Bipolar current collector, bipolar electrode, bipolar battery, and method for manufacturing bipolar current collector

Abstract

The bipolar current collector includes a first metal foil, an adhesive layer, and a second metal foil. The first metal foil has a first main surface and a second main surface. The second main surface is an opposite surface to the first main surface. The bonding layer covers the first main surface. The adhesive layer has electron conductivity. The second metal foil is adhered to the first main surface via the adhesive layer. The second metal foil has a frame-shaped planar shape. The second metal foil is attached along the periphery of the first main surface.

Description

Technical Field

[0001] The present disclosure relates to a bipolar current collector, a bipolar electrode, a bipolar battery, and a method for manufacturing the bipolar current collector. Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-053669 discloses a bipolar current collector. Summary of the invention

[0003] A bipolar current collector is an electrode current collector for a bipolar battery. Conventionally, a bipolar current collector is manufactured by laminating two metal foils. For example, from the perspective of effective resource utilization, it is desired to reduce the amount of metal used.

[0004] The purpose of the present disclosure is to reduce the amount of metal used.

[0005] 1. A bipolar current collector, comprising a first metal foil, an adhesive layer and a second metal foil. The first metal foil has a first main surface and a second main surface. The second main surface is the opposite surface of the first main surface. The adhesive layer covers the first main surface. The adhesive layer has electronic conductivity. The second metal foil is bonded to the first main surface through the adhesive layer. The second metal foil has a frame-like planar shape. The second metal foil is attached along the periphery of the first main surface.

[0006] The second metal foil is frame-shaped, thereby reducing the amount of metal used. In the case where the second metal foil is frame-shaped, it is also considered that the first main surface of the first metal foil is in contact with the electrolyte and there is the possibility of corrosion of the first main surface. However, the adhesive layer covers the first main surface, so the adhesive layer can hinder the contact between the first main surface and the electrolyte. Furthermore, the adhesive layer has conductivity, so that electrons can be conducted in the thickness direction of the bipolar collector. The frame-shaped second metal foil can contribute to the sealing of the bipolar battery. By filling a sealant between the second metal foil (frame) and the first metal foil, it is expected that the sealing will be improved. Assuming that there is no second metal foil (frame), for the adhesive layer, it is required to have adhesion with the sealant. That is, the range of material selection of the adhesive layer and the sealant is narrowed. By having a second metal foil (frame), it is expected that the freedom of material selection will be improved.

[0007] 2. The bipolar current collector according to the above “1” may have the following configuration, for example. The first metal foil includes aluminum, the adhesive layer includes a resin material and a conductive filler, and the second metal foil includes copper.

[0008] In the bipolar current collector described in the above “2”, the amount of copper used can be reduced.

[0009] 3. A bipolar electrode comprising the bipolar current collector according to the above “1” or “2”, a positive electrode layer and a negative electrode layer, wherein the positive electrode layer is disposed on the second main surface, and the negative electrode layer is disposed on the adhesive layer.

[0010] For example, the first main surface of the first metal foil may be the negative electrode side, and the second main surface may be the positive electrode side. Of course, the first main surface may be the positive electrode side, and the second main surface may be the negative electrode side.

[0011] 4. A bipolar battery comprising a plurality of bipolar electrodes, an electrolyte and a seal. The plurality of bipolar electrodes are the bipolar electrodes described in "3" above. The plurality of bipolar electrodes are stacked in the thickness direction. The seal is between two adjacent bipolar electrodes to seal the second main surface and the second metal foil.

[0012] 5. A method for producing a bipolar current collector, comprising the following (a) to (c). (a) Prepare a first metal foil and a second metal foil. (b) An adhesive is applied to one surface of the first metal foil to form an adhesive layer. (c) The second metal foil is attached to the adhesive layer to produce a bipolar current collector. The adhesive layer has electron conductivity. The second metal foil includes a portion having a frame-like planar shape. The second metal foil is attached along the periphery of the first metal foil.

[0013] The following describes an embodiment of the present disclosure (hereinafter may be referred to as "this embodiment") and an example of the present disclosure (hereinafter may be referred to as "this example"). However, this embodiment and this example do not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-restrictive. The technical scope of the present disclosure includes all changes within the meaning and scope equivalent to the description of the claims. For example, it is intended from the outset to extract any configuration from this embodiment and combine them arbitrarily.

[0014] Geometric terms (such as parallel, perpendicular, orthogonal, etc.) should not be interpreted in a strict sense. For example, "parallel" can deviate slightly from "parallel" in the strict sense. Geometric terms can include tolerances, errors, etc. in design, operation, and manufacturing. There are cases where the dimensional relationships in the drawings are inconsistent with the actual dimensional relationships. In order to help readers understand, there are cases where the dimensional relationships in the drawings are changed. For example, there are cases where the length, width, thickness, etc. are changed. There are also cases where part of the structure is omitted.

[0015] Numerical ranges such as "m% to n%" include both the upper limit and the lower limit unless otherwise specified. "m% to n%" means a numerical range of "m% or more and n% or less". "m% or more and n% or less" includes "more than m% and less than n%". BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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. Figure 1 It is a schematic plan view showing an example of a bipolar current collector in this embodiment. Figure 2 yes Figure 1 II-II sectional view. Figure 3 This is a schematic flowchart of the method for producing the bipolar current collector in this embodiment. Figure 4 This is a conceptual diagram showing an example of a production apparatus in this embodiment. Figure 5 It is a schematic plan view showing an example of the first metal foil and the second metal foil. Figure 6 This is a first schematic plan view showing an example of the second metal foil. Figure 7 This is a second schematic plan view showing an example of the second metal foil. Figure 8 It is a schematic cross-sectional view showing an example of a bipolar electrode in this embodiment. Fig. 9 It is a schematic cross-sectional view showing an example of a bipolar battery in this embodiment. Fig.10 is a table showing the evaluation results. DETAILED DESCRIPTION Bipolar current collector

[0017] Figure 1 It is a schematic plan view showing an example of a bipolar current collector in this embodiment. Figure 2 yes Figure 1 II-II cross-sectional view. The bipolar current collector 10 includes a first metal foil 11, an adhesive layer 13 and a second metal foil 12. For convenience, Figure 1 The adhesive layer 13 is not shown in the figure. Figure 2 As shown, the first metal foil 11 has a first main surface 11a and a second main surface 11b. The second main surface 11b is the opposite surface of the first main surface 11a. The adhesive layer 13 covers the first main surface 11a. The second metal foil 12 is bonded to the first main surface 11a through the adhesive layer 13. Figure 1 As shown, the second metal foil 12 has a frame-like planar shape. The second metal foil 12 is attached along the periphery of the first main surface 11a. The width dimension (w) of the second metal foil 12 can be, for example, 1 mm to 50 mm, 1 mm to 30 mm, or 1 mm to 10 mm.

[0018] The area ratio of the portion surrounded by the second metal foil 12 (frame) to the entire area of ​​the first main surface 11a can be, for example, 0.95 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less. The area ratio can be, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. ·First metal foil, second metal foil

[0019] The first metal foil 11 and the second metal foil 12 are different materials from each other. As long as they are different materials from each other, the first metal foil 11 and the second metal foil 12 can include any metal material. For example, the first metal foil 11 and the second metal foil 12 can include at least one selected from aluminum (Al), copper (Cu), nickel (Ni), titanium (Ti), iron (Fe) and stainless steel (SUS).

[0020] The first metal foil 11 may include Al, for example. That is, the first metal foil 11 may be an Al foil. The Al foil in the present embodiment includes a pure Al foil and an Al alloy foil. The Al foil may include, for example, any metal material represented by an alloy number from more than 1000 to more than 8000 described in "JIS H4000". The thickness of the first metal foil 11 may be, for example, 1 μm to 100 μm, 5 μm to 75 μm, or 10 μm to 50 μm.

[0021] The second metal foil 12 may include, for example, Cu. That is, the second metal foil 12 may be a Cu foil. The Cu foil in the present embodiment includes a pure Cu foil and a Cu alloy foil. The Cu foil may include, for example, any metal material represented by an alloy number from more than 1000 to more than 7000 described in "JIS H3100". The thickness of the second metal foil 12 may be, for example, 1 μm to 50 μm, 3 μm to 30 μm, or 5 μm to 10 μm. Adhesive layer

[0022] The adhesive layer 13 has electronic conductivity. The adhesive layer 13 may include, for example, a resin material and a conductive filler. For example, the adhesive layer 13 may include a conductive filler having a mass fraction of 1% to 99% and the remaining resin material. The mass fraction of the conductive filler may be, for example, 5% to 50%, or 10% to 30%.

[0023] The resin material is an adhesive component. The resin material may be resistant to the electrolyte. The resin material may be insoluble in the electrolyte. The resin material may, for example, include at least one selected from olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, epoxy resins, and polyester resins. The resin material may include, for example, a single-component adhesive, a two-component adhesive, etc. In a two-component adhesive, the main agent may include, for example, an olefin resin, etc. The curing agent may include, for example, a compound having an isocyanate group, etc.

[0024] Conductive fillers are conductive components. Conductive fillers may include, for example, carbon particles, metal particles, metal-plated particles, etc. The core of the metal-plated particles may be a solid or hollow resin particle. Conductive fillers may include, for example, at least one selected from carbon black, graphite, vapor-grown carbon fiber, carbon nanotubes, carbon nanofibers, carbon nanospheres, Ni particles, Ni-plated particles, Cu particles, and Cu-plated particles. The particle shape of the conductive filler is arbitrary. The conductive filler may be, for example, spherical, flaky, rod-shaped, needle-shaped, fibrous, etc.

[0025] The particle size of the conductive filler can be, for example, 0.1 μm to 10 μm, 0.5 μm to 5 μm, or 1 μm to 3 μm. "Particle size" represents the average value of the maximum Ferry diameter in the particle image. The average value is calculated based on the measurement results of more than 10 times. The ratio of the thickness of the adhesive layer 13 to the particle size of the conductive filler can be, for example, 0.5 to 2, or 0.8 to 1.2. The thickness of the adhesive layer 13 can be, for example, 1 μm to 10 μm, 1 μm to 5 μm, or 2 μm to 4 μm. By having a thickness of the adhesive layer 13 of more than 2 μm, it is expected that the resistance to permeation of the electrolyte will be improved. Through resistance

[0026] The through resistance represents the resistance when electrons flow through the first metal foil 11 and the adhesive layer 13 in the thickness direction. The through resistance of the bipolar current collector 10 can be, for example, 150 mΩ or less. The through resistance can also be, for example, 125 mΩ or less, 100 mΩ or less, or 75 mΩ or less. The through resistance can be, for example, 10 mΩ or more, or 50 mΩ or more. Method for manufacturing bipolar current collector

[0027] Figure 3 This is a schematic flow chart of the method for manufacturing the bipolar current collector in the present embodiment. The "method for manufacturing the bipolar current collector in the present embodiment" may be abbreviated as "the present manufacturing method". The present manufacturing method includes "(a) preparation of metal foil", "(b) formation of adhesive layer" and "(c) bonding". In addition, Figure 3 The order is just an example. For example, multiple steps can also be performed simultaneously. For example, multiple steps can also be performed one after the other. Figure 4 2 is a conceptual diagram showing an example of a manufacturing apparatus in the present embodiment. The manufacturing apparatus 200 can implement the present manufacturing method. The bipolar current collector 10 can be manufactured by, for example, a roll-to-roll method. Figure 4 The arrows in the figure indicate the conveying direction of the workpiece. (a) Preparation of metal foil

[0028] Figure 5 1 is a schematic plan view showing an example of the first metal foil and the second metal foil. The present manufacturing method includes preparing the first metal foil 11 and the second metal foil 12. As the first metal foil 11, for example, a strip-shaped Al foil can be prepared.

[0029] The second metal foil 12 is prepared in a manner including a portion having a frame-like plane shape. In the second metal foil 12, the portion having a frame-like plane shape may be single or multiple. For example, the second metal foil 12 may be manufactured by punching. For example, a strip-shaped Cu foil may be prepared. For example, a punching process may be performed at a certain interval in the length direction of the strip-shaped Cu foil. The punched portion 12a may be reused in the manufacture of the Cu foil, for example.

[0030] As long as the punching process is performed so as to form a frame-shaped portion, the planar shape of the punched portion 12a (hole) is arbitrary. The planar shape of the punched portion 12a may be, for example, a rectangular shape. Figure 6 1 is a first schematic plan view showing an example of the second metal foil. The planar shape of the punched portion 12a may be, for example, an elliptical shape, a circular shape, or the like. Figure 7 2 is a second schematic plan view showing an example of the second metal foil. For example, the metal foil may remain so as to bridge two sides (frames) facing each other. (b) Formation of adhesive layer

[0031] The manufacturing method includes applying the adhesive 3 to one side (first main side 11a) of the first metal foil 11 to form the adhesive layer 13. For example, the adhesive 3 can be prepared by mixing a main agent, a curing agent and a conductive filler. The coating method is arbitrary. For example, Figure 4 As shown, the adhesive 3 is applied to the first metal foil 11 by a gravure roll 201. The adhesive 3 can be dried by a drying oven 202, for example. (c) Fitting

[0032] The manufacturing method includes attaching the second metal foil 12 to the adhesive layer 13 to manufacture the bipolar current collector 10. For example, the bonding can be performed by dry lamination. For example, the second metal foil 12 can be attached to the first metal foil 11 by using a hot roller 203. The second metal foil 12 is attached along the periphery of the first metal foil 11 (first main surface 11a).

[0033] The bipolar current collector 10 may be cut in accordance with the electrode shape. The cutting may be performed before or after the positive electrode layer 21 and the negative electrode layer 22 are formed. Figures 5 to 7 The one-dot chain line indicates an example of a cutting line. Bipolar Electrode

[0034] Figure 8 1 is a schematic cross-sectional view showing an example of a bipolar electrode in the present embodiment. The bipolar electrode 20 is an electrode for a bipolar battery. The bipolar electrode 20 includes a bipolar current collector 10, a positive electrode layer 21, and a negative electrode layer 22. The positive electrode layer 21 is arranged on the second main surface 11b. "On the second main surface 11b" can also be referred to as the surface of the second main surface 11b. The same also applies to "on the adhesive layer 13" described later.

[0035] The positive electrode layer 21 includes a positive electrode composite material. The positive electrode composite material may include, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode active material may include, for example, lithium nickel composite oxide, lithium iron phosphate, etc. The conductive material may include, for example, carbon black, etc. The binder may include polyvinylidene fluoride, etc. The thickness of the positive electrode layer 21 may be, for example, 10 μm to 500 μm, 50 μm to 300 μm, or 100 μm to 200 μm.

[0036] The negative electrode layer 22 is arranged on the adhesive layer 13. The negative electrode layer 22 may have a larger area than the positive electrode layer 21. The ratio of the area of ​​the negative electrode layer 22 to the area of ​​the positive electrode layer 21 may be, for example, 1.05 to 1.15. The negative electrode layer 22 may extend in a manner covering a portion of the second metal foil 12. The negative electrode layer 22 includes a negative electrode composite material. The negative electrode composite material may include, for example, a negative electrode active material, a conductive material, and a binder. The negative electrode active material may include, for example, graphite, silicon, silicon oxide, etc. The conductive material may include, for example, carbon black, etc. The binder may include styrene-butadiene rubber, carboxymethyl cellulose, etc. The thickness of the negative electrode layer 22 may be, for example, 10 μm to 500 μm, 50 μm to 300 μm, or 100 μm to 200 μm. Bipolar battery

[0037] Fig. 9 1 is a schematic cross-sectional view showing an example of a bipolar battery in the present embodiment. The bipolar battery 100 includes a bipolar electrode 20, an electrolyte (not shown) and a seal 40. The bipolar battery 100 may include, for example, an outer casing (not shown). The outer casing may contain the bipolar electrode 20 and the electrolyte. The outer casing may be, for example, a bag made of a metal foil laminate film, a housing made of metal, or the like.

[0038] The electrolyte is a liquid electrolyte. The electrolyte may include, for example, a supporting salt and a solvent. The supporting salt may include, for example, LiPF 6The solvent may include, for example, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc. The electrolyte may further include any additive.

[0039] A plurality of bipolar electrodes 20 are stacked in the thickness direction (Z direction). The bipolar battery 100 may further include a separator 30. The separator 30 is disposed between the positive electrode layer 21 and the negative electrode layer 22. The separator 30 separates the positive electrode layer 21 from the negative electrode layer 22. The separator 30 may include, for example, a porous film made of resin.

[0040] The seal 40 seals the second main surface 11b and the second metal foil 12 (frame) between two adjacent bipolar electrodes 20. In the XY plane, the seal 40 surrounds the positive electrode layer 21 and the negative electrode layer 22. The seal 40 may include, for example, a first seal 41 (primary seal) and a second seal 42 (secondary seal). The first seal 41 may seal the second main surface 11b and the second metal foil 12. The second seal 42 may further seal the outside of the first seal 41. The seal 40 may include, for example, a resin material. The seal may include, for example, at least one selected from polypropylene, polyphenylene sulfide, and modified polyphenylene ether. The second seal 42 may be the same material as the first seal 41, or a different material. Sample preparation No.1

[0041] Prepare the following materials.

[0042] First metal foil 11: Al foil Second metal foil 12: Cu foil (punching completed, punched portion 12a: rectangular shape) Main agent: olefin resin Curing agent: isocyanate compound Conductive filler: Ni-plated particles

[0043] The adhesive 3 is prepared by mixing the main agent, the curing agent and the conductive filler. Figure 4 ) are provided with a first metal foil 11, a second metal foil 12 and an adhesive 3. The bipolar current collector 10 is manufactured under the following conditions.

[0044] Production line speed (workpiece conveying speed): 15m / min Gravure roller 201: Elongate, 75 lines The set temperature of drying oven 202: 150℃ Surface temperature of hot roller 203: 90°C The nip pressure of the hot roller 203: 0.45 MPa No.2

[0045] The bipolar current collector 10 was produced in the same manner as in No. 1 except that a Cu foil (unprocessed product, without pores) was used as the second metal foil 12 . evaluate

[0046] Fig.10 is a table showing the evaluation results. Fig.10 The "standard" and "target" are values ​​relative to the sample of this experiment. No.1 (frame-shaped Cu foil) shows the same through-resistance as No.2 (normal Cu foil). The quality (minimum thickness, average thickness) of the adhesive layer 13 of No.1 is also sufficient. Therefore, it can be expected to have sufficient resistance to penetration of the electrolyte. In No.1, the negative electrode composite material is coated on the adhesive layer 13, and the coating properties of the composite material are also evaluated. The coating properties of No.1 are equivalent to those of No.2.

Claims

1. A bipolar current collector comprising: a first metal foil; an adhesive layer; and The second metal foil, The first metal foil has a first main surface and a second main surface, The second main surface is the opposite surface of the first main surface, The adhesive layer covers the first main surface, The adhesive layer has electronic conductivity, The second metal foil is bonded to the first main surface via the adhesive layer. The second metal foil has a frame-like planar shape, and The second metal foil is attached along the periphery of the first main surface.

2. The bipolar current collector according to claim 1, wherein The first metal foil comprises aluminum, The adhesive layer comprises a resin material and a conductive filler, and The second metal foil includes copper.

3. A bipolar electrode comprising: The bipolar current collector according to claim 1 or 2; a positive electrode layer; and Negative electrode layer, The positive electrode layer is disposed on the second main surface, and The negative electrode layer is disposed on the adhesive layer.

4. A bipolar battery comprising: multiple bipolar electrodes; electrolyte; and Seals, The plurality of bipolar electrodes are the bipolar electrodes according to claim 3, A plurality of the bipolar electrodes are stacked in the thickness direction, and The sealing member seals between the second main surface and the second metal foil between two adjacent bipolar electrodes.

5. A method for manufacturing a bipolar current collector, comprising: (a) preparing a first metal foil and a second metal foil; (b) applying an adhesive to one side of the first metal foil to form an adhesive layer; and (c) attaching the second metal foil to the adhesive layer to produce a bipolar current collector, wherein the adhesive layer has electronic conductivity. The second metal foil includes a portion having a frame-like planar shape, and The second metal foil is attached along the periphery of the first metal foil.

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