Manufacturing method of power storage module

Abstract

To provide a manufacturing method of a power storage module in which an occurrence of tearing or denting in a side part (particularly, a resin sheet) along a laminating direction is suppressed during a heat welding.SOLUTION: There is provided a manufacturing method of a power storage module. The method includes the steps of: forming a composite current collector by primary-welding a current collector and a resin sheet disposed so as to overlap an outer peripheral end part of both surfaces of the current collector in a thickness direction by using a flat plate-shaped heater disposed in parallel with a surface direction of the current collector; laminating the plurality of composite current collectors in the thickness direction orthogonal to the surface direction; and heating a laminated end surface of the resin sheet arranged to face each other by the lamination from the surface direction and secondary-welding the resin sheet arranged to face each other.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] BACKGROUND ART In recent years, there has been much research being conducted on power storage modules, which are power storage devices equipped with a plurality of battery cells and used to store electricity. For example, Patent Document 1 discloses an electricity storage module. Specifically, the document describes an electricity storage module including a laminate and a reinforcing member provided on the laminate, the laminate including a first electrode including a first current collector and a first active material layer provided on a first surface of the first current collector, a second current collector and a second active material layer provided on a second surface of the second current collector and having a polarity different from that of the first active material layer, the second electrode being laminated on the first electrode such that the second active material layer faces the first active material layer, and a frame-shaped spacer provided between the first current collector and the second current collector so as to surround the first active material layer and the second active material layer when viewed in the stacking direction of the first and second electrodes, the spacer including a first inner surface facing the space and a first outer surface opposite the first inner surface, the reinforcing member provided on the first outer surface so as to cover the first outer surface around the entire periphery of the first outer surface, and a metal layer disposed along the first outer surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-027201 Summary of the Invention [Problem to be solved by the invention]

[0004] When an energy storage module is configured by placing multiple resin sheets with an electrode assembly sandwiched between them, the resin sheets and the electrode assembly are heated with a heater to weld them together. In conventional energy storage modules, for example, a resin sheet and a current collector are placed so that the resin sheet overlaps the outer peripheral edge of the surface of the current collector, and then a braided heater is used to weld them together to obtain a welded body. The resulting welded bodies are then stacked one on top of the other, and a resin sheet is further welded to the side surfaces (side faces) along the stacking direction to form a module. However, it has been discovered that with conventional methods for manufacturing energy storage modules, depending on the type of heater used during the initial welding, i.e., when welding the resin sheet and the current collector to create a welded body, uneven temperature distribution is likely to occur in the heated area. Because uneven temperature distribution remains as thermal history, when welded bodies are stacked to form a module, uneven thickness may occur when the resin sheet is heat-welded, resulting in locally thin areas in the welded resin sheet. This raises concerns that stress may concentrate in the thin areas and cause strong pulling, resulting in localized tears or dents on the side surfaces.

[0005] The problem that one embodiment of the present disclosure aims to solve is that it takes into consideration the above circumstances, and aims to provide a method for manufacturing a storage module that suppresses the occurrence of cracks or dents in the side portions (particularly the resin sheets) along the stacking direction when heat-welded. [Means for solving the problem]

[0006] The means for solving the above problems include the following aspects. <1> A method for manufacturing an electricity storage module, comprising: a step of forming a composite current collector by primarily welding a current collector and a resin sheet arranged so as to overlap an outer peripheral end portion of each side of the current collector in a thickness direction by a plate-shaped heater arranged parallel to a surface direction of the current collector; a step of stacking a plurality of the composite current collectors in a thickness direction perpendicular to the surface direction; and a step of heating stack end faces of the resin sheets arranged opposite each other by the stacking from the surface direction to secondary weld the oppositely arranged resin sheets. <2> The resin sheet contains at least one of a polyethylene resin and a polypropylene resin. <1> A method for manufacturing the storage module according to claim 1. <3> The step of secondary welding includes welding the laminate end surfaces by non-contact heating using a non-contact heater. <1> or <2> A method for manufacturing the storage module according to claim 1. <4> The flat heater is a contact heater. <1> ~ <3> 10. A method for manufacturing the electricity storage module according to any one of the preceding items. <5> The method includes a step of temporarily welding the resin sheet and the current collector before the step of primarily welding. <1> ~ <4> 10. A method for manufacturing the electricity storage module according to any one of the preceding items. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, there is provided a method for manufacturing an electricity storage module in which the occurrence of tears or dents in the side portions (particularly the resin sheets) along the stacking direction during heat welding is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of the positional relationship of a resin sheet disposed on a current collector. [Figure 2] FIG. 2 is a schematic diagram showing an example of a method for welding a resin sheet to the outer peripheral edge of a current collector using a plate heater. [Figure 3] FIG. 3 is a schematic diagram showing an example of a method for welding resin sheets arranged on the outer peripheral edges of both sides of a current collector by heating and pressurizing them with a plate heater, as viewed from a direction perpendicular to the stacking direction. [Figure 4] FIG. 4 is a schematic process diagram showing an example of a method in which a resin sheet is temporarily welded to the outer peripheral edge of each side of a current collector, and then a primary welding step is carried out. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an example of a battery structure configured as a bipolar type using a composite current collector according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, one embodiment of a battery according to the present disclosure will be described with reference to the drawings. The drawings in this disclosure are schematic illustrations, and the size and shape of each part are appropriately exaggerated for ease of understanding. In addition, the same reference numerals are used for the same or equivalent elements, and redundant explanations are omitted.

[0010] In the present disclosure, the resin sheet is a concept that encompasses not only what is generally called a resin sheet, but also what is generally called a resin film. In the present disclosure, "depressions" include depressions, undulations, and the like.

[0011] -Method of manufacturing energy storage modules- The method for manufacturing an energy storage module according to the present disclosure includes a step of forming a composite current collector by primarily welding a current collector and a resin sheet arranged so as to overlap the outer peripheral end portion of each side of the current collector in the thickness direction using a flat heater arranged parallel to the surface direction of the current collector (hereinafter also referred to as the "primary welding step"); a step of stacking a plurality of the composite current collectors in a thickness direction perpendicular to the surface direction (hereinafter also referred to as the "stacking step"); and a step of heating the stack end faces of the resin sheets arranged opposite each other by the stacking from the surface direction to secondarily weld the oppositely arranged resin sheets (hereinafter also referred to as the "secondary welding step").

[0012] In the method for manufacturing an energy storage module according to the present disclosure, a flat heater, which has less uneven temperature distribution than other heaters such as braided heaters, is used as a heater, and a current collector and a resin sheet are welded together by applying heat and pressure to form a composite current collector. This reduces the occurrence of thickness variations, such as the occurrence of locally thin areas in the welded resin sheet. Therefore, even during the secondary welding of the resin sheet portion, which is performed after the primary welding of the current collector and the resin sheet, the effects of stress caused by thickness variations are reduced, and it is believed that the occurrence of tears or dents in the side portions along the stacking direction can be effectively suppressed. The stacking direction refers to the thickness direction in which, for example, negative electrode active material layer / negative electrode current collector / positive electrode current collector / positive electrode active material layer are stacked when modularizing.

[0013] [Primary welding process] In the primary welding process, a current collector and a resin sheet arranged to overlap the outer peripheral edge of both sides of the current collector in the thickness direction are primarily welded together using a flat heater arranged parallel to the surface of the current collector. This forms a composite current collector. In this process, welding using a flat heater provides a highly uniform thermal history to the resin sheet, thereby suppressing thickness variations such as the formation of locally thin areas. This effectively suppresses the occurrence of cracks or dents that tend to occur when the resin sheet is heat-welded on the side surfaces in the secondary welding process described below. In particular, when forming a long composite current collector, this method suppresses the occurrence of cracks or dents that tend to occur on the end surfaces (side surfaces) in the transverse direction (TD), which is perpendicular to the machine direction (MD).

[0014] In the present disclosure, the current collector refers to a laminate including a negative electrode current collector and a positive electrode current collector that are in contact with each other. In the case where a current collector in which a negative electrode current collector and a positive electrode current collector are bonded together has a negative electrode active material layer on one side, that is, the exposed surface of the negative electrode current collector, and a positive electrode active material layer on the other side, that is, the exposed surface of the positive electrode current collector, the current collector in the present disclosure refers to a laminate of negative electrode active material layer / negative electrode current collector / positive electrode current collector / positive electrode active material layer. A flat heater arranged parallel to the surface direction of the current collector includes not only a case where it is in a parallel relationship (tilt angle 0°), but also a case where it has an inclination that can be recognized as being in a parallel relationship at a glance (tilt angle greater than 0° and less than 1°) from the viewpoint of being in close contact with the surface of the resin sheet.

[0015] It is preferable that the resin sheet is superimposed on the outer peripheral edge of at least one surface of the current collector in the electrode body, and is arranged so as to extend in the opposite direction from the outer peripheral edge of the current collector toward the inside of the current collector and protrude outward from the outer peripheral edge.

[0016] FIG. 1 is a schematic diagram showing an example of the positional relationship of a resin sheet disposed on a current collector. As shown in FIG. 1, resin sheet S1, resin sheet S2, resin sheet S3, and resin sheet S4 are arranged so as to avoid overlapping with the negative electrode active material layer 40 and to overlap with copper foil 20, which is a current collector. In FIG. 1, multiple resin sheets S1 to S4 are arranged along the outer periphery of copper foil (current collector) 20, resulting in an arrangement in which rectangular frame-shaped resin sheets are arranged on the edge of the current collector. The present disclosure is not limited to this arrangement, and may also be an embodiment in which a single resin sheet punched into a rectangular frame is arranged on the edge of the current collector. From the perspective of reducing waste of resin sheets due to punching, an embodiment in which multiple resin sheets are arranged in a frame shape as shown in FIG. 1 is preferred.

[0017] The current collector preferably includes a positive electrode current collector and a negative electrode current collector, and may be a current collector in which a positive electrode current collector and a negative electrode current collector are bonded together.

[0018] The positive electrode current collector preferably contains, for example, nickel, iron, stainless steel (SUS), titanium, or aluminum. From the viewpoint of excellent corrosion resistance and conductivity, the positive electrode current collector is preferably aluminum foil. The thickness of the positive electrode current collector is, for example, 8 μm to 10 μm.

[0019] The negative electrode current collector is preferably made of, for example, copper, stainless steel (SUS), or nickel. The negative electrode current collector is preferably made of copper foil, which has excellent corrosion resistance and conductivity. The thickness of the negative electrode current collector is, for example, 10 μm to 20 μm.

[0020] The flow of the primary welding step will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a schematic diagram showing an example of a method for welding a resin sheet to the outer peripheral edge of a current collector using a plate heater. Fig. 3 is a schematic diagram showing an example of a method for welding resin sheets arranged at the outer peripheral edges of both sides of a current collector by heating and pressurizing them with a plate heater, as viewed from a direction perpendicular to the stacking direction. FIG. 3 shows a portion of the bipolar battery structure, which includes copper foil 20 as a negative electrode current collector, a negative electrode active material layer 40 disposed on the surface of the copper foil 20, aluminum foil 30 as a positive electrode current collector, and a positive electrode active material layer 50 disposed on the surface of the aluminum foil 30, and the negative electrode current collector (copper foil 20) and the positive electrode current collector (aluminum foil 30) are in contact with each other.

[0021] As shown in FIG. 2, in the first welding step, a flat heater 70A is positioned so as to include the overlapping region between the resin sheet S1 and the copper foil 20 serving as a current collector, and a flat heater 70B is further positioned so as to include the overlapping region between the resin sheet S3 and the copper foil 20 serving as a current collector, and they are welded by applying heat and pressure. Here, as shown in FIG. 3, welding can be performed by placing a resin sheet 10B on the outer peripheral edge of the surface of the copper foil 20 bearing the negative electrode active material layer 40, and placing a resin sheet 10A on the outer peripheral edge of the surface of the aluminum foil 30 bearing the positive electrode active material layer 50, and applying pressure and heat in the direction of arrow F using flat heaters positioned to sandwich the resin sheets 10A and 10B. This welds the resin sheet 10B to the copper foil 20, and also welds the resin sheet 10A to the aluminum foil 30.

[0022] In the above, the resin sheets S1 and S3 arranged as shown in FIG. 2 are simultaneously welded to the current collector. However, the welding of the resin sheet S1 to the outer peripheral end of the current collector and the welding of the resin sheet S3 to the outer peripheral end of the current collector may be performed separately.

[0023] The flat heater, also called a plate heater, is preferably a contact heater in which at least the heat generating portion is flat. A flat heating element can be used for the flat heater, and it may be a heating wire having a flat surface. By bringing the surface of the flat heating portion into close contact with the surface of the resin sheet, unevenness in the thickness of the resin sheet after heating can be suppressed.

[0024] As the material for the resin sheet, known thermoplastic resins can be used, for example, polypropylene-based resins such as polypropylene (PP); polyethylene-based resins such as polyethylene (PE); and the like. The polyethylene resin refers to a homopolymer having ethylene-derived structural units or a copolymer having ethylene-derived structural units and structural units derived from a monomer copolymerizable with ethylene. The polypropylene resin refers to a homopolymer having propylene-derived structural units or a copolymer having propylene-derived structural units and structural units derived from a monomer copolymerizable with propylene.

[0025] Resin sheets containing at least one of polyethylene-based resin and polypropylene-based resin tend to be relatively soft, which can easily cause thickness variations during the primary welding process, leading to tears or dents when the resin sheets are welded together in the secondary welding process described below. In contrast, the manufacturing method for an energy storage module disclosed herein uses a flat heater in the primary welding process to weld the resin sheets together. This effectively prevents thickness variations that can easily occur when welding is performed using other heaters, such as a braided heater, even when polypropylene-based resin or polyethylene-based resin is used as the resin sheet material. This also effectively prevents tears or dents that can easily occur in the subsequent secondary welding process.

[0026] The thickness of the resin sheet is preferably 50 μm to 200 μm, and more preferably 100 μm to 150 μm. When the thickness of the resin sheet is within the above range, the occurrence of unevenness in the thickness of the resin sheet, which tends to occur during primary welding, is likely to be reduced.

[0027] [Lamination process] In the lamination step, a plurality of composite current collectors are laminated in a thickness direction perpendicular to the surface direction of the current collectors, thereby obtaining a laminate in which a plurality of composite current collectors are laminated.

[0028] The lamination can be performed by, for example, stacking the composite current collector formed in the primary welding step and a separator. For example, when the composite current collector is a current collector formed by bonding a negative electrode current collector and a positive electrode current collector together, the composite current collector has a negative electrode active material layer on the exposed surface of the negative electrode current collector, which is one side of the current collector, and a positive electrode active material layer on the exposed surface of the positive electrode current collector, which is the other side, it is preferable to laminate the composite current collectors with a separator interposed therebetween. This results in a laminate having a laminate structure of composite current collector / separator / composite current collector / ..., and can form a laminate having a composite current collector and an electrode assembly, such as the bipolar battery structure shown in Figure 5.

[0029] The laminate preferably has a unit structure in which a composite current collector having a negative electrode active material layer / negative electrode current collector / positive electrode current collector / positive electrode active material layer, a separator, and a composite current collector having a negative electrode active material layer / negative electrode current collector / positive electrode current collector / positive electrode active material layer are laminated in this order.

[0030] [Secondary welding process] In the secondary welding process, the laminated end surfaces (i.e., side surfaces) of the resin sheets arranged opposite each other by stacking them in the above-mentioned stacking process are heated from a surface direction perpendicular to the stacking direction, thereby secondary welding the resin sheets arranged opposite each other.

[0031] Heating the laminated end faces (side faces) of the resin sheets from the surface direction means heating the side surfaces (side faces) along the lamination direction of the part formed by the opposing resin sheets in the laminate formed in the lamination step from the side of the side faces. The side faces refer to the other four faces of the laminate in the lamination direction excluding the two outermost surfaces.

[0032] Furthermore, a resin sheet (spacer resin sheet) may be interposed as a spacer between the resin sheets arranged opposite each other in the stacking direction of the laminate. The material of the spacer resin sheet is not particularly limited, and a known thermoplastic resin may be used, and it may be formed from the same material as the resin sheets. When a spacer resin sheet is provided between the resin sheets, it is preferable that a secondary welding is performed to weld a laminate including three layers of resin sheet / spacer resin sheet / resin sheet, and the resin sheet and the spacer resin sheet are welded to each other.

[0033] The method for carrying out the secondary welding is not particularly limited, and examples thereof include a method using a non-contact heater such as a radiant heat heater, such as a ceramic heater or an infrared heater.

[0034] The flow of the secondary welding process will be described with reference to Fig. 5. Fig. 5 is a schematic cross-sectional view showing an example of a bipolar battery structure using a composite current collector according to the present disclosure. The battery structure shown in Fig. 5 is an example of a laminate formed by laminating a composite current collector and a separator in a lamination process.

[0035] First, in the bipolar battery structure shown in FIG. 5, a positive electrode terminal electrode and a negative electrode terminal electrode are disposed at the outermost positions in the stacking direction, and multiple bipolar electrodes are stacked between the positive electrode terminal electrode and the negative electrode terminal electrode. The positive electrode terminal electrode includes an aluminum foil 30 serving as a positive electrode current collector and a positive electrode active material layer 50 formed on the aluminum foil 30. The negative electrode terminal electrode includes a copper foil 20 serving as a negative electrode current collector and a negative electrode active material layer 40 formed on the copper foil 20. The bipolar electrode includes a laminated current collector foil formed by laminating the aluminum foil 30 serving as a positive electrode current collector and the copper foil 20 serving as a negative electrode current collector. The positive electrode active material layer 50 is formed on the aluminum foil 30 of the laminated current collector foil, and the negative electrode active material layer 40 is formed on the copper foil 20. A separator 80 is disposed between the positive electrode active material and the negative electrode active material facing each other in the stacking direction. The separator 80 is impregnated with an electrolyte. A resin sheet 10 is welded to the outer peripheral edge of the laminated current collector foil, which is the current collector of the present disclosure, to form a composite current collector. In Fig. 5, spacer resin sheets 90 serving as spacers are interposed between the resin sheets 10 arranged opposite each other in the stacking direction. In the secondary welding process of the present disclosure, in a bipolar battery structure formed by stacking a composite current collector and a separator, the side surfaces (side faces) along the stacking direction of a portion formed by opposing resin sheets (i.e., in FIG. 5, resin sheet 10 and spacer resin sheet 90 and resin sheet 10) are heated non-contact with a non-contact heater (for example, a radiant heat heater such as an infrared heater). This causes resin sheet 10 and spacer resin sheet 90 to be welded together, forming welded region B. In FIG. 5, the secondary welding is performed by fixing the ends of the outermost surfaces (top and bottom surfaces in FIG. 5) in the stacking direction of the bipolar battery structure using restraint plates 100.

[0036] [Temporary welding process] The method for manufacturing an electricity storage module according to the present disclosure preferably further includes a step of temporarily welding the resin sheet and the current collector at the outer peripheral edge of the current collector before the primary welding step (hereinafter also referred to as the "temporary welding step"). By including the temporary welding step, it is possible to prevent the welding position of the resin sheet, which is welded in the subsequent primary welding step, from shifting from the designed position on the current collector.

[0037] The temporary welding can be performed using, for example, a welding iron.

[0038] The flow of temporary welding will be described with reference to Fig. 4. Fig. 4 is a schematic process diagram showing an example of a method for performing a primary welding step after temporary welding a resin sheet to the outer peripheral edge of each side of a current collector (copper foil 20 and aluminum foil 30).

[0039] First, as shown in FIG. 4(1), a resin sheet 10A is placed so that the outer peripheral edge of the aluminum foil 30, which serves as a positive electrode current collector, overlaps with the resin sheet 10A. In this case, it is preferable that the resin sheet 10A does not overlap with the positive electrode active material layer 50. Next, as shown in FIG. 4(2), a resin sheet 10B is placed so that the outer peripheral edge of the copper foil 20, which serves as a negative electrode current collector, overlaps with the resin sheet 10B. In this case, it is preferable that the resin sheet 10B does not overlap with the negative electrode active material layer 40. Then, as shown in FIG. 4(3), a welding iron (a so-called electric heating iron) 60A is pressed against the resin sheet 10A and heated, thereby temporarily welding the resin sheet 10A to the aluminum foil 30. Similarly to the resin sheet 10A, the welding iron 60B is pressed against the resin sheet 10B and heated, thereby temporarily welding the resin sheet 10B to the copper foil 20. During the pre-welding, the resin sheets 10A and 10B may be pre-welded simultaneously or separately. After that, the process proceeds to the next primary welding step. In the primary welding step, as described above, the resin sheet 10A is pressed against the flat heater 70A to heat it, and the resin sheet 10B is pressed against the flat heater 70B to heat it, thereby welding the resin sheets 10A and 10B to the aluminum foil 30 and the copper foil 20, respectively (see FIG. 4(4)).

[0040] [Other steps] The method for manufacturing an energy storage module according to the present disclosure may further include other steps in addition to the primary welding step, the stacking step, the secondary welding step, and the temporary welding step. Examples of such other steps include the following steps. (1) A fixing step of fixing a laminate of a composite current collector having an active material layer and a separator with a jig or the like before the secondary welding step. (2) After the secondary welding process, the lamination process seals the product with a laminate film. [Example]

[0041] The present disclosure will be described in more detail below with reference to examples, but the scope of the present disclosure is not limited to the specific examples shown below.

[0042] Example 1 An electrode body was prepared, in which a current collector consisting of an aluminum foil (positive electrode current collector) and a copper foil (negative electrode current collector) was bonded together, had a positive electrode active material layer 50 on one side (the exposed surface of the aluminum foil 30) and a negative electrode active material layer 40 on the other side (the exposed surface of the copper foil 20). A polyethylene sheet (resin sheet) was placed along the four outer edges of the aluminum foil side of the electrode body, as shown in FIG. 1. Furthermore, a polyethylene sheet (resin sheet) was also placed along the four outer edges of the copper foil side, as shown in FIG. 1. A flat heater was then placed in the position shown in FIG. 2, and heat and pressure were applied in the direction of arrow F so that the resin sheet was sandwiched between the current collector, as shown in FIG. 3, to produce a composite current collector in which the resin sheet was fused to the current collector (primary welding process). Next, multiple composite current collectors were stacked with separators sandwiched between them to form a bipolar battery structure as shown in Figure 5 (lamination process). A spacer resin sheet 90 was sandwiched between a polyethylene sheet (resin sheet) 10 on the aluminum foil side and a polyethylene sheet (resin sheet) 10 on the copper foil side, resulting in a laminate structure in which multiple resin sheets are adjacent to each other. Thereafter, secondary welding was performed by non-contact heating of the side surfaces (side faces) along the stacking direction of the portion formed by stacking adjacent polyethylene sheets 10 and spacer resin sheets 90 from the surface direction of the current collector using an infrared heater 110 as shown in Figure 5 (secondary welding process).

[0043] (Comparative Example 1) A composite current collector was produced in the same manner as in Example 1, except that a braided heater made of a heating wire whose heating portion was not flat was used instead of the flat heater in Example 1, and then a lamination step and a secondary welding step were carried out.

[0044] As a result of the above Example 1 and Comparative Example 1, in Example 1, primary welding was performed using a flat heater, and therefore no cracks or dents were observed on the sides, which tend to occur when the resin sheet is heated from the side surface (side surface) along the stacking direction during the subsequent secondary welding. In contrast, in Comparative Example 1, which used a braided heater, cracks and dents were observed on the sides. Thus, it was found that the Examples could suppress the occurrence of tears or dents on the side portions (particularly the resin sheets) along the stacking direction when heat-welded, compared to the Comparative Examples. [Explanation of symbols]

[0045] 10, 10A, 10B Resin sheet 20 copper foil 30 aluminum foil 40 Negative electrode active material layer 50 Cathode active material layer 60A, 60B welding iron 70A, 70B Flat heater 80 Separator 90 Spacer resin sheet 100 restraint plate 110 Infrared heater B Welding area F Heat and pressure direction S1, S2, S3, S4 Resin sheets

Claims

1. a step of forming a composite current collector by primarily welding a current collector and a resin sheet disposed so as to overlap outer peripheral edges of both surfaces of the current collector in a thickness direction by a plate-shaped heater disposed parallel to a surface direction of the current collector; stacking a plurality of the composite current collectors in a thickness direction perpendicular to the surface direction; a step of heating the laminated end surfaces of the resin sheets arranged opposite to each other by the lamination from the surface direction to perform secondary welding of the resin sheets arranged opposite to each other; A method for manufacturing an electricity storage module comprising:

2. The method for manufacturing an electricity storage module according to claim 1 , wherein the resin sheet contains at least one of a polyethylene-based resin and a polypropylene-based resin.

3. 3. The method for manufacturing an electric storage module according to claim 1, wherein the secondary welding step includes welding the stacked end surfaces by non-contact heating using a non-contact heater.

4. The method for manufacturing an electric storage module according to claim 1 or 2, wherein the flat heater is a contact heater.

5. The method for manufacturing an electricity storage module according to claim 1 or 2, further comprising a step of temporarily welding the resin sheet and the current collector together before the primary welding step.

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