: The power storage device according to Item 2, wherein the protrusion prevention layer is disposed on at least a pair of the long side walls. Item 5: The power storage device according to Item 1 or 2, wherein the protrusion prevention layer is disposed over the entire periphery of the opening of the exterior body. Item 6: The power storage device according to any one of Items 1 to 5, wherein the protrusion prevention layer is mainly composed of aluminum oxide. Item 7: The power storage device according to any one of Items 1 to 6, wherein the protrusion prevention layer is disposed on the outer surface of the side wall and at least a part of the upper end surface of the side wall of the exterior body. Item 8: The power storage device according to any one of Items 1 to 6, wherein the protrusion prevention layer is disposed on the outer surface of the side wall of the exterior body, and the upper end portion of the protrusion prevention layer is disposed at a position that does not reach the peripheral portion where the outer surface of the side wall and the upper end surface of the side wall intersect. Item 9: A method for manufacturing a power storage device, comprising: an electrode body having electrodes, a bottom portion, side walls extending from the periphery of the bottom portion, and an opening surrounded by the side walls; an exterior body for housing the electrode body; a sealing plate for sealing the opening; and an annular molten and solidified portion formed at a fitting portion between the opening of the exterior body and the sealing plate, the method comprising: a preventive layer forming step of forming a protrusion prevention layer on at least a part of the periphery of the opening of the exterior body; a sealing plate fitting step of housing the electrode body in the exterior body and fitting the sealing plate to the opening of the exterior body; and a laser welding step of forming the molten and solidified portion by laser-welding the fitting portion between the exterior body and the sealing plate after the sealing plate fitting step. Item 10: The method for manufacturing a power storage device according to Item 9, wherein the exterior body is made of aluminum or an aluminum alloy, and the preventive layer forming step is performed by anodizing. Item 11: The method for manufacturing a power storage device according to Item 9 or 10, wherein in the preventive layer forming step, the protrusion prevention layer is formed on at least a part of an outer surface of the side walls and an upper end surface of the side walls of the exterior body. Item 12: The method for manufacturing a power storage device according to Item 9 or 10, wherein in the preventive layer forming step, the upper end portion of the protrusion prevention layer is formed so as not to reach a peripheral portion where the outer surface of the side walls and the upper end surface of the side walls intersect.

Explanation of Reference Numerals

[0050] 1 Case 3 Positive Electrode 4 Negative Electrode 6 Positive Electrode Terminal 7 Separator 8 Negative Electrode Terminal 11 Fitting Portion 12 Exterior Body 12d Bottom Portion 12a, 12b Short Side Walls 12e, 12f Long Side Walls 13 Upper End Surface 13a, 13b Short Side Portions 13e, 13f Long Side Portions 15 Opening 16 Peripheral Portion 18 Sealing plate 71 Liquid injection hole 20 Electrode body 30 Positive current collector 31 Positive active material layer 35 Positive current collecting member 36 Positive external conductive member 40 Negative current collector 41 Negative active material layer 45 Negative current collecting member 46 Negative external conductive member 50 Melting and solidifying part 60, 260, 360 Overflow prevention layer 74, 75 Terminal lead-out hole 76 Gasket 78 Insulator 100 Energy storage device L Laser S10 Anti-layer formation process S20 Sealing plate fitting process S30 Laser welding process

Claims

1. An electrode body having electrodes, An exterior body having a bottom, side walls extending from the periphery of the bottom, and an opening surrounded by the side walls, for housing the electrode body, A sealing plate for sealing the opening, An annular molten and solidified portion formed at the fitting portion between the opening of the exterior body and the sealing plate, and At least a part of the periphery of the opening of the exterior body has a protrusion prevention layer for preventing the molten and solidified portion from being formed outside the exterior body, The protrusion prevention layer is A layer having a melting point higher than that of the molten and solidified portion, Disposed on the outer surface of the side wall and a part of the upper end surface of the side wall of the exterior body, A power storage device.

2. The sealing plate is substantially rectangular and plate-shaped, The bottom is substantially rectangular having a pair of short sides and a pair of long sides, The side walls include a pair of long side walls extending from the long sides of the bottom and facing each other, and a pair of short side walls extending from the short sides of the bottom and facing each other, The power storage device according to claim 1.

3. The protrusion prevention layer is disposed on at least a pair of the short side walls, The power storage device according to claim 2.

4. The protrusion prevention layer is disposed on at least a pair of the long side walls, The power storage device according to claim 2.

5. The protrusion prevention layer is disposed over the entire periphery of the opening of the exterior body, The power storage device according to claim 1 or 2.

6. The protrusion prevention layer is mainly composed of aluminum oxide, The power storage device according to claim 1 or 2.

7. An electrode body having electrodes, An exterior body having a bottom, side walls extending from the periphery of the bottom, and an opening surrounded by the side walls, for housing the electrode body, A sealing plate for sealing the opening, A method for manufacturing a power storage device including an annular molten and solidified portion formed at the fitting portion between the opening of the exterior body and the sealing plate, comprising: A prevention layer forming step of forming a protrusion prevention layer, which is a layer having a melting point higher than that of the molten and solidified portion, on at least a part of the periphery of the opening of the exterior body, A sealing plate fitting step of housing the electrode body in the exterior body and fitting the sealing plate to the opening of the exterior body, After the sealing plate fitting step, a laser welding step of forming the molten and solidified portion by laser welding the fitting portion between the exterior body and the sealing plate, and In the prevention layer forming step, the protrusion prevention layer is formed on the outer surface of the side wall and the upper end surface of the side wall of the exterior body. Method for manufacturing a power storage device.

8. The exterior body is made of aluminum or an aluminum alloy, The anti-corrosion layer forming step is performed by anodizing, The method for manufacturing a power storage device according to claim 7.

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