Battery module and its manufacturing method

Abstract

In a configuration in which a single bipolar electrode foil 2X protrudes outward in the planar direction from a sealing portion 6a at the periphery of a cell in a battery module 1 in which multiple cells are stacked, the penetration portion of the bipolar electrode body in the sealing portion is reliably sealed. [Solution] In the method for manufacturing a battery module, a first laminate is formed by sealing the periphery of the region between the outermost electrode foil 2a of one of the battery modules and one bipolar electrode foil with a sealing material 6a_1, and a sealing material 6b and a heat conductive foil 12 are heat-sealed to the band-shaped region at the periphery of the outer surface of one bipolar electrode foil. A second laminate is formed by sealing the periphery of the region between the other outermost electrode foil 2b of the battery module and one electrolyte layer facing one bipolar electrode foil with a sealing material 6a_2, the first laminate and the second laminate are superimposed, and the heat conductive foil is heated to heat-seal the sealing portion 6a_2 to the heat conductive foil 12.

Description

Technical Field

[0001] The present invention relates to a battery module used in a power storage device and a method for manufacturing the same, and more particularly to a structure for cooling the battery module.

Background Art

[0002] Secondary batteries such as lithium-ion secondary batteries used in power storage devices, briefly stated, have a laminated structure in which a positive electrode active material layer coated on a current collector foil (positive electrode foil) that may be a metal foil and a negative electrode active material layer coated on a current collector foil (negative electrode foil) that may be a metal foil face each other with a separator (in the case of a liquid-based battery) or a solid electrolyte layer (in the case of an all-solid battery) immersed in an electrolytic solution interposed therebetween. Various configurations have been proposed for various problems that can occur in such secondary batteries. For example, in Patent Document 1, in order to suppress damage to a power storage stack when an external impact is input, a power storage stack including a plurality of power storage modules arranged in a first direction, a pair of restraint plates sandwiching the power storage stack in the first direction, a pair of side wall portions facing each other in a second direction orthogonal to the first direction such that the power storage stack is positioned therebetween, and a plurality of stoppers respectively arranged between the power storage stack and the pair of side wall portions on both outer sides of the power storage stack in the second direction are provided. Each of the pair of restraint plates has an outer main surface located on the side opposite to the side where the power storage stack is positioned, and a plurality of reinforcing portions are provided on each of the outer main surfaces of the pair of restraint plates so as to extend along the second direction and be arranged in a third direction orthogonal to the first direction and the second direction. Each of the plurality of stoppers is arranged at a position overlapping the corresponding reinforcing portion in the first direction on both end portions sides in the second direction of the corresponding reinforcing portion among the plurality of reinforcing portions. A power storage device having such a configuration has been proposed. In Patent Document 2, in a laminated battery in which a plurality of single cells are connected in series and laminated, in order to suppress voltage fluctuations due to heat storage, improve battery characteristics, and extend battery life, cooling tabs are attached to a plurality of current collectors, and a configuration is proposed in which the heat dissipation effect of the cooling tab installed at the central position in the thickness direction during current collector lamination is the largest, and the heat dissipation effect of the tab gradually decreases toward both end sides in the thickness direction.

Prior Art Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-177537 [Patent Document 2] Japanese Patent Publication No. 2005-71784 [Patent Document 3] Japanese Patent Publication No. 2024-42569 [Patent Document 4] Japanese Patent Publication No. 2024-88396 [Overview of the project] [Problems that the invention aims to solve]

[0004] As a configuration for the secondary battery module described above, a configuration is known in which multiple laminated structures are stacked, with positive electrode foils sandwiched between negative electrode foils. Except for the outermost electrode foil of the module, the positive electrode foil and negative electrode foil are integrated with the negative electrode foil and positive electrode foil of the adjacent laminated structure, respectively, to form a "bipolar electrode foil," with an electrolyte layer sandwiched between each of the multiple bipolar electrode foils. However, since the battery module generates heat during operation, it is preferable to cool it appropriately. In this regard, in the case of a module in which multiple bipolar electrode foils are stacked with an active material layer and an electrolyte layer sandwiched between them, even if a cooler is brought into contact with the outermost stacked cell to cool it, depending on the thermal conductivity in the thickness direction of the stacked cells and the cooling performance, it may not be possible to sufficiently remove heat from the cells stacked on the inside, and it may not be cooled sufficiently. In that case, heat may build up, the inside may become hot, and degradation may progress.

[0005] As described above, in a structure in which multiple cells are stacked by sandwiching an active material layer and an electrolyte layer between multiple bipolar electrode foils, one possible method for cooling the inner cell is to make the bipolar electrode foil of the inner cell (or, as in Patent Document 2, a tab connected thereto) protrude outward in the planar direction of the cell, beyond the seal portion that seals the electrolyte layer at the periphery of the cell, and then cool the protruding portion. In this regard, in a configuration in which the bipolar electrode foil or tab protrudes from the seal portions on both sides in the planar direction of the cell, it is necessary to form a structure in which the area on the electrolyte layer side is reliably sealed by the seal portion when the bipolar electrode foil or tab penetrates the seal portion. In particular, in the case of liquid-based battery cells, if the sealing of the penetration portion of the bipolar electrode foil or tab in the seal portion is incomplete, electrolyte may leak from that portion.

[0006] In view of the above circumstances, the main object of the present invention is to ensure that the portion of the bipolar electrode foil that penetrates the seal portion is reliably sealed in order to cool the inner cell in a battery module (a stack of multiple battery cells) in which multiple bipolar electrode foils are stacked, by having the inner bipolar electrode foil protrude outward in the planar direction from the seal portion that seals the electrolyte layer at the periphery of the cell, and cooling the protruding portion. [Means for solving the problem]

[0007] According to the present invention, the above problem is solved by a method for manufacturing a battery module in which a plurality of cells are stacked, each cell having a positive electrode active material layer coated on an electrode foil which is a positive electrode foil and a negative electrode active material layer coated on an electrode foil which is a negative electrode foil, facing each other with an electrolyte layer in between, wherein, except for the outermost electrode foil of one cell and the outermost electrode foil of the other cell, each of the positive electrode foils and negative electrode foils of the cells are integrated with the negative electrode foil and positive electrode foil of the adjacent cell, forming a bipolar electrode foil, the plurality of cells are connected in series, and a seal portion is formed in which the region between the outermost electrode foil of one cell and the outermost electrode foil of the battery module is sealed with a heat-sealable seal material at the periphery of the electrode foil and the electrolyte layer, The first laminate is constructed by laminating electrode foils coated with the positive and negative electrode active material layers and the electrolyte layer from one outermost electrode foil of the battery module to one bipolar electrode foil, sealing the periphery of the region between one outermost electrode foil of the battery module and the one bipolar electrode foil with the sealing material to form a part of the sealed portion, wherein the one bipolar electrode foil protrudes outward from the sealed portion of the sealing material in at least one planar direction of the one bipolar electrode foil, heat-sealing the sealing material to a strip-shaped region on the outer surface of the one bipolar electrode foil where the sealed portion will be located, and further heat-sealing a heat-conducting foil to the outside thereof. The process involves laminating the electrode foil coated with the positive and negative electrode active material layers and the electrolyte layer from the outermost electrode foil of the other battery module to the electrolyte layer facing the first bipolar electrode foil, sealing the periphery of the region between the outermost electrode foil of the other battery module and the first electrolyte layer with the sealing material to form another part of the sealed portion and thereby constructing a second laminate, A step of superimposing the first laminate and the second laminate such that the heat conductive foil of the first laminate contacts the surface of another part of the sealing portion of the second laminate, A step of heating the heat conductive foil to heat-weld the heat conductive foil and the sealing material in the strip-shaped region of the second laminate. This is achieved by a method that includes [a specific method].

[0008] In the above configuration, the "battery module" may be a battery module for a secondary battery such as a lithium-ion secondary battery, and as described above, multiple cells are stacked in which a positive electrode active material layer coated on an electrode foil which is a positive electrode foil and a negative electrode active material layer coated on an electrode foil which is a negative electrode foil are facing each other with an electrolyte layer in between. Except for the outermost electrode foil of one side of the battery module and the outermost electrode foil of the other side, each positive electrode foil and negative electrode foil of each cell are integrated with the negative electrode foil and positive electrode foil of the adjacent cell, forming a bipolar electrode foil. As a result, multiple cells are connected in series, and a seal portion is formed in which the region between the outermost electrode foil of one side of the battery module and the outermost electrode foil of the other side is sealed with a heat-sealable sealant at the periphery of the electrode foil and electrolyte layer. The positive electrode foil, positive electrode active material layer, negative electrode foil, negative electrode active material layer, separator, electrolyte, and heat-sealable sealant may be of a conventional form. Furthermore, in such a battery module, and in particular in the present invention, in order to cool the cells inside the battery module, any one bipolar electrode foil in the middle of the battery module has a portion that protrudes outward in the planar direction, penetrating the seal portion at the periphery of the battery module, and that portion is cooled. As a result, heat is released from the cells inside the battery module, making it possible to suppress battery degradation.

[0009] As described above, in the case where the bipolar electrode foil in the middle of the battery module protrudes through the seal portion, if all the electrode bodies (electrode foil coated with an active material layer) and the electrolyte layer to be laminated in the battery module are to be heat-sealed with a sealing material at their periphery, the sealing by the sealing material may be insufficient at the portion of the bipolar electrode foil that protrudes from the seal portion. More specifically, as shown in Figure 3(A), when the electrode bodies to be laminated in the battery module 1 (electrode bodies 2a-3, 2b-4 on both sides of the module and the bipolar electrode bodies 4-2-3 between them) and the electrolyte layer 5 are to be laminated (spacers 7 may be interposed between the electrode foils) and the periphery is to be heat-sealed with sealing materials 6, 6a, a method is usually used in which a heat-sealable sealing material 6a is placed at the periphery between the electrode foil and the electrolyte layer, and the sealing material is heated by irradiating it with infrared (IR) light (IR welding). However, as shown in Figure 3(B), if the bipolar electrode foil 2X in the middle of the battery module 1 protrudes from the seal portion 6a, a portion x is created in which the infrared light IR that should be irradiated onto the seal material 6a is blocked by the protruding bipolar electrode foil 2X, resulting in insufficient thermal welding of the seal material by infrared light in that portion x.

[0010] Therefore, in this invention, to put it simply, one side and the other side of the bipolar electrode foil protruding from the seal portion of the battery module are manufactured separately, and then the manufactured parts are superimposed to complete the battery module.

[0011] Specifically, as described above, first, for one part of the battery module, an electrode body (electrode foil coated with positive and negative electrode active material layers) and an electrolyte layer are laminated from the outermost electrode foil on one side of the battery module to a bipolar electrode foil. The periphery of the region between the outermost electrode foil on one side of the battery module and the bipolar electrode foil is sealed with a sealing material to form a part of the sealed area, thereby forming the first laminate. At this time, the bipolar electrode foil is made to protrude outward from the sealed area of ​​the sealing material in at least one planar direction of the bipolar electrode foil. Furthermore, the sealing material is heat-welded to a strip-shaped region on the outer surface of the bipolar electrode foil where the sealed area will be located, and then a heat-conducting foil is heat-welded to the outside of that. The heat-conducting foil may be a foil member made of a heat-conducting material such as a metal foil, and is attached to the entire surface of the sealing material in the strip-shaped region.

[0012] On the other hand, for the other part of the battery module, an electrode body (electrode foil coated with positive and negative electrode active material layers) and an electrolyte layer are laminated from the outermost electrode foil of the other part of the battery module to the electrolyte layer that will face one bipolar electrode foil, and the periphery of the region between the outermost electrode foil of the other part of the battery module and the electrolyte layer is sealed with a sealing material to form another part of the sealed area, thereby forming a second laminate.

[0013] Subsequently, the first and second laminates are superimposed so that the heat conductive foil of the first laminate contacts the surface of another part of the sealing portion of the second laminate, and the heat conductive foil is heated. Here, heating of the heat conductive foil can be achieved by contacting the heat conductive foil with a high-temperature component or by passing an electric current through the heat conductive foil to generate Joule heat. When the heat conductive foil is heated, heat is conducted through the heat conductive foil, melting the sealing material on the surface of the other part of the sealing portion of the second laminate that is in contact with the heat conductive foil, and the heat conductive foil and the other part of the sealing portion of the second laminate are heat-welded together. Thus, the space between the outer surface of one bipolar electrode protruding from the sealing portion of the first laminate and the outer surface of one electrolyte layer in the second laminate is sufficiently sealed with the sealing material, and therefore the penetrating portion of the bipolar electrode in the sealing portion is reliably sealed.

[0014] In the above configuration, the electrolyte layer may be a solid electrolyte layer, or it may be a separator immersed in the electrolyte in the case of a liquid-type battery. In the case of a liquid-type battery, the periphery of the laminated structure of the electrode body and the separator is sealed with a sealing material to form a sealed portion, and then an injection port for injecting the electrolyte between the electrode bodies is attached by any method, and the electrolyte is injected from the injection port, filling the space between the electrode bodies with the electrolyte. In this case, in the present invention, even if the bipolar electrode foil in the middle of the battery module protrudes through the sealed portion, the sealing material around the penetration portion is well heat-sealed to the bipolar electrode foil and sealed, so that the electrolyte can be retained between the electrode bodies.

[0015] Furthermore, if the battery module is a liquid-based battery module, an electrolyte inlet may be formed on one side of the battery module, and the bipolar electrodes may protrude from the sealing portion on the other sides. That is, in the configuration of the present invention, one bipolar electrode may protrude outward from the sealing portion of the sealing material in all other plane directions except the direction in which the electrolyte inlet is formed. This is expected to enable better cooling of the battery module.

[0016] According to the above configuration, in a battery module in which an intermediate bipolar electrode body protrudes from a sealing portion, a configuration is provided in which the protruding bipolar electrode foil is welded to the sealing portion via a heat conductive foil. Thus, according to another aspect of the present invention, a battery module is provided in which a plurality of cells are stacked, in which a positive electrode active material layer coated on an electrode foil which is a positive electrode foil and a negative electrode active material layer coated on an electrode foil which is a negative electrode foil are facing each other with an electrolyte layer in between, and except for the outermost electrode foil of one of the battery modules and the outermost electrode foil of the other, each of the positive electrode foil and negative electrode foil of the cells is a bipolar electrode foil that is integrated with the negative electrode foil and positive electrode foil of the adjacent cell, and the plurality of cells are connected in series, and a sealing portion is formed in which the region between the outermost electrode foil of one of the battery modules and the outermost electrode foil of the other is sealed with a heat-sealable sealing material at the periphery of the electrode foil and the electrolyte layer, A battery module is provided in which one of the bipolar electrode foils has a portion that protrudes in the planar direction from the sealing portion, and the sealing portion on one surface of the one bipolar electrode foil is welded via a thermal conductive foil. Herein, the cell may be a liquid-type battery cell, and the electrolyte layer may be a separator that is immersed in an electrolyte. [Effects of the Invention]

[0017] Thus, according to the configuration of the present invention, in order to cool the inner cell in a battery module in which multiple cells are stacked, the inner bipolar electrode foil is made to protrude outward in the planar direction from the seal portion that seals the electrolyte layer at the periphery of the cell, and the protruding portion is cooled, and the portion of the bipolar electrode foil that penetrates the seal portion can be reliably sealed with a sealing member. The configuration of the present invention may be applied to battery modules with various configurations in which the bipolar electrode foil protrudes from the sealing member.

[0018] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention. [Brief explanation of the drawing]

[0019] [Figure 1] FIG. 1(A) is a schematic top view of a battery module to which the present embodiment is applied, and FIG. 1(B) is a schematic cross-sectional view of the battery module to which the present embodiment is applied, as viewed from line B-B in FIG. 1(A). [Figure 2] FIG. 2(A) is a schematic bottom view of a first laminate of a battery module to which the present embodiment is applied, and FIG. 2(B) is a schematic cross-sectional view thereof as viewed from line B-B. FIG. 2(C) is a schematic cross-sectional view of a second laminate of the battery module to which the present embodiment is applied. FIG. 2(D) is a partial schematic cross-sectional view of a battery module showing a state in which the first laminate and the second laminate are superimposed and their seal portions are thermally welded via a heat conductive foil. [Figure 3] FIG. 3(A) is a partial cross-sectional view of a battery module schematically showing a process for sealing the periphery of a normal battery module with a seal portion. FIG. 3(B) is a partial cross-sectional view of a battery module schematically showing a process for sealing the periphery of a battery module to which the present embodiment is applied with a seal portion.

Explanation of Reference Numerals

[0020] 1... battery module, 2... bipolar electrode foil, 2X... protruding bipolar electrode foil, 2a, 2b... electrode foils at the outermost ends of the battery module, 3... positive electrode active material layer, 4... negative electrode active material layer, 5... separator (electrolyte layer), 6... primary seal, 6a... seal portion, 6a_1... seal portion of the first laminate, 6b... strip region seal portion, 6a_2... seal portion of the second laminate, 6d... surface of the seal portion of the second laminate, 7... spacer, 10... electrolyte injection port, 12... heat conductive foil, 20... high temperature member

Best Mode for Carrying Out the Invention

[0021] The present invention will be described in detail below with reference to the accompanying drawings in several preferred embodiments. In the drawings, the same reference numerals indicate the same parts.

[0022] Battery module configuration The battery module to which this embodiment is applied may basically be a conventional lithium-ion secondary battery or the like. Referring to Figures 1(A) and 1(B), the battery module 1 has a configuration in which a plurality of cells are stacked, each cell being formed with a positive electrode active material layer 3 coated on the surface of positive electrode foils (positive electrode foils) 2, 2a and a negative electrode active material layer 4 coated on the surface of negative electrode foils (negative electrode foils) 2, 2b facing each other with an electrolyte layer in between. Here, in the case of a liquid-based battery, the electrolyte layer is formed by sandwiching a separator 5 between each electrode foil and filling it with electrolyte, and in the case of an all-solid-state battery, it is a solid electrolyte layer (not shown). Furthermore, with the exception of electrode foils 2a and 2b on both sides of module 1, the positive electrode foil and negative electrode foil are formed as a bipolar electrode foil 2 by being bonded to the negative electrode foil and positive electrode foil of the adjacent cell, respectively. A positive electrode active material layer 3 and a negative electrode active material layer 4 are coated on both sides of each bipolar electrode foil 2 as described above to form a bipolar electrode body. In addition, the periphery of electrode foils 2, 2b, and 2a is covered with a primary seal 6, and spacers 7 may be interposed between each of the electrode foils 2, 2b, and 2a to maintain the distance between them, as shown in Figure 1(B). In the case of a liquid-based battery, the area between the electrode foils 2, 2a, and 2a is sealed with a heat-sealable sealing material, except for the edge on the side where the electrolyte injection port 10 is provided as shown in Figure 1(A) (the lower edge in Figure 1(A)), and is sealed with a sealing portion 6a (in the case of an all-solid-state battery, all edges of the periphery between the electrode foils 2, 2a, and 2b and the electrolyte layer (separator 5) may be sealed with the sealing material). In the above configuration, the sealing portion formed by the electrode foils, positive and negative electrode active material layers, electrolyte layer (separator 5 and electrolyte), and sealing material may be formed in a normal manner using materials commonly used in this field, except for the points described in particular below (see, for example, Patent Document 3). The electrolyte inlet 10 may be formed by any method (for example, the injection molding method described in Patent Document 4) after the edges other than the edge on which the inlet is provided are sealed with a seal portion.

[0023] In addition to the basic configuration of the battery module 1 as described above, in this embodiment, one of the bipolar electrode foils 2X stacked in module 1 is configured to have a portion that extends outward in the planar direction from the sealing portion 6a at the periphery of the battery module 1, as shown in Figures 1(A) and (B). The protruding portion of the bipolar electrode foil 2X may be provided on all sides where the sealing portion 6a is formed. With this configuration, since the bipolar electrode foil 2X is a metal foil with high thermal conductivity, cooling its protruding portion makes it possible to absorb heat from the inside of the battery module 1, thereby suppressing the deterioration of the battery module.

[0024] However, as explained in the section on the summary of the invention (see Figure 3(B)), if the intermediate bipolar electrode foil 2X of the battery module 1 protrudes from the seal portion 6a, attempting to form the entire seal portion 6a at once by heat welding of the sealing material by IR welding may result in areas around the bipolar electrode foil 2X where infrared rays do not reach, making it difficult to adequately seal the seal portion.

[0025] Therefore, in this embodiment, as will be described in detail later, the portion from the outermost electrode foil 2a of one end of the battery module 1 to the bipolar electrode foil 2X (the portion above the bipolar electrode foil 2X in Figure 1(B)) and the remaining portion of the battery module 1 (the portion below the bipolar electrode foil 2X in Figure 1(B)) are formed separately, and then these portions are superimposed and the bipolar electrode foil 2X and the sealing portion 6a of the remaining portion are heat-welded using a different method. For this reason, in the battery module according to this embodiment, as shown in Figure 1(B), a sealing member 6b and a heat conductive foil 12 are interposed in the strip-shaped region between the bipolar electrode foil 2X and the sealing portion 6a of the remaining portion.

[0026] Battery module manufacturing As described above, in the manufacturing method of the battery module in this embodiment, a first laminate, which is the portion from the outermost electrode foil 2a of one end of the battery module 1 to the bipolar electrode foil 2X, as schematically shown in Figures 2(A) and (B), and a second laminate, which is the portion from the electrolyte layer (separator 5) facing the bipolar electrode foil 2X to the other outermost electrode foil 2b of the battery module 1, as schematically shown in Figure 2(C), are manufactured separately. Here, the process of laminating the electrode body and the electrolyte layer in the first laminate and the second laminate may be carried out in a normal manner, and the process of forming the seal portions 6a_1 and 6a_2 by heat welding of the sealing member at the periphery of the electrode foil and the electrolyte layer may be carried out by a normal IR welding method. In this case, the bipolar electrode foil 2X of the first laminate may be formed to extend outward in the planar direction from the seal portion 6a_1 at all edges, except for the edge where the liquid injection port will be provided later, as shown in the figure. Furthermore, as shown in the figure, a strip of sealing material 6b is heat-welded to the outer surface (lower surface in the figure) of the bipolar electrode foil 2X in the region where the surface 6d (upper surface in Figure 2(C)) of the seal portion 6a_2 will come into contact with the second laminate, and a foil (thermal conductive foil 12) made of a material with high thermal conductivity is then heat-welded to that surface. The welding of the sealing material 6b and the thermal conductive foil 12 in this strip-shaped region may be achieved by any method, such as irradiating with infrared light from below in the figure.

[0027] Subsequently, as shown by the dotted arrow c in Figures 2(B) and (C), the first laminate and the second laminate are superimposed on each other (as shown in Figure 1(B)) so that the heat conductive foil 12 of the first laminate and the surface 6d of the sealing portion 6a_2 of the second laminate come into contact, and the active material layer 3 on the outer surface of the bipolar electrode foil 2X of the first laminate and the separator 5 of the second laminate face each other, and the heat conductive foil 12 is heated at this point. Heating of the heat conductive foil 12 can be achieved by contacting the heat conductive foil 12 with a high-temperature member 20, as shown in Figure 2(D), or by passing an electric current through the heat conductive foil 12 to generate Joule heat.

[0028] As a result, as shown in Figure 2(D), heat H is conducted along the heat conductive foil 12, the sealing material on the surface 6d of the sealing portion 6a_2 in contact with the heat conductive foil 12 melts and is heat-welded to the heat conductive foil 12, and thus both sides of the bipolar electrode foil 2X and the sealing portion 6a are sealed. In other words, the bipolar electrode foil in the middle of the battery module protrudes through the sealing portion in the planar direction, and the region on the electrolyte layer side can be reliably sealed to the outside by the sealing member. In the case of a liquid-based battery, an injection port 10 is formed at the edge where no sealing portion is formed, and the electrolyte is injected from there.

[0029] Thus, according to this embodiment, in order to cool the inner cell in a battery module in which multiple cells are stacked, the inner bipolar electrode foil is made to protrude outward in the planar direction from the seal portion that seals the electrolyte layer at the periphery of the cell, and the protruding portion is cooled, and the portion through which the bipolar electrode foil penetrates the seal portion can be reliably sealed with a sealing member.

[0030] While the above description has been made in relation to embodiments of the present invention, it will be clear to those skilled in the art that many modifications and changes are readily possible, and that the present invention is not limited to the embodiments illustrated above, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A method for manufacturing a battery module in which a plurality of cells are stacked, each cell having a positive electrode active material layer coated on an electrode foil which is a positive electrode foil and a negative electrode active material layer coated on an electrode foil which is a negative electrode foil, facing each other with an electrolyte layer in between, wherein, except for the outermost electrode foil of one cell and the outermost electrode foil of the other cell, each of the positive electrode foils and negative electrode foils of the cells are integrated with the negative electrode foils and positive electrode foils of the adjacent cells to form a bipolar electrode foil, the plurality of cells are connected in series, and a seal portion is formed in which the region between the outermost electrode foil of one cell and the outermost electrode foil of the battery module is sealed with a heat-sealable seal material at the periphery of the electrode foils and the electrolyte layer, The first laminate is constructed by laminating electrode foils coated with the positive and negative electrode active material layers and the electrolyte layer from one outermost electrode foil of the battery module to one bipolar electrode foil, sealing the periphery of the region between one outermost electrode foil of the battery module and the one bipolar electrode foil with the sealing material to form a part of the sealed portion, wherein the one bipolar electrode foil protrudes outward from the sealed portion of the sealing material in at least one planar direction of the one bipolar electrode foil, heat-sealing the sealing material to a strip-shaped region on the outer surface of the one bipolar electrode foil where the sealed portion will be located, and further heat-sealing a heat-conducting foil to the outside thereof. The process involves laminating the electrode foil coated with the positive and negative electrode active material layers and the electrolyte layer from the outermost electrode foil of the other battery module to the electrolyte layer facing the first bipolar electrode foil, sealing the periphery of the region between the outermost electrode foil of the other battery module and the first electrolyte layer with the sealing material to form another part of the sealed portion and thereby constructing a second laminate, A step of superimposing the first laminate and the second laminate such that the heat conductive foil of the first laminate contacts the surface of another part of the sealing portion of the second laminate, A step of heating the heat conductive foil to heat-weld the heat conductive foil and the sealing material in the strip-shaped region of the second laminate. A method that includes this.

2. The method according to claim 1, wherein the one bipolar electrode foil is the electrode foil of two cells in the middle of the battery module.

3. A method according to claim 1, wherein the cell is a liquid-type battery cell and the electrolyte layer is a separator that is immersed in an electrolyte.

4. The method according to claim 3, wherein the one bipolar electrode foil protrudes outward from the sealing portion of the sealing material in all other planar directions except the direction in which the electrolyte inlet is formed.

5. A battery module comprising multiple stacked cells, each having a positive electrode active material layer coated on an electrode foil (positive electrode foil) and a negative electrode active material layer coated on an electrode foil (negative electrode foil), facing each other with an electrolyte layer in between, wherein, excluding the outermost electrode foil of one cell and the outermost electrode foil of the other cell, each of the positive electrode foils and negative electrode foils of the cells are integrated with the negative electrode foil and positive electrode foil of the adjacent cell, forming a bipolar electrode foil, the multiple cells being connected in series, and a seal portion formed in the battery module that seals the region between the outermost electrode foil of one cell and the outermost electrode foil of the other cell with a heat-sealable seal material at the periphery of the electrode foil and the electrolyte layer, A battery module in which one of the bipolar electrode foils has a portion that protrudes in the planar direction from the sealing portion, and the sealing portion on one side of the one bipolar electrode foil is welded via a thermal conductive foil.

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