WO2023023984A1 - 负极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

负极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023023984A1
WO2023023984A1 PCT/CN2021/114579 CN2021114579W WO2023023984A1 WO 2023023984 A1 WO2023023984 A1 WO 2023023984A1 CN 2021114579 W CN2021114579 W CN 2021114579W WO 2023023984 A1 WO2023023984 A1 WO 2023023984A1
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negative electrode
film layer
electrode film
secondary battery
current collector
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PCT/CN2021/114579
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English (en)
French (fr)
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陈斌溢
王家政
严青伟
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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 CN202180006932.5A priority Critical patent/CN116034497A/zh
Priority to PCT/CN2021/114579 priority patent/WO2023023984A1/zh
Priority to KR1020237001572A priority patent/KR20230031297A/ko
Priority to JP2023501829A priority patent/JP2023542774A/ja
Priority to EP21943336.4A priority patent/EP4163998A4/en
Publication of WO2023023984A1 publication Critical patent/WO2023023984A1/zh
Priority to US18/182,403 priority patent/US20230216028A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M10/052—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/387—Tin or alloys based on tin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light 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
    • H01M4/62—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
    • H01M4/665—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
    • 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
    • H01M2004/027—Negative 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
    • 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 application belongs to the technical field of secondary batteries, and in particular relates to a negative pole piece, a secondary battery, a battery module, a battery pack and an electrical device.
  • the purpose of this application is to provide a negative pole piece, a secondary battery, a battery module, a battery pack, and an electrical device, aiming at solving the problem of lithium precipitation in a secondary battery under high-rate charging and overcharging conditions, and effectively inhibiting lithium
  • the metal is precipitated on the surface of the negative electrode sheet, which significantly improves the kinetic performance, cycle performance and safety performance of the secondary battery.
  • the first aspect of the present application provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector.
  • the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, and the second negative electrode film layer is located between the negative electrode current collector and the first negative electrode film layer.
  • the second negative electrode film layer contains a metal element M, and the atomic radius r M of M and the atomic radius r Li of Li satisfy
  • the negative electrode film layer of the present application has a multilayer structure, and the second negative electrode film layer contains metal element M, and the atomic radius difference between M and Li is small, and the lattice mismatch degree is small, so Li is more likely to solidify on the surface of M. dissolve.
  • the surface of M can be used as a preferential nucleation site for lithium metal, which induces the precipitation of lithium metal on the surface of the second negative electrode film layer M, effectively inhibiting the lithium metal on the surface of the negative electrode sheet. Precipitation, improve the kinetic performance, cycle performance and safety performance of the secondary battery.
  • the lattice structure of M matches that of Li better, and Li is more likely to induce nucleation on the surface of M, so it can better inhibit the precipitation of lithium metal on the surface of the negative electrode sheet. Effect.
  • the negative electrode sheet of the present application can effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, so the secondary battery not only has good kinetic performance, but also has a significantly improved cycle life.
  • the atomic radius r M of M and the atomic radius r Li of Li satisfy
  • the difference between the atomic radii of M and Li is controlled within an appropriate range, which can more effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, and further improve the kinetic performance, cycle performance and safety performance of the secondary battery.
  • M is selected from Sn, Bi, Cd, Ti, Nb, Ta, Sb, Hf, Mg, Zr, Ag, Au, Al, Sc, Mo, W, Pt, Pd, In, Re , Ir, Ga, Os, V, Zn, Ru, Rh in one or more.
  • M is selected from one or more of Sn, Bi, Cd, Ti, Nb, Ta, Sb, Hf, Mg, Zr, Ag, Au, Al.
  • M When M is selected from the above metal elements, its lattice structure is more compatible with that of Li, and Li is more likely to induce nucleation on the surface of M, so it has a better effect of inhibiting the precipitation of lithium metal on the surface of the negative electrode sheet, further improving The kinetic performance, cycle performance and safety performance of secondary batteries.
  • M is located at least in the main body of the negative electrode film layer.
  • the second negative electrode film layer includes an opposite first surface and a second surface along its thickness direction, the first surface is disposed away from the negative electrode current collector, and the second surface is disposed toward the negative electrode current collector , M is located on the first surface of the second negative electrode film layer facing away from the negative electrode current collector and/or on the second surface of the second negative electrode film layer facing the negative electrode current collector.
  • the mass percentage of M is 3%-7%.
  • the mass percentage of M is 3%-5%.
  • the mass percentage of M is in an appropriate range, the precipitation of lithium metal on the surface of the negative electrode sheet can be effectively suppressed, and at the same time, the shortening of the cycle life of the secondary battery can be effectively suppressed.
  • the mass percentage of M is ⁇ 0.5%.
  • the first negative electrode film layer does not contain the metal element M.
  • the first negative electrode film layer does not contain or basically does not contain the metal element M
  • it can effectively ensure that lithium metal is preferentially precipitated on the surface of the second negative electrode film layer M, and further inhibit the precipitation of lithium metal on the surface of the negative electrode sheet.
  • lithium metal is preferentially precipitated on the surface of the second negative electrode film layer M, and the first negative electrode film layer on the surface of the second negative electrode film layer can also inhibit the rapid growth of lithium dendrites, thereby further prolonging the cycle life of the secondary battery.
  • the coating weight ratio of the first negative electrode film layer to the second negative electrode film layer is 0.3 ⁇ 1.2.
  • the coating weight ratio of the first negative electrode film layer to the second negative electrode film layer is 0.5 ⁇ 0.8.
  • the coating weight ratio of the first negative electrode film layer to the second negative electrode film layer is in an appropriate range, which can not only effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, but also effectively inhibit lithium dendrites from reaching the surface of the negative electrode sheet.
  • the second negative electrode film layer includes metal particles, and the metal particles are selected from one or more of M elemental particles and M alloy particles.
  • the alloy of M includes an alloy formed by two or more elements in M, and one or more elements in M and one or more elements in another metal element M1 alloy.
  • M1 includes one or more of Fe, Cu, Ni, Cr, and Mn.
  • the volume average particle diameter Dv50 of the metal particles is ⁇ 5 ⁇ m.
  • the volume average particle diameter Dv50 of the metal particles is ⁇ 1 ⁇ m.
  • the volume average particle diameter Dv50 of the metal particles is controlled within an appropriate range, and a sufficient number of nucleation sites can be formed in the second negative electrode film layer, thereby effectively inhibiting the precipitation of lithium metal on the surface of the negative electrode sheet.
  • the second negative electrode film layer includes one or more of Li-M alloy particles and Li- MM1 alloy particles, M1 represents a metal element, and M1 includes Fe, Cu, Ni, One or more of Cr and Mn.
  • the second aspect of the present application provides a secondary battery, which includes the negative electrode sheet of the first aspect of the present application.
  • a third aspect of the present application provides a battery module, which includes the secondary battery of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack, which includes one of the secondary battery of the second aspect of the present application and the battery module of the third aspect.
  • the fifth aspect of the present application provides an electric device, which includes at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect.
  • the battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of the negative electrode sheet of the present application.
  • FIG. 2 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 3 is an exploded schematic view of an embodiment of the secondary battery of the present application.
  • Fig. 4 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 5 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 6 is an exploded view of FIG. 5 .
  • FIG. 7 is a schematic diagram of an embodiment of an electrical device in which a secondary battery is used as a power source of the present application.
  • FIG. 8 is a cross-sectional scanning electron micrograph of the negative electrode sheet of Example 1.
  • ranges disclosed herein are defined in terms of lower and upper limits, and 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 and may be combined arbitrarily, ie 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, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, 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" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • 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 in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, 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) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: 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).
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active material after the battery is discharged and continue to be used.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions such as lithium ions
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte is between the positive pole piece and the negative pole piece, and mainly plays the role of conducting active ions.
  • lithium ions are extracted from the positive electrode and inserted into the negative electrode.
  • the secondary battery is charged at a high rate or overcharged, it is easy to have insufficient space for the insertion of the negative electrode, and lithium ions are extracted from the positive electrode too quickly but cannot be inserted into the negative electrode in the same amount.
  • Lithium ions that cannot be embedded in the negative electrode in time can only obtain electrons on the surface of the negative electrode and reduce them to form lithium metal, which is the phenomenon of lithium precipitation.
  • the negative electrode is highly polarized.
  • lithium ions When the surface potential of the negative electrode sheet continues to decrease and is lower than the Li/Li + reference electrode potential, lithium ions will obtain electrons on the surface of the negative electrode sheet. and reduced to form lithium metal.
  • Lithium deposition not only degrades the performance of the secondary battery, for example, the cycle life is greatly shortened, and after lithium deposition continues, lithium metal will grow into a tree-like structure, that is, lithium dendrites.
  • the growth of lithium dendrites will destroy the solid electrolyte interface (SEI) film on the surface of the negative active material, resulting in irreversible consumption of active ions; the growth of lithium dendrites will also pierce the separator and cause an internal short circuit, which may cause safety hazards such as combustion and explosion. risk.
  • SEI solid electrolyte interface
  • a negative pole piece which can effectively inhibit the precipitation of lithium metal on the surface of the negative pole piece, significantly improve the kinetic performance, cycle performance and safety performance of the secondary battery, especially improve the performance of the secondary battery under high-rate charging and overcharging conditions Cycle performance and safety performance.
  • the negative electrode sheet of the present application includes a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector.
  • the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer.
  • the second negative electrode film layer is located between the negative electrode current collector and the negative electrode film layer. Between the first negative electrode film layers.
  • the second negative film layer contains metal element M, and the atomic radius r M of M and the atomic radius r Li of Li satisfy
  • the negative electrode film layer of the present application has a multilayer structure, and the second negative electrode film layer contains metal element M, and the atomic radius difference between M and Li is small, and the lattice mismatch degree is small, so Li is more likely to solidify on the surface of M. dissolve.
  • the inventors found that after Li is solid-dissolved on the surface of M, the crystal structure of the formed solid solution is similar to that of Li, so the nucleation interface energy of Li on the surface of M is low. The interface energy is the source of nucleation resistance.
  • the surface nucleation resistance of M is lower, the surface of M can be used as the preferential nucleation site of lithium metal, which induces the precipitation of lithium metal on the surface of M, rather than on the surface of the negative electrode sheet. Precipitate.
  • the polarization of the negative electrode is relatively large, and when the surface potential of the negative electrode sheet is about to be lowered to the overpotential of lithium precipitation, because the surface nucleation resistance of M contained in the second negative electrode film layer is lower. , its surface lithium overpotential is lower than the surface potential of the negative electrode sheet, therefore, it can be used as the preferential nucleation site of lithium metal to induce the precipitation of lithium metal on the surface of the second negative electrode film layer M, effectively inhibiting the lithium metal from forming on the negative electrode.
  • the precipitation on the surface of the sheet improves the kinetic performance, cycle performance and safety performance of the secondary battery.
  • the lattice structure of M matches that of Li better, and Li is more likely to induce nucleation on the surface of M, so it can better inhibit the precipitation of lithium metal on the surface of the negative electrode sheet. Effect.
  • the atomic radius difference between M and Li is large, such as greater than 12%.
  • the lattice mismatch between M and Li is relatively large, and the surface of M cannot be used as a preferential nucleation site for lithium metal, and cannot induce lithium metal in the second phase.
  • the effect of preferential nucleation on the surface of M in the negative electrode film layer When the secondary battery is charged at a high rate or overcharged, lithium metal will still be precipitated on the surface of the negative electrode sheet, and the safety performance of the secondary battery cannot be effectively guaranteed.
  • the negative electrode sheet of the present application can realize the safe use of conventional negative electrode active materials under high-rate charging and overcharging conditions; the negative electrode sheet of the present application can effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, so the secondary battery not only has good Excellent dynamic performance, also has significantly improved cycle life.
  • the atomic radii of metal elements M and Li can refer to "Lange's handbook of chemistry”.
  • the atomic radius r M of M and the atomic radius r Li of Li satisfy
  • the difference between the atomic radii of M and Li is controlled within an appropriate range, which can more effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, and further improve the kinetic performance, cycle performance and safety performance of the secondary battery.
  • the mass percentage of M is ⁇ 0.5%.
  • the first negative electrode film layer does not contain the metal element M.
  • the first negative electrode film layer does not contain or basically does not contain the metal element M
  • it can effectively ensure that lithium metal is preferentially precipitated on the surface of the second negative electrode film layer M, and further inhibit the precipitation of lithium metal on the surface of the negative electrode sheet.
  • lithium metal is preferentially precipitated on the surface of the second negative electrode film layer M, and the first negative electrode film layer on the surface of the second negative electrode film layer can also inhibit the rapid growth of lithium dendrites, thereby further prolonging the cycle life of the secondary battery.
  • the mass percentage of M is 1% ⁇ 10%.
  • the mass percentage of M is 1% to 9%, 1% to 8%, 1% to 7%, 1% to 6%, 1% to 5%, 1% to 4%, 2% to 9%, 2% ⁇ 8%, 2% ⁇ 7%, 2% ⁇ 6%, 2% ⁇ 5%, 2% ⁇ 4%, 3% ⁇ 9%, 3% ⁇ 8%, 3% ⁇ 7% , 3% ⁇ 6%, 3% ⁇ 5%, 3% ⁇ 4%, 3.5% ⁇ 9%, 3.5% ⁇ 8%, 3.5% ⁇ 7%, 3.5% ⁇ 6%, 3.5% ⁇ 5%, or 3.5% to 4.5%.
  • the mass percentage of M When the mass percentage of M is low, the number of nucleation sites in the second negative electrode film layer is relatively small. The effect of surface precipitation is not obvious.
  • the mass percentage of M When the mass percentage of M is higher, the consumption of the electrolyte also increases, and because the volume expansion of M after Li solid solution occurs on the surface of M, the volume expansion of the second negative electrode film layer and the negative electrode sheet will become larger, The cycle life of the secondary battery will be shortened to a certain extent.
  • the mass percentage of M is in an appropriate range, the precipitation of lithium metal on the surface of the negative electrode sheet can be effectively suppressed, and at the same time, the shortening of the cycle life of the secondary battery can be effectively suppressed.
  • M is selected from Sn, Bi, Cd, Ti, Nb, Ta, Sb, Hf, Mg, Zr, Ag, Au, Al, Sc, Mo, W, Pt, Pd, In, Re, Ir , Ga, Os, V, Zn, Ru, Rh in one or more.
  • M is selected from one or more of Sn, Bi, Cd, Ti, Nb, Ta, Sb, Hf, Mg, Zr, Ag, Au, Al.
  • M is selected from one or more of Nb, Au, Ag, Al, Mg, Ti, Cd, and Zr.
  • M When M is selected from the above metal elements, its lattice structure is more compatible with that of Li, and Li is more likely to induce nucleation on the surface of M, so it has a better effect of inhibiting the precipitation of lithium metal on the surface of the negative electrode sheet, further improving The kinetic performance, cycle performance and safety performance of secondary batteries.
  • the second negative electrode film layer includes a main body, and a first surface and a second surface opposite along its thickness direction, the first surface is disposed away from the negative electrode current collector, and the second surface is disposed toward the negative electrode current collector.
  • M is located at one or more positions of the main body of the second negative electrode film layer, the first surface of the second negative electrode film layer facing away from the negative electrode collector, and the second surface of the second negative electrode film layer facing the negative electrode collector. For example, (1) M is only located on the main body of the negative electrode film layer, (2) M is only located on the first surface of the second negative electrode film layer facing away from the negative electrode collector, and (3) M is only located on the second negative electrode film layer facing the negative electrode collector.
  • the second surface of the fluid, (4) M is simultaneously located at the main body of the negative electrode film layer, and the second negative electrode film layer faces away from the first surface of the negative electrode current collector, and (5) M is simultaneously located at the main body of the negative electrode film layer,
  • the second negative electrode film layer faces two positions on the second surface of the negative electrode current collector,
  • (6) M is simultaneously located on the first surface of the second negative electrode film layer facing away from the negative electrode current collector, and the second negative electrode film layer faces the second surface of the negative electrode current collector.
  • Two positions on the surface, (7)M are located at the main body of the negative electrode film layer, the first surface of the second negative electrode film layer facing away from the negative electrode current collector, and the second surface of the second negative electrode film layer facing the negative electrode current collector.
  • M is located at least in the main body of the second negative electrode film layer.
  • M when M is located on the first surface of the second negative electrode film layer facing away from the negative electrode current collector, M can form a layered structure on the first surface of the second negative electrode film layer.
  • the layered structure is discontinuous.
  • M is distributed at intervals or in arrays on the first surface of the second negative electrode film layer.
  • M when M is located on the second surface of the second negative electrode film layer facing the negative electrode current collector, M can form a layered structure on the second surface of the second negative electrode film layer.
  • the layered structure is discontinuous.
  • M is distributed at intervals or in arrays on the second surface of the second negative electrode film layer.
  • the coating weight ratio of the first negative electrode film layer to the second negative electrode film layer is 0.3 ⁇ 1.2.
  • the coating weight ratio of the first negative electrode film layer to the second negative electrode film layer is 0.3-1, 0.4-1, 0.5-1, 0.3-0.8, 0.4-0.8, 0.5-0.8, 0.3-0.7, 0.4 ⁇ 0.7, 0.5 ⁇ 0.7, 0.3 ⁇ 0.6, 0.4 ⁇ 0.6, or 0.5 ⁇ 0.6.
  • the coating weight of the first negative electrode film layer and the second negative electrode film layer When the coating weight of the first negative electrode film layer and the second negative electrode film layer is relatively large, the nucleation sites of the second negative electrode film layer are relatively few, and the effect of inhibiting the precipitation of lithium metal on the surface of the negative electrode sheet is not obvious.
  • the coating weight of the first negative electrode film layer and the second negative electrode film layer is relatively small, the thickness of the first negative electrode film layer is relatively small, and the lithium dendrite formed by the second negative electrode film layer passes through the first negative electrode film layer to reach the negative electrode more easily.
  • the surface of the pole piece increases the risk of short circuits within the battery.
  • the coating weight ratio of the first negative electrode film layer to the second negative electrode film layer is in an appropriate range, which can not only effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, but also effectively inhibit lithium dendrites from reaching the surface of the negative electrode sheet.
  • the second negative electrode film layer may include metal particles, and the metal particles are selected from one or more of M elemental particles and M alloy particles.
  • the alloy of M includes an alloy formed by two or more elements in M, and an alloy formed by one or more elements in M and one or more elements in another metal element M .
  • the alloy of M includes an alloy formed of two or more elements in M.
  • M 1 includes one or more of Fe, Cu, Ni, Cr, and Mn.
  • the volume average particle diameter Dv50 of the metal particles is ⁇ 5 ⁇ m.
  • the volume average particle diameter Dv50 of the metal particles is ⁇ 1 ⁇ m. More specifically, the volume average particle diameter Dv50 of the metal particles is ⁇ 0.5 ⁇ m.
  • the volume average particle diameter Dv50 of the metal particles is controlled within an appropriate range, and a sufficient number of nucleation sites can be formed in the second negative electrode film layer, thereby effectively inhibiting the precipitation of lithium metal on the surface of the negative electrode sheet.
  • the volume average particle diameter Dv50 of a material is a well-known meaning in the art, and can be measured by methods and instruments known in the art. For example, it can be determined by using a laser particle size analyzer (such as the British Malvern Mastersizer 2000E) with reference to the GB/T 19077-2016 particle size distribution laser diffraction method.
  • a laser particle size analyzer such as the British Malvern Mastersizer 2000E
  • the second negative electrode film layer may include one or more of Li-M alloy particles and Li- MM1 alloy particles, M1 represents a metal element, and M1 includes Fe, Cu, Ni, Cr , one or more of Mn.
  • Li-M alloy means an alloy formed by Li and one or more of metal elements M
  • Li- MM1 alloy means one or more of Li and metal elements M and one or more of metal elements M1 alloy formed.
  • Li-M alloys are Li-Sn, Li-Bi, Li-Cd, Li-Ti, Li-Nb, Li-Ta, Li-Sb, Li-Hf, Li-Mg, Li-Zr, Li- Ag, Li-Au, Li-Al, Li-Sc, Li-Mo, Li-W, Li-Pt, Li-Pd, Li-In, Li-Re, Li-Ir, Li-Ga, Li-Os, Li-V, Li-Zn, Li-Ru, Li-Rh, Li-Mg-Al, Li-Mg-Zr, Li-Mg-Zn, Li-Ag-Al, Li-Ag-Zn, Li-Ag- One or more of Mg, Li-Ti-Al.
  • the Li-MM 1 alloy is selected from one of Li-Mg-Mn, Li-Al-Mn, Li-Al-Fe, Li-Al-Cu, Li-Ti-Ni, Li-Ti-Cr or Several kinds.
  • the second negative electrode film layer may also include a second negative electrode active material, optional Conductive agent, optional binder and other optional additives.
  • the first negative electrode film layer includes a first negative electrode active material, an optional conductive agent, an optional binder, and other optional additives.
  • the types of the first negative electrode active material and the second negative electrode active material are not specifically limited, and negative electrode active materials known in the art for secondary batteries can be used.
  • the types of the first negative electrode active material and the second negative electrode active material may be the same or different.
  • the first negative electrode active material and the second negative electrode active material each independently include graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, silicon-based materials, tin-based materials, lithium titanate one or more of.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.
  • the tin-based material may include one or more of simple tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the type and content of the conductive agent and the binder are not specifically limited, and can be selected according to actual needs.
  • the conductive agent type of the first negative electrode film layer and the second negative electrode film layer can be the same or different.
  • the conductive agent can include superconducting carbon, carbon black (such as acetylene black, Ketjen black, etc.), carbon dots, carbon One or more of nanotubes, graphene and carbon nanofibers.
  • the binder type of the first negative electrode film layer and the second negative electrode film layer can be the same or different.
  • the binder can include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS) one or more of.
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • acrylic resin for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS) one or more of.
  • Other optional additives of the first negative electrode film layer and the second negative electrode film layer can be the same or different, as an example, other optional additives can include a thickener (such as sodium
  • a metal foil or a composite current collector can be used as the negative electrode current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the negative electrode film layer is disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • FIG. 1 shows a schematic diagram of an embodiment of a negative electrode sheet 10 of the present application.
  • the negative electrode sheet 10 can be composed of a negative electrode current collector 11, a second negative electrode film layer 122 respectively arranged on both sides of the negative electrode collector body 11, and a first negative electrode film layer 121 arranged on the second negative electrode film layer 122.
  • the second negative electrode film layer 122 is located between the negative electrode collector 11 and the first negative electrode film layer 121 .
  • the second negative electrode film layer 122 includes opposite first surface 1221 and second surface 1222 along its thickness direction, the first surface 1221 is disposed away from the negative electrode current collector 11 , and the second surface 1222 is disposed toward the negative electrode current collector 11 .
  • the negative electrode sheet 10 of the present application can also have other embodiments.
  • the negative electrode sheet 10 is composed of the negative electrode collector 11, the second negative electrode film layer 122 arranged on one side of the negative electrode collector, and the second negative electrode film layer 122 arranged on the second negative electrode.
  • the first negative electrode film layer 121 on the film layer 122 is formed.
  • the negative electrode sheet of the present application does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet of the present application may further include a conductive primer layer (for example, composed of a conductive agent and a binder) disposed between the negative electrode current collector and the second negative electrode film layer.
  • the negative electrode sheet of the present application further includes a protective layer covering the surface of the first negative electrode film layer.
  • the preparation method of the negative electrode sheet of the present application may include the following steps: forming a second negative electrode film layer on at least one side of the negative electrode current collector, the second negative electrode film layer includes metal particles, and the metal particles are selected from M One or more of elemental particles and alloy particles of M; the first negative electrode film layer is formed on the surface of the second negative electrode film layer.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, other optional additives, etc. in a solvent and stirring them evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the first negative electrode active material, optional conductive agent, optional binder, and other optional additives can be dispersed in a solvent and stirred uniformly to form the first negative electrode slurry
  • the second negative electrode Active materials, metal particles, optional conductive agents, optional binders, and other optional additives are dispersed in the solvent and stirred uniformly to form a second negative electrode slurry.
  • the first negative electrode slurry and the second negative electrode slurry can be coated simultaneously at one time, or can be coated twice.
  • the first negative electrode slurry and the second negative electrode slurry are coated simultaneously at one time. Coating at one time can make the adhesion between the first negative electrode film layer and the second negative electrode film layer better, help to reduce the overall interface resistance of the negative electrode film layer, and further improve the cycle performance of the battery.
  • the preparation method of the negative electrode sheet may include the following steps: forming a second negative electrode film layer on at least one side of the negative electrode current collector, forming a layer of metal M on the surface of the second negative electrode film layer, and then continuing to form After the first negative electrode film layer is cold-pressed, M is located on the first surface of the second negative electrode film layer facing away from the negative electrode current collector.
  • the layered structure of the metal M is in a discontinuous form, for example, in a spaced distribution state or an array distribution state.
  • Methods for forming the metal M on the surface of the second negative electrode film layer include coating, shot blasting, spraying, vapor deposition, etc., but are not limited thereto.
  • the metal M is deposited on the surface of the second negative electrode film layer by vapor deposition method.
  • the vapor deposition method may be one or more of atomic layer deposition, chemical vapor deposition and physical vapor deposition.
  • the preparation method of the negative electrode sheet may include the following steps: forming a layer of metal M on at least one side of the negative electrode current collector, then forming a second negative electrode film layer on the surface of the negative electrode current collector, and then forming a second negative electrode film layer on the second negative electrode
  • the first negative electrode film layer is formed on the surface of the film layer, and after cold pressing, M is located on the second surface of the second negative electrode film layer facing the negative electrode current collector.
  • the layered structure of the metal M is in a discontinuous form, for example, in a spaced distribution state or an array distribution state.
  • the method of forming the metal M on the surface of the negative electrode current collector includes coating, vapor deposition, gravure process, etc., but is not limited thereto.
  • the metal M is deposited on the surface of the negative electrode current collector by using a vapor deposition method.
  • the vapor deposition method may be one or more of atomic layer deposition, chemical vapor deposition and physical vapor deposition.
  • the mass percentage content test of M in the second negative electrode film layer can be obtained by the following method.
  • the respective thicknesses of the first negative electrode film layer and the second negative electrode film layer are obtained by using a scanning electron microscope (for example, ZEISS Sigma 300).
  • the negative pole piece is cut into a sample to be tested with a certain size (for example, 2cm ⁇ 2cm), and the negative pole piece is fixed on the sample stage by paraffin.
  • the sample stage into the sample rack and lock it, turn on the power of the argon ion cross-section polisher (such as IB-19500CP) and vacuumize (such as 10 -4 Pa), set the flow rate of argon gas (such as 0.15MPa) and voltage (such as 8KV) and polishing time (for example, 2 hours), adjust the sample stage to swing mode and start polishing.
  • the argon ion cross-section polisher such as IB-19500CP
  • vacuumize such as 10 -4 Pa
  • polishing time for example, 2 hours
  • Sample test can refer to JY/T010-1996.
  • multiple (for example, 5) different areas can be randomly selected in the sample to be tested for scanning test, and under a certain magnification (for example, 500 times), read the first negative electrode in the scale test area
  • the average value of multiple test areas is taken as the test result.
  • the thickness ratio of the first negative electrode film layer and the second negative electrode film layer can obtain the coating weight ratio of the first negative electrode film layer and the second negative electrode film layer.
  • the negative electrode sheet coated on one side and cold-pressed if it is a negative electrode sheet coated on both sides, you can wipe off the negative electrode film on one side first), and cut it into a sample of a certain size (for example, 2cm ⁇ 2cm ), and then scrape powder; All the powders obtained will be tested with inductively coupled plasma-Optical Emission spectrometers (ICP-OES) to obtain the mass concentration of metal element M in the negative electrode film layer; through the first The coating weight ratio of the first negative electrode film layer and the second negative electrode film layer is calculated to obtain the mass percentage content of the metal element M in the second negative electrode film layer.
  • the negative electrode sheet can be cut into multiple samples (for example, 5) with a certain size to be tested, and the average value of the multiple test samples is taken as the test result.
  • the secondary battery includes a positive electrode sheet
  • the positive electrode sheet generally includes a positive electrode collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector and including a positive electrode active material.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used for the positive electrode current collector.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the positive electrode film layer includes a positive electrode active material
  • the positive electrode active material can be a positive electrode active material known in the art for secondary batteries.
  • the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium iron manganese phosphate
  • One or more of the composite materials with carbon and their respective modified compounds may be not limited to these materials, and other conventionally known materials that can be used as a secondary battery positive electrode active material may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the modified compounds of the above-mentioned positive electrode active materials may be doping modification, surface coating modification, or both doping and surface coating modification of the positive electrode active material.
  • the positive electrode film layer generally includes a positive electrode active material, optionally a binder, and optionally a conductive agent.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder used for the positive film layer may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoro One or more of propylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoro
  • fluorine-containing acrylate resin fluorine-containing acrylate resin
  • the conductive agent used in the positive film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the composition or parameters of each positive electrode film layer given in this application all refer to the composition or parameter range of a single film layer of the positive electrode current collector.
  • the positive electrode film layer is arranged on two opposite surfaces of the positive electrode current collector, if the composition or parameters of the positive electrode film layer on any one of the surfaces meet the requirements of this application, it is deemed to fall within the protection scope of this application.
  • the electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the secondary battery of the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytic solutions).
  • the electrolyte is an electrolytic solution.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the type of electrolyte salt is not specifically limited, and can be selected according to actual needs.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (bisfluorosulfonimide Lithium), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium difluorooxalate borate), LiPO 2 F 2 (difluoro Lithium phosphate), LiDFOP (lithium difluorooxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • the type of solvent is not specifically limited, and can be selected according to actual needs.
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate ester (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA ), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyric acid
  • ethyl ester EB
  • 1,4-butyrolactone GBL
  • sulfolane SF
  • MSM dimethyl sulfone
  • the solvent is a non-aqueous solvent.
  • additives are optionally included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance. Additives etc.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from one or more 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. When the separator is a multilayer composite film, the materials of each layer may be the same or different.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • 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 can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.
  • FIG. 2 shows a secondary battery 5 with a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening to close the receiving chamber.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to requirements.
  • the secondary battery can be assembled into a battery module, and the number of 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. 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 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • 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.
  • 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 body 2 and a lower box body 3 , the upper box body 2 is used to cover 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.
  • Embodiments of the present application further provide an electric device, the electric device includes at least one of the secondary battery, the battery module, and the battery pack of the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 7 is an example of an electrical device.
  • the electric device is 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 electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2, and the solvent N-methylpyrrolidone ( NMP), stirred under the action of a vacuum mixer until the system was uniform, to obtain the positive electrode slurry; the positive electrode slurry was evenly coated on the aluminum foil of the positive electrode current collector, dried at room temperature, transferred to an oven to continue drying, and then cold pressed, separated Cut to obtain the positive pole piece.
  • NMP solvent N-methylpyrrolidone
  • the negative electrode active material graphite After mixing the negative electrode active material graphite, the conductive agent acetylene black, the thickener carboxymethylcellulose sodium (CMC-Na), and the binder styrene-butadiene rubber (SBR) in a mass ratio of 96.4:1:1.2:1.4, and then mix with The Ag elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) were mixed according to the mass ratio of 98:2, the solvent deionized water was added, and the system was stirred under the action of a vacuum mixer until the system was uniform to obtain the second negative electrode slurry.
  • the Ag elemental particles volume average particle diameter Dv50 is 0.05 ⁇ m
  • the first negative electrode slurry and the second negative electrode slurry are uniformly coated on both surfaces of the negative electrode current collector copper foil at the same time, and after drying at room temperature, transfer to an oven to continue drying, and then undergo cold pressing and slitting to obtain the negative electrode. piece.
  • the second negative electrode film layer is located between the negative electrode current collector and the first negative electrode film layer, the coating weight of the first negative electrode film layer is 4.3 mg/cm 2 , and the coating weight of the second negative electrode film layer is 6.7 mg/cm 2 .
  • the mass proportion of Ag elemental particles in the second negative electrode film layer is 2%.
  • EC ethylene carbonate
  • EMC ethylmethyl carbonate
  • DEC diethyl carbonate
  • a polyethylene film was used as a separator.
  • the positive electrode, separator, and negative electrode in order, so that the separator is between the positive electrode and the negative electrode for isolation, and then wind the electrode assembly; place the electrode assembly in the outer packaging After being dried, the electrolyte is injected, and the secondary battery is obtained through processes such as vacuum packaging, standing still, chemical formation, and shaping.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) is mixed according to the mass ratio of 96.4:1:1.2:1.4, and then mixed with Ag elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) according to the mass ratio of 97:3, adding solvent deionized water, stirring under the action of a vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Ag elemental particles in the second negative electrode film layer is 3%.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) was mixed at a mass ratio of 96.4:1:1.2:1.4, then mixed with Ag elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) at a mass ratio of 95:5, added solvent deionized water, and stirred under the action of a vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Ag elemental particles in the second negative electrode film layer is 5%.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) is mixed according to the mass ratio of 96.4:1:1.2:1.4, and then mixed with Ag elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) according to the mass ratio of 90:10, adding solvent deionized water, stirring under the action of a vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Ag elemental particles in the second negative electrode film layer is 10%.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) in a mass ratio of 96.4:1:1.2:1.4, then mixed with Al elemental particles (volume average particle diameter Dv50 of 0.05 ⁇ m) in a mass ratio of 95:5, adding solvent deionized water, and stirring under the action of a vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Al simple substance particles in the second negative electrode film layer is 5%.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) is mixed by mass ratio 96.4:1:1.2:1.4, then mixed with Mg elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) by mass ratio 95:5, add solvent deionized water, and stir under the action of vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Mg elemental particles in the second negative electrode film layer is 5%.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) is mixed according to the mass ratio of 96.4:1:1.2:1.4, and then mixed with Nb elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) according to the mass ratio of 95:5, adding solvent deionized water, stirring under the action of a vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Nb elemental particles in the second negative electrode film layer is 5%.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the preparation process of the negative electrode sheet specifically includes the following steps.
  • the negative electrode active material graphite the conductive agent acetylene black, the thickener carboxymethylcellulose sodium (CMC-Na), and the binder styrene-butadiene rubber (SBR) at a mass ratio of 96.4:1:1.2:1.4, and add the solvent Deionized water is stirred under the action of a vacuum mixer until the system is uniform to obtain negative electrode slurry, and the negative electrode slurry is divided into two parts, which are respectively used as the first negative electrode slurry and the second negative electrode slurry.
  • CMC-Na thickener carboxymethylcellulose sodium
  • SBR binder styrene-butadiene rubber
  • the first negative electrode slurry and the second negative electrode slurry are uniformly coated on both surfaces of the negative electrode current collector copper foil at the same time, and after drying at room temperature, transfer to an oven to continue drying, and then undergo cold pressing and slitting to obtain the negative electrode. piece.
  • the second negative electrode film layer is located between the negative electrode current collector and the first negative electrode film layer, the coating weight of the first negative electrode film layer is 4.3 mg/cm 2 , and the coating weight of the second negative electrode film layer is 6.7 mg/cm 2 .
  • the preparation method of the secondary battery is similar to that of Example 1, except that the preparation process of the negative electrode sheet specifically includes the following steps.
  • the negative electrode active material graphite After mixing the negative electrode active material graphite, the conductive agent acetylene black, the thickener carboxymethylcellulose sodium (CMC-Na), and the binder styrene-butadiene rubber (SBR) in a mass ratio of 96.4:1:1.2:1.4, and then mix with The Ag elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) were mixed according to the mass ratio of 95:5, the solvent deionized water was added, and the system was stirred under the action of a vacuum mixer until the system was uniform to obtain the negative electrode slurry.
  • the Ag elemental particles volume average particle diameter Dv50 is 0.05 ⁇ m
  • the negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, dried at room temperature, transferred to an oven for further drying, and then subjected to cold pressing and slitting to obtain negative electrode sheets.
  • the coating weight of the negative electrode film layer was 11.0 mg/cm 2 .
  • the preparation method of the secondary battery is similar to that of Example 1, except that the preparation process of the negative electrode sheet specifically includes the following steps.
  • the negative electrode active material graphite After mixing the negative electrode active material graphite, the conductive agent acetylene black, the thickener carboxymethylcellulose sodium (CMC-Na), and the binder styrene-butadiene rubber (SBR) in a mass ratio of 96.4:1:1.2:1.4, and then mix with The Ag elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) were mixed according to the mass ratio of 95:5, the solvent deionized water was added, and the system was stirred under the action of a vacuum mixer until the system was uniform to obtain the first negative electrode slurry.
  • the Ag elemental particles volume average particle diameter Dv50 is 0.05 ⁇ m
  • the first negative electrode slurry and the second negative electrode slurry are uniformly coated on both surfaces of the negative electrode current collector copper foil at the same time, and after drying at room temperature, transfer to an oven to continue drying, and then undergo cold pressing and slitting to obtain the negative electrode. piece.
  • the second negative electrode film layer is located between the negative electrode current collector and the first negative electrode film layer, the coating weight of the first negative electrode film layer is 4.3 mg/cm 2 , and the coating weight of the second negative electrode film layer is 6.7 mg/cm 2 .
  • the mass proportion of Ag elemental particles in the first negative electrode film layer is 5%.
  • the preparation method of secondary battery is similar to embodiment 1, and difference is: negative electrode active material graphite, conductive agent acetylene black, thickener sodium carboxymethyl cellulose (CMC-Na), binding agent styrene-butadiene rubber (SBR ) is mixed according to the mass ratio of 96.4:1:1.2:1.4, and then mixed with Ni elemental particles (volume average particle diameter Dv50 is 0.05 ⁇ m) according to the mass ratio of 95:5, adding solvent deionized water, stirring under the action of a vacuum mixer Until the system is uniform, the second negative electrode slurry is obtained.
  • the mass proportion of Nb elemental particles in the second negative electrode film layer is 5%.
  • the secondary battery was discharged to 2.8V at a constant current rate of 1C. Then charge to 4.2V with a constant current at a rate of 1C, and continue to charge at a constant voltage until the current is 0.05C. At this time, the secondary battery is fully charged. Let the fully charged secondary battery stand for 5 minutes, and then discharge it to 2.8V at a constant current of 1C rate. The discharge capacity at this time is the actual capacity of the secondary battery at 1C rate, which is recorded as C0.
  • the secondary battery was discharged to 2.8V at a constant current rate of 1C. Then charge with a constant current at a rate of 1C, and design gradient charging times of 1h, 1.1h, 1.2h, 1.3h, 1.4h.... Disassemble the secondary battery after each charge, observe the lithium deposition on the surface of the negative electrode sheet, and record the charging time t(h) when the lithium deposition on the surface of the negative electrode sheet just begins.
  • the charging time t ⁇ 100% means that the secondary battery is overcharged to the SOC state where lithium precipitation begins.
  • the secondary battery was discharged to 2.8V at a constant current rate of 1C. Then charge the secondary battery at a constant current rate of 1C to 4.2V, and continue to charge at a constant voltage until the current is 0.05C. At this time, the secondary battery is fully charged. Record the charging capacity at this time, which is the charging capacity of the first cycle; Let the secondary battery stand still for 5 minutes and discharge it to 2.8V at a constant current rate of 1C. This is a cyclic charge and discharge process. Record the discharge capacity at this time, which is the discharge capacity of the first cycle.
  • the secondary battery is subjected to cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle is recorded until the discharge capacity of the secondary battery decays to 80% of the discharge capacity of the first cycle, and the number of cycles at this time is used to characterize the secondary battery.
  • the secondary battery was discharged to 2.8V at a constant current rate of 1C. Then charge the secondary battery to 4.2V at a constant current rate of 3C, and continue to charge at a constant voltage until the current is 0.05C. At this time, the secondary battery is fully charged. Record the charging capacity at this time, which is the charging capacity of the first cycle; Let the secondary battery stand still for 5 minutes and discharge it to 2.8V at a constant current rate of 3C. This is a cycle charge and discharge process. Record the discharge capacity at this time, which is the discharge capacity of the first cycle.
  • the secondary battery is subjected to cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle is recorded until the discharge capacity of the secondary battery decays to 80% of the discharge capacity of the first cycle, and the number of cycles at this time is used to characterize the secondary battery.
  • FIG. 8 is a cross-sectional scanning electron microscope image of the negative electrode sheet prepared in Example 1. It can be seen from Figure 8 that the Ag elemental particles are evenly distributed in the main part of the second negative electrode film layer, and the surface of Ag serves as the preferential nucleation site of lithium metal point, can play the effect of inducing the nucleation of lithium metal on the surface of Ag in the second negative electrode film layer, and effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet. Good dynamic performance and safety performance, and the cycle performance of the secondary battery is also better.
  • the negative electrode film layer of comparative example 2 is a single layer, and Ag elemental particles are added in the negative electrode film layer, and the surface of Ag can be used as the preferential nucleation site of lithium metal, but since the Ag elemental particles are uniformly distributed in the negative electrode film layer, It cannot play a role in inhibiting the precipitation of lithium metal on the surface of the negative electrode sheet. Therefore, the kinetic performance and cycle performance of the secondary battery under high-rate charging and overcharging conditions are poor. No metal particles were added in the second negative electrode film layer of Comparative Example 3, and Ag elemental particles were added in the first negative electrode film layer.
  • the surface of Ag can be used as the preferential nucleation site of lithium metal, but since the Ag elemental particles are evenly distributed in the The first negative electrode film layer cannot inhibit the precipitation of lithium metal on the surface of the negative electrode sheet. Therefore, the kinetic performance and cycle performance of the secondary battery under high-rate charging and overcharging conditions are poor.
  • the metal particles added in the second negative electrode film layer are Ni simple particles, and the atomic radius difference between Ni and Li is too large.
  • the surface nucleation effect of Ni in the film layer cannot effectively inhibit the precipitation of lithium metal on the surface of the negative electrode sheet, and the kinetic performance of the secondary battery is very poor under high-rate charging and overcharging conditions. At the same time, it is difficult for the secondary battery to have more Long cycle life.

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Abstract

本申请提供一种负极极片、二次电池、电池模块、电池包和用电装置，所述负极极片包括负极集流体以及设置在所述负极集流体上的负极膜层，所述负极膜层包括第一负极膜层以及第二负极膜层，所述第二负极膜层位于所述负极集流体和所述第一负极膜层之间。所述第二负极膜层包含金属元素M，且M的原子半径rM与Li的原子半径rLi满足（aa）。本申请能有效抑制锂金属在负极极片表面析出，显著改善二次电池的动力学性能、循环性能和安全性能。

Description

负极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请属于二次电池技术领域，具体涉及一种负极极片、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池在各类电子产品和新能源汽车等产业的应用及推广，其能量密度受到越来越多的关注。但是，二次电池在大倍率充电过程中，负极极片表面不可避免地产生析锂现象。另外，在二次电池过度充电时，负极极片表面也会产生析锂现象。
发明内容
本申请的目的在于提供一种负极极片、二次电池、电池模块、电池包和用电装置，旨在解决二次电池在大倍率充电及过度充电条件下产生的析锂问题，有效抑制锂金属在负极极片表面析出，显著改善二次电池的动力学性能、循环性能和安全性能。
本申请第一方面提供一种负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体上的负极膜层。所述负极膜层包括第一负极膜层以及第二负极膜层，所述第二负极膜层位于所述负极集流体和所述第一负极膜层之间。所述第二负极膜层包含金属元素M，且M的原子半径r M与Li的原子半径r Li满足
Figure PCTCN2021114579-appb-000001
本申请的负极膜层具有多层结构，第二负极膜层包含金属元素M，M与Li的原子半径相差较小、晶格错配度较小，这样，Li更容易在M的表面发生固溶。当二次电池面临大倍率充电、过度充电时，M的表面可以作为锂金属的优先形核位点，诱导锂金属在第二负极膜层M的表面析出，有效抑制锂金属在负极极片表面析出，提升二次电池的动力学性能、循环性能和安全性能。M与Li的原子半径相差较小时，M晶格结构与Li的晶格结构更匹配，Li更容易在M的表面诱导形核，因此能具有更好的抑制锂金属在负极极片表面析出的效果。本申请的负极极片可以有效抑制锂金属在负极极片表面析出，因此二次电池不仅具有良好的动力学性能，还具有显著改善的循环寿命。
在本申请任意实施方式中，M的原子半径r M与Li的原子半径r Li满足
Figure PCTCN2021114579-appb-000002
Figure PCTCN2021114579-appb-000003
M与Li的原子半径之差控制在合适的范围内，能够更有效抑制锂金属在负极极片表面析出，进一步提升二次电池的动力学性能、循环性能和安全性能。
在本申请任意实施方式中，M选自Sn、Bi、Cd、Ti、Nb、Ta、Sb、Hf、Mg、Zr、Ag、Au、Al、Sc、Mo、W、Pt、Pd、In、Re、Ir、Ga、Os、V、Zn、Ru、Rh中的一种或几种。可选地，M选自Sn、Bi、Cd、Ti、Nb、Ta、Sb、Hf、Mg、Zr、Ag、Au、Al中的一种或几种。
M选自上述金属元素时，其晶格结构与Li的晶格结构更匹配，Li更容易在M表面诱导形核，因此具有更好的抑制锂金属在负极极片表面析出的效果，进一步提升二次电池的动力学性能、循环性能和安全性能。
在本申请任意实施方式中，M至少位于负极膜层的主体部。
在本申请任意实施方式中，第二负极膜层沿自身厚度方向包括相对的第一表面和第二表面，第一表面背向所述负极集流体设置，第二表面朝向所述负极集流体设置，M位于第二负极膜层背向负极集流体的第一表面和/或第二负极膜层朝向负极集流体的第二表面。
在本申请任意实施方式中，基于第二负极膜层的总质量，M的质量百分含量为3％～7％。可选地，M的质量百分含量为3％～5％。
M的质量百分含量在合适的范围内，能够在有效抑制锂金属在负极极片表面析出的同时，有效抑制二次电池循环寿命的缩短。
在本申请任意实施方式中，基于第一负极膜层的总质量，M的质量百分含量≤0.5％。
在本申请任意实施方式中，第一负极膜层不包含金属元素M。
第一负极膜层不含或基本不含金属元素M时，能够有效确保锂金属优先在第二负极膜层M表面析出，进一步抑制锂金属在负极极片表面析出。同时，锂金属优先在第二负极膜层M表面析出，第二负极膜层表面的第一负极膜层还能起到抑制锂枝晶快速生长的效果，从而进一步延长二次电池的循环寿命。
在本申请任意实施方式中，第一负极膜层与第二负极膜层的涂布重量比为0.3～1.2。可选地，第一负极膜层与第二负极膜层的涂布重量比为0.5～0.8。
第一负极膜层与第二负极膜层的涂布重量比在合适的范围内，不仅能够有效抑制锂金属在负极极片表面析出，还能够有效抑制锂枝晶到达负极极片表面。
在本申请任意实施方式中，第二负极膜层包括金属颗粒，金属颗粒选自M的单质颗粒、M的合金颗粒中的一种或几种。
在本申请任意实施方式中，M的合金包括M中的两种以上的元素形成的合金、以及M中的一种或几种元素与另一金属元素M 1中的一种或几种元素形成的合金。
在本申请任意实施方式中，M 1包括Fe、Cu、Ni、Cr、Mn中的一种或几种。
在本申请任意实施方式中，金属颗粒的体积平均粒径Dv50≤5μm。可选地，金属颗粒的体积平均粒径Dv50≤1μm。
金属颗粒的体积平均粒径Dv50控制在合适的范围内，可以在第二负极膜层中形成足够数量的形核位点，进而有效抑制锂金属在负极极片表面析出。
在本申请任意实施方式中，第二负极膜层包括Li-M合金颗粒、Li-M-M 1合金颗粒中的一种或几种，M 1表示金属元素，且M 1包括Fe、Cu、Ni、Cr、Mn中的一种或几种。
本申请第二方面提供一种二次电池，其包括本申请第一方面的负极极片。
本申请第三方面提供一种电池模块，其包括本申请第二方面的二次电池。
本申请第四方面提供一种电池包，其包括本申请第二方面的二次电池、第三方面的电池模块中的一种。
本申请第五方面提供一种用电装置，其包括本申请第二方面的二次电池、第三方 面的电池模块、第四方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
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方式，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是本申请的负极极片的一实施方式的示意图。
图2是本申请的二次电池的一实施方式的示意图。
图3是本申请的二次电池的一实施方式的分解示意图。
图4是本申请的电池模块的一实施方式的示意图。
图5是本申请的电池包的一实施方式的示意图。
图6是图5的分解图。
图7是本申请的二次电池用作电源的用电装置的一实施方式的示意图。
图8是实施例1的负极极片的断面扫描电子显微镜图。
在附图中，附图未必按照实际的比例绘制。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壳体
52电极组件
53盖板
10负极极片
11负极集流体
121第一负极膜层
122第二负极膜层
1221第一表面
1222第二表面。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的负极极片、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)。
二次电池
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、隔离膜及电解质。在二次电池充放电过程中，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。电解质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。
[负极极片]
二次电池充电时，锂离子从正极脱出并嵌入负极，但是二次电池面临大倍率充 电、过度充电时，容易出现负极嵌入空间不足、锂离子从正极过快脱出但无法等量嵌入负极等情况，无法及时嵌入负极的锂离子只能在负极极片表面得到电子并还原形成锂金属，这就是析锂现象。同时，二次电池面临大倍率充电、过度充电时，负极极化较大，当负极极片表面电势持续降低并低于Li/Li +参考电极电位时，锂离子会在负极极片表面得到电子并还原形成锂金属。析锂不仅使二次电池性能下降，例如循环寿命大幅缩短，并且析锂现象持续发生后，锂金属会生长成像树枝一样的结构，即锂枝晶。锂枝晶的生长会破坏负极活性材料表面的固体电解质界面(SEI)膜，造成活性离子的不可逆消耗；锂枝晶的生长还会刺穿隔离膜造成内短路，有可能引起燃烧、爆炸等安全风险。发明人发现，析锂主要是由于负极活性材料通常为嵌锂型材料，这些嵌锂型材料的嵌锂速度较低，难以满足二次电池大倍率充电需求；另外，二次电池过度充电时，这些嵌锂型材料也难以阻止锂金属在负极极片表面生成，导致二次电池的安全风险较高。
为了解决二次电池在大倍率充电及过度充电条件下产生的析锂问题以及由此带来的二次电池循环寿命缩短、安全风险升高等问题，发明人进一步进行了大量的研究，提供了一种负极极片，其能有效抑制锂金属在负极极片表面析出，显著改善二次电池的动力学性能、循环性能和安全性能，尤其是改善二次电池在大倍率充电及过度充电条件下的循环性能和安全性能。
本申请的负极极片包括负极集流体以及设置在所述负极集流体上的负极膜层，负极膜层包括第一负极膜层以及第二负极膜层，第二负极膜层位于负极集流体和第一负极膜层之间。第二负极膜层包含金属元素M，且M的原子半径r M与Li的原子半径r Li满足
Figure PCTCN2021114579-appb-000004
本申请的负极膜层具有多层结构，第二负极膜层包含金属元素M，M与Li的原子半径相差较小、晶格错配度较小，这样，Li更容易在M的表面发生固溶。发明人发现，Li在M的表面固溶后，形成的固溶体的晶体结构与Li的晶体结构相似，由此Li在M表面的形核界面能较低。界面能是形核阻力来源，当M的表面形核阻力更低时，M的表面可以作为锂金属的优先形核位点，诱导锂金属在M的表面析出，而不是在负极极片的表面析出。
当二次电池面临大倍率充电、过度充电时，负极极化较大，当负极极片表面电势将要低至析锂过电势时，因为第二负极膜层包含的M的表面形核阻力更低，其表面析锂过电势比负极极片表面电势更低，因此，可以作为锂金属的优先形核位点，诱导锂金属在第二负极膜层M的表面析出，有效抑制锂金属在负极极片表面析出，提升二次电池的动力学性能、循环性能和安全性能。
M与Li的原子半径相差较小时，M晶格结构与Li的晶格结构更匹配，Li更容易在M的表面诱导形核，因此能具有更好的抑制锂金属在负极极片表面析出的效果。M与Li的原子半径相差较大，例如大于12％，M与Li的晶格错配度较大，M的表面不能作为锂金属的优先形核位点，不能起到诱导锂金属在第二负极膜层中M的表面优先形核的效果。当二次电池大倍率充电、过度充电时，锂金属仍会在负极极片表面析出，二次电池的安全性能得不到有效保障。
本申请的负极极片可以实现常规负极活性材料在大倍率充电及过度充电条件下的安全使用；本申请的负极极片可以有效抑制锂金属在负极极片表面析出，因此二次电池 不仅具有良好的动力学性能，还具有显著改善的循环寿命。
在本申请中，金属元素M以及Li的原子半径可参考《兰氏化学手册》(Lange's handbook of chemistry)。
在一些实施方式中，M的原子半径r M与Li的原子半径r Li满足
Figure PCTCN2021114579-appb-000005
Figure PCTCN2021114579-appb-000006
M与Li的原子半径之差控制在合适的范围内，能够更有效抑制锂金属在负极极片表面析出，进一步提升二次电池的动力学性能、循环性能和安全性能。
在一些实施方式中，基于第一负极膜层的总质量，M的质量百分含量≤0.5％。可选地，第一负极膜层不包含金属元素M。
第一负极膜层不含或基本不含金属元素M时，能够有效确保锂金属优先在第二负极膜层M表面析出，进一步抑制锂金属在负极极片表面析出。同时，锂金属优先在第二负极膜层M表面析出，第二负极膜层表面的第一负极膜层还能起到抑制锂枝晶快速生长的效果，从而进一步延长二次电池的循环寿命。
在一些实施方式中，基于第二负极膜层的总质量，M的质量百分含量为1％～10％。可选地，M的质量百分含量为1％～9％，1％～8％，1％～7％，1％～6％，1％～5％，1％～4％，2％～9％，2％～8％，2％～7％，2％～6％，2％～5％，2％～4％，3％～9％，3％～8％，3％～7％，3％～6％，3％～5％，3％～4％，3.5％～9％，3.5％～8％，3.5％～7％，3.5％～6％，3.5％～5％，或3.5％～4.5％。
M的质量百分含量较低时，第二负极膜层具有的形核位点数量较少，当二次电池面临大倍率充电、过度充电时，第二负极膜层抑制锂金属在负极极片表面析出的作用不明显。M的质量百分含量较高时，对电解液的消耗也增加，且由于Li在M的表面发生固溶后M的体积膨胀，第二负极膜层以及负极极片的体积膨胀会变大，二次电池的循环寿命会有一定程度的缩短。M的质量百分含量在合适的范围内，能够在有效抑制锂金属在负极极片表面析出的同时，有效抑制二次电池循环寿命的缩短。
在一些实施方式中，M选自Sn、Bi、Cd、Ti、Nb、Ta、Sb、Hf、Mg、Zr、Ag、Au、Al、Sc、Mo、W、Pt、Pd、In、Re、Ir、Ga、Os、V、Zn、Ru、Rh中的一种或几种。可选地，M选自Sn、Bi、Cd、Ti、Nb、Ta、Sb、Hf、Mg、Zr、Ag、Au、Al中的一种或几种。进一步可选地，M选自Nb、Au、Ag、Al、Mg、Ti、Cd、Zr中的一种或几种。
M选自上述金属元素时，其晶格结构与Li的晶格结构更匹配，Li更容易在M表面诱导形核，因此具有更好的抑制锂金属在负极极片表面析出的效果，进一步提升二次电池的动力学性能、循环性能和安全性能。
在一些实施方式中，第二负极膜层包括主体部、以及沿自身厚度方向相对的第一表面和第二表面，第一表面背向负极集流体设置，第二表面朝向负极集流体设置。M位于第二负极膜层的主体部、第二负极膜层背向负极集流体的第一表面、第二负极膜层朝向负极集流体的第二表面中的一个或多个位置。例如，(1)M仅位于负极膜层的主体部，(2)M仅位于第二负极膜层背向负极集流体的第一表面，(3)M仅位于第二负极膜层朝向负极集流体的第二表面，(4)M同时位于负极膜层的主体部、第二负极膜层背向负极集流体的第一表面两个位置，(5)M同时位于负极膜层的主体部、第二负极膜层朝向负极集流体的第二表面两个位置，(6)M同时位于第二负极膜层背向负极集流体的 第一表面、第二负极膜层朝向负极集流体的第二表面两个位置，(7)M同时位于负极膜层的主体部、第二负极膜层背向负极集流体的第一表面、第二负极膜层朝向负极集流体的第二表面三个位置。
在一些实施方式中，M至少位于第二负极膜层的主体部。
在一些实施方式中，当M位于第二负极膜层背向负极集流体的第一表面时，M可在第二负极膜层的第一表面位置形成层状结构。可选地，层状结构不连续。例如，M在第二负极膜层的第一表面位置呈间隔分布或阵列分布。此时，一方面有利于电解液充分浸润第二负极膜层，另一方面有利于二次电池充电时来自正极的锂离子顺利嵌入第二负极膜层以及二次电池放电时第二负极膜层嵌入的锂离子充分脱出并顺利迁移至正极。
在一些实施方式中，M位于第二负极膜层朝向负极集流体的第二表面时，M可在第二负极膜层的第二表面位置形成层状结构。可选地，层状结构不连续。例如，M在第二负极膜层的第二表面呈间隔分布或阵列分布。此时，一方面有利于第二负极膜层与负极集流体保持较高的粘结强度，防止掉粉，另一方面有利于来自电子的传导。
在一些实施方式中，第一负极膜层与第二负极膜层的涂布重量比为0.3～1.2。可选地，第一负极膜层与第二负极膜层的涂布重量比为0.3～1，0.4～1，0.5～1，0.3～0.8，0.4～0.8，0.5～0.8，0.3～0.7，0.4～0.7，0.5～0.7，0.3～0.6，0.4～0.6，或0.5～0.6。
第一负极膜层与第二负极膜层的涂布重量比较大时，第二负极膜层的形核位点相对较少，抑制锂金属在负极极片表面析出的效果不明显。第一负极膜层与第二负极膜层的涂布重量比较小时，第一负极膜层的厚度相对较小，第二负极膜层形成的锂枝晶更容易穿过第一负极膜层到达负极极片表面，电池内短路的风险增加。第一负极膜层与第二负极膜层的涂布重量比在合适的范围内，不仅能够有效抑制锂金属在负极极片表面析出，还能够有效抑制锂枝晶到达负极极片表面。
在一些实施方式中，第二负极膜层可包括金属颗粒，金属颗粒选自M的单质颗粒、M的合金颗粒中的一种或几种。
在一些实施方式中，M的合金包括M中的两种以上的元素形成的合金、以及M中的一种或几种元素与另一金属元素M 1中的一种或几种元素形成的合金。可选地，M的合金包括M中的两种以上的元素形成的合金。
在一些实施方式中，M 1包括Fe、Cu、Ni、Cr、Mn中的一种或几种。
在一些实施方式中，金属颗粒的体积平均粒径Dv50≤5μm。可选地，金属颗粒的体积平均粒径Dv50≤1μm。更具体地，金属颗粒的体积平均粒径Dv50≤0.5μm。
金属颗粒的体积平均粒径Dv50控制在合适的范围内，可以在第二负极膜层中形成足够数量的形核位点，进而有效抑制锂金属在负极极片表面析出。
在本申请中，材料的体积平均粒径Dv50为本领域公知的含义，可采用本领域已知的方法和仪器测定。例如，可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)测定。
在一些实施方式中，第二负极膜层可包括Li-M合金颗粒、Li-M-M 1合金颗粒中的一种或几种，M 1表示金属元素，且M 1包括Fe、Cu、Ni、Cr、Mn中的一种或几种。Li-M合金表示Li与金属元素M中的一种或几种形成的合金，Li-M-M 1合金表示Li与金属元素M中的一种或几种以及金属元素M 1中的一种或几种形成的合金。
作为示例，Li-M合金为Li-Sn、Li-Bi、Li-Cd、Li-Ti、Li-Nb、Li-Ta、Li-Sb、Li-Hf、Li-Mg、Li-Zr、Li-Ag、Li-Au、Li-Al、Li-Sc、Li-Mo、Li-W、Li-Pt、Li-Pd、Li-In、Li-Re、Li-Ir、Li-Ga、Li-Os、Li-V、Li-Zn、Li-Ru、Li-Rh、Li-Mg-Al、Li-Mg-Zr、Li-Mg-Zn、Li-Ag-Al、Li-Ag-Zn、Li-Ag-Mg、Li-Ti-Al中的一种或几种。
作为示例，Li-M-M 1合金选自Li-Mg-Mn、Li-Al-Mn、Li-Al-Fe、Li-Al-Cu、Li-Ti-Ni、Li-Ti-Cr中的一种或几种。
在一些实施方式中，第二负极膜层除包括上述金属颗粒、Li-M合金颗粒、Li-M-M 1合金颗粒中的一种或几种外，还可包括第二负极活性材料、可选的导电剂、可选的粘结剂以及其它可选助剂。
在一些实施方式中，第一负极膜层包括第一负极活性材料、可选的导电剂、可选的粘结剂以及其它可选助剂。
在一些实施方式中，第一负极活性材料和第二负极活性材料的种类并不受到具体的限制，可采用本领域公知的用于二次电池的负极活性材料。第一负极活性材料和第二负极活性材料种类可以相同，也可以不同。作为示例，第一负极活性材料和第二负极活性材料各自独立地包括石墨、软碳、硬碳、中间相碳微球、碳纤维、碳纳米管、硅基材料、锡基材料、钛酸锂中的一种或几种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或几种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。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。
在一些实施方式中，导电剂以及粘结剂的种类和含量并不受具体的限制，可根据实际需求进行选择。第一负极膜层和第二负极膜层的导电剂种类可以相同，也可以不同，作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑等)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。第一负极膜层和第二负极膜层的粘结剂种类可以相同，也可以不同，作为示例，粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)及羧甲基壳聚糖(CMCS)中的一种或几种。第一负极膜层和第二负极膜层的其它可选助剂种类可以相同，也可以不同，作为示例，其他可选助剂可包括增稠剂(例如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
在本申请的负极极片中，负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(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。
在一些实施方式中，负极膜层设置在负极集流体的至少一个表面上。例如，负极集流体具有在自身厚度方向相对的两个表面，负极膜层设置于负极集流体相对的两个表面的其中任意一者或两者上。
图1示出了本申请的负极极片10的一种实施方式的示意图。负极极片10可由负极集流体11、分别设置在负极集流体11两侧的第二负极膜层122和设置在第二负极膜层122上的第一负极膜层121构成，第二负极膜层122位于负极集流体11和第一负极膜层121之间。第二负极膜层122沿自身厚度方向包括相对的第一表面1221和第二表面1222，第一表面1221背向负极集流体11设置，第二表面1222朝向负极集流体11设置。
当然，本申请的负极极片10也可具有其他的实施方式，例如，负极极片10由负极集流体11、设置在负极集流体其中一侧的第二负极膜层122和设置在第二负极膜层122上的第一负极膜层121构成。
另外，本申请的负极极片并不排除除了负极膜层之外的其他附加功能层。例如在一些实施方式中，本申请的负极极片还可以包括设置在负极集流体和第二负极膜层之间的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还包括覆盖在第一负极膜层表面的保护层。
在一些实施方式中，本申请的负极极片的制备方法可包括如下步骤：在负极集流体的至少一侧形成第二负极膜层，第二负极膜层包括金属颗粒，金属颗粒选自M的单质颗粒、M的合金颗粒中的一种或几种；在第二负极膜层的表面上形成第一负极膜层。
负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料通常是将负极活性材料以及可选的导电剂、可选的粘结剂、其它可选助剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。在一些实施方式中，可以将第一负极活性材料、可选的导电剂、可选的粘结剂、其它可选助剂分散于溶剂中并搅拌均匀形成第一负极浆料，将第二负极活性材料、金属颗粒、可选的导电剂、可选的粘结剂、其它可选助剂分散于溶剂中并搅拌均匀形成第二负极浆料。
在负极极片的制备方法中，第一负极浆料和第二负极浆料可以一次同时涂布，也可以分两次涂布。
在一些实施方式中，第一负极浆料和第二负极浆料一次同时涂布。一次同时涂布可以使第一负极膜层和第二负极膜层之间的粘结性更好，有助于降低负极膜层整体的界面电阻，进一步改善电池的循环性能。
在一些实施方式中，负极极片的制备方法可包括如下步骤：在负极集流体的至少一侧形成第二负极膜层，在第二负极膜层的表面上形成一层金属M，之后继续形成第一负极膜层，经冷压后，M位于第二负极膜层背向负极集流体的第一表面上。可选地，金属M的层状结构为不连续形态，例如，为间隔分布状态或阵列分布状态。在第二负极膜层的表面上形成金属M的方法包括涂布、喷丸、喷洒、气相沉积等，但不限于此。例如采用气相沉积法将金属M沉积于第二负极膜层的表面上。气相沉积法可以是原子层沉积法、化学气相沉积法及物理气相沉积法中的一种或多种。
在一些实施方式中，负极极片的制备方法可包括如下步骤：在负极集流体的至少一侧形成一层金属M，之后在负极集流体表面上形成第二负极膜层，再在第二负极膜层的表面上形成第一负极膜层，经冷压后，M位于第二负极膜层朝向负极集流体的第二表面上。可选地，金属M的层状结构为不连续形态，例如，为间隔分布状态或阵列分布状态。在负极集流体的表面上形成金属M的方法包括涂布、气相沉积、凹版工艺等，但不 限于此。例如采用气相沉积法将金属M沉积于负极集流体的表面上。气相沉积法可以是原子层沉积法、化学气相沉积法及物理气相沉积法中的一种或多种。
第二负极膜层中M的质量百分含量测试可通过如下的方法得到。
通过使用扫描电子显微镜(例如ZEISS Sigma 300)得到第一负极膜层和第二负极膜层各自的厚度。首先将负极极片裁成一定尺寸的待测样品(例如2cm×2cm)，通过石蜡将负极极片固定在样品台上。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如IB-19500CP)电源和抽真空(例如10 -4Pa)，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光。样品测试可参考JY/T010-1996。为了确保测试结果的准确性，可以在待测样品中随机选取多个(例如5个)不同区域进行扫描测试，并在一定放大倍率(例如500倍)下，读取标尺测试区域中第一负极膜层和第二负极膜层各自的厚度，取多个测试区域的平均值作为测试结果。
由于第二负极膜层中金属元素M的含量较低，对第二负极膜层密度的影响较小，因此认为第一负极膜层和第二负极膜层的密度一致，进而通过第一负极膜层和第二负极膜层的厚度比，可以得到第一负极膜层和第二负极膜层的涂布重量比。
取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜层)，裁成一定尺寸的待测样品(例如2cm×2cm)，然后进行刮粉；将得到的所有粉末用电感耦合等离子体-发射光谱仪(inductively coupled plasma-Optical Emission spectrometers，ICP-OES)测试，得到负极膜层中金属元素M的质量浓度；通过第一负极膜层和第二负极膜层的涂布重量比计算得到第二负极膜层中金属元素M的质量百分含量。为了确保测试结果的准确性，可以将负极极片裁切成多个具有一定尺寸的待测样品(例如5个)，取多个测试样品的平均值作为测试结果。
[正极极片]
二次电池包括正极极片，正极极片通常包括正极集流体以及设置于正极集流体至少一个表面上且包括正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置在正极集流体的两个相对表面中的任意一者或两者上。
在本申请的正极极片中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，正极集流体可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(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。
在本申请的正极极片中，正极膜层包括正极活性材料，正极活性材料可采用本领域公知的用于二次电池的正极活性材料。作为示例，正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合 材料及其各自的改性化合物中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。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。
在本申请的正极极片中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
本申请的正极极片中，正极膜层通常包含正极活性材料以及可选地粘结剂和可选地导电剂。正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂中的一种或几种。作为示例，用于正极膜层的导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或几种。需要说明的是，本申请所给的各正极膜层的组成或参数均指正极集流体单面膜层的组成或参数范围。当正极膜层设置在正极集流体相对的两个表面上时，其中任意一个表面上的正极膜层的组成或参数满足本申请，即认为落入本申请的保护范围内。
[电解质]
电解质在正极极片和负极极片之间起到传导活性离子的作用。本申请的二次电池对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐的种类不受具体的限制，可根据实际需求进行选择。作为示例，电解质盐可选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。
在一些实施方式中，溶剂的种类不受具体的限制，可根据实际需求进行选择。作为示例，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，可选地，溶剂为非水溶剂。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添 加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请对隔离膜的种类没有特别的限制，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，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可相同或不同。
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。
在一些实施方式中，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，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
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。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用于盖设所述开口，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。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几个，可根据需求来调节。
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多个，具体数量可根据电池模块的应用和容量来调节。
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根据电池包的应用和容量进行调节。
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用于盖设下箱体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。
用电装置
本申请的实施方式还提供一种用电装置，所述用电装置包括本申请的二次电池、 电池模块、电池包中的至少一种。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。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
正极极片的制备
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、导电剂乙炔黑、粘结剂聚偏氟乙烯(PVDF)按质量比96:2:2进行混合，加入溶剂N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系呈均一状，获得正极浆料；将正极浆料均匀涂布在正极集流体铝箔上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切，得到正极极片。
负极极片的制备
将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第一负极浆料。
将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ag单质颗粒(体积平均粒径Dv50为0.05μm)按质量比98:2进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。
将第一负极浆料、第二负极浆料一次同时均匀涂布在负极集流体铜箔的两个表面上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切，得到负极极片。第二负极膜层位于负极集流体和第一负极膜层之间，第一负极膜层的涂布重量为4.3mg/cm 2，第二负极膜层涂布重量为6.7mg/cm 2。Ag单质颗粒在第二负极膜层中的质量占比为2％。
电解液的制备
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行混合得到有机溶剂，接着将充分干燥的锂盐LiPF 6溶解于上述有机溶剂中， 配制成浓度为1mol/L的电解液。
隔离膜的制备
使用聚乙烯膜作为隔离膜。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
实施例2
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ag单质颗粒(体积平均粒径Dv50为0.05μm)按质量比97:3进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Ag单质颗粒在第二负极膜层中的质量占比为3％。
实施例3
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ag单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Ag单质颗粒在第二负极膜层中的质量占比为5％。
实施例4
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ag单质颗粒(体积平均粒径Dv50为0.05μm)按质量比90:10进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Ag单质颗粒在第二负极膜层中的质量占比为10％。
实施例5
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Al单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Al单质颗粒在第二负极膜层中的质量占比为5％。
实施例6
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Mg单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Mg单质颗粒在第二负极膜层中的质量占比为5％。
实施例7
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂 乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Nb单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Nb单质颗粒在第二负极膜层中的质量占比为5％。
对比例1
二次电池的制备方法与实施例1类似，不同之处在于负极极片的制备过程，具体包括如下步骤。
将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得负极浆料，将负极浆料分成两份，分别作为第一负极浆料和第二负极浆料。将第一负极浆料、第二负极浆料一次同时均匀涂布在负极集流体铜箔的两个表面上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切，得到负极极片。第二负极膜层位于负极集流体和第一负极膜层之间，第一负极膜层的涂布重量为4.3mg/cm 2，第二负极膜层涂布重量为6.7mg/cm 2。
对比例2
二次电池的制备方法与实施例1类似，不同之处在于负极极片的制备过程，具体包括如下步骤。
将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ag单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得负极浆料。将负极浆料均匀涂布在负极集流体铜箔的两个表面上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切，得到负极极片。负极膜层的涂布重量为11.0mg/cm 2。
对比例3
二次电池的制备方法与实施例1类似，不同之处在于负极极片的制备过程，具体包括如下步骤。
将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ag单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第一负极浆料。
将负极活性材料石墨、导电剂乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。
将第一负极浆料、第二负极浆料一次同时均匀涂布在负极集流体铜箔的两个表面上，室温晾干后转移至烘箱继续干燥，然后经过冷压、分切，得到负极极片。第二负极膜层位于负极集流体和第一负极膜层之间，第一负极膜层的涂布重量为4.3mg/cm 2，第二负极膜层涂布重量为6.7mg/cm 2。Ag单质颗粒在第一负极膜层中的质量占比为5％。
对比例4
二次电池的制备方法与实施例1类似，不同的是：将负极活性材料石墨、导电剂 乙炔黑、增稠剂羧甲基纤维素钠(CMC-Na)、粘结剂丁苯橡胶(SBR)按质量比96.4:1:1.2:1.4混合后，再与Ni单质颗粒(体积平均粒径Dv50为0.05μm)按质量比95:5进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得第二负极浆料。Nb单质颗粒在第二负极膜层中的质量占比为5％。
测试部分
(1)二次电池的最大充电倍率测试
在25℃下，将二次电池以1C倍率恒流放电至2.8V。然后以1C倍率恒流充电至4.2V，继续恒压充电至电流为0.05C，此时二次电池为满充状态。将满充的二次电池静置5min后，以1C倍率恒流放电至2.8V，此时的放电容量为二次电池的1C倍率下的实际容量，记为C0。将二次电池在x C0倍率(表示梯度充电倍率，1C0、1.1C0、1.2C0、1.3C0、1.4C0……)下恒流充电至4.2V，再继续恒压充电至电流为0.05C0，静置5min，拆解二次电池观察负极极片表面析锂情况。如果负极极片表面未析锂，则增大充电倍率再次进行测试，直至负极极片表面析锂。记录负极极片表面未析锂的最大充电倍率。
(2)二次电池的过充性能测试
在25℃下，将二次电池以1C倍率恒流放电至2.8V。然后以1C倍率恒流充电，设计梯度的充电时间1h、1.1h、1.2h、1.3h、1.4h……。将每次充电后二次电池拆解，观察负极极片表面析锂情况，记录负极极片表面刚开始析锂时的充电时间t(h)。用充电时间t×100％，表示二次电池过充至开始析锂的SOC态。
(3)二次电池的循环性能测试
在25℃下，将二次电池以1C倍率恒流放电至2.8V。然后将二次电池以1C倍率恒流充电至4.2V，继续恒压充电至电流为0.05C，此时二次电池为满充状态，记录此时的充电容量，即为第1圈充电容量；将二次电池静置5min后以1C倍率恒流放电至2.8V，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量，直至二次电池的放电容量衰减为第1圈放电容量的80％，用此时的循环圈数表征二次电池在1C倍率条件下的循环性能。二次电池的循环圈数越高，循环性能越好。
在25℃下，将二次电池以1C倍率恒流放电至2.8V。然后将二次电池以3C倍率恒流充电至4.2V，继续恒压充电至电流为0.05C，此时二次电池为满充状态，记录此时的充电容量，即为第1圈充电容量；将二次电池静置5min后以3C倍率恒流放电至2.8V，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量，直至二次电池的放电容量衰减为第1圈放电容量的80％，用此时的循环圈数表征二次电池在3C倍率条件下的循环性能。二次电池的循环圈数越高，循环性能越好。
实施例1～7和对比例1～4的具体参数详见表1，测试结果详见表2。
表1
Figure PCTCN2021114579-appb-000007
Figure PCTCN2021114579-appb-000008
表2
Figure PCTCN2021114579-appb-000009
由表2的数据可知，本申请的二次电池的最大充电倍率更高、过充性能更好，能有效解决二次电池在大倍率充电及过度充电条件下产生的析锂问题，并显著改善二次电池的动力学性能、循环性能和安全性能。图8是实施例1制备的负极极片的断面扫描电镜图，从图8可以看出Ag单质颗粒均匀分布在第二负极膜层的主体部中，Ag的表面作为锂金属的优先形核位点，能起到诱导锂金属在第二负极膜层中Ag的表面形核的效果，有效抑制锂金属在负极极片表面析出，因此，二次电池在大倍率充电及过度充电条件下仍具有良好的动力学性能及安全性能，同时二次电池的循环性能也更好。
对比例1的负极膜层中未添加金属颗粒，负极膜层不含形核位点，因此不能有效抑制锂金属在负极极片表面析出，二次电池在大倍率充电及过度充电条件的动力学性能和循环性能均较差。
对比例2的负极膜层为单层，且负极膜层中添加了Ag单质颗粒，Ag的表面可以作为锂金属的优先形核位点，但是由于Ag单质颗粒是均匀分布在负极膜层中，并不能起到抑制锂金属在负极极片表面析出的作用，因此，二次电池在大倍率充电及过度充电条件的动力学性能和循环性能均较差。对比例3的第二负极膜层中未添加金属颗粒，第一负极膜层中添加了Ag单质颗粒，Ag的表面可以作为锂金属的优先形核位点，但是由于Ag单质颗粒是均匀分布在第一负极膜层中，并不能起到抑制锂金属在负极极片表面析出的作用，因此，二次电池在大倍率充电及过度充电条件的动力学性能和循环性能均较差。
对比例4在第二负极膜层添加的金属颗粒为Ni单质颗粒，Ni与Li的原子半径相差过大，Ni的表面不能作为Li的优先形核位点，不能起到诱导Li在第二负极膜层中Ni的表面形核的效果，不能有效抑制锂金属在负极极片表面析出，二次电池在大倍率充电及过度充电条件下的动力学性能很差，同时二次电池也难以具有更长的循环寿命。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (16)

  1. 一种负极极片，包括
    负极集流体；以及
    设置在所述负极集流体上的负极膜层，所述负极膜层包括第一负极膜层以及第二负极膜层，所述第二负极膜层位于所述负极集流体(11)和所述第一负极膜层之间，所述第二负极膜层包含金属元素M，且M的原子半径r M与Li的原子半径r Li满足
    Figure PCTCN2021114579-appb-100001
    Figure PCTCN2021114579-appb-100002
    可选地，
    Figure PCTCN2021114579-appb-100003
  2. 根据权利要求1所述的负极极片，其中，M选自Sn、Bi、Cd、Ti、Nb、Ta、Sb、Hf、Mg、Zr、Ag、Au、Al、Sc、Mo、W、Pt、Pd、In、Re、Ir、Ga、Os、V、Zn、Ru、Rh中的一种或几种，可选地，M选自Sn、Bi、Cd、Ti、Nb、Ta、Sb、Hf、Mg、Zr、Ag、Au、Al中的一种或几种。
  3. 根据权利要求1-2任一项所述的负极极片，M至少位于第二负极膜层的主体部。
  4. 根据权利要求1-3任一项所述的负极极片，其中，
    所述第二负极膜层沿自身厚度方向包括相对的第一表面和第二表面，第一表面背向所述负极集流体设置，第二表面朝向所述负极集流体设置，
    M位于第二负极膜层背向负极集流体的第一表面和/或第二负极膜层朝向负极集流体的第二表面。
  5. 根据权利要求1-4任一项所述的负极极片，其中，基于第二负极膜层的总质量，M的质量百分含量为3％～7％，可选地为3％～5％。
  6. 根据权利要求1-5任一项所述的负极极片，其中，基于第一负极膜层的总质量，M的质量百分含量≤0.5％。
  7. 根据权利要求1-6任一项所述的负极极片，其中，第一负极膜层不包含金属元素M。
  8. 根据权利要求1-7任一项所述的负极极片，其中，第一负极膜层与第二负极膜层的涂布重量比为0.3～1.2，可选地为0.5～0.8。
  9. 根据权利要求1-8任一项所述的负极极片，其中，第二负极膜层包括金属颗粒，金属颗粒选自M的单质颗粒、M的合金颗粒中的一种或几种。
  10. 根据权利要求9所述的负极极片，其中，M的合金包括M中的两种以上的元素形成的合金、以及M中的一种或几种元素与另一金属元素M 1中的一种或几种元素形成的合金，可选地M 1包括Fe、Cu、Ni、Cr、Mn中的一种或几种。
  11. 根据权利要求9-10任一项所述的负极极片，其中，金属颗粒的体积平均粒径Dv50≤5μm，可选地≤1μm。
  12. 根据权利要求1-11任一项所述的负极极片，其中，第二负极膜层包括Li-M合金颗粒、Li-M-M 1合金颗粒中的一种或几种，M 1表示金属元素，且M 1包括Fe、Cu、Ni、Cr、Mn中的一种或几种。
  13. 一种二次电池，包括根据权利要求1-12任一项所述的负极极片。
  14. 一种电池模块，包括根据权利要求13所述的二次电池。
  15. 一种电池包，包括根据权利要求13所述的二次电池、根据权利要求14所述的电池模块中的一种。
  16. 一种用电装置，包括根据权利要求13所述的二次电池、根据权利要求14所述的电池模块、根据权利要求15所述的电池包中的至少一种。
PCT/CN2021/114579 2021-08-25 2021-08-25 负极极片、二次电池、电池模块、电池包和用电装置 WO2023023984A1 (zh)

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