Manufacturing method of energy storage module

Abstract

To improve the non-defective rate of a power storage module.SOLUTION: A manufacturing method of a power storage unit includes an arrangement step S1, a preheating step S4, a welding step S6, and a stacking step S10. In the preheating step S4, a pre-welding resin portion placed in the arrangement step S1 is pressed against the main surface of a current collector with preheating pressure, and the resin temperature which is the temperature of the resin portion is maintained at a softening point or higher and lower than a melting point to preheat the resin portion. In the welding step S6, the preheated resin portion is pressed against the current collector with the welding pressure and the temperature of the resin portion is kept the melting point or higher to weld the resin portion to the main surface to manufacture an electrode unit. In the stacking step S10, the power storage module is manufactured by stacking the electrode units that have undergone the welding step S6. The preheating pressure is less than the welding pressure.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] The electricity storage module described in Patent Document 1 includes a plurality of electrode units. The electrode units include a current collector that is a metal foil, an active material layer provided on the main surface of the current collector, and a resin part that is welded to the main surface of the current collector so as to surround the active material layer. The resin part is interposed between adjacent electrode units to ensure insulation between the adjacent electrode units. The resin part is welded to the current collector by placing the resin part on the main surface of the current collector and welding the placed resin part. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-107486 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the resin part is deformed by thermal contraction during cooling after welding. The thermal contraction of the resin part causes deformation of the current collector to which the resin part is welded. The degree of thermal contraction of the resin part varies depending on the residual stress in the resin part before it is welded to the current collector. Therefore, variations in the residual stress in the resin part cause unintended deformation of the resin part, such as bending or undulation. The current collector used in the electrode unit is generally a thin metal foil. Therefore, such unintended deformation may damage the current collector, which is a metal foil. As a result, the yield rate of the energy storage module may decrease. [Means for solving the problem]

[0005] A manufacturing method for an electricity storage module that solves the above-mentioned problems is a manufacturing method for an electricity storage module including a plurality of electrode units each including a current collector which is a metal foil, an active material layer provided on a main surface of the current collector, and a resin part welded to surround the active material layer on the main surface, the manufacturing method including: an arrangement step of arranging the resin part before welding on the main surface; a preheating step of preheating the resin part by pressing the arranged resin part against the current collector with a preheating pressure while maintaining a temperature of the resin part equal to or higher than the softening point of the resin part and lower than the melting point of the resin part; a welding step of welding the resin part to the main surface by pressing the preheated resin part against the current collector with a welding pressure while maintaining a temperature of the resin part equal to or higher than the melting point, thereby manufacturing the electrode unit; and a stacking step of stacking the electrode units that have undergone the welding step to manufacture the electricity storage module, wherein the preheating pressure is smaller than the welding pressure.

[0006] According to this method, the electrode unit is manufactured through an arrangement step, a preheating step, and a welding step, and a plurality of such electrode units are stacked through a stacking step to manufacture an electricity storage module.

[0007] In this configuration, a preheating step is performed before the resin portion is welded to the main surface of the current collector in the welding step. In the preheating step, the temperature of the resin portion is maintained at or above the softening point of the resin portion and below the melting point of the resin portion, thereby suppressing welding of the resin portion to the current collector and promoting softening of the resin portion. The softening of the resin portion relieves residual stress in the resin portion. This reduces variation in residual stress in the resin portion prior to the welding step.

[0008] On the other hand, as the residual stress is relaxed, unintended deformation of the resin part, such as bending or swell, may occur. Therefore, in the preheating process, the resin part is pressed against the main surface of the current collector by preheating pressure. This makes it possible to restrict the resin part from deforming in a direction perpendicular to the main surface of the current collector when the residual stress is relaxed in the preheating process. Furthermore, by making the preheating pressure smaller than the welding pressure, the relaxation of the residual stress can be promoted. Therefore, unintended deformation of the resin part due to the variation in residual stress can be suppressed, and damage to the current collector, which is a metal foil, can be suppressed. This makes it possible to improve the yield rate of the energy storage module.

[0009] In the manufacturing method of the energy storage module, the main surfaces include a first main surface and a second main surface located opposite to the first main surface in a thickness direction of the current collector, the resin parts include a first resin part welded to the first main surface and a second resin part welded to the second main surface, the arranging step includes a first arranging step of arranging the first resin part before welding on the first main surface and a second arranging step of arranging the second resin part before welding on the second main surface, the preheating step includes sandwiching and pressing the arranged first resin part and the arranged second resin part from the first main surface side and the second main surface side to perform the preheating together, and the welding step includes sandwiching and pressing the first resin part and the second resin part which have been preheated from the first main surface side and the second main surface side to perform the welding together, thereby welding the first resin part to the first main surface and the second resin part to the second main surface.

[0010] According to this, the resin portion is welded to both the first and second main surfaces through the preheating and welding processes. This makes it easier for the force on the current collector caused by thermal contraction of the resin portion to act evenly on the current collector from both main surfaces, compared to when one resin portion is welded to one of the main surfaces at a time. This makes it possible to suppress unintended deformation of the resin portion and to suppress damage to the current collector, which is a metal foil. This makes it possible to further improve the yield rate of the energy storage module.

[0011] In the above-mentioned method for manufacturing the energy storage module, in the arrangement process, the resin part before welding may be arranged on the main surface such that a portion of the resin part extends beyond the peripheral edge of the main surface, and in the stacking process, the portions of the resin parts of each of the stacked electrode units that extend beyond the peripheral edge of the main surface of the current collector may be integrated.

[0012] According to this, in the electrode units that are adjacent to each other due to stacking, the portions of the resin parts that protrude from the periphery of the main surface are integrated. Here, the portions of the resin parts that protrude from the periphery of the main surface are not welded to the main surface of the current collector. Therefore, the resin parts are integrated at a portion different from the portion where the resin parts are welded to the main surface in the welding process. This makes it possible to reduce the effect of the integration on the portions of the resin parts that are welded to the main surface. Therefore, it is possible to suppress unintended deformation of the resin parts during integration and further suppress damage to the current collector, which is a metal foil. Therefore, it is possible to further improve the yield rate of the energy storage module. Effect of the Invention

[0013] According to the present invention, the yield rate of energy storage modules can be improved. [Brief description of the drawings]

[0014] [Figure 1] 4 is a plan view of an electrode unit included in the power storage module. FIG. [Diagram 2] 4 is a side view of an electrode unit included in the power storage module. FIG. [Diagram 3] FIG. 2 is a diagram for explaining the configuration of an energy storage module manufacturing apparatus. [Figure 4] 4 is a cross-sectional view of FIG. 3 along line 4-4. [Diagram 5] 11A to 11C are diagrams for explaining a manufacturing method of the energy storage module. [Figure 6] FIG. 2A is a diagram for explaining a change in resin temperature in each process, and FIG. 2B is a diagram for explaining a change in resin pressure in each process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Configuration> An embodiment of a method for manufacturing an electricity storage module will be described below. The electricity storage module includes a plurality of electrode units.

[0016] As shown in Figs. 1 and 2, the electrode unit 10 includes an electrode plate 11, a first resin part 20 as a resin part, and a second resin part 30 as a resin part. The electrode plate 11 is a bipolar electrode. The electrode plate 11 includes a current collector 12, a first active material layer 16, and a second active material layer 17.

[0017] The current collector 12 is made of a metal foil. The current collector 12 is, for example, a copper foil, an aluminum foil, a titanium foil, or a nickel foil. From the viewpoint of ensuring mechanical strength, the current collector 12 may be a stainless steel foil (for example, SUS304, SUS316, SUS301, etc., as specified in JIS G 4305:2015). The current collector 12 may be an alloy foil of the above metals, or a plurality of the above metal foils integrated together. The surface of the current collector 12 may be subjected to a known plating process or surface treatment. The thickness of the current collector 12 is, for example, 1 μm or more and 100 μm or less, specifically, 5 μm or more and 70 μm or less. The shape of the current collector 12 is a rectangular sheet, specifically, a rectangular sheet. The electrode plate 11 is not limited to the above-mentioned form, and may be a simple stack of two metal foils.

[0018] The current collector 12 has a main surface 13. The main surface 13 is a surface perpendicular to the thickness direction of the current collector 12. The main surface 13 includes a first main surface 14 and a second main surface 15. The second main surface 15 is located opposite to the first main surface 14 in the thickness direction of the current collector 12.

[0019] The first active material layer 16 as an active material layer contains a positive electrode active material. The positive electrode active material can absorb and release charge carriers such as lithium ions. Examples of the positive electrode active material include, for example, composite oxides, metallic lithium, and sulfur. The first active material layer 16 may contain a conductive assistant, a binder, and other components as necessary. The first active material layer 16 is bonded integrally to the first main surface 14. The first active material layer 16 has a thickness of, for example, 2 to 150 μm. Examples of a method for bonding the first active material layer 16 to the first main surface 14 include known methods such as roll coating.

[0020] The first main surface 14 includes a first uncoated surface 14a. The first uncoated surface 14a is a region to which the first active material layer 16 is not bonded. The first uncoated surface 14a includes a first peripheral edge 14b that is the peripheral edge of the first main surface 14.

[0021] The second active material layer 17 as an active material layer includes a negative electrode active material. The negative electrode active material can absorb and release charge carriers such as lithium ions. Examples of the negative electrode active material include graphite, carbon, metal compounds, elements or compounds thereof that can be alloyed with lithium, and boron-added carbon. The second active material layer 17 may contain a conductive assistant, a binder, and other components as necessary. The second active material layer 17 has a thickness of, for example, 2 to 150 μm. The second active material layer 17 is integrally bonded to the second main surface 15. The second active material layer 17 has a thickness of, for example, 2 to 150 μm. The method for bonding the second active material layer 17 to the second main surface 15 includes a known method such as a roll coating method.

[0022] The second main surface 15 includes a second uncoated surface 15a. The second uncoated surface 15a is a region to which the second active material layer 17 is not bonded. The second uncoated surface 15a includes a second peripheral edge 15b that is the peripheral edge of the second main surface 15.

[0023] The first resin part 20 is formed in a frame shape. The first resin part 20 is formed in a rectangular shape. The first resin part 20 has four first side parts 21. Each of the first side parts 21 is formed in a quadrangular prism shape. Ends of the first side parts 21 are connected to each other. Each of the first side parts 21 faces one of the other first side parts 21.

[0024] The first resin portion 20 is welded to the first main surface 14. More specifically, the first resin portion 20 is welded to the first uncoated surface 14a. The first resin portion 20 is welded along the first periphery 14b. It can also be said that the first resin portion 20 is welded to the first main surface 14 so as to surround the first active material layer 16. A portion of the first resin portion 20 protrudes from the first periphery 14b around the entire periphery of the first periphery 14b in a direction away from the region where the first active material layer 16 is adhered.

[0025] The second resin part 30 is formed in a frame shape. The second resin part 30 is formed in a rectangular shape. The second resin part 30 has four second side parts 31. Each second side part 31 is formed in a quadrangular prism shape. Ends of the second side parts 31 are connected to each other. Each second side part 31 faces one of the other second side parts 31.

[0026] The second resin portion 30 is welded to the second main surface 15. More specifically, the second resin portion 30 is welded to the second uncoated surface 15a. The second resin portion 30 is welded along the second periphery 15b. It can also be said that the second resin portion 30 is welded to the second main surface 15 so as to surround the second active material layer 17. A portion of the second resin portion 30 protrudes from the second periphery 15b around the entire periphery of the second periphery 15b in a direction away from the region where the second active material layer 17 is adhered.

[0027] The first resin part 20 and the second resin part 30 are made of insulating resin. As the material of the first resin part 20 and the second resin part 30, various resin materials such as polyethylene (PE), polystyrene (PS), polypropylene (PP), ABS resin, and AS resin, or modified ones of these resin materials can be used.

[0028] The electrode units 10 configured in this manner are stacked via the resin parts 20, 30 to form a power storage module B. Of the resin parts 20, 30 of the stacked electrode units 10, the parts protruding from the peripheral edges 14b, 15b are integrated together, for example, by an adhesive member. As the adhesive member, for example, the resin material exemplified for the resin parts 20, 30 is used. The power storage module B of this embodiment is a bipolar type lithium ion storage battery. The power storage module B is used in batteries for various vehicles, such as forklifts, hybrid cars, and electric cars.

[0029] <Electricity storage module manufacturing equipment> Next, an example of an energy storage module manufacturing apparatus for manufacturing the energy storage module B will be described.

[0030] 3 and 4, the electricity storage module manufacturing apparatus 40 is an apparatus for manufacturing an electrode unit 10 by welding a first resin part 20 and a second resin part 30 to a current collector 12, and for manufacturing an electricity storage module B by stacking a plurality of the manufactured electrode units 10. The electricity storage module manufacturing apparatus 40 includes two pressing units 41, a heating part 42, a pressure sensor 43, a temperature sensor 44, and a control circuit 45.

[0031] The two pressing units 41 press the resin parts 20 and 30 toward the current collector 12. For ease of explanation, the direction in which the pressing units 41 press the resin parts 20 and 30 toward the current collector 12 will be referred to as the pressing direction. The pressing direction coincides with the stacking direction. The pressing direction also coincides with the thickness direction of the current collector 12.

[0032] In this embodiment, the two pressing units 41 press the first side portion 21 and the second side portion 31 of the resin portions 20, 30 toward the current collector 12, respectively. The two pressing units 41 are arranged spaced apart from each other in a direction perpendicular to the pressing direction. As a result, the first side portion 21 and the second side portion 31 pressed by one pressing unit 41 face each other, spaced apart in a direction perpendicular to the stacking direction, from the first side portion 21 and the second side portion 31 pressed by the other pressing unit 41. Each of the two pressing units 41 includes a first pressing portion 41a and a second pressing portion 41b.

[0033] The first pressing portion 41 a presses the first side portion 21 toward the current collector 12 . The second pressing portion 41b presses the second side portion 31 toward the current collector 12. The second pressing portion 41b is separated from the first pressing portion 41a in the pressing direction. The second pressing portion 41b overlaps with the first pressing portion 41a in a plan view from the pressing direction. As a result, the first pressing portion 41a and the second pressing portion 41b constituting the same pressing unit 41 form a pair with each other. Hereinafter, the pair of the first pressing portion 41a and the second pressing portion 41b may be collectively referred to as a pair of pressing portions 41a, 41b. The current collector 12 and the resin portions 20, 30 are disposed between the pair of pressing portions 41a, 41b. A heater wire (not shown) is disposed in each of the pressing portions 41a, 41b.

[0034] When the current collector 12 and the resin parts 20, 30 are disposed between the pair of pressing parts 41a, 41b, at least a part of the first pressing part 41a faces the first main surface 14 of the current collector 12 via the first resin part 20. At this time, at least a part of the second pressing part 41b faces the second main surface 15 of the current collector 12 via the second resin part 30. That is, the pair of pressing parts 41a, 41b are disposed facing each other so as to be able to press the current collector 12, the first resin part 20, and the second resin part 30. The pair of pressing parts 41a, 41b are configured to be relatively movable with respect to each other in the pressing direction. The pair of pressing parts 41a, 41b come into contact with the resin parts 20, 30 by approaching each other relatively via the current collector 12 and the resin parts 20, 30. After contacting the resin parts 20, 30, the pair of pressing parts 41a, 41b move relatively closer in the pressing direction, so that the first resin part 20 is pressed against the first peripheral edge 14b and the second resin part 30 is pressed against the second peripheral edge 15b. As a result, the pair of pressing parts 41a, 41b sandwich and press the first resin part 20 and the second resin part 30 from the first main surface 14 side and the second main surface 15 side toward the current collector 12. The pressing parts 41a, 41b may include a welding suppression part TF. The welding suppression part TF can be provided on the contact surface between each pressing part 41a, 41b and the resin parts 20, 30. This can suppress the resin parts 20, 30 from welding to the pressing parts 41a, 41b. The welding suppression part TF is, for example, a sheet-like member containing a fluororesin. The adhesion prevention portion TF may be formed by performing a surface treatment such as a fluororesin coating on the pressing portions 41a and 41b.

[0035] The heating unit 42 is configured to be able to heat the first resin part 20 and the second resin part 30. The heating unit 42 in this embodiment is of a pulse heater type that heats the first resin part 20 and the second resin part 30 by Joule heat generated when an electric current is passed through a heater wire provided in each of the pressing parts 41a, 41b. The heating unit 42 is configured integrally with each of the pressing parts 41a, 41b. Note that the specific embodiment and heating means of the heating unit 42 are not limited to this, and may be any of heating methods such as heating by an external heater, ultrasonic heating, and laser heating.

[0036] The pressure sensor 43 is a sensor capable of detecting the resin pressure P applied by the pressing unit 41 to the resin parts 20, 30. The pressure sensor 43 may be any specific embodiment such as a hydraulic sensor or a gauge sensor.

[0037] The temperature sensor 44 is a sensor capable of detecting the resin temperature T, which is the temperature of the resin parts 20, 30. The temperature sensor 44 may be any type, such as a thermistor, a thermocouple, a resistance thermometer, or a radiation thermometer.

[0038] The control circuit 45 includes a processor and a storage unit. The processor may be, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The storage unit includes a random access memory (RAM) and a read only memory (ROM). The storage unit stores program codes or instructions configured to cause the processor to execute processes. The storage unit, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The control circuit 45 may be configured by a hardware circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control circuit 45, which is a processing circuit, may include one or more processors operating according to a computer program, one or more hardware circuits such as an ASIC or an FPGA, or a combination thereof.

[0039] The control circuit 45 is configured to be able to acquire the resin pressure P from the pressure sensor 43. The control circuit 45 is also configured to be able to acquire the resin temperature T from the temperature sensor 44. The control circuit 45 controls the pressing unit 41 and the heating section 42 so that the acquired resin pressure P and resin temperature T become the respective target values.

[0040] <Manufacturing method for energy storage module> Next, each step of the method for manufacturing the electricity storage module B using the electricity storage module manufacturing apparatus 40 will be described.

[0041] 5 and 6, the manufacturing method of the energy storage module B includes an arrangement step S1, a contact step S2, a first transition step S3, a preheating step S4, a second transition step S5, a welding step S6, a cooling step S7, a determination step S8, a change step S9, and a stacking step S10. Each of the steps S1 to S10 is performed, for example, on a workbench (not shown). In Figs. 6(a) and (b), H1 indicates the resin temperature T and the resin pressure P in the steps S1 to S7, respectively.

[0042] In the arranging step S1, the resin parts 20, 30 before welding are arranged on the main surface 13 of the current collector 12. More specifically, the first resin part 20 is arranged on the first main surface 14 (more specifically, the first uncoated surface 14a). Also, the second resin part 30 is arranged on the second main surface 15 (more specifically, the second uncoated surface 15a). Therefore, it can be said that the arranging step S1 includes a first arranging step of arranging the first resin part 20 on the first main surface 14. Also, it can be said that the arranging step S1 includes a second arranging step of arranging the second resin part 30 on the second main surface 15.

[0043] In the arrangement step S1, the resin parts 20, 30 are arranged on the main surfaces 13, 14 so that a part of each of them extends beyond the periphery 14b, 15b of the main surfaces 14, 15. In detail, the first resin part 20 is arranged so that a part of each of the first resin part 20 extends beyond the first periphery 14b. Moreover, the second resin part 30 is arranged so that a part of each of the second resin part 30 extends beyond the second periphery 15b. At this time, the thickness direction of the current collector 12 is parallel to the pressing direction. It is assumed that the electrode plate 11 has been prepared in advance by a known method. Moreover, the specific arrangement method is arbitrary.

[0044] Next, proceeding to the contact step S2, the control circuit 45 brings the two pressing units 41 into contact with the first resin part 20 and the second resin part 30, respectively. In detail, the control circuit 45 brings the first pressing part 41a into contact with the first resin part 20 from the first main surface 14 side. Also, the control circuit 45 brings the second pressing part 41b into contact with the second resin part 30 from the second main surface 15 side. As a result, the two pressing units 41 sandwich the first resin part 20 and the second resin part 30 arranged in the arrangement step S1 on the first main surface 14 side and the second main surface 15 side. At this time, each pressing part 41a, 41b is in direct contact with the resin parts 20, 30. In other words, no member other than the resin parts 20, 30 and the current collector 12 to which the resin parts 20, 30 are welded is interposed between the pair of pressing parts 41a, 41b.

[0045] The control circuit 45 brings the pressing parts 41a, 41b closer to the side parts 21, 31 of the resin parts 20, 30. When the resin pressure P becomes equal to or greater than the contact pressure Pc, the control circuit 45 determines that the pressing parts 41a, 41b are in contact with the side parts 21, 31 of the resin parts 20, 30. The contact pressure Pc can be set arbitrarily according to the material of the current collector 12 and the resin parts 20, 30, for example. When the resin pressure P does not become equal to or greater than the contact pressure Pc during a predetermined confirmation period, the control circuit 45 determines that poor contact has occurred between the pressing parts 41a, 41b and the resin parts 20, 30. When it is determined that poor contact has occurred, the control circuit 45 may perform a process such as notifying the surroundings of the poor contact by, for example, a notification lamp. Possible causes of such poor contact include, for example, deformation of the resin parts 20, 30, or misalignment of the resin parts 20, 30 with respect to the current collector 12.

[0046] Next, proceeding to a first transition step S3, the control circuit 45 uses the pressing unit 41 to press the first side portion 21 of the first resin portion 20 and the second side portion 31 of the second resin portion 30 toward the respective main surfaces 14, 15 so that the resin pressure P changes from the contact pressure Pc to the preheating pressure P1. The preheating pressure P1 is arbitrary as long as it can regulate deformation in the thickness direction due to softening of the resin portions 20, 30. The preheating pressure P1 may be obtained by a test or the like, or may be obtained by a simulation or the like.

[0047] When the control circuit 45 determines that the resin pressure P has been increased to the preheating pressure P1, it heats the first side 21 of the first resin part 20 and the second side 31 of the second resin part 30 using the heating part 42 so that the resin temperature T becomes the first temperature T1. The first temperature T1 is equal to or higher than the softening point Tr of the resin parts 20, 30 and lower than the melting point Tm of the resin parts 20, 30. Hereinafter, for convenience of explanation, the softening point Tr of the resin parts 20, 30 is simply referred to as the softening point Tr, and the melting point Tm of the resin parts 20, 30 is simply referred to as the melting point Tm. The softening point Tr is the lowest temperature at which the resin parts 20, 30 soften. The softening point Tr in this embodiment is the glass transition point of the resin parts 20, 30. Depending on the characteristics of the material used for the resin parts 20, 30, the load deflection temperature, the Vicat softening temperature, or the like may be adopted as the softening point Tr. Furthermore, when the resin parts 20, 30 are made of an amorphous resin, the softening point Tr may be a temperature that is a predetermined temperature lower than the glass transition point. The predetermined temperature depends on the material of the resin parts 20, 30, but is, for example, 10° C. to 40° C., and more preferably 20° C. to 30° C. For ease of explanation, the state in which the resin parts 20, 30 are softened may be referred to as the softened state below.

[0048] Next, the process proceeds to a preheating step S4, where the control circuit 45 uses the heating unit 42 to heat the sides 21, 31 of the resin parts 20, 30 so that the resin temperature T is maintained at or above the softening point Tr and below the melting point Tm. In this embodiment, during the preheating step S4, the resin temperature T is maintained constant at a first temperature T1 within a tolerance range. The tolerance can be set arbitrarily.

[0049] The preheating period tr during which the preheating step S4 continues may be, for example, a period required for the temperatures of the interface of the first resin part 20 in contact with the first peripheral edge 14b and the interface of the second resin part 30 in contact with the second peripheral edge 15b to reach the softening point Tr or more. Note that the preheating period tr is not limited to this and can be set arbitrarily.

[0050] When the resin parts 20, 30 have an acid-modified group such as acid-modified polyethylene, the first temperature T1 and the preheating period tr are preferably the temperature and period required to activate the acid-modified group. The first temperature T1 depends on the material of the resin parts 20, 30, but is, for example, in the range of 80°C to 120°C or 90°C to 110°C. The first temperature T1 and the preheating period tr may be determined by testing or the like depending on the material and size of the resin parts 20, 30.

[0051] Next, proceeding to a second transition step S5, the control circuit 45 uses the pressing unit 41 to press the first side portion 21 of the first resin portion 20 and the second side portion 31 of the second resin portion 30 toward the respective main surfaces 14, 15 so that the resin pressure P changes from the preheating pressure P1 to the welding pressure P2. The welding pressure P2 is a pressure higher than the preheating pressure P1. The welding pressure P2 may be any pressure as long as it allows welding of the resin portions 20, 30. The welding pressure P2 may be obtained by a test or the like, or may be obtained by a simulation or the like.

[0052] When the control circuit 45 determines that the resin pressure P has been increased to the welding pressure P2, it uses the heating unit 42 to heat the first side portion 21 of the first resin portion 20 and the second side portion 31 of the second resin portion 30 so that the resin temperature T changes from the first temperature T1 to the second temperature T2. The second temperature T2 is equal to or higher than the melting point Tm. Note that the second temperature T2 may be, for example, any temperature lower than the temperature at which the resin portions 20, 30 change in quality. The temperature at which the resin portions 20, 30 change in quality is, for example, a temperature at which the resin portions 20, 30 undergo thermal decomposition.

[0053] Next, the process proceeds to a welding step S6, where the control circuit 45 uses the heating unit 42 to heat the sides 21, 31 of the resin parts 20, 30 so that the resin parts 20, 30 are kept at or above the melting point Tm. In this embodiment, during the welding step S6, the resin temperature T is kept constant at the second temperature T2 within the range of the allowable error. The allowable error can be set arbitrarily.

[0054] The welding period tm during which the welding step S6 continues may be, for example, a period required for the temperatures of the interface of the first resin part 20 in contact with the first peripheral edge 14b and the interface of the second resin part 30 in contact with the second peripheral edge 15b to reach the melting point Tm or more. Specifically, the preheating period tr is at least 2 seconds, preferably at least 4 seconds, and more preferably at least 5 seconds. The melting point Tm is not limited to this and can be set arbitrarily. The sum of the preheating period tr and the welding period tm is preferably at least 5 seconds, more preferably at least 7 seconds, and even more preferably at least 10 seconds.

[0055] Next, the process proceeds to a cooling step S7, where the control circuit 45 controls the heating unit 42 to cool the resin parts 20 and 30 so that the resin temperature T is less than the softening point Tr. When the control circuit 45 determines that the resin temperature T is less than the softening point Tr, it reduces the resin pressure P and moves the pressing unit 41 away from the sides 21 and 31 of the resin parts 20 and 30. In this embodiment, when the control circuit 45 determines that the resin temperature T is a temperature lower than the softening point Tr by a predetermined buffer temperature, it performs the above-mentioned reduction in pressure. The buffer temperature can be set arbitrarily, but may be set based on, for example, the difference between the softening point Tr of the resin parts 20 and 30 and the supercooling temperature of the resin parts 20 and 30. The supercooling temperature of the resin parts 20 and 30 is a temperature at which the resin parts 20 and 30 are kept softened even when the resin temperature T is less than the softening point Tr during the cooling process of the resin parts 20 and 30. As a result, the side portions 21 , 31 of the molten resin portions 20 , 30 are welded to the main surfaces 14 , 15 of the current collector 12 .

[0056] Next, the process proceeds to a determination step S8, where the control circuit 45 determines whether or not all of the first side portions 21 and the second side portions 31 are welded. Any method of determination may be used, and the determination may be made based on the number of times each of the steps S2 to S7 is performed after the arrangement step S1, or the determination may be made by image recognition using images of the resin parts 20, 30 captured by an imaging element.

[0057] If the determination result in the determination step S8 is negative, the process proceeds to the change step S9, where the side parts 21, 31 to be welded are changed, and the process returns to the contact step S2. The change method is arbitrary, and each pressing part 41a, 41b may be moved onto the side parts 21, 31 that are not welded, or the current collector 12 and the resin parts 20, 30 that have been through the cooling step S7 may be rotated by 90° in a plane perpendicular to the pressing direction. The rotation method is also arbitrary, and the current collector 12 and the resin parts 20, 30 that have been through the cooling step S7 may be rotated together with the workbench, or may be rotated by picking them up using a robot arm or the like.

[0058] On the other hand, if the determination result in the determination step S8 is positive, the control circuit 45 determines that the manufacture of the electrode unit 10 is completed, and the process proceeds to the stacking step S10. In the lamination step S10, when the electrode units 10 manufactured through the above-mentioned steps S1 to S9 reach a predetermined number, the electricity storage module manufacturing apparatus 40 stacks the electrode units 10 in that number. In this embodiment, the electrode units 10 are stacked such that the first active material layer 16 of one electrode unit 10 faces the second active material layer 17 of another electrode unit 10 via a separator (not shown). In this way, in the lamination step S10, the electricity storage module manufacturing apparatus 40 manufactures an electricity storage module B including a plurality of electrode units 10 that have undergone the welding step S6. Any known method is used as the lamination method.

[0059] In the stacking step S10, the electricity storage module manufacturing apparatus 40 of this embodiment further integrates the protruding portions of the resin parts 20, 30 of each of the stacked electrode units 10. Any method for integrating the resin parts 20, 30 may be used, but the electricity storage module manufacturing apparatus 40 may integrate the resin parts 20, 30 adjacent to each other in the stacking direction, for example, by heating and melting the protruding portions of the resin parts 20, 30 with a plurality of electrode units 10 stacked.

[0060] <effect> Next, the operation of this embodiment will be described. First, a comparative example will be described with reference to Fig. 6. In Fig. 6, H2 shows an overview of the resin temperature T and the resin pressure P in each step in the manufacturing method of the comparative example.

[0061] The manufacturing method of the electric storage module B as a comparative example does not perform the preheating step S4, and proceeds from the contact step S2 through a predetermined pressure and temperature raising step to the welding step S6. In this case, the resin parts 20, 30 are welded while the variation in the residual stress of the resin parts 20, 30 remains unmitigated. Therefore, the deformation of the resin parts 20, 30 during melting also varies with the variation in the residual stress. Therefore, unintended deformation of the resin parts 20, 30 may damage the current collector 12.

[0062] On the other hand, in this embodiment, a preheating step S4 is performed before the welding step S6. In the preheating step S4, the resin temperature T, which is the temperature of the resin parts 20, 30, is kept below the melting point Tm. Therefore, in the preheating step S4, welding of the resin parts 20, 30 is suppressed. On the other hand, in the preheating step S4, the first temperature T1 is kept above the softening point Tr. When the resin temperature T becomes above the softening point Tr, the resin parts 20, 30 undergo a phase transition from a solid state to a glassy state. The mobility of the molecules (particularly polymer chains) constituting the resin parts 20, 30 in the glassy state is higher than that in the solid state. Therefore, compared to the case of the solid state, the time required to relax the residual stress of the resin parts 20, 30 is shorter in the glassy state. Therefore, in the preheating step S4, the softening of the resin parts 20, 30 and the relaxation of the residual stress of the resin parts 20, 30 are promoted. As a result, in the subsequent welding step S6, the resin parts 20, 30 with reduced residual stress variation are welded to the main surface 13 of the current collector 12, thereby suppressing damage to the current collector 12 caused by unintended deformation of the resin parts 20, 30.

[0063] Furthermore, in the preheating step S4 of this embodiment, the resin parts 20 and 30 are pressed so that the resin pressure P becomes the preheating pressure P1 during heating. At this time, deformation in the thickness direction (in other words, the pressing direction) of the resin parts 20 and 30 due to softening is restricted. Examples of such deformation include warping and bending of the resin parts 20 and 30.

[0064] Since the preheating pressure P1 is smaller than the welding pressure P2, excessive pressure is prevented from being applied to the resin parts 20, 30 during preheating in the preheating step S4. This promotes the relaxation of residual stress in the resin parts 20, 30. If temporary variations in hardness occur in the resin parts 20, 30 during the softening process, the resin pressure P may concentrate in an area where the relaxation of residual stress is slow. Therefore, by preventing excessive pressure from being applied to the resin parts 20, 30, the concentration of pressure on the main surfaces 14, 15 is suppressed. This reduces the load on the current collector 12 caused by the pressing of the resin parts 20, 30 in the preheating step S4.

[0065] <Effects> (1) The manufacturing method of the electricity storage module B of this embodiment includes an arrangement step S1, a preheating step S4, a welding step S6, and a lamination step S10. In the preheating step S4, the resin parts 20, 30 before welding arranged in the arrangement step S1 are pressed against the main surface 13 of the current collector 12 with a preheating pressure P1, while maintaining a resin temperature T, which is the temperature of the resin parts 20, 30, at or above the softening point Tr and below the melting point Tm, thereby preheating the resin parts 20, 30. The preheating pressure P1 is smaller than a welding pressure P2, which is the resin pressure P in the welding step S6.

[0066] According to this, a preheating step S4 is performed before the resin parts 20, 30 are welded to the main surface 13 of the current collector 12 in the welding step S6. In the preheating step S4, the resin temperature T is kept equal to or higher than the softening point Tr and lower than the melting point Tm, so that welding of the resin parts 20, 30 to the current collector 12 is suppressed and softening of the resin parts 20, 30 is promoted. The softening of the resin parts 20, 30 relieves the residual stress of the resin parts 20, 30. As a result, the variation in the residual stress of the resin parts 20, 30 is reduced prior to the welding step S6.

[0067] On the other hand, as the residual stress is relaxed, unintended deformation of the resin parts 20, 30, such as bending or swell, may occur. Therefore, in the preheating step S4, the resin parts 20, 30 are pressed against the main surface 13 of the current collector 12 with a preheating pressure P1. This makes it possible to restrict the deformation of the resin parts 20, 30 in a direction perpendicular to the main surface 13 of the current collector 12 (in other words, in the thickness direction of the current collector 12) when the residual stress is relaxed in the preheating step S4. Therefore, unintended deformation of the resin parts 20, 30 due to variations in the residual stress can be suppressed, and damage to the current collector 12, which is a metal foil, can be suppressed.

[0068] (2) The arrangement step S1 includes a first arrangement step of arranging the first resin part 20 on the first main surface 14, and a second arrangement step of arranging the second resin part 30 on the second main surface 15. In the preheating step S4, the first resin part 20 and the second resin part 30 are sandwiched and pressed from the first main surface 14 side and the second main surface 15 side, thereby performing the preheating. In the welding step S6, the first resin part 20 and the second resin part 30 are sandwiched and pressed from the first main surface 14 side and the second main surface 15 side, thereby performing the welding.

[0069] According to this, through the preheating step S4 and the welding step S6, the resin parts 20, 30 are welded to both the first main surface 14 and the second main surface 15. As a result, compared to a case in which the resin parts 20, 30 are welded to one of the main surfaces 14, 15, respectively, the force acting on the current collector 12 due to thermal contraction of the resin parts 20, 30 is more likely to act evenly on the current collector 12 from both sides of the main surface 13. Therefore, unintended deformation of the resin parts 20, 30 can be suppressed, and damage to the current collector 12, which is a metal foil, can be suppressed.

[0070] (3) In the arrangement step S1, the resin parts 20, 30 before welding are arranged on each of the main surfaces 14, 15 so that a part of the resin parts 20, 30 protrudes from the peripheral edges 14b, 15b of each of the main surfaces 14, 15. In the stacking step S10, the parts of the resin parts 20, 30 of each of the stacked electrode units 10 that protrude from the peripheral edges 14b, 15b of the main surfaces 14, 15 of the current collector 12 are integrated.

[0071] According to this, in the stacked electrode units 10, the portions of the resin parts 20, 30 that protrude from the peripheries 14b, 15b of the main surfaces 14, 15 are integrated. Here, the portions of the resin parts 20, 30 that protrude from the main surfaces 14, 15 are not welded to the main surfaces 14, 15 of the current collector 12. Therefore, the portions of the resin parts 20, 30 that are different from the portions that are welded to the main surfaces 14, 15 in the welding step S6 are integrated in the stacking step S10. This can reduce the influence of the portions of the resin parts 20, 30 that are welded to the main surfaces 14, 15 when the resin parts 20, 30 are integrated. Therefore, it is possible to suppress unintended deformation of the resin parts 20, 30 during integration, and to further suppress damage to the current collector 12, which is a metal foil.

[0072] (4) In the first transition step S3 and the second transition step S5, the control circuit 45 increases the resin pressure P and then increases the resin temperature T. According to this, the pressing pressure restricts deformation such as warping of the resin parts 20, 30 that accompanies an increase in the resin temperature T. Therefore, it is possible to suppress a decrease in the contact of the resin parts 20, 30 with the main surface 13 that is caused by deformation of the resin parts 20, 30 that accompanies an increase in temperature.

[0073] <Modification> The embodiment can be modified as follows: The embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction.

[0074] The order of increasing the pressure and increasing the temperature in each of steps S1 to S8 can be changed as desired. In addition, increasing the pressure and increasing the temperature do not have to be performed separately, and may be performed in parallel. As long as the arrangement step S1, the preheating step S4, and the welding step S6 are performed, each step can be omitted as appropriate. For example, the contact step S2 may be omitted. In this case, the contact between the pressing parts 41a and 41b and the resin parts 20 and 30 may be determined based on the transition of the resin pressure P detected by the pressure sensor 43 in the first transition step S3.

[0075] Moreover, the side portions 21, 31 may be individually welded by combining a plurality of power storage module manufacturing apparatuses 40. In this case, the determination step S8 and the change step S9 may be omitted.

[0076] The resin temperature T during the preheating step S4 is not limited to the first temperature T1, which is a constant temperature, and any temperature history can be adopted as long as the resin temperature T is equal to or higher than the softening point Tr and lower than the melting point Tm. In other words, the resin parts 20, 30 may be heated and cooled arbitrarily during the preheating step S4, as long as the resin temperature T is equal to or higher than the softening point Tr and lower than the melting point Tm. For example, the resin temperature T may be raised from the softening point Tr to the melting point Tm at a constant heating rate during the preheating step S4. In this case, the heating rate during the preheating step S4 is slower than the heating rate during the first transition step S3. Similarly, in the welding step S6, any temperature history can be adopted as long as the resin temperature T during the welding step S6 is equal to or higher than the melting point Tm.

[0077] The first resin portion 20 does not have to be welded to the first periphery 14b so as to protrude from the first periphery 14b over the entire circumference of the first periphery 14b. For example, the first resin portion 20 may be welded to the first periphery 14b so as to protrude from the first periphery 14b only partially over the entire circumference of the first periphery 14b. Similarly to the first resin portion 20, the second resin portion 30 does not have to be welded to the second periphery 15b so as to protrude from the second periphery 15b over the entire circumference of the second periphery 15b.

[0078] The first resin portion 20 does not have to be welded to protrude from the first peripheral edge 14b. Accordingly, the first resin portion 20 does not have to be disposed to protrude from the first peripheral edge 14b. The first resin portion 20 may be welded to any location on the first main surface 14. Similar to the first resin portion 20, the second resin portion 30 may be welded to any location on the second main surface 15.

[0079] Both the first resin portion 20 and the second resin portion 30 do not have to be welded to the current collector 12, and only one of the first resin portion 20 and the second resin portion 30 may be welded to the current collector 12.

[0080] The rate at which the resin temperature T and the resin pressure P are changed in each process is arbitrary. The configuration of the electricity storage module manufacturing apparatus 40 is merely an example, and is not limited to this. For example, the pressing unit 41 and the heating unit 42 may be realized by a heater roller.

[0081] The pressing unit 41 does not have to be configured to be capable of pressing only the first side portion 21 and the second side portion 31, which are parts of the resin parts 20, 30. For example, the pressing unit 41 may be configured to be capable of pressing the entire resin parts 20, 30.

[0082] In addition, the heating unit 42 does not have to be provided in the pressing units 41a and 41b. For example, the heating unit 42 may be a heater unit provided separately from the pressing units 41a and 41b. The specific form of the heater unit is arbitrary, and may be an electric furnace or an induction heating device. [Explanation of symbols]

[0083] 10...electrode unit, 12...current collector, 13...main surface, 14...first main surface, 14b...first periphery, 15...second main surface, 15b...second periphery, 16...first active material layer, 17...second active material layer, 20...first resin part, 30...second resin part, B...energy storage module, S1...arrangement step, S4...preheating step, S6...welding step, S10...stacking step, P...resin pressure, P1...preheating pressure, P2...welding pressure, T...resin temperature, Tm...melting point, Tr...softening point.

Claims

1. A method for manufacturing an electricity storage module including a plurality of electrode units each including a current collector that is a metal foil, an active material layer provided on a main surface of the current collector, and a resin portion welded to the main surface so as to surround the active material layer, the method comprising the steps of: a placement step of placing the resin portion before welding on the main surface; a preheating step of preheating the resin portion by pressing the disposed resin portion against the current collector with a preheating pressure and maintaining a temperature of the resin portion at a softening point or higher and lower than a melting point of the resin portion; a welding process in which the preheated resin part is pressed against the current collector with a welding pressure while maintaining a temperature of the resin part at or above the melting point, thereby welding the resin part to the main surface, thereby manufacturing the electrode unit; a lamination process for manufacturing the electricity storage module by laminating the electrode units that have been subjected to the welding process, The method for manufacturing an energy storage module, wherein the preheating pressure is lower than the welding pressure.

2. the main surface includes a first main surface and a second main surface located opposite to the first main surface in a thickness direction of the current collector, the resin portion includes a first resin portion welded to the first main surface and a second resin portion welded to the second main surface, the disposing step includes a first disposing step of disposing the first resin part before welding on the first main surface, and a second disposing step of disposing the second resin part before welding on the second main surface, In the preheating step, the first resin portion and the second resin portion are sandwiched and pressed from the first main surface side and the second main surface side, thereby performing the preheating.

2. The method for manufacturing an energy storage module according to claim 1, wherein in the welding process, the first resin part that has been preheated and the second resin part that has been preheated are sandwiched and pressed from the first main surface side and the second main surface side to perform the welding together, thereby welding the first resin part to the first main surface and welding the second resin part to the second main surface.

3. In the disposing step, the resin portion before welding is disposed on the main surface such that a portion of the resin portion protrudes beyond a peripheral edge of the main surface; The method for manufacturing an electricity storage module according to claim 1 , wherein the stacking step further comprises integrating a portion of the resin portion of each of the stacked electrode units that protrudes beyond a peripheral edge of a main surface of the current collector.

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