Power storage module, method for forming an electrolyte inlet, and method for manufacturing power storage module with the method

Abstract

To provide a power storage module with an electrolyte inlet formed in the power storage module, which is easy to inject electrolyte.SOLUTION: A power storage module comprises a resin section, a power generation element surrounded by the resin section, and an electrolyte inlet for injecting electrolyte with a tapered portion that extends from the inside of the power storage module to the outside.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present application relates to a power storage module, a method for forming an electrolyte injection port, and a method for manufacturing a power storage module including the method.

Background Art

[0002] Patent Document 1 describes that in manufacturing a power storage module, an injection port for injecting an electrolyte into the power storage module is formed using a nested structure. Also, Patent Document 2 describes a method for manufacturing a power storage device. Moreover, Patent Document 3 describes a battery module capable of suppressing blockage of communication holes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the injection port formed in the power storage module has a problem that when the height of the injection port in the stacking direction of the power generation elements inside the power storage module is small, the injection of the electrolyte does not proceed.

[0005] An object of the present disclosure is to provide a power storage module including an electrolyte injection port formed in the power storage module, the electrolyte injection port being an electrolyte injection port into which the electrolyte can be easily injected.

Means for Solving the Problems

[0006] As a result of intensive studies by the present inventors to solve the above problems, the following findings were obtained. · By providing a taper having a shape that expands from the inside to the outside of the power storage module at the electrolyte inlet for injecting the electrolyte, the pressure loss of the electrolyte can be reduced. · By setting the taper angle to have a predetermined relationship with respect to the inlet width of the electrolyte inlet, the pressure loss of the electrolyte at the injection port during injection of the electrolyte can be more efficiently reduced.

[0007] Based on the above, the present inventors completed the following aspects.

[0008] [1] A power storage module including a resin part, a power generation element surrounded by the resin part, and an electrolyte inlet for injecting an electrolyte including a taper part that expands from the inside to the outside of the power storage module.

[0009] [2] The power storage module according to [1], wherein the taper part is a taper that expands in the stacking method of the power generation elements.

[0010] [3] The power storage module according to [1] or [2], wherein when the taper part is viewed from the side in a direction perpendicular to the stacking method of the power generation elements, an angle θ formed by the taper and a direction perpendicular to the stacking method of the power generation elements satisfies the following formula (1).

[0011] Angle θ (°) < -0.0062 × inlet width of the electrolyte inlet + 0.7078 Formula (1) The inlet width of the electrolyte inlet means the width in a direction perpendicular to the stacking direction of the power generation elements at the opening of the electrolyte inlet to the outside of the power storage module.

[0012] [4] The power storage module according to any one of [1] to [3], wherein a height in the stacking direction of the power generation elements other than the taper part on the inside of the power storage module side of the electrolyte inlet is 0.15 mm or less.

[0013] [5] The power storage module according to any one of [1] to [4], wherein the width of the opening of the electrolyte injection port to the outside of the power storage module in a direction perpendicular to the stacking direction of the power generation elements is 25 mm or less.

[0014] [6] The power storage module according to any one of [1] to [5], wherein the thickness of the positive electrode in the power generation element in the stacking direction of the power generation elements is 0.25 mm or less.

[0015] [7] A method of forming an electrolyte injection port in the resin part when forming a power storage module including a power generation element surrounded by a resin part, using a nested structure, The method of forming an electrolyte injection port, characterized in that the nested structure includes a tapered part that expands from the inside to the outside of the power storage module.

[0016] [8] A method for manufacturing a power storage module, comprising the method for forming an electrolyte injection port according to [7].

Advantages of the Invention

[0017] According to one embodiment of the present disclosure, a power storage module having a structure in which an electrolyte injection port formed in the power storage module is provided with a predetermined tapered part can be obtained, making it easier to inject the electrolyte.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, an embodiment of a power storage module, a method for forming an electrolyte injection port, and a method for manufacturing a power storage module including the method according to the present invention will be described.

[0020] <Electrolyte injection port in a conventional power storage module> As shown in Patent Document 1, in a conventional power storage module, as shown in FIG. 1, when forming the power storage module, a heat plate 85 is applied around an insert 80 and heat-welded using the insert 80, thereby forming an electrolyte injection port.

[0021] The present inventors have found that when the electrolyte injection port formed in the power storage module has a predetermined shape, it becomes difficult for the electrolyte to flow in, and the following experiment was conducted.

[0022] Using dummy works (No. 1, NO. 2) having injection ports of different shapes shown in Table 1 below, the dummy works were placed in a vacuum chamber, and an experiment was conducted to inject electrolyte into the electrolyte injection ports. The experimental results are shown in Table 1 together.

[0023]

Table 1

[0024] From the above experiment, it was found that when the height of the injection port becomes low, no electrolyte enters the cell at all. The present inventors predict that such a situation occurs because the pressure loss of the electrolyte occurs and the hydraulic pressure decreases due to the decrease in the height of the electrolyte injection port. Based on the above findings, the present inventors have intensively studied and completed various forms of the present disclosure as follows.

[0025] <Power storage module> A power storage module according to an embodiment of the present disclosure includes a resin part, a power generation element surrounded by the resin part, and an electrolyte injection port for injecting an electrolyte including a tapered part that expands from the inside to the outside of the power storage module.

[0026] (Electrolyte injection port) The electrolyte injection port is an electrolyte injection port for injecting an electrolyte into a power storage module including a power generation element surrounded by a resin part, and includes a tapered part that spreads from the inside to the outside of the power storage module.

[0027] (Power storage module including a power generation element surrounded by a resin part) FIG. 2 shows an example of a power storage module 12 including a plurality of power generation elements surrounded by a resin part. A power storage device including one or more power storage modules 12 as shown in FIG. 2 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. In FIG. 2, as an example, a power storage module 12 that is a bipolar battery is illustrated. However, the power storage module 12 may be a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery, or may be an electric double layer capacitor.

[0028] The power storage module 12 shown in FIG. 2 includes a laminate 30 in which a plurality of bipolar electrodes 32 are laminated. When viewed from the lamination direction of the bipolar electrodes 32, the laminate 30 has, for example, a rectangular shape. A separator 40 may be disposed between adjacent bipolar electrodes 32. Each bipolar electrode 32 includes an electrode plate 34, a positive electrode 36 provided on the first surface 34c of the electrode plate 34, and a negative electrode 38 provided on the second surface 34d of the electrode plate 34. In the laminate 30, the positive electrode 36 of one bipolar electrode 32 faces the negative electrode 38 of one adjacent bipolar electrode 32 in the lamination direction with the separator 40 interposed therebetween, and the negative electrode 38 of one bipolar electrode 32 faces the positive electrode 36 of the other adjacent bipolar electrode 32 in the lamination direction with the separator 40 interposed therebetween.

[0029] In the stacking direction, at one end of the stacked body 30, an electrode plate 34 with a negative electrode 38 disposed on its inner surface (the lower surface in the drawing) is arranged. This electrode plate 34 corresponds to the negative terminal electrode. In the stacking direction, at the other end of the stacked body 30, an electrode plate 34 with a positive electrode 36 disposed on its inner surface (the upper surface in the drawing) is arranged. This electrode plate 34 corresponds to the positive terminal electrode. The negative electrode 38 of the negative terminal electrode faces the positive electrode 36 of the uppermost bipolar electrode 32 via a separator 40. The positive electrode 36 of the positive terminal electrode faces the negative electrode 38 of the lowermost bipolar electrode 32 via a separator 40.

[0030] The power storage module 12 includes a cylindrical resin part (outer package) 50 that extends in the stacking direction of the bipolar electrodes 32 and houses the stacked body 30. The resin part 50 holds the peripheral edges 34a of the plurality of electrode plates 34. The resin part 50 is configured to surround the stacked body 30. The resin part 50 has, for example, a rectangular shape when viewed from the stacking direction of the bipolar electrodes 32. That is, the resin part 50 is, for example, a square tube shape.

[0031] The resin part 50 has a first seal part 52 that is joined to the peripheral edge 34a of the electrode plate 34 and holds the peripheral edge 34a, and a second seal part 54 provided outside the first seal part 52 in a direction (X direction and Y direction) intersecting the stacking direction. The second seal part 54 is provided in a sealed state with the first seal part 52.

[0032] The first seal portion 52 that constitutes the inner wall of the resin portion 50 is provided over the entire circumference of the peripheral edge portion 34a of the electrode plate 34 in the plurality of bipolar electrodes 32 (that is, the laminate 30). The first seal portion 52 is, for example, welded to the peripheral edge portion 34a of the electrode plate 34 and seals the peripheral edge portion 34a. That is, the first seal portion 52 is joined to the peripheral edge portion 34a of the electrode plate 34. The peripheral edge portion 34a of the electrode plate 34 of each bipolar electrode 32 is held in a state of being buried in the first seal portion 52. The peripheral edge portions 34a of the electrode plates 34 disposed at both ends of the laminate 30 are also held in a state of being buried in the first seal portion 52. Thereby, an internal space V hermetically and watertightly partitioned by the electrode plates 34, 34 and the first seal portion 52 is formed between the electrode plates 34, 34 adjacent to each other in the stacking direction. An electrolytic solution (not shown) made of an alkaline solution such as an aqueous potassium hydroxide solution is accommodated in the internal space V. Note that the “volume of the internal space V” means a volume including the voids of the separator 40.

[0033] The outer peripheral surface 52a of the first seal portion 52 is a heat-welded surface. The second seal portion 54 that constitutes the outer wall of the resin portion 50 covers the outer peripheral surface 52a of the first seal portion 52 extending in the stacking direction of the bipolar electrodes 32. The inner peripheral surface 54a of the second seal portion 54 is, for example, welded to the outer peripheral surface 52a of the first seal portion 52 and seals the outer peripheral surface 52a. That is, the second seal portion 54 is joined to the outer peripheral surface 52a of the first seal portion 52. The welding surface (joint surface) of the second seal portion 54 with respect to the first seal portion 52 forms, for example, four rectangular planes.

[0034] The electrode plate 34 is a rectangular metal foil made of, for example, nickel. The peripheral portion 34a of the electrode plate 34 is an uncoated region where the positive electrode active material and the negative electrode active material are not coated. In the uncoated region, the electrode plate 34 is exposed. The uncoated region is buried and held in the first seal portion 52 that constitutes the inner wall of the resin portion 50. Examples of the positive electrode active material that constitutes the positive electrode 36 include composite oxides, metallic lithium, sulfur, and the like. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, LiNiMnCoO2, and the like. Examples of the negative electrode active material that constitutes the negative electrode 38 include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements that can be alloyed with lithium or compounds of the elements, boron-added carbon, and the like. The formation region of the negative electrode 38 on the second surface 34d of the electrode plate 34 may be slightly larger than the formation region of the positive electrode 36 on the first surface 34c of the electrode plate 34.

[0035] The separator 40 is formed, for example, in a sheet shape. The separator 40 has, for example, a rectangular shape. Examples of the material for forming the separator 40 include a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric or non-woven fabric made of polypropylene, or the like. Further, the separator 40 may be reinforced with a vinylidene fluoride resin compound or the like.

[0036] The resin portion 50 (the first seal portion 52 and the second seal portion 54) is formed, for example, in a rectangular cylindrical shape by injection molding using an insulating resin. Examples of the resin material that constitutes the resin portion 50 include polypropylene (PP), polyphenylene sulfide (PPS), or modified polyphenylene ether (modified PPE), and the like.

[0037] In the power storage module 12, a single layer of cells (power generation elements) is constituted by a positive electrode 36 on the first surface 34c side of the electrode plate 34, a negative electrode 38 on the second surface 34d side of the adjacent electrode plate 34, a separator 40 between the positive electrode 36 and the negative electrode 38, and a resin part 50 that seals the space between the first surface 34c and the second surface 34d. The resin part 50 restricts the movement of gas and electrolyte from one cell to another. Thereby, insulation between adjacent cells is ensured.

[0038] When manufacturing the power storage module 12, when forming the exterior body 50, an electrolyte injection port for introducing an electrolyte into the power storage module 12 is formed using a plate-shaped insert 80 having a predetermined width as shown in FIG. 1. Note that in FIG. 2, the electrolyte injection port is not shown.

[0039] (Tapered portion spreading from the inside to the outside of the power storage module) In the above, it has been shown that when the height of the electrolyte injection port becomes low, no electrolyte enters the cell. However, the reason why the height of the electrolyte injection port becomes low in the first place will be explained with reference to FIG. 3. FIG. 3 is a cross-sectional view of the vicinity of the electrolyte injection port 80 inside the power storage module 12.

[0040] The electrolyte injection port 80 shown in FIG. 3 is formed using a plate-shaped insert having no taper. In FIG. 3, a unit cell (power generation element) composed of a positive electrode 36, a negative electrode 38, a separator 40, and a sealing material 522 formed between the electrode plates 34 is shown. From the viewpoint of forming the electrolyte injection port 80 at a position sandwiched between the sealing material 522 and the separator 40, the height of the electrolyte injection port 80 becomes equal to or less than the thickness of the positive electrode 36. Therefore, when reducing the positive electrode thickness to improve the power generation efficiency, the height of the electrolyte injection port also becomes low. Note that the sealing material 522 is used for forming the first seal part 522. The first seal part 52 is formed by laminating the electrodes surrounded by the sealing material 522 together with the separator 40 and then welding the end faces of the sealing material 522 to each other.

[0041] The inventors have found that in order to introduce the electrolytic solution into the cell while keeping the height of the electrolytic solution injection port low, it is necessary to provide a tapered portion that spreads from the inside to the outside of the power storage module at the electrolytic solution injection port. FIG. 4 is a perspective view showing the shape of an embodiment of the electrolytic solution injection port 90 of the present invention. The cell side has a plate-like shape 92 with a uniform height, and a tapered portion 94 is provided on the opposite electrolytic solution inflow side.

[0042] The height A of the opening (inlet) on the tapered portion 94 side where the electrolytic solution flows in is preferably 0.2 mm or more. This makes it possible to easily allow the electrolytic solution to enter the space of the electrolytic solution injection port first. Also, the height of the plate-like shape 92 having a uniform height on the cell side is preferably 0.15 mm or less. This height is determined by the positive electrode thickness. By reducing the height of the plate-like shape 92, the positive electrode thickness can be reduced, and the power generation efficiency can be improved. Regarding the relationship between the width B of the inlet and the taper angle θ of the tapered portion, when the width B of the inlet is wide, the surface tension becomes larger accordingly, making it difficult for the electrolytic solution to enter. Therefore, it is necessary to make the angle θ gentle.

[0043] In FIG. 5, the taper angle θ is taken on the vertical axis and the width B of the inlet is taken on the horizontal axis. The case where the electrolytic solution could be introduced into the electrolytic solution injection port is indicated by "〇", and the case where it could not be introduced is indicated by "×". As a result, it was found that in order to introduce the electrolytic solution, it is preferable that the taper angle θ and the width B of the inlet at the electrolytic solution injection port satisfy the following formula (1).

[0044] Angle θ (°) < -0.0062 × Inlet width of electrolytic solution injection port + 0.7078 Formula (1) The inlet width of the electrolytic solution injection port means the width in the direction perpendicular to the stacking direction of the power generation elements at the opening of the electrolytic solution injection port to the outside of the power storage module (width B in FIG. 4).

[0045] <Method for forming electrolytic solution injection port> The method for forming an electrolyte injection port of the present invention is a method for forming an electrolyte injection port in the resin part using an insert when forming a power storage module including a power generation element surrounded by the resin part, characterized in that the insert includes a tapered part that expands from the inside to the outside of the power storage module.

[0046] According to the above method, by using an insert having a predetermined tapered part to form an outer package, an electrolyte injection port is formed in the resin part along the shape of the insert. As shown in FIG. 4, the shape of the electrolyte injection port is tapered outward toward the outside of the cell (electrolyte inflow side), and at the position where the taper is maximized, there is an opening on the electrolyte inflow side. The insert to be used is, for example, an equal-width strip-shaped film member. The constituent material of the insert may be a material having heat resistance to the extent of being resistant to the processing temperature in heat welding when forming the resin part, and a metal material is mentioned as an example.

[0047] <Method for manufacturing a power storage module> The method for manufacturing a power storage module of the present invention includes the method for forming the electrolyte injection port described above.

Explanation of reference numerals

[0048] 12: Power storage module 30: Laminate 32: Bipolar electrode 34: Electrode plate 36: Positive electrode 38: Negative electrode 50: Resin part 90: Electrolyte inflow port

Claims

1. A power storage module comprising a resin part, a power generation element surrounded by the resin part, and an electrolyte injection port for injecting an electrolyte provided with a tapered part that spreads from the inside to the outside of the power storage module.

2. The power storage module according to claim 1, wherein the tapered part is a taper that spreads in the stacking method of the power generation elements.

3. The power storage module according to claim 1 or 2, wherein, when the tapered part is viewed from the side in a direction perpendicular to the stacking method of the power generation elements, the angle θ formed by the taper and the direction perpendicular to the stacking method of the power generation elements satisfies the following formula (1). Angle θ (°) < -0.0062 × inlet width of the electrolyte injection port + 0.7078 Formula (1) The inlet width of the electrolyte injection port means the width in a direction perpendicular to the stacking direction of the power generation elements at the opening of the electrolyte injection port to the outside of the power storage module.

4. The power storage module according to claim 1 or 2, wherein the height in the stacking direction of the power generation elements, excluding the tapered part on the inner side of the power storage module of the electrolyte injection port, is 0.15 mm or less.

5. The power storage module according to claim 1 or 2, wherein the width in a direction perpendicular to the stacking direction of the power generation elements of the opening of the electrolyte injection port to the outside of the power storage module is 25 mm or less.

6. The power storage module according to claim 1 or 2, wherein the thickness in the stacking direction of the positive electrode in the power generation element is 0.25 mm or less.

7. A method of forming an electrolyte injection port in the resin part by using a nest when forming a power storage module including a power generation element surrounded by the resin part, The method of forming an electrolyte injection port, characterized in that the nest is provided with a tapered part that spreads from the inside to the outside of the power storage module.

8. A method of manufacturing a power storage module, comprising the method of forming an electrolyte injection port according to claim 7.

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