WO2024074136A1 - 电极极片和电化学装置 - Google Patents

电极极片和电化学装置 Download PDF

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Publication number
WO2024074136A1
WO2024074136A1 PCT/CN2023/123247 CN2023123247W WO2024074136A1 WO 2024074136 A1 WO2024074136 A1 WO 2024074136A1 CN 2023123247 W CN2023123247 W CN 2023123247W WO 2024074136 A1 WO2024074136 A1 WO 2024074136A1
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Prior art keywords
insulating layer
electrode plate
current collector
active layer
electrode sheet
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PCT/CN2023/123247
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English (en)
French (fr)
Inventor
廖林萍
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Xiamen Hithium Energy Storage Technology Co Ltd
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Xiamen Hithium Energy Storage Technology Co Ltd
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Priority to EP23874328.0A priority Critical patent/EP4601060A4/en
Publication of WO2024074136A1 publication Critical patent/WO2024074136A1/zh
Priority to US19/173,754 priority patent/US12573732B2/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/586—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries inside the batteries, e.g. incorrect connections of electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/59—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries characterised by the protection means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage devices, and in particular to an electrode plate and an electrochemical device.
  • Lithium-ion batteries have been widely used in fields such as communication equipment and new energy vehicles due to their high energy density, light weight, and long service life. However, due to the limited cycle life of lithium-ion batteries, a large number of waste lithium-ion batteries are generated every year. These waste lithium-ion batteries contain a large amount of non-renewable and economically valuable metal resources (for example, aluminum foil or copper foil used as current collectors, etc.), so the effective recycling of waste lithium-ion batteries has high economic benefits.
  • metal resources for example, aluminum foil or copper foil used as current collectors, etc.
  • the present application provides an electrode plate and an electrochemical device.
  • the current collector in the electrode plate and the insulating layer can have a lower peeling strength, and the current collector can be fully and efficiently recycled, so that the electrode plate has a higher recovery rate.
  • an electrode plate comprising:
  • An insulating layer coated on at least one surface of the current collector and connected to the periphery of the active layer;
  • the insulating layer includes a water-based adhesive and an inorganic material, and the peel strength of the insulating layer after being immersed in water for 1 minute at a preset temperature is less than or equal to 7N/m.
  • the present application provides an electrochemical device, including: a positive electrode plate, a negative electrode plate, a separator and an electrolyte, and the positive electrode plate and/or the negative electrode plate is an electrode plate of one aspect of the present application.
  • the electrode plate provided in the present application includes: a current collector, an active layer and an insulating layer; the active layer is coated on at least one surface of the current collector; the insulating layer is coated on at least one surface of the current collector and connected to the periphery of the active layer; the insulating layer includes an aqueous binder and an inorganic material.
  • the peel strength of the insulating layer after immersion in water for 1 minute at a preset temperature is less than or equal to 7N/m, indicating that when the electrode plate in the present application is recycled, the insulating layer can be easily peeled off from the current collector through water immersion treatment, the recycling cost is low, green and environmentally friendly, and the recovery rate of the current collector is high, so that the electrode plate has a high recovery rate.
  • FIG1 is a schematic diagram of the structure of a first electrode plate provided by the present application.
  • FIG2 is a schematic diagram of the structure of a second electrode plate provided by the present application.
  • FIG3 is a schematic diagram of the structure of a third electrode plate provided by the present application.
  • FIG4 is a schematic diagram of the structure of a fourth electrode plate provided in the present application.
  • Electrode plate 10 Electrode plate 10; Current collector 1 , active layer 2 , first active layer 21 , second active layer 22 , insulating layer 3 , second surface 31 , first surface 32 .
  • Lithium-ion batteries have been widely used in fields such as communication equipment and new energy vehicles due to their high energy density, light weight, and long service life. However, due to the limited cycle life of lithium-ion batteries, a large number of waste lithium-ion batteries are generated every year. These waste lithium-ion batteries contain a large amount of non-renewable and economically valuable metal resources (for example, aluminum foil or copper foil that can be used as current collectors, etc.), so the effective recycling of waste lithium-ion batteries has high economic benefits.
  • metal resources for example, aluminum foil or copper foil that can be used as current collectors, etc.
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • the present application provides an electrode plate that can solve the above-mentioned problems from the root.
  • Figure 1 is a schematic diagram of the structure of the first electrode sheet provided by the present application, and the schematic diagram of the structure of the electrode sheet is a cross-sectional view
  • Figure 2 is a schematic diagram of the structure of the second electrode sheet provided by the present application, and the schematic diagram of the structure of the electrode sheet is a top view.
  • the electrode sheet 10 may include a current collector 1, an active layer 2, and an insulating layer 3; wherein the active layer 2 may be coated on at least one surface of the current collector 1; the insulating layer 3 may also be coated on at least one surface of the current collector 1 and connected to the periphery of the active layer 2.
  • the active layer 2 and the insulating layer 3 do not overlap and there is no gap. Since the active layer 2 and the insulating layer 3 form a mutually flush structure, the electrode plate 10 can effectively prevent the short circuit problem caused by puncture, thereby improving the safety of the electrochemical device; in addition, the structure of the above-mentioned electrode plate 10 can prevent the electrode plate 10 from being punctured and causing a short circuit, and at the same time, it can also help improve the flatness and stability of the rolling of the electrode plate 10, avoid the risk of overpressure of the electrode plate 10 during cold pressing, and thus ensure the performance of the electrochemical device.
  • the electrode plate provided in the present application has a peel strength of less than or equal to 7N/m after the insulating layer is immersed in water for 1 minute at a preset temperature.
  • the preset temperature is a pre-set temperature, and the specific value can be determined according to the actual ambient temperature or actual needs.
  • the preset temperature can be 0-40°C.
  • the preset temperature can be 0°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc., but is not limited to the listed values.
  • the range of values is The same applies to other values not listed in the range.
  • the insulating layer of the present application can be easily peeled off from the current collector through water immersion treatment, the recycling cost is low and easy, green and environmentally friendly, and the recovery rate of the current collector is high, so that the electrode plates have a high recovery rate.
  • the insulating layer of the present application can also achieve a peel strength of less than or equal to 4N/m after immersion in water at 25°C for 1 minute, which can further show that when the electrode plates of the present application are recycled, the current collector can be simply and efficiently recycled.
  • the electrode plate can be a positive electrode plate or a negative electrode plate.
  • the current collector and the active layer therein are respectively a positive electrode current collector (for example, aluminum foil, etc.) and a positive electrode active layer;
  • the electrode plate is a negative electrode plate, the current collector and the active layer therein are respectively a negative electrode current collector (for example, copper foil, etc.) and a negative electrode active layer.
  • the active layer of the electrode plate usually includes an electrode active material, a binder and a conductive agent; of course, the active layer may also include some optional additives or auxiliary agents, such as a lithium supplement, etc., as required.
  • a slurry consisting of an electrode active material, a conductive agent and a binder is coated on at least one surface of a current collector, which may be a single layer coating or a multilayer coating, which is not limited in this application, and the active layer in this application may be obtained after post-treatment such as drying.
  • the positive electrode active material can be selected from at least one of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, nickel-cobalt-manganese ternary materials, and nickel-cobalt-aluminum ternary materials, etc., and this application does not limit this.
  • the negative electrode plate various negative electrode active materials commonly used in the art can be selected.
  • the negative electrode active material can be selected from at least one of graphite, lithium titanate, and silicon-carbon composite materials, etc., and this application does not limit this.
  • the conductive agent in the active layer can be at least one of a conductive carbon material and a metal material; in some specific embodiments, the conductive carbon material is selected from zero-dimensional conductive carbon, such as acetylene black, conductive carbon black (Super-P); one-dimensional conductive carbon, such as carbon nanotubes; two-dimensional conductive carbon, such as conductive graphite, graphene; three-dimensional conductive carbon, such as reduced graphene oxide; the metal material is selected from at least one of aluminum powder, iron powder and silver powder.
  • the binder in the active layer can be selected from the same water-based binder as the insulating layer. The specific type of the water-based binder can refer to the description below and will not be repeated here.
  • the insulating layer in the electrode plate includes an aqueous binder and an inorganic material.
  • the insulating layer may also include some optional additives or auxiliary agents, such as a dispersant, etc., as required.
  • the aqueous binder may include a hydrophilic group.
  • the hydrophilic group may include but is not limited to at least one of a hydroxyl group, a carboxyl group, a cyano group, etc. It is understood that the present application utilizes the hydrophilicity of the hydrophilic group in the aqueous binder so that the electrode plate can be easily stripped from the current collector by water immersion during recycling, thereby fully and efficiently recycling the current collector.
  • the insulating layer 3 in the electrode plate 10 may include a second surface 31 and a first surface 32 that are opposite to each other, wherein the insulating layer 3 is bonded to at least one surface of the current collector 1 through the first surface 32, and at least part of the hydrophilic groups in the aqueous binder are exposed from the second surface 31.
  • the second surface 31 of the insulating layer 3 away from the current collector 1 is first in contact with water, and the hydrophilic groups exposed in the second surface 31 react with water, so that the aqueous binder contained in the insulating layer 3 is quickly dissolved in water, and then the insulating layer 3 and the current collector 1 can be efficiently peeled off, so that the electrode plate 10 has a higher recovery rate.
  • the active layer 2 may include a first active layer 21 and a second active layer 22 connected to each other, and a portion of the insulating layer 3 covers at least a portion of the second active layer 22.
  • the first active layer 21 and the second active layer 22 may be made of the same material.
  • the first active layer 21 and the second active layer 22 contain the same active material. The specific selection of the active material can refer to the above description and will not be repeated here.
  • the first active layer 21 and the second active layer 22 may also be an integrated structure, which can improve the coating efficiency of the active layer 2 and improve the coating efficiency of the active layer 2. And improve the processing efficiency of the electrode plate 10.
  • the first active layer 21 and the second active layer 22 can be made of different materials, so that the energy density of the second active layer 22 connected to the insulating layer 3 is less than the energy density of the first active layer 21.
  • the second active layer 22 can increase the contact resistance between the current collector and other contacts, thereby reducing the risk of short circuit of the electrode plate 10;
  • the electrode plate provided by the present application can avoid the current collector 1 at the junction of the two from being exposed by the second covering of at least part of the second active layer 22 of the insulating layer 3, and can also ensure the coverage of the current collector 1 by the insulating layer 3, thereby further improving the safety performance of the electrode plate 10.
  • the first active layer 21 and the second active layer 22 may be arranged along the length direction x, and the thickness of the second active layer 22 gradually decreases in the direction away from the first active layer 21. It can be understood that in the rolling process, along the length direction x, the roller acts on the second active layer 22 and the first active layer 21 from one end of the current collector 1 in sequence. Since the thickness of the second active layer 22 gradually decreases in the direction away from the first active layer 21, the roller pressure of the roller on the second active layer 22 increases from small to large, thereby alleviating the roller pressure on the second active layer 22 and reducing the probability of powder falling in the second active layer 22, so as to further improve the safety performance of the electrode sheet 10.
  • the second surface 31 of the insulating layer 3 is larger than the first surface 32 along the length direction x, so that the hydrophilic groups of the second surface 31 increase.
  • the second surface 31 with more hydrophilic groups is first in contact with water, thereby achieving efficient stripping of the insulating layer 3 and the current collector 1, so that the electrode plate 10 has a higher recovery rate.
  • the first active layer 21 and the second active layer 22 may be arranged along the thickness direction y, the second active layer 22 is connected to the current collector 1, and the first active layer 21 is away from the current collector 1.
  • the side of the insulating layer 3 away from the current collector 1 is at least partially covered by the side of the first active layer 21 close to the second active layer 22.
  • the insulating layer can be more closely connected with the first active layer and the second active layer, so that under the external force of puncture or collision with great destructive force, the insulating layer 3 is also difficult to fall off, which can prevent the leakage of the current collector 1, making its electrode plate 10 safer.
  • the mass percentage of the hydrophilic group may be greater than or equal to 50% of the total mass of the aqueous binder. It is understandable that when the mass percentage of the hydrophilic group contained in the aqueous binder is too low, the current collector and the insulating layer in the electrode sheet after water immersion still have a high peel strength, which is not conducive to the peeling of the current collector and the insulating layer, thereby making the recovery efficiency and recovery purity of the current collector low.
  • the aqueous binder includes a polymer formed by polymerization of at least one monomer selected from methyl methacrylate, ethyl methacrylate, acrylonitrile, ethyl acrylate, n-butyl acrylate, acrylamide, N-hydroxymethyl acrylamide, ethyl acetoacetate methacrylate, acrylic acid and acrylate, etc., which is not limited in the present application.
  • the weight average molecular weight of the aqueous binder can be 400,000-900,000.
  • the weight average molecular weight of the aqueous binder is too small, the viscosity of the slurry may be too low, the film-forming property of the slurry may be poor, and the insulating layer slurry may be leaked; if the weight average molecular weight of the aqueous binder is too large, the thickening effect of the aqueous binder may be enhanced, and the viscosity of the slurry may be too high and the fluidity may be poor, which may affect the dispersion of the insulating layer slurry.
  • the thickness of the insulating layer of the electrode plate can be 40-100 ⁇ m. It is understandable that the active layer of the present application can be thickly coated. Therefore, when the thickness of the insulating layer is too low, the strength of the insulating layer is too low, and the insulation performance may be affected; when the thickness of the insulating layer is too high, the relative content of the active material in the electrode plate decreases, which may affect the energy density of the electrochemical device.
  • the initial peel strength of the insulating layer can reach 20-150 N/m, indicating that the water-based adhesive used in the present application has a good bonding effect.
  • the inorganic material includes at least one of boehmite, aluminum oxide, insulating carbon black, magnesium oxide, silicon oxide, zirconium oxide and calcium oxide, etc., which is not limited in the present application.
  • the average particle size D50 of the inorganic material can be It is understood that if the average particle size D50 of the inorganic material is too small, the specific surface area will be too large, which may affect the peeling strength and make it difficult to peel off during recycling; if the average particle size D50 of the inorganic material is too large, the insulating layer formed may be relatively hard and brittle, which may affect the insulation effect and may cause greater damage to the current collector during coating.
  • D50 refers to the particle size corresponding to when the cumulative volume percentage of inorganic materials reaches 50%, that is, the median particle size of the volume distribution.
  • the particle size of inorganic materials can be measured using a laser diffraction particle size distribution measuring instrument (such as Malvern Mastersizer 3000).
  • the mass percentage of the aqueous binder can be 8-20% of the total mass of the insulating layer, and the mass percentage of the inorganic material can be 80-92%. It is understandable that when the content of the aqueous binder is too low, the film-forming property of the insulating layer is poor, which is not conducive to improving the coverage of the insulating layer; and when the content of the aqueous binder is too high, due to the high viscosity of the aqueous binder itself, the insulating layer may shrink more during the drying film-forming process, while the current collector basically does not shrink. The large difference in shrinkage between the two may cause a large area of the insulating layer to fall off from the current collector substrate.
  • the present application also provides an electrochemical device, which includes: a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet and/or the negative electrode sheet are the electrode sheets involved above.
  • the electrochemical device of the present application can be a capacitor, a primary battery or a secondary battery.
  • the electrochemical device can be a lithium ion capacitor, a lithium battery or a lithium ion battery, etc.
  • the present application does not limit the type of the electrochemical device.
  • the present application has no specific restrictions on the type of the diaphragm of the electrochemical device, and can be selected according to actual needs.
  • the diaphragm can be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, polymethyl methacrylate, and the like.
  • the electrolyte can be at least one of a gel electrolyte, a solid electrolyte and an electrolyte.
  • the electrolyte includes a lithium salt and a non-aqueous organic solvent.
  • the lithium salt can include at least one of lithium hexafluorophosphate (LiPF 6 ), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium trifluoromethylsulfonate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF 4 ), lithium bis(oxalate)borate (LiBOB), lithium difluorooxalateborate (LiODFB) and lithium perchlorate;
  • the non-aqueous organic solvent can include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), methyl acetate (MA), ethyl acetate (EA), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate (EB), etc.
  • the insulating layer slurries in Examples 1-9 and Comparative Example 2 were prepared according to the following method:
  • the weight average molecular weight of the water-based binder is 400,000-900,000.
  • the average particle size D50 of the inorganic material is 0.8-3.0 ⁇ m.
  • the specific types and contents of the water-based binder and the inorganic material are shown in Table 1.
  • the insulating layer slurry in Comparative Example 1 was prepared according to the following method:
  • PVDF Polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • the weight average molecular weight of PVDF is 900,000-1.2 million.
  • the average particle size D50 of boehmite is 0.8-3.0 ⁇ m.
  • the present application takes the positive electrode sheet as an example for illustration, and the positive electrode sheets in Examples 1-9 and Comparative Example 2 are prepared according to the following method:
  • the positive electrode active material lithium iron phosphate, binder methacrylic acid, and conductive agent Super-P were mixed in a mass ratio of 97:2:1, deionized water was added as a solvent, and a 30L double planetary mixer was used to stir and disperse to obtain a positive electrode slurry with a solid content of 65%.
  • a 30L extrusion coater was used to coat the electrode together with the insulating layer slurry.
  • the electrode sheet had a surface density of 195g/ m2 , wherein the film width was 150 ⁇ 0.5mm and the edge coating width was 8 ⁇ 0.3mm. This was the recovered positive electrode sheet.
  • the positive electrode sheet in Comparative Example 1 was prepared according to the following method:
  • the positive electrode active material lithium iron phosphate, binder PVDF, and conductive agent Super-P were mixed in a mass ratio of 97:2:1, NMP was added as a solvent, and a 30L double planetary mixer was used to stir and disperse to obtain a positive electrode slurry with a solid content of 65%.
  • a 30L extrusion coater was used to coat the electrode together with the insulating layer slurry.
  • the electrode sheet had an area density of 195g/ m2 , wherein the film width was 150 ⁇ 0.5mm and the edge coating width was 8 ⁇ 0.3mm. This was the recovered positive electrode sheet.
  • the insulating layer slurry was coated on the aluminum foil by scraping with a 100mm scraper, and after being baked in an oven, an edge-coated electrode sheet with a width of 100 ⁇ 0.5mm was obtained.
  • the insulating layers prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to initial peel strength tests and peel strength tests after water immersion, respectively.
  • the initial peel strength refers to the peel strength of the electrode pole piece just prepared.
  • the test method for peel strength can be: cut the obtained edge-coated pole piece into a long strip pole piece with a 15*150mm knife die, and peel it 180° with a high-speed rail tensile machine. The peeling length is 100mm, and the peeling strength can be obtained after completing the test.
  • the surface water is absorbed with dust-free paper, and then tested according to the above method.
  • Table 2 shows the test results of initial peel strength of the current collector and the insulating layer in the positive electrode sheets prepared in Examples 1-9 and Comparative Examples 1-2 and the peel strength after immersion in water at 25°C.
  • the peel strength after water immersion for 1 minute at 25°C is less than or equal to 7N/m, and further, the peel strength after water immersion for 1 minute at 25°C is less than or equal to 4N/m.
  • the insulating layer can be easily peeled off from the current collector by simply water immersion treatment. This is because the hydrophilic groups in the aqueous binder are similarly soluble in water, and the aqueous binder in the insulating layer can be well dissolved in water, so that the current collector can be efficiently recovered by simple water immersion, and the recovery rate of the current collector is also high.
  • the entire recycling process has low recycling costs and is green and environmentally friendly. Therefore, the electrode sheet prepared in the present application has a high recycling rate.
  • the initial peel strength of the insulating layer can reach 20-120N/m, indicating that the aqueous binder used in this application has a good bonding effect. It can be understood that the content of the aqueous binder also has a certain influence on the initial peel strength and the peel strength after water immersion. It can be seen from Examples 1-9 and Comparative Example 2 that the content of the aqueous binder is preferably 8-20%. In Comparative Example 2, when the content of the aqueous binder is greater than 20%, its initial peel strength cannot be tested.
  • the initial peel strength begins to decrease.
  • the water immersion time also has a certain effect on the peel strength.
  • the peel strength between the current collector and the insulating layer after soaking in water is inversely proportional to the water immersion time.
  • the peel strength between the current collector and the insulating layer after soaking in water decreases accordingly, but the difference is not large. It can be seen that when the electrode plate of the present application is recycled, the insulating layer can be easily peeled off from the current collector after being immersed in water for 1 minute at 25°C, thereby achieving simple and efficient recycling of the current collector.
  • the insulating layer in the present application contains an aqueous binder.
  • the hydrophilic groups in the aqueous binder can be used to dissolve in water in a similar manner to water, so that the insulating layer can be easily peeled off from the current collector after immersion in water for 1 minute at a preset temperature, wherein the peel strength of the current collector and the insulating layer is less than or equal to 7N/m.
  • the current collector can be efficiently recycled through simple water immersion, and the recovery rate of the current collector is also high.
  • the entire recycling process has low recycling costs and is green and environmentally friendly. Therefore, the electrode pole piece and electrochemical device prepared in the present application have a high recovery rate and are green and environmentally friendly.

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Abstract

一种电极极片和电化学装置，其中，电极极片包括：集流体、活性层和绝缘层；活性层涂覆在集流体至少一个表面上；绝缘层涂覆在集流体至少一个表面上，并连接在活性层的外周；绝缘层包括水性粘结剂和无机材料，绝缘层在预设温度下水浸1 min后的剥离强度小于或等于7 N/m。电极极片和电化学装置在回收的过程中，通过水浸处理，既可使得电极极片中的集流体与绝缘层具有较低的剥离强度，可以充分、高效地对集流体进行回收，使得电极极片以及电化学装置具有较高的回收率。

Description

电极极片和电化学装置
本申请要求于2022年10月08日提交中国专利局、申请号为2022112243352、申请名称为“电极极片和电化学装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及储能装置领域，尤其涉及一种电极极片和电化学装置。
背景技术
锂离子电池以其能量密度高、重量轻、使用寿命长等优点，在通讯设备以及新能源汽车等领域得到了广泛的应用。然而，由于锂离子电池循环寿命有限，每年都会产生大量的废旧锂离子电池。这些废旧锂离子电池中含有大量的不可再生且经济价值高的金属资源(例如，用作集流体的铝箔或者铜箔等)，因此对废弃锂离子电池的有效回收，具有较高的经济效益。
然而，在回收现有的电极极片的过程中发现，位于集流体边缘的绝缘层，难以从集流体中剥离，导致难以充分、高效地对集流体进行回收，从而导致电极极片的回收率较低。因此，如何制备得到回收率高的电极极片是本领域技术人员亟需解决的问题。
发明内容
本申请提供了一种电极极片和电化学装置，电极极片在回收的过程中，通过水浸处理，既可使得电极极片中的集流体与绝缘层具有较低的剥离强度，可以充分、高效地对集流体进行回收，使得电极极片具有较高的回收率。
本申请一方面提供了一种电极极片，包括：
集流体；
活性层，涂覆在集流体至少一个表面上；
绝缘层，涂覆在集流体至少一个表面上，并连接在活性层的外周；
绝缘层包括水性粘结剂和无机材料，绝缘层在预设温度下水浸1min后的剥离强度小于或等于7N/m。
本申请一方面提供了一种电化学装置，包括：正极极片、负极极片、隔膜和电解质，正极极片和/或负极极片为本申请一方面的电极极片。
实施本申请，将具有如下有益效果：
本申请提供的电极极片包括：集流体、活性层和绝缘层；活性层涂覆在集流体至少一个表面上；绝缘层涂覆在集流体至少一个表面上，并连接在活性层的外周；绝缘层包括水性粘结剂和无机材料。可以理解的是，绝缘层在预设温度下水浸1min后的剥离强度小于或等于7N/m，表明本申请中的电极极片在回收时，通过水浸处理，即可轻松实现将绝缘层从集流体中剥离，回收成本低廉，绿色环保，且集流体的回收率高，使得电极极片具有较高的回收率。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍。
图1为本申请提供的第一种电极极片的结构示意图；
图2为本申请提供的第二种电极极片的结构示意图；
图3为本申请提供的第三种电极极片的结构示意图；
图4为本申请提供的第四种电极极片的结构示意图；
图5为本申请提供的第五种电极极片的结构示意图。
附图标记：
电极极片10；
集流体1、活性层2、第一活性层21、第二活性层22、绝缘层3、第二表面31、第一表
面32。
具体实施方式
锂离子电池以其能量密度高、重量轻、使用寿命长等优点，在通讯设备以及新能源汽车等领域得到了广泛的应用。然而，由于锂离子电池循环寿命有限，每年都会产生大量的废旧锂离子电池。这些废旧锂离子电池中含有大量的不可再生且经济价值高的金属资源(例如，可以用作集流体的铝箔或者铜箔等)，因此对废弃锂离子电池的有效回收，具有较高的经济效益。
现有技术中，位于集流体边缘用于防止锂离子电池短路的绝缘层中，一般采用聚偏二氟乙烯(PVDF)作为粘结剂，N-甲基吡咯烷酮(NMP)作为溶剂。然而，在对包含PVDF的电极极片的回收过程中发现，位于集流体边缘的绝缘层，难以从集流体中剥离，导致难以充分、高效地对集流体进行回收。现有的针对包含PVDF的电极极片的回收方案中，在对集流体进行回收时，一般需要增加一道裁边工艺进行绝缘层的去除。这种回收方式，不但降低了集流体的回收率，而且也增加了回收成本。并且，NMP有一定的毒性，可能会对环境造成污染。
鉴于此，本申请提供了一种电极极片，可以从根源上解决上述提及的问题。
请参见图1和图2，图1为本申请提供的第一种电极极片的结构示意图，该电极极片的结构示意图为截面图；图2为本申请提供的第二种电极极片的结构示意图，该电极极片的结构示意图为俯视图。如图1和图2所示，该电极极片10可以包括集流体1、活性层2和绝缘层3；其中，活性层2可以涂覆在集流体1至少一个表面上；绝缘层3也可以涂覆在集流体1至少一个表面上，并连接在该活性层2的外周。
可以理解的是，上述的电极极片10中，活性层2和绝缘层3两者之间既不重叠，也不存在间隙。由于活性层2和绝缘层3两者之间形成相互平齐的结构，使得电极极片10能够有效地防止穿刺而造成的短路问题，从而可以提高电化学装置的安全性；此外，上述电极极片10的结构可以使电极极片10在防止穿刺而造成短路的同时，还能有利于提高电极极片10辊压的平整性和稳定性，避免电极极片10在冷压时存在过压的风险，进而保证电化学装置的性能。
本申请提供的电极极片，绝缘层在预设温度下水浸1min后的剥离强度小于或等于7N/m。其中，预设温度是预先设置的温度，具体的取值可以根据实际环境温度或者实际需求进行确定，示例地，预设温度可以是0-40℃。在一些具体的实施例中，预设温度可以是0℃、10℃、15℃、20℃、25℃、30℃、35℃、40℃等，但不仅限于所列举的数值，该数值范 围内其他未列举的数值同样适用。由此，可以表明本申请中的电极极片在回收时，通过水浸处理，即可轻松实现将绝缘层从集流体中剥离，回收成本低廉易，绿色环保，且集流体的回收率高，使得电极极片具有较高的回收率。此外，本申请的绝缘层还可以实现在25℃水浸1min后的剥离强度小于或等于4N/m，可以进一步表明本申请电极极片在回收时，可以实现简单高效地回收集流体。
可以理解的是，电极极片可以是正极极片或负极极片。当电极极片是正极极片时，相应地，其中的集流体和活性层分别为正极集流体(例如，铝箔等)和正极活性层；当电极极片是负极极片时，相应地，其中的集流体和活性层分别为负极集流体(例如，铜箔等)和负极活性层。
电极极片的活性层，通常包括电极活性材料、粘结剂和导电剂；当然，根据需要，活性层还可以包括一些可选的添加剂或助剂，例如，补锂剂等等。具体地，将电极活性材料、导电剂和粘结剂等组成的浆料涂覆到集流体至少一个表面上，可以是单层涂覆或者多层涂覆，本申请对此不做限定，再经干燥等后处理即可得本申请中的活性层。
对于正极极片而言，可以选用本领域常用的各种正极活性材料。在一些具体的实施例中，正极活性材料可以选自磷酸铁锂、锰酸锂、钴酸锂和镍钴锰三元材料以及镍钴铝三元材料等中的至少一种，本申请对此不做限定。对于负极极片而言，可以选用本领域常用的各种负极活性材料。在一些具体的实施例中，负极活性材料可以选自石墨、钛酸锂以及硅碳复合材料等中的至少一种，本申请对此不做限定。
活性层中的导电剂可以为导电碳材料、金属材料中的至少一种；在一些具体的实施例中，导电碳材料选自零维导电碳，如乙炔黑、导电炭黑(Super-P)；一维导电碳，如碳纳米管；二维导电碳，如导电石墨、石墨烯；三维导电碳，如还原后的氧化石墨烯中的至少一种；金属材料选自铝粉，铁粉以及银粉中的至少一种。为了防止在回收过程中，活性层与集流体出现难以剥离的情况，活性层中的粘结剂可以选用与绝缘层相同的水性粘结剂，其水性粘结剂的具体种类可以参考下文的描述，在此不再赘述。
电极极片中的绝缘层包括水性粘结剂和无机材料。当然，根据需要，绝缘层还可以包括一些可选的添加剂或者助剂，例如，疏散剂等等。
其中，水性粘结剂中可以包括亲水基团。在一些具体的实施例中，亲水基团可以包括但不限于羟基、羧基、氰基等中的至少一种。可以理解的是，本申请利用水性粘结剂中亲水基团的亲水性，可以使得电极极片在回收时，通过水浸即可轻松实现将绝缘层从集流体中剥离，从而可以充分、高效地对集流体进行回收。
如图3所示，在其中一个可能的实施方式中，电极极片10中的绝缘层3可以包括相背离的第二表面31和第一表面32，其中绝缘层3通过第一表面32粘结与集流体1中的至少一个表面上，水性粘结剂中的亲水基团的至少部分由第二表面31露出。可以理解的是，在采用水浸处理回收电极极片10时，绝缘层3中远离集流体1的第二表面31率先与水接触，第二表面31中露出的亲水基团与水反应，使得绝缘层3中包含的水性粘结剂快速溶解于水中，进而可以实现将绝缘层3与集流体1的高效剥离，使得电极极片10具有较高的回收率。
请参见图4和图5，在一些可能的实施例中，活性层2可以包括相连接的第一活性层21和第二活性层22，绝缘层3的部分覆盖至少部分第二活性层22。在一些可能的实施例中，第一活性层21和第二活性层22可以采用相同的材料，例如，第一活性层21和第二活性层22中包含相同的活性材料，活性材料的具体选用可以参考上文的描述，在此不再赘述。此外，第一活性层21和第二活性层22还可以是一体结构，如此可以提高活性层2的涂覆效率，进 而提高电极极片10的加工效率。当然，在另一些可能的实施例中，第一活性层21和第二活性层22可以采用不同的材料，使得与绝缘层3连接的第二活性层22的能量密度小于第一活性层21的能量密度，当电极极片10发生碰撞或穿刺时，第二活性层22能够增加集流体与其他接触物之间的接触电阻，从而降低电极极片10短路的风险；进一步地，本申请提供的电极极片，通过绝缘层3的部分的第二覆盖至少部分第二活性层22，能够避免两者交界处的集流体1暴露，还可以确保绝缘层3对集流体1的覆盖度，进一步提高电极极片10的安全性能。
请参见图4，在一些可能的实施方式中，第一活性层21和第二活性层22可以沿长度方向x设置，并且在沿远离第一活性层21的方向，第二活性层22的厚度逐渐递减。可以理解的是，在辊压工序中，在沿长度方向x，压辊由集流体1的一端依次作用于第二活性层22和第一活性层体21，由于在沿远离第一活性层21的方向，第二活性层22的厚度逐渐递减，进而使得压辊作用于第二活性层22的辊压力由小到大依次递增，从而可以缓解第二活性层22受到的辊压力，降低第二活性层22出现掉粉现象的概率，以进一步提高电极极片10的安全性能。此外，由于第二活性层22的厚度向远离第一活性层21的方向递减，绝缘层3的第二表面31在沿长度方向x大于第一表面32，使得第二表面31的亲水基团增加，在采用水浸处理回收电极极片10时，具有较多亲水基团的第二表面31率先与水接触，进而可以实现将绝缘层3与集流体1的高效剥离，使得电极极片10具有较高的回收率。
请参见图5，在一些可能的实施方式中，第一活性层21和第二活性层22可以沿厚度方向y设置，第二活性层22与集流体1连接，第一活性层21远离集流体1。其中，绝缘层3远离集流体1的一面至少部分被第一活性层21靠近第二活性层22的一面覆盖。如此，可以使得绝缘层与第一活性层和第二活性层连接更紧密，使得在穿刺或者碰撞这种破坏力很大的外力下，绝缘层3也很难脱落，可以防止出现漏出集流体1的情况，使得其电极极片10更加安全。
其中，亲水基团的质量百分含量可以大于或等于水性粘结剂总质量的50％。可以理解的是，当水性粘结剂中包含的亲水基团的质量百分含量过低时，水浸后的电极极片中的集流体和绝缘层之间仍具有较高的剥离强度，不利于集流体与绝缘层的剥离，进而使得集流体的回收效率和回收纯度都较低。
在一些具体的实施例中，水性粘结剂包括甲基丙烯酸甲酯、甲基丙烯酸乙酯、丙烯腈、丙烯酸乙酯、丙烯酸正丁酯、丙烯酰胺、N-羟甲基丙烯酰胺、甲基丙烯酸乙酰乙酸乙酯、丙烯酸和丙烯酸酯等中的至少一种单体聚合形成的聚合物，本申请对此不做限定。其中，水性粘结剂的重均分子量可以为40-90万。可以理解的是，水性粘结剂的重均分子量过小，可能会导致浆料粘度过低，浆料成膜性差，还可能会导致绝缘层浆料漏涂；水性粘结剂的重均分子量过大，水性粘结剂的增稠作用增强，可能会导致浆料粘度过高、流动性变差，影响绝缘层浆料的分散。
电极极片的绝缘层的厚度可以是40-100μm。可以理解的是，本申请的活性层可以采用厚涂处理，因此，当绝缘层的厚度过低时，绝缘层强度过低，绝缘的性能可能受到影响；当绝缘层的厚度过高时，电极极片中的活性物质相对含量下降，可能会影响电化学装置的能量密度。
此外，绝缘层的初始剥离强度可以到达20-150N/m，表明本申请采用的水性粘结剂具有很好的粘结效果。
在一些具体的实施例中，无机材料包括勃姆石、氧化铝、绝缘炭黑、氧化镁、氧化硅、氧化锆和氧化钙等中的至少一种，本申请对此不做限定。其中，无机材料的平均粒径D50可 以为0.3-20μm。可以理解的是，无机材料的平均粒径D50过小，比表面积会过大，可能会影响剥离强度，导致回收时难以剥落；无机材料的平均粒径D50过大，形成的绝缘层可能比较硬脆，可能会影响绝缘效果，在涂覆的时候还可能会给集流体造成较大的损坏。
可以理解的是，D50指无机材料累计体积百分数达到50％时所对应的粒径，即体积分布中位粒径。无机材料的粒径可以使用激光衍射粒度分布测量仪(例如Malvern Mastersizer3000)进行测量。
水性粘结剂的质量百分含量可以为绝缘层总质量的8-20％，无机材料的质量百分含量可以为80-92％。可以理解的是，当水性粘结剂含量过低时，绝缘层成膜性差，不利于绝缘层覆盖度的提升；而当水性粘结剂含量过高，由于水性粘结剂本身的粘度高，可能会导致绝缘层在烘干成膜过程中收缩程度增大，而集流体基本不收缩，二者收缩率差异大，可能会导致绝缘层大面积从集流体基材上脱落。
此外，本申请还提供了一种电化学装置，该电化学装置包括：正极极片、负极极片、隔膜和电解质；其中，正极极片和/或负极极片为上述涉及的电极极片。本申请的电化学装置可以是电容器、一次电池或二次电池。例如，电化学装置可以为锂离子电容器、锂电池或锂离子电池等等，本申请对于电化学装置的类型不做限定。
本申请对该电化学装置的隔膜的种类没有具体限制，可以根据实际需求进行选择。具体地，隔膜可以选自聚乙烯、聚丙烯、聚偏氟乙烯、聚甲基丙烯酸甲酯等中的至少一种。
其中，电解质可以是凝胶电解质、固态电解质和电解液中至少一种。以锂离子电池为例，电解质包括锂盐和非水有机溶剂。锂盐可以包括六氟磷酸锂(LiPF6)、双三氟甲基磺酰亚胺锂(LiTFSI)、三氟甲基磺酸锂、双氟磺酰亚胺锂(LiFSI)、四氟硼酸锂(LiBF4)、二草酸硼酸锂(LiBOB)、二氟草酸硼酸锂(LiODFB)以及高氯酸锂等中的至少一种；非水有机溶剂可以包括碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、乙酸甲酯(MA)、乙酸乙酯(EA)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸乙酯(EB)等中的至少一种。
下面结合实施例，进一步阐述本申请。应理解，本申请提供的实施例仅仅是帮助理解本申请，不应视为对本申请的具体限制。在实施例中仅示出电化学装置为锂离子电池的情况，但本申请不限于此。
为便于理解本申请，本申请列举实施例如下。本领域技术人员应该明了实施例中未注明具体条件者，按照常规条件或制造商建议的条件进行。所用试剂或仪器未注明生产厂商者，均为可以通过市售购买获得的常规产品。
实施例1-9以及对比例2中绝缘层浆料均按照下述方法进行制备：
将水性粘结剂和无机材料进行混合后，加入去离子水，搅拌均匀至浆料粘度稳定，得到固含量为10-40％的绝缘层浆料，将绝缘层浆料倒入挤压涂布机边涂缓存罐。其中，水性粘结剂的重均分子量为40-90万。无机材料的平均粒径D50为0.8-3.0μm。其中，水性粘结剂和无机材料的具体种类及其含量示出在表1中。
对比例1中绝缘层浆料按照下述方法进行制备：
将聚偏氟乙烯(PVDF)和勃姆石，按质量比为8％：92％进行混合，加入N-甲基吡咯烷酮(NMP)，搅拌均匀至浆料粘度稳定，得到固含量为10-40％的绝缘层浆料。其中，PVDF的重均分子量为90-120万。勃姆石的平均粒径D50为0.8-3.0μm。
本申请以电极极片为正极极片为例，进行举例说明，实施例1-9以及对比例2中的正极极片均按照下述方法进行制备：
将正极活性材料磷酸铁锂、粘结剂甲基丙烯酸、导电剂Super-P，按质量比为97:2:1进行混合，加入去离子水作为溶剂，用30L双行星搅拌机搅拌分散得到固含量为65％的正极浆料，利用30L挤压涂布机连同绝缘层浆料一起进行极片涂布，极片面密度为195g/m2的极片，其中，膜宽为150±0.5mm，边涂宽幅为8±0.3mm，此为回收得到的正极极片。为了更好的测试不同边涂的极片剥离力，将不同种类的绝缘层浆料用100mm刮刀以刮涂的方式涂覆在铝箔上，经过烘箱烘烤后得到宽度为100±0.5mm的边涂极片。
对比例1中的正极极片按照下述方法进行制备：
将正极活性材料磷酸铁锂、粘结剂PVDF、导电剂Super-P，按质量比为97:2:1进行混合，加入NMP作为溶剂，用30L双行星搅拌机搅拌分散得到固含量为65％的正极浆料，利用30L挤压涂布机连同绝缘层浆料一起进行极片涂布，极片面密度为195g/m2的极片，其中，膜宽为150±0.5mm，边涂宽幅为8±0.3mm，此为回收得到的正极极片。为了更好的测试不同边涂的极片剥离力，将绝缘层浆料用100mm刮刀以刮涂的方式涂覆在铝箔上，经过烘箱烘烤后得到宽度为100±0.5mm的边涂极片。
其中，实施例1-9和对比例1-2中绝缘层的水性粘结剂和无机材料的具体种类及其含量，以及绝缘层的厚度示出在表1中。在表1中，水性粘结剂和无机材料的含量均为基于绝缘层的总质量计算得到的质量百分数。
表1

以预设温度为25℃为例，将实施例1-9和对比例1-2制备得到的绝缘层分别进行初始剥离强度测试和水浸后的剥离强度测试。可以理解的是，初始剥离强度是指刚制备好的电极极片的剥离强度。其中，剥离强度的测试方法可以是：将所得边涂极片用15*150mm的刀模裁剪成长条状极片，用高铁拉力机进行180°剥离，剥离长度为100mm，完成测试后即可得到剥离强度。泡水之后的边涂极片在剥离强度测试之前，用无尘纸将表面水吸干，后按照上述方法进行测试。
表2为实施例1-9和对比例1-2制备得到正极极片中集流体和绝缘层的初始剥离强度测试和25℃水浸后的剥离强度的测试结果。
表2
从上述表2中的相关数据分析可知，相对其他实施例而言，对比例1的集流体与绝缘层的初始剥离强度较低，然而25℃下水浸后的剥离强度较高。且可以看出，对比例1中集流体与绝缘层的初始剥离强度与水浸后的剥离强度几乎没有发生变化。这可能的原因是因为PVDF作为粘结剂，NMP作为溶剂，两者均表现为亲油性，难以在水中溶解，因此，25℃下水浸5min也很难实现将绝缘层从集流体上剥离。相对应地，在实施例1-9中，25℃下水浸1min后的剥离强度均小于或等于7N/m，更进一步地，25℃下水浸1min后的剥离强度均小于或等于4N/m。可以看出，仅仅通过简单的水浸处理，即可轻松实现将绝缘层从集流体中剥离。这是因为水性粘结剂中的亲水基团与水相似相溶，绝缘层中的水性粘结剂可以很好地溶解在水中，从而可以实现通过简单的水浸，即可以高效回收集流体，且集流体的回收率也较高。此外，整个回收过程，回收成本低廉，绿色环保。因此，本申请制备得到的电极极片具有较高的回收率。
此外，从上述表2中的相关数据分析可知，绝缘层的初始剥离强度可以到达20-120N/m，表明本申请采用的水性粘结剂具有很好的粘结效果。可以理解的是，水性粘结剂的含量对初始剥离强度和水浸后的剥离强度也有一定的影响。通过实施例1-9和对比例2可知，水性粘结剂的含量以8-20％为宜。在对比例2中，当水性粘结剂含量大于20％，无法测试其初始剥离强度，这是水性粘结剂本身的粘度高，可能会导致绝缘层在烘干成膜过程中收缩程度增大，而集流体基本不收缩，二者收缩率差异大，可能会导致绝缘层大面积从集流体基材上脱落，使得初始剥离强度无法测试。
从上述表2中的相关数据分析可知，无机材料的不同，也可能会影响水浸后的剥离效果，其中使用勃姆石作为无机材料，水浸后更容易剥离，使用绝缘炭黑作为无机材料，水浸时间需要延长，但是相差不大。水性粘结剂中酯类化合物单体不宜过多，增加酯类化合物单体的比例超过30％时，水性粘结剂在同等添加量条件下，25℃下水浸后无法用直接擦拭的方法轻松剥离。集流体与绝缘层的初始剥离强度随着绝缘层的厚度呈现先增大后减小的趋势，当绝缘层厚度增加到80μm以上，初始剥离强度开始下降。此外，从上述表2中的相关数据分析可知，水浸时间对剥离强度也有一定的影响。一般而言，泡水后集流体和绝缘层之间的剥离强度与水浸时间呈反比，随着水浸时间的延长，泡水后集流体和绝缘层之间的剥离强度随之降低，但是相差不大。可以看出，本申请的电极极片在回收时，25℃下通过水浸1min后，即可轻松实现将绝缘层从集流体中剥离，从而可以实现简单高效地回收集流体。
综上所述，本申请中的绝缘层包含水性粘结剂，在电极极片回收的过程中，可以利用水性粘结剂中的亲水基团与水相似相溶的机理，实现在预设温度下水浸1min后轻松实现将绝缘层从集流体中剥离，其中，集流体和绝缘层的剥离强度均小于或等于7N/m。也就是说，通过简单的水浸，即可以高效回收集流体，且集流体的回收率也较高。此外，整个回收过程，回收成本低廉，绿色环保。因此，本申请制备得到的电极极片以及电化学装置具有较高的回收率且绿色环保。
最后应当说明的是，以上实施例仅用以说明本申请的技术方案而非对本申请保护范围的限制，尽管参照较佳实施例对本申请作了详细说明，本领域的普通技术人员应当理解，可以对本申请的技术方案进行修改或者等同替换，而不脱离本发明技术方案的实质和范围。

Claims (10)

  1. 一种电极极片，包括：
    集流体；
    活性层，涂覆在所述集流体至少一个表面上；
    绝缘层，涂覆在所述集流体至少一个表面上，并连接在所述活性层的外周；
    所述绝缘层包括水性粘结剂和无机材料，所述绝缘层在预设温度下水浸1min后的剥离强度小于或等于7N/m。
  2. 根据权利要求1所述的电极极片，其中，所述水性粘结剂包括亲水基团，所述绝缘层包括相背离的第一表面和第二表面，所述绝缘层通过所述第一表面粘结于所述集流体至少一个表面上，所述亲水基团的至少部分由所述第二表面露出；所述亲水基团的质量百分含量大于或等于所述水性粘结剂总质量的50％。
  3. 根据权利要求1或2所述的电极极片，其中，所述活性层包括相连接的第一活性层和第二活性层，所述绝缘层的部分覆盖至少部分所述第二活性层。
  4. 根据权利要求1至3任一项所述的电极极片，其中，所述水性粘结剂包括甲基丙烯酸甲酯、甲基丙烯酸乙酯、丙烯腈、丙烯酸乙酯、丙烯酸正丁酯、丙烯酰胺、N-羟甲基丙烯酰胺、甲基丙烯酸乙酰乙酸乙酯、丙烯酸和丙烯酸酯中的至少一种单体聚合形成的聚合物。
  5. 根据权利要求1至4任一项所述的电极极片，其中，所述无机材料包括勃姆石、氧化铝、绝缘炭黑、氧化镁、氧化硅、氧化锆和氧化钙中的至少一种。
  6. 根据权利要求1至5任一项所述的电极极片，其中，所述水性粘结剂的质量百分含量为所述绝缘层总质量的8％-20％，所述无机材料的质量百分含量为80％-92％。
  7. 根据权利要求1至6任一项所述的电极极片，其中，所述水性粘结剂的重均分子量为40万-90万。
  8. 根据权利要求1至7任一项所述的电极极片，其中，所述无机材料的平均粒径D50为0.3μm-20μm。
  9. 根据权利要求1至8任一项所述的电极极片，其中，所述绝缘层在25℃下水浸1min后的剥离强度小于或等于4N/m。
  10. 一种电化学装置，包括：
    正极极片、负极极片、隔膜和电解质；
    所述正极极片和/或所述负极极片为权利要求1至9中任一项所述的电极极片。
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