Method for manufacturing bipolar electrode, and bipolar electrode

Abstract

The invention relates to a method for manufacturing a bipolar electrode and a bipolar electrode. A method for manufacturing a bipolar electrode includes the following (a)-(f). (a) A first carbon coating film is formed on a sheet-like support material. (b) A conductive resin layer is formed on the first carbon film. And (c) forming a second carbon film on the conductive resin layer. And (d) forming a second electrode layer on the second carbon film. And (e) separating the support material from the first carbon film. And (f) forming a first electrode layer on the first carbon film to produce a bipolar electrode.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a bipolar electrode and the bipolar electrode. Background Art

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

[0003] Conventionally, the current collector of the bipolar electrode is manufactured by laminating two kinds of metal foils. For example, from the viewpoint of effective utilization of resources, it is desired to reduce the amount of metal used.

[0004] An object of the present invention is to reduce the amount of metal used.

[0005] 1. A method for manufacturing a bipolar electrode includes the following (a) to (f).

[0006] (a) A first carbon film is formed on a sheet-like support material.

[0007] (b) A conductive resin layer is formed on the first carbon film.

[0008] (c) Forming a second carbon film on the conductive resin layer.

[0009] (d) Forming a second electrode layer on the second carbon film.

[0010] (e) Separating the support material from the first carbon film.

[0011] (f) A first electrode layer is formed on the first carbon film, thereby manufacturing a bipolar electrode.

[0012] The above (d), (e) and (f) are performed sequentially.

[0013] By using a conductive resin layer instead of a metal foil as a current collector, the amount of metal used is greatly reduced. However, it is usually difficult for a conductive resin layer to become a self-supporting layer, so it is difficult to form an electrode layer on the conductive resin layer. Therefore, a support material is used. A conductive resin layer is formed on the support material. By forming an electrode layer on one side of the conductive resin layer, the conductive resin layer and the electrode layer can form a self-supporting layer as a whole. After forming the self-supporting layer, the support material is separated. After separating the support material, another electrode layer is formed on the back of the conductive resin layer. The conductive resin layer can show sufficient electronic conductivity in the thickness direction. However, the conductive resin layer has a tendency to have insufficient electronic conductivity in the surface direction. Therefore, by forming a carbon film on both sides of the conductive resin layer, it is expected to improve the electronic conductivity in the surface direction.

[0014] 2. The method for producing a bipolar electrode according to the above-mentioned “1” may include, for example, the following configuration: The support material includes a fluororesin.

[0015] Fluororesins tend to have excellent releasability (non-stickiness). When the support material contains fluororesins, it is expected that the support material can be easily separated.

[0016] 3. The method for manufacturing a bipolar electrode described in “1” or “2” above may include, for example, the following configurations: The first electrode layer is a positive electrode layer. The second electrode layer is a negative electrode layer.

[0017] The negative electrode layer generally has a larger area than the positive electrode layer. By forming the negative electrode layer first, for example, it is expected that handling properties will be improved when forming the positive electrode layer.

[0018] 4. The bipolar electrode includes a positive electrode layer, a first carbon coating, a conductive resin layer, a second carbon coating, and a negative electrode layer in this order in the thickness direction.

[0019] 5. The bipolar electrode described in the above “4” may include the following configurations, for example: The conductive resin layer has a larger area than the first electrode layer, the first carbon film, the second carbon film, and the second electrode layer, respectively. The conductive resin layer extends to cover the side surface of the first carbon film.

[0020] By making the conductive resin layer have the largest area, the conductive resin layer can be in direct contact with the sealing material in the bipolar battery. For example, compared with the case where the carbon film is sandwiched between the conductive resin layer and the sealing material, by making the conductive resin layer in direct contact with the sealing material, it is expected that the sealing performance can be improved.

[0021] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") and an example of the present invention (hereinafter referred to as "the present example") are described. However, the present embodiment and the present example do not limit the technical scope of the present invention. The present embodiment and the present example are illustrative in all respects. The present embodiment and the present example are non-restrictive. The technical scope of the present invention includes all changes within the meaning and scope equivalent to those described in the claims. For example, it is also originally intended to extract arbitrary structures from the present embodiment and combine them arbitrarily.

[0022] Geometric terms (such as parallel, perpendicular, orthogonal, etc.) should not be understood in a strict sense. For example, "parallel" may slightly deviate from "parallel" in a strict sense. Geometric terms may include tolerances, errors, etc. in design, operation, and manufacturing. The dimensional relationships in the drawings are sometimes inconsistent with the actual dimensional relationships. In order to facilitate the reader's understanding, the dimensional relationships in the drawings may sometimes be changed. For example, the length, width, thickness, etc. may sometimes be changed. Sometimes a part of the structure is omitted.

[0023] Unless otherwise specified, a numerical range such as “m to n%” includes an upper limit and a lower limit. “m to n%” means a numerical range of “m% or more and n% or less”. “m% or more and n% or less” includes “greater than m% and less than n%”. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, wherein like symbols denote like elements.

[0025] Figure 1 This is a schematic flowchart of the method for manufacturing the bipolar electrode according to the present embodiment.

[0026] Figure 2 This is a first schematic cross-sectional view showing a manufacturing process of a bipolar electrode.

[0027] Figure 3 This is a second schematic cross-sectional view showing the manufacturing process of the bipolar electrode.

[0028] Figure 4 This is a third schematic cross-sectional view showing the manufacturing process of the bipolar electrode.

[0029] Figure 5 This is a fourth schematic cross-sectional view showing the manufacturing process of the bipolar electrode.

[0030] Figure 6 This is a fifth schematic cross-sectional view showing the manufacturing process of the bipolar electrode.

[0031] Figure 7 This is a sixth schematic cross-sectional view showing the manufacturing process of the bipolar electrode.

[0032] Figure 8 This is a first schematic cross-sectional view showing an example of a bipolar electrode according to the present embodiment.

[0033] Fig. 9 This is a second schematic cross-sectional view showing an example of the bipolar electrode according to the present embodiment.

[0034] Fig.10 This is a schematic cross-sectional view showing an example of a bipolar electrode according to the present embodiment.

[0035] Fig.11 is a table showing the evaluation results. DETAILED DESCRIPTION

[0036] Method for manufacturing bipolar electrode

[0037] Figure 1This is a schematic flow chart of the method for manufacturing a bipolar electrode according to the present embodiment. Hereinafter, the "method for manufacturing a bipolar electrode according to the present embodiment" may be referred to as the "present manufacturing method". The present manufacturing method includes "(a) formation of a first carbon film", "(b) formation of a conductive resin layer", "(c) formation of a second carbon film", "(d) formation of a second electrode layer", "(e) separation of a supporting material" and "(f) formation of a first electrode layer". (d) to (f) are performed sequentially. Each step may be implemented, for example, by a roll-to-roll method. Unless otherwise specified, the order of the steps is arbitrary. For example, (a), (b) and (c) may be performed simultaneously.

[0038] In the present manufacturing method, the terms "first" and "second" are used simply to distinguish two elements. The terms "first" and "second" do not include concepts such as order. For example, "on the support material" means "on the surface of the support material." The term "on" has no relation to up and down in the vertical direction.

[0039] (a) Formation of the First Carbon Film

[0040] Figure 2 1 is a first schematic cross-sectional view showing a process of manufacturing a bipolar electrode. This manufacturing method includes forming a first carbon film 11 on a sheet-like support material 5 .

[0041] The support material 5 has an arbitrary thickness. The thickness of the support material 5 may be, for example, 0.1 to 2 mm. The support material 5 may have mold release properties. The support material may include, for example, fluororesins, etc. The support material 5 may include, for example, at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE) and chlorotrifluoroethylene-ethylene copolymer (ECTFE).

[0042] The support material 5 may be releasable in its entirety or in part. For example, the surface of any substrate may be coated with a component having releasability to impart releasability to the surface of the substrate. The component having releasability may include silicone, for example.

[0043] The first carbon film 11 can be formed by coating the surface of the support material 5 with, for example, a first dispersion. The first dispersion can contain, for example, a first carbon material, a binder, and a dispersion medium. Any coating method can be used. For example, a gravure coater, a die coater, etc. can be used. The coating can be formed continuously or intermittently. Figure 2In the example, the coating film is intermittently formed. For example, the coating film can be dried in a drying furnace. The same applies to the subsequent formation methods (coating method, drying method) of the second carbon film 12 and various layers.

[0044] The thickness of the first carbon film 11 can be, for example, 0.1 to 3 μm. For example, the first carbon film 11 can include a first carbon material having a mass fraction of more than 50% and a binder as the remainder. The mass fraction of the first carbon material can be, for example, 75 to 99% or 80 to 95%. The first carbon material has electronic conductivity. The first carbon material can, for example, include at least one selected from the group consisting of acetylene black (AB), graphite, vapor grown carbon fiber (VGCF), graphene flakes (GF), carbon nanotubes (CNT), carbon nanofibers (CNF) and carbon nanospheres (CNS). The binder can, for example, include at least one selected from the group consisting of PVDF, PTFE, carboxymethyl cellulose (CMC) and polyacrylic acid (PAA).

[0045] (b) Formation of Conductive Resin Layer

[0046] Figure 3 : is a second schematic cross-sectional view showing the manufacturing process of the bipolar electrode. The manufacturing method includes forming a conductive resin layer 10 on a first carbon film 11. For example, the conductive resin layer 10 can be formed by coating a conductive adhesive on the surface of the first carbon film 11. The conductive resin layer 10 can be coated continuously, for example. The conductive adhesive can be a single-liquid type or a two-liquid type. The conductive adhesive can include, for example, a main agent, a curing agent, and a conductive filler. The main agent can include, for example, an olefin resin, etc. The curing agent can include, for example, a compound having an isocyanate group, etc.

[0047] The thickness of the conductive resin layer 10 may be, for example, 1 to 100 μm, 1 to 50 μm, 1 to 30 μm, 1 to 10 μm, or 1 to 5 μm. The conductive resin layer 10 has electronic conductivity. The conductive resin layer 10 may include, for example, a resin material and a conductive filler. For example, the conductive resin layer 10 may include a conductive filler of 1 to 99% by mass and a resin material as the remainder. The mass fraction of the conductive filler may be, for example, 5 to 50% or 10 to 30%.

[0048] In the conductive resin layer 10, the resin material forms a continuous phase. The resin material may have resistance to the electrolyte. The resin material may also be insoluble in the electrolyte. The resin material may, for example, include 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, for example, have a hydroxyl group. By making the resin material have a hydroxyl group, a hydrogen bond can be formed between the resin material and the sealing material 40 described later. By forming a hydrogen bond, it can be expected that the sealing performance will be improved.

[0049] In the conductive resin layer 10, the conductive filler forms a dispersed phase. 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 particle may be a solid or hollow resin particle. The conductive filler may include, for example, at least one selected from the group consisting of AB, graphite, VGCF, CNT, CNF, CNS, 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. 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" represents the average value of the maximum Feret diameter in the particle image. The average value is calculated from the results of more than 10 measurements.

[0050] (c) Formation of the Second Carbon Film

[0051] Figure 4 3 is a schematic cross-sectional view showing the manufacturing process of the bipolar electrode. The manufacturing method includes forming a second carbon film 12 on the conductive resin layer 10. The second carbon film 12 can be formed in the same manner as the first carbon film 11. The second carbon film 12 and the first carbon film 11 may have the same composition and size or may be different. The composition and size of the second carbon film 12 can be selected and adjusted within the range described above as the composition and size of the first carbon film 11, for example.

[0052] (d) Formation of the Second Electrode Layer

[0053] Figure 5 4 is a schematic cross-sectional view showing the manufacturing process of the bipolar electrode. The manufacturing method includes forming a second electrode layer 22 on the second carbon film 12. For example, the second electrode layer 22 can be formed by applying a second electrode composite material paste on the surface of the second carbon film 12. The second electrode composite material paste can, for example, contain a second electrode composite material and a dispersion medium. After the second electrode layer 22 is formed (after the second electrode composite material paste is dried), the entire workpiece can be compressed. The compression of the workpiece can be after the first electrode layer 21 described later is formed.

[0054] (e) Separation of support material

[0055] Figure 6 5 is a schematic cross-sectional view showing the manufacturing process of the bipolar electrode. The manufacturing method includes separating the support material 5 from the first carbon film 11. The support material 5 can be peeled off, for example, by an external force. In order to form a starting point for peeling, a clamp such as a scraper can be used, for example. By making the support material 5 have a demolding property, it is expected that the peeling of the support material 5 can be promoted. The recovered support material 5 can be reused.

[0056] (f) Formation of the First Electrode Layer

[0057] Figure 7 6 is a schematic cross-sectional view showing the manufacturing process of the bipolar electrode. The manufacturing method includes manufacturing the bipolar electrode 20 by forming the first electrode layer 21 on the first carbon film 11. For example, the first electrode layer 21 can be formed by applying the first electrode composite material paste on the surface of the first carbon film 11. The first electrode composite material paste can include, for example, the first electrode composite material and a dispersion medium.

[0058] The first electrode layer 21 can be formed in a manner having a smaller area than the second electrode layer 22. The first electrode layer 21 has a different polarity from the second electrode layer 22. For example, the first electrode layer 21 can be a positive electrode layer and the second electrode layer 22 can be a negative electrode layer. For example, the first electrode layer 21 can be a negative electrode layer and the second electrode layer 22 can be a positive electrode layer. The positive electrode layer contains a positive electrode active material. The positive electrode active material can include, for example, lithium nickel composite oxide, lithium iron phosphate, etc. The negative electrode layer contains a negative electrode active material. The negative electrode active material can include, for example, graphite, silicon oxide, silicon, etc. The positive electrode layer and the negative electrode layer can each further include a conductive material and a binder. The positive electrode layer and the negative electrode layer can each independently include AB, PVDF, CMC, SBR, etc.

[0059] After forming the first electrode layer 21, the bipolar electrode 20 may be compressed. After compression, the thickness of the first electrode layer 21 and the second electrode layer 22 may be, for example, 10 to 500 μm, 50 to 300 μm, or 100 to 200 μm, respectively. The bipolar electrode 20 (raw material sheet) may be cut according to the battery specifications. Figure 7 The dashed-dotted line is an example of a cutting line.

[0060] Bipolar Electrode

[0061] Figure 81 is a first schematic cross-sectional view showing an example of a bipolar electrode of the present embodiment. The bipolar electrode 20 has a thickness direction (Z direction). The bipolar electrode 20 includes a first electrode layer 21, a first carbon film 11, a conductive resin layer 10, a second carbon film 12, and a second electrode layer 22 in the thickness direction. The conductive resin layer 10 functions as an electrode collector. The conductive resin layer 10 may have an area larger than the first electrode layer 21, the first carbon film 11, the second carbon film 12, and the second electrode layer 22, respectively. The conductive resin layer 10 may have an area that is, for example, 1.01 to 1.5 times, 1.05 to 1.25 times, or 1.1 to 1.2 times larger than that of each other component (the first electrode layer 21, etc.).

[0062] The conductive resin layer 10 may extend to cover the side of the first carbon film 11. In the XY plane, the conductive resin layer 10 may include a peripheral portion 10a extending to the outside of each film and each layer. The peripheral portion 10a may be on the same horizontal plane as the first carbon film 11. For example, by forming the first carbon film 11 by intermittent coating, it is possible to form Figure 8 The bipolar electrode 20.

[0063] Fig. 9 1 is a second schematic cross-sectional view showing an example of the bipolar electrode of the present embodiment. For example, the first carbon film 11 and the second carbon film 12 may each extend so as to cover the peripheral portion 10a of the conductive resin layer 10. For example, by forming the first carbon film 11 and the second carbon film 12 by continuous coating, a Fig. 9 The bipolar electrode 20.

[0064] In the bipolar electrode 20, the resistance when electrons flow in the thickness direction in the components other than the first electrode layer 21 and the second electrode layer 22 can also be called "penetration resistance". Fig. 9 In the embodiment, the through resistance is the resistance between the first carbon film 11 and the second carbon film 12. The through resistance may be, for example, 150 mΩ or less. The through resistance may be, for example, 100 mΩ or less or 80 mΩ or less. The through resistance may be, for example, 10 mΩ or more or 50 mΩ or more.

[0065] Bipolar battery

[0066] Fig.10 1 is a schematic cross-sectional view showing an example of a bipolar electrode of the present embodiment. The bipolar battery 100 includes two or more bipolar electrodes 20, an electrolyte (not shown) and a sealing material 40. The bipolar battery 100 may include, for example, an outer package (not shown). The outer package may contain the bipolar electrode 20 and the electrolyte. The outer package may be, for example, a metal foil laminated film bag, a metal shell, or the like.

[0067] 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 6 The solvent may include, for example, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc. The electrolyte may further include any additive.

[0068] Two or more 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 first electrode layer 21 and the second electrode layer 22. The separator 30 separates the first electrode layer 21 from the second electrode layer 22. The separator 30 may include, for example, a resin porous film or the like.

[0069] In the peripheral portion 10a of the bipolar electrode 20, the sealing material 40 seals between two adjacent conductive resin layers 10. The conductive resin layer 10 may be in direct contact with the sealing material 40. For example, by using Figure 8 In the bipolar electrode 20, the conductive resin layer 10 can be in direct contact with the sealing material 40. By making the conductive resin layer 10 and the sealing material 40 in direct contact, for example, improvement in sealing performance can be expected.

[0070] In the XY plane, the sealing material 40 surrounds the first electrode layer 21 and the second 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 the adjacent conductive resin layers 10 with each other. The second sealing material 42 may further seal the outer side of the first sealing material 41. The sealing material 40 may include, 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 may be a different material.

[0071] "Primary sealing performance" refers to the peel strength between the first sealing material 41 and the conductive resin layer 10 (or the carbon film). The peel strength can be measured by a 90-degree peel test (ISO29862: 2007). The primary sealing performance of the bipolar battery 100 can be, for example, 0.5 N / mm or more. The primary sealing performance can be, for example, 0.8 N / mm or more or 1.0 N / mm or more.

[0072] “Electrolyte resistance” refers to the primary sealing performance after immersion in the electrolyte for 1000 hours. The electrolyte resistance of the bipolar battery 100 may be, for example, 0.5 N / mm or more. The electrolyte resistance may be, for example, 0.8 N / mm or more or 1.0 N / mm or more.

[0073] Sample preparation

[0074] No.1

[0075] A support material (PTFE sheet) is placed on a roll conveying device. A first dispersion is continuously applied to the surface of the support material and dried to form a first carbon film. A main agent (olefin resin), a curing agent (isocyanate compound), and a conductive filler (Ni-plated particles) are mixed to prepare a conductive adhesive. A conductive adhesive is continuously applied to the surface of the first carbon film and dried to form a conductive resin layer. A second dispersion is continuously applied to the surface of the conductive resin layer and dried to form a second carbon film. The second carbon film has substantially the same composition and size as the first carbon film. A negative electrode composite material paste is continuously applied to the surface of the second carbon film and dried to form a negative electrode layer. After the negative electrode layer is formed, the support material is peeled off from the workpiece and wound. After peeling off the support material, a positive electrode composite material paste is continuously applied to the surface of the first carbon film and dried to form a positive electrode layer. According to the above steps, a bipolar electrode is manufactured. It should be noted that various coatings and coatings are dried using a drying furnace. The drying conditions are as follows.

[0076] Line speed: 15m / min

[0077] Drying oven temperature: 150°C

[0078] No.2

[0079] A conductive adhesive is applied to one side of an aluminum (Al) foil to form an adhesive layer. The conductive adhesive is the same as the conductive adhesive prepared in No. 1. A copper (Cu) foil is attached to the adhesive layer to manufacture an electrode collector. A carbon film is formed on both sides of the electrode collector. After the carbon film is formed, a negative electrode layer is formed on the Cu foil side. A positive electrode layer is then formed on the Al foil side. According to the above steps, a bipolar electrode is manufactured. No. 2 is equivalent to an existing bipolar electrode.

[0080] evaluate

[0081] Fig.11 is a table showing the evaluation results. Fig.11 The "target" in the table is the value for the sample in this experiment. In this experiment, the primary sealing property and electrolyte resistance indicate the sealing property between the carbon film and the sealing material. In each of the penetration resistance, primary sealing property and electrolyte resistance, No.1 shows the same performance as No.2. Therefore, it is considered that No.1 (without metal foil) can withstand practical use.

Claims

1. A method for manufacturing a bipolar electrode, comprising: (a) forming a first carbon film on a sheet-like support material; (b) forming a conductive resin layer on the first carbon film; (c) forming a second carbon film on the conductive resin layer; (d) forming a second electrode layer on the second carbon film; (e) separating the support material from the first carbon film; as well as (f) forming a first electrode layer on the first carbon film to produce a bipolar electrode, The steps (d), (e) and (f) are performed sequentially.

2. The method for manufacturing a bipolar electrode according to claim 1, wherein: The supporting material includes a fluororesin.

3. The method for manufacturing a bipolar electrode according to claim 1 or claim 2, wherein: The first electrode layer is a positive electrode layer, and the second electrode layer is a negative electrode layer.

4. A bipolar electrode comprising, in order in a thickness direction, a first electrode layer, a first carbon coating, a conductive resin layer, a second carbon coating, and a second electrode layer.

5. The bipolar electrode according to claim 4, wherein: The conductive resin layer has an area larger than that of the first electrode layer, the first carbon film, the second carbon film, and the second electrode layer, respectively, and The conductive resin layer extends so as to cover the side surfaces of the first carbon coating.

Images