WO2020258754A1 - 一种电极极片、电化学装置及其装置 - Google Patents

一种电极极片、电化学装置及其装置 Download PDF

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Publication number
WO2020258754A1
WO2020258754A1 PCT/CN2019/125061 CN2019125061W WO2020258754A1 WO 2020258754 A1 WO2020258754 A1 WO 2020258754A1 CN 2019125061 W CN2019125061 W CN 2019125061W WO 2020258754 A1 WO2020258754 A1 WO 2020258754A1
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Prior art keywords
layer
current collector
conductive
pole piece
active material
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PCT/CN2019/125061
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English (en)
French (fr)
Inventor
李伟
李静
薛庆瑞
张子格
张扬
杨献伟
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宁德时代新能源科技股份有限公司
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Priority to EP19934632.1A priority Critical patent/EP3916845B1/en
Publication of WO2020258754A1 publication Critical patent/WO2020258754A1/zh
Priority to US17/540,263 priority patent/US20220093932A1/en

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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/72—Grids
    • 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
    • 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
    • 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
    • H01M4/62—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/626—Metals
    • 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
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • 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
    • H01M4/666—Composites in the form of mixed materials
    • 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
    • H01M4/668—Composites of electroconductive material and synthetic resins
    • 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
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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

  • This application relates to the field of batteries, in particular, to an electrode pole piece, an electrochemical device and a device thereof.
  • Lithium-ion batteries are widely used in electric vehicles and consumer electronic products due to their advantages of high energy density, high output power, long cycle life and low environmental pollution. With the continuous expansion of the application range of lithium-ion batteries, the requirements for the weight energy density and volume energy density of lithium-ion batteries are getting higher and higher.
  • lithium-ion batteries with higher mass energy density and volumetric energy density
  • improvements are usually made to lithium-ion batteries: (1) Choose a positive electrode material or negative electrode material with a high specific discharge capacity; (2) Optimize the mechanical design of lithium-ion batteries , To minimize its volume; (3) Choose a positive pole piece or negative pole piece with high compaction density; (4) Reduce the weight of each component of the lithium ion battery.
  • the improvement of the current collector is usually to select a lighter or thinner current collector.
  • a perforated current collector or a metal-plated plastic current collector can be used.
  • some embodiments of the present application provide an electrode pad, an electrochemical device and the device thereof.
  • the present application provides an electrode pad, including a current collector, an electrode active material layer provided on at least one surface of the current collector, an electrical connection member electrically connected to the current collector, and the electrode active material
  • the layer is arranged on the main part of the current collector, this area is called the diaphragm area, the electrical connection member and the current collector are welded and connected at the edge of the current collector, and the welding area is called the transfer welding area.
  • the transition area of the uncoated electrode active material layer of the current collector between the diaphragm area and the transfer welding area is called the extension area.
  • the current collector includes a support layer and a conductive layer disposed on at least one surface of the support layer,
  • the single-sided thickness D2 of the conductive layer satisfies: 30nm ⁇ D2 ⁇ 3 ⁇ m
  • the support layer is a polymer material layer or a polymer composite material layer, and is between the current collector and the electrode active material layer in the diaphragm area of the current collector
  • a conductive primer layer containing a binder and a conductive material is provided in the space and on the surface of the extension area of the current collector.
  • the present application provides an electrochemical device, including a positive pole piece, a negative pole piece, a separator and an electrolyte, wherein the positive pole piece and/or the negative pole piece are the electrode described in the first aspect of the application Pole piece.
  • the present application also provides a device, including the electrochemical device described in the second aspect of the present application.
  • the electrochemical device can be used as a power source for the device, and the electrochemical device can also be used as the device. Energy storage unit.
  • the electrode pole piece of the present application uses a composite current collector. Because the composite current collector has a thinner conductive layer and the support layer is a polymer material or a polymer composite material, it can significantly improve the energy density of the electrochemical device, such as Weight energy density.
  • the composite current collector has a thinner conductive layer, the metal burr generated in abnormal situations such as nail penetration is small, and it has a polymer material or polymer composite material as a support layer, so it is Under abnormal conditions, the short-circuit resistance is larger than that of the traditional metal current collector, so the nail penetration safety performance of the electrochemical device is greatly improved.
  • a conductive primer layer containing a binder and a conductive material is provided on the surfaces of the diaphragm area and the extension area of the composite current collector.
  • the conductive primer layer can improve the bonding force between the current collector and the active material, ensure that the electrode active material layer is more firmly set on the surface of the composite current collector, and improve the flow capacity and electrochemical performance of the electrode pole piece, by improving At the interface of the conductive layer, the conductive bottom coating can make the electrons conduct more smoothly on the entire pole piece, reduce polarization, increase the overcurrent capacity of the pole piece, and also solve the uneven current distribution on the pole piece and local polarization. Larger problem; so that the pole piece using the composite current collector has comparable or even better electrical properties than the pole piece using the conventional metal foil current collector.
  • the electrode pole piece of the present application and the electrochemical device (such as a lithium ion battery) containing the electrode pole piece have both good energy density, electrochemical performance (especially good flow capacity) and safety performance.
  • the device of the present application includes the electrochemical device provided by the present application, and thus has at least the same advantages as the electrochemical device.
  • FIG. 1 is a schematic cross-sectional structure diagram of a positive electrode current collector according to a specific embodiment of the application.
  • FIG. 2 is a schematic cross-sectional structure diagram of a positive electrode current collector according to another specific embodiment of this application.
  • FIG. 3 is a schematic cross-sectional structure diagram of a positive electrode current collector according to another specific embodiment of this application.
  • FIG. 4 is a schematic cross-sectional structure diagram of a positive electrode current collector according to another specific embodiment of this application.
  • FIG. 5 is a schematic cross-sectional structure diagram of a negative electrode current collector according to a specific embodiment of this application.
  • FIG. 6 is a schematic cross-sectional structure diagram of a negative electrode current collector according to another specific embodiment of this application.
  • FIG. 7 is a schematic cross-sectional structure diagram of a negative electrode current collector according to another specific embodiment of this application.
  • FIG. 8 is a schematic cross-sectional structure diagram of a negative electrode current collector according to another specific embodiment of this application.
  • FIG. 9 is a schematic diagram of a cross-sectional structure of a diaphragm area of a positive pole piece according to a specific embodiment of this application.
  • FIG. 10 is a schematic diagram of a cross-sectional structure of a diaphragm area of a positive pole piece according to another specific embodiment of this application.
  • FIG. 11 is a schematic diagram of a cross-sectional structure of a diaphragm area of a positive pole piece according to another specific embodiment of this application.
  • FIG. 12 is a schematic diagram of a cross-sectional structure of a diaphragm area of a positive pole piece according to another specific embodiment of this application.
  • FIG. 13 is a schematic diagram of a cross-sectional structure of a diaphragm area of a negative electrode sheet according to a specific embodiment of this application.
  • FIG. 14 is a schematic diagram of a cross-sectional structure of a diaphragm area of a negative pole piece according to another specific embodiment of this application.
  • FIG. 15 is a schematic diagram of a cross-sectional structure of the diaphragm area of the negative pole piece according to another specific embodiment of this application.
  • FIG. 16 is a schematic diagram of a cross-sectional structure of a diaphragm area of a negative pole piece according to another specific embodiment of this application.
  • FIG. 17A is a schematic top view of a positive pole piece according to a specific embodiment of this application.
  • FIG. 17B is a schematic top view of a positive pole piece according to another specific embodiment of this application.
  • FIG. 17C is a schematic top view of a positive pole piece according to another specific embodiment of this application.
  • FIG. 17D is a schematic top view of a positive pole piece according to another specific embodiment of this application.
  • FIG. 17E is a schematic cross-sectional view of the positive pole piece of a specific embodiment (for example, FIG. 17C) shown in FIGS. 17A to 17D.
  • FIG. 18 is a schematic cross-sectional structure diagram of a positive pole piece according to a specific embodiment of this application.
  • FIG. 19 is a schematic top view of a positive pole piece according to a specific embodiment of this application.
  • 20 is a perspective view of an electrochemical device as a lithium ion secondary battery according to an embodiment of the present application.
  • Fig. 21 is an exploded view of the lithium ion secondary battery shown in Fig. 20.
  • Fig. 22 is a perspective view of a battery module according to an embodiment of the present application.
  • Fig. 23 is a perspective view of a battery pack according to an embodiment of the present application.
  • Fig. 24 is an exploded view of the battery pack shown in Fig. 23.
  • Fig. 25 is a schematic diagram of a device according to a specific embodiment of the present application.
  • the first aspect of the application relates to an electrode pole piece, comprising a current collector, an electrode active material layer provided on at least one surface of the current collector, an electrical connection member electrically connected to the current collector, and the electrode active material
  • the layer is arranged on the main part of the current collector, this area is called the diaphragm area, the electrical connection member and the current collector are welded and connected at the edge of the current collector, and the welding area is called the transfer welding area.
  • the transition area of the uncoated electrode active material layer of the current collector between the diaphragm area and the transfer welding area is called the extension area.
  • the current collector includes a support layer and a conductive layer disposed on at least one surface of the support layer,
  • the single-sided thickness D2 of the conductive layer satisfies: 30nm ⁇ D2 ⁇ 3 ⁇ m
  • the support layer is a polymer material layer or a polymer composite material layer, and is between the current collector and the electrode active material layer in the diaphragm area of the current collector
  • a conductive primer layer containing a binder and a conductive material is provided in the space and on the surface of the extension area of the current collector.
  • the electrode pole piece may be a positive pole piece or a negative pole piece.
  • the current collector and the electrode active material layer therein are the positive electrode current collector and the positive electrode active material layer, respectively.
  • the electrode pole piece is a negative pole piece, correspondingly, the current collector and the electrode active material layer therein are the negative electrode current collector and the negative electrode active material layer, respectively.
  • the current collector used for the electrode pole piece of the first aspect of the present application is a composite current collector, which is a composite of at least two materials.
  • the current collector includes a support layer and a conductive layer provided on at least one surface of the support layer, and the single-sided thickness D2 of the conductive layer satisfies: 30nm ⁇ D2 ⁇ 3 ⁇ m. Therefore, the conductive layer is the conductive layer in the current collector.
  • the thickness D2 of the conductive layer is much smaller than the thickness of metal current collectors such as Al foil or Cu foil commonly used in the prior art (the thickness of commonly used Al foil and Cu foil metal current collectors is usually 12 ⁇ m and 8 ⁇ m), so the use of the The mass energy density and volume energy density of the electrochemical device (such as lithium battery) of the pole piece.
  • the composite current collector can also greatly improve the nail penetration safety performance of the pole piece. This is because the composite current collector has a thinner conductive layer, so in abnormal situations such as nail penetration, the metal burr produced is smaller, and it is also With polymer materials or polymer composite materials as the support layer, the short-circuit resistance is greater than traditional metal current collectors under abnormal conditions such as nail penetration. These factors work together to greatly improve the nail penetration safety performance of the electrochemical device.
  • the composite current collector has poorer conductivity, and the conductive layer is easy to be in the pole piece processing process. Damage occurs in the electrochemical device, which in turn affects the electrochemical performance of the electrochemical device. Therefore, in the electrode pad of the present application, a conductive primer layer containing a conductive material and a binder is provided between the current collector in the diaphragm area of the composite current collector and the electrode active material layer to solve the above technical problems.
  • the conductive primer layer effectively repairs the surface of the current collector and constructs a conductive network between the current collector, the conductive primer layer and the active material, which improves the efficiency of electron transmission and reduces the resistance of the pole piece containing the composite current collector, thereby effectively reducing the DC of the battery.
  • the internal resistance (DCR) improves the power performance of the cell, and ensures that the cell is not prone to large polarization and lithium evolution during long-term cycling, which effectively improves the long-term reliability of the cell; in addition, the conductive bottom
  • the coating can also improve the interface between the composite current collector and the electrode active material layer, improve the adhesion between the current collector and the active material, and ensure that the electrode active material layer is more firmly set on the surface of the composite current collector.
  • the surface of the conductive layer of the composite current collector is electrically connected to the tab (ie, the electrical connection member), since the conductive layer is thin and easy to be damaged, the flow capacity of the electrode pole piece (especially at the tab) is poor. During the operation of the battery, more heat is generated and the polarization is greater. Therefore, in the electrode pad of the present application, in addition to providing a conductive primer layer between the current collector and the electrode active material layer in the diaphragm area of the composite current collector, the surface of the extension area of the current collector is also provided with a conductive material and Adhesive conductive primer to solve the above technical problems.
  • the conductive primer coating can improve the current flow capacity and electrochemical performance of the electrode pole piece.
  • the conductive primer coating can make the electrons conduct more smoothly on the entire pole piece, reducing polarization and increasing the pole piece.
  • the overcurrent capability can also solve the problems of uneven current distribution on the pole piece and large local polarization.
  • the electrode pole piece of the present application and the electrochemical device (such as a lithium ion battery) containing the electrode pole piece have both good energy density, electrochemical performance (especially good flow capacity) and safety performance.
  • the conductive primer layer of the extension area can be increased. Thickness or increase in the content of conductive material, or additional support and protection layer on the surface of the conductive primer, can prevent the current collector from being mechanically damaged and affect the conductive performance of the pole piece, thereby further improving the overcurrent of the pole piece ability.
  • the thickness of the conductive primer layer in the extension region of the current collector is greater than the thickness of the conductive primer layer in the diaphragm region, or the extension of the current collector.
  • the content of the conductive material in the conductive undercoat layer of the area is higher than the content of the conductive material in the conductive undercoat layer of the diaphragm area, or the surface of the conductive undercoat layer in the extension area of the current collector is also provided with support protection
  • the supporting protective layer is an organic insulating layer or an inorganic insulating layer.
  • the support layer (polymer material or polymer composite material) of the composite current collector has a greater rebound degree than the traditional metal current collector, if you follow the traditional process, the surface of the composite current collector is coated and then subjected to a rolling process
  • the compaction may also cause a series of other problems. Due to the rebound of the support layer, the edges on both sides of the pole piece will be warped, causing the pole piece to be curved as a whole, which will cause the pole piece to deform. Deformation of the pole piece may cause separation of the electrode active material layer from the composite current collector, damage to the conductive layer, peeling of the conductive layer from the support layer, etc., thereby degrading the electrochemical performance of the pole piece.
  • the electrode pole piece prepared by the composite current collector is prone to technical problems such as large internal resistance and large polarization.
  • the lateral direction of the active material layer of the electrode pole piece is also determined. The material distribution is specially designed.
  • the electrode pole piece maintains a good pole piece flatness after rolling, eliminates or reduces technical problems such as large internal resistance and large polarization of the pole piece, and is beneficial to protect the conductive layer from being damaged, thereby making the electrode
  • the sheet has good flow capacity and the electrochemical device has good electrochemical performance.
  • the conductive layer plays a role of conduction and current collection, and is used to provide electrons to the electrode active material layer.
  • the material of the conductive layer is selected from at least one of metal conductive materials and carbon-based conductive materials.
  • the metal conductive material is preferably at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy.
  • the carbon-based conductive material is preferably at least one of graphite, acetylene black, graphene, and carbon nanotubes.
  • the material of the conductive layer is preferably a metal conductive material, that is, the conductive layer is preferably a metal conductive layer.
  • the current collector is the positive electrode current collector
  • aluminum is usually used as the material of the conductive layer
  • copper is usually used as the material of the conductive layer.
  • the conductivity of the conductive layer When the conductivity of the conductive layer is poor or the thickness is too small, the internal resistance of the battery will be large, and the polarization will be large. When the thickness of the conductive layer is too large, it is not enough to improve the weight energy density and volume energy density of the battery. Effect.
  • the single-sided thickness of the conductive layer is D2, and D2 preferably satisfies: 30nm ⁇ D2 ⁇ 3 ⁇ m, more preferably 300nm ⁇ D2 ⁇ 2 ⁇ m, most preferably 500nm ⁇ D2 ⁇ 1.5 ⁇ m; in order to better ensure the lightweight performance of the current collector It also has good electrical conductivity.
  • the upper limit of the single-sided thickness D2 of the conductive layer may be 3 ⁇ m, 2.5 ⁇ m, 2 ⁇ m, 1.8 ⁇ m, 1.5 ⁇ m, 1.2 ⁇ m, 1 ⁇ m, 900 nm
  • the lower limit of the single-sided thickness D2 of the conductive layer may be 800nm, 700nm, 600nm, 500nm, 450nm, 400nm, 350nm, 300nm, 100nm, 50nm, 30nm
  • the range of the single-sided thickness D2 of the conductive layer can be composed of any upper limit or lower limit.
  • cracks exist in the conductive layer of the electrode pad described in this application.
  • the cracks in the conductive layer usually exist irregularly in the conductive layer. They can be elongated cracks, cross-shaped cracks, divergent cracks, etc.; they can be cracks that penetrate the entire conductive layer, or they can be in the conductive layer. Cracks formed on the surface layer. Cracks in the conductive layer are usually caused by the rolling during the pole piece processing, the excessive amplitude of the welding tab, and the excessive tension of the substrate winding.
  • the conductive layer may be formed on the support layer by at least one of mechanical rolling, bonding, vapor deposition, electroplating, and electroless plating.
  • the vapor deposition method is preferably physical vapor deposition (Physical Vapor Deposition). , PVD); physical vapor deposition method preferably at least one of evaporation method, sputtering method; evaporation method preferably vacuum evaporation method (vacuum evaporation), thermal evaporation method (Thermal Evaporation Deposition), electron beam evaporation method (electron beam evaporation) At least one of methods, EBEM), and the sputtering method is preferably a magnetron sputtering (Magnetron sputtering).
  • At least one of vapor deposition, electroplating, or electroless plating is preferred to make the bonding between the support layer and the conductive layer stronger.
  • the supporting layer plays a role of supporting and protecting the conductive layer. Since the support layer generally uses organic polymer materials or polymer composite materials, the density of the support layer is usually less than the density of the conductive layer, so that the weight energy density of the battery can be significantly improved compared with traditional metal current collectors.
  • the metal layer adopts a metal layer with a smaller thickness, which can further increase the weight energy density of the battery.
  • the support layer can play a good bearing and protection effect on the conductive layer on its surface, it is not easy to produce the common pole piece fracture phenomenon in traditional current collectors.
  • the material of the support layer is selected from at least one of insulating polymer materials, insulating polymer composite materials, conductive polymer materials, and conductive polymer composite materials.
  • the insulating polymer material is for example selected from polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, aramid, polyphenylene diamide, acrylonitrile -Butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, poly Phenyl sulfide, polyvinylidene fluoride, silicone rubber, polycarbonate, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its cross-linked products, polyethylene glycol and its At least one of cross-linked products.
  • the insulating polymer composite material is, for example, selected from composite materials formed by insulating polymer materials and inorganic materials, and the inorganic material is preferably at least one of ceramic materials, glass materials, and ceramic composite materials.
  • the conductive polymer material is, for example, selected from polysulfur nitride polymer materials or doped conjugated polymer materials, such as at least one of polypyrrole, polyacetylene, polyaniline, and polythiophene.
  • the conductive polymer composite material is, for example, selected from composite materials formed by insulating polymer materials and conductive materials, where the conductive material is selected from at least one of conductive carbon materials, metal materials, and composite conductive materials, and the conductive carbon materials are selected from carbon black, At least one of carbon nanotubes, graphite, acetylene black, and graphene, the metal material is selected from at least one of nickel, iron, copper, aluminum or alloys of the foregoing metals, and the composite conductive material is selected from nickel-coated graphite powder , At least one of nickel-coated carbon fibers.
  • the material of the support layer in this application is preferably an insulating polymer material or an insulating polymer composite material, especially when the current collector is a positive electrode current collector.
  • the safety performance of the battery can be significantly improved by using a composite current collector supported by an insulating layer and a conductive layer with a specific thickness.
  • the insulating layer is non-conductive, its resistance is relatively large, which can increase the short-circuit resistance of the battery when a short circuit occurs under abnormal conditions, and greatly reduce the short-circuit current. Therefore, it can greatly reduce the short-circuit heat generation and improve the safety performance of the battery;
  • the conductive layer is relatively thin. Therefore, under abnormal circumstances such as nail penetration, the local conductive network is cut off, preventing a large area of the electrochemical device or even the entire electrochemical device from short-circuiting, which can reduce the damage of the electrochemical device caused by nail penetration. The damage is limited to the puncture site, only forming a "point disconnection", and does not affect the normal operation of the electrochemical device within a certain period of time.
  • the thickness of the support layer is D1, and D1 preferably satisfies: 1 ⁇ m ⁇ D1 ⁇ 20 ⁇ m; more preferably 1 ⁇ m ⁇ D1 ⁇ 15 ⁇ m.
  • the mechanical strength of the support layer can be adapted to the pole piece processing technology, and the volume energy density of the battery of the current collector is improved.
  • the upper limit of the thickness D1 of the support layer can be 20 ⁇ m, 15 ⁇ m, 12 ⁇ m, 10 ⁇ m, 8 ⁇ m, and the lower limit can be 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m; the range of the thickness D1 of the support layer can be upper limit Or any numerical composition of the lower limit.
  • the specific thickness of the present application can further ensure that the current collector has a larger resistance, and significantly reduce the battery heating when an internal short circuit occurs.
  • the conductive layer is aluminum, it can also significantly reduce or prevent the aluminum heat of the positive electrode current collector. Response to ensure that the battery has good safety performance.
  • the conductive layer is a metal conductive layer
  • the normal temperature Young's modulus of the support layer satisfies: 20GPa ⁇ E ⁇ 1.9GPa.
  • 20GPa ⁇ E ⁇ 4GPa Preferably, 20GPa ⁇ E ⁇ 4GPa.
  • the testing method of the normal temperature Young's modulus of the support layer described in this application is as follows:
  • metal is relatively rigid relative to polymers or polymer composites, that is, it deforms less during the rolling process of pole piece processing, so in order to ensure that the deformation difference between the support layer and the conductive layer is not too large, so
  • the conductive layer is torn, and the normal temperature Young's modulus of the support layer should preferably satisfy: 20GPa ⁇ E ⁇ 1.9Gpa, so that the support layer can have certain rigidity, and the rigidity between the support layer and the conductive layer can be further improved Matching, so as to ensure that the deformation of the support layer and the conductive layer will not be too different during the processing of the current collector and the electrode pole piece.
  • the current collector Since the support layer has a certain rigidity (20GPa ⁇ E ⁇ 1.9GPa), the current collector is not easy to deform or stretch too much during the processing of the current collector and electrode pads, so that the support layer and the conductive layer can be combined It is firm, not easy to detach, and can prevent the conductive layer from being "forced" to stretch and cause damage to the conductive layer.
  • the current collector according to the present application has a certain degree of toughness, so that the current collector and the electrode pole pieces have a certain ability to withstand deformation and are not easy to break.
  • the Young's modulus of the support layer should not be too large, otherwise the rigidity will be too strong, which will cause difficulty in winding and winding, and poor workability.
  • the support layer can be guaranteed to have a certain flexibility, and the electrode pads can also have a certain ability to withstand deformation.
  • the thermal shrinkage rate of the support layer at 90° C. is not greater than 1.5%, so that the thermal stability of the current collector can be better ensured during the pole piece processing.
  • the current collector is further provided with a protective layer, and the protective layer is provided on one surface of the conductive layer of the current collector or on two of the conductive layers of the current collector. On the surface, that is, on the surface of the conductive layer away from the support layer and on the surface facing the support layer.
  • the protective layer can be a metal protective layer or a metal oxide protective layer.
  • the protective layer can prevent the conductive layer of the current collector from being damaged by chemical corrosion or mechanical damage, and can also enhance the mechanical strength of the current collector, thereby improving the current flow capacity of the current collector and the pole piece.
  • the protective layer is provided on both surfaces of the conductive layer of the current collector.
  • the lower protective layer of the conductive layer that is, the protective layer provided on the surface of the conductive layer facing the support layer
  • the technical effect of the upper protective layer of the conductive layer is mainly to prevent the conductive layer from being damaged and corroded during processing (such as electrolyte immersion, rolling, etc.)
  • the surface of the conductive layer affects).
  • the conductive primer layer is used in the electrode pole piece of the present application to repair the cracks that may occur in the conductive layer during rolling, winding, etc., to enhance the conductivity, and to make up for the shortcomings of the composite current collector as a current collector, the conductive layer
  • the upper protective layer can cooperate with the conductive bottom coating to further provide protection for the conductive layer, thereby jointly improving the conductive effect of the composite current collector as a current collector.
  • the metal protective layer can not only further improve the mechanical strength and corrosion resistance of the conductive layer, but also reduce the polarization of the pole piece.
  • the material of the metal protective layer is, for example, selected from at least one of nickel, chromium, nickel-based alloys, and copper-based alloys, preferably nickel or nickel-based alloys.
  • the nickel-based alloy is an alloy formed by adding one or more other elements to pure nickel as the matrix.
  • it is a nickel-chromium alloy.
  • the nickel-chromium alloy is an alloy formed of metallic nickel and metallic chromium.
  • the molar ratio of nickel element to chromium element is 1:99-99:1.
  • Copper-based alloy is an alloy formed by adding one or more other elements to pure copper as the matrix. Preferably, it is a copper-nickel alloy. Optionally, in the copper-nickel alloy, the molar ratio of nickel to copper is 1:99-99:1.
  • metal oxide When metal oxide is selected for the protective layer, due to its low ductility, large specific surface area, and high hardness, it can also form effective support and protection for the conductive layer, and improve the bonding force between the support layer and the conductive layer. Has a good technical effect.
  • the material of the metal oxide protective layer is, for example, at least one selected from aluminum oxide, cobalt oxide, chromium oxide, and nickel oxide.
  • the protective layer of the composite current collector according to the present application When used as a positive electrode current collector, the protective layer of the composite current collector according to the present application preferably adopts metal oxides to achieve good support and protection technical effects while further improving the safety performance of the positive electrode pole pieces and the battery; In the case of a negative electrode current collector, the protective layer of the composite current collector according to the present application preferably adopts metal to achieve good support and protection technical effects while further improving the conductivity of the pole pieces and the dynamic performance of the battery to reduce Battery polarization; when used as a negative electrode current collector, the protective layer of the composite current collector according to the present application is more preferably a double-layer protective layer comprising a metal protective layer and a metal oxide protective layer, preferably a metal protective layer is provided on the surface of the conductive layer , And a metal oxide protective layer is arranged on the surface of the metal protective layer.
  • the double-layer protective layer can better improve the conductivity, corrosion resistance and mechanical damage of the negative electrode current collector.
  • the thickness of the protective layer is D3, and D3 preferably satisfies: D3 ⁇ 1/10 ⁇ D2 and 1nm ⁇ D3 ⁇ 200nm. If the protective layer is too thin, it will not be enough to protect the conductive layer; if the protective layer is too thick, it will reduce the weight energy density and volume energy density of the battery. More preferably, 5nm ⁇ D3 ⁇ 500nm, further preferably 10nm ⁇ D3 ⁇ 200nm, most preferably 10nm ⁇ D3 ⁇ 50nm.
  • the materials of the protective layers on the two surfaces of the conductive layer can be the same or different, and the thickness can be the same or different.
  • the thickness of the lower protective layer is smaller than the thickness of the upper protective layer to help improve the weight energy density of the battery.
  • the ratio of the thickness D3" of the lower protective layer to the thickness D3' of the upper protective layer is: 1/2 ⁇ D3' ⁇ D3" ⁇ 4/5 ⁇ D3'.
  • the current collector is the positive electrode current collector
  • aluminum is usually used as the material of the conductive layer
  • the lower protective layer is preferably a metal oxide material.
  • the metal oxide material has a larger resistance. Therefore, this type of lower protective layer can further increase the resistance of the positive electrode current collector to a certain extent, thereby further improving the abnormality of the battery.
  • the short circuit resistance in the event of a short circuit improves the safety performance of the battery.
  • the specific surface area of the metal oxide is larger, the bonding force between the lower protective layer of the metal oxide material and the support layer is enhanced; at the same time, because the specific surface area of the metal oxide is larger, the lower protective layer can increase the support layer
  • the roughness of the surface plays a role in enhancing the bonding force between the conductive layer and the supporting layer, thereby improving the overall strength of the current collector.
  • the current collector is the negative electrode current collector
  • copper is usually used as the material of the conductive layer
  • the protective layer is preferably a metal material. More preferably, on the basis of including at least one metal protective layer, at least one of the lower protective layer and the lower protective layer further includes a metal oxide protective layer, in order to simultaneously improve the conductivity and interface bonding force of the negative electrode composite current collector.
  • FIGS 1 to 8 show schematic structural diagrams of current collectors used in electrode pads according to certain embodiments of the present application.
  • the positive current collector 10 includes a positive current collector support layer 101 and a positive current collector conductive layer 102 disposed on two opposite surfaces of the positive current collector support layer 101, and also includes a positive current collector conductive layer 102
  • the positive current collector protective layer 103 on the lower surface is the lower protective layer.
  • the positive electrode current collector 10 includes a positive electrode current collector support layer 101 and a positive electrode current collector conductive layer 102 provided on two opposite surfaces of the positive electrode current collector support layer 101, and also includes a positive electrode current collector conductive layer 102 The positive current collector protective layer 103 on the opposite two surfaces, namely the lower protective layer and the upper protective layer.
  • the positive current collector 10 includes a positive current collector support layer 101 and a positive current collector conductive layer 102 disposed on one surface of the positive current collector support layer 101, and also includes a positive current collector disposed on the positive current collector conductive layer 102.
  • the positive current collector protective layer 103 on the surface of the fluid supporting layer 101 is the lower protective layer.
  • the positive electrode current collector current collector 10 includes a positive electrode current collector support layer 101 and a positive electrode current collector conductive layer 102 arranged on one surface of the positive electrode current collector support layer 101, and also includes an opposite electrode arranged on the positive electrode current collector conductive layer 102.
  • the positive current collector protective layer 103 on both surfaces, namely the lower protective layer and the upper protective layer.
  • the negative current collector 20 includes a negative current collector support layer 201 and a negative current collector conductive layer 202 disposed on two opposite surfaces of the negative current collector support layer 201, and also includes a negative current collector conductive layer 202 disposed on the negative current collector conductive layer 202.
  • the negative current collector protective layer 203 on the surface facing the negative current collector support layer 201 is the lower protective layer.
  • the negative current collector 20 includes a negative current collector support layer 201 and a negative current collector conductive layer 202 disposed on two opposite surfaces of the negative current collector support layer 201, and also includes a negative current collector conductive layer 202.
  • the negative current collector protective layer 203 on the opposite two surfaces, namely the lower protective layer and the upper protective layer.
  • the negative current collector 20 includes a negative current collector support layer 201 and a negative current collector conductive layer 202 disposed on one surface of the negative current collector support layer 201, and also includes a negative current collector disposed on the negative current collector conductive layer 202.
  • the negative current collector protective layer 203 in the direction of the fluid supporting layer 201 is the lower protective layer.
  • the negative current collector 20 includes a negative current collector support layer 201 and a negative current collector conductive layer 202 disposed on one surface of the negative current collector support layer 201, and also includes two oppositely disposed negative current collector conductive layers 202.
  • the negative current collector protective layer 203 on the surface, namely the lower protective layer and the upper protective layer.
  • the material of the protective layer on the two opposite surfaces of the conductive layer can be the same or different, and the thickness can be the same or different.
  • a conductive layer may be provided on two opposite surfaces of the support layer, Alternatively, as shown in FIGS. 3, 4, 7, and 8, a conductive layer may be provided on only one side of the support layer. (Although the figure shows the case where only the lower protective layer is included, it is understandable that only the upper protective layer may be included)
  • the composite current collector used in the electrode pads of the present application preferably contains a current collector protective layer as shown in FIGS. 1 to 8, it should be understood that the current collector protective layer is not a necessary structure of the current collector. In some embodiments, The current collector used in may not contain a current collector protective layer.
  • the electrode active material layer of the electrode pad is provided on the main part of one or both surfaces of the composite current collector (in this application, this part is called the diaphragm area of the current collector).
  • a conductive primer layer (discussed later) is provided between the composite current collector and the electrode active material layer.
  • the electrode active material layer used in the electrode pad of the present application generally includes an electrode active material, a binder, and a conductive agent. According to needs, the electrode active material layer may further include optional other additives or auxiliary agents.
  • the positive electrode active material can be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, transition Metal phosphate, lithium iron phosphate, etc., but the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials of lithium ion batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more kinds.
  • the positive electrode active material may be selected from LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM 333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM 523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 , LiMnPO 4 or one of Several kinds.
  • the negative electrode active material can be selected from carbonaceous materials such as graphite (artificial graphite or natural graphite), conductive carbon black, carbon fiber, etc., such as metals or semi-metals such as Si, Sn, Ge, Bi, Sn, and In. Metal material or its alloy, lithium-containing nitride or lithium-containing oxide, lithium metal or lithium aluminum alloy, etc.
  • the average particle diameter D50 of the active material in the electrode active material layer is 5-15 ⁇ m. If the D50 is too small, the porosity of the pole piece after compaction is small, which is not conducive to the infiltration of the electrolyte, and its larger specific surface area is likely to cause more side reactions with the electrolyte, reducing the reliability of the battery; if D50 If it is too large, it is easy to cause greater damage to the conductive primer layer and the composite current collector during the pole piece compaction process. D50 refers to the particle size when the cumulative volume percentage of the active material reaches 50%, that is, the median particle size of the volume distribution. D50 can be measured using, for example, a laser diffraction particle size distribution measuring instrument (such as Malvern Mastersizer 3000).
  • the conductive agent in the electrode active material layer can be at least one of conductive carbon material and metal material; wherein, the conductive carbon material is selected from zero-dimensional conductive carbon, such as acetylene black, conductive carbon black; one-dimensional conductive carbon, such as carbon nano Tube; two-dimensional conductive carbon, such as conductive graphite, graphene; three-dimensional conductive carbon, such as at least one of reduced graphene oxide; metal material selected from at least one of aluminum powder, iron powder and silver powder.
  • the conductive carbon material is selected from zero-dimensional conductive carbon, such as acetylene black, conductive carbon black; one-dimensional conductive carbon, such as carbon nano Tube; two-dimensional conductive carbon, such as conductive graphite, graphene; three-dimensional conductive carbon, such as at least one of reduced graphene oxide; metal material selected from at least one of aluminum powder, iron powder and silver powder.
  • the binder in the electrode active material layer can be selected from styrene butadiene rubber, oily polyvinylidene fluoride (PVDF), polyvinylidene fluoride copolymer (such as PVDF-HFP copolymer, PVDF-TFE copolymer), carboxymethyl fiber Sodium, polystyrene, polyacrylic acid, polytetrafluoroethylene, polyacrylonitrile, polyimide, water-based PVDF, polyurethane, polyvinyl alcohol, polyacrylate, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate- At least one of polyacrylonitrile copolymers.
  • PVDF oily polyvinylidene fluoride
  • PVDF-HFP copolymer such as PVDF-HFP copolymer, PVDF-TFE copolymer
  • carboxymethyl fiber Sodium carboxymethyl fiber Sodium
  • PVDF oily polyvinylidene fluoride
  • a slurry composed of electrode active materials, conductive agents, and binders is coated on the electrode current collector (or pre-coated on the primer layer of the electrode current collector), and then dried and other post-processing Then the desired electrode active material layer can be obtained.
  • Electrodes can be coated with one or more electrode active material layers, but regardless of single-layer coating or multi-layer coating, the electrode active material layer is generally uniformly coated in the coating area of the entire pole piece surface.
  • the cold pressing (rolling) operation is also performed on the surface of the pole piece as a whole, and the compaction density of the electrode active material layer on the pole piece thus obtained is basically the same without significant difference.
  • the electrode active material layer includes three regions based on the compaction density, and the compaction density of the middle region is higher than the compaction density of the regions on both sides.
  • the compaction density on both sides of the pole piece is low, while the compaction density in the middle area is high, that is, the area on both sides of the pole piece is subjected to cold pressing (rolling).
  • the pressure is less than the middle area, which can avoid the edge warpage and curvature of the composite current collector and the electrode pole piece caused by the rebound of the composite current collector during the pole piece processing, which is beneficial to the formation of a smooth surface pole piece, thereby It helps to ensure the electrochemical performance of the electrochemical device. And it is beneficial to protect the conductive layer from being easily damaged, thereby ensuring good overcurrent capability of the electrode pole pieces.
  • the "length direction” and “width direction” of the surface of the electrode pole piece refer to the two dimensions of the surface respectively, where the length direction refers to the main dimension direction (that is, the direction with larger dimensions), and the width direction refers to The secondary dimension direction (that is, the direction of the smaller size).
  • the length direction is consistent with the coating direction of each material layer (such as electrode active material layer) during the processing of the pole piece, and is also consistent with the winding direction of the pole piece during the manufacturing process of an electrochemical device (such as a battery) ;
  • the width direction is perpendicular to the length direction.
  • the 2n+1 regions of the active material layer based on the compaction density according to the present application, it can be realized by a partition coating method, that is, using baffles or spacers to divide different regions (or boundaries) on the surface of the pole piece , Each area is coated with different weight of electrode active material slurry, so that the active material layer area with different compaction density is formed after rolling.
  • the compaction density of the areas on both sides is preferably the same. Such a design is beneficial to better ensure the flatness of the electrode pads.
  • the binder content in the electrode active material layer is preferably not less than 1wt%, more preferably not less than 1.5wt%, most preferably Not less than 2wt%.
  • the binder content in the electrode active material layer is preferably not less than 1wt%, more preferably not less than 1.5wt%, most preferably Not less than 2wt%.
  • the binding force between the two is insufficient, the internal resistance of the battery is larger, the polarization is increased, and the electrochemical performance is poor.
  • the high binding force enables the active material layer to effectively wrap the metal burrs generated in the conductive layer under abnormal circumstances such as nail penetration, so as to improve the safety performance of the battery. If the binder content is kept within this range, the active material layer and the current collector have a better binding force, so that under abnormal conditions such as nail penetration, the active material layer can more effectively wrap the metal burrs generated in the conductive layer , In order to improve the safety performance of battery nail penetration.
  • 9 to 16 show schematic cross-sectional structure diagrams of the diaphragm area of the electrode pad according to some embodiments of the present application.
  • the positive electrode sheet includes a positive electrode current collector 10 and a positive electrode active material layer 11 disposed on two opposite surfaces of the positive electrode current collector 10 in the diaphragm area
  • the positive electrode current collector 10 includes a positive electrode current collector support layer 101 and The positive electrode current collector conductive layer 102 provided on two opposite surfaces of the positive electrode current collector support layer 101 and the positive electrode protective layer 103 (not shown in the figure) provided on one or both sides of the positive electrode conductive layer 102.
  • the positive electrode sheet includes a positive electrode current collector 10 and a positive electrode active material layer 11 provided on one surface of the positive electrode current collector 10 in the diaphragm area
  • the positive electrode current collector 10 includes a positive electrode current collector support layer 101 and a positive electrode
  • the positive pole piece PP includes a positive electrode current collector 10, a conductive undercoat layer 12 and a positive electrode active material layer 11 disposed on two opposite surfaces of the positive electrode current collector 10 in the diaphragm area, and the positive electrode current collector 10 includes The positive electrode current collector support layer 101 and the positive electrode current collector conductive layer 102 provided on two opposite surfaces of the positive electrode current collector support layer 101.
  • the positive electrode sheet PP includes a positive electrode current collector 10, a conductive undercoat layer 12 and a positive electrode active material layer 11 disposed on one surface of the positive electrode current collector 10 in the diaphragm area, and the positive electrode current collector 10 includes a positive electrode current collector.
  • the negative electrode sheet includes a negative electrode current collector 20 and a negative electrode active material layer 21 disposed on two opposite surfaces of the negative electrode current collector 20 in the diaphragm area
  • the negative electrode current collector 20 includes a negative electrode current collector support layer 201 and The negative electrode current collector conductive layer 202 disposed on two opposite surfaces of the negative electrode current collector support layer 201 and the negative electrode protective layer 203 (not shown in the figure) disposed on one or both sides of the negative electrode conductive layer 202.
  • the negative electrode sheet includes a negative electrode current collector 20 and a negative electrode active material layer 21 arranged on one surface of the negative electrode current collector 20 in the diaphragm area, and the negative electrode current collector 20 includes a negative electrode current collector support layer 201 and a negative electrode active material layer 21 arranged on the negative electrode.
  • the negative electrode piece NP includes a negative electrode current collector 20 and a conductive undercoat layer 22 and a negative electrode active material layer 21 disposed on two opposite surfaces of the negative electrode current collector 20 in the diaphragm area, and the negative electrode current collector 20 includes The negative electrode current collector support layer 201 and the negative electrode current collector conductive layer 202 disposed on two opposite surfaces of the negative electrode current collector support layer 201.
  • the negative electrode piece NP includes a negative electrode current collector 20 and a conductive undercoat layer 22 and a negative electrode active material layer 21 disposed on one surface of the negative electrode current collector 20 in the diaphragm area, and the negative electrode current collector 20 includes a negative electrode current collector.
  • the electrode active material layer may be provided on one surface of the current collector, or may be provided on both surfaces of the current collector.
  • the electrode pads can be coated on both sides (that is, the electrode active material layer is provided on both surfaces of the current collector), or only on one side. Coating (that is, the electrode active material layer is only provided on one surface of the current collector); and when the current collector provided with only a single-sided conductive layer is used, the electrode pads can only be coated on one side, and the electrode active material layer (And the conductive primer layer) can only be coated on the side of the current collector provided with the conductive layer.
  • the surface of the composite current collector can be divided into three areas according to the coating material and position: the diaphragm area located in the main body portion for setting the electrode active material layer, and the edge portion used for welding the electrical connection member ( Also known as the pole ear) the transfer welding area and the extension area as the transition area between the two.
  • a conductive primer layer may be provided on the composite current collector.
  • the conductive primer layer is not only provided between the conductive layer of the current collector diaphragm area and the electrode active material layer (also called the diaphragm layer), but also provided on the extension area of the current collector.
  • the surface of the conductive layer The surface of the conductive layer of the current collector at the transfer welding area (usually under the welding mark) can be provided or not provided with a conductive primer layer according to the situation (for ease of operation, such as welding the tabs and then setting the material layer, The conductive primer layer may not be provided. On the contrary, if the material layer is provided first and then the tabs are welded, the conductive primer layer may be provided, or the conductive primer layer may not be provided).
  • the distribution layout of the conductive primer layer on the surface of the diaphragm area and the extension area of the composite current collector can have various designs, which will be described in detail with reference to FIGS. 17A, 17B, 17C and 17D.
  • FIG. 17A schematically shows a top view of a positive pole piece according to a specific embodiment of the present application.
  • the positive pole piece includes a composite current collector 10 and a plurality of electrical connection members (tabs) 511 electrically connected to the current collector 10 at the edges by welding.
  • the current collector 10 is provided with a conductive primer layer and an active material layer in the diaphragm area A of its main body; the area where the current collector 10 and the tab 511 are welded and overlapped is the transfer welding area C; and the diaphragm area A and The transition area outside the transfer welding area C is the extension area B, and the surface of the extension area B is also provided with a conductive primer layer.
  • FIG. 17B schematically shows a top view of a positive pole piece according to another specific embodiment of the present application.
  • the positive pole piece includes a composite current collector 10 and a plurality of electrical connection members (tabs) 511 electrically connected to the current collector 10 by welding at several edge protrusions.
  • the current collector 10 is provided with a conductive primer layer and an active material layer in a diaphragm area A located in its main body part (the entire main body part is referred to as the diaphragm area A).
  • Several protrusions of the current collector 10 serve as the extension area B, and a conductive primer coating is provided on the surface of the extension area B.
  • the area where the tab 511 overlaps the extension area B is the transfer welding area C.
  • FIG. 17C schematically shows a top view of a positive pole piece according to another specific embodiment of the present application.
  • the positive pole piece includes a composite current collector 10 and a plurality of electrical connection members (tabs) 511 electrically connected to the current collector 10 by welding at several edge protrusions.
  • Most areas of the main body of the current collector 10 are used as the diaphragm area A, but a stripe-shaped area is left at the edge as the extension area B together with several protrusions; the diaphragm area A is provided with a conductive primer layer and an active material layer , And only a conductive primer layer is provided in the extension B.
  • the area where the tab 511 overlaps the extension area B is the transfer welding area C.
  • FIG. 17D schematically shows a top view of a positive pole piece according to another specific embodiment of the present application.
  • the positive pole piece includes a composite current collector 10 and a belt-shaped electrical connection member 511 electrically connected to the current collector 10 at the edge by welding.
  • the current collector 10 is provided with a conductive primer layer and an active material layer in the diaphragm area A of its main body; the area where the current collector 10 and the electrical connection member 511 are welded and overlapped together is the transfer welding area C; and the diaphragm area A
  • the transition area with the transfer welding area C is the extension area B, and the surface of the extension area B is also provided with a conductive primer coating.
  • FIG. 17E schematically shows a cross-sectional structure diagram of the positive pole piece of some specific embodiments shown in FIGS. 17A to 17D (for example, the X-X cross-sectional view of 17C).
  • the positive pole piece PP includes a composite current collector 10 and an electrical connection member 511 electrically connected to the current collector 10 by welding.
  • the positive electrode current collector 10 includes a positive electrode current collector support layer 101, a positive electrode current collector conductive layer 102 disposed on one surface of the positive electrode current collector support layer 101, and a positive electrode protective layer 103 disposed on one or both sides of the positive electrode conductive layer 102 ( Figure Not shown in).
  • the positive electrode current collector 10 can be divided into three areas according to the different material layers provided on its surface: diaphragm area A, extension area B and transfer welding area C; diaphragm area A occupies the positive electrode current collector The main part of the surface of 10, on which the conductive primer layer 12 and the positive electrode active material layer 11 are sequentially formed, the transfer welding area C provides the electrical connection interface between the positive electrode current collector 10 and the electrical connection member 511, and the extension area B A conductive primer layer 12 is also provided on the surface (but no positive electrode active material layer 11 is provided).
  • FIGS. 17A to 17E show schematic structural diagrams of a positive pole piece using a single-sided composite current collector with a conductive layer.
  • the pole piece of the present application can also adopt a double-sided composite current collector with two conductive layers.
  • the conductive primer layer and the positive electrode active material layer are also provided on both surfaces of the composite current collector.
  • the negative pole piece can also be similarly designed.
  • the conductive primer layer can improve the interface of the composite current collector, and can well overcome the disadvantages of poor conductivity of the composite current collector and easy damage of the conductive layer in the composite current collector.
  • By effectively repairing the surface of the current collector It also builds a conductive network between the current collector, the conductive primer layer and the active material, improves the efficiency of electron transmission, reduces the resistance of the current collector and the electrode active material layer, which can effectively reduce the DC internal resistance of the cell, improve the power performance of the cell, and ensure
  • the battery cell is not prone to large polarization and lithium evolution during the long-term cycle, which effectively improves the long-term reliability of the battery cell; in addition, it can also improve the adhesion between the current collector and the active material to ensure
  • the electrode active material layer is more firmly arranged on the surface of the composite current collector; in addition, a conductive primer layer is provided on the diaphragm area and the extension area of the composite current collector, which can improve the flow capacity and electrochemical performance of the electrode pole piece, By improving the
  • the conductive primer layer includes a conductive material and a binder. Based on the total weight of the conductive primer layer, the weight percentage of the conductive material is 10% to 99%, preferably 20% to 80%, more preferably 50% to 80%; the weight percentage of the binder The content is 1% to 90%, preferably 20% to 80%, more preferably 20% to 50%. This ratio can help improve the conductivity of the electrode pads and the binding force between the current collector and the electrode active material layer. In addition to conductive materials and binders, the conductive primer layer may also contain optional other additives or auxiliary agents.
  • the conductive material is at least one of a conductive carbon material and a metal material; the conductive material in the conductive primer layer and the conductive agent in the active material layer may be the same or different.
  • the conductive carbon material is selected from zero-dimensional conductive carbon (such as acetylene black, conductive carbon black), 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 preferred conductive material contains one-dimensional conductive carbon material or two-dimensional conductive carbon material. Because after adding the two-dimensional conductive carbon material, during the compaction of the pole piece, the two-dimensional conductive carbon material in the conductive undercoat can produce "horizontal sliding", which acts as a buffer and reduces the impact on the current collector during the compaction process. Destruction of the conductive layer, thereby reducing cracks.
  • the particle size D50 of the preferred two-dimensional conductive carbon material is 0.01 to 0.1 ⁇ m.
  • the two-dimensional conductive carbon material accounts for 1 wt% to 50 wt% of the conductive material.
  • the one-dimensional conductive carbon material due to the special morphology of the one-dimensional conductive carbon material, it can improve the conductivity of the conductive undercoat after adding, especially when the amount of conductive material added is certain, the one-dimensional conductive carbon material is compared with other types of conductive materials.
  • the material can better improve the conductivity of the conductive primer.
  • carbon nanotubes Preferably, carbon nanotubes have an aspect ratio of 1,000 to 5,000.
  • the preferred conductive material is a mixed material of a zero-dimensional conductive carbon material and a one-dimensional conductive carbon material or a mixed material of a zero-dimensional conductive carbon material and a two-dimensional conductive carbon material.
  • the binder in the conductive primer layer and the binder in the active material layer may be the same or different.
  • the binder in the conductive primer layer is selected from styrene butadiene rubber, oily polyvinylidene fluoride (PVDF), polyvinylidene fluoride copolymer (such as PVDF-HFP copolymer, PVDF-TFE copolymer), carboxymethyl cellulose Sodium, polystyrene, polyacrylic acid, polytetrafluoroethylene, polyacrylonitrile, polyimide, water-based PVDF, polyurethane, polyvinyl alcohol, polyacrylate, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-poly At least one of acrylonitrile copolymers.
  • PVDF oily polyvinylidene fluoride
  • PVDF-HFP copolymer such as PVDF-HFP copolymer, PVDF-TFE copolymer
  • carboxymethyl cellulose Sodium carboxymethyl cellulose Sodium
  • PVDF oily polyvinylidene fluoride
  • the binder in the conductive primer layer is preferably an aqueous binder, such as aqueous PVDF, polyacrylic acid, polyurethane, polyvinyl alcohol, polyacrylate, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer At least one of them, so that the DCR growth of the electrochemical device is small.
  • aqueous PVDF aqueous binder
  • aqueous polymer material means that the polymer molecular chain is fully extended and dispersed in water
  • “oily” polymer material means that the polymer molecular chain is fully extended and dispersed in an oily solvent.
  • a suitable surfactant the same type of polymer material can be dispersed in water and oil respectively, that is, by using a suitable surfactant, the same type of polymer material can be made into water-based Polymer materials and oily polymer materials.
  • those skilled in the art can modify PVDF into aqueous PVDF or oily PVDF as needed.
  • the thickness H of one side of the conductive primer layer is preferably 0.1 ⁇ m to 5 ⁇ m.
  • H/D2 is 0.5:1 to 5:1. If the ratio is too small, it cannot effectively improve the cracks of the conductive layer and improve the conductivity of the pole piece; if the ratio is too large, it will not only reduce the weight and energy density of the battery, but also increase the battery DCR, which is not conducive to the dynamic performance of the battery. Improvement.
  • the material composition of the conductive primer layer of the current collector diaphragm region and the conductive primer layer of the current collector extension region may be the same or different, and the thickness may be the same or different.
  • the thickness of the conductive primer layer in the extended region of the composite current collector is greater than the thickness of the conductive primer layer in the diaphragm region, or the conductive material in the conductive primer layer in the extended region of the composite current collector
  • the content of is higher than the content of conductive material in the conductive primer layer of the diaphragm area.
  • the conductive layer of the current collector in the extension area is thinner than the traditional metal current collector. Therefore, in order to prevent damage, such as damage to the conductive layer, breakage, etc., in a preferred embodiment, the conductive layer of the composite current collector
  • the surface of the conductive primer coating of the extension area is also provided with a supporting protective layer, which can improve the mechanical strength and hardness at the extension area of the composite current collector, prevent bending and deformation of the extension area of the current collector, and prevent the conductive layer at the extension area Damage occurs, which can improve the overcurrent capability there.
  • the supporting protection layer is an organic insulating layer or an inorganic insulating layer.
  • the organic insulating layer can be selected from an insulating tape layer or an insulating glue coating.
  • the insulating rubber coating is selected from, for example, a polyvinylidene fluoride layer, a polyvinylidene fluoride layer, a vinylidene fluoride-hexafluoropropylene copolymer layer, a styrene butadiene rubber layer, a sodium carboxymethyl cellulose layer, and a polyacrylic acid layer. , At least one of sodium polyacrylate layer, polyethylene oxide layer, and polyvinyl alcohol layer.
  • the inorganic insulating layer can be selected from aluminum oxide layer, magnesium oxide layer, zinc oxide layer, silicon oxide layer, titanium oxide layer, zirconium oxide layer, aluminum nitride layer, silicon nitride layer, calcium fluoride layer, barium fluoride layer At least one of.
  • the inorganic insulating layer may include insulating fillers and binders, among which preferred insulating fillers are aluminum oxide, magnesium oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, aluminum nitride, silicon nitride, calcium fluoride, At least one of the barium fluoride, the preferred binder is polyvinylidene fluoride, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene butadiene rubber, sodium carboxymethyl cellulose, At least one of polyacrylic acid, polyethylene oxide, and polyvinyl alcohol.
  • preferred insulating fillers are aluminum oxide, magnesium oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, aluminum nitride, silicon nitride, calcium fluoride, At least one of the barium fluoride, the preferred binder is polyvinylidene fluoride, polyvinylidene fluoride, vinyliden
  • the percentage of the insulating filler in the inorganic insulating layer is generally greater than or equal to 50wt% to ensure that the layer has a certain degree of hardness and mechanical strength.
  • the percentage of the binder is generally less than 50wt%, preferably 0.1wt%-20wt %.
  • FIG. 18 schematically shows a cross-sectional view of a positive pole piece provided with a supporting protective layer on the surface of the conductive undercoat layer of the extension area according to a specific embodiment of the present application.
  • the positive pole piece PP includes a composite current collector 10 and an electrical connection member 511 electrically connected to the current collector 10 by welding.
  • the positive electrode current collector 10 includes a positive electrode current collector support layer 101, a positive electrode current collector conductive layer 102 disposed on one surface of the positive electrode current collector support layer 101, and a positive electrode protective layer 103 disposed on one or both sides of the positive electrode conductive layer 102 ( Figure Not shown in).
  • the positive electrode current collector 10 can be divided into three areas according to the different material layers provided on its surface: the diaphragm area A, the extension area B and the transfer welding area C; the diaphragm area A occupies the main part of the surface of the positive electrode current collector 10.
  • a conductive primer layer 12 and a positive electrode active material layer 11 are sequentially formed on the upper surface.
  • the transfer welding area C provides the electrical connection interface between the positive electrode current collector 10 and the electrical connection member 511, and the extension area B is provided with a conductive primer layer on the surface Layer 12 and supporting protective layer 15.
  • Fig. 18 illustrates the supporting and protective layer by taking a single-sided composite current collector as an example, but those skilled in the art understand that the supporting and protective layer can also be provided on both sides of the double-sided composite current collector. In addition, those skilled in the art can understand that the negative pole piece can also be similarly designed.
  • the electrode pads of the present application can be prepared by various methods commonly used in the art.
  • the composite current collector can be prepared first, and then the conductive undercoating slurry can be prepared, and the conductive undercoating slurry can be applied to a single or both surfaces of the composite current collector; after drying, the electrode active material layer slurry can be coated , Then dry; finally, after processing and welding the electrical connection components to obtain the required electrode pole piece.
  • the electrical connection member may be formed on the composite current collector before forming the conductive primer layer and the electrode active material layer.
  • This special partition design can effectively suppress the curvature and edge warping of the composite current collector and electrode pads due to rolling, etc.
  • the electrode pole piece maintains a good pole piece flatness after rolling, eliminates or reduces technical problems such as large internal resistance and large polarization of the pole piece, and is beneficial to protect the conductive layer from being damaged, thereby making the electrode
  • the sheet has good flow capacity and the electrochemical device has good electrochemical performance.
  • FIG. 19 shows a schematic top view of the structure of an electrode pad according to some embodiments of the present application.
  • the positive pole piece PP includes a pole piece body and one or more tabs 511 electrically connected to it; according to the difference in the electrode active material layer to be coated, the pole piece body includes four areas: directly connected to the tab 511
  • the ratio of the intermediate high-density area to the total coating area (in this example, the ratio of the sum of 514 width and 513 width + 514 width + 515 width) can be, for example, 20% to 80%, It is preferably 30% to 70%, preferably 40% to 60%, or more preferably 45% to 55%.
  • the widths of the two low-pressure solid areas may be the same or different, preferably the same.
  • the compaction density of the low-pressure compaction area may be about 5%-30% lower than the compaction density of the high-pressure compaction area, such as 7%-25%, such as 8%-20%, such as 8%-18%. %.
  • Figure 19 uses the positive pole piece as an example to illustrate the preferred partition coating method according to the present application.
  • the negative pole piece can also be coated in a similar manner to improve the flow capacity of the pole piece and maintain a better flatness of the pole piece. , Eliminate or reduce the technical problems such as large internal resistance of the pole piece and large polarization, and help protect the conductive layer from damage, so that the pole piece and electrochemical device have good electrochemical performance.
  • the second aspect of the present application provides an electrochemical device, including a positive pole piece, a negative pole piece, a separator and an electrolyte, wherein the positive pole piece and/or the negative pole piece are according to the first aspect of the present application Electrode pads.
  • the electrochemical device may be a capacitor, a primary battery, or a secondary battery.
  • it may be a lithium ion capacitor, a lithium ion primary battery, or a lithium ion secondary battery.
  • FIG. 20 shows a perspective view of an electrochemical device as a lithium ion secondary battery according to an embodiment of the present invention
  • FIG. 21 is an exploded view of the lithium ion secondary battery shown in FIG. 20.
  • the lithium ion secondary battery 5 (hereinafter referred to as the battery cell 5) according to the present application includes an outer package 51, an electrode assembly 52, a top cover assembly 53, and an electrolyte (not shown).
  • the electrode assembly 52 is contained in the outer package 51, and the number of the electrode assembly 52 is not limited, and can be one or more.
  • the battery cell 5 shown in FIG. 20 is a can type battery, but the application is not limited to this.
  • the battery cell 5 may be a pouch type battery, that is, the housing 51 is replaced by a metal plastic film and the top cover is eliminated. Component 53.
  • the structure and preparation method of these electrochemical devices are well known per se. Due to the use of the electrode pads of the present application, the electrochemical device can have improved safety (such as nail penetration safety) and electrical performance. In addition, the electrode pad of the present application is easy to process, so the manufacturing cost of an electrochemical device using the electrode pad of the present application can be reduced.
  • the specific types and compositions of the isolation membrane and the electrolyte are not specifically limited, and can be selected according to actual needs.
  • the isolation film can be selected from polyethylene film, polypropylene film, polyvinylidene fluoride film and their multilayer composite film.
  • a non-aqueous electrolyte is generally used as the electrolyte.
  • a lithium salt solution dissolved in an organic solvent is generally used as the non-aqueous electrolyte.
  • the lithium salt is, for example, LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 and other inorganic lithium salts, or LiCF 3 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiC n F 2n+1 SO 3 (n ⁇ 2) and other organic lithium salts.
  • the organic solvent used in the non-aqueous electrolyte is, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc.
  • Ether cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, nitriles such as acetonitrile and propionitrile, or a mixture of these solvents.
  • the lithium ion secondary battery can be assembled into a battery module, and the number of lithium ion secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 22 shows the battery module 4 as an example. Referring to FIG. 22, in the battery module 4, a plurality of lithium ion secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of lithium ion secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space, and a plurality of lithium ion secondary batteries 5 are accommodated in the accommodation space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • FIG. 23 and FIG. 24 show the battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the third aspect of the present application provides a device, including the electrochemical device described in the second aspect of the present application.
  • the electrochemical device can be used as a power source for the device or as an energy storage unit of the device.
  • the device includes, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a lithium ion secondary battery, battery module, or battery pack according to its usage requirements.
  • Fig. 25 shows a schematic diagram of a device according to a specific embodiment of the present application.
  • the device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device generally requires lightness and thinness, and a lithium ion secondary battery (ie, the electrochemical device of the present application) can be used as a power source.
  • a lithium ion secondary battery ie, the electrochemical device of the present application
  • the preparation methods of the current collectors used in the electrode pads in each embodiment and comparative example are as follows.
  • the formation conditions of the vacuum evaporation method are as follows: the support layer with the surface cleaning treatment is placed in the vacuum coating chamber, and the high-purity metal wire in the metal evaporation chamber is melted and evaporated at a high temperature of 1600°C to 2000°C. The evaporated metal After the cooling system in the vacuum coating chamber, it is finally deposited on the surface of the support layer to form a conductive layer.
  • the forming conditions of the mechanical rolling method are as follows: the foil of the conductive layer material is placed in a mechanical roller, and it is rolled to a predetermined thickness by applying a pressure of 20t to 40t, and then it is placed and subjected to surface cleaning treatment The surface of the support layer is finally placed in a mechanical roller, and the two are tightly combined by applying a pressure of 30t to 50t.
  • the formation conditions of the bonding method are as follows: the foil of the conductive layer material is placed in a mechanical roller, and it is rolled to a predetermined thickness by applying a pressure of 20t to 40t; and then the surface cleaning treatment of the support layer The surface is coated with a mixed solution of PVDF and NMP; finally, the conductive layer with the predetermined thickness is adhered to the surface of the support layer and dried at 100°C.
  • a protective layer is provided on the surface of the support layer by vapor deposition or coating, and then a conductive layer with a certain thickness is formed on the surface of the support layer with the protective layer by vacuum evaporation, mechanical rolling or bonding.
  • the protective layer is located between the support layer and the conductive layer
  • the surface of the conductive layer away from the support layer can be vapor-deposited in situ
  • the formation method or the coating method forms another protective layer to prepare a current collector with a protective layer (the protective layer is located on two opposite surfaces of the conductive layer).
  • a protective layer is formed on one surface of the conductive layer by vapor deposition, in-situ formation or coating, and then the conductive layer with the protective layer is placed on the support by mechanical rolling or bonding.
  • Layer surface, and the protective layer is arranged between the support layer and the conductive layer to prepare a current collector with a protective layer (the protective layer is located between the support layer and the conductive layer); in addition, on the basis of the above, the conductive layer
  • Another protective layer is formed on the surface away from the support layer by vapor deposition, in-situ formation or coating to prepare a current collector with a protective layer (the protective layer is located on two opposite surfaces of the conductive layer).
  • a protective layer is formed on one surface of the conductive layer by vapor deposition, in-situ formation or coating, and then the conductive layer with the protective layer is placed on the support by mechanical rolling or bonding.
  • the protective layer is arranged on the surface of the conductive layer away from the support layer to prepare a current collector with a protective layer (the protective layer is located on the surface of the conductive layer away from the support layer).
  • a protective layer is formed on the two surfaces of the conductive layer by vapor deposition, in-situ formation or coating, and then the conductive layer with the protective layer is placed on the conductive layer by mechanical rolling or bonding.
  • the surface of the support layer is used to prepare a current collector with a protective layer (the protective layer is located on two opposite surfaces of the conductive layer).
  • the vapor deposition method uses a vacuum evaporation method
  • the in-situ formation method uses an in-situ passivation method
  • the coating method uses a doctor blade coating method.
  • the formation conditions of the vacuum evaporation method are as follows: put the sample with surface cleaning treatment in the vacuum plating chamber, melt and evaporate the protective layer material in the evaporation chamber at a high temperature of 1600°C to 2000°C, and the evaporated protective layer material passes through the vacuum coating chamber The cooling system is finally deposited on the surface of the sample to form a protective layer.
  • the formation conditions of the in-situ passivation method are as follows: the conductive layer is placed in a high-temperature oxidizing environment, the temperature is controlled at 160°C to 250°C, while the oxygen supply is maintained in the high-temperature environment, and the treatment time is 30 minutes, thereby forming metal oxides.
  • the protective layer is controlled at 160°C to 250°C, while the oxygen supply is maintained in the high-temperature environment, and the treatment time is 30 minutes, thereby forming metal oxides.
  • the formation conditions of the gravure coating method are as follows: the protective layer material and NMP are stirred and mixed, and then the slurry of the protective layer material (solid content of 20% to 75%) is coated on the surface of the sample, and then the gravure roll is used to control the coating The thickness is finally dried at 100°C to 130°C.
  • NCM333 92wt% positive electrode active material
  • SP 5wt% conductive agent Super-P
  • 3wt% PVDF 3wt% PVDF
  • the current collector is an Al foil with a thickness of 12 ⁇ m, which is similar to the preparation method of the above positive electrode.
  • the positive electrode active material layer slurry is directly coated on the surface of the Al foil current collector, and then the conventional positive electrode is obtained by post-processing .
  • conductive materials such as conductive carbon black
  • binders such as PVDF or polyacrylic acid, etc.
  • active materials dissolve them in a suitable solvent (such as NMP or water), and mix well to form a primer Slurry.
  • the coating speed is 20m/min
  • the primer is dried, oven
  • the temperature is 70 ⁇ 100°C, and the drying time is 5min.
  • the positive electrode active material layer slurry is coated on the surface of the undercoat layer by extrusion coating; the positive electrode active material layer is obtained after drying at 85° C., and then the positive electrode sheet with the conductive undercoat layer is obtained by post-processing.
  • Press coating applies the positive electrode active material layer slurry to the main part of the surface of the primer layer (ie the membrane area), leaving a stripe-shaped blank on the surface of the primer layer near the edge, and then drying at 85°C After obtaining the positive electrode active material layer, a supporting protective layer is formed on the surface of the undercoating layer of the extension area as required, and then post-processing is performed to obtain a positive electrode sheet with a conductive undercoating layer on the surface of the film area and the extension area.
  • the negative active material artificial graphite, conductive agent Super-P, thickener CMC, and binder SBR was added to the solvent deionized water at a mass ratio of 96.5:1.0:1.0:1.5 to make the negative active material layer slurry;
  • the negative electrode active material layer slurry was partition-coated on both surfaces of the composite current collector prepared according to the above method; the negative electrode active material layer was obtained after drying at 85°C.
  • the current collector is a Cu foil with a thickness of 8 ⁇ m, similar to the preparation method of the negative electrode above, the negative electrode active material layer slurry is directly coated on the surface of the Cu foil current collector, and then the conventional negative electrode is obtained by post-processing .
  • conductive materials such as conductive carbon black
  • binders such as PVDF or polyacrylic acid, etc.
  • active materials dissolve them in a suitable solvent (such as NMP or water), and mix well to form a primer Slurry.
  • the coating speed is 20m/min
  • the primer is dried
  • the oven temperature is 70 ⁇ 100°C
  • the drying time is 5min.
  • the primer layer After the primer layer is completely dried, add the negative active material artificial graphite, conductive agent Super-P, thickener CMC, and binder SBR to the solvent deionized water at a mass ratio of 96.5:1.0:1.0:1.5 and mix uniformly.
  • the negative electrode active material layer slurry is formed; the negative electrode active material layer slurry is partitioned on the surface of the undercoat layer by extrusion coating; the negative electrode active material layer is obtained after drying at 85 °C, and then the conductive The negative pole piece of the base coat.
  • Negative pole piece with conductive undercoating in the diaphragm area Similar to the preparation method of "7) Negative pole piece with conductive undercoating in the diaphragm area", the difference is that the conductive member (nickel tape) is welded at the edge of the extension area before the undercoating slurry is applied. Then coat the primer slurry, and when coating the primer slurry, coat the primer slurry on the entire surface of the current collector (including the current collector surface in the diaphragm area and the current collector surface in the extension area). After the coating is completely dried, the negative active material, artificial graphite, conductive agent Super-P, thickening agent CMC, and binder SBR are added to the solvent deionized water at a mass ratio of 96.5:1.0:1.0:1.5 to make the negative electrode.
  • the conductive member nickel tape
  • the negative active material layer slurry is applied to the main part of the surface of the undercoat layer (ie the diaphragm area) by extrusion coating, leaving a stripe-shaped blank on the surface of the undercoat layer near the edge , And then dried at 85°C to obtain the negative active material layer, and then form a supporting protective layer on the surface of the undercoating layer of the extension area as needed, and then post-processing to obtain that the surfaces of the diaphragm area and the extension area are provided with conductive bottom Coated negative pole piece.
  • the positive pole piece (compact density: 3.4g/cm 3 ), PP/PE/PP separator and negative pole piece (compact density: 1.6g/cm 3 ) are wound together into a bare cell
  • the core is then placed in the battery case, and electrolyte is injected (the EC:EMC volume ratio is 3:7, LiPF 6 is 1mol/L), followed by sealing and chemical conversion processes, and finally a lithium ion secondary battery (below Referred to as battery).
  • Method 1 Charge and discharge the lithium-ion battery at 45°C, that is, charge to 4.2V with 1C current, then discharge to 2.8V with 1C current, record the discharge capacity of the first week; then make the battery go 1C/1C charge and discharge cycle 1000 weeks, record the battery discharge capacity at the 1000th week, divide the discharge capacity at the 1000th week by the discharge capacity at the first week to obtain the capacity retention rate at the 1000th week.
  • Method 2 Charge and discharge the lithium-ion battery at 45°C, that is, first charge it to 4.2V with a current of 0.3C, then discharge it to 2.8V with a current of 0.3C, and record the discharge capacity in the first week;
  • the battery is subjected to a 0.3C/0.3C charge and discharge cycle for 1000 weeks, and the battery discharge capacity at the 1000th week is recorded.
  • the discharge capacity at the 1000th week is divided by the discharge capacity at the first week to obtain the capacity retention rate at the 1000th week.
  • Adjust the secondary battery to 50% SOC with 1C current at 25°C, and record the voltage U1. Then discharge with 4C current for 30 seconds, and record the voltage U2. DCR (U1-U2)/4C. Then the battery is subjected to a 1C/1C charge and discharge cycle for 500 weeks, and the DCR of the 500th week is recorded. The DCR of the 500th week is divided by the DCR of the first week and subtracted by 1 to obtain the DCR growth rate of the 500th week.
  • the secondary batteries (10 samples) were fully charged to the charge cut-off voltage with a current of 1C, and then charged at a constant voltage until the current dropped to 0.05C, and the charging was stopped.
  • the weight percentage of the current collector refers to the weight of the positive electrode current collector per unit area divided by the weight of the conventional positive current collector per unit area.
  • the weight percentage of the current collector is the unit area The weight of the negative current collector divided by the weight of the conventional negative current collector per unit area as a percentage.
  • the Young's modulus of PI used in each current collector is 1.9 GPa
  • the Young's modulus of PET used is 4.2 GPa.
  • Nickel-based alloy nickel, 90wt%; chromium, 10wt%.
  • Double-layer protective layer a nickel metal protective layer arranged on the surface of the conductive layer facing away from the support layer, with a thickness of 20nm; and a nickel oxide protective layer arranged on the surface of the nickel metal protective layer facing away from the support layer, with a thickness of 30nm.
  • Table 3 shows the cycle performance data measured after assembling the battery with the pole pieces listed in Table 2 (without conductive primer).
  • the cycle life of the battery using the composite current collector is good, which is equivalent to the cycle performance of the conventional battery.
  • the battery capacity retention rate of a battery made of a current collector containing a protective layer can be further improved compared to a battery made of a current collector without a protective layer, indicating that the battery is more reliable.
  • the following takes the positive pole piece as an example to illustrate the effect of the composite current collector on improving the safety of battery nail penetration.
  • Lithium-ion batteries using composite current collectors have a thinner conductive layer than traditional metal current collectors, resulting in smaller metal burrs under abnormal conditions such as nail penetration, and the support layer of the composite current collector has a larger short-circuit resistance. Conducive to improving the safety performance of battery nail penetration. As can be seen from the above table, conventional batteries will suffer thermal runaway and destruction under nail penetration and cannot pass the nail penetration safety test. All lithium-ion batteries using composite current collectors can pass the nail penetration safety test.
  • Table 8 shows the specific composition and related parameters of the batteries of each embodiment and comparative example and the electrode pole pieces and current collectors used therein (in Table 6 except for the comparative positive pole piece 20, the rest of the positive pole pieces are all provided with a conductive primer Floor).
  • Table 7 shows the performance measurement results of each battery. Unless otherwise specified, the conductive primer layer in each pole piece is only provided in the diaphragm area.
  • the composite current collector When a composite current collector with a thinner conductive layer is used (that is, the comparative positive pole piece 20 without a conductive primer layer), the composite current collector has poorer conductivity than traditional metal current collectors, and the composite current collector is conductive The layer is easy to be damaged and other shortcomings, the DCR of the battery is large, and the cycle capacity retention rate is low.
  • the conductive primer layer After the introduction of the conductive primer layer, the conductive primer layer effectively repairs the surface of the current collector and constructs a conductive network between the current collector, the conductive primer layer and the active material, which improves the electron transmission efficiency and reduces the current collector and electrode active materials. Layer resistance, which can effectively reduce DCR.
  • the DCR of the battery can be improved to a greater extent.
  • flake graphite can produce "horizontal sliding", which acts as a buffer to reduce the damage to the conductive layer of the current collector during the compaction process, thereby reducing cracks, the introduction of flake graphite can further reduce the battery DCR ( Positive pole piece 24vs. Positive pole piece 29).
  • the DCR of the battery can also be more significantly improved.
  • the thickness of the conductive primer layer is too large, it is not conducive to the improvement of the energy density of the battery.
  • the active material layer and the current collector have better binding force.
  • the entire diaphragm layer ie, the active material layer and the conductive primer layer
  • the binding force between the layer and the composite current collector is also good, so that the active material layer (or membrane layer) can effectively wrap the metal burrs generated in the conductive layer under abnormal conditions such as nail penetration, so as to improve the battery penetration. Nail safety performance.
  • the positive electrode piece As an example, the effect of the content of the binder in the electrode active material layer in improving the electrochemical performance of the battery will be explained from the perspective of battery nailing safety.
  • the positive electrode pieces are prepared according to the method described in the previous embodiment, but the composition of the positive electrode active material layer slurry is adjusted to prepare multiple positive electrode pieces with different binder content in the positive electrode active material layer.
  • the specific pole piece composition is shown in the table below.
  • Table 9 shows the nail penetration test results when the above-mentioned different positive pole pieces are assembled into a battery. The results show that the higher the content of the binder in the positive electrode active material layer, the better the nail penetration safety performance of the corresponding battery.
  • the binder content in the positive electrode active material layer is not less than 1 wt%, more preferably not less than 1.5 wt%, and most preferably not less than 2 wt%.
  • the composite current collector used is: a 1 ⁇ m thick Al metal layer is vapor-deposited on both surfaces of a 10 ⁇ m PET.
  • the two surfaces of the composite current collector are coated by extrusion coating, that is, the middle is the high coating weight area, and the two sides are the low coating weight areas (can be achieved by extrusion gaskets or baffles), at 85°C Dry down.
  • the width of the high coat weight area is 4 cm
  • the width of the low coat weight area is 2.1 cm.
  • the compacted density of the high coat weight area is 3.45 g/cm 3
  • the compacted density of the low coat weight area is both 3.3 g/cm 3 .
  • Compaction density test method first cut 30 small current collector discs with area S to measure their weight and thickness, calculate the weight average value m1 and height average H1, and then cut out the very small discs with area S 30 pieces, calculate the weight average m2 and height average H2, then:
  • the current collector is also prepared using the above-mentioned 10 ⁇ m thick PET Al-plated composite current collector, which is similar to the preparation method of the positive electrode sheet above, but the positive electrode active material layer slurry is directly uniformly coated on the two surfaces of the composite current collector Above, that is, no partitioning treatment is performed, and then post-treatment is performed to obtain a uniformly coated comparative positive pole piece.
  • the compaction density of the positive electrode active material layer is 3.4 g/cm 3 .
  • the current collector is a metal Al foil with a thickness of 12 ⁇ m. Similar to the preparation method of the comparative positive electrode above, the positive electrode active material layer slurry is directly and uniformly coated on the two surfaces of the Al foil current collector, and then Processing to obtain conventional positive pole piece.
  • the composite current collector used is: a 1 ⁇ m thick Cu metal layer is vapor-deposited on both surfaces of a 10 ⁇ m PET.
  • the negative active material artificial graphite, the conductive agent Super-P, the thickener CMC, and the binder SBR are added to the solvent deionized water at a mass ratio of 96.5:1.0:1.0:1.5 to make the negative active material layer slurry.
  • the two surfaces of the composite current collector are coated by extrusion coating, that is, the middle is the high coating weight area, and the two sides are the low coating weight areas (can be achieved by extrusion gaskets or baffles), at 85°C After drying, the negative electrode active material layer is obtained.
  • the width of the high coat weight area is 4.5 cm
  • the width of the low coat weight area is 2 cm.
  • the compacted density of the high coat weight area is 1.7 g/cm 3
  • the compacted density of the low coat weight area is both 1.6 g/cm 3 .
  • the current collector is also prepared with the above-mentioned 10 ⁇ m thick PET Cu-plated composite current collector, which is similar to the preparation method of the negative pole piece above, but the negative active material layer slurry is directly and evenly coated on both surfaces of the composite current collector On top, that is, without partitioning treatment, after post-treatment, a uniformly coated comparative negative pole piece is obtained.
  • the compaction density of the negative electrode active material layer is: 1.65 g/cm 3 .
  • the current collector is a metal Cu foil with a thickness of 8 ⁇ m, similar to the preparation method of the comparative negative electrode plate uniformly coated above, the negative active material layer slurry is directly coated on the two surfaces of the Cu foil current collector, and then After post-processing, a conventional negative pole piece is obtained.
  • the flatness test of the pole piece is characterized by measuring the arc height of the pole piece relative to the reference plane.
  • the specific measurement method of arc height is as follows:
  • the width of the plane is slightly smaller than the length of the electrode pad sample, and then place an equal weight on each side of the sample (1Kg) weight to make the sample close to the plane. Then use a soft ruler to measure the height of the middle of the sample above the plane. The height above is the arc height.
  • the pole pieces with arc height less than or equal to 2mm are flat, and the positive and negative pole pieces can be accurately aligned when assembled into a battery.
  • the conventional positive pole piece or negative pole piece using a metal current collector meets the requirements of the flatness of the pole piece (the arc height is less than or equal to 2mm), and can achieve accurate alignment during battery assembly.
  • the composite current collector is uniformly coated according to the conventional process. If no additional treatment is performed, the arc height of the pole piece is relatively large (greater than 5mm), the flatness of the pole piece is not good, and it is difficult to achieve precise alignment during battery assembly.
  • the arc height is significantly reduced to a degree similar to that of conventional pole pieces, and precise alignment during battery assembly can be achieved.
  • the following describes the influence of the distribution of the conductive primer on the performance of the pole piece, especially the overcurrent capability.
  • the diaphragm area and the extension area have a primer layer
  • the diaphragm area and the extension area have a primer layer and the extension area has a supporting protective layer.
  • Positive pole piece and then measure the fusing time of the lug to compare the overcurrent capability of different types of pole pieces.
  • the electrode active material layer is coated by partition coating to ensure that the conductive layer in the electrode pole piece is less damaged, while the pole piece production efficiency is high; the layout of the extension area is shown in Figure 17C Shown.
  • the above test data shows that setting a primer layer in only the diaphragm area can improve the overcurrent energy of the pole piece, and on this basis, setting a primer and further supporting protection layer in the extension area can further improve the overcurrent capacity of the pole piece .

Abstract

本申请涉及一种电极极片和电化学装置及其装置。本申请的电极极片包括集流体、设置于所述集流体至少一个表面上的电极活性材料层、与所述集流体电连接的电连接构件，所述电极活性材料层设置于所述集流体的主体部分，该区域称为膜片区，所述电连接构件与所述集流体在所述集流体边缘处焊接连接，该焊接区域称为转接焊区域，所述膜片区与转接焊区域之间的集流体的未涂覆电极活性材料层的过渡区域称为延伸区，所述集流体为复合集流体，且在集流体的膜片区的集流体与电极活性材料层之间以及在集流体的延伸区的表面均设置有包含粘结剂和导电材料的导电底涂层。

Description

一种电极极片、电化学装置及其装置
相关申请的交叉引用
本申请要求于2019年6月28日递交的名称为“一种电极极片和电化学装置”的中国专利申请No.201910580127.8的优先权，其内容在此通过援引全部并入本申请。
技术领域
本申请涉及电池领域，具体地讲，涉及一种电极极片、电化学装置及其装置。
背景技术
锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。随着锂离子电池的应用范围不断扩大，大家对锂离子电池的重量能量密度和体积能量密度的要求也越来越高。
为了得到质量能量密度和体积能量密度较高的锂离子电池，通常对锂离子电池进行如下改进：(1)选择放电比容量高的正极材料或负极材料；(2)优化锂离子电池的机械设计，使其体积最小化；(3)选择高压实密度的正极极片或负极极片；(4)对锂离子电池的各部件进行减重。
其中，对集流体的改进通常是选择重量较轻或厚度较小的集流体，例如可以采用打孔集流体或镀有金属层的塑料集流体等。
对于采用镀有金属层的塑料集流体(复合集流体)的极片和电池来说，虽然能量密度得以提高，但是有可能带来加工性能和电化学性能等方面的一些问题或性能劣化。要得到电化学性能好的极片和集流体，还需要很多方面 的改进。
为了克服现有技术之不足，特提出本申请。
发明内容
鉴于此，本申请部分实施例提供一种电极极片、电化学装置及其装置。
第一方面，本申请提供一种电极极片，包括集流体、设置于所述集流体至少一个表面上的电极活性材料层、与所述集流体电连接的电连接构件，所述电极活性材料层设置于所述集流体的主体部分，该区域称为膜片区，所述电连接构件与所述集流体在所述集流体边缘处焊接连接，该焊接区域称为转接焊区域，所述膜片区与转接焊区域之间的集流体的未涂覆电极活性材料层的过渡区域称为延伸区，所述集流体包括支撑层和设置于支撑层至少一个表面上的导电层，所述导电层的单面厚度D2满足：30nm≤D2≤3μm，所述支撑层为高分子材料层或高分子复合材料层，且在集流体的膜片区的集流体与电极活性材料层之间以及在集流体的延伸区的表面均设置有包含粘结剂和导电材料的导电底涂层。
第二方面，本申请提供一种电化学装置，包括正极极片、负极极片、隔离膜和电解液，其中所述正极极片和/或负极极片为本申请第一方面所述的电极极片。
第三方面，本申请还提供一种装置，包括本申请第二方面所述的电化学装置，所述电化学装置可以用作所述装置的电源，所述电化学装置也可以作为所述装置的能量存储单元。
相对于现有技术，本申请的技术方案至少具有以下有益的效果。
第一，本申请的电极极片采用复合集流体，由于该复合集流体具有较薄的导电层且支撑层为高分子材料或高分子复合材料，因此可以显著改善电化学装置的能量密度，例如重量能量密度。
第二，该复合集流体由于具有较薄的导电层，因此在穿钉等异常情况下，产生的金属毛刺较小，而且具有高分子材料或高分子复合材料作为支撑 层，因此在穿钉等异常情况下短路电阻较传统的金属集流体大，所以大大改善了电化学装置的穿钉安全性能。
第三，由于复合集流体的导电层较薄(相对于例如铝箔或铜箔的常规金属箔片集流体而言)，往往会导致导电层易发生破损、极片极化较大、极片过流能力较差、电池工作过程中产热较多等问题。为了解决这些问题，在本申请中，在复合集流体的膜片区和延伸区的表面均设置有包含粘结剂和导电材料的导电底涂层。导电底涂层可以提高集流体和活性物质之间的粘结力，保证电极活性材料层更牢固地设置于复合集流体的表面，并改善电极极片的过流能力和电化学性能，通过改善导电层的界面，导电底涂层可以使电子在整个极片上更流畅地进行导通，减少极化、增加极片过流能力，也可以很好地解决极片上电流分布不均，局部极化较大的问题；从而使得采用复合集流体的极片具有与采用常规金属箔片集流体的极片相当或甚至更佳的电性能。
因此，本申请的电极极片和含有该电极极片的电化学装置(例如锂离子电池)兼具良好的能量密度、电化学性能(尤其是良好的过流能力)和安全性能。
本申请的装置包括本申请提供的电化学装置，因而至少具有与所述电化学装置相同的优势。
附图说明
下面结合附图和具体实施方式，对本申请的电极极片、电化学装置进行详细说明。
图1为本申请一具体实施方式的正极集流体的剖视结构示意图。
图2为本申请又一具体实施方式的正极集流体的剖视结构示意图。
图3为本申请又一具体实施方式的正极集流体的剖视结构示意图。
图4为本申请又一具体实施方式的正极集流体的剖视结构示意图。
图5为本申请一具体实施方式的负极集流体的剖视结构示意图。
图6为本申请又一具体实施方式的负极集流体的剖视结构示意图。
图7为本申请又一具体实施方式的负极集流体的剖视结构示意图。
图8为本申请又一具体实施方式的负极集流体的剖视结构示意图。
图9为本申请一具体实施方式的正极极片的膜片区剖视结构示意图。
图10为本申请又一具体实施方式的正极极片的膜片区剖视结构示意图。
图11为本申请又一具体实施方式的正极极片的膜片区剖视结构示意图。
图12为本申请又一具体实施方式的正极极片的膜片区剖视结构示意图。
图13为本申请一具体实施方式的负极极片的膜片区剖视结构示意图。
图14为本申请又一具体实施方式的负极极片的膜片区剖视结构示意图。
图15为本申请又一具体实施方式的负极极片的膜片区剖视结构示意图。
图16为本申请又一具体实施方式的负极极片的膜片区剖视结构示意图。
图17A为本申请一具体实施方式的正极极片的俯视结构示意图。
图17B为本申请又一具体实施方式的正极极片的俯视结构示意图。
图17C为本申请又一具体实施方式的正极极片的俯视结构示意图。
图17D为本申请又一具体实施方式的正极极片的俯视结构示意图。
图17E为图17A至17D所示一具体实施方式(例如图17C)的正极极片的剖视结构示意图。
图18为本申请一具体实施方式的正极极片的剖视结构示意图。
图19为本申请一具体实施方式的正极极片的俯视结构示意图。
图20是根据本申请一具体实施方式的电化学装置作为锂离子二次电池的立体图。
图21是图20所示的锂离子二次电池的分解图。
图22是根据本申请一具体实施方式的电池模块的立体图。
图23是根据本申请一具体实施方式的电池包的立体图。
图24是图23所示电池包的分解图。
图25是根据本申请一具体实施方式的装置的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5二次电池
51外包装
52电极组件
53顶盖组件
具体实施方式
下面结合具体实施方式，进一步阐述本申请。应理解，这些具体实施方式仅用于说明本申请而不用于限制本申请的范围。
本申请的第一方面涉及一种电极极片，包括集流体、设置于所述集流体至少一个表面上的电极活性材料层、与所述集流体电连接的电连接构件，所述电极活性材料层设置于所述集流体的主体部分，该区域称为膜片区，所述电连接构件与所述集流体在所述集流体边缘处焊接连接，该焊接区域称为转接焊区域，所述膜片区与转接焊区域之间的集流体的未涂覆电极活性材料层的过渡区域称为延伸区，所述集流体包括支撑层和设置于支撑层至少一个表面上的导电层，所述导电层的单面厚度D2满足：30nm≤D2≤3μm，所述支撑层为高分子材料层或高分子复合材料层，且在集流体的膜片区的集流体与电极活性材料层之间以及在集流体的延伸区的表面均设置有包含粘结剂和导电材料的导电底涂层。
显然，所述电极极片可以是正极极片或负极极片。电极极片是正极极片时，相应地，其中的集流体和电极活性材料层分别为正极集流体和正极活性材料层。电极极片是负极极片时，相应地，其中的集流体和电极活性材料层分别为负极集流体和负极活性材料层。
用于本申请第一方面所述电极极片的集流体是一种复合集流体，其由至少两种材料复合而成。在结构上，所述集流体包括支撑层和设置于支撑层至少一个表面上的导电层，所述导电层的单面厚度D2满足：30nm≤D2≤3μm。因此，所述集流体中起导电作用的是导电层。该导电层厚度D2远小于现有技术中常用的诸如Al箔或Cu箔等金属集流体的厚度(常用的Al箔、Cu箔金属集流体的厚度通常为12μm和8μm)，因此可以提高使用该极片的电化学装置(例如锂电池)的质量能量密度和体积能量密度。此外，该复合集流体还可以大大改善极片的穿钉安全性能，这是因为该复合集流体具有较薄的导电层，因此在穿钉等异常情况下，产生的金属毛刺较小，而且还具有高分子材料或高分子复合材料作为的支撑层，因此在穿钉等异常情况下短路电阻较传统的金属集流体大，这些因素一起作用大大改善了电化学装置的穿钉安全性能。
但是，由于这种复合集流体的导电层较薄，所以相对于传统的金属集流体(Al箔或Cu箔)而言，复合集流体的导电能力较差，且导电层容易在极片加工过程中产生破损，进而影响电化学装置的电化学性能。因此，本申请的电极极片中，在复合集流体的膜片区的集流体与电极活性材料层之间设置有包含导电材料和粘结剂的导电底涂层，以解决上述技术问题。导电底涂层通过有效修补集流体的表面并构筑集流体、导电底涂层与活性物质间的导电网络，提高电子传输效率，降低含有复合集流体的极片电阻，从而可以有效降低电芯直流内阻(DCR)，提高电芯功率性能，并保证电芯在长期循环过程中不易于发生较大的极化及析锂等现象，即有效改善了电芯的长期可靠性；此外，导电底涂层还可以改善复合集流体与电极活性材料层之间的界面，提高集流体和活性物质之间的粘结力，保证电极活性材料层更牢固地设置于复 合集流体的表面。
此外，在复合集流体的导电层的表面电连接极耳(即电连接构件)之后，由于导电层较薄且易于破损，因此电极极片(尤其是极耳处)的过流能力较差，在电池工作过程中产热较多，极化较大。因此，在本申请的电极极片中，除了在复合集流体的膜片区的集流体与电极活性材料层之间设置导电底涂层外，还在集流体延伸区的表面设置包含导电材料和粘结剂的导电底涂层，以解决上述技术问题。导电底涂层可以改善电极极片的过流能力和电化学性能，通过改善导电层的界面，导电底涂层可以使电子在整个极片上更流畅地进行导通，减少极化、增加极片过流能力，也可以很好地解决极片上电流分布不均，局部极化较大的问题。
因此，本申请的电极极片和含有该电极极片的电化学装置(例如锂离子电池)兼具良好的能量密度、电化学性能(尤其是良好的过流能力)和安全性能。
此外，因为延伸区的集流体的导电层较传统的金属集流体薄，为了防止被破坏，例如导电层破损、折断等，在优选的实施方式中，可以增大延伸区的导电底涂层的厚度或增加其中导电材料的含量、或在导电底涂层的表面额外设置支撑保护层，可以防止该处的集流体受到机械损坏，而影响极片的导电性能，从而进一步改善极片的过流能力。因此，在根据本申请某些优选实施方式的电极极片中，所述集流体的延伸区的导电底涂层的厚度大于膜片区的导电底涂层的厚度，或者所述集流体的延伸区的导电底涂层中的导电材料的含量高于膜片区的导电底涂层中的导电材料的含量，或者在所述集流体的延伸区的导电底涂层的表面还设置有支撑保护层，所述支撑保护层为有机绝缘层或无机绝缘层。
此外，由于复合集流体的支撑层(高分子材料或高分子复合材料)的反弹程度较传统金属集流体大，因此如果按照传统工艺，在复合集流体的表面进行涂布后再经辊压工艺进行压实，还可能会导致一系列的其它问题。由于支撑层的反弹，会导致极片两侧的边缘上翘，使得极片整体产生弧度，从 而导致极片变形。极片变形有可能导致电极活性材料层与复合集流体分离、导电层破损、导电层从支撑层剥离等，进而使极片电化学性能劣化。另一方面，极片的变形也会使得正负极极片无法精确对准。因此，由复合集流体制备的电极极片容易产生内阻偏大、极化较大等技术问题。现有技术中为了解决复合集流体导致的极片变形问题往往要在活性材料浆料干燥过程或者辊压过程中采用一些特殊技术手段来释放应力，或者采用常规工艺而不得不牺牲良品率。鉴于此，在本申请的优选实施方式中，除了对电极极片的厚度方向的材料分布进行设计外，还对电极极片的活性材料层的横向方向(即与极片表面平行的方向)的材料分布进行了特殊设计。根据本申请的该优选实施方式，电极极片的电极活性材料层基于压实密度包括沿极片宽度方向(即与涂布方向垂直的方向)分布的2n+1(n＝1、2或3)个区域，且中间区域的压实密度高于两侧区域的压实密度，这种特殊的分区设计可以有效抑制复合集流体及电极极片由于辊压等而导致的弧度和边缘翘曲，从而使得电极极片在辊压之后仍保持较好的极片平整度，消除或减小极片内阻偏大、极化较大等技术问题，且有利于保护导电层不易破损，从而使得极片具有良好的过流能力且电化学装置具有良好的电化学性能。
下面对本申请第一方面提供的电极极片(以及其中的集流体)的结构、材料和性能等进行详细描述。
集流体导电层
相对于传统的金属集流体来说，在本申请实施方式的集流体中，导电层起到导电和集流的作用，用于为电极活性材料层提供电子。
导电层的材料选自金属导电材料、碳基导电材料中的至少一种。
所述金属导电材料优选铝、铜、镍、钛、银、镍铜合金、铝锆合金中的至少一种。
所述碳基导电材料优选石墨、乙炔黑、石墨烯、碳纳米管中的至少一种。
导电层的材料优选为金属导电材料，即导电层优选为金属导电层。其 中，当集流体为正极集流体时，通常采用铝为导电层的材料；当集流体为负极集流体时，通常采用铜为导电层的材料。
当导电层的导电性较差或厚度太小时，会造成电池的内阻较大、极化较大，当导电层的厚度太大时，则不足以起到改善电池重量能量密度和体积能量密度的效果。
所述导电层的单面厚度为D2，D2优选满足：30nm≤D2≤3μm，更优选300nm≤D2≤2μm，最优选为500nm≤D2≤1.5μm；以便更好的保证集流体的轻质性能并兼具良好的导电性能。
在本申请优选实施方式中，导电层的单面厚度D2的上限可为3μm、2.5μm、2μm、1.8μm、1.5μm、1.2μm、1μm、900nm，导电层的单面厚度D2的下限可为800nm、700nm、600nm、500nm、450nm、400nm、350nm、300nm、100nm、50nm、30nm；导电层的单面厚度D2的范围可由上限或下限的任意数值组成。优选地，300nm≤D2≤2μm；更优选为500nm≤D2≤1.5μm。
由于本申请中导电层的厚度较小，因此在极片制作等过程中，易产生裂纹等破损。通常，在本申请所述电极极片的导电层中有裂纹存在。导电层中的裂纹通常不规则地存在于导电层中，可以是长条形裂纹、可以为交叉型裂纹、可以为发散状裂纹等；可以是贯穿整个导电层的裂纹，也可以是在导电层的表层形成的裂纹。导电层中的裂纹通常是由于在极片加工过程中的辊压、焊接极耳振幅过大、基材收卷张力过大等情况造成的。
导电层可通过机械辊轧、粘结、气相沉积法(vapor deposition)、电镀、化学镀(Electroless plating)中的至少一种形成于支撑层上，气相沉积法优选物理气相沉积法(Physical Vapor Deposition，PVD)；物理气相沉积法优选蒸发法、溅射法中的至少一种；蒸发法优选真空蒸镀法(vacuum evaporating)、热蒸发法(Thermal Evaporation Deposition)、电子束蒸发法(electron beam evaporation method，EBEM)中的至少一种，溅射法优选磁控溅射法(Magnetron sputtering)。
优选气相沉积法、电镀或化学镀中的至少一种，以使得支撑层与导电 层之间的结合更牢固。
集流体支撑层
在本申请实施方式的集流体中，支撑层对导电层起到支撑和保护的作用。由于支撑层一般采用有机高分子材料或高分子复合材料，因此支撑层的密度通常小于导电层的密度，从而较传统的金属集流体可显著提升电池的重量能量密度。
并且，金属层采用厚度较小的金属层，可进一步提高电池的重量能量密度。并且由于支撑层可以对位于其表面的导电层起到良好的承载和保护作用，因而不易产生传统集流体中常见的极片断裂现象。
所述支撑层的材料选自绝缘高分子材料、绝缘高分子复合材料、导电高分子材料、导电高分子复合材料中的至少一种。
绝缘高分子材料例如选自聚酰胺、聚对苯二甲酸酯、聚酰亚胺、聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、芳纶、聚二甲酰苯二胺、丙烯腈-丁二烯-苯乙烯共聚物、聚对苯二甲酸丁二醇酯、聚对苯二甲酰对苯二胺、聚丙乙烯、聚甲醛、环氧树脂、酚醛树脂、聚四氟乙烯、聚苯硫醚、聚偏氟乙烯、硅橡胶、聚碳酸酯、纤维素及其衍生物、淀粉及其衍生物、蛋白质及其衍生物、聚乙烯醇及其交联物、聚乙二醇及其交联物中的至少一种。
绝缘高分子复合材料例如选自绝缘高分子材料与无机材料形成的复合材料，其中无机材料优选陶瓷材料、玻璃材料、陶瓷复合材料中的至少一种。
导电高分子材料例如选自聚氮化硫类高分子材料或经掺杂的共轭类高分子材料，比如聚吡咯、聚乙炔、聚苯胺、聚噻吩等中的至少一种。
导电高分子复合材料例如选自绝缘高分子材料与导电材料形成的复合材料，其中导电材料选自导电碳材料、金属材料、复合导电材料中的至少一种，其中导电碳材料选自碳黑、碳纳米管、石墨、乙炔黑、石墨烯中的至少一种，金属材料选自镍、铁、铜、铝或上述金属的合金中的至少一种，复合导电材料选自镍包覆的石墨粉、镍包覆的碳纤维中的至少一种。
根据应用环境的实际需要和成本等因素，本领域技术人员可以合理地选择和确定支撑层的材料。本申请中所述支撑层的材料优选为绝缘高分子材料或绝缘高分子复合材料，尤其是当集流体为正极集流体时。
当集流体为正极集流体时，通过采用具有绝缘层支撑、且具有特定厚度的导电层的复合集流体，可以明显改善电池的安全性能。由于绝缘层不导电，因此其电阻较大，可以提高电池在异常情况下发生短路时的短路电阻，使短路电流大幅度减小，因此可极大地降低短路产热量，从而改善电池的安全性能；且导电层较薄，因此在穿钉等异常情况下，局部的导电网络被切断，防止电化学装置大面积甚至整个电化学装置发生内短路，这就可以将穿钉等造成的电化学装置的损坏局限于刺穿位点，仅形成“点断路”，而不影响电化学装置在一定时间内的正常工作。
支撑层的厚度为D1，D1优选满足：1μm≤D1≤20μm；更优选1μm≤D1≤15μm。
由于支撑层含量适中，使得支撑层的机械强度能够适应极片加工工艺，并提高集流体的电池的体积能量密度。
其中，支撑层的厚度D1的上限可为20μm、15μm、12μm、10μm、8μm，下限可为1μm、1.5μm、2μm、3μm、4μm、5μm、6μm、7μm；支撑层的厚度D1的范围可由上限或下限的任意数值组成。优选的，1μm≤D1≤15μm；更优选2μm≤D1≤10μm；最优选3μm≤D1≤8μm。
同时，本申请特定的厚度可以进一步保证该集流体具有较大的电阻，显著降低电池在发生内短路时的电池升温，当导电层为铝时，还可显著减少或防止正极集流体的铝热反应，从而保证电池具有良好的安全性能。
此外，当导电层为金属导电层时，优选支撑层的常温杨氏模量满足：20GPa≥E≥1.9GPa。优选地，20GPa≥E≥4GPa。
本申请中所述支撑层的常温杨氏模量的测试方法如下：
取支撑层样品裁剪成15mm×200mm，用万分尺量取样品的厚度h(μm)，常温常压下使用高铁拉力机进行拉伸测试，设置初始位置，并使夹具 之间样品为50mm长，拉伸以50mm/min速度进行，记录拉伸至断裂的载荷L(N)，设备位移y(mm)，则应力ε＝L/(15×h)×1000，应变η＝y/50×100，绘制应力应变曲线，取初始线性区曲线，该曲线的斜率既为杨氏模量E。
由于金属相对于高分子或高分子复合材料刚性较强，即在极片加工的辊压等过程中变形较小，因此为了确保支撑层和导电层之间的形变差别不至于过大，以至于将导电层撕裂，所述支撑层的常温杨氏模量最好满足：20GPa≥E≥1.9Gpa，从而可以使得支撑层具有一定的刚性，且可进一步提高支撑层与导电层之间的刚性匹配性，从而在集流体、电极极片的加工过程中，保证支撑层与导电层的形变量不会差别太大。
由于支撑层具有一定的刚性(20GPa≥E≥1.9GPa)，因此在集流体、电极极片的加工过程中，集流体不易变形或不易延展太大，从而可使得支撑层与导电层之间结合牢固，不易脱离，且可防止导电层“被迫”延展而导致的导电层破损。且根据本申请的集流体具有一定的韧性，从而可使得集流体和电极极片具有一定的承受变形的能力，不易于断带。
但是支撑层的杨氏模量不能过大，否则刚性过强，会造成收卷及卷绕困难、可加工性变差。当20GPa≥E，可以保证支撑层具有一定的柔性，还可使得电极极片具有一定的承受变形的能力。
此外，优选支撑层在90℃的热收缩率不大于1.5％，从而在极片加工过程中，可以更好的保证集流体的热稳定性。
集流体的保护层
在本申请的一些优选实施方式中，所述集流体还设置有保护层，所述保护层设置于所述集流体的导电层的一个表面上或设置于所述集流体的导电层的两个表面上，即导电层的远离支撑层的表面上和面对支撑层的表面上。
保护层可为金属保护层或金属氧化物保护层。保护层可以防止集流体的导电层受到化学腐蚀或机械损坏而导致的破损，此外还可以增强集流体的机械强度，从而可以改善集流体及极片的过流能力。
优选保护层设置于集流体的导电层的两个表面上。导电层的下保护层 (即设置于导电层的面对支撑层的表面上的保护层)不仅可以防止导电层受到损坏、增强集流体的机械强度，还可以增强支撑层与导电层之间的结合力，防止脱膜(即支撑层与导电层分离)。
导电层的上保护层(即设置于导电层的远离支撑层的表面上的保护层)的技术效果主要是防止加工过程中导电层被破坏、腐蚀等(例如电解液浸泡、辊压等都会对导电层表面造成影响)。由于本申请的电极极片中采用导电底涂层来修复导电层在辊压、卷绕等过程中可能产生的裂纹，增强导电性，弥补该复合集流体作为集流体方面的不足，因此导电层的上保护层可以与导电底涂层协同作用进一步为导电层提供保护作用，从而共同改善复合集流体作为集流体的导电效果。
由于良好的导电性，金属保护层不仅可以进一步改进导电层的机械强度和耐蚀性，还能降低极片的极化。所述金属保护层的材料例如选自镍、铬、镍基合金、铜基合金中的至少一种，优选镍或镍基合金。
其中，镍基合金是以纯镍为基体加入一种或几种其他元素所构成的合金。优选为镍铬合金，镍铬合金是金属镍和金属铬形成的合金，可选的，镍元素与铬元素的摩尔比为1:99～99:1。
铜基合金是以纯铜为基体加入一种或几种其他元素所构成的合金。优选为铜镍合金，可选的，在铜镍合金中，镍元素与铜元素的摩尔比为1：99～99：1。
保护层选用金属氧化物时，由于金属氧化物的延展性小、比表面积大、硬度大，同样也可形成对导电层的有效支撑和保护，并对于改善支撑层与导电层之间的结合力具有良好的技术效果。金属氧化物保护层的材料例如选自氧化铝、氧化钴、氧化铬、氧化镍中的至少一种。
当作为正极集流体时，根据本申请的复合集流体的保护层优选采用金属氧化物，以在达到良好的支撑和保护的技术效果的同时，进一步改善正极极片和电池的安全性能；当作为负极集流体时，根据本申请的复合集流体的保护层优选采用金属，以在达到良好的支撑和保护的技术效果的同时，进一 步改善极片的导电性和电池的动力学性能，以减小电池极化；当作为负极集流体时，根据本申请的复合集流体的保护层更优选包含金属保护层和金属氧化物保护层的双层保护层，优选为在导电层的表面设置金属保护层，并在金属保护层的表面再设置金属氧化物保护层，该双层保护层可以更好地起到改善负极集流体的导电性能、耐腐蚀性能以及防机械破坏等作用。
所述保护层的厚度为D3，D3优选满足：D3≤1/10×D2且1nm≤D3≤200nm。如果保护层太薄，则不足以起到保护导电层的作用；保护层太厚，则会降低电池的重量能量密度和体积能量密度。更优选的，5nm≤D3≤500nm，进一步优选10nm≤D3≤200nm，最优选10nm≤D3≤50nm。
位于导电层的两个表面上的保护层的材料可相同或不同，厚度可相同或不同。
优选，下保护层的厚度小于上保护层的厚度，以有利于改善电池的重量能量密度。
进一步可选的，下保护层厚度D3”与上保护层厚度D3'的比例关系为：1/2×D3'≤D3”≤4/5×D3'。
当集流体为正极集流体时，通常采用铝为导电层的材料，下保护层优选选用金属氧化物材料。相对于下保护层的材料选用金属来讲，金属氧化物材料具有较大电阻，因此该类型的下保护层可以在一定程度上进一步增大正极集流体的电阻，从而进一步的提高电池异常情况下发生短路时的短路电阻，改善电池的安全性能。此外，由于金属氧化物的比表面积更大，所以金属氧化物材料的下保护层与支撑层之间的结合力增强；同时由于金属氧化物的比表面积更大，因此下保护层可以增加支撑层表面的粗糙度，起到增强导电层与支撑层之间的结合力的作用，从而提高了集流体整体的强度。
当集流体为负极集流体时，通常采用铜为导电层的材料，保护层优选选用金属材料。更优选的，在包含至少一层金属保护层的基础上，下保护层和下保护层中的至少一个还包含金属氧化物保护层，以期同时改善负极复合集流体的导电性和界面结合力。
集流体
图1至图8示出了根据本申请某些实施方式的电极极片中所采用的集流体的结构示意图。
正极集流体的示意图如图1至图4所示。
在图1中，正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101相对的两个表面上的正极集流体导电层102，还包括设置于正极集流体导电层102的下表面(即朝向正极集流体支撑层101的面)上的正极集流体保护层103，即下保护层。
在图2中，正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101相对的两个表面上的正极集流体导电层102，还包括设置于正极集流体导电层102的相对两个表面上的正极集流体保护层103，即下保护层和上保护层。
在图3中，正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101一个表面上的正极集流体导电层102，还包括设置于正极集流体导电层102的朝向正极集流体支撑层101的面上的正极集流体保护层103，即下保护层。
在图4中，正极集流体集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101一个表面上的正极集流体导电层102，还包括设置于正极集流体导电层102的相对两个表面上的正极集流体保护层103，即下保护层和上保护层。
同样的，负极集流体的示意图如图5至图8所示。
在图5中，负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201相对的两个表面上的负极集流体导电层202，还包括设置于负极集流体导电层202的朝向负极集流体支撑层201的面上的负极集流体保护层203，即下保护层。
在图6中，负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201相对的两个表面上的负极集流体导电层202，还包括设置于 负极集流体导电层202的相对两个表面上的负极集流体保护层203，即下保护层和上保护层。
在图7中，负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201一个表面上的负极集流体导电层202，还包括设置于负极集流体导电层202的朝向负极集流体支撑层201方向上的负极集流体保护层203，即下保护层。
在图8中，负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201一个表面上的负极集流体导电层202，还包括设置于负极集流体导电层202的相对两个表面上的负极集流体保护层203，即下保护层和上保护层。
位于导电层的两个相对的表面上的保护层的材料可相同或不同，厚度可相同或不同。
其中，对于用于根据本申请的电极极片的集流体而言，如图1、图2、图5、图6所示，可在支撑层的相对的两个表面上均设置有导电层，或者如图3、图4、图7、图8所示，也可在仅支撑层的一面上设置有导电层。(图中虽然示出了仅包含下保护层的情况，但可以理解的是，也可以仅包含上保护层)
另外，虽然本申请的电极极片所采用的复合集流体优选地如图1至8所示含有集流体保护层，但是应该理解：集流体保护层并非集流体的必须结构，在某些实施方式中所用的集流体可以不含集流体保护层。
电极极片的电极活性材料层
电极极片的电极活性材料层设置在复合集流体的一个或两个表面的主要部分上(在本申请中，该部分称为集流体的膜片区)。另外，在复合集流体与电极活性材料层之间还设置有导电底涂层(后文讨论)。用于本申请电极极片的电极活性材料层通常包括电极活性材料、粘结剂和导电剂。根据需要，电极活性材料层还可以包括可选的其它添加剂或助剂。
对于正极极片而言，可以选用本领域常用的各种电极活性材料(即正极活性材料)。例如，对于锂电池来说，正极活性材料可选自锂钴氧化物、锂 镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物、过渡金属磷酸盐、磷酸铁锂等，但本申请并不限定于这些材料，还可以使用其他可被用作锂离子电池正极活性物质的传统公知的材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。优选地，正极活性材料可选自LiCoO 2、LiNiO 2、LiMnO 2、LiMn 2O 4、LiNi 1/3Co 1/3Mn 1/3O 2(NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM 523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM 811)、LiNi 0.85Co 0.15Al 0.05O 2、LiFePO 4、LiMnPO 4中的一种或几种。
对于负极极片而言，可以选用本领域常用的各种电极活性材料(即负极活性材料)。例如，对于锂电池来说，负极活性材料可选自例如石墨(人造石墨或天然石墨)、导电炭黑、碳纤维等碳质材料，例如Si、Sn、Ge、Bi、Sn、In等金属或半金属材料或其合金，含锂氮化物或含锂氧化物，锂金属或锂铝合金等。
对于本申请的电极极片来说，优选电极活性材料层中的活性材料的平均粒径D50为5～15μm。如果D50太小，则压实后，极片的孔隙率较小，不利于电解液的浸润，且其较大的比表面积易与电解液产生较多副反应，降低电芯可靠性；如果D50太大，则易于在极片压实过程中对导电底涂层和复合集流体造成较大的损坏。D50指活性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。D50例如可以使用激光衍射粒度分布测量仪(例如Malvern Mastersizer 3000)进行测量。
电极活性材料层中的导电剂可以为导电碳材料、金属材料中的至少一种；其中，导电碳材料选自零维导电碳，如乙炔黑、导电炭黑；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。
电极活性材料层中的粘结剂可以选自丁苯橡胶，油性聚偏氟乙烯(PVDF)，聚偏氟乙烯共聚物(如PVDF-HFP共聚物、PVDF-TFE共聚物)、羧甲基纤维素钠，聚苯乙烯，聚丙烯酸，聚四氟乙烯，聚丙烯腈、聚酰亚胺、 水性PVDF、聚氨酯、聚乙烯醇、聚丙烯酸酯、聚丙烯酸-聚丙烯腈共聚物、聚丙烯酸酯-聚丙烯腈共聚物中的至少一种。
本领域技术人员熟知，将电极活性材料、导电剂和粘结剂等组成的浆料涂覆到电极集流体(或预先涂覆到电极集流体的底涂层)上，再经干燥等后处理即可得所需的电极活性材料层。
传统的电极极片可以涂覆有一层或多层电极活性材料层，但是不管单层涂覆还是多层涂覆，在整个极片表面的涂覆区域内，电极活性材料层一般都是均匀涂覆的，而且冷压(辊压)操作也是针对极片表面整体进行的，由此所得到的极片上的电极活性材料层的压实密度也是基本一致的，不会有明显差异。
在根据本申请的一些优选实施方式的电极极片中，从所述电极极片被涂布表面的宽度方向看，电极活性材料层基于压实密度包括2n+1(n＝1、2或3)个区域，且中间区域的压实密度高于两侧区域的压实密度；优选地n＝1。以优选的实施方式为例，电极活性材料层基于压实密度包括三个区域，且中间区域的压实密度高于两侧区域的压实密度。由于在冷压(辊压)等过程之后，极片两侧区域的压实密度低，而中间区域的压实密度高，即在冷压(辊压)等过程中极片两侧区域处承受的压力小于中间区域，由此可以避免极片加工过程中由于复合集流体的反弹而导致的复合集流体和电极极片易于产生的边缘翘曲和弧度，有利于形成表面平整的极片，从而有利于保证电化学装置的电化学性能。且有利于保护导电层不易破损，从而保证电极极片良好的过流能力。
在本申请中，电极极片表面的“长度方向”和“宽度方向”分别是指表面的两个维度，其中长度方向是指主要维度方向(即尺寸较大的方向)，而宽度方向是指次要维度方向(即尺寸较小的方向)。通常，长度方向与极片加工过程中的各个材料层(例如电极活性材料层)的涂覆方向是一致的，也与电化学装置(例如电池)制造过程中极片的卷绕方向是一致的；而宽度方向是与长度方向垂直的。
要形成根据本申请的基于压实密度的活性材料层的2n+1个区域，可以采用分区涂布的方法实现，即利用挡板或垫片在极片表面划分出不同的区域(或界限)，在每个区域涂覆不同重量的电极活性材料浆料，这样在辊压之后就形成了压实密度不同的活性材料层区域。此外，两侧区域的压实密度优选为相同，这样的设计有利于更好地保证电极极片的平整度。
在根据本申请的一些优选实施方式的电极极片中，基于电极活性材料层的总重量，电极活性材料层中的粘结剂含量优选不小于1wt％，更优选不小于1.5wt％，最优选不小于2wt％。对于本申请的电极极片来说，当电极活性材料层中的粘结剂的含量较高时，则可以增强活性材料层与复合集流体之间的结合力，从而可以抑制由于加工过程中支撑层的较大反弹而导致的复合集流体与电极活性材料层之间的结合力劣化，从而保证电极活性材料层不易与复合集流体分离。若两者之间结合力不足，则电池内阻较大、极化加大，电化学性能较差。并且较高的结合力使得在穿钉等异常情况下，活性材料层可有效地包裹导电层中产生的金属毛刺，以改善电池的穿钉安全性能。粘结剂含量保持在这一范围内，则活性材料层与集流体间的结合力较好，从而使得在穿钉等异常情况下，活性材料层可更有效地包裹导电层中产生的金属毛刺，以改善电池的穿钉安全性能。
图9至图16示出了根据本申请某些实施方式的电极极片膜片区的剖视结构示意图。
正极极片膜片区的示意图如图9至图12所示。
在图9中，正极极片在膜片区包括正极集流体10和设置于正极集流体10相对的两个表面上的正极活性材料层11，而正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101相对的两个表面上的正极集流体导电层102以及设置于正极导电层102一侧或两侧的正极保护层103(图中未示出)。
在图10中，正极极片在膜片区包括正极集流体10和设置于正极集流体10一个表面上的正极活性材料层11，而正极集流体10包括正极集流体支 撑层101和设置于正极集流体支撑层101一个表面上的正极集流体导电层102以及设置于正极导电层102一侧或两侧的正极保护层103(图中未示出)。
在图11中，正极极片PP在膜片区包括正极集流体10和设置于正极集流体10相对的两个表面上的导电底涂层12和正极活性材料层11，而正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101相对的两个表面上的正极集流体导电层102。
在图12中，正极极片PP在膜片区包括正极集流体10和设置于正极集流体10一个表面上的导电底涂层12和正极活性材料层11，而正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101一个表面上的正极集流体导电层102。
负极极片膜片区的示意图如图13至图16所示。
在图13中，负极极片在膜片区包括负极集流体20和设置于负极集流体20相对的两个表面上的负极活性材料层21，而负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201相对的两个表面上的负极集流体导电层202以及设置于负极导电层202一侧或两侧的负极保护层203(图中未示出)。
在图14中，负极极片在膜片区包括负极集流体20和设置于负极集流体20一个表面上的负极活性材料层21，而负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201一个表面上的负极集流体导电层202以及设置于负极导电层202一侧或两侧的负极保护层203(图中未示出)。
在图15中，负极极片NP在膜片区包括负极集流体20和设置于负极集流体20相对的两个表面上的导电底涂层22和负极活性材料层21，而负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201相对的两个表面上的负极集流体导电层202。
在图16中，负极极片NP在膜片区包括负极集流体20和设置于负极集流体20一个表面上的导电底涂层22和负极活性材料层21，而负极集流体20包括负极集流体支撑层201和设置于负极集流体支撑层201一个表面上的 负极集流体导电层202。
如图9至图16所示，电极活性材料层可以设置于集流体的一个表面上，也可以设置于集流体的两个表面。
本领域技术人员可以理解：当采用设置有双面导电层的集流体时，电极极片既可以双面涂布(即电极活性材料层设置于集流体的两个表面)，也可以仅单面涂布(即电极活性材料层仅设置于集流体的一个表面上)；而当采用仅设置有单面导电层的集流体时，电极极片也仅能单面涂布，且电极活性材料层(以及导电底涂层)仅能涂布在集流体设置有导电层的一面。
电极极片的导电底涂层
在本申请中，复合集流体的表面根据涂覆材料和位置的不同可划分成三个区域：位于主体部分用于设置电极活性材料层的膜片区、在边缘部分用于焊接电连接构件(也称极耳)的转接焊区域、以及作为两者之间过渡区域的延伸区。
在本申请中，在复合集流体之上可以设置导电底涂层。具体的说，在本申请中，导电底涂层既设置于集流体膜片区的导电层与电极活性材料层(又可称为膜片层)之间，又设置于集流体的延伸区的导电层的表面。而在转接焊区域处的集流体的导电层的表面(通常情况下为焊印下方)视情况可以设置或不设置导电底涂层(为了操作方便，如先焊接极耳再设置材料层，则可以不设置导电底涂层，反之，如先设置材料层再焊接极耳，则可以设置导电底涂层，也可以不设置导电底涂层)。
根据需要，导电底涂层在复合集流体的膜片区和延伸区表面的分布布局可以有多种设计，下面参考附图17A、17B、17C和17D进行详细说明。
图17A示意性地示出了本申请一具体实施方式的正极极片的俯视图。如图所示，正极极片包括复合集流体10和在边缘处与集流体10通过焊接而电连接的多个电连接构件(极耳)511。集流体10在位于其主体部分的膜片区A设置有导电底涂层和活性材料层；集流体10与极耳511焊接重叠在一起的区域为转接焊区域C；而膜片区A与转接焊区域C之外的过渡区域即延伸 区B，延伸区B的表面也设置有导电底涂层。
图17B示意性地示出了本申请又一具体实施方式的正极极片的俯视图。如图所示，正极极片包括复合集流体10和在几个边缘突出处与集流体10通过焊接而电连接的多个电连接构件(极耳)511。集流体10在位于其主体部分的膜片区A设置有导电底涂层和活性材料层(全部主体部分作为膜片区A)。集流体10的几个突出部作为延伸区B，在延伸区B表面设置有导电底涂层，极耳511与延伸区B重叠的区域为转接焊区域C。
图17C示意性地示出了本申请又一具体实施方式的正极极片的俯视图。如图所示，正极极片包括复合集流体10和在几个边缘突出处与集流体10通过焊接而电连接的多个电连接构件(极耳)511。集流体10的主体部分的大部分区域作为膜片区A，但在边缘留有条形区域与几个突出部一起作为延伸区B；在膜片区A设置有导电底涂层和活性材料层，而在延伸区B仅设置有导电底涂层。极耳511与延伸区B重叠的区域为转接焊区域C。
图17D示意性地示出了本申请又一具体实施方式的正极极片的俯视图。如图所示，正极极片包括复合集流体10和在边缘处与集流体10通过焊接而电连接的带状电连接构件511。集流体10在位于其主体部分的膜片区A设置有导电底涂层和活性材料层；集流体10与电连接构件511焊接重叠在一起的区域为转接焊区域C；而膜片区A与转接焊区域C之间的过渡区域为延伸区B，延伸区B的表面也设置有导电底涂层。
图17E示意性地示出了图17A至17D所示某些具体实施方式的正极极片的剖视结构示意图(例如17C的X-X剖视图)。如图所示，正极极片PP包括复合集流体10和与集流体10通过焊接而电连接的电连接构件511。而正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101一个表面上的正极集流体导电层102以及设置于正极导电层102一侧或两侧的正极保护层103(图中未示出)。与例如17C所示一致，正极集流体10根据其表面设置的材料层的不同可分成三个区域：膜片区A、延伸区B和转接焊区域C；膜片区A占据了正极集流体10表面的主要部分，其上依次形成有导电 底涂层12和正极活性材料层11，转接焊区域C提供了正极集流体10与电连接构件511之间的电连接界面，而延伸区B表面上同样设置有导电底涂层12(但未设置正极活性材料层11)。
图17A至17E示出了采用具有一个导电层的单面复合集流体的正极极片的结构示意图。但是本领域技术人员可以理解，本申请的极片还可以采用具有两个导电层的双面复合集流体，此时导电底涂层和正极活性材料层也设置于复合集流体的两个表面上。此外，本领域技术人员可以理解，也可以对负极极片进行类似的设计。
在本申请中，导电底涂层可以改善复合集流体的界面，可以很好地克服复合集流体导电能力较差、且复合集流体中的导电层易于破损等缺点，通过有效修补集流体的表面并构筑集流体、导电底涂层与活性物质间的导电网络，提高电子传输效率，降低集流体与电极活性材料层电阻，从而可以有效降低电芯直流内阻，提高电芯功率性能，并保证电芯在长期循环过程中不易于发生较大的极化及析锂等现象，即有效改善了电芯的长期可靠性；此外，还可以提高集流体和活性物质之间的粘结力，保证电极活性材料层更牢固地设置于复合集流体的表面；另外，在复合集流体的膜片区和延伸区均设置有导电底涂层，可以改善电极极片的过流能力和电化学性能，通过改善导电层的界面，导电底涂层可以使电子在整个极片上更流畅地进行导通，减少极化、增加极片过流能力，也可以很好地解决极片上电流分布不均，局部极化较大的问题。
所述导电底涂层包含导电材料和粘结剂。基于所述导电底涂层的总重量，导电材料的重量百分含量为10％～99％，优选20％～80％，更优选为50％～80％；所述粘结剂的重量百分含量为1％～90％，优选20％～80％，更优选为20％～50％。该比例可以有助于改善电极极片的导电性以及集流体与电极活性材料层之间的结合力。除了导电材料和粘结剂，所述导电底涂层还可包含可选的其他添加剂或助剂。
导电材料为导电碳材料、金属材料中的至少一种；导电底涂层中的导 电材料与活性材料层中的导电剂可以相同或不同。
其中，导电碳材料选自零维导电碳(如乙炔黑、导电炭黑)，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。
优选的导电材料含有一维导电碳材料或二维导电碳材料。因为加入二维导电碳材料后，在极片压实过程中，导电底涂层中的二维导电碳材料可以产生“水平滑动”，从而起到缓冲作用，减少压实过程中对集流体的导电层的破坏，从而减少裂纹。优选的二维导电碳材料的粒径D50为0.01～0.1μm。优选地，二维导电碳材料占所述导电材料的1wt％～50wt％。另外由于一维导电碳材料的形貌特殊，因此添加后可以改善导电底涂层的导电性，尤其是在导电材料的添加量一定的情况下，一维导电碳材料相较于其他类型的导电材料可以更好的改善导电底涂层的导电性。优选碳纳米管，其长径比优选为1000～5000。
优选的导电材料为零维导电碳材料与一维导电碳材料的混合材料或者为零维导电碳材料与二维导电碳材料的混合材料。
导电底涂层中的粘结剂与活性材料层中的粘结剂可以相同或不同。
导电底涂层中的粘结剂选自丁苯橡胶，油性聚偏氟乙烯(PVDF)，聚偏氟乙烯共聚物(如PVDF-HFP共聚物、PVDF-TFE共聚物)、羧甲基纤维素钠，聚苯乙烯，聚丙烯酸，聚四氟乙烯，聚丙烯腈、聚酰亚胺、水性PVDF、聚氨酯、聚乙烯醇、聚丙烯酸酯、聚丙烯酸-聚丙烯腈共聚物、聚丙烯酸酯-聚丙烯腈共聚物中的至少一种。
导电底涂层中的粘结剂优选水性粘结剂，如水性PVDF、聚丙烯酸、聚氨酯、聚乙烯醇、聚丙烯酸酯、聚丙烯酸-聚丙烯腈共聚物、聚丙烯酸酯-聚丙烯腈共聚物中的至少一种，这样电化学装置的DCR增长较小。
在本申请中，“水性”高分子材料是指高分子分子链完全伸展开分散在水中，“油性”高分子材料是指高分子分子链完全伸展开分散在油性溶剂中。本 领域技术人员理解，通过采用合适的表面活性剂可以将同一类的高分子材料分别分散在水中和油中，即通过采用合适的表面活性剂，同一类的高分子材料可以被分别做成水性高分子材料和油性高分子材料。例如，本领域技术人员可以根据需要，将PVDF改性为水性PVDF或油性PVDF。
导电底涂层的单面厚度H优选为：0.1μm至5μm。优选H/D2为0.5:1至5:1。比例过小，则不能有效地起到改善导电层裂纹、改善极片导电性能的作用；比例过大，则不仅会降低电池的重量能量密度，还会增大电池DCR，不利于电池动力学性能的改善。
在本申请的极片中，所述集流体膜片区的导电底涂层与所述集流体延伸区的导电底涂层的材料组成可以相同或不同，厚度可相同或不同。
在本申请的优选实施例中，复合集流体的延伸区的导电底涂层的厚度大于膜片区的导电底涂层的厚度，或者复合集流体的延伸区的导电底涂层中的导电材料的含量高于膜片区的导电底涂层中的导电材料的含量。这样的设置，可以更好地改善集流体的延伸区处的过流能力，且可以保证整个电极极片具有较高的重量能量密度。
电极极片的支撑保护层
由于采用了复合集流体，在延伸区的集流体的导电层较传统的金属集流体薄，因此为了防止被破坏，例如导电层破损、折断等，在优选的实施方式中，在复合集流体的延伸区的导电底涂层的表面还设置有支撑保护层，从而可以改善复合集流体的延伸区处的机械强度和硬度、防止集流体的延伸区发生弯曲、变形，防止延伸区处的导电层发生损坏，从而可以改善该处的过流能力。所述支撑保护层为有机绝缘层或无机绝缘层。
有机绝缘层可以选自绝缘胶带层或绝缘胶涂层。其中，绝缘胶涂层例如选自聚偏氟乙烯层、聚偏二氟乙烯层、偏二氟乙烯-六氟丙烯共聚物层、丁苯橡胶层、羧甲基纤维素钠层、聚丙烯酸层、聚丙烯酸钠层、聚环氧乙烷层、聚乙烯醇层中的至少一种。
无机绝缘层可以选自氧化铝层、氧化镁层、氧化锌层、氧化硅层、氧 化钛层、氧化锆层、氮化铝层、氮化硅层、氟化钙层、氟化钡层中的中的至少一种。
所述无机绝缘层可以包含绝缘填料和粘结剂，其中优选的绝缘填料为氧化铝、氧化镁、氧化锌、氧化硅、氧化钛、氧化锆、氮化铝、氮化硅、氟化钙、氟化钡中的中的至少一种，优选的粘结剂为聚偏氟乙烯、聚偏二氟乙烯、偏二氟乙烯-六氟丙烯共聚物、丁苯橡胶、羧甲基纤维素钠、聚丙烯酸、聚环氧乙烷、聚乙烯醇中的至少一种。无机绝缘层中绝缘填料的百分含量一般为大于或等于50wt％，以保证该层具有一定的硬度和机械强度，粘结剂的百分含量一般为小于50wt％，优选为0.1wt％～20wt％。
图18示意性地示出了本申请一个具体实施方式的在延伸区的导电底涂层表面设置有支撑保护层的正极极片的剖视图。如图所示，正极极片PP包括复合集流体10和与集流体10通过焊接而电连接的电连接构件511。而正极集流体10包括正极集流体支撑层101和设置于正极集流体支撑层101一个表面上的正极集流体导电层102以及设置于正极导电层102一侧或两侧的正极保护层103(图中未示出)。正极集流体10根据其表面设置的材料层的不同可分成三个区域：膜片区A、延伸区B和转接焊区域C；膜片区A占据了正极集流体10表面的主要部分，其上依次形成有导电底涂层12和正极活性材料层11，转接焊区域C提供了正极集流体10与电连接构件511之间的电连接界面，而延伸区B表面上设置有导电底涂层12和支撑保护层15。
图18以单面复合集流体为例对支撑保护层进行了说明，但是本领域技术人员理解，支撑保护层也可以设置于双面复合集流体的两面。此外，本领域技术人员可以理解，也可以对负极极片进行类似的设计。
电极极片
本申请的电极极片可以采用本领域常用的各种方法进行制备。例如，可以先准备复合集流体，再制备导电底涂层浆料，将导电底涂层浆料涂覆到复合集流体的单个或两个表面；干燥后，再涂覆电极活性材料层浆料，然后干燥；最后经后处理和焊接电连接构件得到所需电极极片。在某些实施方式 中，也可以先在复合集流体上形成电连接构件再形成导电底涂层和电极活性材料层。
对于电极活性材料浆料的涂布，可以采用传统的均匀涂布，或者针对复合集流体的特性采用特殊的分区涂布方式进行涂布。在本申请的优选实施方式中，电极极片的电极活性材料层基于压实密度包括沿极片宽度方向(即与涂布方向垂直的方向)分布的2n+1(n＝1、2或3)个区域，且中间区域的压实密度高于两侧区域的压实密度，这种特殊的分区设计可以有效抑制复合集流体及电极极片由于辊压等而导致的弧度和边缘翘曲，从而使得电极极片在辊压之后仍保持较好的极片平整度，消除或减小极片内阻偏大、极化较大等技术问题，且有利于保护导电层不易破损，从而使得极片具有良好的过流能力且电化学装置具有良好的电化学性能。
图19示出了根据本申请某些实施方式的电极极片的俯视结构示意图。如图所示，正极极片PP包括极片本体和一个或多个与其电连接的极耳511；根据涂覆的电极活性材料层的不同，极片本体包括四个区域：与极耳511直接相连的延伸区512、第一低压实区域513、高压实区域514和第二低压实区域515。即，从正极极片PP被涂布表面的宽度方向看，电极活性材料层基于压实密度包括3个区域(即2n+1个区域，其中n＝1)。且中间区域514的压实密度高于两侧区域513、515的压实密度。
在本申请中，中间高压实区域占涂布总区域的比例(在本例中，即514宽度与513宽度+514宽度+515宽度之和的比值)，可以例如为20％～80％，优选为30％～70％，优选地40％～60％，或者更优选地45％～55％。两个低压实区域的宽度可以相同或不同，优选相同。
在本申请中，低压实区域的压实密度比高压实区域的压实密度可以低约5％～30％，例如7％～25％，例如8％～20％，例如8％～18％。
图19以正极极片为例说明了根据本申请的优选的分区涂布方式，负极极片也可以做类似的分区涂布，以达到改善极片过流能力、保持较好的极片平整度、消除或减小极片内阻偏大、极化较大等技术问题，且有利于保护 导电层不易破损，从而使得极片和电化学装置具有良好的电化学性能。
电化学装置
本申请的第二方面提供一种电化学装置，包括正极极片、负极极片、隔离膜和电解液，其中所述正极极片和/或负极极片为根据本申请的第一方面所述的电极极片。
所述电化学装置可以为电容器、一次电池或二次电池。例如可以为锂离子电容器、锂离子一次电池或锂离子二次电池。
图20示出了根据本发明一具体实施方式的电化学装置作为锂离子二次电池的立体图，图21是图20所示锂离子二次电池的分解图。参看图20和图21，根据本申请的锂离子二次电池5(以下简称电池单体5)包括外包装51、电极组件52、顶盖组件53和电解液(未示出)。其中电极组件52收容于外包装51内，电极组件52的数量不受限制，可以为一个或多个。
需要说明的是，图20所示的电池单体5为罐型电池，但本申请并不限于此，电池单体5可以是袋型电池，即壳体51由金属塑膜替代且取消顶盖组件53。
除了使用了本申请的正极极片和/或负极极片外，这些电化学装置的构造和制备方法本身是公知的。由于使用了本申请的电极极片，所述电化学装置可以具有改善的安全性(如穿钉安全性)和电性能。并且本申请的电极极片容易加工，因此可以降低使用了本申请的电极极片的电化学装置的制造成本。
在本申请的电化学装置中，隔离膜以及电解液的具体种类及组成均不受具体的限制，可根据实际需求进行选择。具体地，所述隔离膜可选自聚乙烯膜、聚丙烯膜、聚偏氟乙烯膜以及它们的多层复合膜。当电池为锂离子电池时，通常使用非水电解液作为电解质。作为非水电解液，通常使用在有机溶剂中溶解的锂盐溶液。锂盐例如是LiClO 4、LiPF 6、LiBF 4、LiAsF 6、LiSbF 6等无机锂盐、或者LiCF 3SO 3、LiCF 3CO 2、Li 2C 2F 4(SO 3) 2、LiN(CF 3SO 2) 2、LiC(CF 3SO 2) 3、LiC nF 2n+1SO 3(n≥2)等有机锂盐。非水电解液中使用的有机溶剂 例如是碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸亚乙烯酯等环状碳酸酯，碳酸二甲酯、碳酸二乙酯、碳酸甲基乙酯等链状碳酸酯，丙酸甲酯等链状酯，γ-丁内酯等环状酯，二甲氧基乙烷、二乙醚、二甘醇二甲醚、三甘醇二甲醚等链状醚，四氢呋喃、2-甲基四氢呋喃等环状醚，乙腈、丙腈等腈类，或者这些溶剂的混合物。
在一些实施方式中，所述锂离子二次电池可以组装成电池模块，电池模块所含的锂离子二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。图22是作为一个示例的电池模块4。参照图22，在电池模块4中，多个锂离子二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂离子二次电池5进行固定。可选地，电池模块4还可以包括具有容纳空间的壳体，多个锂离子二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。图23和图24是作为一个示例的电池包1。参照图23和图24，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
装置
本申请第三方面提供一种装置，包括本申请第二方面所述的电化学装置，所述电化学装置可以用作所述装置的电源，也可以作为所述装置的能量存储单元。所述装置包括但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述装置可以根据其使用需求来选择锂离子二次电池、电池模块或电池包。
图25示出了根据本申请一具体实施方式的装置的示意图。该装置可以为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子二次电池(即本申请的电化学装置)的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用锂离子二次电池(即本申请的电化学装置)作为电源。
本领域技术人员可以理解：以上提到的本申请的不同实施方式中对于极片、电极活性材料层等的组分选择、组分含量和材料理化性能参数的各种限定或优选范围可以任意组合，其组合而得到的各种实施方式仍然在本申请范围内，且视为本说明书公开内容的一部分。
除非特别规定，本说明书中涉及的各种参数具有本领域公知的通用含义，可以按本领域公知的方法进行测量。例如，可以按照在本申请的实施例中给出的方法进行测试。另外，各种优选实施方式中给出的各种不同参数的优选范围和选项可以进行任意组合，由此得到的各种组合都视为在本申请的公开范围之内。
以下结合实施例进一步说明本申请的有益效果。
实施例
各实施例和对比例中的电极极片所用的集流体制备方法如下。
1、不具有保护层的集流体的制备
选取一定厚度的支撑层，按照以下条件，分别在其表面通过真空蒸镀、机械辊轧或粘结的方式形成一定厚度的导电层。
(1)真空蒸镀方式的形成条件如下：将经过表面清洁处理的支撑层置于真空镀室内，以1600℃至2000℃的高温将金属蒸发室内的高纯金属丝熔化蒸发，蒸发后的金属经过真空镀室内的冷却系统，最后沉积于支撑层的表面，形成导电层。
(2)机械辊轧方式的形成条件如下：将导电层材料的箔片置于机械 辊中，通过施加20t至40t的压力将其碾压为预定的厚度，然后将其置于经过表面清洁处理的支撑层的表面，最后将两者置于机械辊中，通过施加30t至50t的压力使两者紧密结合。
(3)粘结方式的形成条件如下：将导电层材料的箔片置于机械辊中，通过施加20t至40t的压力将其碾压为预定的厚度；然后在经过表面清洁处理的支撑层的表面涂布PVDF与NMP的混合溶液；最后将上述预定厚度的导电层粘结于支撑层的表面，并于100℃下烘干。
2、具有保护层的集流体的制备
制备具有保护层的集流体有如下几种方式。
(1)先通过气相沉积法或涂布法在支撑层表面设置保护层，然后通过真空蒸镀、机械辊轧或粘结的方式，在上述具有保护层的支撑层表面形成一定厚度的导电层，以制备具有保护层的集流体(保护层位于支撑层与导电层之间)；此外，也可在上述基础上，再在导电层的远离支撑层方向的表面上通过气相沉积法、原位形成法或涂布法形成另外一层保护层，以制备具有保护层的集流体(保护层位于导电层的两个相对的表面)。
(2)先通过气相沉积法、原位形成法或涂布法在导电层的一个表面上形成保护层，然后通过机械辊轧或粘结的方式，将上述具有保护层的导电层设置于支撑层表面，且保护层设置于支撑层与导电层之间，以制备具有保护层的集流体(保护层位于支撑层与导电层之间)；此外，也可在上述基础上，再在导电层的远离支撑层方向的表面上通过气相沉积法、原位形成法或涂布法形成另外一层保护层，以制备具有保护层的集流体(保护层位于导电层的两个相对的表面)。
(3)先通过气相沉积法、原位形成法或涂布法在导电层的一个表面上形成保护层，然后通过机械辊轧或粘结的方式，将上述具有保护层的导电层设置于支撑层表面，且保护层设置于导电层的远离支撑层的表面上，以制备具有保护层的集流体(保护层位于导电层的远离支撑层的表面)。
(4)先通过气相沉积法、原位形成法或涂布法在导电层的两个表面 上形成保护层，然后通过机械辊轧或粘结的方式，将上述具有保护层的导电层设置于支撑层表面，以制备具有保护层的集流体(保护层位于导电层的两个相对的表面)。
(5)在上述“不具有保护层的集流体的制备”的基础上，再在导电层的远离支撑层方向的表面上通过气相沉积法、原位形成法或涂布法形成另外一层保护层，以制备具有保护层的集流体(保护层位于导电层的远离支撑层的表面)。
在制备实例中，气相沉积法采用真空蒸镀方式，原位形成法采用原位钝化方式，涂布法采用刮刀涂布方式。
真空蒸镀方式的形成条件如下：将经过表面清洁处理的样品置于真空镀室内，以1600℃至2000℃的高温将蒸发室内的保护层材料熔化蒸发，蒸发后的保护层材料经过真空镀室内的冷却系统，最后沉积于样品的表面，形成保护层。
原位钝化法的形成条件如下：将导电层置于高温氧化环境中，温度控制在160℃至250℃，同时在高温环境中维持氧气供应，处理时间为30min，从而形成金属氧化物类的保护层。
凹版涂布方式的形成条件如下：将保护层材料与NMP进行搅拌混合，然后在样品表面涂布上述保护层材料的浆料(固含量为20％至75％)，其次用凹版辊控制涂布的厚度，最后在100℃至130℃下进行干燥。
3、极片的制备
1)不带有导电底涂层的正极极片的制备
将92wt％正极活性材料(未指明具体材料的情况下，缺省使用NCM333)、5wt％导电剂Super-P(简称“SP”)和3wt％PVDF，以NMP为溶剂，搅拌均匀配成正极活性材料层浆料(某些实施例的活性材料层浆料组成可能有所变化，此时以该实施例中特别注明的为准)，采用挤压涂布将正极活性材料层浆料分区涂布于按照上述方法制备的复合集流体的两个表面；在85℃下烘干后得到正极活性材料层。
然后进行冷压，然后切割，再在85℃真空条件下烘干4小时，焊接极耳，得到正极极片。
2)常规正极极片的制备
集流体是厚度为12μm的Al箔片，类似于上面正极极片的制备方法，将正极活性材料层浆料直接涂布到Al箔片集流体的表面上，再经后处理得到常规正极极片。
3)膜片区带有导电底涂层的正极极片的制备
采用一定配比的导电材料(如导电炭黑)和粘结剂(如PVDF或聚丙烯酸等)以及可选的活性材料溶于适当的溶剂中(例如NMP或水中)，搅拌均匀配成底涂浆料。
将底涂浆料均匀双面涂覆于复合集流体表面上(边缘部分留出部分空白区作为延伸区并用于焊接极耳)，涂布速度20m/min，并对底涂层进行干燥，烘箱温度为70～100℃，烘干时间为5min。
待底涂层完全干燥后，再将92wt％正极活性材料、5wt％导电剂Super-P(简称“SP”)和3wt％PVDF，以NMP为溶剂，搅拌均匀配成正极活性材料层浆料，采用挤压涂布将正极活性材料层浆料分区涂布于底涂层表面；在85℃下烘干后得到正极活性材料层，再经后处理得到带有导电底涂层的正极极片。
4)膜片区和延伸区的表面均设置有导电底涂层的正极极片的制备
与“3)膜片区带有导电底涂层的正极极片”的制备方法类似，不同之处在于：在涂覆底涂浆料之前，先在延伸区边缘处焊接导电构件(铝带)再涂覆底涂浆料，并且在涂覆底涂浆料时，在整个集流体的表面(包括膜片区的集流体表面和延伸区的集流体表面)涂覆底涂浆料，待底涂层完全干燥后，再将92wt％正极活性材料、5wt％导电剂Super-P(简称“SP”)和3wt％PVDF，以NMP为溶剂，搅拌均匀配成正极活性材料层浆料，采用挤压涂布将正极活性材料层浆料涂布于底涂层表面的主要部分(即膜片区)，而在底涂层靠近边缘的表面上留下带状空白，然后在85℃下烘干后得到正极活性材料层，然后视需要在延伸区的底涂层表面上形成支撑保护层，再经后处理得到膜片区和 延伸区的表面均设置有导电底涂层的正极极片。
5)不带有导电底涂层的负极极片的制备
将负极活性物质人造石墨、导电剂Super-P、增稠剂CMC、粘接剂SBR按质量比96.5:1.0:1.0:1.5加入到溶剂去离子水中混合均匀制成负极活性材料层浆料；采用挤压涂布将负极活性材料层浆料分区涂布于按照上述方法制备的复合集流体的两个表面；在85℃下烘干后得到负极活性材料层。
然后进行冷压，然后切割，再在110℃真空条件下烘干4小时，焊接极耳，得到负极极片。
6)常规负极极片的制备
集流体是厚度为8μm的Cu箔片，类似于上面负极极片的制备方法，将负极活性材料层浆料直接涂布到Cu箔片集流体的表面上，再经后处理得到常规负极极片。
7)膜片区带有导电底涂层的负极极片的制备
采用一定配比的导电材料(如导电炭黑)和粘结剂(如PVDF或聚丙烯酸等)以及可选的活性材料溶于适当的溶剂中(例如NMP或水中)，搅拌均匀配成底涂浆料。
将底涂浆料均匀双面涂覆于复合集流体的表面上(边缘部分留出部分空白区作为延伸区并用于焊接极耳)，涂布速度20m/min，并对底涂层进行干燥，烘箱温度为70～100℃，烘干时间为5min。
待底涂层完全干燥后，再将负极活性物质人造石墨、导电剂Super-P、增稠剂CMC、粘接剂SBR按质量比96.5:1.0:1.0:1.5加入到溶剂去离子水中混合均匀制成负极活性材料层浆料；采用挤压涂布将负极活性材料层浆料分区涂布于底涂层表面；在85℃下烘干后得到负极活性材料层，再经后处理得到带有导电底涂层的负极极片。
8)膜片区和延伸区的表面均设置有导电底涂层的负极极片的制备
与“7)膜片区带有导电底涂层的负极极片”的制备方法类似，不同之处在于：在涂覆底涂浆料之前，先在延伸区边缘处焊接导电构件(镍带)再 涂覆底涂浆料，并且在涂覆底涂浆料时，在整个集流体的表面(包括膜片区的集流体表面和延伸区的集流体表面)涂覆底涂浆料，待底涂层完全干燥后，再将负极活性物质人造石墨、导电剂Super-P、增稠剂CMC、粘接剂SBR按质量比96.5:1.0:1.0:1.5加入到溶剂去离子水中混合均匀制成负极活性材料层浆料，采用挤压涂布将负极活性材料层浆料涂布于底涂层表面的主要部分(即膜片区)，而在底涂层靠近边缘的表面上留下带状空白，然后在85℃下烘干后得到负极活性材料层，然后视需要在延伸区的底涂层表面上形成支撑保护层，再经后处理得到膜片区和延伸区的表面均设置有导电底涂层的负极极片。
4、电池的制备
通过常规的电池制作工艺，将正极极片(压实密度：3.4g/cm 3)、PP/PE/PP隔膜和负极极片(压实密度：1.6g/cm 3)一起卷绕成裸电芯，然后置入电池壳体中，注入电解液(EC:EMC体积比为3:7，LiPF 6为1mol/L)，随之进行密封、化成等工序，最终得到锂离子二次电池(以下简称电池)。
5、电池测试方法
1)锂离子电池循环寿命测试方法
方法1：将锂离子电池于45℃下进行充放电，即先以1C的电流充电至4.2V，然后再以1C的电流放电至2.8V，记录下第一周的放电容量；然后使电池进行1C/1C充放电循环1000周，记录第1000周的电池放电容量，将第1000周的放电容量除以第一周的放电容量，得到第1000周的容量保有率。
方法2：将锂离子电池于45℃下进行充放电，即先以0.3C的电流充电至4.2V，然后再以0.3C的电流放电至2.8V，记录下第一周的放电容量；然后使电池进行0.3C/0.3C充放电循环1000周，记录第1000周的电池放电容量，将第1000周的放电容量除以第一周的放电容量，得到第1000周的容量保有率。
2)DCR增长率的测试方法
在25℃下，以1C电流将二次电池调整至50％SOC，记录电压U1。然后以4C电流放电30秒，记录电压U2。DCR＝(U1-U2)/4C。然后使电池 进行1C/1C充放电循环500周，记录第500周的DCR，将第500周的DCR除以第一周的DCR并减1，得到第500周的DCR增长率。
3)针刺测试
将二次电池(10个样品)以1C电流满充至充电截止电压，再恒压充电至电流降至0.05C，停止充电。用φ8mm的耐高温钢针，以25mm/s的速度，从垂直于电池极板的方向贯穿，贯穿位置宜靠近所刺面的几何中心，钢针停留在电池中，观察电池是否有燃烧、爆炸现象。
6、测试结果和讨论
6.1复合集流体在改善电池重量能量密度方面的作用
各实施例的集流体及其极片具体参数如表1所示(表1中所列各实施例的集流体均未设置保护层)。在表1中，对于正极集流体而言，集流体重量百分数是指单位面积正极集流体重量除以单位面积常规正极集流体重量的百分数，对于负极集流体而言，集流体重量百分数是单位面积负极集流体重量除以单位面积常规负极集流体重量的百分数。如无特别指出，则各集流体中采用的PI的杨氏模量为1.9GPa，采用的PET的杨氏模量为4.2GPa。
表1
Figure PCTCN2019125061-appb-000001
Figure PCTCN2019125061-appb-000002
根据表1可知，本申请采用的复合正极集流体和复合负极集流体的重量相对于传统的集流体都得到了不同程度的减轻，从而可提升电池的重量能量密度。不过当导电层的厚度大于1.5μm以后，对于集流体的减重改善程度变小，尤其是负极集流体。
6.2保护层在改善复合集流体的电化学性能方面的作用
在表1中所列各实施例的集流体基础上，进一步形成保护层，以便研究保护层对于改善复合集流体的电化学性能方面的作用。表2中“正极集流体2-1”表示在表1中“正极集流体2”的基础上形成保护层所得集流体，其它集流体的编号含义类似。
表2
Figure PCTCN2019125061-appb-000003
说明：1)镍基合金：镍，90wt％；铬，10wt％。
2)双层保护层：设置于导电层背向支撑层的表面的镍金属保护层，厚度为20nm；以及设置于镍金属保护层背向支撑层的表面的氧化镍保护层，厚度为30nm。
表3示出了以表2中所列极片(不带导电底涂层)组装成电池后测得的循环性能数据。
表3
Figure PCTCN2019125061-appb-000004
如表3所示，与采用常规的正极极片和常规的负极极片的电池1相比，采用复合集流体的电池的循环寿命良好，与常规的电池的循环性能相当。尤其是含有保护层的集流体制成的电池，相对于不含保护层的集流体制成的电池，其电池的容量保有率可进一步获得提升，说明电池的可靠性更好。
6.3复合集流体对于改善电池穿钉安全的作用
下面以正极极片为例，说明复合集流体对于改善电池穿钉安全的作用。
表4
Figure PCTCN2019125061-appb-000005
(表4中各极片未设置导电底涂层)
表5
电池编号 正极极片 负极极片 穿钉实验结果
电池20 常规正极极片 常规负极极片 全部不通过
电池21 正极极片11 常规负极极片 全部通过
电池22 正极极片12 常规负极极片 全部通过
电池23 正极极片13 常规负极极片 全部通过
电池24 正极极片14 常规负极极片 全部通过
电池25 正极极片15 常规负极极片 全部通过
电池26 正极极片16 常规负极极片 全部通过
采用复合集流体的锂离子电池，由于导电层较传统的金属集流体薄，在穿钉等异常情况下产生的金属毛刺较小，且复合集流体的支撑层具有较大的短路电阻，因此有利于改善电池的穿钉安全性能。从上表中可以看出，常规电池在穿钉情况下会发生热失控和毁坏，不能通过穿钉安全测试。而采用了复合集流体的锂离子电池，均可以通过穿钉安全测试。
6.4导电底涂层在改善电池的电化学性能方面的作用
下面以正极极片为例，说明导电底涂层、以及导电底涂层的组成等因素对于改善电池的电化学性能方面的作用。表8示出了各个实施例和对比例的电池以及其中采用的电极极片和集流体的具体组成和相关参数(表6中除 了对比正极极片20外其余正极极片都设置有导电底涂层)。表7示出了各电池的性能测量结果。如无特别指出，则各极片中导电底涂层仅设置于膜片区。
表6
Figure PCTCN2019125061-appb-000006
表7
Figure PCTCN2019125061-appb-000007
从以上测试数据可以看出：
1).采用导电层较薄的复合集流体时(即不含导电底涂层的对比正极极片20)，由于复合集流体导电能力较传统的金属集流体差、且复合集流体中的导电层易于破损等缺点，电池的DCR较大、循环容量保持率较低。而在引入了导电底涂层后，导电底涂层通过有效修补集流体的表面并构筑集流体、导电底涂层与活性物质间的导电网络，提高电子传输效率，降低集流体与电极活性材料层电阻，从而可以有效降低DCR。
2).随着导电底涂层中的导电剂含量的提高(正极极片21至26)，电池的DCR可得到较大程度的改善。
3).在相同的组成下，水性粘结剂的引入较油性粘结剂可使得DCR的改善程度更明显(正极极片24vs.正极极片27以及正极极片25vs.正极极片28)。
4).由于片状石墨可产生“水平滑动”，从而起到缓冲作用，减少压实 过程中对集流体的导电层的破坏，从而减少裂纹，因此片状石墨的引入可进一步降低电池DCR(正极极片24vs.正极极片29)。
5).随着导电底涂层的厚度的增大(正极极片30至正极极片32)，电池的DCR也可得到更明显的改善。但是若导电底涂层的厚度过大，则不利于电池的能量密度的改进。
6.5电极活性材料层中的粘结剂的含量在改善电池的电化学性能方面的作用
当电极活性材料层中的粘结剂的含量较高时，则活性材料层与集流体的结合力较好，当有导电底涂层时，整个膜片层(即活性材料层和导电底涂层的统称)与复合集流体的结合力也较好，从而使得在穿钉等异常情况下，活性材料层(或膜片层)可有效地包裹导电层中产生的金属毛刺，以改善电池的穿钉安全性能。
下面以正极极片为例，从电池穿钉安全的角度来说明电极活性材料层中的粘结剂的含量在改善电池的电化学性能方面的作用。按照前面实施例所述方法制备正极极片，但是调整正极活性材料层浆料的组成，制得正极活性材料层中粘结剂含量不同的多个正极极片。具体极片组成见下表。
表8
Figure PCTCN2019125061-appb-000008
表9示出了上述不同正极极片组装成电池时的穿钉测试结果。结果表明正极活性材料层中的粘结剂的含量越高时，相应电池的穿钉安全性能越好。优选地，正极活性材料层中的粘结剂含量不小于1wt％，更优选不小于1.5wt％，最优选不小于2wt％。
表9
Figure PCTCN2019125061-appb-000009
6.6电极活性材料层涂布方式对极片性能的影响
下面说明电极极片上的活性材料层的不同的涂布方式对于电极极片平整性的影响。具体地，分别比较了以下3种不同类型的正极极片和负极极片的平整度。为了简化影响因素，比较的各极片均未设置导电底涂层，但是得出的结论对于设置有导电底涂层的极片也是适用的。
1)分区涂布的正极极片
采用的复合集流体为：10μm的PET的两个表面上分别气相沉积有1μm厚的Al金属层。
将92wt％正极活性材料NCM 333、5wt％导电剂Super-P(简称“SP”)和3wt％PVDF，以NMP为溶剂，搅拌均匀配成正极活性材料层浆料。
在复合集流体的两个表面通过挤压涂布进行分区涂布，即中间为高涂布重量区域，两边为低涂布重量区域(可通过挤压垫片或挡板实现)，在85℃下烘干。其中，高涂布重量区域宽度为4cm，低涂布重量区域宽度均为2.1cm。
然后进行冷压、切割，再在85℃真空条件下烘干4小时，焊接极耳，得到正极极片。
高涂布重量区域的压实密度为3.45g/cm 3，低涂布重量区域的压实密 度均为3.3g/cm 3。
压实密度测试方法：首先裁取面积为S的集流体小圆片30片测量其重量及厚度，求取重量平均值m1及高度平均值H1，再裁取面积为S的极片小圆片30片，求取重量平均值m2及高度平均值H2，则：
压实密度＝(m2-m1)/((H2-H1)×S)
2)均匀涂布的对比正极极片
集流体同样采用上面提到的10μm厚PET镀Al复合集流体，类似于上面的正极极片的制备方法进行制备，但是将正极活性材料层浆料直接均匀涂布到复合集流体的两个表面上，即不进行分区处理，再经后处理得到均匀涂布的对比正极极片。正极活性材料层的压实密度为：3.4g/cm 3。
3)常规正极极片
集流体是厚度为12μm的金属Al箔片，类似于上面对比正极极片的制备方法，将正极活性材料层浆料直接均匀地涂布到Al箔片集流体的两个表面上，再经后处理得到常规正极极片。
4)分区涂布的负极极片
采用的复合集流体为：10μm的PET的两个表面上分别气相沉积有1μm厚的Cu金属层。
将负极活性物质人造石墨、导电剂Super-P、增稠剂CMC、粘接剂SBR按质量比96.5:1.0:1.0:1.5加入到溶剂去离子水中混合均匀制成负极活性材料层浆料。
在复合集流体的两个表面通过挤压涂布进行分区涂布，即中间为高涂布重量区域，两边为低涂布重量区域(可通过挤压垫片或挡板实现)，在85℃下烘干后得到负极活性材料层。其中，高涂布重量区域宽度为4.5cm，低涂布重量区域宽度均为2cm。
然后对带有各涂层的集流体进行冷压，然后切割，再在110℃真空条件下烘干4小时，焊接极耳，得到负极极片。
高涂布重量区域的压实密度为1.7g/cm 3，低涂布重量区域的压实密度 均为1.6g/cm 3。
5)均匀涂布的对比负极极片
集流体同样采用上面提到的10μm厚PET镀Cu复合集流体，类似于上面的负极极片的制备方法进行制备，但是将负极活性材料层浆料直接均匀涂布到复合集流体的两个表面上，即不进行分区处理，再经后处理得到均匀涂布的对比负极极片。负极活性材料层的压实密度为：1.65g/cm 3。
6)常规负极极片
集流体是厚度为8μm的金属Cu箔片，类似于上面均匀涂布的对比负极极片的制备方法，将负极活性材料层浆料直接涂布到Cu箔片集流体的两个表面上，再经后处理得到常规负极极片。
对以上6种不同的极片测量极片平整度。极片平整度的测试是通过测量极片相对于参考平面的弧高来表征的。弧高的具体测量方法如下：
取长度为2m的电极极片样品，将样品置于参考平面上并沿着该平面的宽度方向展开，该平面的宽度略小于电极极片样品的长度，然后在样品的两边各放置一个重量相等(1Kg)的重物，以使样品与该平面紧贴。然后用软尺测量样品中间位置高出该平面的高度，该高出的高度即为弧高。实际生产中，一般认为弧高小于等于2mm的极片是平整的，组装成电池时可以实现正负极片的精确对准。
下表为具体测量结果：
表10
极片 弧高
分区涂布的正极极片 小于2mm
均匀涂布的对比正极极片 大于5mm
常规正极极片 小于2mm
分区涂布的负极极片 小于2mm
均匀涂布的负极极片 大于5mm
常规负极极片 小于2mm
根据上表的测量结果可知，采用金属集流体的常规正极极片或负极极片都是满足极片平整度要求的(弧高小于或等于2mm)，可以实现电池组装时的精确对准。而按照常规工艺对于复合集流体进行均匀涂布，如不进行额外处理，则极片的弧高较大(大于5mm)，极片平整度不好，在电池组装时难以实现精确对准。而采用本申请的分区涂布工艺后，弧高明显降低，达到与常规极片近似的程度，可以实现电池组装时的精确对准。这说明，采用活性材料层分区涂布的特殊设计，可以消除或降低含有复合集流体的电极极片在辊压之后可能产生的边缘翘曲和弧度，提高极片平整度，从而实现电池组装时的精确对准，同时可以使电池具有复合集流体所带来的优异的电化学性能和安全性能。
6.7导电底涂层的分布对极片性能的影响
下面说明导电底涂层的分布对极片性能尤其是过流能力的影响。为此，分别制备无底涂层、仅膜片区有底涂层、膜片区和延伸区具有底涂层、以及膜片区和延伸区具有底涂层且延伸区带有支撑保护层的正极极片，然后测量极耳熔断时间来比较不同类型的极片的过流能力。各极片制备过程中电极活性材料层采用分区涂布方式进行涂布，以在保证电极极片中导电层受损程度较小的同时，极片生产效率较高；延伸区的布局采用图17C所示。
极耳熔断时间的具体测试方法如下：
裁取长140mm、宽80mm的U型极片(即具有两个伸出的极耳的极片)，取5片，用转接片焊接到一起，以50A电流进行充电，观测极耳断裂时间，如若不断裂，则电流在50A基础上再增大10A，以此类推。时间越短则表示过流能力越差。
表11
Figure PCTCN2019125061-appb-000010
以上测试数据说明在仅膜片区设置底涂层可以改善极片过流能量，而在此基础上，在延伸区设置底涂层和进一步设置支撑保护层，可以进一步改善极片的过流能力。
本领域技术人员可以理解：以上仅以锂电池为例示出了本申请的极片的应用实例，但是本申请的极片同样可以应用于其它类型的电池或电化学装置，而仍然可以获得本申请的良好技术效果。
根据上述说明书的揭示和教导，本申请所属领域的技术人员还可以对上述实施方式进行适当的变更和修改。因此，本申请并不局限于上面揭示和 描述的具体实施方式，对本申请的一些修改和变更也应当落入本申请的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本申请构成任何限制。

Claims (11)

  1. 一种电极极片，包括集流体、设置于所述集流体至少一个表面上的电极活性材料层，以及与所述集流体电连接的电连接构件；其中
    所述电极活性材料层设置于所述集流体的主体部分，该区域称为膜片区，所述电连接构件与所述集流体在所述集流体边缘处焊接连接，该焊接区域称为转接焊区域，所述膜片区与转接焊区域之间的集流体的未涂覆电极活性材料层的过渡区域称为延伸区；
    所述集流体包括支撑层和设置于所述支撑层至少一个表面上的导电层，所述导电层的单面厚度D2满足：30nm≤D2≤3μm，所述支撑层为高分子材料层或高分子复合材料层；并且
    在所述集流体的膜片区的所述集流体与所述电极活性材料层之间以及在所述集流体的延伸区的表面均设置有包含粘结剂和导电材料的导电底涂层。
  2. 根据权利要求1所述的电极极片，其中，基于所述导电底涂层的总重量，所述导电材料的重量百分含量为10％～99％，优选20％～80％，更优选为50％～80％；和/或，
    基于所述导电底涂层的总重量，所述粘结剂的重量百分含量为1％～90％，优选20％～80％，更优选为20％～50％。
  3. 根据权利要求1或2所述的电极极片，其中，所述导电底涂层的单面厚度H为0.1μm至5μm，更优选H与D2的比例为0.5:1至5:1；和/或
    所述导电底涂层中的粘结剂含有水性粘结剂；和/或
    所述导电材料为零维导电碳材料与一维导电碳材料的混合材料或者为零维导电碳材料与二维导电碳材料的混合材料。
  4. 根据权利要求1至3任一项所述的电极极片，其中，所述导电层为金属导电层，所述金属导电层的材料选自铝、铜、镍、钛、银、镍铜合金、铝锆合金中的至少一种；和/或
    所述支撑层的材料选自绝缘高分子材料、绝缘高分子复合材料、导电高 分子材料、导电高分子复合材料中的至少一种，所述支撑层的材料优选为绝缘高分子材料或绝缘高分子复合材料。
  5. 根据权利要求1至4任一项所述的电极极片，其中，所述支撑层的厚度D1满足：1μm≤D1≤15μm；和/或，所述支撑层的常温杨氏模量E满足：20GPa≥E≥1.9GPa；和/或，所述导电层中有裂纹。
  6. 根据权利要求1至5任一项所述的电极极片，其中，所述集流体的导电层表面还设置有保护层，所述保护层仅设置于所述集流体的导电层的一个表面上或设置于所述集流体的导电层的两个表面上；所述保护层的厚度D3满足：D3≤1/10×D2且1nm≤D3≤200nm，优选10nm≤D3≤50nm。
  7. 根据权利要求1至6任一项所述的电极极片，其中，所述集流体的延伸区的导电底涂层的厚度大于所述膜片区的导电底涂层的厚度，或者所述集流体的延伸区的导电底涂层中的导电材料的含量高于所述膜片区的导电底涂层中的导电材料的含量。
  8. 根据权利要求1至7任一项所述的电极极片，其中，在所述集流体的延伸区的导电底涂层的表面还设置有支撑保护层，所述支撑保护层为有机绝缘层或无机绝缘层；
    优选地，所述有机绝缘层选自绝缘胶带层或绝缘胶涂层，所述绝缘胶涂层选自聚偏氟乙烯层、聚偏二氟乙烯层、偏二氟乙烯-六氟丙烯共聚物层、丁苯橡胶层、羧甲基纤维素钠层、聚丙烯酸层、聚丙烯酸钠层、聚环氧乙烷层、聚乙烯醇层中的至少一种；
    优选地，所述无机绝缘层选自氧化铝层、氧化镁层、氧化锌层、氧化硅层、氧化钛层、氧化锆层、氮化铝层、氮化硅层、氟化钙层、氟化钡层中的至少一种。
  9. 根据权利要求1至8任一项所述的电极极片，其中，从所述电极极片被涂布表面的宽度方向看，所述电极活性材料层基于压实密度包括2n+1个区域，且中间区域的压实密度高于两侧区域的压实密度；其中n＝1、2或3，优选地n＝1；和/或
    所述电极活性材料层包括电极活性材料、粘结剂和导电剂，且所述电极活性材料的平均粒径D50为：5μm～15μm。
  10. 一种电化学装置，包括正极极片、负极极片、隔离膜和电解液，其中，所述正极极片和/或所述负极极片为权利要求1至9任一项所述的电极极片。
  11. 一种装置，包括根据权利要求10所述的电化学装置，所述电化学装置作为所述装置的电源。
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Publication number Priority date Publication date Assignee Title
CN110660957B (zh) * 2018-12-29 2020-12-04 宁德时代新能源科技股份有限公司 一种电极极片和电化学装置
CN111769289B (zh) * 2020-06-18 2023-04-07 合肥国轩高科动力能源有限公司 一种柔性集流体的焊接方法
CN114122312A (zh) * 2020-08-31 2022-03-01 宁德新能源科技有限公司 极片、电化学装置和电子装置
CN214411248U (zh) * 2021-03-23 2021-10-15 宁德时代新能源科技股份有限公司 电极组件、电池单体、电池以及用电设备
CN113328064B (zh) * 2021-05-31 2023-05-26 珠海冠宇电池股份有限公司 一种负极片及电池
CN113328133B (zh) * 2021-05-31 2023-05-26 珠海冠宇电池股份有限公司 一种电池
CN113883882B (zh) * 2021-08-23 2023-03-24 茌平阳之光亲水箔有限公司 一种亲水箔加工的节能降耗系统及其方法
CN115295757A (zh) * 2022-09-08 2022-11-04 珠海冠宇电池股份有限公司 一种极片和电池
WO2024065250A1 (zh) * 2022-09-28 2024-04-04 宁德时代新能源科技股份有限公司 一种负极极片及由其制备的电池
CN115692723B (zh) * 2022-11-08 2024-01-23 厦门海辰储能科技股份有限公司 复合集流体、电芯、电池以及复合集流体的制备方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108598491A (zh) * 2018-06-22 2018-09-28 宁德时代新能源科技股份有限公司 二次电池及其极片
CN208507818U (zh) * 2018-06-29 2019-02-15 宁德时代新能源科技股份有限公司 二次电池及其极片
CN208955108U (zh) * 2018-10-11 2019-06-07 宁德时代新能源科技股份有限公司 二次电池及其电极构件

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1551070A1 (en) * 2002-08-29 2005-07-06 Toyo Kohan Co., Ltd. Composite current collector
WO2013176161A1 (ja) * 2012-05-25 2013-11-28 Ｎｅｃエナジーデバイス株式会社 非水電解液電池用正極電極および非水電解液二次電池
US20150017523A1 (en) * 2012-06-11 2015-01-15 Nec Energy Devices, Ltd. Electrode manufacturing method
EP2966721B1 (en) * 2013-03-07 2018-01-17 NEC Energy Devices, Ltd. Non-aqueous electrolyte secondary battery
KR101586251B1 (ko) * 2013-06-24 2016-01-18 주식회사 제낙스 이차 전지용 집전체 및 이를 이용한 전극
CN105514349B (zh) * 2014-09-24 2018-04-20 比亚迪股份有限公司 锂离子电池正极片及制备方法和锂离子电池
JP2018073723A (ja) * 2016-11-02 2018-05-10 株式会社リコー 電極及び蓄電素子
CN107732146A (zh) * 2017-10-10 2018-02-23 中航锂电（洛阳）有限公司 一种锂离子电池极片及其制备方法，锂离子电池
CN109873160B (zh) * 2017-12-05 2021-05-18 宁德时代新能源科技股份有限公司 一种集流体，其极片和电池

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108598491A (zh) * 2018-06-22 2018-09-28 宁德时代新能源科技股份有限公司 二次电池及其极片
CN208507818U (zh) * 2018-06-29 2019-02-15 宁德时代新能源科技股份有限公司 二次电池及其极片
CN208955108U (zh) * 2018-10-11 2019-06-07 宁德时代新能源科技股份有限公司 二次电池及其电极构件

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP3916845A4 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113285056A (zh) * 2021-05-31 2021-08-20 珠海冠宇电池股份有限公司 一种正极片及电池
CN113285056B (zh) * 2021-05-31 2023-11-21 珠海冠宇电池股份有限公司 一种正极片及电池
CN114551898A (zh) * 2022-02-10 2022-05-27 瑞浦能源有限公司 二次电池用集流体、二次电池极片及其制造方法和二次电池

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