Method for manufacturing electric power storage module

Abstract

This method for manufacturing an electric power storage module includes: a step S101 for preparing an electrode by forming a coating layer 80 on a surface 15b of a current collector 15; a step S102 for ultrasonically bonding a detection line 60 to the surface 15b of the current collector 15; and a step S103 for bonding a seal material 41 to the surface 15b via the coating layer 80 after the step S102. In step S101, a part of the coating layer 80 is removed at a peripheral edge 15c of the current collector 15 to form an exposed portion 81, and in step S102, the detection line 60 is ultrasonically bonded to the surface 15b in the exposed portion 81.

Description

Energy storage module manufacturing method

[0001] The present disclosure relates to a method for manufacturing an electricity storage module.

[0002] Patent Document 1 describes a bipolar secondary battery. This bipolar secondary battery has a battery element formed by stacking unit cells. Each unit cell includes a positive electrode, a negative electrode, a separator, and an insulating member. The bipolar secondary battery has a voltage detection terminal disposed on the outer periphery of the battery element between one of the two surfaces of the positive electrode current collector that does not contact the insulating member and one of the two surfaces of the negative electrode current collector that does not contact the insulating member, for detecting the voltage of the unit cell.

[0003] Japanese Patent Application Laid-Open No. 2020-061221

[0004] In the energy storage module described in Patent Document 1, for example, a coating layer such as a carbon coating may be formed on the surface of the current collector in order to improve the bonding strength between the surface of the current collector and the seal or active material. However, when attempting to bond a voltage detection terminal to the surface of a current collector provided with a coating layer, there is a problem in that the bonding strength cannot be sufficiently increased.

[0005] Therefore, an object of the present disclosure is to provide a method for manufacturing an electricity storage module that can improve the bonding strength between the current collector and the terminal.

[0006] The method for manufacturing an electric storage module according to the present disclosure is a method for manufacturing an electric storage module including: an electrode laminate formed by stacking a plurality of electrodes, each electrode including a current collector and a coating layer and an active material layer formed on the surface of the current collector, along a first direction; a sealing body provided so as to surround the electrode laminate by stacking a plurality of sealing materials, each of which is welded to the current collector via the coating layer, along the peripheral portion of the current collector, along the first direction; and a plurality of terminals joined to each of the plurality of current collectors and extended to the outside of the sealing body, the method including a preparation step for preparing electrodes; and a terminal joining step for ultrasonically joining terminals to a first surface, which is the surface of the current collector, the preparation step including a formation step for forming a coating layer on the first surface, and a removal step for removing a portion of the coating layer by irradiating with laser light to form an exposed portion that is exposed from the coating layer relative to the first surface, and the terminal joining step ultrasonically joining the terminal to the exposed portion.

[0007] In this energy storage module manufacturing method, in preparing the electrodes, a coating layer is formed on a first surface, which is the surface of a current collector, and then a portion of the coating layer is removed by irradiating with laser light to form an exposed portion that is exposed from the coating layer on the first surface. Then, a terminal is ultrasonically bonded to the first surface of the current collector in the exposed portion. Therefore, ultrasonic bonding can be performed without a coating layer being interposed between the first surface of the current collector and the terminal at least in part of the joint between the current collector and the terminal. Therefore, even when a coating layer is formed on the current collector, the bond strength between the current collector and the terminal can be improved.

[0008] In the energy storage module manufacturing method according to the present disclosure, in the removal process, the exposed portion may be formed so that the area of ​​the exposed portion when viewed from a direction intersecting the first surface is larger than the area of ​​the region where the first surface and the terminal overlap when viewed from a direction intersecting the first surface.

[0009] In the energy storage module manufacturing method according to the present disclosure, in the terminal joining step, an ultrasonic horn is applied to a second surface of the current collector opposite the first surface to perform ultrasonic joining, thereby joining the terminal to the first surface, and in the removal step, the exposed portion may be formed so that the area of ​​the exposed portion when viewed from a direction intersecting the first surface is larger than the area of ​​the second surface that is in contact with the ultrasonic horn in the terminal joining step.

[0010] The method for manufacturing an electricity storage module according to the present disclosure may further include a sealing material bonding step of bonding a sealing material to the surface of the peripheral edge portion of the current collector via the coating layer.

[0011] In the energy storage module manufacturing method according to the present disclosure, the sealing material is formed in a frame shape that overlaps the peripheral portion of the current collector when viewed from a direction intersecting the first surface, and in the sealing material joining process, the sealing material may be positioned so that it overlaps the exposed portion when viewed from a direction intersecting the first surface.

[0012] In the energy storage module manufacturing method according to the present disclosure, the electrode stack includes a bipolar electrode as an electrode, and the bipolar electrode includes a current collector including a first surface and a second surface opposite the first surface, a first active material layer as an active material layer provided on the second surface, and a second active material layer as an active material layer provided on the first surface and having a different polarity from the first active material layer, and in the forming step, a coating layer may be formed on the first surface and the second surface, and in the removing step, a part of the coating layer formed on the first surface may be removed by irradiating it with laser light, thereby forming an exposed portion that is exposed from the coating layer to the first surface.

[0013] According to the present disclosure, it is possible to provide a method for manufacturing an electricity storage module that can improve the bonding strength between a current collector and a terminal.

[0014] FIG. 1 is a schematic plan view of an energy storage module according to one embodiment. FIG. 2 is a schematic side view showing an enlarged portion of the energy storage module shown in FIG. 1. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a flowchart showing one step of a method for manufacturing an energy storage module according to this embodiment. FIG. 5 is a schematic view showing each step shown in FIG. 4. FIG. 5(a) is a plan view, and FIG. 5(b) is a cross-sectional view. FIG. 6 is a schematic view showing each step shown in FIG. 4. FIG. 6(a) is a cross-sectional view, and FIG. 6(b) is a plan view. FIG. 7 is a schematic view showing each step shown in FIG. 4. FIG. 7(a) is a plan view, and FIG. 7(b) is a cross-sectional view. FIG. 8 is a graph showing the relationship between bonding time and bonding strength.

[0015] An embodiment of the present disclosure will be described below with reference to the drawings. In the description of each drawing, the same or corresponding elements are designated by the same reference numerals, and duplicate descriptions may be omitted. In addition, each drawing may show a Cartesian coordinate system consisting of an X-axis, a Y-axis, and a Z-axis.

[0016] Fig. 1 is a schematic plan view of an energy storage module according to one embodiment. Fig. 2 is a schematic side view showing an enlarged portion of the energy storage module shown in Fig. 1. Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 2. The liquid injection port shown in Figs. 1 and 2 and the sealing member shown in Fig. 1 are omitted from Fig. 3.

[0017] 1 to 3 is mounted on, for example, a forklift, a hybrid vehicle, or an electric vehicle. The power storage module 1 is, for example, a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The power storage module 1 may also be, for example, an electric double layer capacitor. In this embodiment, the power storage module 1 is a lithium-ion secondary battery.

[0018] The energy storage module 1 includes an electrode stack 10, a sealing body 20, a sealing member 30, and a plurality of detection lines (terminals) 60. The electrode stack 10 includes a plurality of electrodes stacked along the Z-axis direction. The electrode stack 10 has, for example, a rectangular parallelepiped shape.

[0019] The sealing body 20 has a liquid injection port 50 formed therein. The sealing body 20 is provided on the peripheral edge of the electrode stack 10. The sealing body 20 seals the side surface of the electrode stack 10. The sealing body 20 has, for example, a rectangular cylindrical shape. The sealing body 20 has electrical insulation properties.

[0020] The liquid inlet portion 50 is provided in a region of the sealing body 20 where a liquid inlet 20a (described later) is formed. The liquid inlet portion 50 is provided on a side surface 20c of the sealing body 20. The width of the liquid inlet portion 50 in the X-axis direction is smaller than the width of the sealing body 20 in the X-axis direction. Both ends of the liquid inlet portion 50 in the X-axis direction are located inside both ends of the sealing body 20 in the X-axis direction. The liquid inlet portion 50 includes a side wall portion 51, an overhang portion 52, an overhang portion 53, a frame portion 54, and a thin-walled portion 55.

[0021] The sidewall portion 51 is provided on the side surface 20c of the sealing body 20. The sidewall portion 51 has, for example, a rectangular plate shape. The overhang portion 52 is provided on one end surface of the sealing body 20 in the Z-axis direction. The overhang portion 52 has, for example, a rectangular plate shape. The overhang portion 53 is provided on the other end surface of the sealing body 20 in the Z-axis direction. The overhang portion 53 has, for example, a rectangular plate shape.

[0022] The liquid inlet portion 50 includes multiple frame portions 54. The frame portions 54 protrude from the side surfaces of the sidewall portions 51. When viewed from the Y-axis direction, the frame portions 54 surround each of the liquid inlets 20a lined up in the Z-axis direction. Thin-walled portions 55 are provided on the side surfaces of the sidewall portions 51 on both sides of the sidewall portions 51 in the X-axis direction. The thin-walled portions 55 extend along the Z-axis direction. The thin-walled portions 55 reach both ends of the sidewall portions 51 in the Z-axis direction. The thickness of the thin-walled portions 55 is smaller than the thickness of the sidewall portions 51. The sidewall portions 51, the overhanging portions 52 and 53, the frame portions 54, and the thin-walled portions 55 are each a partial region of the liquid inlet portion 50 integrated from the same material. The liquid inlet portion 50 is formed, for example, by injection molding.

[0023] The sealing body 20 includes a plurality of liquid inlet ports 20a. The liquid inlet ports 20a are in communication with the internal space S of the electrode stack 10. The liquid inlet ports 20a function as paths for injecting an electrolyte solution into the internal space S. The sealing body 20 has a plurality of liquid inlet rows. The plurality of liquid inlet rows are aligned in the Z-axis direction. Each liquid inlet row includes a plurality of liquid inlet ports 20a aligned in the X-axis direction. Each liquid inlet row includes, for example, ten liquid inlet ports 20a. When focusing on each liquid inlet row, the positions of the liquid inlet ports 20a in the Z-axis direction are gradually shifted from the liquid inlet ports 20a on one side in the X-axis direction to the liquid inlet ports 20a on the other side. As a result, when viewed from the Y-axis direction, the plurality of liquid inlet ports 20a in each liquid inlet row are aligned diagonally with respect to the X-axis direction. In each liquid inlet row, the liquid inlet ports 20a are spaced apart from each other in the X-axis direction.

[0024] The sealing member 30 has, for example, a plate shape. When viewed from the X-axis direction, the sealing member 30 overlaps with the multiple frame portions 54. The sealing member 30 is, for example, a laminate sheet or the like. The sealing member 30 includes, for example, a metal layer and a resin layer. The material of the metal layer is, for example, aluminum. The sealing member 30 is welded to the tips of the multiple frame portions 54. This seals the multiple liquid injection ports 20a. Note that the sealing member 30 is not shown in FIG. 2.

[0025] The multiple detection wires 60 are located adjacent to the multiple frame portions 54 when viewed from the Y-axis direction. The detection wires 60 are used to detect the battery state of the energy storage module 1. In this embodiment, the voltage between adjacent electrodes of the energy storage module 1 is detected by an external device via the detection wires 60. That is, the detection wires 60 are, for example, voltage detection wires (i.e., include terminals for voltage detection). The detection wires 60 protrude from the side wall portion 51. Each detection wire 60 is joined to a respective current collector 15, which will be described later.

[0026] The energy storage module 1 has a plurality of detection line arrays 61. Each detection line array 61 has a plurality of detection lines 60 lined up in the Z-axis direction. That is, the plurality of detection lines 60 constituting one detection line array 61 overlap one another when viewed in the Z-axis direction. The plurality of detection line arrays 61 are lined up along the X-axis direction at predetermined intervals. The positions of the detection lines 60 in the Z-axis direction are shifted from one another. In this embodiment, the detection line arrays 61 are positioned closer to the negative terminal electrode 13 (described later) (lower side in FIG. 2 ) as they move away from the frame portion 54 in the X-axis direction.

[0027] When focusing on a pair of adjacent detection line arrays 61 in the X-axis direction, for example, one detection line 60 of one detection line array 61 is located closer to the positive electrode terminal electrode 12 (upper side in FIG. 2 ), which will be described later, than another detection line 60 of another detection line array 61 that is located on the opposite side of the frame portion 54 from the one detection line array 61. Note that the one detection line 60 is the Nth (N is a natural number) detection line of the one detection line array 61 when counted from the positive electrode terminal electrode 12 side, and the other detection line 60 is the Nth (N is a natural number) detection line of the other detection line array 61 when counted from the positive electrode terminal electrode 12 side.

[0028] The electrode stack 10 has a plurality of bipolar electrodes 11, a positive terminal electrode 12, a negative terminal electrode 13, and a plurality of separators 14. The plurality of bipolar electrodes 11, the positive terminal electrodes 12, the negative terminal electrodes 13, and the plurality of separators 14 are stacked along the Z-axis direction (first direction). That is, the electrode stack includes a plurality of electrodes (bipolar electrodes 11, positive terminal electrodes 12, negative terminal electrodes 13) stacked along the Z-axis direction.

[0029] The bipolar electrode 11 includes a current collector 15, a first active material layer 16, and a second active material layer 17. When viewed from the Z-axis direction, the current collector 15 has, for example, a rectangular shape. The current collector 15 includes a surface 15a (second surface) and a surface 15b (first surface) opposite to the surface 15a.

[0030] The first active material layer 16 is provided on the surface 15a. The first active material layer 16 is, for example, a positive electrode active material layer. When viewed from the Z-axis direction, the first active material layer 16 has, for example, a rectangular shape. The surface 15a includes an unformed region where the first active material layer 16 is not provided. When viewed from the Z-axis direction, the unformed region surrounds the first active material layer 16.

[0031] The second active material layer 17 is provided on the surface 15b. The polarity of the second active material layer 17 is different from the polarity of the first active material layer 16. The second active material layer 17 is, for example, a negative electrode active material layer. When viewed from the Z-axis direction, the second active material layer 17 has, for example, a rectangular shape. The surface 15b includes an unformed region where the second active material layer 17 is not provided. When viewed from the Z-axis direction, the unformed region surrounds the second active material layer 17. When viewed from the Z-axis direction, the area of ​​the second active material layer 17 is larger than the area of ​​the first active material layer 16. When viewed from the Z-axis direction, the outer edge of the second active material layer 17 is located outside the outer edge of the first active material layer 16.

[0032] The multiple bipolar electrodes 11 are stacked such that the first active material layer 16 of one bipolar electrode 11 faces the second active material layer 17 of another bipolar electrode 11. In other words, the multiple bipolar electrodes 11 are stacked such that, of adjacent bipolar electrodes 11, the surface 15a of the current collector 15 of one bipolar electrode 11 faces the surface 15b of the current collector 15 of the other bipolar electrode 11.

[0033] The positive terminal electrode 12 is disposed on one side of the plurality of bipolar electrodes 11 in the Z-axis direction. The positive terminal electrode 12 includes a current collector 15 and a first active material layer 16. The positive terminal electrode 12 differs from the bipolar electrode 11 primarily in that it does not include a second active material layer 17. The other configuration of the positive terminal electrode 12 may be the same as that of the bipolar electrode 11. The first active material layer 16 of the positive terminal electrode 12 faces the second active material layer 17 of the bipolar electrode 11. That is, the positive terminal electrode 12 is stacked such that the surface 15a of the current collector 15 of the positive terminal electrode 12 faces the surface 15b of the current collector 15 of the bipolar electrode 11 adjacent to the positive terminal electrode 12.

[0034] The negative electrode terminal electrode 13 is disposed on the other side of the plurality of bipolar electrodes 11 in the Z-axis direction. The negative electrode terminal electrode 13 includes a current collector 15 and a second active material layer 17. The negative electrode terminal electrode 13 differs from the bipolar electrode 11 mainly in that it does not include a first active material layer 16. The other configuration of the negative electrode terminal electrode 13 may be the same as that of the bipolar electrode 11. The second active material layer 17 of the negative electrode terminal electrode 13 faces the first active material layer 16 of the bipolar electrode 11. That is, the negative electrode terminal electrode 13 is stacked such that the surface 15b of the current collector 15 of the negative electrode terminal electrode 13 faces the surface 15a of the current collector 15 of the bipolar electrode 11 adjacent to the negative electrode terminal electrode 13.

[0035] The outer edges of the current collectors 15 of each electrode form the side surfaces of the electrode stack 10. Internal spaces S for accommodating an electrolyte are formed between each bipolar electrode 11, between the bipolar electrode 11 and the positive terminal electrode 12, and between the bipolar electrode 11 and the negative terminal electrode 13.

[0036] Separators 14 are disposed between each bipolar electrode 11, between the bipolar electrode 11 and the positive terminal electrode 12, and between the bipolar electrode 11 and the negative terminal electrode 13. The separators 14 are disposed between the opposing first and second active material layers 16 and 17. The separators 14 are, for example, sheet-shaped. When viewed from the Z-axis direction, the outer edges of the separator 14 are located further outward than the outer edges of the first and second active material layers 16 and 17. The separators 14 allow charge carriers such as lithium ions to pass through. The separators 14 separate adjacent electrodes, thereby preventing electrical shorts due to contact between the electrodes. The separators 14 absorb and retain the electrolyte.

[0037] The current collector 15 has the function of maintaining the flow of current in the first active material layer 16 and the second active material layer 17 during discharging or charging of the energy storage module 1. The current collector 15 is, for example, a chemically inactive electrical conductor. The material of the current collector 15 is, for example, a metal material, a conductive resin material, a conductive inorganic material, etc. The conductive resin material is, for example, a conductive polymer material, or a non-conductive polymer material to which a conductive filler has been added. When the current collector 15 has multiple layers, the material of each layer may be any of the materials described above. A coating layer (coating layer 80 described below) may be formed on the surface of the current collector 15. The coating layer may be formed by a known method such as plating or spray coating. The coating layer is, for example, a carbon coating.

[0038] The current collector 15 has, for example, a plate, foil, sheet, film, or mesh shape. The current collector 15 may be, for example, an aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil. The current collector 15 may be an alloy foil or clad foil of the above metals. When the current collector 15 is foil-shaped, the thickness of the current collector 15 is, for example, 1 μm or more and 100 μm or less. The current collector 15 may be a laminate having multiple metal layers. The current collector 15 may be, for example, a laminate in which an aluminum layer and a copper layer are integrated. The current collector 15 may include, for example, an aluminum foil and copper plating formed on one side of the aluminum foil. The current collector 15 may include multiple metal foils bonded together with a conductive adhesive.

[0039] The first active material layer 16 includes a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. The positive electrode active material is, for example, a composite oxide, metallic lithium, or sulfur. The composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. The composite oxide is, for example, olivine-type lithium iron phosphate (LiFePO ４ ), LiCoO ２ , LiNiMnCoO ２ etc.

[0040] The second active material layer 17 includes a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions. Examples of the negative electrode active material include graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, soft carbon, metal compounds, elements or compounds thereof that can be alloyed with lithium, and boron-doped carbon. Examples of the elements that can be alloyed with lithium include silicon and tin.

[0041] Each of the first active material layer 16 and the second active material layer 17 may contain a binder and a conductive additive in addition to the active material. The binder functions to bind the active material or conductive additive together and maintain 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; alkoxysilyl group-containing resins; acrylic resins such as polyacrylic acid and polymethacrylic acid; styrene-butadiene rubber; carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinked bodies; and starch-acrylic acid graft polymers. These binders may be used alone or in combination. The conductive additive is a conductive material that enhances electrical conductivity. Examples of conductive additives include acetylene black, carbon black, and graphite. Examples of viscosity-adjusting solvents include N-methyl-2-pyrrolidone.

[0042] Formation of the first active material layer 16 on the surface 15a and the second active material layer 17 on the surface 15b can be achieved by conventional methods such as roll coating, die coating, dip coating, doctor blade coating, spray coating, and curtain coating. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive additive are mixed to produce a slurry-like active material layer-forming composition, which is then applied to the surface 15a or the surface 15b and dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The dried electrode may be compressed to increase electrode density.

[0043] The electrolyte solution is accommodated in the internal space S. The separator 14 is impregnated with the electrolyte solution. The electrolyte solution is, for example, a liquid containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The electrolyte salt of the electrolyte solution is, for example, LiClO ４ , LiAsF ６ , LiPF ６ , LiBF ４ , LiCF ３ SO ３ , LiN(FSO ２ ) ２ , LiN(CF ３ SO ２ ) ２ The non-aqueous solvent is a cyclic carbonate, a cyclic ester, a chain carbonate, a chain ester, an ether, etc. Two or more of these known solvent materials may be used in combination.

[0044] The sealing body 20 has a sealing material 41, a spacer 42, and a welded portion 43. The sealing material 41 has, for example, a rectangular frame shape. The sealing material 41 is provided on the peripheral portion 15c of each current collector 15 and covers the peripheral portion 15c. The sealing material 41 is provided on the surface 15a and the surface 15b of each current collector 15. The sealing material 41 is formed in a frame shape so as to surround the first active material layer 16 and the second active material layer 17 when viewed from the Z-axis direction. The inner edge of the sealing material 41 is separated from the first active material layer 16 and the second active material layer 17. The sealing material 41 is welded to the current collector 15.

[0045] The spacer 42 has, for example, a rectangular frame shape. The spacer 42 is provided between adjacent sealing materials 41. The spacer 42 is sandwiched between adjacent sealing materials 41. The inner peripheral portion of the spacer 42 overlaps with the second active material layer 17 when viewed from the Z-axis direction. The inner peripheral portion of the spacer 42 is located between the surface 15a of the current collector 15 and the second active material layer 17 (separator 14). The welded portion 43 is formed by welding and integrating the outer edges of each sealing material 41 and each spacer 42. The welded portion 43 has, for example, a rectangular cylindrical shape.

[0046] In this way, in the energy storage module 1, the sealing material 41 provided on each electrode is stacked along the Z-axis direction via spacers 42 so as to surround the electrode stack 10, thereby forming a sealing body 20 for sealing the internal space S formed between adjacent electrodes in the Z-axis direction.

[0047] The sealant 41 and the spacer 42 are made of, for example, acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene. The sealant 41 and the spacer 42 are both electrolyte-resistant. The sealant 41 and the spacer 42 may be made of the same material or different materials. In this embodiment, the sealant 41 is made of, for example, acid-modified polyethylene or acid-modified polypropylene. In this embodiment, the spacer 42 is made of, for example, polyethylene or polypropylene. Acid-modified polyethylene and acid-modified polypropylene are more easily bonded to metal than non-acid-modified polyethylene and non-acid-modified polypropylene. When the current collector 15 is made of metal, the bonding strength of the sealant 41 to the current collector 15 can be improved by forming the sealant 41 from acid-modified polyethylene or acid-modified polypropylene. In this embodiment, the current collector 15 is coated with a carbon coating (coating layer 80) described below, and the sealing material 41 is bonded via the carbon coating, thereby improving the bonding strength of the sealing material 41 to the current collector 15 compared to when the sealing material 41 is bonded directly to the current collector 15.

[0048] The detection wires 60 are bonded to the surfaces 15b of the current collectors 15 and are electrically connected to the surfaces 15b. The detection wires 60 are located between the surfaces 15b of the current collectors 15 and the sealing material 41. The detection wires 60 pass through the sealing body 20 and are drawn out to the outside of the sealing body 20. The detection wires 60 are made of, for example, a metal. The detection wires 60 are, for example, stainless steel foil.

[0049] Next, a description will be given of a method for manufacturing an energy storage module according to this embodiment. In this embodiment, the above-described energy storage module 1 is manufactured. FIG. 4 is a flowchart showing one step of the method for manufacturing an energy storage module according to this embodiment. FIGS. 5 to 7 are schematic diagrams showing the steps shown in FIG. 4. Note that the Cartesian coordinate system shown in FIG. 5 and subsequent figures is the same as the Cartesian coordinate system shown in FIGS. 1 to 3 for ease of understanding, but the directions during manufacturing do not need to match the directions in the manufactured energy storage module 1.

[0050] As shown in FIGS. 4 and 5 , in the energy storage module manufacturing method according to this embodiment, first, electrodes are prepared (step S101: preparation step). More specifically, in step S101, as shown in FIG. 5 , a current collector 15 is prepared, and a coating layer 80 is formed on the surfaces 15 a and 15 b of the current collector 15 (formation step). The coating layer 80 can be formed, for example, by applying a carbon coating to the surfaces 15 a and 15 b. Here, the coating layer 80 is first formed on the entire surfaces 15 a and 15 b. Then, in step S101, a portion of the coating layer 80 on the surface 15 b is removed by irradiating it with laser light (for example, by ablation processing of the coating layer), thereby forming an exposed portion 81 that is exposed from the coating layer 80 on the surface 15 b (removal step).

[0051] In a later step S102, the detection wire 60 is ultrasonically bonded to the surface 15b of the current collector 15 in the exposed portion 81. In step S101, the exposed portion 81 is formed so that the area of ​​the exposed portion 81 when viewed from a direction intersecting the surface 15b (here, the Z-axis direction) is larger than the area of ​​the region P where the surface 15b of the current collector 15 and the detection wire 60 overlap in step S102. In a later step S103, a rectangular frame-shaped sealant 71 (along the peripheral edge 15c) is bonded to the surface 15b of the current collector 15. In step S101, the exposed portion 81 is formed so that when the sealant 71 is placed on the current collector 15 in step S103, the exposed portion 81 does not reach the inner edge 41e of the sealant 71. This allows the exposed portion 81 to be covered by the sealant 71 when the sealant 71 is placed on the current collector 15 in step S103, as described below.

[0052] As described above, in step S101, the coating layer 80 is formed to expose a portion of the surface 15b of the current collector 15, and the coating layer 80 is formed over the entire surface 15a of the current collector 15. After that, the first active material layer 16 is formed on the surface 15a via the coating layer 80, and the second active material layer 17 is formed on the surface 15b. This completes the preparation of the bipolar electrode 11. In step S101, the positive terminal electrode 12 and the negative terminal electrode 13 are prepared in a similar manner.

[0053] 4 and 6, the first electrode unit U1 is constructed by joining the detection wire 60 to the electrode (step S102: terminal joining step). In the illustrated example, the detection wire 60 is joined (e.g., welded) to the surface 15b of the peripheral portion 15c of the current collector 15 of the bipolar electrode 11, thereby constructing the first electrode unit U1 including the bipolar electrode 11.

[0054] In this embodiment, surface 15b has a rectangular shape including four sides. In step S101, detection line 60 is joined to a first side 151 of the four sides of surface 15b. At this time, detection line 60 is joined to an exposed portion 81 of surface 15b. Therefore, exposed portion 81 is provided on first side 151. As described above, in this embodiment, exposed portion 81 is formed to be wider than region P where surface 15b and detection line 60 overlap when viewed from a direction intersecting surface 15b (Z-axis direction). Therefore, here, detection line 60 is arranged and joined to surface 15b so that the entire detection line 60 overlaps exposed portion 81 when viewed from a direction intersecting surface 15b.

[0055] Here, the current collector 15 and the detection wire 60 are sandwiched between the anvil A2 and the horn A1 (ultrasonic horn) and ultrasonically bonded (welded). More specifically, in step S102, the anvil A2 is placed under the detection wire 60 on the surface 15b side of the current collector 15, and the horn A1 is brought into contact with the surface 15a of the current collector 15 to perform ultrasonic bonding, thereby bonding the detection wire 60 to the surface 15b. At this time, vibration is applied to the current collector 15 and the detection wire 60. Here, when viewed from a direction intersecting the surface 15b, the area of ​​the exposed portion 81 is made larger than the area of ​​the surface 15b that the horn A1 contacts. That is, in step S101, the exposed portion 81 is formed so that the area of ​​the exposed portion 81 when viewed from a direction intersecting the surface 15b is larger than the area of ​​the surface 15a that the horn A1 contacts in step S102. In step S101, the detection wires 60 are also joined to the positive terminal electrode 12 and the negative terminal electrode 13 in a similar manner to form a first electrode unit U1 including each of the positive terminal electrode 12 and the negative terminal electrode 13.

[0056] 4 and 7 , a sealant 41 is placed on the surface 15b and the detection lines 60 in the peripheral portion 15c of the current collector 15 of the first electrode unit U1, thereby forming a second electrode unit U2 (step S103). More specifically, in step S103, a sealant 71, which is the basis for the sealant 41, is placed on the surface 15b, and another sealant 71 is placed on the surface 15a. The pair of sealants 71 are integrated into the sealant 41 in a later step. Then, the sealant 71 is welded to the surface 15b of the current collector 15 of the second electrode unit U2 and the detection lines 60 on the surface 15b, and the sealant 71 is welded to the surface 15a of the current collector 15, thereby forming a third electrode unit.

[0057] Thus, in step S103, the sealant 71 is bonded to the surfaces 15a and 15b of the peripheral portion 15c of the current collector 15 via the coating layer 80 (sealant bonding step). The sealant 71 is formed in a rectangular frame shape that overlaps the peripheral portion 15c of the current collector 15 when viewed from a direction intersecting with the surface 15b. Then, in step S103, the sealant 71 is positioned so that it overlaps the exposed portion 81 when viewed from a direction intersecting with the surface 15b. As described above, the exposed portion 81 is formed so as not to reach the inner edge 41e of the sealant 41. Therefore, even in the region of the surface 15b where the exposed portion 81 is provided, the coating layer 80 remains in the extension direction of the detection line 60 (here, the Y-axis direction), allowing for suitable welding of the sealant 71 via the coating layer 80. Furthermore, as described above, the exposed portion 81 can be covered with the sealant 71, ensuring insulation.

[0058] As a result, welding of the sealant 71 is completed at the first side portion 151 (and the same portion on the surface 15a) where the detection line 60 is provided on the surface 15b of the current collector 15. Thereafter, welding of the sealant 71 is performed at the three second side portions 152 (and the same portions on the surface 15a) where the detection line 60 is not provided on the surface 15b of the current collector 15. As a result, the frame-shaped sealant 71 is welded to the current collector 15 over its entirety, and the pair of sealants 71 form the sealant 41, and a third electrode unit including the sealant 41 is configured.

[0059] 4 , in the next step, a plurality of third electrode units configured as described above are stacked along the Z-axis direction via separators 14 and spacers 42 (step S104), and a plurality of sealants 41 (of the plurality of third electrode units) stacked on top of each other are integrated to form the electrode stack 10 and the sealed body 20 (step S105). In step S105, the sealants 41 and the spacers 42 are welded to each other to form welded portions 43, thereby forming the sealed body 20. In this way, the sealed body 20 is provided so as to surround the electrode stack 10 by stacking a plurality of sealants 41 (and spacers 42) welded to the current collector 15 via the coating layer 80 at the peripheral portion 15c of the current collector 15 along the Z-axis direction.

[0060] Thereafter, subsequent processes such as a process of forming a liquid injection port 50 in the sealing body 20 and a process of injecting the electrolyte into the internal space S using the liquid injection port 50 are carried out, and the energy storage module 1 is manufactured.

[0061] As described above, in the method for manufacturing an energy storage module according to this embodiment, in preparing an electrode, a coating layer 80 is formed on the surface 15b of the current collector 15 of the electrode, and then a portion of the coating layer 80 is removed by irradiating it with laser light to form an exposed portion 81 that is exposed from the coating layer 80 on the surface 15b. Then, the detection wire 60 is ultrasonically bonded to the surface 15b of the current collector 15 at the exposed portion 81. Graph G0 in FIG. 8 shows the relationship between the bonding time and the bonding strength when the detection wire 60 is ultrasonically bonded to the surface 15b of the current collector 15 on which the coating layer 80 is provided, and graph G1 in FIG. 8 shows the relationship between the bonding time and the bonding strength when the detection wire 60 is ultrasonically bonded to the surface 15b of the current collector 15 on which the coating layer 80 is not provided.

[0062] As shown in FIG. 8 , ultrasonic bonding via the coating layer 80 (graph G0) results in a lower increase in bond strength with increasing bonding time compared to ultrasonic bonding without the coating layer 80 (graph G1). In other words, it is difficult to sufficiently increase the bond strength. Furthermore, when ultrasonic bonding is performed on the surface 15 b of the current collector 15 on which the coating layer 80 is provided, the time required for the bond strength between the current collector 15 and the detection wire 60 to reach a specified value (the time required to perform ultrasonic bonding) becomes longer. Furthermore, ultrasonic bonding over a long period of time results in excessive vibration of the current collector 15 and the detection wire 60, which may result in deterioration of the quality of the current collector 15 and the detection wire 60.

[0063] In contrast, in the energy storage module manufacturing method according to this embodiment, the detection wire 60 is ultrasonically bonded to the surface 15b of the current collector 15 in the exposed portion 81 of the surface 15b of the current collector 15 as described above. Therefore, in at least a portion of the region P where the current collector 15 and the detection wire 60 overlap when viewed from a direction intersecting the surface 15b (the bonded portion between the current collector 15 and the detection wire 60), ultrasonic bonding can be performed without the coating layer 80 being interposed between the surface 15b of the current collector 15 and the detection wire 60. Thus, forming the coating layer 80 on the surface 15b of the current collector 15 allows the sealing material 41 to be bonded appropriately, while also suitably improving the bonding strength between the current collector 15 and the detection wire 60. Furthermore, the ultrasonic bonding of the detection wire 60 to the current collector 15 can be prevented from taking a long time.

[0064] Furthermore, in the energy storage module manufacturing method according to this embodiment, in step S101, covering layer 80 is formed so that the area of ​​exposed portion 81 when viewed from a direction intersecting surface 15b (Z-axis direction) is larger than the area of ​​region P where surface 15b and detection line 60 overlap when viewed from the direction intersecting surface 15b. This makes it possible to position region P entirely within exposed portion 81, thereby reliably improving the bonding strength between current collector 15 and detection line 60.

[0065] Furthermore, in the energy storage module manufacturing method according to this embodiment, in step S102, a horn A1 is brought into contact with surface 15a of current collector 15 to perform ultrasonic bonding, thereby bonding detection wire 60 to surface 15b. Then, in the removal step of step S101, exposed portion 81 is formed so that the area of ​​exposed portion 81 when viewed from a direction intersecting surface 15b is larger than the area of ​​surface 15a that is contacted by horn A1 in step S102. This makes it possible to more reliably improve the bonding strength between current collector 15 and detection wire 60.

[0066] Furthermore, in the energy storage module manufacturing method according to this embodiment, the sealing material 71 is formed in a frame shape that overlaps the peripheral portion 15c of the current collector 15 when viewed from a direction intersecting the surface 15b, and in step S103, the sealing material 71 is arranged so that the sealing material 71 overlaps the exposed portion 81 when viewed from a direction intersecting the surface 15b. This makes it possible to cover the exposed portion 81 with the sealing material 41. Note that in this embodiment, the exposed portion 81 is sealed by the sealing body 20 by being located inside (toward the internal space S) more than the welded portion 43 of the sealing body 20 when viewed from the Z-axis direction.

[0067] The above embodiment has described one aspect of the energy storage module manufacturing method according to the present disclosure. Therefore, the energy storage module manufacturing method according to the present disclosure is not limited to the above embodiment and can be modified as desired.

[0068] For example, in the above embodiment, an example has been described in which ultrasonic bonding is performed by placing the anvil A2 under the detection wire 60 and bringing the horn A1 into contact with the surface 15a of the current collector 15. However, ultrasonic bonding may also be performed by placing the anvil A2 under the surface 15a and bringing the horn A1 into contact with the detection wire 60 arranged on the surface 15b of the current collector 15. In this case as well, vibration is applied to the current collector 15 and the detection wire 60.

[0069] Furthermore, the area of ​​exposed portion 81 when viewed from a direction intersecting surface 15b is not limited to being larger than the area of ​​region P where surface 15b and detection line 60 overlap when viewed from that direction, and may be equal to or smaller than the area of ​​region P when viewed from that direction. In other words, it is sufficient that exposed portion 81 is provided in at least a part of region P.

[0070] Furthermore, the method of removing a portion of the coating layer 80 to form the exposed portion 81 is not limited to removal by irradiation with laser light as described above, but may be other methods such as providing a mask in the area on the surface 15b where the exposed portion 81 is to be formed when forming the coating layer 80, or removal by a method other than irradiation with laser light.

[0071] The following additional notes are provided regarding the above embodiment.

[0072] The energy storage module manufacturing method according to the appendix may be [1] "an energy storage module manufacturing method for manufacturing an energy storage module including: an electrode laminate configured by laminating, along a first direction, a plurality of electrodes, each electrode including a current collector and an active material layer and a coating layer formed on a surface of the current collector; a sealing body provided so as to surround the electrode laminate by laminating, along the first direction, a plurality of sealing materials welded to the current collector at a peripheral portion thereof via the coating layer; and a plurality of terminals joined to each of the plurality of current collectors and extended to the outside of the sealing body, the method including: a preparation step of preparing the electrodes; and a terminal joining step of ultrasonically joining the terminals to a first surface, which is the surface of the current collector, the preparation step including: a formation step of forming the coating layer on the first surface; and a removal step of irradiating laser light to remove a portion of the coating layer to form an exposed portion that is exposed from the coating layer on the first surface; and the terminal joining step ultrasonically joining the terminals to the exposed portions."

[0073] The storage module manufacturing method according to the appendix may be [2] "the storage module manufacturing method described in [1] above, in which in the removal process, the exposed portion is formed so that the area of ​​the exposed portion when viewed from a direction intersecting the first surface is larger than the area of ​​the region where the first surface and the terminal overlap when viewed from a direction intersecting the first surface."

[0074] The storage module manufacturing method according to the appendix may be [3] "the storage module manufacturing method described in [1] or [2] above, wherein in the terminal joining step, an ultrasonic horn is applied to a second surface of the surface of the current collector opposite the first surface to perform the ultrasonic joining, thereby joining the terminal to the first surface, and in the removing step, the exposed portion is formed so that the area of ​​the exposed portion when viewed from a direction intersecting the first surface is larger than the area of ​​the second surface that is in contact with the ultrasonic horn in the terminal joining step."

[0075] The storage module manufacturing method according to the appendix may be [4] "the storage module manufacturing method according to any one of the above [1] to [3], further comprising a sealing material joining step of joining the sealing material to the surface of the peripheral portion of the current collector via the coating layer."

[0076] The storage module manufacturing method according to the appendix may be [5] "the storage module manufacturing method described in [4] above, wherein the sealing material is formed in a frame shape that overlaps the peripheral portion of the current collector when viewed from a direction intersecting the first surface, and in the sealing material joining step, the sealing material is positioned so that the sealing material overlaps the exposed portion when viewed from a direction intersecting the first surface."

[0077] The method for producing an electric storage module according to the appendix is ​​the method for producing an electric storage module according to any one of [1] to [5] above, wherein [6] "the electrode laminate includes a bipolar electrode as the electrode, the bipolar electrode includes the current collector including the first surface and a second surface opposite to the first surface, a first active material layer as the active material layer provided on the second surface, and a second active material layer as the active material layer provided on the first surface and having a polarity different from that of the first active material layer, the forming step forms the covering layer on the first surface and the second surface, and the removing step removes a part of the covering layer formed on the first surface by irradiating it with the laser light, thereby forming the exposed portion that is exposed from the covering layer on the first surface."

[0078] 1...storage module, 10...electrode laminate, 11...bipolar electrode (electrode), 12...positive terminal electrode (electrode), 13...negative terminal electrode (electrode), 15...current collector, 15b...surface, 15c...periphery, 20...sealing body, 41, 71...sealing material, 60...detection line (terminal), 80...covering layer, 81...exposed portion, P...region.

Claims

1. A method for manufacturing an energy storage module comprising: an electrode laminate formed by laminating, along a first direction, a plurality of electrodes, each electrode including a current collector and an active material layer and a coating layer formed on the surface of the current collector; a sealing body provided so as to surround the electrode laminate by laminating, along the first direction, a plurality of sealing materials welded to the current collector at the peripheral edge of the current collector via the coating layer; and a plurality of terminals joined to each of the plurality of current collectors and extended to the outside of the sealing body, the method comprising: a preparation step of preparing the electrodes; and a terminal joining step of ultrasonically joining the terminals to a first surface, which is the surface of the current collector, 2. The method for manufacturing a storage module according to claim 1, wherein in the removing step, the exposed portion is formed so that the area of ​​the exposed portion when viewed in a direction intersecting the first surface is larger than the area of ​​the region where the first surface and the terminal overlap when viewed in a direction intersecting the first surface.

3. The method for manufacturing a storage module according to claim 1 or 2, wherein in the terminal joining step, an ultrasonic horn is applied to a second surface of the current collector opposite the first surface to perform the ultrasonic joining, thereby joining the terminal to the first surface, and in the removal step, the exposed portion is formed so that the area of ​​the exposed portion when viewed in a direction intersecting the first surface is larger than the area of ​​the second surface that is in contact with the ultrasonic horn in the terminal joining step.

4. The method for manufacturing an electric storage module according to any one of claims 1 to 3, further comprising a sealing material joining step of joining the sealing material to the surface of the current collector at the periphery thereof via the covering layer.

5. The method for manufacturing a storage module according to claim 4, wherein the sealing material is formed in a frame shape that overlaps the peripheral portion of the current collector when viewed from a direction intersecting the first surface, and in the sealing material joining step, the sealing material is positioned so that the sealing material overlaps the exposed portion when viewed from a direction intersecting the first surface.

6. The method for manufacturing an electric storage module according to any one of claims 1 to 5, wherein the electrode laminate includes a bipolar electrode as the electrode, the bipolar electrode including: the current collector including the first surface and a second surface opposite to the first surface; a first active material layer as the active material layer provided on the second surface; and a second active material layer as the active material layer provided on the first surface and having a polarity different from that of the first active material layer; and wherein the forming step forms the covering layer on the first surface and the second surface, and the removing step removes a part of the covering layer formed on the first surface by irradiating it with the laser light, thereby forming the exposed portion that is exposed from the covering layer on the first surface.

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