Bipolar battery module

Abstract

To provide a bipolar battery module that improves performance in injecting an electrolyte into an internal space of a cell.SOLUTION: A bipolar battery module of the present disclosure has a structure in which a plurality of cells 10 are laminated in a lamination direction of bipolar electrodes 60. Each of the plurality of cells has an internal space 40 in which an electrolyte is stored between two positive and negative electrode foils adjacent to each other in the lamination direction. In part of an outer peripheral part of each cell, a sealing member 30 forms an opening for injection 42 to inject the electrolyte into the internal space. In an opening for injection 42B in at least one cell 10B, a peripheral part of at least one positive and negative electrode foil 20C, of the two positive and negative electrode foils, is arranged inclined to the adjacent cell 10C, and thereby has a shape spread toward the adjacent cell.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a bipolar battery module. [Background technology]

[0002] Patent Document 1 discloses an electricity storage module including at least one electrode unit. In the electricity storage module disclosed in Patent Document 1, a spacer that maintains the distance between a pair of current collectors in the electrode unit is formed in a frame shape surrounding an active material layer by connecting multiple spacer members arranged along the outer periphery of the current collectors. A seal member that seals the seams is provided on exposed portions of the seams between the multiple spacer members on the outer periphery of the frame-shaped spacer. The outer periphery of the spacer has a first region covered by the seal member and a second region not covered by the seal member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-16904 Summary of the Invention [Problem to be solved by the invention]

[0004] Fig. 6 shows a schematic diagram of an example of an opening for electrolyte injection in a cell in a conventional bipolar battery module. In a battery having a bipolar structure shown in Fig. 6, electrolyte is injected into an internal space 40P from the opening of each cell. The total thickness T of the separator 16P and the positive and negative electrode layers 12P and 14P is the height of the internal space of the cell, and therefore greatly affects the electrolyte injection property. When the energy density of the positive electrode layer 14P and the negative electrode layer 12P is increased, the thickness of the positive and negative electrode layers 12P, 14P is set to be thin. When the thickness of the positive and negative electrode layers 12P, 14P is reduced, the total thickness of the separator 16P and the positive and negative electrode layers 12P, 14P is reduced, and the height of the internal space of the cell is reduced. Therefore, the height (distance in the thickness direction) H of the injection hole is also reduced, and the injection property is reduced.

[0005] An object of the present disclosure is to provide a bipolar battery module in which the injection of an electrolyte into the internal space of a cell is improved. [Means for solving the problem]

[0006] Means for solving the above problems include the following embodiments.

[0007] <1> an electrode laminate in which a plurality of bipolar electrodes are laminated with separators interposed therebetween, the bipolar electrodes having a positive electrode mixture layer disposed on a positive electrode foil side of positive and negative electrode foils and a negative electrode mixture layer disposed on a negative electrode foil side of positive and negative electrode foils; A sealing member that covers the peripheral portion of the positive and negative electrode foils; Including, A structure in which a plurality of cells are stacked in the stacking direction of the bipolar electrodes, each of the plurality of cells has an internal space between two of the positive and negative electrode foils adjacent to each other in the stacking direction in which an electrolyte is accommodated, and a liquid injection opening for injecting the electrolyte into the internal space is formed by the sealing member in a part of an outer periphery of each cell; a bipolar battery module, wherein the liquid injection opening in at least some of the plurality of cells has a shape that spreads toward the adjacent cell because the peripheral portion of at least one of the two positive and negative electrode foils is positioned so as to be biased toward the adjacent cell. <2> The liquid injection openings extending toward the adjacent cells are formed at intervals of one or more cells in the plurality of cells. <1> The bipolar battery module according to claim 1 . <3> The injection opening portion extending toward the adjacent cell side is formed by folding the peripheral portion of the positive and negative electrode foil in a stepped shape, and a portion closer to an end than the folded portion is covered by the sealing member. <1> or <2> The bipolar battery module according to claim 1 . <4> The plurality of cells is three or more cells, and the volume of the internal space of at least one of the two cells positioned outermost in the stacking direction is the smallest among the volumes of the internal spaces of the plurality of cells. <1> ~ <3> 13. The bipolar battery module according to claim 12, <5> the electrolyte injection opening is sealed in a state in which the electrolyte is contained in the internal space of each of the plurality of cells; <1> ~ <4> 13. The bipolar battery module according to claim 12, Effect of the Invention

[0008] According to the present disclosure, a bipolar battery module is provided that improves the injection of electrolyte into the internal space of the cell. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a bipolar battery module according to the present disclosure. [Diagram 2] 2 is a schematic partial cross-sectional view showing a part of a cross section taken along line AA in FIG. 1. [Diagram 3] 10 is a partial schematic cross-sectional view showing an example of a state in which an electrolyte injection opening is sealed after electrolyte is injected into an internal space of a cell through the electrolyte injection opening. FIG. [Figure 4] 2 is a schematic partial cross-sectional view showing a part of the cross section along line BB in FIG. 1. [Diagram 5] 10 is a partial schematic cross-sectional view showing another example of a liquid injection opening in a bipolar battery module according to the present disclosure. FIG. [Figure 6] FIG. 11 is a partial schematic cross-sectional view showing an example of a liquid injection opening of a cell in a conventional bipolar battery module. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the present disclosure, a numerical range indicated using "~" means a range including the numerical values ​​described before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper limit value described in a certain numerical range may be replaced with the upper limit value of another numerical range described in stages, and the lower limit value described in a certain numerical range may be replaced with the lower limit value of another numerical range described in stages. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0011] Hereinafter, an embodiment of a bipolar battery module according to the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will be omitted as appropriate. In addition, in the drawings, the same or corresponding parts, for example, cells 10A, 10B, 10C, 10D, and 10E, may be collectively referred to as cells 10. In addition, in the present disclosure, the term bipolar battery module is not limited to a configuration in which an electrolyte is contained in the internal space of each cell and sealed, but also includes a configuration before an electrolyte is contained in the internal space of each cell and sealed.

[0012] Fig. 1 is a schematic diagram showing an example of a bipolar battery module according to the present disclosure. A large number of liquid injection nozzles 112, 114 are provided on an exterior body 120. Fig. 2 is a schematic partial cross-sectional view showing a part of the cross section along line AA in Fig. 1. The bipolar battery module 100 includes an electrode laminate 70 in which a plurality of bipolar electrodes 60 are laminated with separators 16 interposed therebetween, and a sealing member 30 that covers the peripheral portions of positive and negative electrode foils (current collectors) 20. The positive and negative electrode foils 20 are formed by bonding a negative electrode foil 22 and a positive electrode foil 24 together.

[0013] Each bipolar electrode 60 has a configuration in which a positive electrode mixture layer 14 is disposed on the positive electrode foil 24 side of the positive and negative electrode foils 20, and a negative electrode mixture layer 12 is disposed on the negative electrode foil 22 side.

[0014] The bipolar battery module 100 has a structure in which a plurality of cells 10 are stacked in the stacking direction of the bipolar electrodes 60. Each cell 10 has an internal space 40 in which an electrolyte is contained between two positive and negative electrode foils 20, 20 adjacent to each other in the stacking direction of the bipolar electrodes 60. A liquid injection opening 42 for injecting an electrolyte into the internal space 40 is formed by the sealing member 30 in a part of the outer periphery of each cell 10. In FIG. 2, the liquid injection opening 42B of the cell 10B is shown.

[0015] At the injection opening 42B of the cell 10B, the peripheral portion of the positive and negative electrode foil 20C (the portion of the positive and negative electrode foil 20C where the negative electrode mixture layer 12B and the positive electrode mixture layer 14C are not formed) is folded in a stepped shape. The portion of the positive and negative electrode foil 20C closer to the end than the folded portion is covered with a sealing member 30C. Meanwhile, an end of the separator 16B is welded to the sealing member 30B that covers the peripheral portion of the positive and negative electrode foil 20B.

[0016] The sealing member 30C at the end of the positive and negative electrode foil 20C contacts the positive and negative electrode foil 20D of the cell 10C adjacent to the cell 10B. The positive and negative electrode foils 20C, 20D do not come into direct contact with each other, thereby preventing a short circuit. The peripheral edge of the positive and negative electrode foil 20C is folded in a stepped shape and positioned toward the adjacent cell 10C, and the liquid injection opening 42B is expanded toward the adjacent cell 10C. This configuration makes it easier to inject electrolyte into the internal space of the cell 10B from the liquid injection opening 42B (sometimes referred to as the "expanded opening" in this specification).

[0017] In the bipolar battery module according to the present disclosure, at least one of the two positive and negative foils 20B, 20C arranged opposite each other at the liquid injection opening 42B of the cell 10B may have a peripheral portion biased toward the adjacent cell. For example, the peripheral portion of the positive and negative foil 20B may be biased toward the adjacent cell 10A. Alternatively, the peripheral portions of the positive and negative foils 20B, 20C may be biased toward the adjacent cells 10A, 10C, respectively, to further widen the liquid injection opening 42B.

[0018] The liquid injection opening 42B of the cell 10B is formed at a position corresponding to the liquid injection nozzle 112 of the bipolar battery module 100 shown in Fig. 1. By supplying the electrolyte through the liquid injection nozzle 112, the electrolyte is injected from the liquid injection opening 42B into the internal space of the cell 10B. The electrolyte injected into the internal space of cell 10B permeates through negative electrode mixture layer 12 and further through separator 16B to permeate into positive electrode mixture layer 14.

[0019] 3 is a partial schematic cross-sectional view showing an example of a state in which the electrolyte injection opening 42B is sealed after the electrolyte is injected into the internal space 40B of the cell 10B from the electrolyte injection opening 42B. The electrolyte 50 is injected into the internal space 40B of the cell 10B through the electrolyte injection opening 42B. After injection, the electrolyte injection opening 42B is sealed by the electrolyte injection port sealing members 32, 34, and 36. As a result, the electrolyte 50 injected into the inside of the cell 10B remains in the area surrounded by the positive and negative electrode foils 20B and 20C and the sealing member 36.

[0020] FIG. 4 is a partial schematic cross-sectional view showing a part of the cross section taken along the line BB in FIG. 1. FIG. 4 shows the liquid injection opening 42D in the cell 10D. The peripheral edge of the positive and negative electrode foil 20E is folded in a stepped shape and arranged to one side of the adjacent cell 10E. As a result, the liquid injection opening 42D of the cell 10D also has a shape that spreads toward the adjacent cell 10E side. The liquid injection opening 42D of the cell 10D is formed at a position corresponding to the liquid injection nozzle 114 of the bipolar battery module. By supplying the electrolyte through the liquid injection nozzle 114, the electrolyte is injected from the liquid injection opening 42D into the internal space 40D of the cell 10D. As with the liquid injection opening 42B, the liquid injection opening 42D is sealed by a liquid injection port sealing member (not shown) after injection.

[0021] In the bipolar battery module 100 according to the present disclosure, the liquid injection openings (enlarged openings) 42B, 42D that expand toward the adjacent cell side are formed at intervals of one cell each, as shown in Figures 2 and 4. In the bipolar battery module according to the present disclosure, the enlarged openings may be formed at intervals of one or more cells, or the liquid injection openings of each cell 10 may have a shape that expands to the adjacent cell at different positions on the outer periphery.

[0022] The cells 10A, 10C, and 10E have injection openings (not shown) at positions different from the injection openings 42B and 40D of the cells 10B and 10D, for example, on the opposite side. The injection openings of the cells 10A, 10C, and 10E also have a shape in which the peripheral parts of the positive and negative electrode foils extend toward the adjacent cell side, thereby improving the injection of the electrolyte. In the internal spaces 40A, 40C, and 40E of the cells 10A, 10C, and 10E, the electrolyte is injected from the corresponding injection nozzle (not shown) through the injection opening and then sealed.

[0023] The bipolar battery module 100 functions as a storage battery when an electrolyte is injected into the internal space of each cell 10 and the electrolyte injection opening is sealed.

[0024] (Variation 1) 5 is a partial schematic cross-sectional view showing another example of a liquid injection opening in a bipolar battery module according to the present disclosure. The peripheral portion of the positive and negative electrode foil 20B of the cell 10B is arranged to be inclined toward the adjacent cell 10A. Even if the peripheral portion of the positive and negative electrode foil of each cell is not folded in a stepped shape and is arranged to be inclined toward the adjacent cell, the liquid injection opening 42B is widened, improving the liquid injection property.

[0025] (Variation 2) The volume of the internal space of at least one of the two cells (sometimes referred to as the "outermost cells" in this disclosure) located on the outermost sides in the stacking direction of a structure in which three or more cells are stacked may be made the smallest among the volumes of the internal spaces of the other cells. In conventional bipolar battery modules, when the inside of the cells is kept in a reduced pressure state, the degree of reduced pressure inside each cell cannot be monitored from the outside while the module is in the state where the cells are overlapped.

[0026] On the other hand, for example, in FIG. 2, when the cells 10A and 10E are the outermost cells, at least one of the outermost cells, for example the cell 10A, is designed to have the smallest volume of the internal space 40A. When the pressure inside the cells rises due to the inflow of outside air, the internal pressure of the outermost cell 10A, which has the narrowest internal space 40A, rises the most, and it is possible to determine whether there is an abnormality in the internal pressure by visual inspection or measurement. For example, the outermost cell 10A has an exposed flat surface of the exterior body, and the pressure inside the cell can be detected by placing a pressure sensor on the flat surface. This eliminates the need to monitor the internal pressure of all the cells in the bipolar battery module.

[0027] There is no particular limitation on the method for narrowing the internal space of the outermost cell 10A. For example, as shown in Fig. 2, there are a method of narrowing the internal space 40A by folding the positive and negative electrode foils 20A to make the sealing member 30A longer than the other cells, a method of narrowing the internal space 40A by disposing a spacer (not shown) between the positive and negative electrode foils 20A and 20B of the outermost cell 10A, and a method of narrowing the internal space 40A by making the areas of the positive electrode mixture layer 14A and the negative electrode mixture layer 12A larger than the areas of the positive electrode mixture layers and the negative electrode mixture layers of the other cells.

[0028] The components of the bipolar battery module according to the present disclosure will be described in detail below, but the components of the bipolar battery module according to the present disclosure are not limited to the following description.

[0029] (Electrode laminate) The electrode stack 70 is, for example, a rectangular parallelepiped. The electrode stack 70 includes a plurality of bipolar electrodes 60 stacked with a separator 16 interposed therebetween. Specifically, the electrode stack 70 has a plurality of bipolar electrodes 60, a plurality of separators 16, a positive electrode layer side end electrode (not shown), and a negative electrode layer side end electrode (not shown). The plurality of bipolar electrodes 60 and the plurality of separators 16 are alternately stacked along the axial direction. The positive electrode layer side end electrode is stacked with a separator interposed on the bipolar electrode located on the outermost side of one of the plurality of bipolar electrodes 60 in the stacking direction. The negative electrode layer side end electrode is stacked with a separator interposed on the bipolar electrode located on the outermost side of the other of the plurality of bipolar electrodes in the stacking direction.

[0030] (Bipolar electrode) The bipolar electrode 60 has positive and negative electrode foils 20, a positive electrode mixture layer 14, and a negative electrode mixture layer 12. The peripheral edge of the positive and negative electrode foils 20 is welded to a sealing member 30. The positive electrode mixture layer 14 is formed on the positive electrode foil 24 side of the positive and negative electrode foils 20. The negative electrode mixture layer 12 is formed on the negative electrode foil 22 side of the positive and negative electrode foils 20. The bipolar electrode 60 may have a known configuration.

[0031] The positive and negative electrode foils 20 supply current to the positive electrode mixture layer 14 and the negative electrode mixture layer 12 during discharging or charging of the bipolar battery module 100. Examples of the positive and negative electrode foils 20 include aluminum foil, copper foil, nickel foil, titanium foil, stainless steel foil, and the like. A coating layer may be formed by a known method (for example, plating, spray coating, etc.) on the surface of the positive and negative electrode foils 20. The thickness of the positive and negative electrode foils 20 may be 1 μm to 100 μm.

[0032] The positive electrode mixture layer 14 includes a positive electrode layer active material (e.g., a lithium composite metal oxide having a layered rock salt structure, a metal oxide having a spinel structure, a polyanion-based compound, etc.) capable of absorbing and releasing charge carriers. The positive electrode mixture layer 14 may further include a conductive assistant (e.g., carbon nanofiber, etc.) for increasing electronic conductivity, a binder (e.g., polyvinylidene fluoride, etc.), an electrolyte supporting salt (lithium salt) for increasing ionic conductivity, a polymer electrolyte, and an additive (e.g., trifluoropropylene carbonate, a filler as a reinforcing material, etc.) as necessary. The thickness of the positive electrode mixture layer 14 may be 2 μm to 500 μm.

[0033] The negative electrode mixture layer 12 includes a negative electrode layer active material capable of absorbing and releasing charge carriers (for example, carbon (for example, natural graphite, artificial graphite), a compound capable of alloying with lithium (for example, silicon, tin, etc.), etc.). The negative electrode mixture layer 12 may further include a conductive assistant (for example, acetylene black, etc.) for increasing electronic conductivity, a binder (for example, polyvinylidene fluoride, etc.), an electrolyte supporting salt (lithium salt) for increasing ionic conductivity, a polymer electrolyte, and an additive (for example, trifluoropropylene carbonate, a filler as a reinforcing material, etc.) as necessary. The thickness of the negative electrode mixture layer 12 may be 2 μm to 500 μm. The thickness of the negative electrode mixture layer 12 may be the same as or different from the thickness of the positive electrode mixture layer 14. In the embodiment shown in FIG. 2, the length of the negative electrode mixture layer 12 is longer than the length of the positive electrode mixture layer 14.

[0034] (Separator) The separator 16 maintains a distance between the positive electrode mixture layer 14 and the negative electrode mixture layer 12 to prevent contact short circuit, and allows charge carriers such as lithium ions (e.g., lithium ions, etc.) to pass through. The periphery of the separator 16 is welded to the sealing member 30. The separator 16 is held by the sealing member 30. Examples of the separator 16 include a porous resin sheet or a nonwoven fabric. Examples of the material of the porous resin sheet include polyolefin (polypropylene, polyethylene, etc.). Examples of the material of the nonwoven fabric include polypropylene, polyethylene terephthalate, methylcellulose, etc. The separator may have a known configuration.

[0035] (Positive electrode layer side termination electrode) The positive electrode layer side terminal electrode has a positive electrode foil and a positive electrode mixture layer. The positive electrode mixture layer is formed on the negative electrode foil of the positive electrode foil. The positive electrode layer side terminal electrode may have a known configuration.

[0036] (Negative layer side terminal electrode) The negative electrode layer side terminal electrode has a positive electrode foil and a negative electrode mixture layer. The negative electrode mixture layer is formed on the positive electrode foil of the positive electrode foil. The negative electrode layer side terminal electrode may have a known configuration.

[0037] (Sealing member) The sealing members 30, 32, 34, 36 cover the periphery of the positive and negative electrode foils 20 and also form an internal space 40 between adjacent bipolar electrodes 60, i.e., in each cell 10. The internal space 40 contains the positive electrode mixture layer 14, the negative electrode mixture layer 12, and the separator 16, and further contains an electrolyte. In the present disclosure, the sealing members 30, 32, 34, 36 prevent the electrolyte contained in the internal space 40 from leaking to the outside. The sealing members 30, 32, 34, 36 can prevent moisture from entering the internal space 40 from the outside of the bipolar battery module 100. The sealing members 30, 32, 34, 36 prevent internal gas generated from the positive electrode mixture layer 14 or the negative electrode mixture layer 12 due to charging, discharging, etc. from leaking to the outside of the bipolar battery module 100.

[0038] Adjacent sealing members are welded to each other. The peripheral edges of the positive and negative electrode foils 20 and the peripheral edges of the separators 16 are each held in a state of being embedded in the sealing members 30. Examples of materials for the sealing members 30, 32, 34, and 36 include polyethylene, polystyrene, acrylonitrile-butadiene-styrene copolymer synthetic resin (ABS resin, modified polypropylene, acrylonitrile-styrene resin, etc.

[0039] (electrolyte) The electrolyte is accommodated in the internal space 40. The electrolyte may include a non-aqueous solvent and a lithium salt. Examples of the lithium salt include LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2. Examples of the non-aqueous solvent include cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers. The electrolyte may include an additive (e.g., lithium bis(oxalato)borate, etc.).

[0040] (Application) The bipolar battery module 100 can be used as a power source for, for example, electric four-wheeled vehicles, electric two-wheeled vehicles, portable devices, and power storage systems. Examples of electric four-wheeled vehicles include battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Examples of electric two-wheeled vehicles include electric motorcycles and electrically assisted bicycles. Examples of portable devices include smartphones, tablet computers, notebook computers, power tools, and video cameras. Examples of power storage systems include home power storage systems, industrial power storage systems, and energy storage systems (ESSs). [Explanation of symbols]

[0041] 10 cell, 12 negative electrode composite layer, 14 positive electrode composite layer, 16 separator, 20 positive and negative electrode foils, 22 negative electrode foil, 24 positive electrode foil, 30 sealing member, 32, 34, 36 liquid injection port sealing member, 40 internal space, 42 liquid injection opening, 50 electrolyte, 60 bipolar electrode, 70 electrode laminate, 100 bipolar battery module, 112 liquid injection nozzle, 114 liquid injection nozzle

Claims

1. an electrode laminate in which a plurality of bipolar electrodes are laminated with separators interposed therebetween, the bipolar electrodes having a positive electrode mixture layer disposed on a positive electrode foil side of positive and negative electrode foils and a negative electrode mixture layer disposed on a negative electrode foil side of positive and negative electrode foils; A sealing member that covers the peripheral portion of the positive and negative electrode foils; Including, A structure in which a plurality of cells are stacked in the stacking direction of the bipolar electrodes, each of the plurality of cells has an internal space in which an electrolyte is accommodated between two of the positive and negative electrode foils adjacent to each other in the stacking direction, and a liquid injection opening for injecting the electrolyte into the internal space is formed by the sealing member in a part of an outer periphery of each cell; a peripheral portion of at least one of the two positive and negative electrode foils is positioned so as to be biased toward an adjacent cell, thereby causing the liquid injection opening in at least some of the plurality of cells to have a shape that spreads toward the adjacent cell.

2. 2 . The bipolar battery module according to claim 1 , wherein the electrolyte injection openings extending toward the adjacent cell are formed at intervals of one or more cells among the plurality of cells.

3. 2. The bipolar battery module according to claim 1, wherein the liquid injection opening extending toward the adjacent cell side is formed by folding the peripheral edge portions of the positive and negative electrode foils in a stepped shape, and a portion closer to an end than the folded portion is covered by the sealing member.

4. 2. The bipolar battery module according to claim 1, wherein the plurality of cells is three or more cells, and the volume of the internal space of at least one of the two cells located outermost in the stacking direction is the smallest among the volumes of the internal spaces of the plurality of cells.

5. 5. The bipolar battery module according to claim 1, wherein the electrolyte injection opening is sealed with the electrolyte contained in the internal space of each of the plurality of cells.

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