WO2023206405A1 - 正极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

正极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023206405A1
WO2023206405A1 PCT/CN2022/090415 CN2022090415W WO2023206405A1 WO 2023206405 A1 WO2023206405 A1 WO 2023206405A1 CN 2022090415 W CN2022090415 W CN 2022090415W WO 2023206405 A1 WO2023206405 A1 WO 2023206405A1
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Prior art keywords
lithium
conductive
positive electrode
secondary battery
current collector
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PCT/CN2022/090415
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English (en)
French (fr)
Inventor
张翠平
韩昌隆
付成华
任苗苗
常雯
范朋
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2022/090415 priority Critical patent/WO2023206405A1/zh
Priority to EP22924556.8A priority patent/EP4290602B1/en
Priority to CN202280013062.9A priority patent/CN116964766A/zh
Priority to US18/498,072 priority patent/US20240079600A1/en
Publication of WO2023206405A1 publication Critical patent/WO2023206405A1/zh
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/667—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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a positive electrode plate, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries have penetrated into all aspects of daily life, such as cameras, laptops, electric vehicles, etc. And with the great development of lithium-ion battery technology, people have also put forward higher requirements for its safety performance, battery cycle performance, service life, etc. Especially in the field of electric vehicles, how to ensure that lithium-ion batteries have both high safety performance and long cycle performance and service life has become an urgent technical problem that needs to be solved.
  • This application provides a positive electrode plate, a secondary battery, a battery module, a battery pack and an electrical device.
  • the conductive coating provided on the cathode current collector causes the cathode active material layer to be easily decoated.
  • the first aspect of the application provides a positive electrode sheet, including: a current collector, a conductive coating and a positive active layer.
  • the conductive coating is provided on at least one side surface of the current collector.
  • the conductive coating includes a mass content of 20%. ⁇ 50% conductive agent and 50% ⁇ 80% mass content of binder; the positive active layer is set on the surface of the conductive coating away from the current collector, and the positive active material in the positive active layer is a lithium manganate cathode material, at least one of a ternary cathode material and a quaternary cathode material.
  • the conductive coating of the positive electrode piece of the present application alleviates the damage of the positive electrode active particles to the oxide layer on the surface of the aluminum foil during the cold pressing process, and at the same time increases the breaking tensile strength of the electrode piece, effectively avoiding the problem of the electrode piece being broken due to oxidation.
  • the stability of the electronic conduction between the current collector and the cathode active material is ensured by controlling the amount of the conductive agent and binder. property, and enhances the peeling strength between the current collector and the conductive coating, thereby effectively solving the problem of delamination of the cathode active layer, and effectively improving the cycle performance and cycle stability of secondary batteries with the cathode plate.
  • the above-mentioned adhesive is a conductive adhesive, and the volume resistivity of the conductive adhesive is ⁇ 10 -3 ⁇ cm; optionally, the conductive coating includes a mass content of 20% to 30% Conductive agent and conductive adhesive with a mass content of 70% to 80%.
  • a conductive binder is used as the binder. On the basis of ensuring the same electronic conductivity, the amount of conductive agent can be further reduced, thereby correspondingly increasing the amount of binder to further improve the current collector. and the purpose of peel strength between conductive coatings.
  • the above-mentioned conductive adhesive is selected from any one of the group consisting of epoxy resin conductive glue, silicone resin conductive glue, polyimide resin conductive glue, phenolic resin conductive glue, polyurethane conductive glue, or Various.
  • Each of the above-mentioned conductive binders has high chemical stability and thermal stability, so it can meet the long-term cycle use of secondary batteries.
  • the above-mentioned adhesive is an insulating adhesive, and the volume resistivity of the insulating adhesive is ⁇ 10 10 ⁇ cm; optionally, the conductive coating includes a conductive agent with a mass content of 30% to 45% and insulating adhesive with a mass content of 55% to 70%.
  • the adhesive used is an insulating material, so the amount of conductive agent required increases accordingly. The above mass content ensures that the electronic conduction effect and bonding effect of the conductive coating are simultaneously optimized.
  • the above-mentioned insulating adhesive is selected from any one of the group consisting of PVDF, polyacrylonitrile, styrene-butadiene rubber, polyvinyl alcohol, gum arabic, xanthan gum, and polyacrylate. or more.
  • Each of the above-mentioned binders has high bonding strength, good compatibility with the conductive agent, and ideal chemical and thermal stability, so it can meet the long-term cycle use of secondary batteries.
  • the conductive agent includes acetylene black (AB), carbon fiber, conductive carbon black, conductive graphite, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene nanosheets, graphene oxide nanosheets, and Any one or more of the group consisting of micron graphite.
  • AB acetylene black
  • carbon fiber carbon fiber
  • conductive carbon black conductive graphite
  • single-walled carbon nanotubes single-walled carbon nanotubes
  • multi-walled carbon nanotubes graphene nanosheets
  • graphene oxide nanosheets graphene oxide nanosheets
  • the thickness of the conductive coating is 0.5 microns to 5 microns.
  • the thickness of the conductive coating is 0.8 microns to 3 microns.
  • the conductive coating with the above thickness range on the basis of effective bonding between the conductive coating and the current collector, can effectively alleviate the damage of the positive electrode active particles to the oxide layer on the surface of the aluminum foil during the cold pressing process.
  • an effective electron conduction channel can be constructed to ensure that the secondary battery with the positive electrode plate has a sufficiently high volume energy density.
  • the current collector is an aluminum foil, and optionally, the thickness of the aluminum foil is 8 microns to 20 microns; and/or, the tensile strength of the current collector in the longitudinal and transverse directions is ⁇ 175 MPa. To provide better mechanical strength and better meet the long-term cycle use of secondary batteries.
  • the positive active material includes at least one of formulas (I) to (III):
  • M1 is Mn and/or Al
  • M2 is selected from any one or more of the group consisting of Mg, Cu, Zn, Al, Sn, B, Ga, Zr, Cr, Sr, V and Ti. species, 0.8 ⁇ a1 ⁇ 1.2, 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 1, 0 ⁇ z1 ⁇ 1, x1+y1+z1 ⁇ 1, -0.2 ⁇ b1 ⁇ 0.2.
  • M3 is selected from Mg, Cu, Zn, Al, Sn, B, Ga, Zr, Cr, Sr, V and Any one or more of the group consisting of Ti.
  • 0 ⁇ c ⁇ 1, 0 ⁇ x3 ⁇ 1, 0.8 ⁇ a3 ⁇ 1.2, -0.2 ⁇ b3 ⁇ 0.2, M4 is selected from any one of Ni, Co, Mn, and Mg, Cu, Any one or more of the group consisting of Zn, Al, Sn, B, Ga, Zr, Cr, Sr, V and Ti.
  • Each of the above positive active materials is mainly selected from the group consisting of lithium manganate cathode materials, ternary cathode materials, and quaternary cathode materials.
  • the lithium manganate cathode material shown in formula (II) is a doped lithium manganate cathode material. Therefore, on the basis of ensuring high rate, the dissolution of manganese is relatively reduced, thus ensuring high cycle performance.
  • a second aspect of the present application provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • the positive electrode sheet is any positive electrode sheet of the first aspect. Since the conductive coating of the positive electrode piece of the present application alleviates the damage of the positive electrode active particles to the oxide layer on the surface of the aluminum foil during the cold pressing process, it also improves the breaking tensile strength of the electrode piece, effectively avoiding the problem of the electrode piece being broken due to oxidation. And by controlling the amount of conductive agent and binder, it not only ensures the stability of electronic conduction between the current collector and the cathode active material, but also enhances the peeling strength between the current collector and the conductive coating, thereby effectively solving the problem. The problem of decoating of the positive electrode active layer is eliminated, and at the same time, the cycle performance and cycle stability of the secondary battery with the positive electrode sheet are effectively improved.
  • the electrolyte solution includes a lithium salt
  • the lithium salt includes lithium fluorine-containing sulfonyl imide and lithium hexafluorophosphate.
  • the fluorine-containing lithium sulfonylimide is lithium bisfluorosulfonyl imide, lithium bis(trifluoromethyl)fluorosulfonyl imide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide , (fluorosulfonyl) (pentafluoroethylsulfonyl) lithium imide, (trifluoromethylsulfonyl) (difluoromethylsulfonyl) lithium imide, (fluorosulfonyl) (perfluorobutylsulfonyl) ) Lithium imide, any one or more of the group consisting of lithium bis(pentafluoroethylsulfon
  • the total concentration of lithium salt in the electrolyte is 0.6 mol/L to 2 mol/L.
  • the concentration C1 of lithium hexafluorophosphate is 0.1 mol/L to 1 mol/L
  • the concentration C2 of lithium fluorosulfonyl imide is 0.5 mol/L to 1.5 mol/L.
  • fluorine-containing lithium sulfonylimide can be used to improve the conductivity of the electrolyte; at the same time, lithium hexafluorophosphate can also be used to oxidize and form on the cathode current collector during the first charge and discharge process.
  • the aluminum trifluoride film, together with the conductive coating, has the effect of mitigating the corrosion of the fluorinated sulfonylimide lithium on the current collector, thereby further improving the high-temperature cycle performance of the secondary battery.
  • the thickness d of the conductive coating of the positive electrode piece, the concentration C1 of lithium hexafluorophosphate, and the concentration C2 of fluorine-containing lithium sulfonyl imide satisfy the relationship: C2/(5 ⁇ C1) ⁇ d ⁇ lg(C2/C1)+4, where the units of C1 and C2 are mol/L, and the unit of d is ⁇ m.
  • the above-mentioned electrolyte further includes an organic solvent and additives.
  • the organic solvent is selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, and methylpropyl carbonate.
  • the mass content of the organic solvent in the electrolyte is 65% to 85%.
  • the above-mentioned additive is selected from the group consisting of vinylene carbonate, vinyl sulfate, lithium difluoroxaloborate, lithium difluorophosphate, lithium tetrafluoroborate, 1,3-propanesultone, trifluoroborate. At least one of the group consisting of lithium fluoromethanesulfonate and lithium diacetate borate.
  • 1,3-propanesultone can be oxidized in the positive electrode in advance to alleviate the oxidation of fluorinated sulfonylimide lithium at high voltage. Generate gas, thereby better alleviating the corrosion of fluorinated sulfonylimide lithium on the current collector.
  • the total mass content of the above additives in the electrolyte is 0.5% to 7%. In order to give full play to the role of the corresponding additives, it does not affect the performance of the above-mentioned lithium salts.
  • the negative active material of the above-mentioned negative electrode includes natural graphite, artificial graphite, mesophase microcarbon, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn Any one or more of the group consisting of -O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 and Li-Al alloy.
  • the above-mentioned negative electrodes are all commonly used negative electrodes in secondary electrodes in this field. Those skilled in the art can select appropriate negative electrode materials from the above types according to the performance requirements of secondary batteries.
  • a third aspect of the present application provides a battery module, including a secondary battery, and the secondary battery is any secondary battery of the second aspect.
  • a fourth aspect of the present application provides a battery pack, including a battery module, and the battery module is any battery module of the third aspect.
  • the fifth aspect of the present application provides an electrical device, including a secondary battery or a battery module or a battery pack, wherein the secondary battery is any secondary battery of the second aspect, and the battery module is any of the third aspect.
  • a battery module, the battery pack is any battery pack of the fourth aspect.
  • the positive electrode sheet of the present application is corrosion-resistant and the positive active layer adheres stably to the current collector, the secondary batteries, battery modules, battery packs and electrical devices equipped with it have good high-temperature stability and good cycle performance. The advantages.
  • FIG. 1 is a side view of a positive electrode tab according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 3 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 2 .
  • Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the positive electrode base material is usually aluminum foil.
  • the surface of aluminum foil will be oxidized when placed in the air, forming a uniform oxide film.
  • the active material particles will be partially pressed into the aluminum foil, destroying this layer. oxide film at.
  • the electrolyte contains fluorine-containing sulfonyl imide lithium salt
  • the lithium salt is oxidized at the positive electrode, and the oxidation product combines with aluminum.
  • the combined product further dissolves into the electrolyte, causing corrosion pits, which may cause the electrode fragments to break, causing serious problems. Threaten the safety performance and service life of secondary batteries.
  • the patent application with publication number CN 13851724 A discloses a combination of fluorine-containing sulfonyl imide lithium salt and a conductive coating.
  • the introduction of the conductive coating reduces the contact resistance between the current collector and the active material, while also reducing the contact resistance between the current collector and the active material. It can reduce the risk of corrosion caused by the contact between the fluorinated sulfonimide lithium salt and the current collector to a certain extent. It can not only improve the high-rate cycle performance of the electrochemical device and reduce the temperature rise of the electrochemical device, but also slow down the fluorinated sulfonimide lithium salt. The corrosive effect of lithium imide salt on the cathode current collector improves the long-term stability of the electrochemical device.
  • the conductive coating can easily cause the cathode active material layer to peel off from the current collector, thereby affecting the cycle performance of the lithium-ion battery.
  • the conductive coating can slow down the corrosion effect of fluorosulfonyl imide lithium salt on the cathode current collector, it can improve the long-term stability of the electrochemical device.
  • the conductive coating can easily cause the cathode active material layer to peel off from the current collector, thereby affecting the cycle performance of lithium-ion batteries.
  • this application provides a positive electrode plate, a secondary battery, a battery module, a battery pack and a power device.
  • the positive electrode piece includes: a current collector 11, a conductive coating 12 and a positive electrode active layer 13.
  • the conductive coating 12 is disposed on the current collector 11.
  • the conductive coating 12 includes a conductive agent with a mass content of 20% to 50% and a binder with a mass content of 50% to 80%; the positive active layer 13 is disposed away from the current collector of the conductive coating 12
  • the cathode active material in the cathode active layer 13 is at least one of a lithium manganate cathode material, a ternary cathode material, and a quaternary cathode material.
  • the lithium manganate cathode material refers to a doped or undoped LiMn 2 O 4 cathode material with a spinel structure.
  • the ternary cathode material refers to a lithium transition metal oxide with a layered structure and a transition metal site containing at least three elements: Ni, Co, Mn, or Ni, Co, and Al.
  • the quaternary cathode material refers to a lithium transition metal oxide with a layered structure and a transition metal site containing at least four elements: Ni, Co, Mn, and Al.
  • the conductive coating 12 of the positive electrode piece of the present application alleviates the damage of the positive electrode active particles to the oxide layer on the surface of the current collector during the cold pressing process, and at the same time increases the breaking tensile strength of the electrode piece, effectively avoiding the problem of the electrode piece being broken due to oxidation.
  • the stability of the electronic conduction between the current collector and the cathode active material is ensured by controlling the amount of the conductive agent and binder. property, and enhances the peeling strength between the current collector 11 and the conductive coating 12, thereby effectively solving the problem of decoating of the positive active layer 13, and effectively improving the cycle performance and performance of the secondary battery with the positive electrode sheet. Cycling stability.
  • the mass content of the conductive agent and the mass content of the binder in the conductive coating can be any value in the above range.
  • the mass content of the conductive agent can be 20%, 25%, 30%, 35%, 40%, 45% or 50%
  • the mass content of the binder can be 50%, 55%, 60%, 65%, 70%, 75% or 80%.
  • the conductive coating of the present application must not only provide sufficient conductivity, but also must meet the requirements of enhanced adhesion to the positive active layer.
  • the inventor of the present application adjusted the ratio of the conductive agent and the binder and found that when the volume resistivity of the binder has a significant difference, the ratio of the two can be further adjusted to achieve better control of the conductivity. and further improvement of bonding capabilities.
  • the above-mentioned adhesive is a conductive adhesive, and the volume resistivity of the conductive adhesive is ⁇ 10 -3 ⁇ cm; optionally, the conductive coating includes a mass content of 20% ⁇ 30% conductive agent and 70% ⁇ 80% conductive adhesive by mass.
  • a conductive binder is used as the binder. On the basis of ensuring the same electronic conductivity, the amount of conductive agent can be further reduced, thereby correspondingly increasing the amount of binder to further improve the current collector. and the purpose of peel strength between conductive coatings.
  • the conductive adhesive used for its own removal can be selected from the adhesives with conductive properties commonly used in the existing technology. Considering that the better the dispersion of the conductive agent in it, the stronger the conductivity, so in order to further ensure that the conductive agent To give full play to the conductive effect, in some embodiments, the above-mentioned conductive adhesive is selected from the group consisting of epoxy resin conductive glue, silicone resin conductive glue, polyimide resin conductive glue, phenolic resin conductive glue, and polyurethane conductive glue. any one or more of them.
  • the above-mentioned conductive binders have high chemical stability and thermal stability; they also have high dispersibility for inorganic conductive agents, thus ensuring the uniform dispersion of the conductive agents and meeting the long-term and high-performance cycles of secondary batteries. use.
  • the above-mentioned adhesive is an insulating adhesive, and the volume resistivity of the insulating adhesive is ⁇ 10 10 ⁇ cm; optionally, the conductive coating includes a conductive agent with a mass content of 30% to 45% and insulating adhesive with a mass content of 55% to 70%.
  • the volume resistivity of the adhesive used is relatively high, so the amount of conductive agent required increases accordingly. The above mass content ensures that the electronic conduction effect and bonding effect of the conductive coating are simultaneously optimized.
  • the above-mentioned insulating adhesive is selected from PVDF, polyacrylonitrile, styrene-butadiene rubber, polyethylene Any one or more of the group consisting of alcohol, gum arabic, xanthan gum, and polyacrylate.
  • the above-mentioned adhesives has high bonding strength, good compatibility with the conductive agent, and ideal chemical and thermal stability, so it can ensure that the conductive agent dispersed in it can fully exert its conductive effect.
  • the conductive agent used in this application can be selected from the conductive agents commonly used in secondary batteries.
  • the conductive agent includes acetylene black (AB), carbon fiber, conductive carbon black, conductive graphite, and single-wall carbon. Any one or more of the group consisting of nanotubes, multi-walled carbon nanotubes, graphene nanosheets, graphene oxide nanosheets and micron graphite.
  • AB acetylene black
  • carbon fiber conductive carbon black
  • conductive graphite conductive graphite
  • single-wall carbon any one or more of the group consisting of nanotubes, multi-walled carbon nanotubes, graphene nanosheets, graphene oxide nanosheets and micron graphite.
  • Each of the above-mentioned conductive agents is a conductive agent with high conductivity commonly used in this field. On the basis of the above dosage, it is ensured that the conductive coating has good conductivity.
  • the thickness of the conductive coating is 0.5 microns to 5 microns.
  • the thickness of the conductive coating can be in the range of any two of the following values: 0.5 microns, 0.8 microns, 1.0 microns, 1.5 microns, 1.8 microns, 2.0 microns, 2.2 microns, 2.5 microns, 3.0 microns, 3.5 microns, 4.0 microns, 4.5 micron or 5.0 micron.
  • the thickness of the conductive coating is 0.8 microns to 3 microns.
  • the conductive coating with the above thickness range on the basis of effective bonding between the conductive coating and the current collector, can effectively alleviate the damage of the positive electrode active particles to the oxide layer on the surface of the aluminum foil during the cold pressing process.
  • an effective electron conduction channel can be constructed to ensure that the secondary battery with the positive electrode plate has a sufficiently high volume energy density.
  • the corresponding adhesive is a conductive adhesive and the volume resistivity of the conductive adhesive is ⁇ 10 -3 ⁇ cm.
  • the optional thickness of the conductive coating is 2.2 microns to 3 microns; in some cases In the technical solution corresponding to the embodiment in which the adhesive is an insulating adhesive and the volume resistivity of the insulating adhesive is ⁇ 10 10 ⁇ cm, the optional thickness of the conductive coating is 1.2 microns to 1.8 microns.
  • the current collector has two surfaces opposite in its own thickness direction, and the conductive coating 12 and the positive active layer 13 are sequentially disposed on any one or both of the two opposite surfaces of the positive current collector.
  • the current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the above-mentioned current collector is aluminum foil.
  • the thickness of the current collector is 8 microns to 20 microns (such as 8 microns, 9 microns, 10 microns, 12 microns, 14 microns, 16 microns, 18 microns or 20 microns). micron).
  • the longitudinal and transverse tensile strength of the current collector is ⁇ 175MPa. To provide better mechanical strength and better meet the long-term cycle use of secondary batteries.
  • the transverse tensile strength of the current collector in this application can be tested using methods known in the art. As an example, the following method can be used for testing: take a length of 50mm, a width of 20mm, and a thickness of aluminum foil of 15 ⁇ m. Fix both ends of the sample to be tested in the length direction or width direction on the fixture of the Instron 3365 high-speed rail tensile machine. , pull at a speed of 10mm/min until the sample to be tested is broken to complete the test. According to the instrument’s own software, the tensile force value F (N) in the width direction is obtained.
  • the cathode active material of the present application is at least one of a lithium manganate cathode material, a ternary cathode material, and a quaternary cathode material.
  • the cathode active material includes at least one of formulas (I) to (III):
  • M1 is Mn and/or Al
  • M2 is selected from any one or more of the group consisting of Mg, Cu, Zn, Al, Sn, B, Ga, Zr, Cr, Sr, V and Ti. species, 0.8 ⁇ a1 ⁇ 1.2, 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 1, 0 ⁇ z1 ⁇ 1, x1+y1+z1 ⁇ 1, -0.2 ⁇ b1 ⁇ 0.2.
  • M3 is selected from Mg, Cu, Zn, Al, Sn, B, Ga, Zr, Cr, Sr, V and Any one or more of the group consisting of Ti.
  • 0 ⁇ c ⁇ 1, 0 ⁇ x3 ⁇ 1, 0.8 ⁇ a3 ⁇ 1.2, -0.2 ⁇ b3 ⁇ 0.2, M4 is selected from any one of Ni, Co, Mn, and Mg, Cu, Any one or more of the group consisting of Zn, Al, Sn, B, Ga, Zr, Cr, Sr, V and Ti.
  • Each of the above cathode active materials is mainly selected from the group consisting of lithium manganate cathode materials, ternary cathode materials, and quaternary cathode materials.
  • the lithium manganate cathode material represented by formula (II) is a doped lithium manganate cathode material. , so on the basis of ensuring high rate, the dissolution of manganese is relatively reduced, thus ensuring high cycle performance.
  • a second aspect of the present application provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • the positive electrode sheet is any positive electrode sheet of the first aspect.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery normally includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions such as lithium ions
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the electrolyte is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.
  • the conductive coating of the positive electrode piece of the present application alleviates the damage of the positive electrode active particles to the oxide layer on the surface of the aluminum foil during the cold pressing process, it also improves the breaking tensile strength of the electrode piece, effectively avoiding the problem of the electrode piece being broken due to oxidation. And by controlling the amount of conductive agent and binder, it not only ensures the stability of electronic conduction between the current collector and the cathode active material, but also enhances the peeling strength between the current collector and the conductive coating, thereby effectively solving the problem. The problem of decoating of the positive electrode active layer is eliminated, and at the same time, the cycle performance and cycle stability of the secondary battery with the positive electrode sheet are effectively improved.
  • the above-mentioned electrolyte includes a lithium salt
  • the lithium salt includes lithium fluorine-containing sulfonyl imide and lithium hexafluorophosphate.
  • the lithium fluorine-containing sulfonyl imide is lithium bisfluorosulfonyl imide, Lithium bis(trifluoromethyl)fluorosulfonyl imide, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, lithium (fluorosulfonyl)(pentafluoroethylsulfonyl)imide, (trifluoroethylsulfonyl)imide A group consisting of lithium fluoromethylsulfonyl)(difluoromethylsulfonyl)imide, lithium (fluoromethylsulfonyl)(perfluorobutylsulfonyl)imide
  • lithium hexafluorophosphate (LiPF 6 ) undergoes oxidation and decomposition at the anode, and the oxidation product aluminum trifluoride is deposited on the surface of the current collector, which alleviates the corrosion of aluminum foil by fluorine-containing lithium sulfonyl imide to a certain extent; fluorine-containing sulfonyl Lithium imide has a high degree of dissociation in non-aqueous organic solvents, the conductivity of the electrolyte is high, and this type of lithium salt has good thermal stability and fewer side reactions at high temperatures, so electrolysis containing this type of lithium salt is Liquid secondary batteries have better high-temperature cycle performance.
  • the total concentration of lithium salt in the electrolyte is 0.6 mol/L ⁇ 2 mol/L (such as 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 1.0 mol/L, 1.2mol/L, 1.5mol/L, 1.8mol/L or 2.0mol/L).
  • the concentration C1 of lithium hexafluorophosphate in the electrolyte is 0.1 mol/L to 1 mol/L (for example, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L or 1mol/L), the concentration C2 of lithium fluorosulfonimide is 0.5mol/L ⁇ 1.5mol/L (for example, 0.5mol/L L, 0.7mol/L, 0.8mol/L, 1.0mol/L, 1.2mol/L, 1.4mol/L or 1.5mol/L), further optionally, 1 ⁇ C2/C1 ⁇ 5 (such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5).
  • 1 ⁇ C2/C1 ⁇ 5 such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5
  • fluorine-containing lithium sulfonyl imide can fully improve the conductivity of the electrolyte; further controlling the concentration ratio of the two within the above range, fluorine-containing lithium sulfonyl imide can be used to improve the conductivity of the electrolyte. property, and can make full use of lithium hexafluorophosphate and the conductive coating to alleviate the corrosion of fluorinated sulfonylimide lithium on the current collector, thereby further improving the high-temperature cycle performance of the secondary battery.
  • the thickness d of the conductive coating of the positive electrode piece, the concentration C1 of lithium hexafluorophosphate, and the concentration C2 of fluorine-containing lithium sulfonyl imide satisfy the relationship: C2/(5 ⁇ C1) ⁇ d ⁇ lg(C2/C1)+4, where the units of C1 and C2 are mol/L, and the unit of d is ⁇ m.
  • the above-mentioned electrolyte further includes an organic solvent and additives.
  • the organic solvent is selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, and methylpropyl carbonate.
  • the mass content of the organic solvent in the electrolyte is 65% to 85%. Typical but not limiting, the above mass content is 65%, 70%, 75%, 80% or 85%.
  • the above-mentioned additive is selected from the group consisting of vinylene carbonate, vinyl sulfate, lithium difluoroxaloborate, lithium difluorophosphate, lithium tetrafluoroborate, 1,3-propanesultone, trifluoroborate. At least one of the group consisting of lithium fluoromethanesulfonate and lithium diacetate borate.
  • 1,3-propanesultone can be oxidized in the positive electrode in advance to alleviate the oxidation of fluorinated sulfonylimide lithium at high voltage. Generate gas, thereby better alleviating the corrosion of fluorinated sulfonylimide lithium on the current collector.
  • the total mass content of the above additives in the electrolyte is 0.5% to 7% (such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6% or 7%). In order to give full play to the role of the corresponding additives, it does not affect the performance of the above-mentioned lithium salts.
  • the negative electrode sheet may include a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector and including a negative electrode active material.
  • the negative electrode material layer may be disposed on one surface of the negative electrode current collector, or may disposed on both surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: graphite (such as artificial graphite, natural graphite), soft carbon, hard carbon, mesophase carbon microspheres, carbon fiber, carbon nanotubes, silicon-based materials, tin-based Materials and lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative active material of the above-mentioned negative electrode includes natural graphite, artificial graphite, mesophase microcarbon, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn Any one or more of the group consisting of -O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 and Li-Al alloy.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode material layer includes the negative electrode active material artificial graphite, the conductive agent acetylene black, and the binder styrene-butadiene rubber (SBR).
  • SBR styrene-butadiene rubber
  • the negative electrode material layer optionally also includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • auxiliaries such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the isolation film is arranged between the positive electrode sheet and the negative electrode sheet to play the role of isolation.
  • the type of the isolation membrane is not specifically limited, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the secondary battery of the present application may be a lithium ion battery.
  • the secondary battery of the present application can be prepared using conventional methods.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • Exemplary preparation methods include:
  • Step 1 Stack the positive electrode piece, isolation film, and negative electrode piece in order so that the isolation film is between the positive and negative electrode pieces, and then wind it to obtain the electrode assembly;
  • Step 2 Place the electrode assembly in the secondary battery case, dry it, inject the electrolyte, and then go through the formation and standing processes to prepare the secondary battery.
  • the secondary battery of the present application may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 2 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • this application also provides an electrical device, which includes the secondary battery, battery module or battery pack provided by this application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device can be selected from mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf balls). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 7 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the positive electrode sheet of the present application is corrosion-resistant and the positive active layer adheres stably to the current collector, the secondary batteries, battery modules, battery packs and electrical devices equipped with it have good high-temperature stability and good cycle performance. The advantages.
  • Table 1 below describes the sources and properties of some materials used in the examples.
  • the ratios of solvents and additives used are shown in Table 2, where the ratios of solvents and additives in Table 2 are mass percentages calculated based on the total mass of the electrolyte.
  • the solvents are ethylene carbonate:ethyl methyl carbonate (3:7wt%/wt%)
  • the additives are vinylene carbonate
  • the additive mass content is 2%.
  • an aqueous solution containing a conductive agent and a binder is coated on an aluminum foil substrate (15 ⁇ m aluminum foil, transverse tensile strength of 180 MPa), and then dried in an oven at 85°C to form a corresponding conductive coating on the aluminum foil substrate. layer, spare.
  • the electrolyte components in Examples 6-33 and Comparative Examples 1 to 5 in Table 3 are consistent with Example 3.
  • compositions of the conductive coatings of each example and comparative example are recorded in Table 3.
  • the positive electrode active material, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the solid content in the positive electrode slurry is 50wt%, and the mass ratio of the positive electrode active material, Super P, and PVDF in the solid content is 8:1:1.
  • the cathode active material of Examples 1 to 33 is Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2
  • the cathode active material of Example 34 is Li[Ni 0.5 Co 0.2 Mn 0.3 ]O 2
  • the cathode active material of Example 35 is It is Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 .
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were prepared in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the solid content in the positive electrode slurry is 50wt%, and the mass ratio of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , Super P, and PVDF in the solid content is 8:1:1.
  • PE polyethylene film
  • the following method can be used to test: fix one side of the positive electrode sheet that has been cycled 500 times on a steel plate (double-sided tape can be used), and gently tear off the diaphragm, so that about 2cm of the diaphragm is peeled off from the base material.
  • a steel plate double-sided tape can be used
  • the peeled diaphragm is fixed on the clamp on the upper end of the tensile machine.
  • the Instron 3365 high-speed rail tensile machine is used to pull the high-speed rail tensile machine at a speed of 60mm/min.
  • the diaphragm slowly moves from The base material is peeled off, and the computer displays the pulling force value when the pulling force is stable, which is the peeling strength value of the diaphragm.
  • the primer layer and the active material layer are integrated and peeled off from the base material.
  • Example 27 Comparison of the results of Example 27 and other examples shows that when the binder/conductive agent in the primer meets the above range, and the thickness of the primer satisfies C2/(5 ⁇ C1) ⁇ d ⁇ lg(C2/C1)+ 4. You can get a battery with better performance.

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Abstract

本申请提供了一种正极极片、二次电池、电池模块、电池包和用电装置。该正极极片包括：集流体、导电涂层和正极活性层，导电涂层设置在集流体的至少一侧表面上，导电涂层包括质量含量为20％～50％的导电剂和质量含量为50％～80％的粘结剂；正极活性层设置在导电涂层的远离集流体的表面上，正极活性层中的正极活性材料为锰酸锂系正极材料、三元正极材料、四元正极材料中的至少一种。利用导电涂层有效避免了氧化导致的极片断带的问题，且通过对导电剂和粘结剂的用量控制，既保证了集流体和正极活性材料之间的电子传导的稳定性，且增强了集流体和导电涂层之间的剥离强度，有效提升了具有该正极极片的二次电池的循环性能和循环稳定性。

Description

正极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池技术领域，特别是涉及一种正极极片、二次电池、电池模块、电池包和用电装置。
背景技术
目前锂离子电池的应用已经深入到日常生活中的方方面面例如相机、笔记本电脑、电动汽车等。并且随着锂离子电池技术的极大发展，人们对其安全性能以及电池循环性能、使用寿命等也提出了更高的要求。尤其，在电动汽车领域，如何保证锂离子电池兼具较高的安全性能同时具有较长的循环性能、使用寿命，已成为一项亟需解决的技术问题。
发明内容
本申请提供了一种正极极片、二次电池、电池模块、电池包和用电装置。以解决现有技术中在正极集流体上设置的导电涂层导致正极活性材料层容易脱膜的问题。
本申请的第一方面提供了一种正极极片，包括：集流体、导电涂层和正极活性层，导电涂层设置在集流体的至少一侧表面上，导电涂层包括质量含量为20％～50％的导电剂和质量含量为50％～80％的粘结剂；正极活性层设置在导电涂层的远离集流体的表面上，正极活性层中的正极活性材料为锰酸锂系正极材料、三元正极材料、四元正极材料中的至少一种。
本申请正极极片的导电涂层缓解了冷压过程中正极活性颗粒对铝箔表面氧化层的破坏，同时提高极片断裂拉伸强度，有效避免了氧化导致的极片断带的问题。其中在利用导电剂起到集流体与正极活性材料之间的电子传导的基础上，通过对导电剂和粘结剂的用量控制，既保证了集流体和正极活性材料之间的电子传导的稳定性，且增强了集流体和导电涂层之间的剥离强度，进而有效地解决了正极活性层脱膜的问题，同时有效提升了具有该正极极片的二次电池的循环性能和循环稳定性。
在本申请任意实施方式中，上述粘结剂为导电粘结剂，导电粘结剂的体积电阻率≤10 -3Ω·cm；可选地，导电涂层包括质量含量为20％～30％的导电剂和质量含量为70％～80％的导电粘结剂。在上述实施方式中，采用导电粘结剂作为粘结剂，在保证相同电子传导能力的基础上，可以进一步减少导电剂的用量，进而相对地增加了粘结剂的用量，实现进一步改善集流体和导电涂层之间剥离强度的目的。
在任意实施方式中，上述导电粘结剂选自环氧树脂导电胶、有机硅树脂导电胶、聚酰亚胺树脂导电胶、酚醛树脂导电胶、聚氨酯导电胶组成的组中的任意一种或多种。上述各导电粘结剂的化学稳定性、热稳定性较高，因此满足二次电池的长周期循环使用。
在任意实施方式中，上述粘结剂为绝缘粘结剂，绝缘粘结剂的体积电阻率≥10 10Ω·cm；可选地，导电涂层包括质量含量为30％～45％的导电剂和质量含量为55％～70％的绝缘粘结剂。在该实施方式中，采用的粘结剂为绝缘材料，因此其中所需的导电剂相应增多，上述质量含量保证了对导电涂层的电子传导效果和粘结效果的同时优化。
在任意实施方式中，进一步可选地，上述绝缘粘结剂选自PVDF、聚丙烯腈、丁苯橡胶、聚乙烯醇、阿拉伯胶、黄原胶、聚丙烯酸酯组成的组中的任意一种或多种。上述各粘结剂的粘结强度较高、与导电剂的相容性较好、化学稳定性和热稳定性也较为理想，因此满足二次电池的长周期循环使用。
在任意实施方式中，上述导电剂包含选自乙炔黑(AB)、碳纤维、导电炭黑、导电石墨、单壁碳纳米管、多壁碳纳米管、石墨烯纳米片、氧化石墨烯纳米片和微粉石墨组成的组中任意一种或多种。上述各导电剂均为本领域常用的导电性较高的导电剂，在上述用量的基础上，保证了导电涂层具有较好的导电性。
在任意实施方式中，上述导电涂层的厚度为0.5微米～5微米，可选地，导电涂层的厚度为0.8微米～3微米。具有上述厚度范围内的导电涂层，在起到对导电涂层和集流体之间的有效的粘结的基础上，既可以有效缓解冷压过程中正极活性颗粒对铝箔表面氧化层的破坏，又可以构建有效的电子传导通道并保证具有该正极极片的二次电池具有足够高的体积能量密度。
在任意实施方式中，上述集流体为铝箔，可选地，铝箔的厚度为8微米～20微米；和/或，所述集流体在纵向、横向的拉伸强度≥175MPa。以提供更好的机械强度，更好地满足二次电池的长时间循环使用。
在任意实施方式中，正极活性材料包括式(I)～(III)中的至少一种：
Li a1Ni x1Co y1M1 z1M2 1-x1-y1-z1O 2-b1   式(I)
Li a2Mn 2-y2M3 y2O 4-b2   式(II)
cLi 2MnO 3·(1-c)Lia 3M4 x3O 2-b3   式(III)
式(I)中，M1为Mn和/或Al，M2选自Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种，0.8≤a1＜1.2，0≤x1＜1，0≤y1≤1，0≤z1≤1，x1+y1+z1≤1，-0.2≤b1≤0.2。式(II)中，0.8≤a2＜1.2，0.6≤y2≤1，-0.2≤b2≤0.2，M3选自Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种。式(III)中，0<c<1，0＜x3＜1，0.8<a3<1.2，-0.2≤b3≤ 0.2，M4选自Ni、Co、Mn中的任意一种，以及Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种。上述各正极活性材料主要选自锰酸锂系正极材料、三元正极材料、四元正极材料，其中式(II)示出的锰酸锂系正极材料为掺杂的锰酸锂系正极材料，因此在保证高倍率的基础上，锰的溶出相对降低进而保证了较高的循环性能。
本申请的第二方面提供了一种二次电池，包括正极极片、负极极片、电解液和隔膜，该正极极片为第一方面的任意一种正极极片。由于本申请的正极极片的导电涂层缓解了冷压过程中正极活性颗粒对铝箔表面氧化层的破坏，同时提高极片断裂拉伸强度，有效避免了氧化导致的极片断带的问题。且通过对导电剂和粘结剂的用量控制，既保证了集流体和正极活性材料之间的电子传导的稳定性，且增强了集流体和导电涂层之间的剥离强度，进而有效地解决了正极活性层脱膜的问题，同时有效提升了具有该正极极片的二次电池的循环性能和循环稳定性。
在第二方面的任意实施方式中，上述电解液包括锂盐，锂盐包括含氟磺酰亚胺锂和六氟磷酸锂。可选地，含氟磺酰亚胺锂为双氟磺酰亚胺锂、双(三氟甲基)氟磺酰亚胺锂、(氟磺酰)(三氟甲基磺酰)亚胺锂、(氟磺酰)(五氟乙基磺酰)亚胺锂、(三氟甲基磺酰)(二氟甲基磺酰)亚胺锂、(氟磺酰)(全氟丁基磺酰)亚胺锂、双(五氟乙基磺酰)亚胺锂组成的组中的任意一种或多种。上述的含氟磺酰亚胺锂应用与电解液中，提高了具有该电解液的二次电池的高温安全性能。
在第二方面的任意实施方式中，可选地，电解液中锂盐的总浓度为0.6mol/L～2mol/L。可选地，电解液中，六氟磷酸锂的浓度C1为0.1mol/L～1mol/L，含氟磺酰亚胺锂的浓度C2为0.5mol/L～1.5mol/L。可选地，1≤C2/C1≤5。在上述浓度范围内，含氟磺酰亚胺锂可以充分提升电解液的导电性。进一步将二者的浓度比例控制在上述范围内，一方面可以利用含氟磺酰亚胺锂提高电解液的导电性；同时，还可以利用六氟磷酸锂在首次充放电过程中在正极集流体上氧化形成三氟化铝薄膜，进而与导电涂层一起起到缓解含氟磺酰亚胺锂对集流体的腐蚀的效果，从而进一步提高二次电池的高温循环性能。
在第二方面的任意实施方式中，上述正极极片的导电涂层的厚度d、六氟磷酸锂的浓度C1与含氟磺酰亚胺锂的浓度C2满足关系式：C2/(5×C1)≤d≤lg(C2/C1)+4，其中，C1、C2的单位为mol/L，d的单位为μm。通过上述关系式对导电涂层厚度、六氟磷酸锂浓度、含氟磺酰亚胺锂浓度的控制，在三者的共同作用下，实现了对二次电池的高温循环性能、能量密度以及耐腐蚀性能的更好地共同提升。
在第二方面的任意实施方式中，上述电解液还包括有机溶剂和添加剂，有机溶剂选自碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯，碳酸亚乙酯、碳酸亚丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸乙丙酯、γ-丁内酯、甲酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸甲酯和四氢呋喃组成的组中的任意一种或多种；上述有机溶剂均为本领域的常用的有机溶剂，锂盐在其中的 分散性能较好。
在第二方面的任意实施方式中，有机溶剂在电解液中的质量含量为65％～85％。
在第二方面的任意实施方式中，上述添加剂选自碳酸亚乙烯酯、硫酸乙烯酯、二氟草酸硼酸锂、二氟磷酸锂、四氟硼酸锂、1,3-丙磺酸内酯、三氟甲基磺酸锂、和双乙酸硼酸锂组成的组中至少一种。本领域技术人员可以根据对二次电池的特定性能需求选择添加上述添加剂，比如其中的1,3-丙磺酸内酯可以提前在正极氧化缓解含氟磺酰亚胺锂在高电压下的氧化产气，进而更好地缓解含氟磺酰亚胺锂对集流体的腐蚀。
在第二方面的任意实施方式中，上述添加剂在电解液中的总质量含量为0.5％～7％。以充分发挥相应添加剂的作用，并不影响上述锂盐作用的发挥。
在第二方面的任意实施方式中，上述负极的负极活性材料包括天然石墨、人造石墨、中间相微碳、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12和Li-Al合金组成的组中的任意一种或多种。上述负极均为本领域二次电极中的常用负极，本领域技术人员可以根据对二次电池的性能要求从上述种类中选择合适的负极材料。
本申请的第三方面提供了一种电池模块，包括二次电池，该二次电池为第二方面的任意一种二次电池。
本申请的第四方面提供了一种电池包，包括电池模块，该电池模块为第三方面的任意一种电池模块。
本申请的第五方面提供了一种用电装置，包括二次电池或电池模块或电池包，其中的二次电池为第二方面的任意一种二次电池，电池模块为第三方面的任意一种电池模块，电池包为第四方面的任意一种电池包。
由于本申请的正极极片具有耐腐蚀、正极活性层在集流体上粘附稳定，因此，使具有其的二次电池、电池模块、电池包和用电装置具有高温稳定性好、循环性能好的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请一实施方式的正极极片的侧视图。
图2是本申请一实施方式的二次电池的示意图。
图3是图2所示的本申请一实施方式的二次电池的分解图。
图4是本申请一实施方式的电池模块的示意图。
图5是本申请一实施方式的电池包的示意图。
图6是图5所示的本申请一实施方式的电池包的分解图。
图7是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
11集流体；12导电涂层；13正极活性层；1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
在附图中，附图并未按照实际的比例绘制。
具体实施方式
下面结合附图和实施例对本申请的实施方式作进一步详细描述。以下实施例的详细描述和附图用于示例性地说明本申请的原理，但不能用来限制本申请的范围，即本申请不限于所描述的实施例。
以下，适当地参照附图详细说明具体公开了本申请的正极极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
锂离子电池的安全性能是最低的保障，提高锂离子电池使用的安全性一直是研究者不懈的追求，就电解液角度而言，含氟磺酰亚胺锂具有较高的热分解温度，对水不敏感，在一定程度上可以提高电池的安全性能。但是电解液含有此类锂盐时，会出现腐蚀铝箔的风险，可能会导致极片断带，严重威胁到二次电池的安全性能和使用寿命。
具体地，正极基材目前通常是铝箔，铝箔在空气中放置表面会被氧化，形成一层均匀的氧化薄膜，在进行活性材料冷压过程中，活性材料颗粒会部分压进铝箔中，破坏此处的氧化膜。当电解液中含有含氟磺酰亚胺锂盐时，该锂盐在正极发生氧化，氧化产物与铝结合，结合产物进一步溶解到电解液中，出现腐蚀坑，可能会导致极片断带，严重威胁到二次电池的安全性能和使用寿命。
公开号为CN 13851724 A的专利申请公开了一种将含氟磺酰亚胺锂盐和导电涂层相配合，通过导电涂层的引入降低了集流体与活性材料之间的接触电阻，同时还能够在一定程度上减少含氟磺酰亚胺锂盐与集流体接触而导致的腐蚀风险，既可以提高电化学装置的大倍率循环性能和降低电化学装置的温升，又能够减缓含氟磺酰亚胺锂盐对正极集流体的腐蚀影响，提升电化学装置的长期稳定性。
但是，导电涂层容易导致正极活性材料层从集流体上的脱落，进而影响锂离子电池的循环性能。
如前文所描述的，虽然导电涂层能够减缓含氟磺酰亚胺锂盐对正极集流体的腐蚀影响，提升电化学装置的长期稳定性。但是，在实际应用中，导电涂层容易导致正极活性材料层从集流体上的脱落，进而影响锂离子电池的循环性能。为了解决该问题，本申请提供了一种正极极片、二次电池、电池模块、电池包和用电装置。
[正极极片]
本申请的第一方面提供了一种正极极片，如图1所示，该正极极片包括：集流体11、导电涂层12和正极活性层13，导电涂层12设置在集流体11的至少一侧表面上，导电涂层12包括质量含量为20％～50％的导电剂和质量含量为50％～80％的粘结剂；正极活性层13设置在导电涂层12的远离集流体11的表面上，正极活性层13中的正极活性材料为锰酸锂系正极材料、三元正极材料、四元正极材料中的至少一种。
本申请中，锰酸锂系正极材料指的是具有尖晶石结构、经掺杂或未掺杂的LiMn 2O 4正极材料。三元正极材料指的是具有层状结构、且过渡金属位至少含有Ni、Co、Mn或Ni、Co、Al三种元素的锂过渡金属氧化物。四元正极材料指的是具有层状结构、且过渡金属位至少含有Ni、Co、Mn、Al四种元素的锂过渡金属氧化物。
本申请正极极片的导电涂层12缓解了冷压过程中正极活性颗粒对集流体表面氧化层的破坏，同时提高极片断裂拉伸强度，有效避免了氧化导致的极片断带的问题。其中在利用导电剂起到集流体与正极活性材料之间的电子传导的基础上，通过对导电剂和粘结剂的用量控制，既保证了集流体和正极活性材料之间的电子传导的稳定性，且增强了集流体11和导电涂层12之间的剥离强度，进而有效地解决了正极活性层13脱膜的问题，同时有效提升了具有该正极极片的二次电池的循环性能和循环稳定性。
上述导电涂层中的导电剂的质量含量和粘结剂的质量含量可以为上述范围的中任意数值，比如导电剂的质量含量可以为20％、25％、30％、35％、40％、45％或50％；粘结剂的质量含量可以为50％、55％、60％、65％、70％、75％或80％。
如前所述，本申请的导电涂层既要提供充分的导电能力，又必须满足增强对正极活性层的粘结能力。在此基础上，本申请发明人在调整导电剂和粘结剂的配比基础上，发现当粘结剂的体积电阻率具有明显差异时，二者的比例可以进一步调整，以实现对导电能力和粘结能力的进一步提升。
在上述第一方面的任意实施方式中，上述粘结剂为导电粘结剂，导电粘结剂的体积电阻率≤10 -3Ω·cm；可选地，导电涂层包括质量含量为20％～30％的导电剂和质量含量为70％～80％的导电粘结剂。在上述实施方式中，采用导电粘结剂作为粘结剂，在保证相同电子传导能力的基础上，可以进一步减少导电剂的用量，进而相对地增加了粘结剂的用量，实现进一步改善集流体和导电涂层之间剥离强度的目的。
用于本身去的导电粘结剂可以从现有技术中常用的具有导电性能的粘结剂中进行选择，考虑到导电剂在其中的分散性越好导电能力越强，因此为进一步保证导电剂导电作用的充分发挥，在一些实施方式中，上述导电粘结剂选自环氧树脂导电胶、有机硅树脂导电胶、聚酰亚胺树脂导电胶、酚醛树脂导电胶、聚氨酯导电胶组成的组中的任意一种或多种。上述各导电粘结剂的化学稳定性、热稳定性较高；而且对无机的导电剂具有较高的分散性，因此保证了导电剂的均匀分散，满足二次电池的长周期、 高性能循环使用。
在一些实施方式中，上述粘结剂为绝缘粘结剂，绝缘粘结剂的体积电阻率≥10 10Ω·cm；可选地，导电涂层包括质量含量为30％～45％的导电剂和质量含量为55％～70％的绝缘粘结剂。在该实施方式中，采用的粘结剂体积电阻率较高，因此其中所需的导电剂相应增多，上述质量含量保证了对导电涂层的电子传导效果和粘结效果的同时优化。
当粘结剂的体积电阻率较高时，除了增加导电剂用量之外，在一些实施方式中，进一步可选地，上述绝缘粘结剂选自PVDF、聚丙烯腈、丁苯橡胶、聚乙烯醇、阿拉伯胶、黄原胶、聚丙烯酸酯组成的组中的任意一种或多种。上述各粘结剂的粘结强度较高、与导电剂的相容性较好、化学稳定性和热稳定性也较为理想，因此可以保证分散在其中的导电剂的导电作用充分发挥。
用于本申请的导电剂可以从二次电池常用的导电剂中进行选择，在一些实施方式中，上述导电剂包含选自乙炔黑(AB)、碳纤维、导电炭黑、导电石墨、单壁碳纳米管、多壁碳纳米管、石墨烯纳米片、氧化石墨烯纳米片和微粉石墨组成的组中任意一种或多种。上述各导电剂均为本领域常用的导电性较高的导电剂，在上述用量的基础上，保证了导电涂层具有较好的导电性。
在一些实施方式中，上述导电涂层的厚度为0.5微米～5微米。导电涂层的厚度可以为以下任意二个数值组成的范围：0.5微米、0.8微米、1.0微米、1.5微米、1.8微米、2.0微米、2.2微米、2.5微米、3.0微米、3.5微米、4.0微米、4.5微米或5.0微米。可选地，导电涂层的厚度为0.8微米～3微米。具有上述厚度范围内的导电涂层，在起到对导电涂层和集流体之间的有效的粘结的基础上，既可以有效缓解冷压过程中正极活性颗粒对铝箔表面氧化层的破坏，又可以构建有效的电子传导通道并保证具有该正极极片的二次电池具有足够高的体积能量密度。在一些实施方式对应粘结剂为导电粘结剂、导电粘结剂的体积电阻率≤10 -3Ω·cm的方案中，可选地导电涂层的厚度为2.2微米～3微米；在一些实施方式对应粘结剂为绝缘粘结剂、绝缘粘结剂的体积电阻率≥10 10Ω·cm的技术方案中，可选地导电涂层的厚度为1.2微米～1.8微米。
作为示例，集流体具有在其自身厚度方向相对的两个表面，导电涂层12和正极活性层13依次设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。进一步可选地，上述集流体为铝箔，可选地，集流体的厚度为8微米～20微米(比如为8微米、9微米、10微米、12微米、14微米、16微米、18微米或20微米)。可选地，集流体的纵向、横向的拉伸强度≥175MPa。以提供更好的机 械强度，更好地满足二次电池的长时间循环使用。
本申请中集流体的横向拉伸强度可以采用本领域公知的测试方法。作为示例的，可以采用如下方法进行测试：取长度50mm、宽度为20mm，铝箔的厚度为15μm将待测样品的长度方向或宽度方向的两端固定在英斯特朗3365高铁拉力机的夹具上，以10mm/min的速度拉动，直到待测样品被拉断完成测试，根据仪器自带软件得到宽度方向拉力值F(N)，横向拉伸强度可通过R＝F/(铝箔的宽度×铝箔的厚度)，横向拉伸强度可通过R＝F/(铝箔的宽度×铝箔的厚度)。
本申请的正极活性材料为锰酸锂系正极材料、三元正极材料、四元正极材料中的至少一种。在一些实施方式中，正极活性材料包括式(I)～(III)中的至少一种：
Li a1Ni x1Co y1M1 z1M2 1-x1-y1-z1O 2-b1   式(I)
Li a2Mn 2-y2M3 y2O 4-b2   式(II)
cLi 2MnO 3·(1-c)Lia 3M4 x3O 2-b3   式(III)
式(I)中，M1为Mn和/或Al，M2选自Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种，0.8≤a1＜1.2，0≤x1＜1，0≤y1≤1，0≤z1≤1，x1+y1+z1≤1，-0.2≤b1≤0.2。式(II)中，0.8≤a2＜1.2，0.6≤y2≤1，-0.2≤b2≤0.2，M3选自Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种。式(III)中，0<c<1，0＜x3＜1，0.8<a3<1.2，-0.2≤b3≤0.2，M4选自Ni、Co、Mn中的任意一种，以及Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种。上述各正极活性材料主要选自锰酸锂系正极材料、三元正极材料、四元正极材料，其中的式(II)示出的锰酸锂系正极材料为掺杂的锰酸锂系正极材料，因此在保证高倍率的基础上，锰的溶出相对降低进而保证了较高的循环性能。
本申请的第二方面提供了一种二次电池，包括正极极片、负极极片、电解液和隔膜，该正极极片为第一方面的任意一种正极极片。
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
由于本申请的正极极片的导电涂层缓解了冷压过程中正极活性颗粒对铝箔表面氧化层的破坏，同时提高极片断裂拉伸强度，有效避免了氧化导致的极片断带的问题。且通过对导电剂和粘结剂的用量控制，既保证了集流体和正极活性材料之间的电 子传导的稳定性，且增强了集流体和导电涂层之间的剥离强度，进而有效地解决了正极活性层脱膜的问题，同时有效提升了具有该正极极片的二次电池的循环性能和循环稳定性。
在第二方面的一些实施方式中，上述电解液包括锂盐，锂盐包括含氟磺酰亚胺锂和六氟磷酸锂，可选地，含氟磺酰亚胺锂为双氟磺酰亚胺锂、双(三氟甲基)氟磺酰亚胺锂、(氟磺酰)(三氟甲基磺酰)亚胺锂、(氟磺酰)(五氟乙基磺酰)亚胺锂、(三氟甲基磺酰)(二氟甲基磺酰)亚胺锂、(氟磺酰)(全氟丁基磺酰)亚胺锂、双(五氟乙基磺酰)亚胺锂组成的组中的任意一种或多种。在首次充放电过程中，六氟磷酸锂(LiPF 6)在阳极发生氧化分解，氧化产物三氟化铝沉积在集流体表面，在一定程度上缓解含氟磺酰亚胺锂对铝箔的腐蚀；含氟磺酰亚胺锂在非水有机溶剂中解离度较高，电解液的电导率较高，并且此类锂盐的热稳定性较好，高温下副反应较少，因此含有此类锂盐电解液的二次电池高温循环性能较优。
在第二方面的任意实施方式中，可选地，电解液中锂盐的总浓度为0.6mol/L～2mol/L(比如为0.6mol/L、0.7mol/L、0.8mol/L、1.0mol/L、1.2mol/L、1.5mol/L、1.8mol/L或2.0mol/L)。可选地，电解液中，六氟磷酸锂的浓度C1为0.1mol/L～1mol/L(比如为0.1mol/L、0.2mol/L、0.3mol/L、0.4mol/L、0.5mol/L、0.6mol/L、0.7mol/L、0.8mol/L、0.9mol/L或1mol/L)，含氟磺酰亚胺锂的浓度C2为0.5mol/L～1.5mol/L(比如为0.5mol/L、0.7mol/L、0.8mol/L、1.0mol/L、1.2mol/L、1.4mol/L或1.5mol/L)，进一步可选地，1≤C2/C1≤5(比如为1、1.5、2、2.5、3、3.5、4、4.5或5)。在上述浓度范围内，含氟磺酰亚胺锂可以充分提升电解液的导电性；进一步将二者的浓度比例控制在上述范围内，既可以利用含氟磺酰亚胺锂提高电解液的导电性，又可以充分利用六氟磷酸锂与导电涂层一起起到缓解含氟磺酰亚胺锂对集流体的腐蚀的效果，从而进一步提高二次电池的高温循环性能。
在第二方面的任意实施方式中，上述正极极片的导电涂层的厚度d、六氟磷酸锂的浓度C1与含氟磺酰亚胺锂的浓度C2满足关系式：C2/(5×C1)≤d≤lg(C2/C1)+4，其中，C1、C2的单位为mol/L，d的单位为μm。通过上述关系式对导电涂层厚度、六氟磷酸锂浓度、含氟磺酰亚胺锂浓度的控制，在三者的共同作用下，实现了对二次电池的高温循环性能、能量密度以及耐腐蚀性能的更好地共同提升。
在第二方面的任意实施方式中，上述电解液还包括有机溶剂和添加剂，有机溶剂选自碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯，碳酸亚乙酯、碳酸亚丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸乙丙酯、γ-丁内酯、甲酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸甲酯和四氢呋喃组成的组中的任意一种或多种；上述有机溶剂均为本领域的常用的有机溶剂，锂盐在其中的分散性能较好。
在第二方面的任意实施方式中，有机溶剂在电解液中的质量含量为65％～85％。典型而非限制的，上述质量含量为65％、70％、75％、80％或85％。
在第二方面的任意实施方式中，上述添加剂选自碳酸亚乙烯酯、硫酸乙烯酯、二氟草酸硼酸锂、二氟磷酸锂、四氟硼酸锂、1,3-丙磺酸内酯、三氟甲基磺酸锂、和双乙酸硼酸锂组成的组中至少一种。本领域技术人员可以根据对二次电池的特定性能需求选择添加上述添加剂，比如其中的1,3-丙磺酸内酯可以提前在正极氧化缓解含氟磺酰亚胺锂在高电压下的氧化产气，进而更好地缓解含氟磺酰亚胺锂对集流体的腐蚀。
在第二方面的任意实施方式中，上述添加剂在电解液中的总质量含量为0.5％～7％(比如为0.5％、1％、2％、3％、4％、5％、6％或7％)。以充分发挥相应添加剂的作用，并不影响上述锂盐作用的发挥。
[负极极片]
本申请的二次电池中，负极极片可包括负极集流体以及设置于负极集流体上且包括负极活性材料的负极材料层，负极材料层可设置在负极集流体的其中一个表面上，也可设置在负极集流体的两个表面上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：石墨(例如人造石墨、天然石墨)、软炭、硬炭、中间相碳微球、碳纤维、碳纳米管、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负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。
在第二方面的一些实施方式中，上述负极的负极活性材料包括天然石墨、人造石墨、中间相微碳、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12和Li-Al合金组成的组中的任意一种或多种。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方案中，负极材料层包含负极活性材料人造石墨、导电剂乙炔黑和粘结剂丁苯橡胶(SBR)。
在一些实施方式中，负极材料层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[隔离膜]
本申请的二次电池中，隔离膜设置在正极片和负极片之间，起到隔离的作用。其中，所述隔离膜的种类并不受到具体的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
本申请的二次电池可以是锂离子电池。
可使用常规方法制备本申请的二次电池。在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。示例性的制备方法包括：
步骤1：将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间，然后卷绕得到电极组件；
步骤2：将电极组件置于二次电池壳体中，干燥后注入电解液，再经过化成、静置工艺制得二次电池。
在一些实施方式中，本申请的二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图2是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图3，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个 或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图4是作为一个示例的电池模块4。参照图4，在电池模块4中，多个二次电池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外壳，多个二次电池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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图5和图6是作为一个示例的电池包1。参照图5和图6，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。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块或电池包。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以选自移动设备(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，但不限于此。作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图7是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池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，可以采用二次电池作为电源。
由于本申请的正极极片具有耐腐蚀、正极活性层在集流体上粘附稳定，因此，使具有其的二次电池、电池模块、电池包和用电装置具有高温稳定性好、循环性能好的优势。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域 内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
以下表1对实施例所用的某些材料的来源、性能进行说明。
表1
名称 厂家和型号 体积电阻率(Ω·cm)
环氧树脂导电胶 东莞市品恒胶业有限公司，PH8011 10 -3～10 -4
有机硅树脂导电胶 汉高粘结剂有限公司，ICP4000 10 -3～10 -4
聚酰亚胺树脂导电胶 深圳市德惠康科技有限公司，CW229 10 -3～10 -4
酚醛树脂导电胶 本诺公司，DAD-3 10 -3～10 -4
聚氨酯导电胶 上海野川化工有限公司，DU294B 10 -3-10 -4
PVDF 上海三爱富PVDF，FR915 5×10 14
聚丙烯腈 麦克林试剂，P823208 6.5×10 13
阿拉伯胶 麦克林试剂，A800707 3×10 12
碳纤维 天津晶林新材料科技有限公司，ECC-N 0.001
多壁碳纳米管 先锋纳米，100238 0.002
石墨烯纳米片 中科言诺，C03041 4×10 -4
导电炭黑 天津优盟科技有限公司，Super P 0.001
(1)电解液的制备
在充满氩气的手套箱中(水含量＜10ppm，氧气含量＜1ppm)，将2％碳酸亚乙烯酯加入到有机溶剂中(EC:EMC＝3:7wt％/wt％)，混合均匀后，向非水有机溶剂中缓慢加入适量的锂盐(LiPF 6、含氟磺酰亚胺锂的具体含量见下表)，待锂盐完全溶解后，得到目标电解液，即为所述电解液。
实施例和对比例中，所用到的溶剂和添加剂比例如表2所示，其中，在表2中溶剂和添加剂的比例是基于电解液的总质量计算所得到的质量百分数，另外，各实施例和对比例的电解液中，如无特殊说明，溶剂均为碳酸乙烯酯：碳酸甲乙酯(3:7wt％/wt％)，添加剂均为碳酸亚乙烯酯，添加剂质量含量为2％。
表2
Figure PCTCN2022090415-appb-000001
(2)正极片的制备(加底涂)：
首先将含有导电剂和粘结剂的水溶液涂布在铝箔基材(15μm的铝箔，横向拉伸强度为180MPa)，随后在85℃的烘箱中烘干以在铝箔基材上形成相应的导电涂层，备用。表3中实施例6-33、对比例1至5中电解液组分与实施例3保持一致。
其中，各实施例和对比例导电涂层的组成记录在表3中。
表3
Figure PCTCN2022090415-appb-000002
Figure PCTCN2022090415-appb-000003
将正极活性材料、导电剂Super P、粘结剂聚偏二氟乙烯(PVDF)在N-甲基吡咯烷酮(NMP)中制成正极浆料。正极浆料中固体含量为50wt％，固体成分中正极活性材料、Super P、PVDF的质量比为8:1:1。将正极浆料涂布在底涂处理后的集流体铝箔上并在85℃下烘干后进行冷压，然后进行切边、裁片、分条后，在85℃的真空条件下烘干4h，制成正极片。其中实施例1至33的正极活性材料为Li[Ni 0.8Co 0.1Mn 0.1]O 2，实施例34的正极活性材料为Li[Ni 0.5Co 0.2Mn 0.3]O 2，实施例35的正极活性材料为Li[Ni 0.6Co 0.2Mn 0.2]O 2。
(2)正极片的制备(不加底涂)：
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、导电剂Super P、粘结剂聚偏二氟乙烯(PVDF)在N-甲基吡咯烷酮(NMP)中制成正极浆料。正极浆料中固体含量为50wt％，固体成分中LiNi 0.8Co 0.1Mn 0.1O 2、Super P、PVDF的质量比为8:1:1。将正极浆料涂布在集流体铝箔上并在85℃下烘干后进行冷压，然后进行切边、裁片、分条后，在85℃的真空条件下烘干4h，制成正极片。
(3)负极片的制备：
将作为负极活性材料的石墨与导电剂Super P、增稠剂CMC、粘接剂丁苯橡胶(SBR)在去离子水中混合均匀，制成负极浆料。负极浆料中固体含量为30wt％，固体成分中石墨、Super P、CMC及粘接剂丁苯橡胶(SBR)的质量比为80:15:3:2。将负极浆料涂布在集流体铜箔(厚度为8μm)上并在85℃下烘干，然后进行冷压、切边、裁片、分条后，在120℃真空条件下烘干12h，制成负极片。
(4)锂离子电池的制备：
以16μm的聚乙烯薄膜(PE)作为隔离膜。将制得的正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正负极片中间起到隔离正负极的作用，卷绕得到裸电芯，焊接极耳，将裸电芯置于外包装中，将上述制备的电解液注入到干燥后的壳体中，封装、静置、化成、整形、容量测试等，完成锂离子电池的制备(软包锂离子电池的厚度4.0mm、宽度60mm、长度140mm)。
接下来说明锂离子电池的测试过程。
(1)锂离子电池循环性能测试
25℃下将锂离子电池以1C恒流充电至4.2V，然后以4.2V恒压充电至电流为0.05C，然后用1C恒流放电至2.8V，此为一个充放电循环。以首次放电的容量为100％，计算锂离子电池循环500次后的容量保持率。锂离子电池循环500次后的容量保持率(％)＝第500次循环的放电容量/首次放电的容量×100％。
(2)锂离子电池的热失控性能测试
环境温度调节为25℃，锂离子电池1C充电到4.2V，随后恒压充电到0.05C，将锂离子电池放到加热炉中，炉子按照10℃/min升温，保温10min，直至锂离子电池出现热失控，流程截至。记录锂离子电池热失控时炉子监控的温度
极片横向拉伸强度测试
作为示例的，可以采用如下方法进行测试：将循环500次后的正极极片(长度50mm、宽度为20mm)的两端固定在英斯特朗3365高铁拉力机的夹具上，以10mm/min的速度拉动，直到待测样品被拉断完成测试，根据仪器自带软件得到长度方向以及宽度方向拉力值F(N)，横向拉伸强度可通过R＝F/(铝箔的宽度×铝箔的厚度)。
极片剥离强度测试
作为示例的，可以采用如下方法测试：将循环500次的正极极片一面固定在钢板上(可采用双面胶)，轻轻撕开膜片，使得约2cm的膜片从基材上剥离开来，钢板一端固定在拉力机夹具上，剥离的膜片固定在拉力机上端的夹子上，采用英斯特朗3365高铁拉力机高铁拉力机以60mm/min的速度拉动，膜片缓缓的从基材才剥离，电脑上显示拉力平稳时的拉力值，即该膜片的剥离强度值。剥离时，底涂层与活性材料层为一个整体，从基材上剥离。
正极极片电阻测试
将初始的正极极片放入元能科技BER2100多功能极片电阻仪测量仪中，上下接触面中等待10s，待电脑显示器出现数据后，进行下一个位置的测试，测试10个不同的位置，取平均值。
(5)45℃容量保持率测试
45℃下将锂离子电池以1C恒流充电至4.2V，然后以4.2V恒压充电至电流为0.05C，然后用1C恒流放电至2.8V，此为一个充放电循环。以首次放电的容量为100％，计算锂离子电池循环200次后的容量保持率。锂离子电池循环200次后的容量保持率(％)＝第200次循环的放电容量/首次放电的容量×100％。
(6)锂离子电池充电温升测试
将锂离子电池置于25℃恒温箱中，静置30分钟，使锂离子电池达到恒温。将达到恒温的锂离子电池以1.0C恒流充电至电压为4.2V，然后以4.2V恒压充电至电流为0.05C。接着以1.0C恒流放电至2.8V，充电过程采用多路测温仪监控，电池表面温升。测试结果记录在表4中。
表4
Figure PCTCN2022090415-appb-000004
Figure PCTCN2022090415-appb-000005
由表4的测试结果可以得知，与对比例1-5相比，实施例1-35测试得到的综合性能得到改善。说明本申请的导电涂层的组成有效保证粘结性和导电性的平衡。对比例1中没有底涂，无法抑制含氟磺酰亚胺锂对铝箔的腐蚀，在使用过程中可能出现极 片断裂，内部短路，因此无论循环性能还是安全性能都最差。对比例2、4中虽然有底涂，但是底涂中粘结剂含量过高，严重影响了底涂的导电性，导致极片阻抗增大，二次电池极化增大，恶化二次电池性能和安全性能。对比例3、5中粘结剂含量过少，无法有效的粘接膜片，在循环过程中，极片粘接力变差，集流体与活性材料的电接触差，造成极大的接触电阻，因此二次电池综合性能也比较差。
另外，实施例27和其余实施例的结果对比，说明当底涂中粘结剂/导电剂满足上述范围，且底涂厚度满足C2/(5×C1)≤d≤lg(C2/C1)+4，可以得到性能较好的电池。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (15)

  1. 一种正极极片，包括：
    集流体；
    导电涂层，所述导电涂层设置在所述集流体的至少一侧表面上，所述导电涂层包括质量含量为20％～50％的导电剂和质量含量为50％～80％的粘结剂；
    正极活性层，所述正极活性层设置在所述导电涂层的远离所述集流体的表面上，所述正极活性层中的正极活性材料为锰酸锂系正极材料、三元正极材料、四元正极材料中的至少一种。
  2. 根据权利要求1所述的正极极片，其中，所述粘结剂为导电粘结剂，所述导电粘结剂的体积电阻率≤10 -3Ω·cm；
    可选地，所述导电涂层包括质量含量为20％～30％的导电剂和质量含量为70％～80％的导电粘结剂；
    进一步可选地，所述导电粘结剂选自环氧树脂导电胶、有机硅树脂导电胶、聚酰亚胺树脂导电胶、酚醛树脂导电胶、聚氨酯导电胶组成的组中的任意一种或多种。
  3. 根据权利要求1所述的正极极片，其中，所述粘结剂为绝缘粘结剂，所述绝缘粘结剂的体积电阻率≥10 10Ω·cm；
    可选地，所述导电涂层包括质量含量为30％～45％的导电剂和质量含量为55％～70％的绝缘粘结剂；
    进一步可选地，所述绝缘粘结剂选自PVDF、聚丙烯腈、丁苯橡胶、聚乙烯醇、阿拉伯胶、黄原胶、聚丙烯酸酯组成的组中的任意一种或多种。
  4. 根据权利要求1至3中任一项所述的正极极片，其中，所述导电剂包含选自乙炔黑、碳纤维、导电炭黑、导电石墨、单壁碳纳米管、多壁碳纳米管、石墨烯纳米片、氧化石墨烯纳米片和微粉石墨组成的组中任意一种或多种。
  5. 根据权利要求1至4中任一项所述的正极极片，其中，所述导电涂层的厚度为0.5微米～5微米，可选地，所述导电涂层的厚度为0.8微米～3微米。
  6. 根据权利要求1至5中任一项所述的正极极片，其中，所述集流体为铝箔，可选地，所述铝箔的厚度为8微米～20微米，和/或，所述集流体的纵向、横向的拉伸强度≥175MPa。
  7. 根据权利要求1至6中任一项所述的正极极片，其中，所述正极活性材料包括式(I)～(III)中的至少一种：
    Li a1Ni x1Co y1M1 z1M2 1-x1-y1-z1O 2-b1  式(I)
    Li a2Mn 2-y2M3 y2O 4-b2  式(II)
    cLi 2MnO 3·(1-c)Li a3M4 x3O 2-b3  式(III)
    式(I)中，M1为Mn和/或Al，M2选自Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种，0.8≤a1＜1.2，0≤x1＜1，0≤y1≤1，0≤z1≤1，x1+y1+z1≤1，-0.2≤b1≤0.2；
    式(II)中，0.8≤a2＜1.2，0.6≤y2≤1，-0.2≤b2≤0.2，M3选自Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种；
    式(III)中，0<c<1，0＜x3＜1，0.8<a3<1.2，-0.2≤b3≤0.2，M4选自Ni、Co、Mn中的任意一种，以及Mg、Cu、Zn、Al、Sn、B、Ga、Zr、Cr、Sr、V和Ti组成的组中的任意一种或多种。
  8. 一种二次电池，包括如权利要求1至7任一项所述的正极极片。
  9. 根据权利要求8所述的二次电池，其中，所述二次电池中含有电解液，所述电解液包括锂盐，所述锂盐包括含氟磺酰亚胺锂和六氟磷酸锂；
    可选地，所述电解液还至少满足以下条件之一：
    (1)所述含氟磺酰亚胺锂为双氟磺酰亚胺锂、双(三氟甲基)氟磺酰亚胺锂、(氟磺酰)(三氟甲基磺酰)亚胺锂、(氟磺酰)(五氟乙基磺酰)亚胺锂、(三氟甲基磺酰)(二氟甲基磺酰)亚胺锂、(氟磺酰)(全氟丁基磺酰)亚胺锂、双(五氟乙基磺酰)亚胺锂组成的组中的任意一种或多种；
    (2)所述电解液中所述锂盐的总浓度为0.6mol/L～2mol/L；
    (3)所述电解液中，所述六氟磷酸锂的浓度C1为0.1mol/L～1mol/L，所述含氟磺酰亚胺锂的浓度C2为0.5mol/L～1.5mol/L；
    (4)所述电解液中，所述六氟磷酸锂的浓度C1与所述含氟磺酰亚胺锂的浓度C2满足：1≤C2/C1≤5。
  10. 根据权利要求9所述的二次电池，其中，所述正极极片的导电涂层的厚度d、所述六氟磷酸锂的浓度C1与所述含氟磺酰亚胺锂的浓度C2满足关系式：
    C2/(5×C1)≤d≤lg(C2/C1)+4，
    其中，C1、C2的单位为mol/L，d的单位为μm。
  11. 根据权利要求9或10所述的二次电池，其中，所述电解液还包括有机溶剂和添加剂，所述有机溶剂选自碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯，碳酸亚乙酯、碳酸亚丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸乙丙酯、γ-丁内酯、甲酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸甲酯和四氢呋喃组成的组中的任意一种或多种；和/或，
    所述有机溶剂在电解液中的质量含量为65％～85％；和/或，
    所述添加剂选自碳酸亚乙烯酯、硫酸乙烯酯、二氟草酸硼酸锂、二氟磷酸锂、四氟硼酸锂、1,3-丙磺酸内酯、三氟甲基磺酸锂、和双乙酸硼酸锂组成的组中至少一种；和/或，
    所述添加剂在所述电解液中的总质量含量为0.5％～7％。
  12. 根据权利要求8所述的二次电池，其中，所述负极极片的负极活性材料包括天然石墨、人造石墨、中间相微碳、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12和Li-Al合金组成的组中的任意一种或多种。
  13. 一种电池模块，包括二次电池，其中，所述二次电池为权利要求8至12中任一项所述的二次电池。
  14. 一种电池包，包括电池模块，其中所述电池模块为权利要求13所述的电池模块。
  15. 一种用电装置，包括二次电池或电池模块或电池包，其中，所述二次电池选自权利要求8至12中任一项所述的二次电池、所述电池模块为权利要求13所述的电池模块或所述电池包为权利要求14所述的电池包。
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