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

Abstract

To reduce the amount of usage of metal.SOLUTION: The bipolar collector includes a first metal foil, an adhesive layer, and a second metal foil. The first metal foil includes a first main surface and a second main surface. The second main surface is the opposite surface to the first main surface. The adhesive layer covers the first main surface. The adhesive layer has an electron conduction property. The second metal foil is attached to the first main surface by the adhesive layer. The second metal foil has a frame-like flat surface. The second metal foil is attached along the periphery of the first main surface.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A bipolar current collector is an electrode current collector for a bipolar battery. Conventionally, a bipolar current collector has been manufactured by laminating two kinds of metal foils. For example, from the viewpoint of effective utilization of resources and the like, reduction of the amount of metal used is desired.

[0005] An object of the present disclosure is to reduce the amount of metal used.

Means for Solving the Problems

[0006] 1. 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 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 adhered to the first main surface by 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.

[0007] The frame-like structure of the second metal foil reduces the amount of metal used. When the second metal foil is frame-like, there is a possibility that the first main surface of the first metal foil may corrode due to contact with the electrolyte. However, since the adhesive layer covers the first main surface, the adhesive layer can prevent contact between the first main surface and the electrolyte. Furthermore, because the adhesive layer is conductive, electrons can be conducted in the thickness direction of the bipolar current collector. The frame-like second metal foil can contribute to the sealing performance of the bipolar battery. Improved sealing performance is expected by filling the space between the second metal foil (frame) and the first metal foil with a sealing material. If the second metal foil (frame) is absent, adhesion between the adhesive layer and the sealing material is required. This narrows the range of material selection options for the adhesive layer and sealing material. The presence of the second metal foil (frame) is expected to increase the freedom of material selection.

[0008] 2. The bipolar current collector described in "1" above may include, for example, the following configuration: The first metal foil contains aluminum. The adhesive layer contains a resin material and a conductive filler. The second metal foil contains copper.

[0009] In the bipolar current collector described in "2" above, the amount of copper used can be reduced.

[0010] 3. The bipolar electrode includes the bipolar current collector, positive electrode layer and negative electrode layer described in "1" or "2" above. The positive electrode layer is located on the second main surface. The negative electrode layer is located on the adhesive layer.

[0011] For example, the first main surface of the first metal foil may be on the negative electrode side and the second main surface may be on the positive electrode side. Of course, a configuration in which the first main surface is on the positive electrode side and the second main surface is on the negative electrode side is also conceivable.

[0012] 4. A bipolar battery includes a plurality of bipolar electrodes, an electrolyte, and a sealing material. Each of the plurality of bipolar electrodes is the bipolar electrode described in "3" above. The plurality of bipolar electrodes are stacked in the thickness direction. The sealing material seals between the second main surface and the second metal foil between two adjacent bipolar electrodes.

[0013] 5. The method for manufacturing a bipolar current collector includes (a) to (c) below. (a) Prepare the first metal foil and the second metal foil. (b) An adhesive layer is formed by applying an adhesive to one side of the first metal foil. (c) A bipolar current collector is manufactured by attaching a second metal foil to the adhesive layer. The adhesive layer is electrically conductive. 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.

[0014] Embodiments of the present disclosure (which may be abbreviated as "Embodiments") and examples of the present disclosure (which may be abbreviated as "Examples") are described below. However, these embodiments and examples do not limit the technical scope of the present disclosure. These embodiments and examples are illustrative in all respects. These embodiments and examples are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from these embodiments and combined in any way.

[0015] Geometric terms (e.g., parallel, perpendicular, orthogonal) should not be interpreted strictly. For example, "parallel" may deviate slightly from its strict meaning. Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensions. Dimensional relationships in each figure may be altered to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0016] A numerical range such as "from m to n%" includes the upper limit value and the lower limit value, unless otherwise specified. "From m to n%" indicates 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 Drawings

[0017] [Figure 1] It is a schematic plan view showing an example of a bipolar current collector in this embodiment. [Figure 2] It is a sectional view taken along the line A-A of FIG. 1. [Figure 3] It is a schematic flowchart of a method for manufacturing a bipolar current collector in this embodiment. [Figure 4] It is a conceptual diagram showing an example of a manufacturing apparatus in this embodiment. [Figure 5] It is a schematic plan view showing an example of a first metal foil and a second metal foil. [Figure 6] It is a first schematic plan view showing an example of a second metal foil. [Figure 7] It is a second schematic plan view showing an example of a second metal foil. [Figure 8] It is a schematic sectional view showing an example of a bipolar electrode in this embodiment. [Figure 9] It is a schematic sectional view showing an example of a bipolar battery in this embodiment. [Figure 10] It is a table showing evaluation results.

Modes for Carrying Out the Invention

[0018] <Bipolar Current Collector> Figure 1 is a schematic plan view showing an example of a bipolar current collector in this embodiment. Figure 2 is a cross-sectional view of Figure 1, section AA. The bipolar current collector 10 includes a first metal foil 11, an adhesive layer 13, and a second metal foil 12. For convenience, the adhesive layer 13 is not shown in Figure 1. As shown in Figure 2, 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 by the adhesive layer 13. As shown in Figure 1, 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 may be, for example, 1 to 50 mm, 1 to 30 mm, or 1 to 10 mm.

[0019] The ratio of the area of ​​the portion enclosed by the second metal foil 12 (frame) to the total area of ​​the first main surface 11a may 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 ratio of the same area may also 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.

[0020] • First metal foil, second metal foil The first metal foil 11 and the second metal foil 12 are made of dissimilar materials. As long as they are made of dissimilar materials, the first metal foil 11 and the second metal foil 12 may contain any metallic material. For example, the first metal foil 11 and the second metal foil 12 may contain at least one selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), titanium (Ti), iron (Fe), and stainless steel (SUS).

[0021] The first metal foil 11 may contain, for example, Al. That is, the first metal foil 11 may be Al foil. The Al foil in this embodiment includes pure Al foil and Al alloy foil. The Al foil may contain any metallic material represented by alloy numbers from the 1000s to the 8000s as described in "JIS H 4000". The thickness of the first metal foil 11 may be, for example, 1 to 100 μm, 5 to 75 μm, or 10 to 50 μm.

[0022] The second metal foil 12 may contain, for example, Cu. That is, the second metal foil 12 may be Cu foil. The Cu foil in this embodiment includes pure Cu foil and Cu alloy foil. The Cu foil may contain any metallic material represented by alloy numbers from the 1000 to 7000 range as described in "JIS H 3100". The thickness of the second metal foil 12 may be, for example, 1 to 50 μm, 3 to 30 μm, or 5 to 10 μm.

[0023] ·Adhesive layer The adhesive layer 13 is electrically conductive. The adhesive layer 13 may contain, for example, a resin material and a conductive filler. For example, the adhesive layer 13 may contain 1 to 99% by mass fraction of a conductive filler and the remainder being a resin material. The mass fraction of the conductive filler may be, for example, 5 to 50% or 10 to 30%.

[0024] The resin material is an adhesive component. The resin material may have resistance to the electrolyte. The resin material may be insoluble in the electrolyte. The resin material may include, for example, at least one selected from the group consisting of olefin resins, urethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, epoxy resins, and polyester resins. The resin material may include, for example, a one-component adhesive or a two-component adhesive. In a two-component adhesive, the main component may include, for example, an olefin resin. The curing agent may include, for example, a compound having an isocyanate group.

[0025] The conductive filler is a conductive component. The conductive filler may include, for example, carbon particles, metal particles, metal-plated particles, etc. The core of the metal-plated particles may be solid or hollow resin particles. The conductive filler may include, for example, at least one selected from the group consisting of carbon black, graphite, vapor-grown carbon fibers, 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 spherical, flake-shaped, rod-shaped, needle-shaped, fibrous, etc.

[0026] The particle size of the conductive filler may be, for example, 0.1 to 10 μm, 0.5 to 5 μm, or 1 to 3 μm. "Particle size" refers to the average value of the maximum Ferret diameter in the particle image. The average value is calculated from the results of 10 or more measurements. The ratio of the thickness of the adhesive layer 13 to the particle size of the conductive filler may be, for example, 0.5 to 2, or 0.8 to 1.2. The thickness of the adhesive layer 13 may be, for example, 1 to 10 μm, 1 to 5 μm, or 2 to 4 μm. By making the thickness of the adhesive layer 13 2 μm or more, improved resistance to permeation to the electrolyte can be expected.

[0027] • Penetration resistance The through-resistance indicates 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 may be, for example, 150 mΩ or less. The through-resistance may be, for example, 125 mΩ or less, 100 mΩ or less, or 75 mΩ or less. The through-resistance may be, for example, 10 mΩ or more, or 50 mΩ or more.

[0028] <Manufacturing method for bipolar current collectors> Figure 3 is a schematic flowchart of the manufacturing method for a bipolar current collector in this embodiment. Hereinafter, "the manufacturing method for a bipolar current collector in this embodiment" may be abbreviated as "this manufacturing method." This manufacturing method includes "(a) preparation of metal foil," "(b) formation of adhesive layer," and "(c) bonding." Note that the order in Figure 3 is merely an example. For example, multiple steps may proceed simultaneously. For example, multiple steps may proceed in sequence. Figure 4 is a conceptual diagram showing an example of a manufacturing apparatus in this embodiment. The manufacturing apparatus 200 can carry out this manufacturing method. The bipolar current collector 10 may be manufactured, for example, by a roll-to-roll method. The arrows in Figure 4 indicate the direction of workpiece transport.

[0029] (a) Preparation of metal foil Figure 5 is a schematic plan view showing an example of a first metal foil and a second metal foil. This manufacturing method includes preparing a first metal foil 11 and a second metal foil 12. For example, a strip of Al foil may be prepared as the first metal foil 11.

[0030] The second metal foil 12 is prepared to include a portion having a frame-like planar shape. In the second metal foil 12, there may be one or more portions having a frame-like planar shape. For example, the second metal foil 12 may be manufactured by punching. For example, a strip of Cu foil may be prepared. For example, punching may be performed at a constant pitch along the length of the strip of Cu foil. The punched portions 12a may be reused, for example, in the manufacture of Cu foil.

[0031] As long as the punching process is carried out in such a way that a frame-like portion is formed, the planar shape of the punched portion 12a (hole) is arbitrary. The planar shape of the punched portion 12a may be, for example, rectangular. Figure 6 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, elliptical, circular, etc. Figure 7 is a second schematic plan view showing an example of the second metal foil. For example, metal foil may be left to bridge two opposing sides (frame).

[0032] (b) Formation of the adhesive layer This manufacturing method includes forming an adhesive layer 13 by applying adhesive 3 to one side (first main surface 11a) of the first metal foil 11. For example, adhesive 3 may be prepared by mixing a main agent, a curing agent, and a conductive filler. The application method is arbitrary. For example, as shown in Figure 4, adhesive 3 may be applied to the first metal foil 11 by a gravure roll 201. Adhesive 3 may be dried, for example, by a drying oven 202.

[0033] (c) bonding This manufacturing method includes manufacturing a bipolar current collector 10 by attaching a second metal foil 12 to an adhesive layer 13. For example, bonding may be performed by dry lamination. For example, the second metal foil 12 may be bonded to the first metal foil 11 by a hot roll 203. The second metal foil 12 is bonded along the periphery of the first metal foil 11 (first main surface 11a).

[0034] The bipolar current collector 10 may be cut to match the electrode shape. The cutting may be done before the formation of the positive electrode layer 21 and the negative electrode layer 22, or after the formation of the positive electrode layer 21 and the negative electrode layer 22. The dashed lines in Figures 5 to 7 show an example of a cutting line.

[0035] <Bipolar electrodes> Figure 8 is a schematic cross-sectional view showing an example of a bipolar electrode in this 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 located on the second main surface 11b. "On the second main surface 11b" can be rephrased as the surface of the second main surface 11b. The same applies to "on the adhesive layer 13" described later.

[0036] 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, for example, polyvinylidene fluoride, etc. The thickness of the positive electrode layer 21 may be, for example, 10 to 500 μm, 50 to 300 μm, or 100 to 200 μm.

[0037] The negative electrode layer 22 is disposed 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 to cover a portion of the second metal foil 12. The negative electrode layer 22 contains 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, carboxymethylcellulose, etc. The thickness of the negative electrode layer 22 may be, for example, 10 to 500 μm, 50 to 300 μm, or 100 to 200 μm.

[0038] <Bipolar battery> Figure 9 is a schematic cross-sectional view showing an example of a bipolar battery in this embodiment. The bipolar battery 100 includes a bipolar electrode 20, an electrolyte (not shown), and a sealing material 40. The bipolar battery 100 may also include, for example, an outer casing (not shown). The outer casing may house the bipolar electrode 20 and the electrolyte. The outer casing may be, for example, a pouch made of metal foil laminate film, a metal case, etc.

[0039] The electrolyte is a liquid electrolyte. The electrolyte may contain, for example, a supporting salt and a solvent. The supporting salt may contain, for example, LiPF6. The solvent may contain, for example, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc. The electrolyte may further contain any additives.

[0040] Multiple 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 placed 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.

[0041] The sealing material 40 seals between the second main surface 11b and the second metal foil 12 (frame) between two adjacent bipolar electrodes 20. In the XY plane, the sealing material 40 surrounds the positive electrode layer 21 and the negative electrode layer 22. The sealing material 40 may include, for example, a first sealing material 41 (primary sealing) and a second sealing material 42 (secondary sealing). The first sealing material 41 may seal between the second main surface 11b and the second metal foil 12. The second sealing material 42 may further seal the outside of the first sealing material 41. The sealing material 40 includes, for example, a resin material. The sealing material may include, for example, at least one selected from the group consisting of polypropylene, polyphenylene sulfide, and modified polyphenylene ether. The second sealing material 42 may be the same material as the first sealing material 41 or a different material. [Examples]

[0042] <Sample preparation> No.1 The following materials were prepared.

[0043] First metal foil 11: Al foil Second metal foil 12: Cu foil (die-cut, die-cut portion 12a: rectangular) Main component: Olefin resin Hardening agent: Isocyanate compound Conductive filler: Ni-plated particles

[0044] Adhesive 3 was prepared by mixing the main agent, hardener, and conductive filler. The first metal foil 11, the second metal foil 12, and adhesive 3 were set in the manufacturing apparatus 200 (see Figure 4). A bipolar current collector 10 was manufactured under the following conditions.

[0045] Line speed (workpiece transport speed): 15 m / min Gravure Roll 201: Elongated, 75 lines Drying oven 202 setting temperature: 150℃ Surface temperature of heat roll 203: 90℃ Nip pressure of heat roll 203: 0.45 MPa

[0046] No. 2 The bipolar current collector 10 was manufactured in the same manner as No. 1, except that Cu foil (unprocessed, without holes) was used as the second metal foil 12.

[0047] <Rating> Figure 10 is a table showing the evaluation results. In Figure 10, "Guideline" and "Target" are values ​​for the samples used in this experiment. No. 1 (frame-shaped Cu foil) showed the same penetration resistance as No. 2 (normal Cu foil). No. 1 also had sufficient quality (minimum thickness, average thickness) of the adhesive layer 13. Therefore, sufficient permeability resistance to the electrolyte can be expected. In No. 1, the coating properties of the negative electrode composite were also evaluated by applying the composite material onto the adhesive layer 13. The coating properties of No. 1 were equivalent to those of No. 2. [Explanation of Symbols]

[0048] 3 Adhesive, 10 Bipolar current collector, 11 First metal foil, 11a First main surface, 11b Second main surface, 12 Second metal foil, 12a Part, 13 Adhesive layer, 20 Bipolar electrode, 21 Positive electrode layer, 22 Negative electrode layer, 30 Separator, 40 Sealing material, 41 First sealing material, 42 Second sealing material, 100 Bipolar battery, 200 Manufacturing equipment, 201 Gravure roll, 202 Drying oven, 203 Heat roll.

Claims

1. First metal foil, Adhesive layer, and, Second metal foil, Includes, 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 by 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. Bipolar current collector.

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

3. Bipolar current collector according to claim 1 or claim 2, The positive electrode layer, and, Negative electrode layer, Includes, The positive electrode layer is arranged on the second main surface, and The negative electrode layer is disposed on the adhesive layer, Bipolar electrodes.

4. Multiple bipolar electrodes, Electrolyte, and Sealant, Includes, Each of the plurality of bipolar electrodes is the bipolar electrode described in claim 3, Multiple bipolar electrodes are stacked in the thickness direction, and The sealing material seals the space between the second main surface and the second metal foil between two adjacent bipolar electrodes. Bipolar battery.

5. (a) Prepare the first metal foil and the second metal foil. (b) Applying an adhesive to one side of the first metal foil to form an adhesive layer, and (c) A bipolar current collector is manufactured by attaching the second metal foil to the adhesive layer. Includes, The adhesive layer has electronic 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. A method for manufacturing a bipolar current collector.

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