Current collector foil, bipolar storage battery, and material recovery method for bipolar storage battery

Abstract

To easily separate a positive electrode foil and a negative electrode foil when recovering a material.SOLUTION: A material recovery method for a bipolar storage battery includes a disassembly step of disassembling the bipolar storage battery and separating a bipolar electrode from a constituent member, a foaming step of heating the separated bipolar electrode and foaming a resin foaming agent contained in an adhesive layer of a current collector foil forming the bipolar electrode to increase a thickness of the adhesive layer, and a separation step of separating a positive electrode foil and a negative electrode foil adhered via the adhesive layer in the current collector foil in a state where the thickness of the adhesive layer is increased by foaming the resin foaming agent.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a current collecting foil, a bipolar storage battery, and a method for recovering materials from a bipolar storage battery. [Background technology]

[0002] Patent Document 1 discloses a method for recovering materials from a bipolar storage battery, in which a battery pack is disassembled, an external force is applied to the bipolar electrodes obtained using a tool, the substrate and adhesive are mechanically removed, and the positive electrode current collector and the negative electrode current collector are separated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-147473 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration described in Patent Document 1, the substrate and adhesive are mechanically removed using a tool, making complete removal difficult and requiring a post-processing step to remove the residue, leaving room for improvement.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a current collector foil, a bipolar storage battery, and a material recovery method for a bipolar storage battery that allows the positive electrode foil and the negative electrode foil to be easily separated when recovering materials. [Means for solving the problem]

[0006] The current collector foil according to the present invention is a current collector foil in which a positive electrode foil and a negative electrode foil are bonded via an adhesive layer containing a conductive material, and the adhesive layer is characterized in that it contains a resin foaming agent.

[0007] According to this configuration, since the adhesive layer of the laminated foil contains a resin foaming agent, the resin foaming agent can be foamed when recovering the constituent materials of the current collector foil, making it easier to separate the positive electrode foil and the negative electrode foil.

[0008] The resin foaming agent may include at least one of a plurality of types of chemical foaming agents.

[0009] According to this configuration, the resin foaming agent of the adhesive layer can be a chemical foaming agent.

[0010] The resin foaming agent may include at least one of a chemical foaming agent and a thermally expandable microcapsule.

[0011] According to this configuration, the resin foaming agent in the adhesive layer phase can be made of thermally expandable microcapsules.

[0012] The resin foaming agent may be contained in the adhesive layer at a ratio of 10 to 50%.

[0013] According to this configuration, the resin foaming agent in the pre-foamed state is mixed in a proportion that does not impede electronic conductivity between the positive electrode foil and the negative electrode foil.

[0014] The adhesive layer may contain an olefin resin, an epoxy resin, and a metal-plated resin, and the olefin resin may be a resin having a melting point lower than the foaming initiation temperature of the resin foaming agent.

[0015] According to this configuration, the olefin resin contained in the adhesive layer is a thermoplastic resin, and therefore softens when the resin foaming agent foams, forming a film that allows the resin foaming agent to expand.

[0016] A bipolar storage battery according to the present invention is a bipolar storage battery including a current collector foil in which a positive electrode foil and a negative electrode foil are bonded via an adhesive layer containing a conductive material, wherein the adhesive layer contains a resin foaming agent.

[0017] According to this configuration, since the adhesive layer of the laminated foil provided in the bipolar storage battery contains a resin foaming agent, the resin foaming agent can be foamed when recovering the constituent materials of the bipolar storage battery, thereby facilitating separation of the positive electrode foil and the negative electrode foil.

[0018] The positive electrode foil may be an aluminum foil, and the negative electrode foil may be a copper foil.

[0019] With this configuration, the aluminum foil and the copper foil can be easily separated from each other after the resin foaming agent in the adhesive layer has foamed.

[0020] The method for recovering materials from a bipolar storage battery according to the present invention includes a disassembly step of disassembling the bipolar storage battery and separating the bipolar electrodes from constituent members; a foaming step of heating the separated bipolar electrodes to foam a resin foaming agent contained in an adhesive layer of a current collector foil that forms the bipolar electrode, thereby increasing the thickness of the adhesive layer; and a separation step of separating a positive electrode foil and a negative electrode foil that are bonded to the current collector foil via the adhesive layer in a state in which the resin foaming agent has foamed and the thickness of the adhesive layer has increased.

[0021] According to this configuration, the positive electrode foil and the negative electrode foil can be easily separated by foaming the resin foaming agent contained in the adhesive layer of the current collector foil.

[0022] The adhesive layer may contain an olefin-based resin, an epoxy-based resin, and a metal-plated resin, the olefin-based resin having a melting point lower than the foaming initiation temperature of the resin foaming agent, and the foaming process may include a process of heating the bipolar electrode to a temperature higher than the foaming initiation temperature of the resin foaming agent.

[0023] According to this configuration, since the olefin resin contained in the adhesive layer is a thermoplastic resin, the olefin resin softens during the foaming step to form a film, which allows the resin foaming agent to expand. [Effects of the Invention]

[0024] In the present invention, the positive electrode foil and the negative electrode foil can be easily separated when the material is recovered. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram schematically illustrating a current collecting foil according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a state before the resin foaming agent contained in the adhesive layer foams, and a state in which the adhesive layer has become thicker after the resin foaming agent foams. [Figure 3] FIG. 3 is a flowchart showing a method for recovering materials from a bipolar storage battery. [Figure 4] FIG. 4 is a diagram for explaining the steps after the resin foaming agent of the adhesive layer has foamed. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, a current collecting foil, a bipolar storage battery, and a method for recovering materials from a bipolar storage battery according to embodiments of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0027] 1 is a diagram schematically illustrating a current collector foil according to an embodiment. The current collector foil 1 includes an aluminum foil 2, a copper foil 3, an adhesive layer 4, and carbon coating layers 5 and 6.

[0028] The current collector foil 1 is a laminated foil in which an aluminum foil 2, which is a positive electrode foil, and a copper foil 3, which is a negative electrode foil, are bonded via an adhesive layer 4. One surface of each of the aluminum foil 2 and the copper foil 3 is covered with carbon coating layers 5 and 6. The laminated foil, current collector foil 1, constitutes a bipolar electrode. A bipolar electrode including the current collector foil 1 is a component that constitutes a bipolar storage battery. A bipolar storage battery has multiple bipolar electrodes, each including the current collector foil 1. A bipolar storage battery including the current collector foil 1 is a bipolar lithium-ion battery. A bipolar lithium-ion battery including the current collector foil 1 is installed in an electric vehicle. The electric vehicle is an electric vehicle (BEV) or a plug-in hybrid vehicle (PHEV).

[0029] The aluminum foil 2 is a positive electrode substrate. A positive electrode composite material is provided on one surface of the aluminum foil 2 via a carbon coating layer 5.

[0030] The copper foil 3 is a negative electrode substrate. A negative electrode composite material is provided on one surface of the copper foil 3 via a carbon coating layer 6.

[0031] The adhesive layer 4 is a resin layer that bonds the aluminum foil 2 and the copper foil 3. The adhesive layer 4 contains an olefin resin, an epoxy resin, a metal-plated resin that ensures electrical conductivity, and a resin foaming agent. Of the olefin resin, epoxy resin, metal-plated resin, and resin foaming agent that make up the adhesive layer 4, the olefin resin is selected to have a melting point lower than the foaming initiation temperature of the resin foaming agent. This increases the fluidity of the adhesive layer 4 and promotes foaming.

[0032] The resin foaming agent for the adhesive layer 4 is one or a mixture of several types of chemical foaming agents, and one that can foam in a target temperature range is selected.

[0033] Chemical foaming agents include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), p,p'-oxybisbenzenesulfonylhydrazide (OBSH), and sodium bicarbonate (baking soda).

[0034] Furthermore, the resin foaming agent of the adhesive layer 4 may use thermally expandable microcapsules instead of a chemical foaming agent, or may contain both a chemical foaming agent and thermally expandable microcapsules. The resin foaming agent may be composed of only a chemical foaming agent, only thermally expandable microcapsules, or may contain both a chemical foaming agent and thermally expandable microcapsules. When the resin foaming agent is composed of a chemical foaming agent, the resin foaming agent of the adhesive layer 4 contains at least one of several types of chemical foaming agents (ADCA, DPT, OBSH, and baking soda).

[0035] Furthermore, the resin foaming agent in the adhesive layer 4 is contained in a proportion of 10 to 50% in the adhesive layer 4. In the adhesive layer 4, the resin foaming agent in a state before foaming is mixed in a proportion that does not interfere with electronic conductivity between the aluminum foil 2 and the copper foil 3. The proportion that does not interfere with electronic conductivity between the aluminum foil 2 and the copper foil 3 means that the proportion of the resin foaming agent mixed in the adhesive layer 4 is 10 to 50%.

[0036] The resin foaming agent has two functions: to increase the thickness of the adhesive layer 4 when foaming, and to decrease the density of the adhesive layer 4 when foaming. By utilizing this function, when recovering the material, physical peeling using a scraper or the like is performed, or peeling is performed by carbonizing and gasifying the resin portion through roasting and combustion.

[0037] As shown in Figure 2, when the current collector foil 1 is in an unconstrained environment, the adhesive layer 4 is thin before the resin foaming agent foams, and the adhesive layer 4 is thick after the resin foaming agent foams. During recycling, the current collector foil 1 is heated at a relatively low temperature, causing the resin foaming agent in the adhesive layer 4 to foam, forming gaps between the aluminum foil 2 and the copper foil 3. As a result, when the current collector foil 1 is heated to a predetermined temperature or higher under unconstrained conditions during recycling, the resin foaming agent in the adhesive layer 4 foams, allowing the aluminum foil 2 and copper foil 3 to be easily separated from the laminated foil. In other words, when the resin foaming agent in the adhesive layer 4 foams and many gaps are formed between the aluminum foil 2 and the copper foil 3, mechanical peeling and gas diffusion during roasting become easier.

[0038] In a bipolar storage battery including current collector foil 1 configured in this manner, when the battery pack is constrained (when high pressure is applied between the electrodes), even if the resin foaming agent in adhesive layer 4 foams, the volume of adhesive layer 4 cannot be increased, and a sufficient peeling effect cannot be obtained. Therefore, in order to maximize the foaming effect of the resin foaming agent, it is desirable to disassemble the battery module and, once the bipolar electrodes are disassembled, heat current collector foil 1 to foam the resin foaming agent in adhesive layer 4.

[0039] Furthermore, because the olefin resin contained in the adhesive layer 4 is a thermoplastic resin, it softens when the resin foaming agent foams, forming a film that allows the resin foaming agent to expand. As a result, the foaming of the resin foaming agent creates a sufficient gap between the aluminum foil 2 and the copper foil 3, making it possible to complete the process in a shorter time and at lower cost than conventional methods, whether by mechanical peeling using a scraper or by high-temperature roasting (600°C or less).

[0040] 3 is a flowchart showing a method for recovering materials from a bipolar storage battery. The method for recovering materials from a bipolar storage battery includes a detoxification step (step S1), a battery pack disassembly step (step S2), a battery module disassembly step (step S3), an electrolyte recovery step (step S4), a composite material recovery step (step S5), and a laminated foil peeling step (step S6).

[0041] The detoxification process is a process of discharging the battery pack to make it safe to handle (step S1). The detoxification process includes a discharging process. The battery pack is a bipolar lithium-ion battery equipped with bipolar electrodes including a current collecting foil 1.

[0042] The battery pack disassembly step is a step of disassembling the battery pack and separating the battery modules from the constituent members of the battery pack (step S2). The battery pack includes a plurality of battery modules, and each battery module includes a bipolar electrode.

[0043] The battery module disassembly process involves disassembling the battery module and removing the resin from the four sides of the battery module so that the battery module can be separated into individual bipolar electrodes (step S3). In this disassembly process, resin from the four sides of the battery module, such as sealing material, is removed from the battery module, which is formed in a rectangular shape.

[0044] The electrolytic solution recovery step is a step of recovering the electrolytic solution filling between the bipolar electrodes by heating, drying under reduced pressure, or the like before the heat treatment of the bipolar electrodes (step S4).

[0045] The composite material recovery step is a step of removing and recovering the positive electrode composite material and the negative electrode composite material applied to the bipolar electrodes from the current collector foil 1 (step S5). The positive electrode composite material is applied to the surface of the carbon coating layer 5 on the positive electrode side. The negative electrode composite material is applied to the surface of the carbon coating layer 6 on the negative electrode side.

[0046] The peeling step of the laminated foil is a step of heat-treating the current collector foil 1 to increase the film thickness of the adhesive layer 4 and reduce the density of the adhesive layer 4, thereby separating the aluminum foil 2 and the copper foil 3 (step S6). This peeling step includes a foaming step and a separation step. The foaming step is a step of heating the bipolar electrode to foam the resin foaming agent contained in the adhesive layer 4 of the current collector foil 1 that forms the bipolar electrode, thereby increasing the thickness of the adhesive layer 4. The separation step is a step of separating the aluminum foil 2 and the copper foil 3 that are bonded together via the adhesive layer 4 in the current collector foil 1, in a state in which the resin foaming agent has foamed and the thickness of the adhesive layer 4 has increased.

[0047] The foaming step includes a step (heat treatment) of heating the current collector foil 1 so that the temperature is higher than the foaming initiation temperature of the resin foaming agent in the adhesive layer 4. The heat treatment of the current collector foil 1 may be any of atmospheric heat treatment, contact heating, and induction heating.

[0048] In the separation step, the laminated foil is separated into aluminum foil 2 and copper foil 3. Methods for separating the electrode foil include physically peeling it off with a tool and separating the aluminum foil 2 and copper foil 3 by roasting. As shown in FIG. 4, in the separation step, the current collector foil 1 in which the adhesive layer 4 has been foamed is roasted at 600°C or less in a furnace 200, and after this heat treatment, the aluminum foil 2 and copper foil 3 are separated by hand. Roasting is performed in the furnace 200 at 350 to 600°C, and the roasting time is within a few minutes.

[0049] In this way, the positive electrode mixture, the negative electrode mixture, the aluminum foil 2, and the copper foil 3 are recovered, thereby completing the recovery of both electrode mixtures and the substrate of the bipolar electrode.

[0050] As described above, according to the embodiment, the resin foaming agent in the adhesive layer 4 foams, creating a sufficient gap between the aluminum foil 2 and the copper foil 3, making it possible to recover the aluminum foil 2 and the copper foil 3 in a shorter time and at a lower cost than conventional methods, even by mechanical peeling using a scraper or high-temperature roasting.

[0051] In the method for recovering materials from a bipolar storage battery, the composite recovery step (step S5) and the laminated foil peeling step (step S6) may be performed in any order. A recovery method is possible in which the peeling step is performed after the electrolyte recovery step, and then the composite recovery step is performed.

[0052] Furthermore, in the current collector foil 1, the combination of metal foils constituting the positive and negative electrode foils is not limited to aluminum foil 2 and copper foil 3. The metal foil included in the current collector foil 1 may also be lead foil. In other words, the bipolar storage battery including the current collector foil 1 is not limited to a bipolar lithium-ion battery, but may also be a bipolar lead-acid battery or a bipolar nickel-metal hydride battery.

[0053] Furthermore, the carbon coating layers 5 and 6 do not necessarily have to be provided. For example, a positive electrode composite layer is formed by applying a positive electrode slurry to the surface of the aluminum foil 2. Similarly, a negative electrode composite layer is formed by applying a negative electrode slurry to the surface of the copper foil 3. [Explanation of symbols]

[0054] 1 Current collecting foil 2. Aluminum foil (positive electrode foil) 3 Copper foil (negative electrode foil) 4 Adhesive layer 5,6 Carbon coating layer

Claims

1. A current collector foil in which a positive electrode foil and a negative electrode foil are bonded via an adhesive layer containing a conductive material, The adhesive layer contains a resin foaming agent. A current collecting foil characterized by:

2. The resin foaming agent contains at least one of a plurality of types of chemical foaming agents. The current collector foil according to claim 1 .

3. The resin foaming agent includes at least one of a chemical foaming agent and a thermally expandable microcapsule. The current collector foil according to claim 1 .

4. The resin foaming agent is contained in the adhesive layer at a ratio of 10 to 50%. The current collector foil according to any one of claims 1 to 3.

5. the adhesive layer contains an olefin-based resin, an epoxy-based resin, and a metal-plated resin; The olefin resin has a melting point lower than the foaming initiation temperature of the resin foaming agent. The current collector foil according to claim 4 .

6. A bipolar storage battery including a current collector foil in which a positive electrode foil and a negative electrode foil are bonded via an adhesive layer containing a conductive material, The adhesive layer contains a resin foaming agent. A bipolar storage battery characterized by:

7. The resin foaming agent contains at least one of a plurality of types of chemical foaming agents.

7. The bipolar storage battery according to claim 6,

8. The resin foaming agent includes at least one of a chemical foaming agent and a thermally expandable microcapsule.

7. The bipolar storage battery according to claim 6,

9. The resin foaming agent is contained in the adhesive layer at a ratio of 10 to 50%.

9. The bipolar storage battery according to claim 6, wherein the bipolar storage battery is a bipolar storage battery.

10. the adhesive layer contains an olefin-based resin, an epoxy-based resin, and a metal-plated resin; The olefin resin has a melting point lower than the foaming initiation temperature of the resin foaming agent.

10. The bipolar storage battery according to claim 9.

11. The positive electrode foil is an aluminum foil, The negative electrode foil is a copper foil.

11. The bipolar storage battery according to claim 10.

12. A method for recovering materials from a bipolar storage battery, comprising: a disassembly step of disassembling the bipolar storage battery to separate the bipolar electrodes from the components; a foaming step of heating the separated bipolar electrode to foam a resin foaming agent contained in an adhesive layer of a current collecting foil forming the bipolar electrode, thereby increasing the thickness of the adhesive layer; a separation step of separating the positive electrode foil and the negative electrode foil bonded to the current collector foil via the adhesive layer in a state in which the resin foaming agent has foamed and the thickness of the adhesive layer has increased; A method for recovering materials from a bipolar storage battery, comprising:

13. the adhesive layer contains an olefin-based resin, an epoxy-based resin, and a metal-plated resin; the olefin-based resin has a melting point lower than the foaming initiation temperature of the resin foaming agent, The foaming step includes a step of heating the bipolar electrode to a temperature higher than the foaming initiation temperature of the resin foaming agent.

13. The method for recovering materials from a bipolar storage battery according to claim 12.

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