Power storage device and method for manufacturing power storage device

Abstract

A power storage device (1) comprises: a positive electrode (11) and a negative electrode (12) facing each other; a porous separator (13) arranged between the positive electrode (11) and the negative electrode (12); and a resin sealing portion (14) sealing a space (S) between the positive electrode (11) and the negative electrode (12); the separator (13) is constructed to include a material having a melting temperature higher than the melting temperature of the resin material constituting the sealing portion (14); and an edge portion (13a) of the separator (13) is clamped and held by the sealing portion (14) in a state of being combined with a molten solidified portion (M1) of the resin material constituting the sealing portion (14).

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] As a conventional power storage device, for example, the power storage device described in Patent Document 1 is known. This power storage device includes a separator disposed between a positive electrode and a negative electrode, and a sealing portion that seals the space between the positive and negative electrodes. The edge of the separator is welded to the sealing portion.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-62081 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] To prevent short circuits between the positive and negative electrodes due to separator shrinkage, as in the aforementioned energy storage device, a configuration in which the edge of the separator between the positive and negative electrodes is welded to the seal can be considered. However, when the separator edge is welded to the seal, the separator thickness may be partially insufficient. When the separator shrinks in this state, a portion of the separator may be stretched and break. If the separator breaks, the positive and negative electrodes will face each other without the separator, potentially causing a short circuit between the positive and negative electrodes.

[0008] An object of the present disclosure is to provide an electricity storage device and a method for manufacturing the electricity storage device, which are capable of more reliably suppressing a short circuit between a positive electrode and a negative electrode.

[0009] Solutions for solving problems

[0010] One aspect of the present disclosure is a storage device comprising: a positive electrode and a negative electrode, which are opposite to each other; a porous separator, which is arranged between the positive electrode and the negative electrode; and a resin sealing portion, which seals the space between the positive electrode and the negative electrode, wherein the separator is constructed to include a material having a melting temperature higher than the melting temperature of the resin material constituting the sealing portion, and the edge of the separator is clamped and held by the sealing portion while being combined with the molten solidified portion of the resin material constituting the sealing portion.

[0011] In this power storage device, the edge of the separator is clamped and held by the sealing portion while being bonded to the molten solidified portion of the resin material constituting the sealing portion, thereby preventing the separator from being displaced. Consequently, it is possible to prevent the positive and negative electrodes from facing each other without the separator, and thus to prevent short circuits between the positive and negative electrodes. Furthermore, since the separator is constructed to include a material having a melting point higher than that of the resin material constituting the sealing portion, the edge of the separator can be bonded to the molten solidified portion while maintaining its shape and not melting. By maintaining the shape of the separator in this way, it is possible to prevent the separator from becoming locally thinner. Therefore, even if the separator shrinks, it is possible to prevent a portion of the separator from being stretched and broken. As a result, it is possible to maintain the state in which the separator is between the positive and negative electrodes, thereby more reliably preventing short circuits between the positive and negative electrodes.

[0012] Alternatively, the molten solidified portion may be located on the outer surface of the separator's edge. In this case, the outer surface of the separator's edge and the molten solidified portion can be rubbed against the seal to maintain the separator's edge against the seal. In this configuration, the bonding strength between the separator's edge and the seal can be fully ensured, thereby preventing the separator's edge from detaching from the seal. As a result, the positive and negative electrodes can be more reliably maintained with the separator between them, thus preventing short circuits between the positive and negative electrodes.

[0013] Alternatively, the molten solidified portion may be located within the hole in the edge of the separator. This allows the molten solidified portion to enter the hole in the edge of the separator, thereby achieving an anchoring effect at the junction between the edge of the separator and the sealing portion. This improves the bonding strength between the edge of the separator and the sealing portion, thereby more reliably preventing the edge of the separator from detaching from the sealing portion. As a result, the separator can be further reliably maintained between the positive and negative electrodes, further reliably preventing short circuits between the positive and negative electrodes.

[0014] Alternatively, the separator may include a first porous layer and a second porous layer stacked on top of each other, the first porous layer being composed of a material having a melting temperature higher than that of the resin material constituting the sealing portion, and the second porous layer being composed of a material having a melting temperature lower than that of the material constituting the first porous layer, the edge of the first porous layer being bonded to a first melt-solidified portion formed by melting and solidifying the resin material constituting the sealing portion, and the edge of the second porous layer being bonded to a second melt-solidified portion formed by melting and solidifying the material constituting the second porous layer and the resin material constituting the sealing portion. By bonding the edge of the second porous layer to the second melt-solidified portion in this manner, the bonding strength between the edge of the separator and the sealing portion can be increased, and the situation in which the edge of the separator is separated from the sealing portion can be suppressed. In addition, as described above, the edge of the first porous layer can be bonded to the sealing portion in a state in which its shape is maintained and it is not melted, thereby suppressing the situation in which the separator is broken due to shrinkage of the separator. That is, according to the above-mentioned structure, it is possible to suppress the separation of the edge of the separator from the sealing portion and to suppress the breakage of the separator. Thus, it is possible to further reliably maintain the state of the separator between the positive electrode and the negative electrode, thereby further reliably suppressing short circuits between the positive electrode and the negative electrode.

[0015] Alternatively, the first porous layer may be laminated so as to sandwich the second porous layer. In this case, the separator edge can be prevented from detaching from the sealing portion, and the separator breakage can be more reliably suppressed. This further reliably maintains the separator between the positive and negative electrodes, thereby further reliably suppressing short circuits between the positive and negative electrodes.

[0016] One aspect of the present disclosure is a method for manufacturing an electrical storage device, the electrical storage device comprising: a positive electrode and a negative electrode facing each other; a porous separator arranged between the positive electrode and the negative electrode; and a resin sealing portion that seals the space between the positive electrode and the negative electrode, the method for manufacturing the electrical storage device comprising: a preparation step of preparing an insulator composed of a material having a melting temperature higher than that of a resin material constituting the sealing portion; a configuration step of configuring an edge of the insulator so as to be sandwiched by the resin material constituting the sealing portion; and a welding step of bonding the edge of the insulator and the resin material constituting the sealing portion to each other by welding, wherein the welding is performed at a temperature higher than the melting temperature of the resin material constituting the sealing portion and lower than the melting temperature of the material constituting the insulator.

[0017] In this method for manufacturing a power storage device, the edge of the separator is positioned so as to be sandwiched between the resin material forming the seal, and the edge of the separator and the resin material forming the seal are bonded together by welding. As a result, the edge of the separator is held between the seal, thereby preventing the separator from shifting. This prevents the positive and negative electrodes from facing each other without the separator, and thus prevents short circuits between the positive and negative electrodes. Furthermore, the welding process is performed at a temperature above the melting temperature of the resin material forming the seal and below the melting temperature of the material forming the separator. Therefore, during the welding process, the edge of the separator can be bonded to the seal while melting the seal without melting the separator. In other words, the edge of the separator can be bonded to the seal while maintaining its shape and not melting. By maintaining the separator's shape in this way, localized thinning of the separator can be prevented. Therefore, even if the separator shrinks, it can be prevented from partially stretching and breaking. As a result, the state in which the separator is interposed between the positive electrode and the negative electrode can be maintained, and thus a short circuit between the positive electrode and the negative electrode can be more reliably suppressed.

[0018] Effects of the Invention

[0019] According to the present disclosure, short circuiting between the positive electrode and the negative electrode can be more reliably suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic cross-sectional view showing one embodiment of a power storage device.

[0021] Figure 2 This is a cross-sectional view showing an enlarged portion of the power storage device.

[0022] Figure 3 (a) is a schematic cross-sectional view showing one embodiment of a method for manufacturing a power storage device. Figure 3 (b) shows Figure 3 A schematic cross-sectional view of the subsequent steps of (a).

[0023] Figure 4 (a) shows Figure 3 (b) is a schematic cross-sectional view of the subsequent steps. Figure 4 (b) shows Figure 4 A schematic cross-sectional view of the subsequent steps of (a).

[0024] Figure 5 This is an enlarged cross-sectional view showing a first modified example of the power storage device.

[0025] Figure 6 This is an enlarged cross-sectional view showing a second modified example of the power storage device.

[0026] Figure 7 This is an enlarged cross-sectional view showing a third modified example of the power storage device. DETAILED DESCRIPTION

[0027] Hereinafter, an embodiment of a method for manufacturing an electrode plate according to one aspect of the present disclosure will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted as appropriate.

[0028] Figure 1 The illustrated power storage device 1 is a power storage module used in various vehicles, such as forklifts, hybrid vehicles, and electric vehicles. Power storage device 1 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. Power storage device 1 may also be an electric double-layer capacitor or an all-solid-state battery. In this embodiment, a lithium-ion secondary battery is used as an example.

[0029] The power storage device 1 is configured to include a battery stack 5, which is formed by stacking the power storage cells 2 in a stacking direction. Figure 1 As shown, the battery cell 2 includes: a positive electrode 11, a negative electrode 12, a separator 13 and a sealing portion 14. The positive electrode 11 is a rectangular electrode formed by applying a positive electrode active material layer 22 on one side of a metal foil 21. The negative electrode 12 is a rectangular electrode formed by applying a negative electrode active material layer 23 on one side of a metal foil 21. The negative electrode 12 is configured so that the negative electrode active material layer 23 is opposite to the positive electrode active material layer 22. In this embodiment, both the positive electrode active material layer 22 and the negative electrode active material layer 23 are applied in a rectangular shape. The negative electrode active material layer 23 is formed to be larger than the positive electrode active material layer 22, and when viewed from above, the entire application area of ​​the positive electrode active material layer 22 is located within the application area of ​​the negative electrode active material layer 23.

[0030] The power storage cells 2 are stacked so that the metal foil 21 of the positive electrode 11 and the metal foil 21 of the negative electrode 12 are in contact with each other, thereby forming a battery stack 5. In the battery stack 5, the power storage cells 2, 2 adjacent to each other in the stacking direction form a pseudo-bipolar electrode 16, which has the metal foil 21 of the positive electrode 11 and the metal foil 21 of the negative electrode 12 in contact with each other as the electrode body.

[0031] The metal foil 21 is, for example, copper foil, aluminum foil, titanium foil, or nickel foil. To ensure mechanical strength, the metal foil 21 may be a stainless steel foil (e.g., SUS304, SUS316, SUS301, etc., as specified in JIS G 4305:2015). The metal foil 21 may also be an alloy foil of the aforementioned metals. When the metal foil 21 is an alloy foil or a metal foil other than aluminum foil, its surface may be coated with aluminum.

[0032] The positive electrode active material layer 22 is composed of, for example, a composite oxide, metallic lithium, and a positive electrode active material such as sulfur. The composite oxide composition includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, as well as lithium. An example of a composite oxide is olivine-type lithium iron phosphate (LiFePO4).

[0033] In addition to the positive electrode active material, the positive electrode active material layer 22 may also contain a binder and a conductive aid. The binder plays the role of holding the active material or conductive aid on the surface of the collector and maintaining the conductive network in the electrode. Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; resins containing alkoxysilyl groups; acrylic resins such as polyacrylic acid or polymethacrylic acid; styrene-butadiene rubber (SBR); carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinks; starch-acrylic acid graft polymers. These binders can be used alone or in combination. Conductive aids include acetylene black, carbon black, graphite, etc. Viscosity adjustment solvents include, for example, N-methyl-2-pyrrolidone (NMP).

[0034] The negative electrode active material layer 23 is composed of, for example, carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, soft carbon, or the like; metal compounds; elements or compounds capable of alloying with lithium; and boron-doped carbon. Examples of elements capable of alloying with lithium include silicon and tin. The conductive additive and binder used for the positive electrode active material layer 22 can be the same.

[0035] The separator 13 is arranged between the positive electrode 11 and the negative electrode 12 facing each other. When the storage battery cells 2 are stacked, short circuits between adjacent bipolar electrodes 16, 16 are prevented. The separator 13 is a porous body having a plurality of pores formed therein, and is composed of a material having a melting temperature higher than the melting temperature of the resin material constituting the sealing portion 14. As the material constituting the separator 13, for example, a porous film including polypropylene (PP) is used. The material constituting the separator 13 may also be a woven fabric or non-woven fabric including polypropylene or methyl cellulose. In the present embodiment, the case where the entire separator 13 is composed of a material having a melting temperature higher than the melting temperature of the resin material constituting the sealing portion 14 is illustrated, but a part of the separator 13 may also be composed of the material. In this specification, the melting temperature of a certain material refers to the temperature at which the material begins to melt, that is, the melting point of the material.

[0036] The sealing portion 14 is a resin member that seals the space S between the positive electrode 11 and the negative electrode 12 and has electrical insulation properties. The sealing portion 14 has a rectangular frame shape when viewed from above and is welded to the edge 21a of the metal foil 21 in the positive electrode 11 and the edge 21a of the metal foil 21 in the negative electrode 12. As described later, the sealing portion 14 is formed by welding a resin portion 25A welded to the edge 21a of the metal foil 21 in the positive electrode 11 and a resin portion 25B welded to the edge 21a of the metal foil 21 in the negative electrode 12 (see FIG. 2 ). Figure 3 (a) and Figure 3 (b)).

[0037] The edge of the resin portion 25 is a protruding portion 25a that protrudes outward from the edge 21a of the metal foil 21 in the positive electrode 11 and the edge 21a of the metal foil 21 in the negative electrode 12. In the battery stack 5, the protruding portions 25a of the resin portion 25 are joined together by hot plate welding or the like. Thus, the sealing portion 14 has a generally rectangular frame shape that surrounds the outer peripheral surface (side surface) of the battery stack 5. The sealing portion 14 also functions as a sealing member that seals the contacting metal foil 21 of the positive electrode 11 and the metal foil 21 of the negative electrode 12 in adjacent power storage cells 2 in the stacking direction.

[0038] Examples of the resin material constituting the sealing portion 14 include polyethylene (PE), polystyrene, ABS resin, modified polypropylene (modified PP), and acrylonitrile styrene (AS) resin. An electrolyte (not shown) is contained in the space S sealed by the sealing portion 14. The electrolyte is, for example, a carbonate-based or polycarbonate-based electrolyte. The supporting salt contained in the electrolyte is, for example, a lithium salt. Examples of the lithium salt are LiBF4, LiPF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, or mixtures thereof.

[0039] like Figure 2 As shown, the edge 13a of the separator 13 is buried in the sealing portion 14. Specifically, the edge 13a of the separator 13 is sandwiched and held by the sealing portion 14 while being bonded to the melted and solidified portion M1 of the resin material of the sealing portion 14. For example, when the edge 13a of the separator 13 and the sealing portion 14 are bonded to each other by welding such as heat welding or laser welding, the resin material constituting the sealing portion 14 melts and solidifies. The melted and solidified portion M1 refers to the portion of the resin material that is melted and solidified and is located within the pores of the separator 13.

[0040] For example, the resin material of the sealing portion 14 in a molten state solidifies while entering the hole of the edge 13a of the spacer 13 from the outer surface 13b of the edge 13a of the spacer 13, thereby forming a molten solidified portion M1 located in the hole of the edge 13a of the spacer 13. The molten solidified portion M1 located in the hole of the edge 13a of the spacer 13 includes the following two cases: a case where the molten solidified portion M1 is provided without a gap in the hole of the edge 13a of the spacer 13, and a case where the molten solidified portion M1 is provided only in a portion of the hole of the edge 13a of the spacer 13.

[0041] Next, a method for manufacturing the above-mentioned electricity storage device 1 will be described.

[0042] When manufacturing the power storage device 1, first, the positive electrode 11, which is formed by applying a positive electrode active material layer 22 to one surface of a metal foil 21; the negative electrode 12, which is formed by applying a negative electrode active material layer 23 to one surface of a metal foil 21; and the separator 13, which is composed of a material having a higher melting temperature than the melting temperature of the resin material constituting the sealing portion 14, are prepared (preparation step). Figure 3 As shown in (a), the resin portion 25A is bonded to the edge portion 21a of one surface of the metal foil 21 in the positive electrode 11 to form a positive electrode 41 with a resin portion, and as shown in FIG. Figure 3 As shown in (b) , the resin portion 25B is bonded to the edge portion 21 a of one surface of the metal foil 21 in the negative electrode 12 to form the negative electrode 42 with the resin portion (forming step).

[0043] During the forming process, the edges of the resin portions 25A and 25B are made to protrude outwards relative to the edges 21a of the metal foil 21 of the positive electrode 11 and the negative electrode 12. The thickness of the resin portion 25A of the positive electrode 41 with a resin portion and the thickness of the resin portion 25B of the negative electrode 42 with a resin portion may be equal to each other. Figure 3 (a) and Figure 3 In (b), the resin portions 25A and 25B are bonded to the edge portion 21a of one surface of the metal foil 21 by adhesion. Alternatively, the resin portions 25A and 25B may be bonded to the edge portion 21a of one surface of the metal foil 21 by welding. When welding the resin portions 25A and 25B to the metal foil 21, for example, the resin portions 25A and 25B may be heated from the metal foil 21 side using a heating means such as a heater.

[0044] Next, after placing the separator 13 on the active material layer of one of the positive electrode 41 with a resin portion and the negative electrode 42 with a resin portion, the electrolyte E is dripped and injected (liquid injection step). Figure 4As shown in (a), a positive electrode 41 with a resin portion having a small active material layer coating area is used, and a separator 13 is placed on the positive electrode active material layer 22 of the positive electrode 41 with a resin portion. At this time, the edge 13a of the separator 13 overlaps the resin portion 25A. The dripped electrolyte E is impregnated into the separator 13.

[0045] After the electrolyte E is injected, the positive electrode 41 with a resin portion and the negative electrode 42 with a resin portion are arranged so that the positive electrode active material layer 22 and the negative electrode active material layer 23 face each other (arrangement step). Figure 4 As shown in (b), the negative electrode 42 with a resin portion is stacked on the positive electrode 41 with a resin portion injected with the electrolyte E so that the positive electrode active material layer 22 and the negative electrode active material layer 23 face each other. At this time, the edge 13a of the separator 13 is sandwiched between the resin portion 25A and the resin portion 25B.

[0046] Next, the edge 13a of the separator 13, the resin portion 25A of the positive electrode 41 with a resin portion, and the resin portion 25B of the negative electrode 42 with a resin portion are bonded to each other by welding (welding process). In the welding process, heat H is applied from the metal foil 21 side of the electrode of the positive electrode 41 with a resin portion and the metal foil 21 side of the electrode of the negative electrode 42 with a resin portion. At this time, the temperature of the heat H at the interface between the edge 13a of the separator 13 and the resin portions 25A and 25B is set to a temperature that is higher than the melting temperature of the resin portions 25A and 25B (for example, 130°C) and lower than the melting temperature of the separator 13 (for example, 160°C). When welding is performed with the heat H at this temperature, the resin portions 25A and 25B melt, but the separator 13 does not melt.

[0047] Therefore, the edge 13a of the spacer 13 is bonded to the resin portions 25A and 25B while maintaining its shape without melting. The resin portions 25A and 25B are melted and bonded to each other, thereby forming the resin portion 25 (see FIG. Figure 1 ). In this way, the resin portion 25 is obtained, which is combined with the edge portion 13a of the spacer 13. In the resin portion 25, the portion located in the hole of the edge portion 13a of the spacer 13 becomes the melt-solidified portion M1 formed by the solidification of the melted portion of the resin portion 25 (see Figure 2 ).

[0048] exist Figure 4In the example shown in (b), the edge 13a of the spacer 13 and the resin portions 25A and 25B are bonded to each other by heat welding using a heating means such as a heater. However, the edge 13a of the spacer 13 and the resin portions 25A and 25B can also be bonded to each other by laser welding. In this case, laser light of a wavelength easily absorbed by the metal foil 21 is used. Then, by irradiating the metal foil 21 with laser light of this wavelength, the metal foil 21 is heated, which melts the resin portions 25A and 25B, thereby obtaining the resin portion 25 bonded to the edge 13a of the spacer 13.

[0049] After the above steps, the power storage cell 2 is obtained. Then, by repeatedly performing the preparation step to the welding step, a plurality of power storage cells 2 are obtained. After obtaining a plurality of power storage cells 2, as shown in FIG. Figure 1 As shown, the storage cells 2 are stacked in such a manner that the metal foil 21 of the positive electrode 11 and the metal foil 21 of the negative electrode 12 are in contact with each other, thereby forming a battery stack 5 (cell stacking process). After the battery stack 5 is formed, heat H is applied from a hot plate (not shown) to the protruding portions 25a of the resin portion 25 in each storage cell 2, for example, by hot plate welding, so that the protruding portions 25a are welded to each other. Thus, a sealing portion 14 is formed to seal between the metal foil 21 of the positive electrode 11 and the metal foil 21 of the negative electrode 12 that are in contact with each other in the storage cells 2, 2 adjacent in the stacking direction, and a sealing portion 14 is obtained. Figure 1 The power storage device 1 shown.

[0050] Next, the effects of the power storage device 1 and the method for manufacturing the power storage device 1 according to this embodiment will be described. In the power storage device 1 according to this embodiment, the edge 13a of the separator 13 is held and clamped by the sealing portion 14 while bonded to the molten-solidified portion M1 of the resin material constituting the sealing portion 14. This prevents the separator 13 from shifting position. This prevents the positive electrode 11 and the negative electrode 12 from facing each other without the separator 13 in between, and thus prevents short circuits between the positive electrode 11 and the negative electrode 12. Furthermore, because the separator 13 is constructed from a material having a higher melting point than the resin material constituting the sealing portion 14, the edge 13a of the separator 13 can be bonded to the molten-solidified portion M1 while maintaining its shape and not melting. By maintaining the shape of the separator 13 in this way, localized thinning of the separator 13 can be prevented. Therefore, even if the separator 13 shrinks, it is prevented from partially stretching and breaking. As a result, the separator 13 can be maintained between the positive electrode 11 and the negative electrode 12 , and thus a short circuit between the positive electrode 11 and the negative electrode 12 can be more reliably suppressed.

[0051] The melted and solidified portion M1 is located within the hole of the edge portion 13a of the separator 13. Thus, since the melted and solidified portion M1 enters the hole of the edge portion 13a of the separator 13, it exerts an anchoring effect at the junction between the edge portion 13a of the separator 13 and the sealing portion 14. This improves the bonding strength between the edge portion 13a of the separator 13 and the sealing portion 14, thereby more reliably suppressing the edge portion 13a of the separator 13 from detaching from the sealing portion 14. As a result, the state in which the separator 13 is interposed between the positive electrode 11 and the negative electrode 12 can be further reliably maintained, thereby further reliably suppressing short circuits between the positive electrode 11 and the negative electrode 12.

[0052] In the method for manufacturing the power storage device 1 of this embodiment, the edge 13a of the separator 13 is positioned so as to be sandwiched between the resin portions 25A and 25B, and the edge 13a of the separator 13 and the resin portions 25A and 25B are bonded to each other by welding. As a result, the edge 13a of the separator 13 is held by the seal portion 14, thereby preventing the separator 13 from shifting. This prevents the positive electrode 11 and the negative electrode 12 from facing each other without the separator 13 in between, and thus prevents short circuits between the positive electrode 11 and the negative electrode 12. Furthermore, the welding step is performed at a temperature that is higher than the melting temperature of the resin portions 25A and 25B and lower than the melting temperature of the separator 13. Therefore, during welding, the seal portion 14 is melted while the edge 13a of the separator 13 is bonded to the seal portion 14, without melting the separator 13. In other words, the edge 13a of the separator 13 can be bonded to the sealing portion 14 while maintaining its shape and not melting. By maintaining the shape of the separator 13 in this way, it is possible to prevent the separator 13 from becoming locally thinner. Therefore, even if the separator 13 shrinks, it is possible to prevent a portion of the separator 13 from being stretched and breaking. As a result, the separator 13 can be maintained between the positive electrode 11 and the negative electrode 12, thereby more reliably preventing a short circuit between the positive electrode 11 and the negative electrode 12.

[0053] While one embodiment of the power storage device 1 and the method for manufacturing the power storage device 1 have been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.

[0054] In the above embodiment, the melted solidified portion M1 is shown as being located in the hole of the edge portion 13a of the separator 13, but it may also be Figure 5 As shown, the entire molten solidified portion M1 is located on the outer surface 13b of the edge 13a of the separator 13. That is, the entire molten solidified portion M1 may not enter the hole of the edge 13a of the separator 13, but may stay on the outer surface 13b of the edge 13a of the separator 13. Figure 5In the example shown, the portion of the seal 14 where the resin material is melted and solidified, located on the outer surface 13b of the separator 13, is referred to as the melt-solidified portion M1. In this example, the melt-solidified portion M1 is located on each of the one surface S1 and the other surface S2, which are opposite to each other in the stacking direction at the edge 13a of the separator 13, and the side surface S3 connecting the one surface S1 and the other surface S2 at the edge 13a of the separator 13. The melt-solidified portion M1 may also be located on both or one of the one surface S1 and the other surface S2, or may be located only on the side surface S3.

[0055] exist Figure 5 In the example shown, the outer surface 13b of the edge 13a of the separator 13 is rubbed against the melted and solidified portion M1, thereby enabling the edge 13a of the separator 13 to be held against the sealing portion 14. Consequently, the bonding strength between the edge 13a of the separator 13 and the sealing portion 14 can be sufficiently ensured, thereby suppressing the edge 13a of the separator 13 from being separated from the sealing portion 14. As a result, the separator 13 can be more reliably maintained between the positive electrode 11 and the negative electrode 12, thereby more reliably suppressing short circuits between the positive electrode 11 and the negative electrode 12.

[0056] In addition, you can also Figure 6 As shown, a portion of the melted and solidified portion M1 enters the hole of the edge 13a of the separator 13, and the remaining portion of the melted and solidified portion M1 remains on the outer surface 13b of the edge 13a of the separator 13. In other words, the melted and solidified portion M1 may be located both on the outer surface 13b of the edge 13a of the separator 13 and in the hole of the edge 13a of the separator 13. Even in this manner, the same effect as in the above-mentioned embodiment can be achieved.

[0057] In the above embodiment, the spacer 13 is shown as a single layer, but the spacer 13 may also be a multi-layer. Figure 7 In the example shown, separator 13A has a three-layer structure comprising a porous layer 31A (first porous layer), a porous layer 32 (second porous layer), and a porous layer 31B (first porous layer) stacked in this order. In other words, separator 13 comprises porous layer 31A (first porous layer) and porous layer 32 (second porous layer) stacked one on top of the other. Porous layers 31A and 31B are stacked on top of each other, sandwiching porous layer 32, and have the same structure. Similar to separator 13 in the aforementioned embodiment, porous layers 31A and 31B are made of a material having a higher melting point than the resin material constituting sealing portion 14.

[0058] On the other hand, the porous layer 32 is composed of a material having a melting temperature lower than the melting temperature of the material constituting the porous layers 31A and 31B. As the material constituting the porous layer 32, for example, a porous film including polyethylene (PE) can be cited. The melting temperature of the material constituting the porous layer 32 may be the same as the melting temperature of the resin material constituting the sealing portion 14, or may be lower or higher than the melting temperature. In other words, the material constituting the porous layer 32 may be the same as the resin material constituting the sealing portion 14, or may be different from the material. In addition, Figure 7 In the illustrated example, the porous layer 31A, the porous layer 32, and the porous layer 31B have the same thickness, but they may have different thicknesses.

[0059] The edge 13c of the separator 13A (i.e., the edge 31a of the porous layer 31A, the edge 32a of the porous layer 32, and the edge 31b of the porous layer 31B) is held and clamped by the sealing portion 14, similarly to the separator 13 of the above-described embodiment. Similar to the separator 13, the edge 31a of the porous layer 31A and the edge 31b of the porous layer 31B are each bonded to the melted and solidified portion M1 (first melted and solidified portion). The melted and solidified portion M1 bonded to the edge 31a of the porous layer 31A is located only within the pores of the edge 31a of the porous layer 31A, while the melted and solidified portion M1 bonded to the edge 31b of the porous layer 31B is located only within the pores of the edge 31b of the porous layer 31B.

[0060] On the other hand, the edge 32a of the porous layer 32 is coupled to the melt-solidified portion M2 (second melt-solidified portion), which is provided between the melt-solidified portion M1 coupled to the edge 31a of the porous layer 31A and the melt-solidified portion M1 coupled to the edge 31b of the porous layer 31B. The melt-solidified portion M2 is a portion formed by melting and solidifying the porous layer 32 and the sealing portion 14 together when the edge 32a of the porous layer 32 and the sealing portion 14 are coupled to each other by welding, such as heat welding or laser welding. Therefore, the edge 32a of the porous layer 32 is integrated with the melt-solidified portion M2. In other words, the edge 32a of the porous layer 32 constitutes the melt-solidified portion M2.

[0061] When the edge 13c of the separator 13A and the sealing portion 14 are joined together by welding, the temperature of the heat H at the interface between the edge 13c of the separator 13A and the resin portions 25A and 25B is set to a temperature that is higher than the melting temperature of the porous layer 32 and higher than the melting temperature of the resin portions 25A and 25B, but lower than the melting temperature of the porous layers 31A and 31B. When welding is performed at this temperature of heat H, the edge 32a of the porous layer 32 and the resin portions 25A and 25B melt together, while the porous layers 31A and 31B do not melt.

[0062] Therefore, the edge 31a of the porous layer 31A and the edge 31b of the porous layer 31B are bonded to the resin portions 25A and 25B while maintaining their shapes and remaining unmolten. Meanwhile, the edge 32a of the porous layer 32 melts and becomes integrally bonded to the resin portions 25A and 25B. As the edge 32a of the porous layer 32 and the resin portions 25A and 25B fuse and bond, the resin portion 25 is formed. Thus, the resin portion 25 is formed, which is bonded to the edge 13c of the separator 13A. Within the resin portion 25, the portion located within the pores of the edge 31a of the porous layer 31A and the portion located within the pores of the edge 31b of the porous layer 31B each become a melt-solidified portion M1 formed by the solidification of the melted portion of the resin portion 25. On the other hand, in the resin portion 25 , a portion bonded to the edge portion 32 a of the porous layer 32 becomes a melted and solidified portion M2 formed by solidification of the melted portion of the porous layer 32 and the resin portion 25 .

[0063] In separator 13A, because edge 32a of porous layer 32 is integrally bonded to melted and solidified portion M2, the bonding strength between edge 13c of separator 13A and seal 14 is enhanced, thereby preventing edge 13c of separator 13A from separating from seal 14. Furthermore, similar to the above-described embodiment, edge 31a of porous layer 31A and edge 31b of porous layer 31B are bonded to seal 14 while maintaining their shape and remaining unmolten. This prevents separator 13A from breaking due to shrinkage. Specifically, separator 13A prevents both edge 13c of separator 13A from separating from seal 14 and fracture of separator 13A. Consequently, separator 13A can be more reliably maintained between positive electrode 11 and negative electrode 12, further reliably preventing short circuits between positive electrode 11 and negative electrode 12. Furthermore, in the separator 13A, since the porous layer 31A and the porous layer 31B are stacked with the porous layer 32 interposed therebetween, breakage of the separator 13A can be more reliably suppressed.

[0064] exist Figure 7 In the illustrated example, the separator 13A has a three-layer structure, but the separator may also have a two-layer structure or a multi-layer structure having four or more layers. In the case of a two-layer structure, the separator may be composed of a single-layer porous layer 31A and a single-layer porous layer 32. In the case of a multi-layer structure having four or more layers, the separator may be composed of a single-layer or multi-layer porous layer 31A and a single-layer or multi-layer porous layer 32.

[0065] exist Figure 7In the illustrated example, the melted and solidified portion M1 bonded to the edge 31a of the porous layer 31A is located within the pores of the edge 31a of the porous layer 31A, and the melted and solidified portion M1 bonded to the edge 31b of the porous layer 31B is located within the pores of the edge 31b of the porous layer 31B. However, the melted and solidified portion M1 bonded to the edge 31a of the porous layer 31A may be located only on the outer surface 31c of the edge 31a of the porous layer 31A, or may be located both within the pores of the edge 31a of the porous layer 31A and on the outer surface 31c of the edge 31a of the porous layer 31A. Similarly, the molten solidified portion M1 coupled to the edge 31b of the porous layer 31B may be located only on the outer surface 31d of the edge 31b of the porous layer 31B, or may be located both within the pores of the edge 31b of the porous layer 31B and on the outer surface 31d of the edge 31a of the porous layer 31B.

[0066] The structure of the power storage device is not limited to the above-mentioned embodiment and each modified example. For example, the above-mentioned embodiment and each modified example can be combined with each other according to the desired purpose and effect. In addition, the structure of the power storage device is not limited to the above-mentioned embodiment and can be appropriately changed. For example, a battery stack can be formed by alternately stacking bipolar electrodes with a positive electrode active material layer formed on one side of a metal foil and a negative electrode active material layer formed on the other side of the metal foil with a separator interposed therebetween. In this case, the bipolar electrodes and the separator are stacked in such a way that the edge of the separator is sandwiched between a resin portion bonded to one side of the metal foil of the bipolar electrode and a resin portion bonded to the other side of the metal foil of the bipolar electrode facing the bipolar electrode. Then, by laser welding from the side of the stacked body with the bipolar electrodes and separators, the edge of the separator and these resin portions can be bonded to each other. Even in this way, the same effect as the above-mentioned embodiment and each modified example can be achieved.

[0067] Description of Reference Numerals

[0068] 1. Power storage device

[0069] 11. Positive electrode

[0070] 12 negative electrode

[0071] 13.13A Isolation

[0072] 13a, 13c, 21a, 31a, 31b, 32a edge

[0073] 13b, 31c, 31d outer surface

[0074] 14 Sealing part

[0075] 25, 25A, 25B resin part

[0076] 31A, 31B porous layer (first porous layer)

[0077] 32 porous layer (second porous layer)

[0078] M1 Melting and solidifying part (first melting and solidifying part)

[0079] M2 Melting and solidifying part (second melting and solidifying part)

[0080] S space.

Claims

1. A power storage device, characterized in that: have: positive and negative electrodes, which are opposite to each other; a porous separator disposed between the positive electrode and the negative electrode; and a resin sealing portion that seals the space between the positive electrode and the negative electrode, The spacer is formed of a material having a higher melting temperature than the resin material forming the sealing portion. The edge of the separator is sandwiched and held by the sealing portion while being bonded to the melted and solidified portion of the resin material constituting the sealing portion. The separator comprises a first porous layer and a second porous layer stacked on each other. The first porous layer is made of a material having a melting temperature higher than that of the resin material constituting the sealing portion. The second porous layer is composed of a material having a melting temperature lower than the melting temperature of the material constituting the first porous layer. The edge of the first porous layer is bonded to the first melted and solidified portion formed by melting and solidifying the resin material constituting the sealing portion. The edge of the second porous layer is integrally bonded to a second melt-solidified portion formed by melting and solidifying a material constituting the second porous layer and a resin material constituting the sealing portion.

2. The power storage device according to claim 1, wherein The melted and solidified portion is located on the outer surface of the edge portion of the separator.

3. The power storage device according to claim 1 or 2, wherein The melted and solidified portion is located in the hole of the edge portion of the separator.

4. The power storage device according to claim 1 or 2, wherein The first porous layer is stacked so as to sandwich the second porous layer.

5. A method for manufacturing an electricity storage device, the method for manufacturing an electricity storage device according to any one of claims 1 to 4, The method for manufacturing the power storage device is characterized in that: have: a preparation step of preparing the separator composed of a material having a higher melting temperature than a resin material constituting the sealing portion; an arranging step of arranging the edge of the spacer so as to be sandwiched by the resin material constituting the sealing portion; and a welding step of bonding the edge of the separator to the resin material constituting the sealing portion by welding; In the welding step, welding is performed at a temperature equal to or higher than the melting temperature of the resin material constituting the sealing portion and lower than the melting temperature of the material constituting the spacer.

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