Bipolar battery module

Abstract

A bipolar battery module of the present disclosure has a structure in which a plurality of battery cells are stacked in a stacking direction of bipolar electrodes. Each of the plurality of battery cells has an internal space in which an electrolyte solution is accommodated between two positive and negative electrode foils that are adjacent in the stacking direction. In a portion of the outer peripheral portion of each battery cell, a liquid injection opening for injecting an electrolyte into the internal space is formed by a sealing member. The liquid injection openings in at least some of the battery cells have a shape that expands toward the adjacent battery cell side as the peripheral edge of at least one of the two positive and negative electrode foils is disposed toward the adjacent battery cell side.

Description

Technical Field

[0001] The present disclosure relates to bipolar battery modules. Background Art

[0002] Japanese Patent Laid-Open No. 2022-16904 discloses a storage module having at least one electrode unit. The storage module disclosed in Japanese Patent Laid-Open No. 2022-16904 has the following structure. A spacer that maintains a gap between a pair of current collectors in the electrode unit is joined to a plurality of spacer components arranged along the outer periphery of the current collector. In this way, the plurality of spacer components are formed into a frame shape surrounding the active material layer. A sealing component that seals the seam is provided at the exposed portion of the joints between the plurality of spacer components on the outer peripheral surface of the frame-shaped spacer. The outer peripheral surface of the spacer has a first area covered by the sealing component and a second area not covered by the sealing component. Summary of the invention

[0003] Figure 6 An example of a liquid injection opening of a battery cell in a conventional bipolar battery module is schematically shown. Figure 6 In the bipolar battery shown, the electrolyte is injected into the internal space 40P from the opening of each battery 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 battery cell, which greatly affects the injection of the electrolyte.

[0004] 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 and 14P is set thin. If the thickness of the positive and negative electrode layers 12P and 14P is reduced, the total thickness of the separator 16P and the positive and negative electrode layers 12P and 14P becomes smaller, and the height of the internal space of the battery cell becomes lower. Therefore, the height (thickness direction interval) H of the liquid injection port also becomes lower, and the liquid injection property is reduced.

[0005] An object of the present disclosure is to provide a bipolar battery module having improved injection properties of an electrolyte solution into an internal space of a battery cell.

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

[0007] <1> A bipolar battery module, comprising:

[0008] An electrode stack, formed by stacking a plurality of bipolar electrodes with a separator therebetween, each bipolar electrode comprising a positive electrode composite material layer disposed on the positive electrode foil side of the positive and negative electrode foils and a negative electrode composite material layer disposed on the negative electrode foil side of the positive and negative electrode foils; and

[0009] A sealing member covers the peripheral edge of the positive and negative electrode foils,

[0010] The bipolar battery module has a structure in which a plurality of battery cells are stacked in a stacking direction of the bipolar electrodes.

[0011] Each of the plurality of battery cells has an internal space for storing electrolyte between two of the positive and negative electrode foils adjacent to each other in the stacking direction.

[0012] In a part of the outer periphery of each battery cell, an injection opening for injecting the electrolyte into the internal space is formed by the sealing member.

[0013] The liquid injection opening in at least a part of the plurality of battery cells has a shape that expands toward the adjacent battery cell due to the peripheral edge portion of at least one of the two positive and negative electrode foils being arranged toward the adjacent battery cell.

[0014] <2> exist <1> In the bipolar battery module described,

[0015] The liquid injection openings are formed in the plurality of battery cells at intervals of one or more battery cells so as to expand toward the adjacent battery cells.

[0016] <3> exist <1> or <2> In the bipolar battery module described,

[0017] The peripheral edge portions of the positive and negative electrode foils are bent in a step-like manner with respect to the liquid injection opening that expands toward the adjacent battery cell side.

[0018] The portion closer to the distal end than the bent portion is covered by the sealing member.

[0019] <4> exist <1> to <3> In any one of the bipolar battery modules described in

[0020] The plurality of battery cells are three or more battery cells, and the volume of the internal space of at least one of the two battery cells located outermost in the stacking direction is the smallest among the volumes of the internal spaces of the plurality of battery cells.

[0021] <5> exist <1> to <4> In any one of the bipolar battery modules described in

[0022] The liquid injection opening is sealed in a state where the electrolyte is accommodated in the internal space of each of the plurality of battery cells.

[0023] According to the present disclosure, a bipolar battery module is provided in which the injection property of an electrolyte into the internal space of a battery cell is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0025] Figure 1 This is a schematic diagram showing an example of a bipolar battery module according to the present disclosure.

[0026] Figure 2 It is shown Figure 1 A partial schematic cross-sectional view of a portion of the AA line section.

[0027] Figure 3 This is a partial schematic cross-sectional view showing an example of a state in which the liquid injection opening is sealed after the electrolyte is injected into the internal space of the battery cell from the liquid injection opening.

[0028] Figure 4 It is shown Figure 1 A partial schematic cross-sectional view of a portion of the BB line cross section.

[0029] Figure 5 This is a partial schematic cross-sectional view showing another example of the liquid injection opening in the bipolar battery module according to the present disclosure.

[0030] Figure 6 This is a partial schematic cross-sectional view showing an example of a liquid injection opening of a battery cell in a conventional bipolar battery module. DETAILED DESCRIPTION

[0031] In the present disclosure, the numerical range expressed by "to" means a range including the numerical values ​​recorded before and after "to" as the minimum value and the maximum value, respectively. In the numerical range recorded in stages in the present disclosure, the upper limit value recorded in a certain numerical range can also be replaced by the upper limit value of the numerical range recorded in other stages. The lower limit value recorded in a certain numerical range can also be replaced by the lower limit value of the numerical range recorded in other stages. In the present disclosure, a combination of two or more preferred methods is a more preferred method. In the present disclosure, the term "process" is not only an independent process, but also is included in this term as long as the expected purpose of the process is achieved, even if it cannot be clearly distinguished from other processes.

[0032] Hereinafter, the embodiment of the bipolar battery module of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are added to the same or equivalent parts and the description is appropriately omitted. In addition, in the drawings, the same or equivalent parts, such as battery cells 10A, 10B, 10C, 10D, and 10E, are sometimes collectively referred to as battery cells 10.

[0033] In the present disclosure, the invention is not limited to a method in which an electrolyte is contained in the internal space of each battery cell and sealed, but also includes a method in which an electrolyte is contained in the internal space of each battery cell and sealed before being referred to as a bipolar battery module.

[0034] Figure 1 1 is a schematic diagram showing an example of a bipolar battery module according to the present disclosure. A plurality of liquid injection nozzles 112 and 114 are provided on an exterior body 120 . Figure 2 It is shown Figure 1 A partial schematic cross-sectional view of a portion of the AA line section in FIG. The bipolar battery module 100 includes an electrode stack 70 formed by stacking a plurality of bipolar electrodes 60 with a separator 16 interposed therebetween, and a sealing member 30 covering the peripheral edge of a positive and negative electrode foil (current collector) 20. The positive and negative electrode foil 20 is formed by bonding a negative electrode foil 22 and a positive electrode foil 24.

[0035] Each bipolar electrode 60 has a structure in which a positive electrode composite material layer 14 is arranged on the positive electrode foil 24 side of the positive and negative electrode foils 20 , and a negative electrode composite material layer 12 is arranged on the negative electrode foil 22 side.

[0036] The bipolar battery module 100 has a structure in which a plurality of battery cells 10 are stacked in the stacking direction of each bipolar electrode 60. Each battery cell 10 has an internal space 40 for storing electrolyte between two positive and negative electrode foils 20, 20 adjacent to each other in the stacking direction of the bipolar electrodes 60. An injection opening 42 for injecting electrolyte into the internal space 40 is formed in a portion of the outer periphery of each battery cell 10 by a sealing member 30. Figure 2 In FIG. 1 , the liquid injection opening 42B of the battery cell 10B is shown.

[0037] In the injection opening 42B of the battery cell 10B, the peripheral edge of the positive and negative electrode foil 20C (the portion of the positive and negative electrode foil 20C where the negative electrode composite material layer 12B and the positive electrode composite material layer 14C are not formed) is bent in a step-like manner. The portion of the positive and negative electrode foil 20C closer to the end than the bent portion is covered by the sealing member 30C. On the other hand, the end of the separator 16B is welded to the sealing member 30B covering the peripheral edge of the positive and negative electrode foil 20B.

[0038] The sealing component 30C at the end of the positive and negative electrode foil 20C contacts the positive and negative electrode foil 20D of the adjacent battery cell 10C of the battery cell 10B. The positive and negative electrode foils 20C and 20D are not in direct contact with each other, thereby preventing short circuits. The peripheral edge portions of the positive and negative electrode foils 20C are bent in a step-like manner and are arranged toward the adjacent battery cell 10C side, and the injection opening 42B is expanded toward the adjacent battery cell 10C side. With such a structure, it is easy to inject electrolyte into the internal space of the battery cell 10B from the injection opening 42B (sometimes referred to as the "expanded opening" in this specification).

[0039] In the bipolar battery module involved in the present disclosure, in the liquid injection opening 42B of the battery cell 10B, the peripheral edge of at least one of the two positive and negative electrode foils 20B and 20C arranged opposite to each other may be arranged toward the adjacent battery cell side. For example, the peripheral edge of the positive and negative electrode foil 20B may also be arranged toward the adjacent battery cell 10A side. Alternatively, the peripheral edge of the positive and negative electrode foils 20B and 20C may be arranged toward the adjacent battery cell 10A and 10C side, respectively, so that the liquid injection opening 42B is further enlarged.

[0040] The liquid injection opening 42B of the battery cell 10B is formed at the same Figure 1 The position corresponds to the injection nozzle 112 of the bipolar battery module 100 shown. The electrolyte is supplied through the injection nozzle 112, and the electrolyte is injected into the internal space of the battery cell 10B from the injection opening 42B.

[0041] The electrolyte injected into the internal space of the battery cell 10B passes through the negative electrode composite layer 12 side, further passes through the separator 16B, and also permeates to the positive electrode composite layer 14 side.

[0042] Figure 3 1 is a partial schematic cross-sectional view showing an example of a state in which the injection opening 42B is sealed after the electrolyte is injected into the internal space 40B of the battery cell 10B from the injection opening 42B. The electrolyte 50 is injected into the internal space 40B of the battery cell 10B through the injection opening 42B. After the injection, the injection opening 42B is sealed by the injection port sealing components 32, 34, and 36. As a result, the electrolyte 50 injected into the interior of the battery cell 10B remains in the area surrounded by the positive and negative electrode foils 20B and 20C and the sealing component 36.

[0043] Figure 4 It is shown Figure 1 A schematic cross-sectional view of a portion of the BB line section in FIG. Figure 4, the liquid injection opening 42D in the battery cell 10D is shown. The peripheral edge portions of the positive and negative electrode foils 20E are bent in a step-like shape and are arranged toward the adjacent battery cell 10E. Therefore, the liquid injection opening 42D of the battery cell 10D also has a shape that expands toward the adjacent battery cell 10E side. The liquid injection opening 42D of the battery cell 10D is formed at a position corresponding to the liquid injection nozzle 114 of the bipolar battery module. The electrolyte is supplied through the liquid injection nozzle 114, thereby injecting the electrolyte into the internal space 40D of the battery cell 10D from the liquid injection opening 42D. Similar to the liquid injection opening 42B, after the liquid is injected, the liquid injection opening 42D is sealed using a liquid injection port sealing component (not shown).

[0044] In the bipolar battery module 100 involved in the present disclosure, Figure 2 as well as Figure 4 As shown, injection openings (enlarged openings) 42B and 42D are formed at intervals between each battery cell and expand toward the adjacent battery cell. In the bipolar battery module involved in the present disclosure, the expanded openings may be formed at intervals of more than one battery cell, or the injection openings of each battery cell 10 may have a shape that expands toward the adjacent battery cell at different positions on the outer periphery.

[0045] The battery cells 10A, 10C, and 10E have injection openings (not shown) at positions different from the injection openings 42B and 40D of the battery cells 10B and 10D, for example, on the opposite side. The injection openings of each of the battery cells 10A, 10C, and 10E also have a shape in which the peripheral edge of the positive and negative electrode foils expands toward the adjacent battery cell side, thereby improving the injection properties of the electrolyte. In each of the internal spaces 40A, 40C, and 40E of the battery cells 10A, 10C, and 10E, the electrolyte is injected from the corresponding injection nozzles (not shown) through the injection openings and then sealed.

[0046] The bipolar battery module 100 functions as a storage battery by injecting an electrolyte into the internal space of each battery cell 10 and sealing the injection opening.

[0047] Modification 1

[0048] Figure 5 This is a partial schematic cross-sectional view showing another example of the liquid injection opening in the bipolar battery module involved in the present disclosure. The peripheral edge portions of the positive and negative electrode foils 20B of the battery cell 10B are arranged to be inclined toward the adjacent battery cell 10A. In this way, even if the peripheral edge portions of the positive and negative electrode foils of each battery cell are not bent in a step-like manner, but are arranged to be inclined toward the adjacent battery cell, the liquid injection opening 42B is enlarged, and the liquid injection property is improved.

[0049] Modification 2

[0050] The volume of the internal space of at least one of the two battery cells located on the outermost sides in the stacking direction (sometimes referred to as "outermost battery cells" in the present disclosure) in a structure in which more than three battery cells are stacked can also be minimized among the volumes of the internal spaces of the other battery cells.

[0051] In a conventional bipolar battery module, the battery cells are stacked on top of each other to maintain the interior of the battery cells in a depressurized state, so the degree of depressurization inside each battery cell cannot be monitored from the outside in the module state.

[0052] On the other hand, for example, Figure 2 In the case where the battery cells 10A and 10E are respectively the outermost battery cells, the volume of the inner space 40A of at least one of the outermost battery cells, for example, the battery cell 10A, is minimized. When the pressure inside the battery cell rises due to the inflow of external gas, the inner pressure of the outermost battery cell 10A, in which the inner space 40A is narrowest, rises the most, and it is possible to determine whether the internal pressure is abnormal by visual inspection and measurement. For example, in the outermost battery cell 10A, there is a flat surface portion of the outer casing exposed, and by abutting the pressure sensor against the flat surface portion, the pressure inside the battery cell can be detected. Thus, it is not necessary to monitor the internal pressure of all the battery cells in the bipolar battery module.

[0053] The method of narrowing the inner space of the outermost battery cell 10A is not particularly limited. Figure 2 As shown, the following methods can be mentioned.

[0054] (i) A method of bending the positive and negative electrode foils 20A to make the sealing member 30A longer than other battery cells and narrow the internal space 40A

[0055] (ii) A method of placing a spacer (not shown) between the positive and negative electrode foils 20A and 20B of the outermost battery cell 10A to narrow the internal space 40A

[0056] (iii) A method of making the area of ​​the positive electrode composite material layer 14A and the negative electrode composite material layer 12A larger than the area of ​​the positive electrode composite material layer and the negative electrode composite material layer of other battery cells to narrow the internal space 40A.

[0057] Hereinafter, the components of the bipolar battery module according to the present disclosure will be described in detail, but the components of the bipolar battery module according to the present disclosure are not limited to the following description.

[0058] Electrode stack

[0059] The electrode stack 70 is, for example, a rectangular parallelepiped object. The electrode stack 70 includes a plurality of bipolar electrodes 60 stacked with a separator 16 therebetween. Specifically, the electrode stack 70 includes a plurality of bipolar electrodes 60, a plurality of separators 16, a positive electrode layer side terminal electrode (not shown), and a negative electrode layer side terminal electrode (not shown). A plurality of bipolar electrodes 60 and a plurality of separators 16 are alternately stacked along the axial direction. The positive electrode layer side terminal electrode is stacked with a separator for the outermost bipolar electrode located on one side of the stacking direction among the plurality of bipolar electrodes 60. The negative electrode layer side terminal electrode is stacked with a separator for the outermost bipolar electrode located on the other side of the stacking direction among the plurality of bipolar electrodes.

[0060] Bipolar Electrode

[0061] The bipolar electrode 60 includes positive and negative electrode foils 20, a positive electrode composite material layer 14, and a negative electrode composite material layer 12. The peripheral edge portions of the positive and negative electrode foils 20 are welded to the sealing member 30. The positive electrode composite material layer 14 is formed on the positive electrode foil 24 side of the positive and negative electrode foils 20. The negative electrode composite material layer 12 is formed on the negative electrode foil 22 side of the positive and negative electrode foils 20. The bipolar electrode 60 may also be a known structure.

[0062] The positive and negative electrode foils 20 supply current to the positive electrode composite layer 14 and the negative electrode composite layer 12 during discharge or charge of the bipolar battery module 100. Examples of the positive and negative electrode foils 20 include aluminum foil, copper foil, nickel foil, titanium foil, and stainless steel foil.

[0063] A coating layer may be formed on the surface of the positive and negative electrode foils 20 by a known method (eg, plating, spraying, etc.). The thickness of the positive and negative electrode foils 20 may be 1 μm to 100 μm.

[0064] The positive electrode composite material layer 14 contains a positive electrode layer active material that can absorb and release charge carriers (for example, a lithium composite metal oxide with a layered rock salt structure, a metal oxide with a spinel structure, a polyvinylidene fluoride compound, etc.). The positive electrode composite material layer 14 may also contain a conductive auxiliary agent (for example, carbon nanofibers, etc.) for improving electronic conductivity, a binder (for example, polyvinylidene fluoride, etc.), an electrolyte supporting salt (lithium salt) for improving ion conductivity, a polymer electrolyte, and an additive (for example, propylene trifluorocarbonate, a filler as a reinforcing material, etc.) as needed. The thickness of the positive electrode composite material layer 14 may also be 2μm to 500μm.

[0065] The negative electrode composite material layer 12 contains a negative electrode layer active material that can absorb and release charge carriers (such as carbon (such as natural graphite, artificial graphite), compounds that can be alloyed with lithium (such as silicon, tin, etc.), etc.). The negative electrode composite material layer 12 may also contain a conductive auxiliary agent (such as acetylene black, etc.) for improving electronic conductivity, a binder (such as polyvinylidene fluoride, etc.), an electrolyte supporting salt (lithium salt) for improving ion conductivity, a polymer electrolyte, and additives (such as trifluoropropylene carbonate, fillers as reinforcing materials, etc.) as needed. The thickness of the negative electrode composite material layer 12 can also be 2μm to 500μm. The thickness of the negative electrode composite material layer 12 can be the same as or different from the thickness of the positive electrode composite material layer 14. Figure 2 In the illustrated embodiment, the length of the negative electrode composite material layer 12 is longer than the length of the positive electrode composite material layer 14 .

[0066] Partition

[0067] The separator 16 maintains the spacing between the positive electrode composite material layer 14 and the negative electrode composite material layer 12 to prevent contact short circuit, and allows charge carriers such as lithium ions (such as lithium ions) to pass through. The peripheral edge of the separator 16 is welded to the sealing component 30. The separator 16 is held by the sealing component 30. As the separator 16, for example, a porous resin sheet or a non-woven fabric can be cited. As the material of the porous resin sheet, for example, polyolefins (polypropylene, polyethylene, etc.) can be cited. As the material of the non-woven fabric, for example, polypropylene, polyethylene terephthalate, methyl cellulose, etc. can be cited. The separator can also be a known structure.

[0068] Positive electrode side terminal electrode

[0069] The positive electrode layer side terminal electrode has positive and negative electrode foils and a positive electrode composite material layer. The positive electrode composite material layer is formed on the negative electrode foil of the positive and negative electrode foils. The positive electrode layer side terminal electrode may also have a known structure.

[0070] Negative electrode side terminal electrode

[0071] The negative electrode layer side terminal electrode has positive and negative electrode foils and a negative electrode composite material layer. The negative electrode composite material layer is formed on the positive electrode foil of the positive and negative electrode foils. The negative electrode layer side terminal electrode may also have a known structure.

[0072] Sealing parts

[0073] In addition to covering the peripheral portions of the positive and negative electrode foils 20, the sealing components 30, 32, 34, and 36 form an internal space 40 between adjacent bipolar electrodes 60, that is, between each battery cell 10. In the internal space 40, the positive electrode composite material layer 14, the negative electrode composite material layer 12, the separator 16, and further the electrolyte are contained. In the present disclosure, the sealing components 30, 32, 34, and 36 prevent the electrolyte contained in the internal space 40 from leaking to the outside. The sealing components 30, 32, 34, and 36 can prevent moisture from invading the internal space 40 from the outside of the bipolar battery module 100. The sealing components 30, 32, 34, and 36 prevent the internal gas generated from the positive electrode composite material layer 14 or the negative electrode composite material layer 12 due to charging and discharging, etc. from leaking to the outside of the bipolar battery module 100.

[0074] Adjacent sealing members are welded to each other, and the peripheral edge portions of the positive and negative electrode foils 20 and the peripheral edge portions of the separator 16 are held in a state of being buried in the sealing member 30 .

[0075] Examples of the material of the sealing members 30, 32, 34, and 36 include polyethylene, polystyrene, acrylonitrile-butadiene-styrene copolymer resin (ABS resin, modified polypropylene, acrylonitrile-styrene resin, and the like.

[0076] Electrolyte

[0077] The electrolyte is contained in the internal space 40. The electrolyte may also contain a non-aqueous solvent and a lithium salt. Examples of lithium salts include LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2. Examples of non-aqueous solvents include cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers. The electrolyte may also contain additives (e.g., lithium bis(oxalatoborate)).

[0078] use

[0079] The bipolar battery module 100 can be used, for example, as a power source for electric four-wheeled vehicles, electric two-wheeled vehicles, portable devices, and power storage systems. Examples of electric four-wheeled vehicles include BEV: battery electric vehicles, PHEV: plug-in hybrid electric vehicles, and HEV: hybrid electric vehicles. Electric two-wheeled vehicles include electric motorcycles or electric power-assisted vehicles. Examples of portable devices include smartphones, tablet computers, notebook computers, power tools, video cameras, and the like. Examples of power storage systems include household power storage systems, industrial power storage systems, and power storage systems (ESS: Energy Storage System).

Claims

1. A bipolar battery module, comprising: An electrode stack, formed by stacking a plurality of bipolar electrodes with a separator therebetween, each bipolar electrode comprising a positive electrode composite material layer disposed on the positive electrode foil side of the positive and negative electrode foils and a negative electrode composite material layer disposed on the negative electrode foil side of the positive and negative electrode foils; and A sealing member covers the peripheral edge of the positive and negative electrode foils, The bipolar battery module has a structure in which a plurality of battery cells are stacked in a stacking direction of the bipolar electrodes. Each of the plurality of battery cells has an internal space for storing electrolyte between two of the positive and negative electrode foils adjacent to each other in the stacking direction. In a part of the outer periphery of each battery cell, an injection opening for injecting the electrolyte into the internal space is formed by the sealing member. The liquid injection opening in at least a part of the plurality of battery cells has a shape that expands toward the adjacent battery cell due to the peripheral edge portion of at least one of the two positive and negative electrode foils being arranged toward the adjacent battery cell.

2. The bipolar battery module according to claim 1, wherein: The liquid injection openings are formed in the plurality of battery cells at intervals of one or more battery cells so as to expand toward the adjacent battery cells.

3. The bipolar battery module according to claim 1, wherein: The peripheral edge portions of the positive and negative electrode foils are bent in a step-like manner with respect to the liquid injection opening that expands toward the adjacent battery cell side. The portion closer to the distal end than the bent portion is covered by the sealing member.

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

5. The bipolar battery module according to any one of claims 1 to 4, wherein: The liquid injection opening is sealed in a state where the electrolyte is accommodated in the internal space of each of the plurality of battery cells.

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