Electrode manufacturing method

Abstract

The present invention provides a method for producing an electrode which is provided with a collector having a polygonal shape with at least one side of more than 1 meter, an active material layer that is provided on the surface of the collector, and at least one sealing member that is welded to the surface of the collector, the method comprising: an arrangement step in which the sealing member is arranged on the surface of the collector along the side; and a welding step in which an object part is heated by having a jig in area contact with the object part and pressing the object part against the collector. The welding step is performed a plurality of times between the both ends of the sealing member; and in the second and subsequent welding steps, a portion of the sealing member, at least a part of the portion being deviated from the object part in the immediately preceding welding step, is taken as the object part.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode. [Background technology]

[0002] In an electricity storage device in which multiple electrodes are stacked, a sealing member may be welded to the current collector when manufacturing the electrode, for the purpose of insulating the current collectors from each other. For example, in the electrode manufacturing method described in Patent Document 1, a jig is brought into contact with the sealing member placed on the current collector and heated with the jig to weld the sealing member to the current collector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-106963 Summary of the Invention [Problem to be solved by the invention]

[0004] When a sealing member made of a resin material is welded to a current collector, thermal shrinkage occurs in the portion of the sealing member welded to the current collector. At this time, the larger the portion of the sealing member welded to the current collector, the greater the amount of thermal shrinkage of the sealing member. The greater the amount of thermal shrinkage of the sealing member, the greater the contraction force transmitted to the current collector due to the thermal shrinkage of the sealing member, making the current collector more likely to deform. [Means for solving the problem]

[0005] In a method for manufacturing an electrode according to one embodiment of the present disclosure, the electrode comprises a current collector that is polygonal in shape in a plan view, with at least one side longer than one meter, an active material layer provided on a surface of the current collector, and one or more sealing members welded to the surface of the current collector, and the manufacturing method includes: an arrangement step of arranging the sealing members on the surface of the current collector along the sides; and a welding step of bringing a jig into surface contact with a target portion of the sealing member, the target portion having a dimension in the direction in which the side extends that is smaller than the side, and heating the target portion while pressing the target portion against the current collector, thereby forming a welded portion in which the target portion is welded to the surface of the current collector, the welding step being performed multiple times between both ends of the sealing member in the direction in which the side extends, and in the second and subsequent welding steps, the target portion is a portion of the sealing member that is at least partially shifted in the direction in which the side extends from the target portion in the previous welding step.

[0006] According to the above method, a welding process is performed in which a jig is brought into surface contact with a target portion of the sealing member, the target portion having a dimension in the direction of extension of the side smaller than the side, and the target portion is pressed against the current collector while being heated with the jig, thereby forming a welded portion in which the target portion is welded to the surface of the current collector. Therefore, compared to when the dimension of the target portion in the direction of extension of the side is the same as the dimension of the side, the smaller dimension of the target portion reduces the amount of thermal expansion of the sealing member. The smaller amount of thermal expansion of the sealing member reduces the amount of thermal contraction of the sealing member. This reduces the contraction force transmitted from the sealing member to the current collector due to thermal contraction of the sealing member. Therefore, deformation of the current collector that occurs when the sealing member is welded to the current collector can be reduced.

[0007] In the method for manufacturing an electrode, in the arranging step, the sealing members may be arranged on both sides of the current collector, and the welding step may be performed on the sealing members arranged on both sides of the current collector.

[0008] According to the above method, in the placement process, sealing members are placed on both sides of the current collector, and the welding process is performed on the sealing members placed on both sides of the current collector, thereby reducing deformation of the current collector that occurs when the sealing members are welded to both sides of the current collector.

[0009] In the method for manufacturing an electrode, in the second or subsequent welding step, a part of the target portion in the extending direction of the side may overlap with the target portion in the previous welding step. According to the above method, in the second and subsequent welding processes, a portion of the target portion in the direction of the side extension overlaps with the target portion in the previous welding process. Therefore, even if the relative position of the target portion in the direction of the side extension with respect to the jig is shifted from its original position during the welding process, the portion of the target portion that overlaps with the target portion in the previous welding process in the direction of the side extension of the target portion only increases or decreases. This makes it less likely that a portion of the multiple target portions will not be welded to the current collector. Therefore, poor welding of the sealing member to the current collector can be reduced.

[0010] In the electrode manufacturing method, the jig has a heater portion that heats the target portion while making surface contact with the target portion, and corner portions that are located around the heater portion and come into contact with the sealing member when the target portion is heated by the heater portion, and the corner portions may be curved.

[0011] According to the above method, the jig has a corner that comes into contact with the sealing member when the target portion is heated by the heater unit. If this corner is curved, it is possible to reduce the occurrence of local swelling of the sealing member caused by the sealing member being pressed by the corner when the corner comes into contact with the sealing member.

[0012] In the method for manufacturing an electrode, the dimension of the target portion in the direction in which the side extends may be 720 mm or less. According to the above method, the dimension of the target portion in the direction in which the side extends is 720 mm or less, which further reduces deformation of the current collector that occurs when the seal member is welded to the current collector. [Effects of the Invention]

[0013] According to this invention, deformation of the current collector that occurs when the seal member is welded to the current collector can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of an electricity storage device according to an embodiment; [Figure 2] 2 is an enlarged cross-sectional view showing a part of the electricity storage device of FIG. 1. FIG. [Figure 3] 2 is a top view of an electrode included in the power storage device of FIG. 1. FIG. [Figure 4] 10 is a cross-sectional view illustrating a welding step for a first target portion in a manufacturing method of an electrode according to one embodiment. FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. [Figure 7] 10 is a cross-sectional view illustrating a welding step for a second target portion in a manufacturing method of an electrode according to one embodiment. FIG. [Figure 8] 10 is a cross-sectional view illustrating a welding step for a third target portion in a manufacturing method of an electrode according to one embodiment. FIG. [Figure 9] 10A and 10B are cross-sectional views illustrating the formation of a sealing portion in a method for manufacturing an electrode according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of a method for manufacturing an electrode will be described with reference to Figures 1 to 9. For convenience of explanation, the electricity storage device and the electrode will be described before the method for manufacturing the electrode. <Electricity storage device> As shown in Fig. 1, the energy storage device 10 includes a laminate 10a and a sealing body 15. The laminate 10a is formed by stacking a plurality of electrodes 11 between a positive terminal electrode 36 and a negative terminal electrode 37. The energy storage device 10 is, for example, a lithium ion secondary battery. Hereinafter, the direction in which the plurality of electrodes 11 are stacked will be simply referred to as the stacking direction X.

[0016] <Electrode> As shown in FIGS. 1 and 2 , each of the multiple electrodes 11 includes a current collector 12, a positive electrode active material layer 23, and a negative electrode active material layer 33. The current collector 12 is sheet-shaped. The current collector 12 has a first surface 12a and a second surface 12b that face opposite to each other in the stacking direction X. The first surface 12a of the current collector 12 is provided with a positive electrode active material layer 23, and the second surface 12b is provided with a negative electrode active material layer 33. In other words, each of the multiple electrodes 11 is a bipolar electrode. In the laminate 10a, the multiple electrodes 11 are stacked such that the first surface 12a of the current collector 12 of one of two electrodes 11 adjacent to each other in the stacking direction X faces the second surface 12b of the current collector 12 of the other electrode 11, with a separator 35 sandwiched between them. That is, the multiple electrodes 11 are stacked so that the positive electrode active material layer 23 of one electrode 11 and the negative electrode active material layer 33 of the other electrode 11 adjacent in the stacking direction X face each other with the separator 35 interposed therebetween.

[0017] In a plan view seen from the stacking direction X (hereinafter simply referred to as a plan view), the positive electrode active material layer 23 is formed in the central portion of the first surface 12a of the current collector 12. In the plan view, the peripheral portion of the first surface 12a of the current collector 12 is a positive electrode uncoated portion 12c where the positive electrode active material layer 23 is not provided. The positive electrode uncoated portion 12c is arranged so as to surround the periphery of the positive electrode active material layer 23 in the plan view. In the plan view, the negative electrode active material layer 33 is formed in the central portion of the second surface 12b of the current collector 12. In the plan view, the peripheral portion of the second surface 12b of the current collector 12 is a negative electrode uncoated portion 12d where the negative electrode active material layer 33 is not provided. The negative electrode uncoated portion 12d is arranged so as to surround the periphery of the negative electrode active material layer 33 in the plan view.

[0018] The positive electrode active material layer 23 and the negative electrode active material layer 33 are disposed so as to face each other in the stacking direction X. The negative electrode active material layer 33 is formed, for example, to be slightly larger than the positive electrode active material layer 23. In a plan view, the entire region where the positive electrode active material layer 23 is formed is located within the region where the negative electrode active material layer 33 is formed.

[0019] <Current collector details> In this embodiment, the current collector 12 is formed by integrating a sheet-like positive electrode current collector 22 and a negative electrode current collector 32. The first surface 12a of the current collector 12 is formed by one surface of the positive electrode current collector 22, and the second surface 12b is formed by one surface of the negative electrode current collector 32. The positive electrode current collector 22 and the negative electrode current collector 32 may be integrated by bonding the surface of the positive electrode current collector 22 opposite the first surface 12a to the surface of the negative electrode current collector 32 opposite the second surface 12b. The positive electrode current collector 22 and the negative electrode current collector 32 have the same shape in a plan view.

[0020] As shown in FIG. 3, the current collector 12 has a polygonal shape with multiple (three or more) sides 12f in a plan view. Specifically, the current collector 12 has four sides 12f and is rectangular in a plan view. The outer edge 12e of the current collector 12 is formed by the four sides 12f. Two of the sides 12f are also referred to as short sides 12g, and the two sides 12f longer than the short sides 12g are also referred to as long sides 12h. The short sides 12g and the long sides 12h each exceed 1 meter. The short sides 12g are, for example, 1.2 meters. The long sides 12h are, for example, 1.5 meters.

[0021] 1, the positive electrode current collector 22 and the negative electrode current collector 32 are chemically inactive electrical conductors that allow current to continue to flow through the positive electrode active material layer 23 and the negative electrode active material layer 33 during charging or discharging of the lithium-ion secondary battery. The positive electrode current collector 22 and the negative electrode current collector 32 may be made of a material such as a metal material, a conductive resin material, or a conductive inorganic material.

[0022] The conductive resin material may be, for example, a resin obtained by adding a conductive filler to a conductive polymer material or a non-conductive polymer material as needed. The positive electrode current collector 22 and the negative electrode current collector 32 may have multiple layers, including one or more layers containing a metal material or a conductive resin material. The surfaces of the positive electrode current collector 22 and the negative electrode current collector 32 may be coated with a known protective layer. The surfaces of the positive electrode current collector 22 and the negative electrode current collector 32 may be metal-plated by a known method such as plating.

[0023] The positive electrode current collector 22 and the negative electrode current collector 32 may have the form of, for example, a foil, sheet, film, wire, rod, mesh, or clad material. When the positive electrode current collector 22 and the negative electrode current collector 32 are metal foils, the positive electrode current collector 22 and the negative electrode current collector 32 may be, for example, aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil. The positive electrode current collector 22 and the negative electrode current collector 32 may be alloy foils of the above metals. When the positive electrode current collector 22 and the negative electrode current collector 32 are metal foils, the thickness of the positive electrode current collector 22 and the negative electrode current collector 32 is, for example, 1 to 100 μm. The positive electrode current collector 22 of this embodiment is aluminum foil. The negative electrode current collector 32 of this embodiment is copper foil. In order to improve the structural stability of the laminate 10a, for example, the thickness of the current collectors 12 of the positive terminal electrode 36 and the negative terminal electrode 37, or at least one of the current collectors 12 of the multiple electrodes 11 consisting of bipolar electrodes, may be 100 μm or more.

[0024] The current collector 12 is not limited to a configuration in which the positive electrode current collector 22 and the negative electrode current collector 32 are integrated, but may be a single sheet-like current collector made of a metal material, a conductive resin material, or a conductive inorganic material. The current collector 12 may also be a single sheet-like current collector formed by plating the surface of the sheet-like current collector to form a coating layer. In these cases, the single current collector 12 is used as the positive electrode current collector 22 and the negative electrode current collector 32.

[0025] <Details of the positive electrode active material layer and the negative electrode active material layer> The positive electrode active material layer 23 includes a positive electrode active material capable of absorbing and releasing lithium ions as a charge carrier. The positive electrode active material may be, for example, a polyanion compound such as olivine-type lithium iron phosphate (LiFePO4), a lithium composite metal oxide having a layered rock salt structure, or a metal oxide having a spinel structure. The positive electrode active material may be any material that can be used as a positive electrode active material for the power storage device 10, such as a lithium ion secondary battery.

[0026] The negative electrode active material layer 33 includes a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions. The negative electrode active material may be any element, alloy, or compound capable of absorbing and releasing charge carriers, such as lithium ions, and is not particularly limited to such a material. For example, the negative electrode active material may be Li, carbon, a metal compound, or an element or compound thereof that can be alloyed with lithium. The carbon may be, for example, natural graphite, artificial graphite, hard carbon (non-graphitizable carbon), or soft carbon (easily graphitizable carbon). The artificial graphite may be, for example, highly oriented graphite or mesocarbon microbeads. The element that can be alloyed with lithium may be, for example, silicon or tin.

[0027] The positive electrode active material layer 23 and the negative electrode active material layer 33 may contain components for increasing electrical conductivity, such as a conductive additive, a binder, an electrolyte (e.g., a polymer matrix, an ion-conductive polymer, or a liquid electrolyte), or an electrolyte supporting salt (lithium salt) for increasing ion conductivity, as needed. The types and blending ratios of these components contained in the positive electrode active material layer 23 and the negative electrode active material layer 33 are not particularly limited.

[0028] The conductive additive may be, for example, acetylene black, carbon black, or graphite. The binder may be, for example, a fluorine-containing resin such as polyvinylidene fluoride, polytetrafluoroethylene, or fluorine rubber; a thermoplastic resin such as polypropylene or polyethylene; an imide resin such as polyimide or polyamideimide; an alkoxysilyl group-containing resin; an acrylic resin such as poly(meth)acrylic acid; styrene-butadiene rubber; carboxymethyl cellulose; an alginate salt such as sodium alginate or ammonium alginate; a water-soluble cellulose ester crosslinked product; or a starch-acrylic acid graft polymer. These binders may be used alone or in combination. The solvent or dispersion medium may be, for example, water or N-methyl-2-pyrrolidone.

[0029] <separator> The electricity storage device 10 includes a plurality of separators 35. Each separator 35 is disposed between a positive electrode active material layer 23 and a negative electrode active material layer 33. The separator 35 separates the positive electrode active material layer 23 from the negative electrode active material layer 33 to prevent a short circuit due to contact between the two electrodes, while allowing charge carriers such as lithium ions to pass through.

[0030] The separator 35 may be, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. The electrolyte impregnated in the separator 35 may be, for example, a liquid electrolyte containing a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent, or a polymer gel electrolyte containing an electrolyte retained in a polymer matrix. In this embodiment, a liquid electrolyte is used as the electrolyte. Examples of the electrolyte salt of the liquid electrolyte include LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2, as well as other known lithium salts. Examples of the nonaqueous solvent include cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers, as well as other known solvents. Two or more of these known solvent materials may be used in combination. The material constituting the separator 35 may be, for example, polypropylene, polyethylene, polyolefin, or polyester. The separator 35 may have a single-layer or multi-layer structure. The multi-layer structure may include, for example, at least one of an adhesive layer and a ceramic layer that is a heat-resistant layer.

[0031] <Positive and negative terminal electrodes> In the stacking direction X, the multiple electrodes 11 are located between a positive terminal electrode 36 and a negative terminal electrode 37. The positive terminal electrode 36 has a current collector 12 and a positive electrode active material layer 23 disposed on a first surface 12a of the current collector 12, and has a configuration similar to that of the electrode 11 except that it does not have a negative electrode active material layer 33. The negative terminal electrode 37 has a current collector 12 and a negative electrode active material layer 33 disposed on a second surface 12b of the current collector 12, and has a configuration similar to that of the electrode 11 except that it does not have a positive electrode active material layer 23. The current collector 12 of the positive terminal electrode 36 is located at a first end of the stack 10a in the stacking direction X. The current collector 12 of the negative terminal electrode 37 is located at a second end of the stack 10a in the stacking direction X.

[0032] The second surface 12b of the current collector 12 included in the positive terminal electrode 36 is the first outer surface 32a of the laminate 10a. The first outer surface 32a is a first end surface in the stacking direction X of the laminate 10a. The first surface 12a of the current collector 12 included in the negative terminal electrode 37 is the second outer surface 22a of the laminate 10a. The second outer surface 22a is a second end surface in the stacking direction X of the laminate 10a. The first outer surface 32a and the second outer surface 22a are flat surfaces extending perpendicular to the stacking direction X.

[0033] <Interior space> Between two current collectors 12 adjacent to each other in the stacking direction X, there is one internal space S for each pair of a positive electrode current collector 22 and a negative electrode current collector 32 adjacent to each other in the stacking direction X. Each internal space S is defined by the positive electrode current collector 22 and the negative electrode current collector 32 adjacent to each other in the stacking direction X and the sealing body 15. A positive electrode active material layer 23, a negative electrode active material layer 33, a separator 35, and a liquid electrolyte (not shown) are arranged in each internal space S. The liquid electrolyte is a so-called electrolytic solution and includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

[0034] <Positive and negative conductive plates> The energy storage device 10 includes a positive electrode current-carrying plate 38 and a negative electrode current-carrying plate 39. The positive electrode current-carrying plate 38 and the negative electrode current-carrying plate 39 are made of a material with excellent conductivity. The material making up the positive electrode current-carrying plate 38 and the negative electrode current-carrying plate 39 may be, for example, aluminum, copper, stainless steel, or other metallic material. The stack 10a is disposed between the positive electrode current-carrying plate 38 and the negative electrode current-carrying plate 39 in the stacking direction X.

[0035] The positive electrode current-carrying plate 38 is electrically connected to the first outer surface 32a of the laminate 10a. The negative electrode current-carrying plate 39 is electrically connected to the second outer surface 22a of the laminate 10a. Terminals (not shown) are provided on each of the positive electrode current-carrying plate 38 and the negative electrode current-carrying plate 39. The energy storage device 10 is charged and discharged via the terminals provided on the positive electrode current-carrying plate 38 and the negative electrode current-carrying plate 39.

[0036] <Sealing body> The sealing body 15 is disposed so as to surround the periphery of the positive electrode active material layers 23 and negative electrode active material layers 33 of the multiple electrodes 11, the positive electrode terminal electrode 36, and the negative electrode terminal electrode 37, as viewed from the stacking direction X. Hereinafter, the electrodes 11, the positive electrode terminal electrode 36, and the negative electrode terminal electrode 37 may be simply referred to as electrodes 11a. The sealing body 15 seals the gaps between the current collectors 12 adjacent to each other in the stacking direction X.

[0037] As shown in FIGS. 2 and 3, the sealing body 15 has a plurality of seal portions 40 welded to the current collectors 12 of the plurality of electrodes 11a. All of the seal portions 40 are made of resin. Each seal portion 40 has two first seal portions 41 and a second seal portion 42. The first seal portion 41 is a portion disposed between the first surface 12a of the current collector 12 of one of the electrodes 11a adjacent to each other in the stacking direction X and the second surface 12b of the current collector 12 of the other electrode 11a. In other words, the first seal portion 41 is disposed inside the outer edge 12e of the current collector 12 when viewed from the stacking direction X.

[0038] The two first seal portions 41 are arranged on both sides (first surface 12a and second surface 12b) of the current collector 12. The first seal portions 41 are arranged continuously along the four sides 12f. In other words, the seal portion 40 has two first seal portions 41 arranged on both sides of the current collector 12 along the sides 12f.

[0039] Each seal portion 40 has a welded portion 41a welded to the current collector 12. The welded portion 41a is located at the boundary between the first surface 12a and the second surface 12b of the first seal portion 41. The first seal portion 41 is welded to each of the positive electrode uncoated portion 12c and the negative electrode uncoated portion 12d via the welded portion 41a. As a result, the seal portion 40 is welded to the first surface 12a and the second surface 12b of the current collector 12 of the corresponding electrode 11a via the welded portion 41a.

[0040] The first sealing portion 41 located on the positive electrode uncoated portion 12c is arranged so as to surround the periphery of the positive electrode active material layer 23. The first sealing portion 41 located on the negative electrode uncoated portion 12d is arranged so as to surround the periphery of the negative electrode active material layer 33. The first sealing portion 41 has a rectangular frame shape. That is, the rectangular frame-shaped first sealing portion 41 is a member of a predetermined width that continuously surrounds the periphery of the positive electrode active material or the negative electrode active material in a plan view.

[0041] The second seal portion 42 is a portion that extends from the first seal portion 41 outward beyond the outer edge 12e of the current collector 12. More specifically, the second seal portion 42 is a portion that is located outside the outer edge 12e of the current collector 12 when viewed from the stacking direction X. The second seal portion 42 is arranged so as to surround the periphery of the current collector 12 when viewed from the stacking direction X. The second seal portion 42 has a rectangular frame shape. The second seal portion 42 covers the end face that connects the first surface 12a and the second surface 12b of the current collector 12. The second seal portion 42 connects the outer periphery of the first seal portion 41 located on the positive electrode uncoated portion 12c to the outer periphery of the first seal portion 41 located on the negative electrode uncoated portion 12d.

[0042] As shown in FIG. 2, the sealing body 15 has a plurality of spacer portions 50. Each spacer portion 50 is adjacent to a first seal portion 41 and a second seal portion 42 in the stacking direction X. Each spacer portion 50 is located between the seal portions 40 provided on two electrodes 11 adjacent to each other in the stacking direction X. The spacer portions 50 are arranged so as to surround the peripheries of the positive electrode active material layer 23 and the negative electrode active material layer 33. The spacer portions 50 have a rectangular frame shape. The spacer portions 50 are made of resin.

[0043] The spacer portion 50 is not welded to the first seal portion 41. Therefore, the spacer portion 50 is not welded to the current collector 12. Both surfaces of the spacer portion 50 in the stacking direction X may be in contact with the first seal portion 41 or may be separated from the first seal portion 41.

[0044] The first seal portion 41 and the spacer portion 50 are positioned between adjacent current collectors 12 in the stacking direction X. As a result, the first seal portion 41 and the spacer portion 50 maintain a gap between the positive electrode current collector 22 of one of the two current collectors 12 adjacent to each other in the stacking direction X and the negative electrode current collector 32 of the other current collector 12, thereby insulating them from each other. In this way, the seal portion 40 and the spacer portion 50 prevent a short circuit between the positive electrode current collector 22 and the negative electrode current collector 32.

[0045] The spacer portion 50 is welded to at least a portion of the second seal portion 42 adjacent to it in the stacking direction X. This integrates the seal portion 40 and the spacer portion 50. A region of a predetermined width from the outer edge of the spacer portion 50 is welded to a region of a predetermined width from the outer edge of the second seal portion 42.

[0046] The sealing body 15 has a sealing portion 16, which includes a spacer portion 50 and a second seal portion 42 that are welded to each other. In the sealing portion 16, the spacer portion 50 and the second seal portion 42 are compatible with each other. The sealing portion 16 has a cylindrical shape that extends in the stacking direction X. The sealing portion 16 surrounds the periphery of the multiple current collectors 12 from the outside of the stack 10a.

[0047] The sealing portion 16 seals the internal space S between the current collectors 12 adjacent to each other in the stacking direction X. The sealing portion 16 can prevent moisture from entering the internal space S from the outside of the electricity storage device 10. The sealing portion 16 can prevent the liquid electrolyte accommodated in the internal space S from leaking out of the electricity storage device 10.

[0048] <Electrode manufacturing method> Next, a method for manufacturing the electrode 11a will be described. Note that, although the following description will be given using the electrode 11, the positive terminal electrode 36 and the negative terminal electrode 37 are also manufactured in the same manner.

[0049] 4 and 5 , an electrode 11 is manufactured by welding a sealing member 140 to a current collector 12 using a jig 60. At this time, a positive electrode active material layer 23 is disposed on a first surface 12a of the current collector 12, and a negative electrode active material layer 33 is disposed on a second surface 12b of the current collector 12. That is, the sealing member 140 is welded to the current collector 12 having active material layers disposed on both surfaces. The manufactured electrode 11 has the current collector 12, an active material layer provided on the surface of the current collector 12, and the sealing member 140 welded to the surface of the current collector 12.

[0050] <Placement process> Prior to welding the sealing member 140 to the current collector 12, the sealing member 140 is placed on the current collector 12 (placement step). The sealing member 140 is made of resin. In the placement step, separate sealing members 140 (first sealing member 141 and second sealing member 142) are placed on both sides of the current collector 12, i.e., on the first surface 12a and the second surface 12b. After the sealing members 140 are placed so as to extend along the side 12f of the current collector 12, the sealing members 140 may be temporarily fixed (temporarily welded) to the current collector 12 by spot welding using ultrasonic waves or heat.

[0051] 5, in the disposing step, the sealing member 140 disposed on the first surface 12a is the first sealing member 141. The first sealing member 141 is spaced apart from the positive electrode active material layer 23. In the disposing step, the sealing member 140 disposed on the second surface 12b is the second sealing member 142. The second sealing member 142 is spaced apart from the negative electrode active material layer 33. The first sealing member 141 and the second sealing member 142 sandwich the current collector 12 from both sides in the thickness direction of the current collector 12.

[0052] Each seal member 140 has a protruding portion 140b protruding from the outer edge 12e of the current collector 12. The protruding portion 140b is a portion that does not overlap the current collector 12 when viewed from the direction in which the current collector 12 and the seal members 140 are stacked. The protruding portion 140b of the first seal member 141 and the protruding portion 140b of the second seal member 142 are separated from each other. The portions of the seal member 140 that are arranged on both sides of the current collector 12 are referred to as main body portions 140a. The main body portions 140a are portions that overlap the current collector 12 when viewed from the direction in which the current collector 12 and the seal members 140 are stacked. Each of the first seal member 141 and the second seal member 142 has a main body portion 140a and a protruding portion 140b. In the first seal member 141 and the second seal member 142, the protruding portion 140b extends from the main body portion 140a. That is, when viewed from the direction in which the current collector 12 and the sealing member 140 are stacked, each sealing member 140 is arranged on the current collector 12 so that it has both a portion that overlaps the current collector 12 and a portion that does not overlap the current collector 12.

[0053] As shown in FIG. 4, in the arrangement step, two sealing members 140 are arranged on both sides of the current collector 12 along the side 12f of the current collector 12. Each sealing member 140 is strip-shaped, extends longitudinally along the side 12f on which it is arranged, and the direction intersecting the side 12f is the short direction (width direction). More specifically, the multiple sealing members 140 are arranged along the two long sides 12h and the two short sides 12g of the current collector 12. In the arrangement step, separate sealing members 140 are arranged on the two sides 12f. The sealing members 140 arranged along each short side 12g are also referred to as short side sealing members 144. The sealing members 140 arranged along each long side 12h are also referred to as long side sealing members 143. Each of the long side sealing members 143 and the short side sealing members 144 includes a first sealing member 141 and a second sealing member 142. The direction in which the long sides 12h extend is also referred to as the first direction Y. The direction in which the short sides 12g extend is also referred to as the second direction Z. The first direction Y is the direction in which two of the four sides 12f extend, and the second direction Z is the direction in which the remaining two of the four sides 12f extend.

[0054] When viewed from the direction in which the current collector 12 and the sealing member 140 are stacked, both end portions 143a of the long side sealing member 143 in the first direction Y protrude further outside the current collector 12 than the outer edges 12e of both ends of the current collector 12 in the first direction Y. Each of the long side sealing members 143 overlaps one long side 12h of the current collector 12 and the ends of two short sides 12g in the second direction Z.

[0055] The short side sealing member 144 extends between the two long side sealing members 143 in the second direction Z. The short side sealing member 144 may overlap the long side sealing member 143, or may be disposed between the two long side sealing members 143 so as not to overlap with the long side sealing member 143. In this embodiment, each of the short side sealing members 144 overlaps a portion of both end portions of one short side 12g of the current collector 12 that overlaps with the long side sealing member 143. In other words, the short side sealing member 144 and the long side sealing member 143 overlap each other.

[0056] The long-side sealing member 143 and the short-side sealing member 144 are arranged to form a frame on each of the first surface 12a and the second surface 12b. The periphery of the positive electrode active material layer 23 is surrounded by the first sealing member 141 of the long-side sealing member 143 and the short-side sealing member 144. The periphery of the negative electrode active material layer 33 is surrounded by the second sealing member 142 of the long-side sealing member 143 and the short-side sealing member 144.

[0057] <Jig> 5, the jig 60 used to weld the sealing member 140 to the current collector 12 is, for example, an impulse sealer having an electric heating wire. The impulse sealer has a pair of jigs 60 arranged to sandwich the current collector 12 in the thickness direction (the direction perpendicular to the first direction Y and the second direction Z).

[0058] The jig 60 includes a heater section 61. The heater section 61 is, for example, a metal plate with a built-in heating wire (not shown). By adjusting the amount of current flowing through the heating wire, the heater section 61 can be switched between heating and non-heating. The heater section 61 is deformable.

[0059] The jig 60 includes a rubber portion 62 and a base portion 63. The rubber portion 62 is made of, for example, silicone rubber. The rubber portion 62 is positioned so as to overlap the heater portion 61 in the thickness direction of the current collector 12. The heater portion 61 is fixed to the rubber portion 62. The rubber portion 62 is compressively deformable.

[0060] The base portion 63 is made of, for example, metal. The rubber portion 62 is located between the base portion 63 and the heater portion 61. As a result, the rubber portion 62 insulates the base portion 63 from the heater portion 61. The rubber portion 62 suppresses heat transfer from the heater portion 61 to the base portion 63. The rubber portion 62 is fixed to the base portion 63. As a result, the heater portion 61, the rubber portion 62, and the base portion 63 are integrated with one another. The base portion 63 is displaceable relative to the welding target. For example, the position of the base portion 63 relative to the welding target, that is, the sealing member and the current collecting foil, is changed by an operator operating an operating device (not shown). When the position of the base portion 63 relative to the welding target is changed, the heater portion 61 and the rubber portion 62 integrated with the base portion 63 are displaced together with the base portion 63.

[0061] The heater part 61 and the rubber part 62 are rectangular flat plates. The longitudinal direction of the heater part 61 and the rubber part 62 is also referred to as the longitudinal direction of the jig 60. The lateral direction of the heater part 61 and the rubber part 62 is also referred to as the lateral direction of the jig 60.

[0062] The dimension of the rubber portion 62 in the short direction of the jig 60 is larger than the dimension of the heater portion 61 in the short direction of the jig 60. The rubber portion 62 has a rubber protruding portion 62a that protrudes outward beyond the end portion 61a of the heater portion 61 in the short direction of the jig 60 when viewed from the stacking direction in which the heater portion 61 and the rubber portion 62 overlap.

[0063] As shown in FIG. 6 , the jig 60 has a jig electrode 64. The jig electrode 64 is located outside both ends of the heater portion 61, the rubber portion 62, and the base portion 63 in the longitudinal direction of the jig 60. The jig electrode 64 has a corner 64a. The corner 64a is curved. The contact surface of the heater portion 61 with the seal member 140 and the surface of the jig electrode 64 perpendicular to the longitudinal direction of the jig 60 are smoothly connected via the corner 64a. The corner 64a is adjacent to the heater portion 61 in the longitudinal direction of the jig 60. In other words, the corner 64a can be said to be located around the heater portion 61. The jig 60 can also be said to have the corner 64a.

[0064] <Welding process> As shown in FIG. 4 , after the arrangement step, the seal member 140 is welded to the current collector 12 using a jig 60 (welding step). In the welding step, the jig 60 is brought into surface contact with a target portion 145, which is a part of the seal member 140, and the target portion 145 is heated by the jig 60 while being pressed against the current collector 12. Specifically, the target portion 145 of the seal member 140 is a part between both ends of the seal member 140 in the direction in which the side 12f extends. The dimension of the target portion 145 in the direction in which the side 12f extends is smaller than the dimension of the side 12f of the current collector 12. The heater unit 61 is brought into surface contact with this target portion 145, and the heater unit 61 heats the target portion 145 while pressing it against the current collector 12. As a result, in the welding step, the target portion 145 is welded to the surface of the current collector 12. The size of the target portion 145 is the same as the size of the area where the heater portion 61 comes into contact with the seal member 140. In this welding step, a sheet material 65 may be placed between the heating surface of the heater portion 61 and the current collector 12 and seal member 140, and the heater portion 61 may be pressed against the current collector 12 and seal member 140 via the sheet material 65 to heat the seal member 140. This makes it possible to prevent the molten seal member 140 from adhering to the heating surface of the heater portion 61.

[0065] The sheet material 65 may be, for example, a base sheet coated with a heat-resistant, non-adhesive, and slippery fluororesin on its surface, or may be, for example, a heat-resistant base sheet impregnated with a fluorine-based compound such as polytetrafluoroethylene.

[0066] 5, the target portion 145 includes the main body portion 140a and a part of the protruding portion 140b. Therefore, in the welding step, the main body portion 140a is welded to the surface of the current collector 12, and the parts of the protruding portions 140b of the first seal member 141 and the second seal member 142 are welded to each other.

[0067] 4, in the welding step, the sealing member 140 is welded to the current collector 12 while displacing the relative position of the electrode 11 with respect to the jig 60 in the direction in which the side 12f of the current collector 12 extends. Specifically, the long side sealing member 143 is welded to the current collector 12 while displacing the relative position of the electrode 11 with respect to the jig 60 in the first direction Y. The short side sealing member 144 is welded to the current collector 12 while displacing the relative position of the electrode 11 with respect to the jig 60 in the second direction Z. In this embodiment, the relative position of the electrode 11 with respect to the jig 60 is changed by displacing the electrode 11 in the first direction Y using a moving device (transfer device) such as a belt conveyor or a robot hand.

[0068] The dimension of the target portion 145 in the direction in which the side 12f extends is also referred to as the dimension L of the target portion 145. In the welding process performed using the long side seal member 143, the dimension L of the target portion 145 is the dimension of the target portion 145 in the first direction Y. In the welding process performed using the short side seal member 144, the dimension L of the target portion 145 is the dimension of the target portion 145 in the second direction Z. When the welding process is performed on the long side seal member 143, the dimension L of the target portion 145 is smaller than the long side 12h. Although not shown in FIG. 4, when the welding process is performed on the short side seal member 144, the dimension L of the target portion 145 is smaller than the short side 12g. The upper limit of the dimension L may be equal to or smaller than half the length of the long side 12h (1.5 meters). Furthermore, the lower limit of the dimension L may be equal to or larger than one-third the length of the long side 12h to reduce the number of welding processes. In this embodiment, whether the welding process is performed on the long side seal members 143 or on the short side seal members 144, the dimension L of the target portion 145 is 720 mm or less.

[0069] The region where the heater portion 61 is located when the long side seal member 143 is welded to the current collector 12 is referred to as the long side region R1. The region where the heater portion 61 is located when the short side seal member 144 is welded to the current collector 12 is referred to as the short side region R2. The long side region R1 and the short side region R2 are illustrated by dot hatching in FIG. 4. The overlapping portions of the long side seal member 143 and the short side seal member 144 are included in the long side region R1 or the short side region R2. As a result, the overlapping portions of the long side seal member 143 and the short side seal member 144 are welded in the welding process. The long side region R1 and the short side region R2 overlap with each other at both end portions 143a of the long side seal member 143 in the first direction Y and both end portions 144a of the short side seal member 144 in the second direction Z.

[0070] The welding process is performed multiple times between both end portions of the sealing member 140 in the direction in which the side 12f extends. In this embodiment, when welding the long side sealing member 143 to the current collector 12, the welding process is performed three times between both end portions 143a of the long side sealing member 143 in the first direction Y. When welding the short side sealing member 144 to the current collector 12, the welding process is performed two times between both end portions 144a of the short side sealing member 144 in the second direction Z.

[0071] In the second and subsequent welding steps, the portion of the sealing member 140 that is at least partially displaced in the direction in which the side 12f extends from the target portion 145 in the previous welding step is defined as the target portion 145. In the present embodiment, in the second and subsequent welding steps that are performed when welding the long side sealing member 143 to the current collector 12, the portion of the sealing member 140 that is partially displaced in the first direction Y from the target portion 145 in the previous welding step is defined as the target portion 145. In the second and subsequent welding steps, a portion of the target portion 145 in the direction in which the side 12f extends overlaps with the target portion 145 in the previous welding step.

[0072] Of the target portions 145 in the welding process performed with the long-side seal member 143, the target portion 145 in the first welding process is referred to as a first target portion 145a, the target portion 145 in the second welding process is referred to as a second target portion 145b, and the target portion 145 in the third welding process is referred to as a third target portion 145c. The second target portion 145b is partially misaligned from the first target portion 145a in the first direction Y. The third target portion 145c is partially misaligned from the second target portion 145b in the first direction Y. A first end portion of the second target portion 145b in the first direction Y overlaps with a portion of the first target portion 145a, and a second end portion of the second target portion 145b in the first direction Y overlaps with a portion of the third target portion 145c.

[0073] Of the target portions 145 in the welding process performed on the short side seal member 144, the target portion 145 in the first welding process is referred to as the first target portion 145a, and the target portion 145 in the second welding process is referred to as the second target portion 145b. The first target portion 145a and the second target portion 145b in the welding process performed on the short side seal member 144 are not shown in FIG. 4. In the welding process on the short side seal member 144, as in the welding process on the long side seal member 143, a portion of the target portion 145 overlaps with the target portion 145 in the previous welding process. In the welding process on the short side seal member 144, a portion of the end portions in the second direction Z of the first target portion 145a and the second target portion 145b overlap with each other.

[0074] By carrying out the welding process for the long side seal member 143 and the welding process for the short side seal member 144, an electrode 11 is manufactured in which the seal member 140 is integrated with the current collector 12. By repeatedly welding the seal member 140 to the current collector 12 using the jig 60 in this manner, electrodes 11 in which the seal member 140 is integrated with the current collector 12 are successively manufactured.

[0075] <Details of the welding process for long side seal parts> Next, the welding process for the long side seal member 143 will be described in detail. Note that a detailed explanation of the welding process for the short side seal member 144 will be omitted. In the following explanation of the welding process for the long side seal member 143, the "first direction Y" will be replaced with the "second direction Z" and welding to the third target portion 145c will be omitted, thereby explaining the welding process for the short side seal member 144.

[0076] As shown in FIG. 6 , in the welding process for the first target portion 145a, the electrode 11 is moved relative to the jig 60 to a position where the heater portion 61 faces the first target portion 145a in the thickness direction of the current collector 12. At this time, the electrode 11 is arranged so that the first direction Y is along the longitudinal direction of the jig 60. The pair of jigs 60 are arranged so as to sandwich the current collector 12 in the thickness direction. The welding process is performed on the sealing members 140 arranged on both sides of the current collector 12. As the base portion 63 is displaced in the thickness direction of the current collector 12 from the position where the heater portion 61 faces the first target portion 145a, the jig 60 is displaced so as to approach the first target portion 145a.

[0077] When the heater portion 61 moves to a position where it contacts the first target portion 145a of the seal member 140, the displacement of the base portion 63 in the thickness direction of the current collector 12 stops, and the displacement of the jig 60 also stops. At this time, the heater portion 61 is pressed against the main body portions 140a of the first seal member 141 and the second seal member 142. As the heater portion 61 presses against the seal member 140, the rubber portion 62 may be compressively deformed. In this embodiment, the pair of jigs 60 are displaced toward each other to sandwich the seal member 140 and the current collector 12 between them, and in this state, the heater portion 61 of each jig 60 is pressed against the seal member 140 and the exposed portion, respectively. Therefore, one jig 60 of the pair of jigs 60 is also used as a support member that receives the pressing force of the other jig 60.

[0078] The heater section 61 is heated while being pressed against the first target portion 145a. Heating by the heater section 61 may start before or after the heater section 61 is pressed against the seal member 140. The heater section 61 heats the first target portion 145a while being in surface contact with the first target portion 145a. When the heater section 61 heats the first target portion 145a, the corner portion 64a of the jig 60 also comes into contact with the seal member 140.

[0079] With the heater part 61 still pressed against the first target part 145a, heating by the heater part 61 is stopped. A predetermined time passes with the heater part 61 still pressed against the first target part 145a, and as the seal member 140 cools, the seal member 140 is welded to the current collector 12. In the welding process, a welded part 41a is formed at the boundary position of the first target part 145a between the seal member 140 and the current collector 12, where the first target part 145a is welded to the surface of the current collector 12.

[0080] When the weld portion 41a is formed in the first target portion 145a, the welding process for the first target portion 145a using the jig 60 is completed. The welding process for the first target portion 145a is completed by displacing the jig 60 in the thickness direction of the current collector 12 so that the heater portion 61 moves away from the seal member 140.

[0081] 7, after the welding process for the first target portion 145a is performed, the welding process for the second target portion 145b is performed. During the welding process for the second target portion 145b, the electrode 11 is moved in the first direction Y relative to the jig 60 to a position where the heater portion 61 faces the second target portion 145b. As the base portion 63 is displaced in the thickness direction of the current collector 12 from the position where the heater portion 61 faces the second target portion 145b, the jig 60 is displaced so as to approach the second target portion 145b.

[0082] When the heater unit 61 moves to a position where it contacts the second target portion 145b of the seal member 140, it welds the second target portion 145b to the current collector 12, similar to the welding of the first target portion 145a. At this time, the end of the second target portion 145b in the first direction Y overlaps with a portion of the first target portion 145a. That is, the heater unit 61 presses the second target portion 145b and a portion of the first target portion 145a. Therefore, the end of the second target portion 145b in the first direction Y overlaps with a portion of the weld portion 41a formed on the first target portion 145a. In the welding process, a weld portion 41a is formed at the boundary position of the second target portion 145b between the seal member 140 and the current collector 12, where the second target portion 145b is welded to the surface of the current collector 12. When the welded portion 41a is formed on the second target portion 145b, the welding process for the second target portion 145b using the jig 60 is completed.

[0083] 8, after the welding process for the second target portion 145b is performed, the welding process for the third target portion 145c is performed. During the welding process for the third target portion 145c, the electrode 11 is moved in the first direction Y relative to the jig 60 to a position where the heater portion 61 faces the third target portion 145c. As the base portion 63 is displaced in the thickness direction of the current collector 12 from the position where the heater portion 61 faces the third target portion 145c, the jig 60 is displaced so as to approach the third target portion 145c.

[0084] When the heater unit 61 moves to a position where it contacts the third target portion 145c of the seal member 140, it welds the third target portion 145c to the current collector 12, similar to the welding of the first target portion 145a and the second target portion 145b. At this time, the end of the third target portion 145c in the first direction Y overlaps with a portion of the second target portion 145b. That is, the heater unit 61 presses the third target portion 145c and a portion of the second target portion 145b. Therefore, the end of the third target portion 145c in the first direction Y overlaps with a portion of the weld portion 41a formed on the second target portion 145b. In the welding process, a weld portion 41a is formed at the boundary position of the third target portion 145c between the seal member 140 and the current collector 12, where the third target portion 145c is welded to the surface of the current collector 12. When the welded portion 41a is formed on the third target portion 145c, the welding process for the third target portion 145c using the jig 60 is completed.

[0085] <Electrodes after welding process> 5 and 9, when the sealing member 140 is welded to the current collector 12 by performing the welding process for the long side sealing member 143 and the welding process for the short side sealing member 144, an electrode 11a integrated with the sealing member 140 is obtained. Note that the main body portion 140a of the sealing member 140 welded to the surface of the current collector 12 after the welding process corresponds to the first sealing portion 41 of the sealing portion 40. The welded portions of the protruding portions 140b of the first sealing member 141 and the second sealing member 142 after the welding process correspond to the second sealing portion 42 of the sealing portion 40.

[0086] <Method of manufacturing an electricity storage device> 9, the electrode 11a integrated with the sealing member 140, the separator 35, and the spacer portion 50 are stacked in order in the stacking direction X. Of two electrodes 11a adjacent to each other in the stacking direction X, the spacer portion 50 is interposed between the sealing member 140 integrated with one electrode 11a and the sealing member 140 integrated with the other electrode 11a.

[0087] Next, the sealing member 140 and the spacer portion 50 are welded together. The sealing member 140 and the spacer portion 50 may be welded together without contact using, for example, a welding jig 70. The welding jig 70 is, for example, an infrared heater. A portion of the protruding portion 140b of the sealing member 140 and a portion of the spacer portion 50 are heated and melted by infrared rays irradiated from the welding jig 70, thereby welding and integrating the portion of the protruding portion 140b and the portion of the spacer portion 50. Here, a region of a predetermined width from the edge of the protruding portion 140b of the sealing member 140 is welded to a region of a predetermined width from the edge of the spacer portion 50. In other words, the outer end surfaces of a laminated resin portion formed by stacking multiple sealing members 140 and multiple spacer portions 50 are welded together to form the sealing portion 16.

[0088] As a result, as shown in FIG. 2, the seal portion 40 is formed, and the second seal portion 42 and the spacer portion 50, which are integrated with each other, form the sealing portion 16. <Experimental results regarding the relationship between the dimensions of the target part and the occurrence of deformation in the current collector> An experiment was conducted to examine the relationship between the dimensions of the target portion 145 to which the seal member 140 is welded and the occurrence of deformation in the current collector 12. The positive electrode current collector 22 of the current collector 12 used in this experiment was aluminum foil, and the negative electrode current collector 32 was copper foil. In the current collector 12 used in the experiment, the positive electrode current collector 22 and the negative electrode current collector 32 were bonded to each other with a conductive adhesive made of a polyolefin adhesive mixed with carbon as a conductive additive. The current collector 12 had a thickness of 65 μm. The seal member 140 used in the experiment was made of acid-modified low-density polyethylene and had a thickness of 120 μm.

[0089] In the experiment, sealing member 140 was welded to both sides of current collector 12 using an impulse sealer under conditions of a welding temperature of 195°C and a surface pressure of 0.7 MPa or more during welding. In this experiment, when target portion 145 to which sealing member 140 was welded had a dimension of 720 mm or less, current collector 12 did not deform due to welding of sealing member 140 to current collector 12.

[0090] [Effect] Next, the operation of this embodiment will be described. When welding the seal member 140 to the current collector 12, the jig 60 heats the seal member 140 while making surface contact with the seal member 140 and pressing the target portion 145 against the current collector 12. The seal member 140 thermally expands upon receiving heat from the jig 60. At this time, the larger the dimensions of the target portion 145 that is the target of heating by the jig 60, the greater the amount of thermal expansion of the seal member 140. After heating of the seal member 140 by the jig 60 is completed, the seal member 140 thermally contracts as it cools. The greater the amount of thermal expansion of the seal member 140, the greater the amount of thermal contraction of the seal member 140.

[0091] If the entire area between both end portions 143a of the sealing member 140 in the direction in which the long side 12h extends is defined as the target portion 145, the dimension of the target portion 145 in the direction in which the side 12f extends will be the same as the dimension of the long side 12h. If the entire area between both end portions 144a of the sealing member 140 in the direction in which the short side 12g extends is defined as the target portion 145, the dimension of the target portion 145 in the direction in which the side 12f extends will be the same as the dimension of the short side 12g. In contrast, the dimension of the target portion 145 in the direction in which the side 12f extends in this embodiment is smaller than that of the side 12f. Therefore, compared to the case in which the dimension of the target portion 145 in the direction in which the side 12f extends is the same as the dimension of the side 12f as described above, the smaller dimension of the target portion 145 reduces the amount of thermal expansion of the sealing member 140.

[0092] [effect] According to the above embodiment, the following effects can be obtained. (1) A jig 60 is placed in surface contact with a target portion 145 of the seal member 140, the target portion 145 having a dimension in the direction in which the side 12f extends that is smaller than the side 12f, and the target portion 145 is pressed against the current collector 12 and heated by the jig 60. This performs a welding process to form a welded portion 41a in which the target portion 145 is welded to the surface of the current collector 12. Therefore, compared to when the dimension of the target portion 145 in the direction in which the side 12f extends is the same as the dimension of the side 12f, the smaller dimension of the target portion 145 reduces the amount of thermal expansion of the seal member 140. The smaller amount of thermal expansion of the seal member 140 reduces the amount of thermal contraction of the seal member 140. This reduces the contraction force transmitted from the seal member 140 to the current collector 12 due to the thermal contraction of the seal member 140. This reduces deformation of the current collector 12 that occurs when the seal member 140 is welded to the current collector 12.

[0093] (2) In the arrangement step, the sealing members 140 are arranged on both sides of the current collector 12. The welding step is performed on the sealing members 140 arranged on both sides of the current collector 12. Therefore, deformation of the current collector 12 that occurs when the sealing members 140 are welded to both sides of the current collector 12 can be reduced.

[0094] (3) In the second and subsequent welding steps, a portion of the target portion 145 in the direction in which the side 12f extends overlaps with the target portion 145 from the previous welding step. Therefore, even if the relative position of the target portion 145 in the direction in which the side 12f extends with respect to the jig 60 deviates from its original position during the welding step, the portion of the target portion 145 that overlaps with the target portion 145 from the previous welding step in the direction in which the side 12f extends only increases or decreases. This makes it less likely that a portion of the multiple target portions 145 will not be welded to the current collector 12. Therefore, poor welding of the sealing member 140 to the current collector 12 can be reduced.

[0095] (4) The jig 60 has a corner 64a that contacts the sealing member 140 when the heater 61 heats the target portion 145. The corner 64a is curved. Therefore, when the corner 64a contacts the sealing member 140, the sealing member 140 is pressed by the corner 64a, which reduces localized swelling of the sealing member 140. If the sealing member 140 locally bulges, the bulge may increase the dimensional tolerance of the energy storage device 10 in the stacking direction X after the sealing members 140 are stacked. According to this embodiment, such an increase in tolerance can be suppressed. Furthermore, when the spacer portion 50 and the sealing member 140 are stacked, the bulge of the sealing member 140 may cause a gap to form between the spacer portion 50 and the sealing member 140. In this case, a gap that forms between the spacer portion 50 and the sealing member 140 during the formation of the sealing portion 16 may result in poor welding between the spacer portion 50 and the sealing member 140. According to this embodiment, the occurrence of such poor welding can be suppressed.

[0096] (5) The dimension of the target portion 145 in the direction in which the side 12f extends is 720 mm or less. Therefore, deformation of the current collector 12 that occurs when the seal member 140 is welded to the current collector 12 can be further reduced.

[0097] (6) If the current collector 12 on which the sealing member 140 is disposed is transported between rollers and the rollers sequentially weld the sealing member 140 to the current collector 12, the welding is performed by line contact of the rollers, making it difficult for air to be pushed out of the welded portion of the sealing member 140. This may result in voids being generated in the seal portion 40. If voids are generated in this manner, adjacent internal spaces S in the stacking direction X of the energy storage device 10 may be connected to each other through the voids in the seal portion 40, resulting in a risk of a short circuit. According to the above embodiment, the welding process is performed by heating the target portion 145 with the jig 60 while bringing the jig 60 into surface contact with the target portion 145. This makes it easy for air to be pushed out of the welded portion of the sealing member 140, making it difficult for voids to be generated in the seal portion 40. This may prevent the above-mentioned short circuit caused by the generation of voids.

[0098] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0099] The welding process may be performed two times or four or more times between both end portions 143a of the seal member 140 in the first direction Y. The welding process may be performed three or more times between both end portions 144a of the seal member 140 in the second direction Z. The welding process may be performed a different number of times between both end portions 143a of the seal member 140 in the first direction Y and between both end portions 144a of the seal member 140 in the second direction Z, or the welding process may be performed the same number of times.

[0100] Of the multiple welding processes performed between both end portions 143a of the sealing member 140 in the first direction Y, the dimensions of the target portion 145 in the first direction Y may be different in all or some of the welding processes. Of the multiple welding processes performed between both end portions 144a of the sealing member 140 in the second direction Z, the dimensions of the target portion 145 in the second direction Z may be different in all or some of the welding processes.

[0101] Of the multiple welding steps performed between both end portions 143a of the seal member 140 in the first direction Y, the dimension of the target portion 145 in the first direction Y may be larger than 720 mm in all or some of the welding steps. Of the multiple welding steps performed between both end portions 144a of the seal member 140 in the second direction Z, the dimension of the target portion 145 in the second direction Z may be larger than 720 mm in all or some of the welding steps. Even in this case, deformation of the current collector 12 that occurs when the seal member 140 is welded to the current collector 12 can be reduced compared to when the entire seal member 140 is used as the target portion 145 and manufactured in a single welding step.

[0102] The corner 64a does not have to be a part of the jig electrode 64. For example, the corner 64a may be a part of the heater portion 61. In this case, the corner 64a is also located around the heater portion 61. The corners 64a do not have to be curved.

[0103] During one or more welding processes among the second and subsequent welding processes performed between both end portions 143a of the sealing member 140 in the first direction Y, the target portion 145 may not overlap with the target portion 145 in the previous welding process. During one or more welding processes among the second and subsequent welding processes performed between both end portions 144a of the sealing member 140 in the second direction Z, the target portion 145 may not overlap with the target portion 145 in the previous welding process.

[0104] Of the welding steps performed between both ends of the sealing member 140 in the extending direction of the side 12f, the target portion 145 in the first welding step does not have to include both ends of the sealing member 140 in the extending direction of the side 12f. In this case, the target portion 145 in the second and subsequent welding steps includes both ends of the sealing member 140 in the extending direction of the side 12f.

[0105] The welding step performed on the sealing member 140 arranged on the first surface 12a of the current collector 12 and the welding step performed on the sealing member 140 arranged on the second surface 12b may be performed at different times. In this case, the sealing member 140 may be arranged on one surface of the current collector 12 in the arrangement step, and then the welding step may be performed on the arranged sealing member 140. Alternatively, the arrangement step and the welding step may be performed on only one surface of the current collector 12, so that the sealing member 140 is welded to only one surface of the current collector 12.

[0106] The dimension of the short side 12g is not limited to, for example, 1.2 meters. The dimension of the long side 12h is not limited to 1.5 meters. For example, the dimension of the short side 12g may be less than 1 meter. In short, it is sufficient that at least one of the sides 12f of the current collector 12 exceeds 1 meter. Note that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, when the number of options is two, the expression "at least one" used in this specification means "only one option" or "both of two options." As another example, when the number of options is three or more, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options."

[0107] The shape of the current collector 12 in plan view is not limited to a rectangular shape. In other words, the current collector 12 may have a polygonal shape in plan view having a plurality of sides 12f, some of which may be longer than one meter.

[0108] The energy storage device 10 may include a restraining member that restrains the stack 10a. The restraining member applies a restraining load in the stacking direction X to a region where the positive electrode active material layer 23 and the negative electrode active material layer 33 overlap when the stack 10a is viewed from the stacking direction X. The restraining member may include, for example, restraining plates disposed on both ends of the stack 10a in the stacking direction X, and fastening members made of bolts and nuts that fasten the restraining plates together. In the case of this restraining member, the fastening members bias the restraining plates in directions that bring them closer to each other, thereby applying a restraining load in the stacking direction X to the stack 10a.

[0109] The heater unit 61 may be a device separate from the jig 60. In this case, the jig 60 does not need to include the heater unit 61. The heater unit 61 may be a non-contact heating device that heats the target portion 145 without coming into contact with the target portion 145, such as an infrared heater. Then, heating of the target portion 145 by a heating device (heater unit 61) separate from the jig 60 may start simultaneously with pressing the target portion 145 with the jig 60, or before or after the pressing.

[0110] In the welding process, the jig 60 may sequentially press only the target portion 145, or may press a wider area so as to include at least the target portion 145. For example, the jig 60 may sequentially heat the portion that will become the target portion 145 while pressing the entire sealing member 140 along one side 12f. In this case, the heater unit 61, which is separate from the jig 60, may be moved, or the direction of heat radiation from the heater unit 61 may be changed. Alternatively, the heater unit 61 may have multiple divided heating units, and the heating area may be sequentially changed by switching the heating unit that performs heating.

[0111] [Note] The technical ideas that can be understood from the embodiments and modified examples will be described. [1] A method for manufacturing an electrode, the electrode comprising: a current collector having a polygonal shape with at least one side longer than one meter in plan view; an active material layer provided on a surface of the current collector; and one or more sealing members welded to the surface of the current collector, the manufacturing method including: an arrangement step of arranging the sealing members on the surface of the current collector along the sides; and a welding step of bringing a jig into surface contact with a target portion of the sealing member, the target portion having a dimension in a direction in which the side extends that is smaller than the side, and heating the target portion while pressing the target portion against the current collector, thereby forming a welded portion in which the target portion is welded to the surface of the current collector, the welding step being performed a plurality of times between both end portions of the sealing member in the direction in which the side extends, and in second and subsequent welding steps, the target portion is a portion of the sealing member that is at least partially displaced in the direction in which the side extends from the target portion in the previous welding step.

[0112] [2] The method for manufacturing an electrode according to [1], wherein in the disposing step, the sealing members are disposed on both sides of the current collector, and the welding step is performed on the sealing members disposed on both sides of the current collector.

[0113] [3] The method for manufacturing an electrode according to [1] or [2], wherein in the second or subsequent welding steps, a portion of the target portion in the direction in which the side extends overlaps with the target portion in the previous welding step.

[0114] [4] The method for manufacturing an electrode described in any one of [1] to [3], wherein the jig has a heater portion that heats the target portion while making surface contact with the target portion, and corners that are located around the heater portion and come into contact with the sealing member when the target portion is heated by the heater portion, and the corners are curved.

[0115] [5] The method for manufacturing an electrode according to any one of [1] to [4], wherein the dimension of the target portion in the direction in which the side extends is 720 mm or less. [Explanation of symbols]

[0116] L...dimension, Y...first direction, Z...second direction, 11, 11a...electrode, 12...current collector, 12a...first surface, 12b...second surface, 12f...side, 23...positive electrode active material layer, 33...negative electrode active material layer, 41a...welded portion, 60...jig, 61...heater portion, 64a...corner portion, 140...sealing member, 143a, 144a...edge portion, 145...target portion.

Claims

1. A method for manufacturing an electrode, the electrode comprising: A current collector having a polygonal shape with at least one side longer than 1 meter in plan view; an active material layer provided on a surface of the current collector; one or more sealing members welded to the surface of the current collector; The manufacturing method includes: a placement step of placing the sealing member on the surface of the current collector along the side; a welding process in which a jig is brought into surface contact with a target portion of the sealing member, the target portion having a dimension in a direction in which the side extends that is smaller than the side, and the target portion is heated while being pressed against the current collector, thereby forming a welded portion in which the target portion is welded to a surface of the current collector, A method for manufacturing an electrode, wherein the welding process is performed multiple times between both ends of the sealing member in the direction in which the side extends, and in the second or subsequent welding process, the target part is a part of the sealing member that is at least partially shifted in the direction in which the side extends from the target part in the previous welding process.

2. In the disposing step, the sealing members are disposed on both surfaces of the current collector, The welding step is performed on the sealing members disposed on both sides of the current collector. A method for manufacturing the electrode according to claim 1.

3. In the second or subsequent welding steps, a part of the target portion in the extending direction of the side overlaps with the target portion in the previous welding step. The method for manufacturing the electrode according to claim 1 or 2.

4. the jig has a heater portion that heats the target portion while being in surface contact with the target portion, and corner portions that are located around the heater portion and come into contact with the sealing member when the heater portion heats the target portion, The corners are curved. The method for manufacturing the electrode according to claim 1 or 2.

5. The dimension of the target portion in the direction in which the side extends is 720 mm or less. The method for manufacturing the electrode according to claim 1 or 2.

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