Manufacturing method of power storage device

Abstract

To suppress deterioration of a volumetric efficiency of a cell 10.SOLUTION: A manufacturing method is a manufacturing method of a cell 10. The cell 10 includes an electrode body and an exterior body in which the electrode body is enclosed. The exterior body is formed by using a laminate film including at least a resin layer and includes a seal portion in which a periphery edge of the exterior body is welded. The manufacturing method includes a heating step (step S11) of heating a bent portion of a portion to be bent of the seal portion, a bending step (steps S12 and S13) of bending the seal portion at the bent portion, and a cooling step (step S14) of cooling the bent portion. A temperature at which the bent portion is heated in the heating step is a predetermined first temperature equal to or higher than a glass transition point Tg or a melting point Tm of the resin layer. The temperature at which the bent portion is cooled in the cooling step is a predetermined second temperature equal to or lower than the glass transition point Tg or the melting point Tm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing an electricity storage device. [Background technology]

[0002] Conventionally, there has been a method for manufacturing a laminated battery that includes a first step of contacting a metal round wire with a portion of one surface of the peripheral edge of the exterior body, and a second step of bending the peripheral edge of the exterior body toward one surface while heating the metal round wire and using the metal round wire as a guide (see, for example, Patent Document 1). This allows the exterior body to be folded while suppressing heat damage to the power generating element. This reduces the width of the laminated battery, allowing more laminated batteries to be fitted in a smaller space. As a result, the volumetric efficiency of the energy storage device can be improved. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-175295 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the manufacturing method of Patent Document 1, springback occurs at the folded portion of the laminate depending on the temperature when the periphery of the exterior body is heated and the temperature after the folding process, which may result in a deterioration in the volumetric efficiency of the electricity storage device.

[0005] This disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing an electricity storage device that can suppress deterioration in the volumetric efficiency of the electricity storage device. [Means for solving the problem]

[0006] The manufacturing method according to this disclosure is a method for manufacturing an electricity storage device. The electricity storage device includes an electrode assembly and an exterior body in which the electrode assembly is encapsulated. The exterior body is made of a laminate film including at least a resin layer, and has a seal portion where the periphery of the exterior body is welded. The manufacturing method includes a heating step of heating a folding portion where the seal portion is folded, a folding step of folding the seal portion at the folding portion, and a cooling step of cooling the folding portion. The temperature to which the folding portion is heated in the heating step is a predetermined first temperature that is equal to or higher than the glass transition point Tg or melting point Tm of the resin layer. The temperature to which the folding portion is cooled in the cooling step is a predetermined second temperature that is equal to or lower than the glass transition point Tg or melting point Tm.

[0007] According to this configuration, the folded portion of the sealing portion of the exterior body is heated to a predetermined first temperature equal to or higher than the glass transition temperature Tg or melting temperature Tm of the resin layer, then folded, and cooled to a predetermined second temperature equal to or lower than the glass transition temperature Tg or melting temperature Tm. This makes it possible to reduce springback at the folded portion. As a result, it is possible to provide a manufacturing method for an energy storage device that can suppress deterioration in the volumetric efficiency of the energy storage device. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are diagrams showing an outline of the shape of a cell manufactured by the manufacturing method of this embodiment. [Figure 2] FIG. 1 is a first diagram for explaining the method for manufacturing the cell according to this embodiment. [Figure 3] FIG. 2 is a second diagram for explaining the method for manufacturing the cell according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0010] FIG. 1 is a diagram showing the outline of the shape of a cell 10 manufactured by the manufacturing method of this embodiment. FIG. 1(A) is a plan view of the cell 10. FIG. 1(B) is a cross-sectional view of the cell 10 taken along the line AA. Referring to FIG. 1, the cell 10 is a secondary battery, and in this embodiment, it is a lithium-ion battery. However, the present invention is not limited to this, and the cell 10 may also be a nickel-metal hydride battery or an all-solid-state battery. Two or more cells 10 are combined to form a battery pack.

[0011] The cell 10 includes an electrode assembly 11 and an outer casing 14. The cell 10 also includes a positive electrode tab and a negative electrode tab, which are not shown in FIG. 1 . The electrode assembly 11 is housed in the outer casing 14. The electrode assembly 11 has multiple positive electrodes, multiple negative electrodes, and multiple separators. The positive electrodes and negative electrodes are alternately stacked. The positive electrode has a positive electrode active material that occludes lithium (Li) ions. The negative electrode has a negative electrode active material that occludes lithium ions. The separator is disposed between the positive electrode and the negative electrode. The separator is made of an insulating material that allows lithium ions to pass through. Although not shown, in the case of a lithium-ion battery, an electrolyte is also enclosed inside the outer casing 14 along with the electrode assembly 11.

[0012] The exterior body 14 is composed of a laminate film 12 on the first surface side and a laminate film 13 on the second surface side. The laminate films 12, 13 have a film base (e.g., aluminum foil, stainless steel foil) made of metal (e.g., aluminum (Al) or stainless steel) and resin layers (e.g., a polypropylene (PP) layer, a biaxially oriented nylon film layer) formed on both sides of the film base. The laminate films 12, 13 are welded at the seal portion 15 by heating the resin layers on their respective peripheries. In other words, the seal portion 15 is formed on the periphery of the exterior body 14.

[0013] Conventionally, there has been a method for manufacturing a laminated cell 10 that includes a first step of contacting a metal round wire with a portion of one surface of the peripheral edge of the outer casing 14, and a second step of bending the peripheral edge of the outer casing 14 toward one surface while heating the metal round wire, using the metal round wire as a guide. This reduces the width of the laminated cell 10, allowing more laminated cells 10 to be fitted in a smaller space. As a result, the volumetric efficiency of an energy storage device, which is a battery pack formed by combining multiple cells 10, can be improved. However, depending on the temperature during heating of the peripheral portion of the outer casing 14 and the temperature after the bending step, springback of the folded portion of the laminate can occur. This raises concerns about a deterioration in the volumetric efficiency of the energy storage device.

[0014] Therefore, the manufacturing method of cell 10 includes a heating step of heating the folding portion where seal portion 15 is folded, a folding step of folding seal portion 15 at the folding portion, and a cooling step of cooling the folding portion. The temperature to which the folding portion is heated in the heating step is set to a predetermined first temperature (e.g., 160°C) that is equal to or higher than the glass transition point Tg (e.g., about -20°C if the resin is polypropylene) or the melting point Tm (e.g., about 140°C if the resin is polypropylene) of the resin layer of laminate films 12, 13. The temperature to which the folding portion is cooled in the cooling step is set to a predetermined second temperature (e.g., 100°C) that is equal to or lower than the glass transition point Tg or the melting point Tm.

[0015] As a result, the folded portion of the seal portion 15 of the exterior body 14 is heated to a predetermined first temperature equal to or higher than the glass transition temperature Tg or melting temperature Tm of the resin layer of the laminate films 12 and 13, then folded, and after folding, cooled to a predetermined second temperature equal to or lower than the glass transition temperature Tg or melting temperature Tm. This makes it difficult for springback to occur at the folded portion. As a result, deterioration in the volumetric efficiency of the electricity storage device can be suppressed.

[0016] Fig. 2 is a first diagram for explaining the manufacturing method of the cell 10 of this embodiment. Fig. 3 is a second diagram for explaining the manufacturing method of the cell 10 of this embodiment. With reference to Figs. 2 and 3, as shown in Fig. 2(A), manufacturing apparatus 100 for cell 10 includes a heating device 120, a bending device 130, a cooling device 140, and a control device 110.

[0017] The control device 110 includes a CPU and a memory. The memory stores programs such as a predetermined program for manufacturing the cell 10 and various data. The CPU executes predetermined processing for manufacturing the cell 10 in accordance with the program stored in the memory.

[0018] The heating device 120 is controlled by the control device 110 to heat at least the folded portion 16 shown in FIG. 3(A) and other figures of the laminate films 12 and 13 in the seal portion 15 of the cell 10. The CPU of the control device 110 controls the heating device 120 to execute a process of heating the folded portion 16 at a predetermined first temperature, as shown in FIG. 3(A) (step S11 in FIG. 2(B)). The predetermined first temperature is a temperature determined in advance at the time of design that is equal to or higher than the glass transition temperature Tg or melting temperature Tm of the resin layer of the laminate films 12 and 13. Note that, if the film base of the laminate films 12 and 13 is aluminum, the predetermined first temperature is a temperature lower than the melting point of the aluminum (660°C for pure aluminum).

[0019] The folding device 130 is controlled by the control device 110 to fold the seal portion 15 of the cell 10 at the folding portion 16. As shown in Figures 3(A) and 3(B), the CPU of the control device 110 controls the folding device 130 to execute a step of abutting the pressing plate 131 among the steps of folding the seal portion 15 at the folding portion 16 (step S12 in Figure 2(B)). Details of this folding step are described in JP 2019-200973 A.

[0020] As shown in FIG. 3(A), the bending device 130 includes a pressure plate 131. FIG. 3(A) shows a cross section of the pressure plate 131. The length of the pressure plate 131 in the direction from the back to the front of the paper is equal to or greater than the length of the cells 10 in the same direction. The cross section of the portion of the pressure plate 131 that abuts against the cells 10 in the same direction has the same shape as the cross section shown in FIG. 3(A). After the bending portion 16 is heated to a predetermined first temperature, in the step of abutting the pressure plate, as shown in FIGS. 3(A) and 3(B), the pressure plate 131 is moved in the direction indicated by arrow a and abuts against the bending portion 16.

[0021] Next, the CPU of the control device 110 controls the folding device 130 to execute the process of folding the seal portion 15 to form the folding portion 16, as shown in Figures 3(C) to 3(E) (step S13 in Figure 2(B)).

[0022] As shown in FIG. 3(C), the bending device 130 further includes a pressing unit 132. FIG. 3(C) shows a cross section of the pressing unit 132. The pressing unit 132 has an inclined surface 133 that slides against the sealing unit 15, and a clamping surface 134. The length of the pressing unit 132 in the direction from the back to the front of the paper is equal to or greater than the length of the cell 10 in the same direction, and is approximately the same as the length of the pressing plate 131 in the same direction. The cross section of the portion of the pressing unit 132 that abuts against the cell 10 in the same direction has the same shape as the cross section shown in FIG. 3(C).

[0023] In the step of forming the folded portion, as shown in Fig. 3(C), the pressing portion 132 is moved in the direction indicated by the arrow b. Next, as shown in Fig. 3(D), the inclined surface 133 is slid against the sealed portion 15. As a result, the sealed portion 15 is folded at the folding portion 16. Then, as shown in Fig. 3(E), the pressing portion 132 is moved in the direction indicated by the arrow c, so that the sealed portion 15 is sandwiched between the sandwiching surface 134 and the presser plate 131. As a result, the sealed portion 15 is folded until it is at a substantially right angle (90 degrees) to the bottom surface of the cell 10 (the outer surface of the laminate film 13).

[0024] The cooling device 140 is controlled by the control device 110 to cool at least the folded portion 16 shown in FIG. 3(E) of the laminate films 12, 13 in the seal portion 15 of the cell 10. The CPU of the control device 110 controls the heating device 120 to execute a step of cooling the folded portion 16 at a predetermined second temperature as shown in FIG. 3(E) (step S14 in FIG. 2(B)). The predetermined second temperature is a temperature determined in advance at the time of design that is equal to or lower than the glass transition temperature Tg or melting temperature Tm of the resin layer of the laminate films 12, 13.

[0025] When the heating and cooling processes are not performed, springback occurs by 15 degrees after bending the bent portion 16 to 90 degrees, resulting in a final bending angle of 75 degrees. On the other hand, when the heating and cooling processes are performed as in this disclosure, springback occurs by 5 degrees after bending the bent portion 16 to 90 degrees, resulting in a final bending angle of 85 degrees. Thus, according to this disclosure, springback of the bent portion 16 can be made less likely to occur.

[0026] [Variations] (1) In the above-described embodiment, as shown in Fig. 2(A), the cell 10 is depicted as being transferred between the devices in sequence. However, this is not limiting, and the cell 10 may be configured to be left unmoved and have predetermined processing performed by each device.

[0027] (2) As shown in FIG. 3(E), the cooling device 140 can cool the bent portion 16 of the sealing portion 15 in a state where the sealing portion 15 is clamped between the clamping surface 134 of the pressing portion 132 and the pressure plate 131, or in a state where the sealing portion 15 is not clamped between the clamping surface 134 and the pressure plate 131.

[0028] (3) In the above-described embodiment, the welding process of welding the laminate films 12 and 13 to form the seal portion 15 is performed independently of the heating process. However, this is not limiting, and the heating process may be performed together with the welding process.

[0029] [summary] The manufacturing method disclosed herein is a method for manufacturing a cell 10. As shown in FIG. 1, the cell 10 includes an electrode assembly 11 and an exterior body 14 in which the electrode assembly 11 is sealed. As shown in FIG. 1, the exterior body 14 is composed of laminate films 12 and 13 including at least a resin layer, and has a seal portion 15 where the periphery of the exterior body 14 is welded. As shown in FIGS. 2 and 3, the manufacturing method includes a heating step (step S11) of heating a folding portion 16 where the sealing portion 15 is folded, a folding step (steps S12 and S13) of folding the sealing portion 15 at the folding portion 16, and a cooling step (step S14) of cooling the folding portion 16. As shown in FIG. 2, the temperature to which the folding portion 16 is heated in the heating step is a predetermined first temperature that is equal to or higher than the glass transition temperature Tg or melting temperature Tm of the resin layer. As shown in FIG. 2, the temperature to which the bent portion 16 is cooled in the cooling step is a predetermined second temperature that is equal to or lower than the glass transition point Tg or the melting point Tm.

[0030] As a result, the folded portion 16 of the seal portion 15 of the exterior body 14 is heated to a predetermined first temperature equal to or higher than the glass transition point Tg or melting point Tm of the resin layer, then folded, and after folding, cooled to a predetermined second temperature equal to or lower than the glass transition point Tg or melting point Tm. This makes it difficult for the folded portion 16 to spring back, thereby suppressing a deterioration in the volumetric efficiency of the cell 10.

[0031] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0032] 10 cell, 11 electrode body, 12, 13 laminate film, 14 exterior body, 15 sealing section, 16 bending section, 100 manufacturing device, 110 control device, 120 heating device, 130 bending device, 131 pressure plate, 132 pressing section, 133 inclined surface, 134 clamping surface, 140 cooling device.

Claims

[Claim 1] A method for manufacturing an electricity storage device, comprising: The power storage device includes an electrode body and an exterior body in which the electrode body is enclosed, the exterior body is made of a laminate film including at least a resin layer, and has a seal portion where the periphery of the exterior body is welded; The manufacturing method includes: a heating step of heating a folded portion of the sealing portion; a folding step of folding the seal portion at the folding portion; a cooling step of cooling the bent portion, a temperature to which the bent portion is heated in the heating step is a predetermined first temperature that is equal to or higher than a glass transition temperature Tg or a melting point Tm of the resin layer, The method for manufacturing an electricity storage device, wherein the temperature to which the bent portion is cooled in the cooling step is a predetermined second temperature that is equal to or lower than the glass transition point Tg or the melting point Tm.

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