Energy storage module

Abstract

To suppress performance degradation caused by gases generated in the negative electrode composite layer. [Solution] The energy storage module comprises an electrode stack in which a plurality of electrodes, each containing a current collector 11 and an asphalt mixture layer, are stacked, and a resin frame that forms an internal space S between adjacent current collectors 11 in the stacking direction in which an electrolyte 8 is contained and seals the internal space S. The electrode stack has separators 40 provided between adjacent electrodes in the stacking direction, the asphalt mixture layer includes a positive electrode asphalt mixture layer divided into a plurality of regions with a plurality of grooves 14 provided in between, and the frame has a communication hole 7 that connects the internal space S to the outside. The separators 40 are arranged along the grooves 14 and are joined to the current collectors 11 inside the grooves 14.

Description

Technical Field

[0001] The present invention relates to an electricity storage module. Background Art

[0002] Patent Document 1 discloses an electricity storage module including an electrode laminate in which a plurality of electrodes are stacked, having a structure where a positive electrode mixture layer is divided into a plurality of parts by linear grooves, and a separator is disposed so as to straddle the grooves. Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Patent Application Laid-Open No.2022-025869 Summary of the Invention Problems to be Solved by the Invention

[0004] However, in the configuration described in Patent Document 1, when gas is generated from the negative electrode mixture layer, the gas does not pass through the separator and pushes the separator toward the positive electrode mixture layer side within the groove, so that the electrolyte is pushed out from the groove, resulting in depletion of electrolyte in the vicinity of the electrodes, which may possibly lead to performance deterioration.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electricity storage module capable of suppressing performance deterioration caused by gas generated in a negative electrode mixture layer. Means for Solving the Problems

[0006] The present invention relates to an electrode storage module comprising: an electrode stack comprising a current collector and a plurality of electrodes including an asphalt layer provided on one or both sides of the current collector; and a resin frame that forms an internal space for containing an electrolyte between adjacent current collectors in the stacking direction and seals the internal space, wherein the electrode stack has separators provided between adjacent electrodes in the stacking direction, the asphalt layer includes a positive electrode asphalt layer divided into a plurality of regions with a plurality of grooves provided between them, and the frame has a communication hole that connects the internal space to the outside, wherein the separator is arranged along the grooves and is joined to the current collector inside the grooves. [Effects of the Invention]

[0007] In this invention, it is possible to suppress performance degradation caused by gas generated in the negative electrode composite layer. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an energy storage module in an embodiment. [Figure 2] This is a cross-sectional view showing the stacked structure of an energy storage module. [Figure 3] This diagram illustrates the groove, separator, and communication hole. [Figure 4] This diagram illustrates the groove, separator, positive electrode composite layer, and negative electrode composite layer. [Figure 5] This figure shows the positive electrode composite layer divided by grooves. [Figure 6] This is a cross-sectional view showing the shape of the groove. [Figure 7] This diagram illustrates a structure in which a separator is joined to the bottom surface of a groove. [Figure 8] This diagram illustrates how gas generated from the negative electrode composite layer diffuses into the electrolyte within the groove. [Figure 9] This diagram shows a method for laser welding a separator to the bottom surface of a groove. [Figure 10]This diagram shows a structure in which a separator is welded along the bottom surface of the groove. [Figure 11] This diagram shows a method for heat-welding a separator to the bottom surface of a groove by heating and pressurizing. [Figure 12] This figure shows the separator being heated and pressurized against the current collector by a heat press. [Modes for carrying out the invention]

[0009] The following describes in detail the energy storage module in the embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0010] Figure 1 is a perspective view showing an energy storage module in an embodiment. The energy storage module 1 is a bipolar battery. The energy storage module 1 is included in a battery pack installed in electric vehicles such as hybrid vehicles and electric vehicles. The battery pack including the energy storage module 1 is a bipolar energy storage device in which multiple energy storage modules 1 are stacked. For example, the energy storage module 1 is composed of lithium-ion batteries.

[0011] The energy storage module 1 comprises an electrode stack 2 in which multiple electrodes are stacked, a resin frame 3 that seals the electrode stack 2, and a liquid injection section 4 attached to the frame 3.

[0012] As shown in Figure 2, the electrode stack 2 is a stack of multiple cells 5. The electrode stack 2 has a structure in which multiple bipolar electrodes 10, a positive terminal electrode 20, a negative terminal electrode 30, and multiple separators 40 are stacked. Each cell 5 is composed of a positive electrode composite layer and a negative electrode composite layer stacked via separators 40.

[0013] The bipolar electrode 10 comprises a current collector 11, a positive electrode mixture layer 12 provided on one surface of the current collector 11, and a negative electrode mixture layer 13 provided on the other surface of the current collector 11. The current collector 11 is a current collector formed in a rectangular sheet shape and is constituted of a metal foil. The positive electrode mixture layer 12 is formed by applying a positive electrode mixture onto the current collector 11. The positive electrode mixture comprises a positive electrode active material, a conductive aid, and a binder. The positive electrode active material comprises NCM (nickel-cobalt-manganese ternary positive electrode material) or LFP (lithium iron phosphate). The positive electrode mixture forms the positive electrode mixture layer 12 on one surface of the current collector 11. The positive electrode mixture layer 12 is a positive electrode active material layer and is formed as a porous body. The negative electrode mixture layer 13 is formed by applying a negative electrode mixture onto the current collector 11. The negative electrode mixture comprises a negative electrode active material, a conductive aid, and a binder. The negative electrode active material comprises carbon, silica and the like. The negative electrode mixture forms the negative electrode mixture layer 13 on the other surface of the current collector 11. The negative electrode mixture layer 13 is a negative electrode active material layer and is formed as a porous body. One surface of the current collector 11 comprises a positive electrode side uncoated portion where the positive electrode mixture layer 12 is not provided in a peripheral edge portion. The other surface of the current collector 11 comprises a negative electrode side uncoated portion where the negative electrode mixture layer 13 is not provided in a peripheral edge portion. The peripheral edge portion of the current collector 11 is an uncoated portion where neither the positive electrode mixture layer 12 nor the negative electrode mixture layer 13 is provided.

[0014] The positive terminal electrode 20 comprises a positive current collector 21 and a positive electrode mixture layer 22 provided on one surface of the positive current collector 21. The positive current collector 21 is a current collector formed in a rectangular sheet shape and is constituted of a metal foil. The positive electrode mixture layer 22 is formed by applying a positive electrode mixture onto the positive current collector 21. A peripheral edge portion of the positive current collector 21 is an uncoated portion where the positive electrode mixture layer 22 is not provided.

[0015] The negative terminal electrode 30 comprises a negative current collector 31 and a negative electrode mixture layer 32 provided on one surface of the negative current collector 31. The negative current collector 31 is a current collector formed in a rectangular sheet shape and is constituted of a metal foil. The negative electrode mixture layer 32 is formed by applying a negative electrode mixture onto the negative current collector 31. A peripheral edge portion of the negative current collector 31 is an uncoated portion where the negative electrode mixture layer 32 is not provided.

[0016] In the electrode stack 2, bipolar electrodes 10 and separators 40 are alternately stacked between a positive terminal electrode 20 and a negative terminal electrode 30. Among the bipolar electrodes 10 adjacent to each other in the stacking direction, a positive electrode mixture layer 12 of one bipolar electrode 10 and a negative electrode mixture layer 13 of the other bipolar electrode 10 are stacked with a separator 40 interposed therebetween. The stacking direction coincides with the Z direction.

[0017] The separator 40 is a porous membrane made of a resin such as polyethylene. The separator 40 is provided between electrodes adjacent to each other in the stacking direction. The separator 40 is interposed between the positive electrode mixture layer and the negative electrode mixture layer.

[0018] In this description, when there is no need to distinguish between the current collector 11, the positive current collector 21, and the negative current collector 31, they are simply referred to as current collectors. Similarly, when there is no need to distinguish between the positive electrode mixture layer 12, the negative electrode mixture layer 13, the positive electrode mixture layer 22, and the negative electrode mixture layer 32, they are simply referred to as mixture layers. Further, when there is no need to distinguish between the positive electrode mixture layer 12 and the positive electrode mixture layer 22, they are described as positive electrode mixture layers without reference signs, and when there is no need to distinguish between the negative electrode mixture layer 13 and the negative electrode mixture layer 32, they are described as negative electrode mixture layers without reference signs. Furthermore, when there is no particular need to distinguish between the bipolar electrode 10, the positive terminal electrode 20, and the negative terminal electrode 30, they are simply referred to as electrodes. An electrode includes a current collector and a mixture layer provided on one or both surfaces of the current collector.

[0019] The frame body 3 is formed so as to surround the electrode stack 2 when viewed from the stacking direction. The frame body 3 forms an internal space S for accommodating an electrolyte between current collectors adjacent to each other in the stacking direction. The frame body 3 is a sealing portion that seals the internal space S. The frame body 3 is provided at the peripheral edge of the current collector and arranged so as not to contact the mixture layer. The frame body 3 is formed by a resin portion 6 provided at the peripheral edge of the current collector. In the frame body 3, a plurality of sealing materials are laminated on the peripheral edge of the current collector. The frame body 3 has a structure in which a plurality of resin portions 6 are stacked and welded to each other.

[0020] The resin part 6 is a frame-shaped sealing material formed along the periphery of the current collector. The resin part 6 is welded to the periphery of the current collector. The resin part 6 and the current collector are welded together by a heat sealer or laser. The resin part 6 is made of an insulating resin. The resin part 6 is made of polypropylene, polyethylene, polyphenylene sulfide, polystyrene, etc.

[0021] As shown in Figure 3, the frame 3 is provided with communication holes 7 that connect the internal space S to the outside. A communication hole 7 is provided for each cell 5, connecting the inside of the cell 5 to the outside of the frame 3. The communication hole 7 is provided in the resin part 6 that forms one side of the frame 3 extending in the X direction, and extends in the Y direction inside the resin part 6. The X direction coincides with the width direction of the energy storage module 1, and the Y direction coincides with the length direction of the energy storage module 1. When viewing the energy storage module 1 from the Z direction, the X direction is the short side direction of the energy storage module 1, and the Y direction is the long side direction of the energy storage module 1. The communication hole 7 has an opening that faces in the Y direction. The opening of the communication hole 7 is an injection port for injecting electrolyte into the inside of the electrode stack 2. The communication hole 7 functions as a flow path for the electrolyte when it is injected into the inside of the electrode stack 2.

[0022] The communication holes 7 are sealed by the liquid injection section 4. The frame 3 has an electrolyte injection port formed by the communication holes 7. The liquid injection port is located on one side of the frame 3 that extends in the X direction, and is positioned on one side in the Y direction when viewed from the Z direction. An injection port is provided for each cell 5, and each injection port is sealed by the liquid injection section 4. The liquid injection section 4 is a resin component. The liquid injection section 4 is welded to the frame 3. For example, the liquid injection section 4 includes a resin frame formed for each liquid injection port and a sealing material that seals the opening of the resin frame. The sealing material of the liquid injection section 4 is made of film.

[0023] As shown in Figure 4, the positive electrode composite layer 12 is divided into multiple regions by grooves 14 formed in between. As shown in Figure 5, the grooves 14 extend in the Y direction and divide the positive electrode composite layer 12 into different regions in the X direction. As shown in Figure 3, the grooves 14 extend in the direction in which the opening of the communication hole 7 opens. The grooves 14 extend in a direction parallel to the direction in which the liquid injection port opens and are formed in a region inside the uncoated positive electrode portion of the current collector 11. The grooves 14 are the portions in which the positive electrode composite layer 12 is not provided. As shown in Figure 6, the grooves 14 are formed in a rectangular shape when viewed from the Y direction. The grooves 14 have a flat bottom surface 14a made from one side of the current collector 11 and a wall surface 14b made from the positive electrode composite layer 12. In the grooves 14, the pair of wall surfaces 14b face each other in the X direction. The groove width of the grooves 14 is 0.5 to 20 mm. The thickness of the positive electrode composite layer 12 is 30 to 500 μm.

[0024] As shown in Figure 4, the separator 40 is positioned between the positive electrode composite layer and the negative electrode composite layer, covering the entire positive electrode composite layer, and is positioned to follow the groove 14 of the positive electrode composite layer. The separator 40 has heat welding and adhesive properties and is fixed to the current collector 11.

[0025] As shown in Figure 7, the separator 40 is positioned inside the groove 14 so as to conform to the shape of the groove 14 and is joined to the current collector 11. Inside the groove 14, the separator 40 is formed in a rectangular shape that conforms to the shape of the groove 14. The separator 40 is in contact with the bottom surface 14a and the wall surface 14b inside the groove 14. The surface 40a of the separator 40 is joined to the bottom surface 14a, which is made up of the current collector 11. The surface 40a is joined to the bottom surface 14a along the bottom surface 14a. For example, the separator 40 is continuously joined to the current collector 11 inside the groove 14 along the extending direction of the groove 14. The separator 40 is joined to the current collector 11 in the Y direction over a range from inside the groove 14 to the unpainted area on the positive electrode side. In other words, the separator 40 is also joined to the current collector 11 in the area outside the groove 14. As shown in Figures 2 and 3, the end of the separator 40 does not extend to the resin portion 6, but is joined to the current collector 11. This joining method may be heat welding or the like.

[0026] As shown in Figure 8, by arranging the separator 40 along the shape of the groove 14 inside the groove 14, the gas 9 generated in the negative electrode composite layer 13 diffuses into the electrolyte 8 within the groove 14. Therefore, the separator 40 is not pushed up by the gas 9, and the discharge of the electrolyte 8 from inside the groove 14 due to the pushing up of the separator 40 can be suppressed. This prevents the electrolyte 8 from disappearing from the vicinity of the electrode due to the generation of gas 9. The communication hole 7 functions as a passage for venting the gas 9 generated from the negative electrode composite layer during the activation treatment when manufacturing the energy storage module 1. Because the separator 40 is provided along the shape of the groove 14, gas venting performance is improved during the activation treatment.

[0027] A joining method for joining the separator 40 to the current collector 11 within the groove 14 will be described. As this joining method, a welding process is possible in which the separator 40 is welded to the current collector 11 using a laser. As shown in Figure 9, in the welding process, the separator 40 is positioned on the electrode sheet 50 so as to completely cover the positive electrode composite layer 12, and laser light L is irradiated from the laser light source 101 toward the groove 14. As shown in Figure 6, the electrode sheet 50 is a sheet in which a positive electrode composite layer 12 and a negative electrode composite layer 13 are provided on both sides of the current collector 11, and a resin portion 6 is provided on the peripheral edge of the current collector 11. After the welding process, as shown in Figure 10, the separator 40 is welded to the current collector 11 in a shape along the groove 14.

[0028] As described above, according to the embodiment, since the separator 40 is arranged and joined to the groove 14 along the shape of the groove 14, the gas 9 generated in the negative electrode composite layer 13 diffuses into the electrolyte 8 within the groove 14. Therefore, the gas 9 does not push the separator 40 into the groove 14, and the loss of electrolyte 8 from the vicinity of the electrode can be suppressed. This makes it possible to suppress performance deterioration.

[0029] The number of grooves 14 is not particularly limited. In the example shown in Figure 4, etc., the example is limited to a case where the positive electrode composite layer 12 is divided into three regions by two grooves 14, but the number of grooves 14 is not limited to two. There may be one groove 14, or there may be three or more.

[0030] Furthermore, in the energy storage module 1, the positive electrode composite layer 22 is divided into multiple regions by grooves 14 formed in between. In the energy storage module 1, grooves 14 are provided not only in the bipolar electrode 10 but also in the positive electrode termination electrode 20.

[0031] Furthermore, the position in the X direction where the groove 14 is provided is not particularly limited. The groove 14 only needs to extend parallel to the direction in which the opening of the communication hole 7 faces, and does not necessarily have to be opposite the opening in the Y direction.

[0032] Furthermore, the current collector 11 may be a laminated foil in which a positive electrode foil and a negative electrode foil are bonded together by an adhesive layer. One side of the current collector 11 is formed by the positive electrode foil, and the other side of the current collector 11 is formed by the negative electrode foil. If the energy storage module 1 is a lithium-ion battery, the positive electrode foil is aluminum foil and the negative electrode foil is copper foil.

[0033] Furthermore, the end of the separator 40 may extend to the resin part 6. In this case, the end of the separator 40 is joined to the resin part 6, and the joining method may be heat welding or the like.

[0034] Furthermore, the method of joining the current collector 11 and the separator 40, which form the bottom surface 14a of the groove 14, is not limited to laser welding. In other words, the joining method may be a method of heat welding using a laser, or a method of heating and pressurizing the separator 40 after applying an adhesive layer. For example, as shown in Figures 11 and 12, a joining method is possible in which the separator 40 is heated and pressurized using a hot press 102. As shown in Figure 11, the hot press 102 is integrated with an elastic body 103. The elastic body 103 is in contact with the separator 40. The elastic body 103 has a projection 103a that follows the shape of the groove 14. As shown in Figure 12, the hot press 102 heats and pressurizes the separator 40 via the elastic body 103. [Explanation of symbols]

[0035] 1. Energy storage module 2-electrode stack 3 Frame 4. Injection section 5 cells 6. Resin part 7 Communication hole 8 Electrolyte 9 Gas 10 bipolar electrodes 14 grooves 40 Separators S interior space

Claims

1. An electrode laminate comprising a current collector and an electrode including a composite material layer provided on one or both sides of the current collector, An internal space is formed between adjacent current collectors in the stacking direction, containing an electrolyte, and a resin frame is provided to seal the internal space. Equipped with, The electrode stack has separators provided between adjacent electrodes in the stacking direction, The composite material layer includes a positive electrode composite material layer divided into multiple regions by having multiple grooves in between, The frame is a power storage module having a communication hole that connects the internal space to the outside, The separator is arranged along the groove and is joined to the current collector inside the groove. A battery storage module characterized by the following features.

2. The groove portion includes a flat bottom surface formed by the current collector, The separator is joined to the bottom surface along the bottom surface. The energy storage module according to claim 1.

3. The groove extends toward the internal space in the direction toward the opening of the communication hole, The separator is continuously joined to the current collector within the groove along the direction of extension of the groove. The energy storage module according to claim 2.

4. The electrode includes an uncoated portion at the periphery of the current collector where the composite material layer is not applied. The separator is bonded to the current collector in the direction of extension of the groove, extending from the groove to the uncoated portion. The energy storage module according to claim 3.

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