Manufacturing method of power storage module

Abstract

To provide a manufacturing method of a power storage module in which generation of a void at the time of welding a sealing member for sealing a liquid injection hole is suppressed to suppress a short circuit between cells.SOLUTION: A manufacturing method of a power storage module includes: a preparation step of preparing an electrode stacked body 11 including a plurality of electrodes stacked along a stacking direction, a resin-made first sealing member 21 in which a first communication hole 25 communicating with an internal space V formed between the adjacent electrodes is formed and which is provided so as to surround a side surface 11a along the stacking direction of the electrode stacked body 11, and a resin-made second sealing member 22 in which a second communication hole 26 communicating with the first communication hole 25 is formed and which is provided so as to surround the outer surface 21a of the first sealing member 21 in the stacking direction; a liquid injection step of injecting an electrolytic solution into the internal space V through the first communication hole 25 and the second communication hole 26; and a sealing step of melting the second sealing member 22 and flowing it into the first communication hole 25 to seal the first communication hole 25.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] An example of a method for manufacturing an electricity storage module is disclosed in Patent Document 1.

[0003] The method for manufacturing an energy storage module described in Patent Document 1 includes a welding step in which a module main body having a sealing member and a pressure regulating valve having a case are integrated by hot plate welding. The welding step uses a hot plate welding device equipped with a hot plate main body and a thin, rigid cover plate with high thermal conductivity that is detachably attached to the hot plate main body. The bonding protrusions of the sealing member and the case are respectively brought into contact with the outer surface of the cover plate. When the bonding protrusions are heated and melted by a predetermined amount, the bonding protrusions are separated from the outer surface of the cover plate, and then the bonding protrusions are brought into pressure contact with each other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-173921 Summary of the Invention [Problem to be solved by the invention]

[0005] A known energy storage module includes a plurality of electrodes stacked in a stacking direction with separators interposed between them. In such an energy storage module, a resin sealant is provided on a side surface of the electrode stack to seal between adjacent electrodes in the stacking direction, and an electrolyte solution is contained in an internal space formed between the adjacent electrodes.

[0006] In the process of manufacturing this type of energy storage module, an electrolyte solution is injected into the internal space through an injection hole provided in a sealing body such as a case. After the electrolyte solution is injected, the injection hole may be sealed using a film-like sealing member such as a laminate film or a resin film. When welding the film-like sealing member to the sealing body, it is possible to melt the sealing member by heating and bond it to the sealing body.

[0007] On the other hand, when such a sealing member is heated, the air inside the sealing body is heated and the internal pressure increases, which makes it easier for the air inside the sealing body to escape to the outside of the sealing body through the molten sealing member. If cooling is performed in this state, air may be left between the sealing member and the sealing body, causing voids. If voids are generated between the sealing member and the sealing body, there is a risk of short-circuiting between cells formed by a pair of electrodes facing each other with a separator interposed therebetween.

[0008] The present invention has been made to solve such problems, and aims to provide a method for manufacturing an energy storage module that suppresses the occurrence of voids when welding a sealing member that seals the liquid injection hole, thereby suppressing short circuits between cells. [Means for solving the problem]

[0009] A method for manufacturing a storage module according to one embodiment includes a preparation process for preparing an electrode stack including a plurality of electrodes stacked along a stacking direction, a first sealing member made of resin having a first communicating hole communicating with an internal space formed between adjacent electrodes and arranged to surround the side surface of the electrode stack along the stacking direction, and a second sealing member made of resin having a second communicating hole communicating with the first communicating hole and arranged to surround the outer surface of the first sealing member in the stacking direction; an injection process for injecting an electrolyte into the internal space through the first communicating hole and the second communicating hole; and a sealing process for melting the second sealing member, pouring it into the first communicating hole, and sealing the first communicating hole. [Effects of the Invention]

[0010] The present invention can provide a method for manufacturing an electricity storage module that suppresses the occurrence of voids when welding a sealing member that seals an injection hole, thereby suppressing short circuits between cells. [Brief explanation of the drawings]

[0011] [Figure 1] 5A to 5C are cross-sectional views illustrating a method for manufacturing the electricity storage module according to the first embodiment. [Figure 2] 1A and 1B are a cross-sectional view and a top view showing an electricity storage module manufactured by a method for manufacturing an electricity storage module according to a first embodiment; [Figure 3] 10 is a cross-sectional view illustrating a problem that occurs when the first communication hole is sealed with a film-like sealing member. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments. Furthermore, for clarity of explanation, the following description and drawings have been simplified as appropriate. What is shown in the drawings is only a part of the whole, and in reality, many other configurations not shown are included. In the following description, the same or equivalent elements are given the same reference numerals, and redundant explanations will be omitted.

[0013] A method for manufacturing an energy storage module 1 according to the first embodiment (hereinafter sometimes referred to as "the manufacturing method") will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view illustrating the method for manufacturing an energy storage module according to the first embodiment. The manufacturing method includes a preparation step (step S1), a liquid injection step (step S2), and a sealing step (step S3).

[0014] First, as shown in S1 of FIG. 1, a preparation step prepares a module having an electrode stack 11, a plurality of first sealing members 21, and a second sealing member 22. The electrode stack 11, the plurality of first sealing members 21, and the second sealing member 22 constitute a module body. The electrode stack 11 includes a plurality of electrodes stacked in a stacking direction (DR1) with separators 13 interposed therebetween. The plurality of electrodes includes a stack of a plurality of bipolar electrodes 14, a negative terminal electrode, and a positive terminal electrode. In such an electrode stack 11, a single cell is formed by a pair of electrodes facing each other with the separators 13 interposed therebetween. The stack of a plurality of bipolar electrodes 14 is stacked between the negative terminal electrode and the positive terminal electrode.

[0015] The bipolar electrode 14 includes an electrode plate 15 including one surface 15a and another surface 15b opposite the one surface 15a, a positive electrode 16 provided on the one surface 15a, and a negative electrode 17 provided on the other surface 15b. The positive electrode 16 is a positive electrode active material layer formed by coating the electrode plate 15 with a positive electrode active material. The negative electrode 17 is a negative electrode active material layer formed by coating the electrode plate 15 with a negative electrode active material. In the electrode stack 11, the positive electrode 16 of one bipolar electrode 14 faces the negative electrode 17 of another bipolar electrode 14 adjacent to it on one side in the stacking direction, with the separator 13 interposed therebetween. In the electrode stack 11, the negative electrode 17 of one bipolar electrode 14 faces the positive electrode 16 of another bipolar electrode 14 adjacent to it on the other side in the stacking direction, with the separator 13 interposed therebetween.

[0016] The negative terminal electrode has an electrode plate 15 and a negative electrode 17 provided on the other surface 15b of the electrode plate 15. The negative terminal electrode is disposed at one end in the stacking direction so that the other surface 15b faces the center of the electrode stack 11 in the stacking direction. The negative electrode 17 provided on the other surface 15b of the electrode plate 15 of the negative terminal electrode faces the positive electrode 16 of the bipolar electrode 14 at one end in the stacking direction, via the separator 13.

[0017] The positive terminal electrode has an electrode plate 15 and a positive electrode 16 provided on one surface 15a of the electrode plate 15. The positive terminal electrode is disposed at the other end in the stacking direction such that one surface 15a faces the center of the electrode stack 11 in the stacking direction. The positive electrode provided on one surface 15a of the positive terminal electrode faces, via the separator 13, the negative electrode 17 of the bipolar electrode 14 at the other end in the stacking direction.

[0018] The electrode plate 15 is made of a metal plate, such as a nickel plate or a steel plate. Here, the electrode plate 15 is made of a plated steel plate, which is formed by plating the surface of a steel plate with nickel. The steel plate used as the base material for the plated steel plate may be ordinary steel, such as rolled steel, or specialty steel, such as stainless steel. The edge portion 15c of the electrode plate 15 has a rectangular frame shape and is an uncoated region where the positive electrode active material and the negative electrode active material are not applied. Examples of positive electrode active materials that constitute the positive electrode 16 include nickel hydroxide. Examples of negative electrode active materials that constitute the negative electrode 17 include hydrogen storage alloys. In this embodiment, the area where the negative electrode 17 is formed on the other surface 15b of the electrode plate 15 is slightly larger than the area where the positive electrode 16 is formed on the one surface 15a of the electrode plate 15.

[0019] The separator 13 is formed, for example, in the shape of a sheet. Examples of the separator 13 include a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), and a woven or nonwoven fabric made of polypropylene, methyl cellulose, etc. The separator 13 may be reinforced with a vinylidene fluoride resin compound.

[0020] The first sealing member 21 is provided on the side surface 11a of the electrode stack 11 so as to surround the side surface 11a along the stacking direction of the electrode stack 11. The first sealing member 21 is joined to the side surface 11a of the edge portion 15c of the electrode plate 15. The first sealing member 21 is provided continuously around the entire periphery of the side surface 11a of the edge portion 15c, and has a rectangular frame shape when viewed from the stacking direction. The first sealing member 21 can be formed, for example, by injection molding of resin. In this embodiment, the first sealing member 21 is provided not only on the electrode plate 15 of the bipolar electrode 14, but also on the electrode plate 15 of the negative terminal electrode and the electrode plate 15 of the positive terminal electrode.

[0021] The first sealing member 21 is hermetically welded to the side surface 11a of the edge portion 15c by, for example, ultrasonic or thermocompression bonding, and is joined airtightly. The first sealing member 21 protrudes outward from the edge of the electrode plate 15 in the up-down direction (DR2), which is a direction perpendicular to the stacking direction. Note that the up-down direction is an example provided for convenience of explanation, and is unrelated to the direction when the energy storage module 1 is in use, etc.

[0022] The second sealing member 22 is provided on the outside of the electrode stack 11 and the first sealing member 21. The second sealing member 22 is provided on the outer surface 21a of each first sealing member 21 so as to surround the outer surface 21a of the first sealing member 21 along the stacking direction. The second sealing member 22 can be formed, for example, by injection molding of resin. The second sealing member 22 extends over the entire length of the electrode stack 11 along the stacking direction. The second sealing member 22 has a rectangular frame shape extending in the stacking direction. The second sealing member 22 is welded to the outer surface 21a of the first sealing member 21 by heating in a sealing process described below. The outer surface 21a is the surface of the first sealing member 21 on which the opening 22c is formed.

[0023] The first sealing member 21 and the second sealing member 22 are made of, for example, an insulating resin having alkali resistance. Examples of materials that can be used to form the first sealing member 21 and the second sealing member 22 include polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), and modified polyphenylene ether (modified PPE).

[0024] A plurality of first communication holes 25 that communicate with each internal space V formed between adjacent electrodes are formed in the first sealing member 21. Each first communication hole 25 extends in the vertical direction from the outer surface 21a of the first sealing member 21 to the inner surface.

[0025] A plurality of second communication holes 26 communicating with each of the first communication holes 25 are formed in the second sealing member 22. Each second communication hole 26 extends in the stacking direction from the outer surface 22a to the inner surface of the second sealing member 22. The opening 22c is an opening of the second communication hole 26 formed in the outer surface 22a.

[0026] The first and second communication holes 25, 26 function as injection holes for injecting the electrolyte into the internal space V. After the electrolyte is injected, the first and second communication holes 25, 26 also serve as flow paths for the gas generated in the internal space V to flow.

[0027] 1, in the injection step, an electrolyte is injected into each of the internal spaces V through the first communication hole 25 and the second communication hole 26. In this embodiment, the electrolyte is a non-aqueous electrolyte. For example, an injection device 100 shown in S2 of FIG. 1 can be used to inject the electrolyte.

[0028] 1, the liquid injection device 100 includes a connector 101, a plurality of liquid injection nozzles 102, and an electrolyte solution supply unit 103. The liquid injection device 100 is a device that supplies the electrolyte solution supplied from the electrolyte solution supply unit 103 to each internal space V through the plurality of liquid injection nozzles 102.

[0029] The connector 101 is a rectangular plate-like member for connecting a plurality of liquid injection nozzles 102 to the second sealing member 22 of the module body. The connector 101 can be fitted to the outer surface 22a along the stacking direction of the second sealing member 22. The connector 101 is formed so as to cover the outer surface 22a in which the opening 22c is formed.

[0030] The liquid injection nozzle 102 has a discharge port at its tip for discharging the electrolyte. The liquid injection nozzle 102 extends in a vertical direction perpendicular to the stacking direction so that the discharge port faces the inside of the second communication hole 26. The liquid injection nozzle 102 is inserted into the connector 101. The liquid injection nozzles 102 are provided in a number corresponding to the plurality of second communication holes 26. The liquid injection nozzles 102 are arranged between the second sealing members 22 adjacent to each other in the stacking direction. Each liquid injection nozzle 102 is provided with a valve 104 for opening and closing the liquid injection nozzle 102.

[0031] The electrolyte solution supply unit 103 is connected to the plurality of injection nozzles 102. The electrolyte solution supply unit 103 includes a supply tank capable of holding the electrolyte solution, a pump that pressure-feeds the electrolyte solution in the supply tank to the injection nozzles 102, and the like. The electrolyte solution supply unit 103 is in communication with the plurality of injection nozzles 102.

[0032] When injecting electromechanical fluid using the injection device 100, first, the connector 101 is fitted into the second sealing member 22 from the outer surface 22a, thereby closing the opening 22c with the connector 101. Then, with the valve 104 open, the electrolyte supply unit 103 is operated, and the electrolyte supplied from the electrolyte supply unit 103 is injected into the internal space V through the second communication hole 26 and the first communication hole 25 by the injection nozzle 102.

[0033] In the sealing process, after the electrolyte is injected, the second sealing member 22 is melted and poured into the first communicating holes 25 to seal the first communicating holes 25. For sealing, for example, a welding device 200 shown in S3-1 and S3-2 in FIG. 1 can be used. As shown in S3-1 and S3-2 in FIG. 1, the welding device 200 has a hot plate 201, a heater, and a temperature sensor. The welding device 200 is a device that welds the second sealing member 22 to the first sealing member 21 using the hot plate 201.

[0034] The hot plate 201 is a rectangular plate-like member. The hot plate 201 has, for example, a melting surface 201a on its lower surface. The hot plate 201 is made of, for example, a metal such as iron or stainless steel. The hot plate 201 is provided, for example, so as to be movable up and down relative to the second sealing member 22 of the module main body.

[0035] The heater heats the hot plate 201. The heater is, for example, a cartridge heater. The heater is, for example, built into the hot plate 201.

[0036] The temperature sensor detects the temperature of the hot plate 201. The temperature sensor is, for example, a thermocouple. The temperature sensor is, for example, disposed on the melting surface 201a of the hot plate 201.

[0037] The heater and the temperature sensor are each connected to a control circuit (not shown) that controls the welding apparatus 200. The control circuit includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). In this case, the control circuit loads programs stored in the ROM into the RAM and executes them on the CPU to perform various processes.

[0038] Here, the hot plate 201 is rectangular and covers the outer surface 22a where the opening 22c is formed. The hot plate 201 is provided with a plurality of recesses 202 recessed upward from the melting surface 201a. The number of recesses 202 corresponds to the number of openings 22c. The plurality of recesses 202 are arranged adjacent to each other along the stacking direction. The recesses 202 are formed in the shape of a quadrangular pyramid that widens from the base end (upper end) to the tip end (lower end). The opening at the lower end of the recess 202 is larger than the opening 22c.

[0039] The hot plate 201 has a tapered inner peripheral surface 203 formed by each recess 202. A pair of inclined surfaces of the inner peripheral surface 203 facing each other in the stacking direction are inclined approximately symmetrically so that the gap between them in the stacking direction increases from the upper end to the lower end. A pair of inclined surfaces of the inner peripheral surface 203 facing each other in the direction perpendicular to the stacking direction and the vertical direction are inclined approximately symmetrically so that the gap between them in the direction perpendicular to the stacking direction and the vertical direction increases from the upper end to the lower end.

[0040] As described above, the hot plate 201 has a tapered inner peripheral surface 203, and thus, when welding the second sealing member 22 to the first sealing member 21, the tapered inner peripheral surface 203 (slope) can guide the molten second sealing member 22. Therefore, the hot plate 201 can guide the molten second sealing member 22 into the first communicating holes 25. Since the inner peripheral surface 203 of the hot plate 201 guides the molten second sealing member 22 into the first communicating holes 25, the molten second sealing member 22 can be easily filled into the first communicating holes 25. In this embodiment, the inclination angle of each slope constituting the inner peripheral surface 203 is 45°. When the inclination angle of each slope is 45°, the molten second sealing member 22 can be efficiently guided into the first communicating holes 25.

[0041] When melting second sealing member 22 using welding device 200, hot plate 201 disposed above second sealing member 22 is lowered to bring melting surface 201a into contact with outer surface 22a of second sealing member 22. This melts second sealing member 22. At this time, second sealing member 22 is pressed against outer surface 22a.

[0042] The pushing amount of the second sealing member 22 (the melting amount of the second sealing member 22) is set in advance. In this embodiment, the length of the second sealing member 22 in the vertical direction perpendicular to the stacking direction is 4 mm, so the pushing amount of the second sealing member 22 is preferably 4 mm. By matching the pushing amount of the second sealing member 22 to the vertical length of the second sealing member 22, the hot plate 201 is seated on the first sealing member 21, and the first communication hole 25 can be suitably sealed.

[0043] The heating temperature and heating time of the heater are not particularly limited as long as they are sufficient to melt second sealing member 22. In this embodiment, the heating temperature of the heater is 180° C., and the heating time is 30 seconds.

[0044] After heating at a predetermined heating temperature for a predetermined heating time, the heating plate 201 is raised to separate the heating plate 201 from the outer surface 22a of the second sealing member 22.

[0045] The manufacturing method described above can obtain the energy storage module 1 shown in FIG. 2. FIG. 2 is a cross-sectional view and a top view showing an energy storage module manufactured by the manufacturing method for an energy storage module according to the first embodiment. In the energy storage module 1, a film-like sealing member may be bonded to the outer surfaces 21a, 22a of the first sealing member 21 so as to cover the outer surface 21a of the first sealing member 21 and the outer surface 22a of the second sealing member 22 that seals the first communication holes 25. The sealing member may be, for example, a laminate film or a resin film. Examples of materials for the resin film include PP, PET, PPS, and modified PPE. Such a sealing member may have a single-layer structure or a multilayer structure in which different materials are laminated. As such a sealing member, for example, a film having a three-layer structure in which a PE layer, an aluminum laminate layer, and a PET layer are laminated in this order can be preferably used.

[0046] 2, the energy storage module 1 manufactured by this manufacturing method includes an electrode stack 11, a first sealing member 21 provided to surround a side surface 11a of the electrode stack 11, and a second sealing member 22 provided to surround an outer surface 22a of the first sealing member 21. The second sealing member 22 seals a first communication hole 25 provided in the first sealing member 21. The second sealing member 22 is composed of a portion that is welded to the outer surface 21a of the first sealing member 21 and covers the opening 22c, and a plug-shaped portion that is inserted along the inner circumferential surface 203 of the first communication hole 25.

[0047] The first sealing member 21 and the second sealing member 22 included in the energy storage module 1 form an internal space V between adjacent electrodes and seal the internal space V. More specifically, the second sealing member 22 seals the first communication hole 25 provided in the first sealing member 21. Furthermore, the second sealing member 22, which seals the first communication hole 25, together with the first sealing member 21 seals the spaces between adjacent bipolar electrodes 14 in the stacking direction, between adjacent negative electrode terminal electrodes and bipolar electrodes 14 in the stacking direction, and between adjacent positive electrode terminal electrodes and bipolar electrodes 14 in the stacking direction. As a result, airtightly partitioned internal spaces V are formed between adjacent bipolar electrodes 14, between the negative electrode terminal electrode and bipolar electrode 14, and between the positive electrode terminal electrode and bipolar electrode 14. An electrolyte is contained in this internal space V. The separator 13, the positive electrode 16, and the negative electrode 17 are impregnated with the electrolyte.

[0048] Here, referring to Fig. 3, a description will be given of problems that arise when first communication hole 25 is sealed with film-like sealing member 30 instead of second sealing member 22. Fig. 3 is a cross-sectional view that describes problems that arise when first communication hole 25 is sealed with a film-like sealing member. Fig. 3 is a view corresponding to Fig. 2.

[0049] As shown in Fig. 3, the sealing member 30 seals the first communication hole 25 provided in the first sealing member 21. The sealing member 30 shown in Fig. 3 has a three-layer structure in which a PE layer 31, an aluminum laminate layer 32, and a PET layer 33 are laminated in this order. The sealing member 30 is welded to the outer surface 21a of the first sealing member 21 after the liquid injection step, and is thereby joined to the outer surface 21a.

[0050] During welding, the sealing member 30 is heated to melt it. However, when the sealing member 30 is heated in this manner, the air inside the first sealing member 21 is heated and the internal pressure increases, which makes it easier for the air inside the first sealing member 21 to escape to the outside of the first sealing member 21 through the molten sealing member 30 (welded interface). If cooling is performed in this state, air may be left between the sealing member 30 and the first sealing member 21, causing voids. If voids occur between the sealing member 30 and the first sealing member 21, there is a risk of short-circuiting between the cells.

[0051] In contrast, the present manufacturing method includes a preparation step of preparing an electrode stack 11, a first sealing member 21 made of resin, and a second sealing member 22 made of resin. The electrode stack 11 includes a plurality of electrodes stacked in a stacking direction. The first sealing member 21 has first communication holes 25 that communicate with an internal space V formed between adjacent electrodes and is provided to surround a side surface 11a of the electrode stack 11 along the stacking direction. The second sealing member 22 has second communication holes 26 that communicate with the first communication holes 25 and is provided to surround an outer side surface 21a of the first sealing member 21 along the stacking direction. The present manufacturing method also includes a liquid injection step of injecting an electrolyte into the internal space V through the first communication holes 25 and the second communication holes 26, and a sealing step of melting the second sealing member 22 and pouring it into the first communication holes 25 to seal the first communication holes 25.

[0052] In this manufacturing method, the second sealing member 22 is melted and poured into the first communication holes 25 provided in the first sealing member 21, thereby sealing the first communication holes 25. According to this manufacturing method, when the molten second sealing member 22 is poured into the first communication holes 25, the molten second sealing member 22 is pressed against the outer surface 22a, so that the air inside the second sealing member 22 is pressed into the internal space V through the first communication holes 25. This makes it possible to manufacture an energy storage module 1 that suppresses the generation of voids when welding the second sealing member 22 that seals the first communication holes 25 (liquid injection holes), thereby suppressing short circuits between cells.

[0053] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention. [Explanation of symbols]

[0054] 1. Energy storage module 11 electrode laminate 11a side surface 13 separator 14 bipolar electrode 15 Electrode plate 15a One side 15b Other side 15c Edge 16 Positive electrode 17 Negative electrode 21 First sealing member 21a Outer surface 22 Second sealing member 22a Outer surface 22c Opening 25 1st communication hole 26 2nd communication hole 100 liquid injection device 101 connector 102 liquid injection nozzle 103 electrolyte supply unit 104 valve 200 welding device 201 hot plate 201a melting surface 202 recess 203 inner peripheral surface V interior space

Claims

[Claim 1] a preparation step of preparing an electrode stack including a plurality of electrodes stacked along a stacking direction, a first sealing member made of resin and having first communication holes communicating with internal spaces formed between adjacent electrodes and provided to surround a side surface of the electrode stack along the stacking direction, and a second sealing member made of resin and having second communication holes communicating with the first communication holes and provided to surround an outer side surface of the first sealing member in the stacking direction; a liquid injection step of injecting an electrolyte into the internal space through the first communication hole and the second communication hole; a sealing step of melting the second sealing member and pouring it into the first communication hole to seal the first communication hole; A method for manufacturing a storage module having the above structure.

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