WO2022105614A1 - 锂金属负极、其制备方法及其相关的锂金属电池和装置 - Google Patents

锂金属负极、其制备方法及其相关的锂金属电池和装置 Download PDF

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WO2022105614A1
WO2022105614A1 PCT/CN2021/128641 CN2021128641W WO2022105614A1 WO 2022105614 A1 WO2022105614 A1 WO 2022105614A1 CN 2021128641 W CN2021128641 W CN 2021128641W WO 2022105614 A1 WO2022105614 A1 WO 2022105614A1
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lithium
negative electrode
lithium metal
battery
optionally
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PCT/CN2021/128641
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English (en)
French (fr)
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刘成勇
程萌
符昂
胡波兵
郭永胜
范铨
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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 EP21893761.3A priority Critical patent/EP4131494A4/en
Priority to JP2022558231A priority patent/JP7459288B2/ja
Priority to KR1020227033419A priority patent/KR20220147117A/ko
Publication of WO2022105614A1 publication Critical patent/WO2022105614A1/zh
Priority to US18/125,174 priority patent/US20230223545A1/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
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • 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
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H—ELECTRICITY
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    • 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
    • H01M4/38—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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
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    • 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
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    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, in particular to a lithium metal negative electrode, a preparation method thereof, and a related lithium metal battery and device.
  • Lithium-ion batteries have the advantages of high specific energy, long life and low cost, so they are widely used. For example, with the increasingly prominent environmental and energy problems, there is an urgent need for the development of new energy electric vehicles, which has led to the vigorous development of lithium-ion batteries as a new energy system.
  • lithium-ion battery as an energy source has a higher energy density.
  • Metal lithium has a very high theoretical specific capacity (3860mAh/g) and the lowest reduction potential (-3.04V vs standard hydrogen electrode), so lithium metal anode is expected to become the next-generation high-energy density lithium-ion battery.
  • lithium-ion battery also called a lithium metal battery
  • a lithium metal negative electrode is likely to cause internal short circuits, which has a great potential safety hazard. Therefore, how to improve the safety performance of lithium metal batteries has become a key challenge in the field of lithium metal batteries.
  • a first aspect of the present application provides a lithium metal negative electrode, comprising: a negative electrode current collector; at least one lithium-based metal layer disposed on at least one surface of the negative electrode current collector; and an ion-conducting polymer modified layer, the polymer modified layer
  • the layer is on the surface of the at least one lithium-based metal layer and includes at least a catalytic amount of a Lewis acid that includes a cation of a metal capable of forming an alloy-based active material with lithium.
  • an ion-conducting polymer modified layer is formed on the surface of the lithium-based metal layer catalyzed by a Lewis acid, and the Lewis acid contains metal cations, and the metal can form an alloy-based active material with lithium.
  • the dual role of lithium metal and alloy can effectively control the uniform deposition of lithium on the surface of lithium metal negative electrode, and inhibit the growth of lithium dendrites, thereby greatly reducing the risk of internal short circuit in lithium metal batteries and improving safety performance.
  • the thickness of the polymer modification layer may be 100 nm to 10 ⁇ m, optionally 300 nm to 5 ⁇ m, and further optionally 500 nm to 3 ⁇ m.
  • the polymer modification layer has an appropriate thickness, which can effectively improve the safety performance of the battery and improve the cycle performance of the battery.
  • the battery is also beneficial to obtain higher energy density.
  • the Lewis acid may be selected from one or more of the compounds represented by the formula (1): An L m ( 1), wherein A represents Al, Zn, Mg, Pb, Ge , Sn or Sb cation, optionally, A represents Al or Zn cation; L independently represents F-, Cl-, Br-, I- or the anion represented by formula (2),
  • L may represent F ⁇ , Cl ⁇ , Br ⁇ , I ⁇ , [(FSO 2 ) 2 N] ⁇ , [(CF 3 SO 2 ) 2 N] ⁇ , [(FSO 2 ) (CF 3 SO 2 )N] ⁇ , [(FSO 2 )(C 2 F 5 SO 2 )N] ⁇ , or [(FSO 2 )(C 4 F 9 SO 2 )N] ⁇ .
  • the Lewis acid may be selected from one or more of AlCl 3 , ZnCl 2 , Al[(FSO 2 ) 2 N] 3 and Zn[(FSO 2 ) 2 N] 2 .
  • the compressive elastic modulus of the polymer modification layer may be 0.01 MPa to 1 MPa, and optionally 0.02 MPa to 0.78 MPa.
  • the polymer modification layer is flexible, which can further improve the interface contact between the lithium metal anode and the separator or solid electrolyte membrane (such as inorganic solid electrolyte membrane), thus further improving the deposition/dissolution behavior of lithium, which can further improve the safety performance of the battery and cycle performance.
  • the polymer may include one or more of polyether, polyester and polyimine.
  • the polymer includes one or more of polycarbonate, polysulfate, polysulfite and polysulfonate.
  • the modification layer can obtain appropriate mechanical strength and flexibility by using a suitable polymer, which can further improve the safety performance of the battery.
  • the polymer modified layer is obtained by in-situ polymerization of monomers on the surface of the lithium-based metal layer under the catalysis of Lewis acid.
  • surface in-situ polymerization it is convenient to control the thickness of the modified layer within a desired range.
  • the monomers may include one or more of cyclic carbonates, cyclic sulfonates, cyclic sulfates, cyclic sulfites, and halogenated derivatives thereof.
  • the monomers include one or more of cyclic carbonates and their halogenated derivatives.
  • the monomer may include one or more of ethylene carbonate, propylene carbonate and their halogenated derivatives.
  • the monomer includes one or more of ethylene carbonate and fluoroethylene carbonate.
  • the monomer includes fluoroethylene carbonate.
  • the polymer modification layer may further include a lithium salt.
  • the weight proportion of the lithium salt in the polymer modification layer is ⁇ 60%, optionally 10% to 40%.
  • the lithium salt may include LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiBOB, LiDFOB, LiTFOP, LiN(SO 2 R F ) 2 and LiN(SO 2 F )(SO 2 R F ), wherein R F represents C n F 2n+1 , and n is an integer of 0-10.
  • the lithium salt includes one or more of LiN(SO 2 F) 2 , LiDFOB, and LiN(SO 2 F)(SO 2 CF 3 ). Appropriate lithium salts can make the modified layer obtain a good film-forming effect, thereby further improving the cycle performance of the battery.
  • the polymer modified layer may further include inorganic fillers.
  • the weight proportion of the inorganic filler in the modification layer is less than or equal to 10%.
  • the weight proportion of the inorganic filler in the modification layer is 1% to 5%. The inclusion of inorganic fillers in the polymer modified layer can further improve the cycle performance of the battery.
  • the inorganic filler may include silicon dioxide (SiO 2 ), titanium oxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO), zirconium oxide (ZrO 2 ), oxide Zinc (ZnO), iron oxide (Fe 3 O 4 ), barium titanate (BaTiO 3 ), lead titanate (PbTiO 3 ), lithium nitride (Li 3 N), lithium aluminate (LiAlO 2 ), montmorillonite and one or more of molecular sieves.
  • the volume average particle diameter D v 50 of the inorganic filler is 50 nm to 1000 nm, optionally 100 nm to 800 nm.
  • the particle size of the inorganic filler is in an appropriate range, which can further improve the battery cycle life.
  • a second aspect of the present application provides a method for preparing a lithium metal negative electrode, comprising the following steps:
  • a lithium metal negative electrode to be modified is provided, and the lithium metal negative electrode to be modified includes a negative electrode current collector and a lithium-based metal layer disposed on at least one surface of the negative electrode current collector;
  • the mixed solution comprising a Lewis acid and a monomer, the Lewis acid comprising a cation of a metal capable of forming an alloy-based active material with lithium;
  • the mixed solution is made to cover the surface of at least one lithium-based metal layer, and the Lewis acid catalyzes the polymerization of the monomer to form an ion-conducting polymer modified layer to obtain a lithium metal negative electrode.
  • the weight part of the Lewis acid may be 1-35, optionally 3-30, and further optionally 10-20.
  • the proper ratio of Lewis acid to monomer can enable the modified layer to obtain good strength and flexibility, so that it can effectively inhibit short circuit and improve the safety performance of the battery.
  • keeping the ratio of Lewis acid to monomer in an appropriate range is also conducive to improving the cycle life of the battery, and can also enable the battery to obtain a higher first-week discharge specific capacity and first-week Coulombic efficiency.
  • the mixed solution further includes a reaction moderator.
  • the weight part of the reaction moderator may be greater than 0 and less than or equal to 800, and optionally 100-200.
  • the reaction moderator can control the reaction rate and make the reaction proceed under mild conditions.
  • the obtained polymer modified layer can be a colloidal elastic film layer with good quality, which can effectively improve the safety performance and cycle performance of the battery.
  • the reaction moderator may include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate , methyl butyrate, ethyl acetate, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, methyl sulfide, diethyl sulfite, sulfoxide
  • dimethyl sulfate, tetrahydrofuran, cyclic ester shown in formula (I) optionally including in dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate one or more of;
  • R 1 and R 2 independently represent H, F, or a fluoroalkyl group having 1 to 4 carbon atoms
  • R 3 represents a fluoroalkylene group having 1 to 3 carbon atoms.
  • the mixed solution may further include a lithium salt.
  • the content of the lithium salt may be 200 parts by weight or less based on 100 parts by weight of the monomer.
  • the content of the lithium salt is 30-80 parts by weight based on 100 parts by weight of the monomer.
  • the mixed solution may further include inorganic fillers.
  • the content of the inorganic filler may be 30 parts by weight or less based on 100 parts by weight of the monomer.
  • the content of the inorganic filler is 10-20 parts by weight based on 100 parts by weight of the monomer.
  • a third aspect of the present application provides a lithium metal battery, which includes a positive pole piece and a negative pole piece, wherein the negative pole piece is the lithium metal negative pole provided by the application. Since the lithium metal battery of the present application adopts the lithium metal negative electrode of the present application, high safety performance can be obtained.
  • a fourth aspect of the present application provides an apparatus comprising a lithium metal battery according to the first aspect of the present application.
  • the device of the present application includes the lithium metal battery, and thus has at least the same advantages as the lithium metal battery.
  • FIG. 1 is a scanning electron microscope (SEM) image of a lithium metal negative electrode provided in an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a lithium metal battery provided in an embodiment of the present application.
  • FIG. 3 is an exploded view of FIG. 2 .
  • FIG. 4 is a schematic diagram of a battery module provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a battery pack provided by an embodiment of the present application.
  • FIG. 6 is an exploded view of FIG. 5 .
  • FIG. 7 is a schematic diagram of an apparatus provided by an embodiment of the present application.
  • FIG. 8 is a cycle graph of the Li/Li symmetric lithium metal battery of Example 1 and Comparative Example 1 of the present application.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • every point or single value between the endpoints of a range is included within the range, even if not expressly recited.
  • each point or single value may serve as its own lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • the present application first provides a lithium metal negative electrode.
  • the lithium metal negative electrode includes a negative electrode current collector, a lithium-based metal layer located on at least one surface of the negative electrode current collector, and a polymer modified layer located on the surface of the at least one lithium-based metal layer and capable of conducting ions, the polymer modified layer comprising at least one The catalytic amount of Lewis acid, the Lewis acid contains cations of metals capable of forming an alloy-based active material with lithium.
  • the polymer modified layer is obtained by in-situ polymerization of monomers on the surface of the lithium-based metal layer under the catalysis of Lewis acid, and the polymer modified layer has ionic conductivity, which can ensure good lithium Ion transport properties.
  • the polymer modified layer can improve the lithium deposition behavior on the surface of the lithium-based metal layer, so that the lithium is deposited uniformly.
  • the Lewis acid contains metal cations. The metals in the Lewis acid near the lithium-based metal layer first form an alloy-based active material with lithium, and the metal of the remaining Lewis acid will alloy with the newly deposited lithium during electrochemical charging.
  • Lithium alloys have better lithiophilicity and lithium ion migration properties, and the lithium alloys distributed on the surface of the lithium-based metal layer and in the modified layer can further regulate the uniform deposition of lithium. Therefore, through the dual functions of ion-conducting polymer and lithium alloy, lithium can be uniformly deposited on the surface of lithium metal negative electrode, inhibiting the growth of lithium dendrites, thereby greatly reducing the risk of internal short circuit in lithium metal batteries and improving safety performance.
  • the polymer modified layer may include one or more of polyether, polyester and polyimine.
  • the polyether may include, but is not limited to, one or more of polyethylene oxide, polypropylene oxide, polyethylene glycol, and polyethylene glycol dimethyl ether.
  • Polyimides may include, but are not limited to, polyimides and the like.
  • Polyesters may include, but are not limited to, one or more of polycarbonates, polysulfates and polysulfonates.
  • the polymer in the polymer modification layer may also include other polymers useful in solid electrolyte membranes; for example, polyolefins (eg, polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl chloride, etc.) , polynitriles (such as polyacrylonitrile, etc.), polycarboxylate (such as polymethyl methacrylate, polymethyl acrylate, etc.).
  • polyolefins eg, polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl chloride, etc.
  • polynitriles such as polyacrylonitrile, etc.
  • polycarboxylate such as polymethyl methacrylate, polymethyl acrylate, etc.
  • the polymer modification layer includes one or more of polycarbonate, polysulfate, polysulfite, and polysulfonate.
  • Polycarbonates may include, but are not limited to, polymers of one or more of the cyclic carbonates represented by formula (H1), and one or more of their halogenated derivatives.
  • the polysulfate may include, but is not limited to, one or more polymers of the cyclic sulfates represented by formula (H2), and one or more of their halogenated derivatives.
  • Polysulfites can include, but are not limited to, polymers of one or more of the cyclic sulfites represented by formula (H3), and one or more of their halogenated derivatives.
  • the polysulfonates may include, but are not limited to, polymers of one or more of the cyclic sulfonates represented by formula (H4), and one or more of their halogenated derivatives.
  • a halogenated derivative means that one or more hydrogens in an organic matter are replaced by a halogen.
  • Halogen includes F, Cl, Br, I.
  • R 11 , R 12 , R 13 , R 14 , R 15 , and R 16 when present, each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, or a carbon atom number. is a haloalkyl group of 1 to 4.
  • "Halogen atom” includes F, Cl, Br, I.
  • Alkyl with 1 to 4 carbon atoms includes straight or branched chain saturated hydrocarbon groups containing 1 to 4 carbon atoms, such as methyl, ethyl, propyl (such as n-propyl, isopropyl), butyl Alkyl groups (such as n-butyl, isobutyl, sec-butyl, tert-butyl) and the like are analogous to alkyl groups.
  • Hydrocarbon groups containing 1 to 4 carbon atoms such as methyl, ethyl, propyl (such as n-propyl, isopropyl), butyl Alkyl groups (such as n-butyl, isobutyl, sec-butyl, tert-butyl) and the like are analogous to alkyl groups.
  • Hydroalkyl having 1 to 4 carbon atoms means that one or more hydrogens in the alkyl group having 1 to 4 carbon atoms are substituted by halogen atoms, for example, by
  • Examples of the haloalkyl group having 1 to 4 carbon atoms may include -CH 2 F, -CHF 2 , -CF 3 , -CH 2 CF 3 , -C 2 F 5 , -(CH 2 ) 2 CF 3 , -C 3 F 7 , -(CH 2 ) 3 CF 3 , -C 4 F 9 , but not limited thereto.
  • t represents 1, 2, 3 or 4 when present, eg 1 or 2.
  • the polymer of the modification layer includes one or more of F, Cl, Br, and I.
  • F is contained in the monomeric units of the polymer.
  • halogens such as F
  • substances such as LiF can be formed with lithium, which can improve the surface stability of the lithium metal anode, thereby improving the interface stability between the lithium metal anode and the electrolyte, and further improving the cycle performance of the battery.
  • the battery can also obtain better first-week discharge specific capacity and first-week charge-discharge efficiency.
  • the polymer-modified layer is obtained by in-situ polymerization of Lewis acid-catalyzed monomers on the surface of the lithium-based metal layer.
  • the monomers may be the monomers corresponding to the aforementioned polymers.
  • the monomer may be selected from cyclic carbonates (eg, ethylene carbonate, propylene carbonate, etc.), cyclic sulfates (eg, ethylene sulfate, propylene sulfate, etc.), cyclic ethylene carbonate, etc.
  • the monomers may include one or more of cyclic carbonates and halogenated derivatives thereof.
  • the monomer may include one or more of ethylene carbonate (EC), propylene carbonate (PC) and their halogenated derivatives.
  • the aforementioned halogenated derivatives are, for example, fluoro derivatives.
  • the monomers may include one or more of ethylene carbonate and fluoroethylene carbonate (FEC), including, for example, fluoroethylene carbonate.
  • the Lewis acid is selected from one or more of the compounds represented by formula (1): An L m ( 1).
  • A represents a cation of Al, Zn, Mg, Pb, Ge, Sn or Sb.
  • A represents a cation of Al or Zn.
  • the lithium alloy formed by suitable A and lithium can have better lithiophilicity and lithium ion migration performance, which can further improve the safety performance and cycle performance of the battery.
  • L independently represents F-, Cl-, Br-, I- or an anion represented by formula (2).
  • X and Y each independently represent F, Cl, Br, I, an alkyl group having 1 to 4 carbon atoms, or a haloalkyl group having 1 to 4 carbon atoms.
  • the alkyl group having 1 to 4 carbon atoms is selected from methyl, ethyl, propyl (such as n-propyl, isopropyl), butyl (such as n-butyl, isobutyl, sec-butyl, tert-butyl) and similar alkyl groups.
  • the halogenated alkyl group having 1 to 4 carbon atoms may be one or more hydrogens in the above-mentioned alkyl group having 1 to 4 carbon atoms are substituted by halogen atoms, for example, by F.
  • X and Y each independently represent F or an F-substituted alkyl group having 1 to 4 carbon atoms.
  • the F-substituted alkyl group having 1 to 4 carbon atoms include -CH 2 F, -CHF 2 , -CF 3 , -CH 2 CF 3 , -C 2 F 5 , -(CH 2 ) 2 CF 3 , -C 3 F 7 , -(CH 2 ) 3 CF 3 , -C 4 F 9 , but not limited thereto.
  • z is 0, 1, 2, 3 or 4.
  • z is 0 or 1.
  • L may represent F ⁇ , Cl ⁇ , Br ⁇ , I ⁇ , [(FSO 2 ) 2 N] ⁇ , [(CF 3 SO 2 ) 2 N] ⁇ , [(FSO 2 )(CF 3 SO 2 )N] ⁇ , [(FSO 2 )(C 2 F 5 SO 2 )N] ⁇ , or [(FSO 2 )(C 4 F 9 SO 2 )N] ⁇ .
  • L can represent F - , Cl - , [(FSO 2 ) 2 N] - , [(CF 3 SO 2 ) 2 N] - , [(FSO 2 )(CF 3 SO 2 )N] - , [(FSO 2 )(C 2 F 5 SO 2 )N] ⁇ , or [(FSO 2 )(C 4 F 9 SO 2 )N] ⁇ .
  • halogens such as F in L can form substances such as LiF with lithium, which can improve the interfacial stability between the lithium metal negative electrode and the electrolyte, thereby further improving the cycle performance of the battery.
  • the Lewis acid may be selected from AlF3 , ZnF2 , AlCl3, ZnCl2, Al[( FSO2 ) 2N] 3 , Zn[( FSO2 ) 2N] 2 , Al [ ( CF3 SO 2 ) 2 N] 3 , Zn[(CF 3 SO 2 ) 2 N] 2 , Al[(FSO 2 )(CF 3 SO 2 )N] 3 , Zn[(FSO 2 )(CF 3 SO 2 )N ] 2 , Al[(FSO 2 )(C 2 F 5 SO 2 )N] 3 , Zn[(FSO 2 )(C 2 F 5 SO 2 )N] 2 , Al[(FSO 2 )(C 4 F 9 One or more of SO 2 )N] 3 and Zn[(FSO 2 )(C 4 F 9 SO 2 )N] 2 .
  • the Lewis acid may be selected from AlF 3 , ZnF 2 , AlCl 3 , ZnCl 2 , Al[(FSO 2 ) 2 N] 3 , Zn[(FSO 2 ) 2 N] 2 , Al[(CF 3 SO 2 ) 2 N] 3 , Zn[(CF 3 SO 2 ) 2 N] 2 , Al[(FSO 2 )(CF 3 SO 2 )N] 3 , Zn[(FSO 2 )(CF 3 SO 2 )N] 2 one or more of them.
  • the Lewis acid can be selected from one or more of AlF 3 , ZnF 2 , AlCl 3 , ZnCl 2 , Al[(FSO 2 ) 2 N] 3 and Zn[(FSO 2 ) 2 N] 2 .
  • the Lewis acid can be selected from one of AlCl 3 , ZnCl 2 , Al[(FSO 2 ) 2 N] 3 (abbreviated as Al(FSI) 3 ) and Zn[(FSO 2 ) 2 N] 2 species or several.
  • the weight part of the Lewis acid may be 1-35, for example, 3-30, 5-25, 5-20, 8- 16, or 10 to 20.
  • Appropriate ratio of Lewis acid to monomer can initiate the polymerization and gelation of the monomer, so that the modified layer can obtain good strength and flexibility, so that it can effectively play the role of suppressing short circuit and improve the safety performance of the battery.
  • the reaction of the monomer is mild during polymerization, which greatly reduces the decomposition of the polymer caused by the strong reaction, and the surface passivation of the lithium metal negative electrode, so that the battery can maintain a high charge-discharge stability in the middle and late cycle, and improve the cycle life. , and can also make the battery obtain higher first-week discharge specific capacity and first-week coulombic efficiency.
  • the polymer modification layer further includes a lithium salt.
  • the modified layer can obtain or enhance the ionic conductivity and reduce the polarization of the battery, thereby helping the battery to obtain higher cycle performance.
  • the lithium salt may include one or more of organic lithium salts and inorganic lithium salts. It can be selected from electrolyte lithium salts known in the art.
  • lithium salts may include LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiBOB (lithium dioxalate borate), LiDFOB One or more of (lithium difluorooxalate borate), LiTFOP (lithium tetrafluorooxalate phosphate), LiN(SO 2 R F ) 2 and LiN(SO 2 F)(SO 2 R F ).
  • R F represents C n F 2n+1 , and n is an integer of 0-10, for example, an integer of 0-6.
  • n is 0, 1 or 2.
  • R F represents F, CF 3 , C 2 F 5 , C 3 F 7 , or C 4 F 9 .
  • examples of LiN(SO 2 R F ) 2 may include LiN(SO 2 F ) 2 (lithium bisfluorosulfonimide, abbreviated as LiFSI), LiN(SO 2 CF 3 ) 2 (bistrifluoromethane) Lithium sulfonimide, abbreviated as LiTFSI) and so on.
  • LiN(SO 2 F)(SO 2 R F ) may include LiFSI, LiN(SO 2 F)(SO 2 CF 3 ), and the like.
  • the lithium salt may be selected from one or more of LiFSI, LiDFOB, LiN(SO 2 F)(SO 2 CF 3 ).
  • the modified layer can obtain a good film-forming effect, thereby improving the cycle performance of the battery.
  • the weight proportion of lithium salt in the polymer modification layer is ⁇ 60%, for example, 5%-60%, 10%-40%, 5%-20%, 10%-20%, 5% ⁇ 15%, or 15% ⁇ 25%.
  • Appropriate content of lithium salt in the modified layer can make the modified layer obtain good film quality and high ionic conductivity, thereby improving the safety performance and cycle performance of the battery.
  • the weight ratio of the lithium salt in the modification layer can be tested by methods known in the art, such as ion chromatography.
  • the test can refer to JY/T 020-1996 "General Principles of Ion Chromatography Analysis Methods".
  • the polymer modified layer also optionally includes inorganic fillers.
  • D may include one or more of B, Si, P, Ti, Al, Mg, Zr, Zn, Fe, Ba, Pd, and Li.
  • E may represent O, N, S or PO 4 .
  • the inorganic filler may include silicon dioxide (SiO 2 ), titanium oxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO), zirconium oxide (ZrO 2 ), zinc oxide (ZnO), oxide One of iron (Fe 3 O 4 ), barium titanate (BaTiO 3 ), lead titanate (PbTiO 3 ), lithium nitride (Li 3 N), lithium aluminate (LiAlO 2 ), montmorillonite and molecular sieve or several.
  • the inclusion of inorganic fillers in the polymer modification layer is beneficial to increase the ion transport channel in the film layer, thereby improving lithium deposition, and increasing the ionic conductivity of the modification layer, thereby further improving the cycle performance of the battery.
  • the volume average particle size D v 50 of the inorganic filler is 50 nm to 1000 nm, for example, 50 nm to 100 nm, 50 nm to 300 nm, 50 nm to 350 nm, 100 nm to 800 nm, 100 nm to 500 nm, 150 nm to 350 nm, or 500 nm to 500 nm to 1000nm.
  • the particle size of the inorganic filler is in an appropriate range, the ionic conductivity of the modified layer can be further improved, the mechanical strength of the modified layer can also be improved, and the battery cycle life can be improved.
  • the volume average particle diameter D v 50 of the inorganic filler is the meaning known in the art, and can be tested by methods known in the art.
  • laser particle size analyzer eg Malvern Master Size 3000
  • the test can refer to GB/T 19077.1-2016.
  • D V 50 represents the particle size corresponding to the cumulative volume distribution percentage of the inorganic filler reaching 50%.
  • the weight proportion of the inorganic filler in the modification layer is less than or equal to 10%.
  • the weight proportion of the inorganic filler in the modification layer is 1%-10%, 1%-5%, 2%-6%, 3%-8%, or 3%-5%.
  • the appropriate content of inorganic fillers in the modified layer can not only play the role of inorganic fillers in improving the ion transport of the modified layer, but also help the modified layer to have appropriate mechanical strength and flexibility, which can improve the lithium metal negative electrode and separator or solid electrolyte.
  • the interfacial contact between membranes reduces the interfacial impedance, thereby further improving the deposition/dissolution behavior of lithium, enabling the battery to obtain better safety performance and cycle performance.
  • the weight proportion of the inorganic filler in the modification layer can be tested by methods known in the art.
  • the modified layer can be washed three times in turn with dimethyl carbonate and water; after drying the obtained solid material at 120°C, weigh it to obtain the weight of the inorganic filler in the modified layer; calculate the inorganic filler in the modified layer weight ratio.
  • the thickness of the polymer modification layer may be 100 nm ⁇ 10 ⁇ m.
  • the thickness of the polymer modification layer is 200 nm to 7 ⁇ m, 300 nm to 5 ⁇ m, 500 nm to 3 ⁇ m, 1 ⁇ m to 5 ⁇ m, 1 ⁇ m to 3 ⁇ m, 2 ⁇ m to 5 ⁇ m, or 2 ⁇ m to 4 ⁇ m.
  • the polymer modification layer has an appropriate thickness, which can fully play the role of improving lithium deposition and effectively improve the safety performance of the battery; at the same time, it can also make the battery have a lower impedance and improve the cycle performance of the battery. In addition, the battery is also beneficial to obtain higher energy density.
  • the thickness of the polymer modification layer can be tested using methods known in the art.
  • An exemplary test method is as follows: the lithium metal negative electrode is quenched in liquid nitrogen, and the cross-sectional morphology and thickness of the lithium metal negative electrode are tested by an environmental scanning electron microscope (SEM, such as Quanta200FEI, FEI, Netherlands). As a specific example, the SEM magnification is 1000 times, the thickness values of 5 different regions are taken, and the average value is calculated as the thickness of the polymer modification layer.
  • the compressive elastic modulus of the polymer modification layer is 0.01MPa-1MPa, further optionally 0.02MPa-0.78MPa, 0.1MPa-0.8MPa, 0.3MPa-0.8MPa, 0.4MPa-0.78MPa, Or 0.5MPa ⁇ 0.75MPa.
  • the polymer modification layer is flexible, which can further improve the interface contact between the lithium metal anode and the separator or solid electrolyte membrane (such as inorganic solid electrolyte membrane), reduce the interface impedance, and thus further improve the deposition/dissolution behavior of lithium, which can further improve the The safety performance and cycle performance of the battery.
  • the mixed solution for preparing the polymer modification layer can be coated on the stainless steel substrate to undergo catalytic polymerization to obtain a gelled product; the gelled product is cut into 10 mm in diameter and 1 mm in thickness ⁇ 5mm (for example, 1mm) cylindrical sample; put the sample on the electronic universal chemical testing machine MTS Exceed E43 for compression test, the compression rate is 10% thickness/min, take 5 parallel samples of each sample for the experiment, take the average value.
  • the compressive elastic modulus E of the gel is calculated by linear fitting of the data whose compression ratio is within 5%. The calculation formula is as follows:
  • E ⁇ l/(S ⁇ l), where: E represents the compressive elastic modulus (unit, Pa); ⁇ represents the pressure (unit, N); l represents the thickness of the sample before compression deformation (unit, m) ; S represents the area of the sample before compression deformation (unit, m 2 ); ⁇ l represents the thickness of the sample compressive deformation (unit, m).
  • the lithium-based metal layer may include one or more of metallic lithium and lithium alloys.
  • the content of lithium element in the lithium alloy can be selected as more than 30wt%, more than 50wt%, more than 70wt%, more than 90wt%, more than 95wt%, more than 97wt%, or more than 99wt%.
  • Lithium alloys may include, but are not limited to, one or more of lithium-indium alloys, lithium-zinc alloys, lithium-magnesium alloys, lithium-tin alloys, and lithium-silver alloys.
  • the lithium-based metal layer may have a thickness of 1 ⁇ m ⁇ 200 ⁇ m, eg, 3 ⁇ m ⁇ 120 ⁇ m, 5 ⁇ m ⁇ 100 ⁇ m, 10 ⁇ m ⁇ 60 ⁇ m, 15 ⁇ m ⁇ 50 ⁇ m, or 20 ⁇ m ⁇ 30 ⁇ m.
  • the negative electrode current collector can be a metal foil or a composite current collector (a metal material can be arranged on a polymer substrate to form a composite current collector).
  • the negative electrode current collector may use copper foil, carbon-coated copper foil, or stainless steel sheet.
  • the present application also provides a preparation method of a lithium metal negative electrode, according to which any one of the above-mentioned lithium metal negative electrodes can be prepared.
  • the preparation method of lithium metal negative electrode comprises the following steps:
  • a lithium metal negative electrode to be modified includes a negative electrode current collector and a lithium-based metal layer disposed on at least one surface of the negative electrode current collector.
  • a mixed solution is provided that contains the monomer and the Lewis acid.
  • the mixed solution is made to cover the surface of at least one lithium-based metal layer, and the Lewis acid catalyzes the polymerization of the monomer to form an ion-conducting polymer modified layer to obtain a lithium metal negative electrode.
  • the lithium metal negative electrode to be modified can be obtained commercially or prepared by methods known in the art.
  • a lithium-based metal foil can be laminated and compounded on any surface or two opposite surfaces of the negative electrode current collector to obtain a lithium metal negative electrode to be modified.
  • the lithium-based metal foil may be a metallic lithium foil or a lithium alloy foil.
  • the Lewis acid and the monomer may be selected from one or more of those described herein, respectively.
  • the ratio of Lewis acid and monomer can be as described above.
  • a reaction moderator is also included in the mixed solution.
  • the reaction moderator can control the reaction rate and prevent the reaction from being too violent and exothermic, so that the reaction can be carried out under mild conditions to prevent the decomposition of the polymer.
  • the polymer modified layer is a colloidal elastic film layer with good quality, which can effectively improve the safety performance and cycle performance of the battery.
  • the reaction moderator may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl formate, ethyl formate , ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, methyl One or more of thioether, diethyl sulfite, dimethyl sulfite, tetrahydrofuran, and cyclic ester represented by formula (I).
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • EMC ethyl methyl carbonate
  • methyl formate ethyl formate
  • ethyl propionate eth
  • Q represents O or S.
  • the cyclic ester represented by formula (I) may include one or more of (I-1) and (I-2).
  • R 1 and R 2 independently represent H, F, or a fluoroalkyl group having 1 to 4 carbon atoms.
  • the "fluoroalkyl group having 1 to 4 carbon atoms” means that one or more hydrogens in the alkyl group having 1 to 4 carbon atoms are substituted by F.
  • the alkyl group having 1 to 4 carbon atoms can be as described herein.
  • R 1 and R 2 independently represent H, F, -CH 2 F, -CHF 2 , -CF 3 , -CH 2 CF 3 , -C 2 F 5 , -(CH 2 ) 2 CF 3 , - C 3 F 7 , -(CH 2 ) 3 CF 3 , -C 4 F 9 , but not limited thereto.
  • R 3 represents a fluoroalkylene group having 1 to 3 carbon atoms.
  • the "fluoroalkylene group having 1 to 3 carbon atoms” means that one or more hydrogens in the alkyl group having 1 to 3 carbon atoms are substituted by F.
  • Alkyl groups with 1-3 carbon atoms include straight-chain or branched-chain saturated hydrocarbon groups containing 1-3 carbon atoms, such as methyl, ethyl, propyl (such as n-propyl, isopropyl) and similar alkyl groups .
  • R 3 may represent -CH 2 F, -CHF 2 , -CF 3 , -CH 2 CF 3 , -C 2 F 5 , -(CH 2 ) 2 CF 3 , -C 3 F 7 , but does not limited to this.
  • the reaction moderator may include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), and ethyl methyl carbonate (EMC).
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • EMC ethyl methyl carbonate
  • reaction corrosion inhibitors include ethyl methyl carbonate.
  • the part by weight of the reaction moderator may be greater than 0 and less than or equal to 800.
  • the weight part of the reaction moderator is 50-750, 60-500, 60-200, 70-350, 70-300, 80-250, 100-200, or 120-185, etc. .
  • Appropriate content of the reaction moderator is beneficial to control the reaction rate, reduce the interface side reaction during the polymerization reaction, improve the interface stability, and at the same time make the polymer modified layer obtain suitable strength and flexibility, thereby improving the safety performance of the battery.
  • the cycle performance can also improve the first cycle discharge specific capacity and the first cycle Coulomb efficiency.
  • the mixed solution also optionally includes a lithium salt.
  • the lithium salt can be selected from one or more of the lithium salts described herein.
  • the content of the lithium salt is less than 200 parts by weight, eg, 10-200, 20-150, 25-100, 30-80, or 40-60 parts by weight, based on 100 parts by weight of the monomer.
  • the mixed solution also optionally includes inorganic fillers.
  • the inorganic filler can be selected from one or more of the inorganic fillers described herein.
  • the content of the inorganic filler in the mixed solution, is 30 parts by weight or less based on 100 parts by weight of the monomer, for example, 20 parts by weight or less, or 10 parts by weight or less.
  • the content of the inorganic filler in the mixed solution is 1-30, 3-20, 5-15, 5-10, 8-15, 10-20, or 10-15 parts by weight .
  • the lithium metal negative electrode to be modified can be dipped in the mixed solution, or the mixed solution can be coated on the surface of the lithium-based metal layer of the lithium metal negative electrode to be modified, so that the mixed solution covers the surface of the lithium-based metal layer .
  • the mixed solution can be coated on the surface of the lithium-based metal layer by means of blade coating, spin coating, spray coating, or the like.
  • the mixed solution After the mixed solution is covered on the surface of the lithium-based metal layer, it can be allowed to stand for 5 minutes to 50 hours to complete the polymerization reaction and obtain a polymer modified layer.
  • the standing time is 10min ⁇ 10h, 15min ⁇ 120min, 20min ⁇ 100min, 20min ⁇ 60min, 30min ⁇ 150min, 30min ⁇ 90min, or 40min ⁇ 60min.
  • the present application also provides a lithium metal battery.
  • the lithium metal battery according to the present application includes a positive electrode and a negative electrode, and the negative electrode is any lithium metal negative electrode of the present application.
  • lithium metal battery of the present application adopts the lithium metal negative electrode of the present application, the safety performance can be improved under the condition of high energy density.
  • lithium metal batteries can also have high cycle performance, first-cycle discharge specific capacity and first-time charge-discharge efficiency.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
  • the positive electrode current collector has two surfaces opposite in its thickness direction, and the positive electrode film layer is provided on either 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 (a metal material can be arranged on a polymer substrate to form a composite current collector).
  • the positive electrode current collector may be selected from aluminum foil, carbon-coated aluminum foil, or stainless steel sheet.
  • the positive electrode active material may include one or more of layered lithium transition metal oxides, spinel structure lithium transition metal oxides, olivine structure lithium-containing phosphates, and their respective modified materials.
  • layered lithium transition metal oxides may include, but are not limited to, lithium cobaltate (eg, LiCoO 2 ), lithium nickelate (eg, LiNiO 2 ), ternary materials (eg, LiNi s B t C (1-st) O 2 ( Wherein, B and C are independently selected from Co, Al, Mn, and B and C are different, 0 ⁇ s ⁇ 1, 0 ⁇ t ⁇ 1)) and one or more of its modified materials.
  • the spinel structure lithium transition metal oxide may include, but is not limited to, one or more of lithium manganate (LiMn 2 O 4 ), lithium nickel manganate (LiNi 0.5 Mn 1.5 O 4 ) and modified materials thereof.
  • Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (LiFePO 4 ), lithium cobalt phosphate (LiCoPO 4 ), lithium manganese phosphate (LiMnPO 4 ), lithium nickel phosphate (LiNiPO 4 ), iron phosphate ( One or more of FePO 4 ) and their respective modified materials.
  • the positive electrode active material may include one or more of the lithium transition metal oxides represented by formula (3) and modified compounds thereof,
  • M is selected from Mn, Al, Zr , one or more of Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from one or more of N, F, S and Cl.
  • the working voltage window of the battery can be improved, so that the battery can obtain a higher energy density and also have a higher cycle performance.
  • M is selected from one or more of Mn and Al.
  • A is F.
  • the modified material of each of the above materials may be doping modification or surface coating modification of the positive electrode active material.
  • Doping and cladding elements can be independently selected from metallic and non-metallic elements such as Li, N, F, Cl, S, B, P, Al, Si, Zr, Ti, Ge, Sn, Mg, Zn, One or more of Ce, W, V, etc.
  • the positive electrode film layer usually includes a positive electrode active material and an optional positive electrode solid electrolyte, an optional binder and an optional conductive agent, usually coated with a positive electrode slurry, and dried, compacted.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material and optional positive electrode solid electrolyte, optional conductive agent and binder in a solvent and stirring uniformly.
  • the mixing method of the positive electrode slurry can be a well-known mixing method in the industry, such as magnetic stirring, mechanical ball milling, and the like.
  • the positive film layer comprises a positive solid electrolyte.
  • the positive electrode film layer can be combined with a solid electrolyte film and a lithium metal negative electrode to form a solid lithium metal battery.
  • Solid-state lithium metal batteries have no risk of electrolyte leakage due to the use of solid-state electrolyte membranes, and at the same time can inhibit the puncture of lithium dendrites, so the safety performance can be improved.
  • the positive solid electrolyte can use materials known in the art, and can be selected according to actual needs.
  • the positive solid electrolyte can be one or more of sulfide solid electrolyte, oxide solid electrolyte, and polymer solid electrolyte.
  • the oxide electrolyte may include a compound having a NASICON (Na + super ionic conductor, Na fast ionic conductor) structure (eg, NaE 2 (PO 4 ) 3 , where E represents Ti, Zr, or Ge), with LISICON (Li + super ionic conductor, Li fast ion conductor) structure compound (such as Li 14 Zn(GeO 4 ) 4 ), compound with garnet structure (such as Li 7 La 3 L 2 O 12 , where L represents One or more of Zr or Sn) and compounds with perovskite structure (such as Li 3x La 1-3x TiO 3 , where 0 ⁇ x ⁇ 0.16).
  • NASICON Na + super ionic conductor, Na fast ionic conductor
  • Li fast ion conductor Li 14 Zn(GeO 4 ) 4
  • garnet structure such as Li 7 La 3 L 2 O 12 , where L represents One or more of Zr or Sn
  • perovskite structure such as Li 3
  • the sulfide electrolyte may include Li 10 MP 2 S 12 , Li 6 (P 1-a Ma )S 5 X, Li 3 PS 4 , Li 7 P 3 S 11 , where M is Ge, Si , one or more of Sn, Sb; X is one or more of F, Cl, Br, I; 0.01 ⁇ a ⁇ 1.
  • the oxide electrolyte may be selected from one or more of Li 3 PS 4 , Li 10 GeP 2 S 12 , and Li 6 PS 5 Cl .
  • the polymer solid electrolyte may include one or more of polyether (PEO), polyacrylonitrile (PAN), polyacrylate (PMMA), and polyvinylidene fluoride (PVDF). kind.
  • PEO polyether
  • PAN polyacrylonitrile
  • PMMA polyacrylate
  • PVDF polyvinylidene fluoride
  • the binder may include styrene-butadiene-styrene triblock thermoplastic elastomer (SBS), ethylene-butylene copolymer (SEBS), polyvinylidene fluoride (PVDF), polyvinylidene fluoride (PVDF), polyvinylidene One or more of tetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), styrene-butadiene rubber, nitrile rubber, butene rubber, styrene rubber or polyurethane.
  • SBS styrene-butadiene-styrene triblock thermoplastic elastomer
  • SEBS ethylene-butylene copolymer
  • PVDF polyvinylidene fluoride
  • PVDF polyvinylidene fluoride
  • PVDF polyvinylidene
  • PTFE tetrafluoroethylene
  • PAALi lithium polyacrylate
  • the conductive agent may include one or more of conductive carbon black (super-P), acetylene black, vapor-grown carbon fiber (VGCF for short), carbon nanotube, and graphene .
  • the solvent can be selected from organic solvents, such as one or more of ether solvents, hydrocarbon solvents, ester solvents, nitrile solvents, amide solvents, alcohol solvents, and halogenated hydrocarbon solvents .
  • the ether solvent can be selected from one or more of diethyl ether, tetrahydrofuran (THF), and ethylene glycol dimethyl ether.
  • the hydrocarbon solvent can be selected from one or more of n-pentane, n-hexane, cyclohexane, toluene, xylene and trimethylbenzene.
  • the ester solvent can be selected from one or more of ethyl acetate, methyl formate and dimethyl phthalate.
  • Nitrile-based solvents may include acetonitrile.
  • the amide solvent can be selected from one or more of N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF).
  • the alcoholic solvent may include ethanol.
  • the halogenated hydrocarbon solvent can be selected from one or more of dichloromethane and 1,2-dichloroethane.
  • the solvent of the positive electrode slurry may be N-methylpyrrolidone (NMP) and/or tetrahydrofuran (THF).
  • the positive electrode slurry comprises a positive electrode solid electrolyte, and drying and compacting are optionally performed under the protection of protective gas.
  • the shielding gas can be nitrogen or an inert gas such as argon.
  • the compaction pressure may be 20 MPa to 500 MPa, such as 200 MPa to 300 MPa.
  • the temperature of compaction may be 20°C to 160°C, eg, 20°C to 100°C.
  • the compaction density of the positive electrode active material layer may be 1.8 g/cm 3 to 4.2 g/cm 3 , for example, 2.8 g/cm 3 to 4.0 g/cm 3 .
  • the positive electrode active material layer includes a positive electrode active material, a positive electrode solid electrolyte, a conductive agent, and a binder.
  • Reasonable regulation of the content of each component in the cathode active material layer can build a good conduction network of electrons and lithium ions, and improve the cycle performance of the battery.
  • the mass ratio of the positive electrode active material in the positive electrode active material layer is 48% to 90%, for example, 60% to 75%, 70% to 85%, or 65% to 80%.
  • the positive active material has an appropriate proportion in the positive active material layer, which is not only conducive to the transfer of electrons and lithium ions, but also to the battery to obtain a higher energy density.
  • the mass ratio of the positive electrode solid electrolyte in the positive electrode active material layer is 8% to 50%, for example, 10% to 40%, 15% to 30%, or 10% to 25%.
  • the mass proportion of the conductive agent in the positive electrode active material layer may be 1% to 10%, for example, 2% to 8%, 3% to 6%, 4% to 7%, or 2% to 5%.
  • the mass proportion of the binder in the positive electrode active material layer may be 1%-10%, for example, 2%-8%, 3%-6%, 4%-7%, or 2%-5%.
  • the thickness of the positive electrode active material layer may be 10 ⁇ m ⁇ 200 ⁇ m.
  • the thickness of the positive electrode active material layer is 40 ⁇ m to 160 ⁇ m, 60 ⁇ m to 120 ⁇ m, or 80 ⁇ m to 140 ⁇ m, or the like.
  • the thickness of the positive electrode active material layer is in an appropriate range, which is conducive to improving the capacity of the positive electrode, so that the battery can obtain a higher energy density; at the same time, it can also make the positive electrode active material layer have a lower lithium ion transmission impedance, reduce polarization, Thus, the battery has both high cycle performance.
  • an electrolyte known in the art can be used as the electrolyte, and those skilled in the art can select it according to requirements.
  • the electrolyte may be selected from solid electrolyte membranes, or liquid electrolytes (ie, electrolytes).
  • the electrolyte employs a solid electrolyte membrane.
  • the solid electrolyte membrane is arranged between the negative pole piece and the positive pole piece to conduct ions.
  • the solid electrolyte membrane can be selected from one or more of inorganic solid electrolyte membranes, solid polymer electrolyte membranes and inorganic-organic composite solid electrolyte membranes. Compared with the electrolyte, the solid electrolyte membrane has no risk of liquid leakage, which further improves the safety performance of the battery.
  • the lithium metal battery is an all-solid-state battery or a semi-solid-state battery.
  • the solid electrolyte membrane is selected from inorganic solid electrolyte membranes.
  • the use of an inorganic solid electrolyte membrane is beneficial to increase the voltage window of the battery, thereby increasing the energy density.
  • the surface of the lithium metal anode has a polymer modification layer, which has appropriate flexibility, which can significantly improve the contact between the lithium metal anode and the inorganic solid electrolyte membrane, reduce the interfacial impedance, and the polymer modification layer can also improve the deposition and dissolution of lithium, Therefore, the growth of lithium dendrites can be greatly reduced, the risk of short circuit in the battery can be reduced, and the safety performance can be improved. Further, the cycle performance of the battery can also be improved.
  • the inorganic solid electrolyte membrane includes an inorganic solid electrolyte and an optional binder.
  • the inorganic solid electrolyte may include one or more of oxide electrolytes and sulfide electrolytes.
  • the oxide electrolyte may include one or more of a compound having a NASICON structure, a compound having a LISICON structure, a compound having a garnet structure, and a compound having a perovskite structure.
  • the oxide electrolyte may be selected from NaE 2 (PO 4 ) 3 , where E represents Ti, Zr or Ge; Li 14 Zn(GeO 4 ) 4 ; Li 7 La 3 L 2 O 12 , where L represents Zr or Sn ; Li 3x La 1-3x TiO 3 , where 0 ⁇ x ⁇ 0.16.
  • the sulfide electrolyte may include Li 10 MP 2 S 12 , Li 6 (P 1-a Ma )S 5 X, Li 3 PS 4 , Li 7 P 3 S 11 , wherein M is selected from Ge, One or more of Si, Sn, and Sb; X is selected from one or more of F, Cl, Br, and I; 0.01 ⁇ a ⁇ 1.
  • the oxide electrolyte may be selected from one or more of Li 3 PS 4 , Li 10 GeP 2 S 12 , and Li 6 PS 5 Cl .
  • the binder may be selected from styrene-butadiene-styrene triblock thermoplastic elastomer (SBS), ethylene-butene copolymer (SEBS), polyvinylidene fluoride (PVDF) , polytetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), styrene-butadiene rubber, nitrile rubber, butylene rubber, styrene rubber or polyurethane one or more.
  • SBS styrene-butadiene-styrene triblock thermoplastic elastomer
  • SEBS ethylene-butene copolymer
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAALi lithium polyacrylate
  • PVDF-HFP vinylidene fluoride-hexa
  • the mass ratio of the inorganic solid electrolyte and the binder may be 99-50:1-50, for example, 98-80:2-20.
  • the mass ratio of the inorganic solid electrolyte and the binder is in an appropriate range, the inorganic solid electrolyte membrane can obtain higher strength and toughness, as well as higher lithium ion transport performance, thus improving the cycle performance of the battery.
  • Inorganic solid-state electrolyte membranes are commercially available or can be prepared using methods known in the art, for example, by forming a membrane from an electrolyte slurry comprising an inorganic solid-state electrolyte and an optional binder.
  • An exemplary preparation method is as follows: dispersing an inorganic solid electrolyte and a binder in an organic solvent to form an electrolyte slurry; uniformly coating the electrolyte slurry on a substrate (such as a plastic substrate, a glass substrate, etc.), and after drying, The inorganic solid electrolyte membrane is obtained by pressing and molding.
  • the organic solvent should not react with the solid electrolyte, for example, it can be selected from ether solvents, hydrocarbon solvents, ester solvents, nitrile solvents, amide solvents, alcohol solvents, halogenated hydrocarbon solvents. one or more. For example, they may each include those described herein.
  • the organic solvent includes N-methylpyrrolidone (NMP) and/or tetrahydrofuran (THF).
  • the amount of the organic solvent can be adjusted according to the viscosity of the electrolyte slurry.
  • the viscosity of the electrolyte slurry is 5000 mPa ⁇ s ⁇ 200000 mPa ⁇ s, for example, 5000 mPa ⁇ s ⁇ 100000 mPa ⁇ s, or 10000 mPa ⁇ s ⁇ 50000 mPa ⁇ s.
  • the viscosity of the electrolyte slurry is in an appropriate range, which can facilitate the film coating, and can reduce the holes in the inorganic solid electrolyte membrane, reduce the risk of short circuit in the battery to a certain extent, and improve the safety performance.
  • the drying step may include: drying the coating layer naturally for 1-1.5 hours, and then vacuum drying for 1-3 hours.
  • the pressing method can be one-step pressing or step-by-step pressing.
  • the pressing pressure may be 1 MPa to 500 MPa, for example, 100 MPa to 300 MPa.
  • the pressing temperature may be 20°C to 160°C, for example, 20°C to 100°C, 40°C to 100°C, or 60°C to 90°C.
  • the pressing pressure and temperature are within an appropriate range, it is beneficial for the membrane to obtain a higher density, so that the membrane has good strength; and it can also ensure that the solid electrolyte membrane has good ion transport performance.
  • the electrolyte may also employ an electrolytic solution.
  • the electrolyte includes an electrolyte lithium salt and a solvent.
  • the electrolyte lithium salt and the solvent can all be those known in the art, and those skilled in the art can choose according to their needs.
  • the electrolyte salt may be selected from LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (bisfluorosulfonimide) Lithium), LiTFSI (Lithium Bistrifluoromethanesulfonimide), LiTFS (Lithium Trifluoromethanesulfonate), LiDFOB (Lithium Difluorooxalate Borate), LiBOB (Lithium Dioxalate Borate), LiPO 2 F 2 (Difluorooxalate) Lithium phosphate), one or more of LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF6 lithium hexafluorophosphate
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate ester (DPC), methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, One or more of ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC diprop
  • additives are also optionally included in the electrolyte.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, and additives to improve battery low temperature performance. additives, etc.
  • a separator is also included.
  • the separator is arranged between the positive pole piece and the negative pole piece, and plays the role of isolation.
  • the type of the separator in the present application and any known separator can be selected.
  • the separator can be selected from one of glass fiber film, non-woven fabric, polyethylene film, polypropylene film and polyvinylidene fluoride film or a multi-layer composite film comprising two or more of them .
  • the positive electrode sheet, the negative electrode sheet and the separator may be fabricated into an electrode assembly through a winding process or a lamination process.
  • the positive electrode sheet, the inorganic solid electrolyte membrane and the lithium metal negative electrode are sequentially stacked, wherein the inorganic solid electrolyte membrane is interposed between the positive electrode electrode sheet and the lithium metal negative electrode; the stacked units are pressed and compounded together to form a solid lithium metal Electrode assemblies of batteries.
  • the pressure of pressurized compounding can be 1 MPa to 500 MPa, for example, 100 MPa to 300 MPa.
  • the temperature of pressure compounding is 20°C to 160°C, for example, 25°C to 60°C, or 60°C to 120°C.
  • the lithium metal battery can include an outer packaging.
  • the outer packaging can be used to encapsulate the electrode assembly, as well as the electrolyte when needed.
  • the outer packaging of the lithium metal battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like.
  • the outer package of the lithium metal battery can also be a soft package, such as a bag-type soft package.
  • the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • FIG. 2 is a lithium metal battery 5 of 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 plate are enclosed to form a accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening to close the accommodating cavity.
  • the positive electrode sheet, the inorganic solid electrolyte membrane and the lithium metal negative electrode can be laminated to form the electrode assembly 52 .
  • the electrode assembly 52 is packaged in the accommodating cavity.
  • the number of electrode assemblies 52 contained in the lithium metal battery 5 may be one or several, and may be adjusted according to requirements.
  • the lithium metal batteries can be assembled into a battery module, and the number of lithium metal 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 lithium metal batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of lithium metal batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodating space, and the plurality of lithium metal batteries 5 are accommodated in the accommodating space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules included 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 case and a plurality of battery modules 4 disposed in the battery case.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery modules 4 .
  • the plurality of battery modules 4 may be arranged in the battery case in any manner.
  • the present application also provides a device comprising at least one of the lithium metal battery, battery module, or battery pack of the present application.
  • Lithium metal batteries, battery modules or battery packs can be used as a power source for the device or as an energy storage unit for the device.
  • the device may be, but is not limited to, a mobile device (such as a cell phone, a laptop, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • Devices can choose lithium metal batteries, battery modules or battery packs according to their usage requirements.
  • Figure 7 is an apparatus as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • the device can employ battery packs or battery modules.
  • Lewis acid AlCl 3 was added to the monomer solution of LiFSI/FEC/EMC (mass ratio 15:30:55), and the mixture was uniformly mixed to obtain a mixed solution.
  • the addition amount (%) of Lewis acid mass of Lewis acid/mass of monomer solution ⁇ 100%.
  • a 25 ⁇ m lithium metal foil was pasted on the surface of the copper foil by a calendering method, and sliced.
  • the above mixed solution was coated on the surface of the lithium metal layer using a doctor blade, and after standing for 50 min, a polymer modification layer with a thickness of 3 ⁇ m was formed on the surface of the lithium metal layer.
  • the positive active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), the sulfide solid state electrolyte Li 3 PS 4 , the conductive agent VGCF, and the binder styrene-butadiene rubber (number average molecular weight about 500,000) were weighed
  • the ratio of 70:20:5:5 is mixed in THF solvent, and the positive electrode slurry is obtained after fully stirring and evenly mixing; the positive electrode slurry is coated on the surface of the aluminum foil, dried naturally at 60°C, cold-pressed, sliced , get the positive pole piece.
  • the thickness of the positive electrode active material layer was 50 ⁇ m, and the compaction density was 3 g/cm 3 .
  • the sulfide solid electrolyte Li 3 PS 4 and the binder styrene-butadiene rubber were mixed in THF solvent at a weight ratio of 99:1 to prepare an electrolyte slurry; the electrolyte slurry was coated on the surface of the glass substrate, After drying at 60° C. and slicing, a sulfide solid-state electrolyte membrane was obtained.
  • the thickness of the sulfide solid-state electrolyte membrane is 50 ⁇ m.
  • Lithium metal battery Align the above-mentioned lithium metal negative electrode, sulfide solid-state electrolyte membrane, and lithium metal sheet to the center of the stack in sequence, and cold-press at room temperature and 250 MPa for 2 minutes to obtain a stacked unit, which is then placed in an outer package for packaging. After molding, solid-state symmetry is obtained. Lithium metal battery.
  • the preparation method is similar to that of Example 1, except that the relevant parameters in the preparation steps of the lithium metal negative electrode are adjusted to obtain the corresponding lithium metal battery, as shown in Table 1.
  • the cycle test is carried out by means of constant current charge and discharge, wherein the deposition and dissolution capacity is limited to 6mAh/cm 2 , the test current density is about 0.39mA/cm 2 , and the test temperature is 25°C.
  • FIG. 8 shows the cycle curves of the Li/Li symmetric lithium metal batteries of Example 1 and Comparative Example 1.
  • the Li/Li symmetrical battery of Example 1 adopts the lithium metal negative electrode of the present application, wherein the ion-conducting polymer modified layer is formed on the surface of the lithium-based metal layer catalyzed by a Lewis acid, and the Lewis acid contains an ion-conducting polymer modified layer that can form with lithium.
  • the metal cation of the alloy-based active material improves the interfacial stability between the lithium metal anode and the inorganic solid electrolyte membrane, so that the Li/Li symmetric battery exhibits good cycle stability.
  • the overpotential in the first week is higher than that in the second week, which may be due to the lithium alloying process.
  • the Li/Li symmetric battery of Comparative Example 1 uses an unmodified lithium metal negative electrode, and its charge-discharge curve is relatively disordered, the overpotential is high in the early stage, and the side reaction between the surface of the lithium negative electrode and the electrolyte occurs, resulting in a large interface impedance between the two. , a rapid voltage change occurs in the later cycle, and the polarization is severe.
  • the solid-state lithium metal batteries prepared in the examples and comparative examples were tested by constant current charging and discharging, specifically: charging at 0.1C (current density is about 0.13mA/cm 2 ) constant current to The voltage is 4.2V, and then the constant voltage is charged until the current is 0.05C, and the specific capacity of the first cycle is recorded; after standing for 5 minutes, the battery is discharged to a voltage of 2.8V at a constant current of 0.1C, and the specific capacity of the first cycle is recorded.
  • the battery was subjected to a cyclic charge-discharge test according to the above method, and the discharge specific capacity of the 200th cycle was recorded.
  • the first-week coulombic efficiency of solid-state lithium metal batteries first-week discharge specific capacity/first-week charge specific capacity ⁇ 100%.
  • the 200-cycle capacity retention rate of the solid-state lithium metal battery the discharge specific capacity in the 200th cycle/the discharge specific capacity in the first cycle ⁇ 100%.
  • Short circuit rate The battery is subjected to a 200-cycle charge-discharge test according to the method in 1). During the test of 100 solid-state lithium metal batteries, the number of short-circuited solid-state lithium metal batteries is counted, and the number of short-circuited solid-state lithium metal batteries is counted. percentage of battery.
  • the ion-conducting polymer modified layer is formed on the surface of the lithium-based metal layer catalyzed by a Lewis acid, and the Lewis acid contains a metal that can form an alloy-based active material with lithium. It can effectively reduce the risk of internal short circuit in the lithium metal battery using it, and improve the safety performance of the battery. Further, by optimizing the preparation parameters or structural parameters of the polymer modification layer, the battery can obtain higher cycle performance, first-week discharge specific capacity and first-week Coulomb efficiency while improving battery safety performance.
  • Comparative Examples 1 to 3 do not meet the conditions of the present application, the risk of internal short circuit in lithium metal batteries is relatively large, which reduces the safety performance of the battery, and is not conducive to the improvement of battery cycle performance, first-week discharge specific capacity and first-week coulombic efficiency .

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Abstract

本申请实施例提供一种锂金属负极、其制备方法及其相关的锂金属电池和装置。锂金属负极包括：负极集流体；至少一个锂基金属层，设置于负极集流体的至少一个表面上；以及导离子的聚合物修饰层，聚合物修饰层位于至少一个锂基金属层的表面上，并包含至少催化量的路易斯酸，路易斯酸包含能与锂形成合金系活性材料的金属的阳离子。

Description

锂金属负极、其制备方法及其相关的锂金属电池和装置
相关申请的交叉引用
本申请要求享有于2020年11月23日提交的名称为“锂金属负极、其制备方法及其相关的锂金属电池和装置”的中国专利申请202011320607.X的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及二次电池技术领域，具体涉及一种锂金属负极、其制备方法及其相关的锂金属电池和装置。
背景技术
锂离子电池具有高比能量、长寿命、低成本等优势，因而被广泛应用。例如，随着环境及能源问题的日益突出，对新能源电动车的发展有着迫切的需求，使得作为新型能源体系的锂离子电池得到了蓬勃发展。
与此同时，人们对电动车的续航里程提出了更高的要求。这就要求作为能源的锂离子电池具有更高的能量密度。金属锂具有极高的理论比容量(3860mAh/g)、最低的还原电势(-3.04V vs标准氢电极)，因此锂金属负极有望成为下一代高能量密度锂离子电池的优选负极极片。
然而，在实际研究中发现，采用锂金属负极的锂离子电池(也可称锂金属电池)容易引发内短路，存在较大的安全隐患。因此，如何提高锂金属电池的安全性能，成为锂金属电池领域的一个关键挑战。
发明内容
本申请的第一方面提供一种锂金属负极，其包括：负极集流体；至少一个锂基金属层，设置于负极集流体的至少一个表面上；以及导离子的聚合物修饰层，聚合物修饰层位于至少一个锂基金属层的表面上，并包含至少催化量的路易斯酸，路易斯酸包含能与锂形成合金系活性材料的金属的阳离子。
本申请的锂金属负极中，在锂基金属层表面由路易斯酸催化形成导离子聚合物修饰层，并且路易斯酸中含有金属阳离子，该金属能与锂形成合金系活性材料，通过导离子聚合物和合金的双重作用，能有效地调控锂在锂金属负极表面均匀沉积， 抑制锂枝晶的生长，从而大幅度降低锂金属电池发生内短路的风险，提高安全性能。
在本申请任意实施方式中，聚合物修饰层的厚度可以为100nm～10μm，可选的为300nm～5μm，进一步可选的为500nm～3μm。聚合物修饰层具有适当的厚度，可以有效提升电池的安全性能，同时改善电池的循环性能。另外，电池还有利于获得较高的能量密度。
发明人发现，采用合适的路易斯酸和聚合物，可以进一步改善电池的安全性能和循环性能。
在本申请任意实施方式中，路易斯酸可选自式(1)所示的化合物中的一种或几种：A nL m(1)，其中，A表示Al、Zn、Mg、Pb、Ge、Sn或Sb的阳离子，可选的，A表示Al或Zn的阳离子；L独立地表示F－、Cl－、Br－、I－或式(2)所示阴离子，
Figure PCTCN2021128641-appb-000001
其中，X和Y分别独立地表示F、Cl、Br、I、碳原子数为1～4的烷基、或碳原子数为1～4的卤代烷基，可选的，X和Y分别独立地表示F或F取代的碳原子数为1～4的烷基；z为0、1、2、3或4；n和m满足：A的价数×n＝L的价数×m。
在本申请任意实施方式中，L可表示F －、Cl －、Br －、I －、[(FSO 2) 2N] －、[(CF 3SO 2) 2N] －、[(FSO 2)(CF 3SO 2)N] －、[(FSO 2)(C 2F 5SO 2)N] －、或[(FSO 2)(C 4F 9SO 2)N] －。
在本申请任意实施方式中，路易斯酸可选自AlCl 3、ZnCl 2、Al[(FSO 2) 2N] 3和Zn[(FSO 2) 2N] 2中的一种或几种。
在本申请任意实施方式中，聚合物修饰层的压缩弹性模量可以为0.01MPa～1MPa，可选的为0.02MPa～0.78MPa。聚合物修饰层具有柔性，可以进一步改善锂金属负极与隔离膜或固态电解质膜(例如无机固态电解质膜)之间界面接触，因而更加改善锂的沉积/溶出行为，从而能进一步提升电池的安全性能和循环性能。
在本申请任意实施方式中，聚合物可包括聚醚、聚酯和聚亚胺中的一种或几种。可选的，聚合物包括聚碳酸酯、聚硫酸酯、聚亚硫酸酯和聚磺酸酯中的一种或几种。采用合适的聚合物可以使修饰层获得适当的机械强度和柔性，能进一步改善电池的安全性能。
在本申请任意实施方式中，聚合物修饰层通过单体在路易斯酸的催化下，在锂基金属层的表面原位聚合得到。通过表面原位聚合的方式，方便调控修饰层的厚度在所需范围内。
在本申请任意实施方式中，单体可包括环状碳酸酯、环状磺酸酯、环状硫酸酯、环状亚硫酸酯及其卤代衍生物中的一种或多种。可选的，单体包括环状碳酸酯及其卤代衍生物中的一种或多种。
在本申请任意实施方式中，单体可包括碳酸亚乙酯、碳酸亚丙酯及它们的 卤代衍生物中的一种或几种。可选的，单体包括碳酸亚乙酯、氟代碳酸亚乙酯中的一种或几种。进一步可选的，单体包括氟代碳酸亚乙酯。通过引入F等卤素，能提高锂金属负极的表面稳定性，从而进一步提高电池的循环性能。另外，电池还可以获得更好的首周放电比容量和首周充放电效率。
在本申请任意实施方式中，聚合物修饰层还可包括锂盐。在一些实施例中，锂盐在聚合物修饰层中的重量占比≤60％，可选的为10％～40％。通过在聚合物修饰层中添加锂盐，有利于电池获得更高的循环性能。
在本申请任意实施方式中，锂盐可包括LiPF 6、LiBF 4、LiClO 4、LiAsF 6、LiBOB、LiDFOB、LiTFOP、LiN(SO 2R F) 2和LiN(SO 2F)(SO 2R F)中的一种或几种，其中R F表示C nF 2n+1，n为0～10的整数。可选的，锂盐包括LiN(SO 2F) 2、LiDFOB、LiN(SO 2F)(SO 2CF 3)中的一种或几种。合适的锂盐可以使修饰层获得良好的成膜效果，从而进一步改善电池的循环性能。
在本申请任意实施方式中，聚合物修饰层还可包括无机填料。在一些实施例中，无机填料在修饰层中的重量占比≤10％。可选的，无机填料在修饰层中的重量占比为1％～5％。在聚合物修饰层中含有无机填料，可进一步改善电池的循环性能。
在本申请任意实施方式中，无机填料可包括二氧化硅(SiO 2)、氧化钛(TiO 2)、氧化铝(Al 2O 3)、氧化镁(MgO)、氧化锆(ZrO 2)、氧化锌(ZnO)、氧化铁(Fe 3O 4)、钛酸钡(BaTiO 3)、钛酸铅(PbTiO 3)、氮化锂(Li 3N)、铝酸锂(LiAlO 2)、蒙脱土和分子筛中的一种或几种。
在本申请任意实施方式中，无机填料的体积平均粒径D v50为50nm～1000nm，可选的为100nm～800nm。无机填料的粒径在适当范围内，能进一步提高电池循环寿命。
本申请的第二方面提供一种锂金属负极的制备方法，其包括如下步骤：
提供待修饰的锂金属负极，待修饰的锂金属负极包括负极集流体及设置于负极集流体至少一个表面上的锂基金属层；
提供混合溶液，混合溶液包含路易斯酸和单体，路易斯酸包含能与锂形成合金系活性材料的金属的阳离子；
使混合溶液覆盖于至少一个锂基金属层的表面，路易斯酸催化单体发生聚合，形成导离子的聚合物修饰层，得到锂金属负极。
在本申请任意实施方式中，基于100重量份的单体，路易斯酸的重量份可以为1～35，可选的为3～30，进一步可选的为10～20。路易斯酸与单体的配比适当，能使修饰层获得良好的强度和柔性，使其有效发挥抑制短路的作用，提高电池的安全性能。此外，使路易斯酸与单体的配比在适当范围内，还有利于提升电池的循环寿命，还可以使电池获得较高的首周放电比容量和首周库伦效率。
在本申请任意实施方式中，混合溶液还包括反应缓和剂。其中，基于100重量份的单体，反应缓和剂的重量份可以为大于0小于等于800，可选的为100～200。反应缓和剂可以调控反应速率，使反应在温和的条件下进行。所得聚合物修饰层可以为质量良好的胶状弹性膜层，能有效发挥改善电池安全性能和循环性能的作用。
在本申请任意实施方式中，反应缓和剂可包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、甲酸甲酯、甲酸乙酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、乙酸乙酯、N-甲基吡咯烷酮、N-甲基甲酰胺、N-甲基乙酰胺、乙腈、环丁砜、二甲亚砜、甲硫醚、亚硫酸二乙酯、亚硫酸二甲酯、四氢呋喃、如式(I)所示的环状酯中的一种或几种，可选的包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯中的一种或几种；
Figure PCTCN2021128641-appb-000002
其中，Q表示O或S，R 1和R 2独立地表示H、F、或碳原子数为1～4的氟代烷基，R 3表示碳原子数为1～3的氟代亚烷基。
在本申请任意实施方式中，混合溶液还可包括锂盐。锂盐的含量基于100重量份的单体计，可以为200重量份以下。可选的，锂盐的含量基于100重量份的单体计为30～80重量份。
在本申请任意实施方式中，混合溶液还可包括无机填料。无机填料的含量基于100重量份的单体计，可以为30重量份以下。可选的，无机填料的含量基于100重量份的单体计为10～20重量份。
本申请的第三方面提供一种锂金属电池，其包括正极极片和负极极片，其中负极极片为本申请提供的锂金属负极。本申请的锂金属电池由于采用本申请的锂金属负极，因而能获得较高的安全性能。
本申请的第四方面提供一种装置，其包括根据本申请第一方面的锂金属电池。本申请的装置包括所述的锂金属电池，因而至少具有与所述锂金属电池相同的优势。
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例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请实施例提供的一种锂金属负极的扫描电子显微镜(SEM)图。
图2是本申请实施例提供的一种锂金属电池的示意图。
图3是图2的分解图。
图4是本申请实施例提供的一种电池模块的示意图。
图5是本申请实施例提供的一种电池包的示意图。
图6是图5的分解图。
图7是本申请实施例提供的一种装置的示意图。
图8是本申请实施例1和对比例1的Li/Li对称锂金属电池的循环曲线图。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合具体实施例对本申请进行详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种及两种以上。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
本申请首先提供一种锂金属负极。该锂金属负极包括负极集流体、位于负极集流体的至少一个表面上的锂基金属层、以及位于至少一个锂基金属层的表面且能导离子的聚合物修饰层，聚合物修饰层包含至少催化量的路易斯酸，路易斯酸包含能与锂形成合金系活性材料的金属的阳离子。
本申请的锂金属负极中，聚合物修饰层通过单体在路易斯酸的催化下，在锂基金属层的表面原位聚合得到，且聚合物修饰层具有导离子性，可以保证负极良好的锂离子传输性能。特别地，聚合物修饰层能改善锂基金属层表面的锂沉积行为，使锂均匀沉积。并且，路易斯酸中含有金属阳离子。靠近锂基金属层的路易斯酸中的金属首先与锂形成合金系活性材料，其余路易斯酸的金属将在电化学充电期间与新沉积的锂合金化。锂合金具有更好的亲锂性和锂离子迁移性能，分布在锂基金属层表面以及修饰层中的锂合金能进一步调控锂的均匀沉积。因此，通过导离子聚合物和锂合金的双重作用，能使锂在锂金属负极表面进行均匀沉积，抑制锂枝晶生长，从而大幅度降低锂金属电池发生内短路的风险，提高安全性能。
在一些实施方式中，聚合物修饰层可包括聚醚、聚酯和聚亚胺中的一种或几种。作为示例，聚醚可包括但不限于聚环氧乙烷、聚环氧丙烷、聚乙二醇、聚乙二醇二甲醚中的一种或几种。聚亚胺可包括但不限于聚酰亚胺等。聚酯可包括但不限于 聚碳酸酯、聚硫酸酯和聚磺酸酯中的一种或几种。在一些实施例中，聚合物修饰层中的聚合物还可包括其它可用于固态电解质膜的聚合物；例如，聚烯烃类(例如聚乙烯、聚丙烯、聚偏氟乙烯、聚氯乙烯等)、聚腈类(例如聚丙烯腈等)、聚羧酸酯(例如聚甲基丙烯酸甲酯、聚丙烯酸甲酯等)。
在一些实施方式中，聚合物修饰层包括聚碳酸酯、聚硫酸酯、聚亚硫酸酯和聚磺酸酯中的一种或几种。聚碳酸酯可包括但不限于式(H1)所示的环状碳酸酯中的一种或几种的聚合物、以及它们的卤代衍生物中的一种或几种。聚硫酸酯可包括但不限于式(H2)所示的环状硫酸酯中的一种或几种的聚合物、以及它们的卤代衍生物中的一种或几种。聚亚硫酸酯可包括但不限于式(H3)所示的环状亚硫酸酯中的一种或几种的聚合物、以及它们的卤代衍生物中的一种或几种。聚磺酸酯可包括但不限于式(H4)所示的环状磺酸酯中的一种或几种的聚合物、以及它们的卤代衍生物中的一种或几种。在本文中，卤代衍生物表示有机物中的一个或多个氢被卤素取代。卤素包括F、Cl、Br、I。
Figure PCTCN2021128641-appb-000003
在任意实施方式中，R 11、R 12、R 13、R 14、R 15、R 16在出现时分别独立地表示氢原子、卤素原子、碳原子数为1～4的烷基或碳原子数为1～4的卤代烷基。“卤素原子”包括F、Cl、Br、I。“碳原子数为1～4的烷基”包括含1～4个碳原子的直链或支链饱和烃基，例如甲基、乙基、丙基(如正丙基、异丙基)、丁基(如正丁基、异丁基、仲丁基、叔丁基)等类似烷基。“碳原子数为1～4的卤代烷基”表示碳原子数为1～4的烷基中的一个或多个氢被卤素原子所取代，例如被F取代。碳原子数为1～4的卤代烷基的示例可包括-CH 2F、-CHF 2、-CF 3、-CH 2CF 3、-C 2F 5、-(CH 2) 2CF 3、-C 3F 7、-(CH 2) 3CF 3、-C 4F 9，但并不限于此。
在任意实施方式中，t在出现时表示1、2、3或4，例如表示1或2。
在一些实施方式中，修饰层的聚合物中包含F、Cl、Br、I中的一种或几 种。作为示例，聚合物的单体单元中含有F。通过引入F等卤素，可以与锂形成LiF等物质，能提高锂金属负极的表面稳定性，从而改善锂金属负极与电解质之间的界面稳定性，能进一步提高电池的循环性能。另外，电池还可以获得更好的首周放电比容量和首周充放电效率。
聚合物修饰层是由路易斯酸催化单体在锂基金属层的表面原位聚合得到。单体可以是前文所述的聚合物对应的单体。在一些实施例中，单体可选自环状碳酸酯(例如碳酸亚乙酯、碳酸亚丙酯等)、环状硫酸酯(例如硫酸亚乙酯、硫酸亚丙酯等)、环状亚硫酸酯(例如亚硫酸亚乙酯、亚硫酸亚丙酯等)、环状磺酸酯(例如1,3-丙烷磺酸内酯等)及其卤代衍生物中的一种或几种。在一些实施例中，单体可包括环状碳酸酯及其卤代衍生物中的一种或多种。作为示例，单体可包括碳酸亚乙酯(EC)、碳酸亚丙酯(PC)及它们的卤代衍生物中的一种或几种。前述卤代衍生物例如是氟代衍生物。在一些实施例中，单体可包括碳酸亚乙酯和氟代碳酸亚乙酯(FEC)中的一种或几种，例如包括氟代碳酸亚乙酯。
在一些实施方式中，路易斯酸选自式(1)所示的化合物中的一种或几种：A nL m(1)。
A表示Al、Zn、Mg、Pb、Ge、Sn或Sb的阳离子。可选的，A表示Al或Zn的阳离子。合适的A与锂形成的锂合金可以具有更好的亲锂性和锂离子迁移性能，能进一步提高电池的安全性能和循环性能。
L独立地表示F－、Cl－、Br－、I－或式(2)所示阴离子。
Figure PCTCN2021128641-appb-000004
式(2)中，X和Y分别独立地表示F、Cl、Br、I、碳原子数为1～4的烷基、或碳原子数为1～4的卤代烷基。作为示例，碳原子数为1～4的烷基选自甲基、乙基、丙基(如正丙基、异丙基)、丁基(如正丁基、异丁基、仲丁基、叔丁基)等类似烷基。碳原子数为1～4的卤代烷基可以是上述碳原子数为1～4的烷基中的一个或多个氢被卤素原子所取代，例如被F取代。
在一些实施例中，X和Y分别独立地表示F或F取代的碳原子数为1～4的烷基。F取代的碳原子数为1～4的烷基的示例包括-CH 2F、-CHF 2、-CF 3、-CH 2CF 3、-C 2F 5、-(CH 2) 2CF 3、-C 3F 7、-(CH 2) 3CF 3、-C 4F 9，但并不限于此。
式(2)中，z为0、1、2、3或4。例如，z为0或1。
在一些实施例中，L可表示F －、Cl －、Br －、I －、[(FSO 2) 2N] －、[(CF 3SO 2) 2N] －、[(FSO 2)(CF 3SO 2)N] －、[(FSO 2)(C 2F 5SO 2)N] －、或[(FSO 2)(C 4F 9SO 2)N] －。可选的，L可表示F －、Cl －、[(FSO 2) 2N] －、[(CF 3SO 2) 2N] －、[(FSO 2)(CF 3SO 2)N] －、[(FSO 2)(C 2F 5SO 2)N] －、或[(FSO 2)(C 4F 9SO 2)N] －。
在电化学充放电过程中，L中的F等卤素可以与锂形成LiF等物质，能起到 改善锂金属负极与电解质之间的界面稳定性的作用，从而能进一步提高电池的循环性能。
n和m满足：A的价数×n＝L的价数×m。
在一些实施方式中，路易斯酸可选自AlF 3、ZnF 2、AlCl 3、ZnCl 2、Al[(FSO 2) 2N] 3、Zn[(FSO 2) 2N] 2、Al[(CF 3SO 2) 2N] 3、Zn[(CF 3SO 2) 2N] 2、Al[(FSO 2)(CF 3SO 2)N] 3、Zn[(FSO 2)(CF 3SO 2)N] 2、Al[(FSO 2)(C 2F 5SO 2)N] 3、Zn[(FSO 2)(C 2F 5SO 2)N] 2、Al[(FSO 2)(C 4F 9SO 2)N] 3、Zn[(FSO 2)(C 4F 9SO 2)N] 2中的一种或几种。可选的，路易斯酸可选自AlF 3、ZnF 2、AlCl 3、ZnCl 2、Al[(FSO 2) 2N] 3、Zn[(FSO 2) 2N] 2、Al[(CF 3SO 2) 2N] 3、Zn[(CF 3SO 2) 2N] 2、Al[(FSO 2)(CF 3SO 2)N] 3、Zn[(FSO 2)(CF 3SO 2)N] 2中的一种或几种。进一步可选的，路易斯酸可选自AlF 3、ZnF 2、AlCl 3、ZnCl 2、Al[(FSO 2) 2N] 3和Zn[(FSO 2) 2N] 2中的一种或几种。更进一步可选的，路易斯酸可选自AlCl 3、ZnCl 2、Al[(FSO 2) 2N] 3(简写为Al(FSI) 3)和Zn[(FSO 2) 2N] 2中的一种或几种。
在一些实施方式中，在形成聚合物修饰层的原料中，基于100重量份的单体，路易斯酸的重量份可以为1～35，例如3～30，5～25，5～20，8～16，或10～20。路易斯酸与单体的配比适当，能引发单体聚合胶化，使修饰层获得良好的强度和柔性，从而使其有效发挥抑制短路的作用，提高电池的安全性能。同时，单体聚合时反应温和，大大减少强烈反应引起的聚合物分解，以及锂金属负极的表面钝化，由此使得电池在循环中后期也能保持较高的充放电稳定性，提升循环寿命，还可以使电池获得较高的首周放电比容量和首周库伦效率。
在一些实施方式中，聚合物修饰层还包括锂盐。通过在聚合物修饰层中添加锂盐，能使修饰层获得或增强离子电导率，降低电池的极化，从而有利于电池获得更高的循环性能。
在一些实施例中，锂盐可包括有机锂盐和无机锂盐中的一种或几种。其可以选自本领域已知的电解质锂盐。作为示例，锂盐可包括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)、LiBOB(二草酸硼酸锂)、LiDFOB(二氟草酸硼酸锂)、LiTFOP(四氟草酸磷酸锂)、LiN(SO 2R F) 2和LiN(SO 2F)(SO 2R F)中的一种或几种。其中，R F表示C nF 2n+1，n为0～10的整数，例如为0～6的整数。如，n为0、1或2。可选的，R F表示F、CF 3、C 2F 5、C 3F 7、或C 4F 9。可选的，LiN(SO 2R F) 2的示例可包括LiN(SO 2F) 2(双氟磺酰亚胺锂，简写为LiFSI)、LiN(SO 2CF 3) 2(双三氟甲磺酰亚胺锂，简写为LiTFSI)等。LiN(SO 2F)(SO 2R F)的示例可包括LiFSI、LiN(SO 2F)(SO 2CF 3)等。
在一些实施例中，锂盐可选自LiFSI、LiDFOB、LiN(SO 2F)(SO 2CF 3)中的一种或几种。
通过修饰层中锂盐的设计与添加，可以使修饰层获得良好的成膜效果，从而改善电池的循环性能。
在一些实施方式中，锂盐在聚合物修饰层中的重量占比≤60％，例如为5％～60％，10％～40％，5％～20％，10％～20％，5％～15％，或15％～25％。锂盐在修饰 层中的含量适当，可以使修饰层获得良好的成膜质量以及较高的离子电导率，从而改善电池的安全性能和循环性能。
可以采用本领域已知的方法测试修饰层中锂盐的重量占比，例如离子色谱法。作为具体的示例，用水浸润浸润稀释层，使锂盐溶解于水中，获得水溶液；采用离子色谱仪测试水溶液中的阴离子含量，根据阴离子含量得到锂盐的重量；计算锂盐在修饰层中的重量占比。测试可参考JY/T 020-1996《离子色谱分析方法通则》。
在一些实施方式中，聚合物修饰层还可选的包括无机填料。无机填料可选的包括D iE j中的一种或几种，i和j满足：D的价数×i＝E的价数×j。D可包括B、Si、P、Ti、Al、Mg、Zr、Zn、Fe、Ba、Pd、Li中的一种或几种。E可表示O、N、S或PO 4。例如，无机填料可包括二氧化硅(SiO 2)、氧化钛(TiO 2)、氧化铝(Al 2O 3)、氧化镁(MgO)、氧化锆(ZrO 2)、氧化锌(ZnO)、氧化铁(Fe 3O 4)、钛酸钡(BaTiO 3)、钛酸铅(PbTiO 3)、氮化锂(Li 3N)、铝酸锂(LiAlO 2)、蒙脱土和分子筛中的一种或几种。在聚合物修饰层中含有无机填料，有利于增加膜层中的离子传输通道，由此能改善锂沉积，并且提高修饰层的离子电导率，从而进一步改善电池的循环性能。
在一些实施方式中，无机填料的体积平均粒径D v50为50nm～1000nm，例如为50nm～100nm，50nm～300nm，50nm～350nm，100nm～800nm，100nm～500nm，150nm～350nm，或500nm～1000nm。无机填料的粒径在适当范围内，能进一步改善修饰层的离子电导率，还可以改善修饰层的机械强度，提高电池循环寿命。
在本申请中，无机填料的体积平均粒径D v50为本领域公知的含义，可采用本领域已知的方法进行测试。例如激光粒度分析仪(如Malvern Master Size 3000)测试。测试可参照GB/T 19077.1-2016。其中：D V50表示无机填料累计体积分布百分数达到50％时所对应的粒径。
在一些实施方式中，无机填料在修饰层中的重量占比≤10％。可选的，无机填料在修饰层中的重量占比为1％～10％，1％～5％，2％～6％，3％～8％，或3％～5％。修饰层中无机填料的含量适当，既能发挥无机填料改善修饰层离子传输的作用，还有利于使修饰层兼具适当的机械强度和柔性，由此能改善锂金属负极与隔离膜或固态电解质膜(例如无机固态电解质膜)之间界面接触，降低界面阻抗，从而进一步改善锂的沉积/溶出行为，使电池获得更好的安全性能和循环性能。
可以采用本领域已知的方法测试修饰层中无机填料的重量占比。作为示例，可以采用碳酸二甲酯、水将修饰层依次洗涤3次；将得到的固体材料在120℃烘干后，称重，获得修饰层中无机填料的重量；计算无机填料在修饰层中的重量占比。
在一些实施方式中，聚合物修饰层的厚度可以为100nm～10μm。例如，聚合物修饰层的厚度为200nm～7μm，300nm～5μm，500nm～3μm，1μm～5μm，1μm～3μm，2μm～5μm，或2μm～4μm。聚合物修饰层具有适当的厚度，可以充分发挥改善锂沉积的作用，有效提升电池的安全性能；同时还可以使电池具有较低的阻抗，改善电池的循环性能。另外，电池还有利于获得较高的能量密度。
在本申请中，可以采用本领域已知的方法测试聚合物修饰层的厚度。示例 性测试方法如下：将锂金属负极进行液氮淬断，采用环境扫描电子显微镜(SEM，例如Quanta200FEI，荷兰FEI公司)测试锂金属负极的截面形貌及厚度。作为具体的示例，SEM放大倍数为1000倍，取5个不同区域的厚度值，计算出平均值，作为聚合物修饰层的厚度。
在一些实施方式中，聚合物修饰层的压缩弹性模量为0.01MPa～1MPa，进一步可选的为0.02MPa～0.78MPa，0.1MPa～0.8MPa，0.3MPa～0.8MPa，0.4MPa～0.78MPa，或0.5MPa～0.75MPa。聚合物修饰层具有柔性，可以进一步改善锂金属负极与隔离膜或固态电解质膜(例如无机固态电解质膜)之间界面接触，降低界面阻抗，因而更加改善锂的沉积/溶出行为，从而能进一步提升电池的安全性能和循环性能。
在本申请中，可以将制备聚合物修饰层的混合溶液涂布在不锈钢基材上，使其发生催化聚合反应，得到凝胶化产物；将凝胶化产物切成直径为10mm，厚度为1mm～5mm(例如1mm)的圆柱体样品；将样品放在电子万能力学试验机MTS Exceed E43上进行压缩测试，压缩速率为10％厚度/min，每种样品取5个平行样进行实验，取其平均值。凝胶的压缩弹性模量E是以压缩比为5％以内的数据进行线性拟合来计算的，计算公式如下：
E＝σ·l/(S·Δl)，式中：E表示压缩弹性模量(单位，Pa)；σ表示压力(单位，N)；l表示样品未压缩变形前的厚度(单位，m)；S表示样品未压缩变形前的面积(单位，m 2)；Δl表示样品受压变形的厚度(单位，m)。
在一些实施方式中，锂基金属层可包括金属锂和锂合金中的一种或几种。锂合金中锂元素的含量可选为30wt％以上，50wt％以上，70wt％以上，90wt％以上，95wt％以上，97wt％以上，或99wt％以上。锂合金可包括但不限于锂铟合金、锂锌合金、锂镁合金、锂锡合金和锂银合金中的一种或几种。
在一些实施方式中，锂基金属层的厚度可以为1μm～200μm，例如3μm～120μm，5μm～100μm，10μm～60μm，15μm～50μm，或20μm～30μm。
在本申请的锂金属负极中，负极集流体可采用金属箔片或复合集流体(可以将金属材料设置在高分子基材上形成复合集流体)。作为示例，负极集流体可采用铜箔、涂炭铜箔、或不锈钢片。
本申请还提供一种锂金属负极的制备方法，根据该制备方法能制备得到上述任意一种锂金属负极。锂金属负极的制备方法包括如下步骤：
提供待修饰的锂金属负极。待修饰的锂金属负极包括负极集流体及设置于负极集流体至少一个表面上的锂基金属层。
提供混合溶液，混合溶液包含单体和路易斯酸。
使混合溶液覆盖于至少一个锂基金属层的表面，路易斯酸催化单体发生聚合，形成导离子的聚合物修饰层，得到锂金属负极。
待修饰的锂金属负极可以商购获得，或采用本领域已知的方法制备得到。作为一个示例，可以将锂基金属箔层压复合于负极集流体的任意一个表面或相对的两个表面上，得到待修饰的锂金属负极。锂基金属箔可以是金属锂箔或锂合金箔片。
混合溶液中，路易斯酸和单体可分别选自如本文所描述的那些中的一种或几种。路易斯酸和单体的配比可以如前文所述。
在一些实施方式中，在混合溶液中还包括反应缓和剂。反应缓和剂可以调控反应速率，避免反应太激烈而大量放热，由此可以使反应在温和的条件下进行，防止聚合物分解。聚合物修饰层为质量良好的胶状弹性膜层，能有效发挥改善电池安全性能和循环性能的作用。
在一些实施例中，反应缓和剂可包括碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲乙酯(EMC)、甲酸甲酯、甲酸乙酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、乙酸乙酯、N-甲基吡咯烷酮、N-甲基甲酰胺、N-甲基乙酰胺、乙腈、环丁砜、二甲亚砜、甲硫醚、二乙基亚硫酸酯、亚硫酸二甲酯、四氢呋喃、如式(I)所示的环状酯中的一种或几种。
Figure PCTCN2021128641-appb-000005
式(I)中，Q表示O或S。式(I)所示的环状酯可包括(I-1)和(I-2)中的一种或几种。
Figure PCTCN2021128641-appb-000006
在各实施方式中，R 1和R 2独立地表示H、F、或碳原子数为1～4的氟代烷基。“碳原子数为1～4的氟代烷基”表示碳原子数为1～4的烷基中的一个或多个氢被F取代。碳原子数为1～4的烷基可以如本文所描述。作为示例，R 1和R 2独立地表示H、F、-CH 2F、-CHF 2、-CF 3、-CH 2CF 3、-C 2F 5、-(CH 2) 2CF 3、-C 3F 7、-(CH 2) 3CF 3、-C 4F 9，但并不限于此。
在各实施方式中，R 3表示碳原子数为1～3的氟代亚烷基。“碳原子数为1～3的氟代亚烷基”表示碳原子数为1～3的烷基中的一个或多个氢被F取代。碳原子数为1～3的烷基包括含1～3个碳原子的直链或支链饱和烃基，例如甲基、乙基、丙基(如正丙基、异丙基)等类似烷基。作为示例，R 3可表示-CH 2F、-CHF 2、-CF 3、-CH 2CF 3、-C 2F 5、-(CH 2) 2CF 3、-C 3F 7，但并不限于此。
在一些实施方式中，反应缓和剂可包括碳酸二甲酯(DMC)、碳酸二乙酯 (DEC)、碳酸二丙酯(DPC)、碳酸甲乙酯(EMC)中的一种或几种。例如，反应缓蚀剂包括碳酸甲乙酯。
在一些实施方式，在混合溶液中，基于100重量份的单体，反应缓和剂的重量份可以大于0且小于等于800。例如，基于100重量份的单体，反应缓和剂的重量份为50～750，60～500，60～200，70～350，70～300，80～250，100～200，或120～185等。反应缓和剂的含量适当，有利于控制反应速率，减少聚合反应过程中的界面副反应，提高界面稳定性，同时还使聚合物修饰层获得适宜的强度和柔性，从而能提高电池的安全性能和循环性能，还能提升首圈放电比容量和首圈库伦效率。
在一些实施方式中，混合溶液还可选的包括锂盐。锂盐可选自本文所描述的锂盐中的一种或几种。
在一些实施方式中，锂盐的含量基于100重量份的单体计为200重量份以下，例如10～200，20～150，25～100，30～80，或40～60重量份。
在一些实施方式中，混合溶液还可选的包括无机填料。无机填料可选自本文所描述的无机填料中的一种或几种。
在一些实施方式中，在混合溶液中，无机填料的含量基于100重量份的单体计为30重量份以下，例如为20重量份以下，或10重量份以下。可选的，基于100重量份的单体，混合溶液中无机填料的含量为1～30，3～20，5～15，5～10，8～15，10～20，或10～15重量份。
在一些实施方式中，可以将待修饰锂金属负极浸渍于混合溶液中，或将混合溶液涂覆于待修饰锂金属负极的锂基金属层表面，从而使混合溶液覆盖于锂基金属层的表面。在路易斯酸的催化作用下，使单体在待修饰锂金属负极的锂基金属层表面发生原位聚合反应。其中浸渍和涂覆可采用本领域已知的方法。例如，可通过刮涂、旋涂、喷涂等方式将将混合溶液涂覆于锂基金属层表面。
将混合溶液覆盖于锂基金属层表面后，可以静置5min～50h，来完成聚合反应，得到聚合物修饰层。可选的，静置的时间为10min～10h，15min～120min，20min～100min，20min～60min，30min～150min，30min～90min，或40min～60min。
本申请还提供一种锂金属电池。根据本申请的锂金属电池包括正极极片和负极极片，负极极片为本申请任意的锂金属负极。
本申请的锂金属电池由于采用本申请的锂金属负极，因而能在具有较高能量密度的条件下，提升安全性能。另外，锂金属电池还可以兼具较高的循环性能、首周放电比容量和首次充放电效率。
[正极极片]
本申请的锂金属电池中，正极极片包括正极集流体以及设置在正极集流体至少一个表面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，正极膜层设置于正极集流体的两个相对表面中的任意一者或两者上。
正极集流体可采用金属箔片或复合集流体(可以将金属材料设置在高分子 基材上形成复合集流体)。作为示例，正极集流体可选自铝箔、涂炭铝箔、或不锈钢片。
正极活性材料可采用本领域公知的用于锂离子电池的正极活性材料。例如，正极活性材料可包括层状锂过渡金属氧化物、尖晶石结构锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性材料中的一种或几种。层状锂过渡金属氧化物的示例可包括但不限于钴酸锂(例如LiCoO 2)、镍酸锂(例如LiNiO 2)、三元材料(例如LiNi sB tC (1-s-t)O 2(其中，B、C独立地选自Co、Al、Mn，且B和C不同，0<s<1，0<t<1))及其改性材料中的一种或几种。尖晶石结构锂过渡金属氧化物可包括但不限于锰酸锂(LiMn 2O 4)、镍锰酸锂(LiNi 0.5Mn 1.5O 4)及其改性材料中的一种或几种。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(LiFePO 4)、磷酸钴锂(LiCoPO 4)、磷酸锰锂(LiMnPO 4)、磷酸镍锂(LiNiPO 4)、磷酸铁(FePO 4)及其各自的改性材料中的一种或几种。
在一些实施方式中，为了进一步提高电池的能量密度，正极活性材料可包括式(3)所示的锂过渡金属氧化物及其改性化合物中的一种或几种，
Li aNi bCo cM dO eA f        (3)，
式(3)中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，A选自N、F、S及Cl中的一种或几种。
可选的，0.5≤b≤0.9，0.5≤b≤0.8，0.6≤b≤0.8，或0.6≤b≤0.75。采用该锂过渡金属氧化物，可以提升电池的工作电压窗口，使电池获得较高的能量密度，同时还兼具较高的循环性能。
可选的，M选自Mn和Al中的一种或几种。
可选的，A为F。
在本申请中，上述各材料的改性材料可以是对正极活性材料进行掺杂改性或表面包覆改性。掺杂和包覆的元素可独立地选自金属元素和非金属元素，例如Li、N、F、Cl、S、B、P、Al、Si、Zr、Ti、Ge、Sn、Mg、Zn、Ce、W、V等的一种或几种。
本申请的锂金属电池中，正极膜层通常包含正极活性材料以及可选的正极固态电解质、可选的粘结剂和可选的导电剂，通常是由正极浆料涂布，并经干燥、压实而成的。正极浆料通常是将正极活性材料以及可选的正极固态电解质、可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。正极浆料的混合方式可以采用行业内公知的混料方式，如磁力搅拌、机械球磨等。
在一些实施方式中，正极膜层包含正极固态电解质。该正极膜层可以与固态电解质膜和锂金属负极制成固态锂金属电池。固态锂金属电池由于采用固态电解质膜，无电解液泄露风险，同时还能抑制锂枝晶的刺穿，因此可以提升安全性能。
正极固态电解质可采用本领域已知的材料，可根据实际需求进行选择。例如，正极固态电解质可以是硫化物固态电解质、氧化物固态电解质、聚合物固态电解质中的一种或几种。
在一些实施例中，氧化物电解质可包括具有NASICON(Na +super ionic conductor，Na快离子导体)结构的化合物(例如NaE 2(PO 4) 3，其中E表示Ti、Zr或Ge)、具有LISICON(Li +super ionic conductor，Li快离子导体)结构的化合物(例如Li 14Zn(GeO 4) 4)、具有石榴石(Garnet)结构的化合物(例如Li 7La 3L 2O 12，其中L表示Zr或Sn)和具有钙钛矿结构的化合物(例如Li 3xLa 1-3xTiO 3，其中0<x<0.16)中的一种或几种。
在一些实施例中，硫化物电解质可包括Li 10MP 2S 12、Li 6(P 1-aM a)S 5X、Li 3PS 4、Li 7P 3S 11，其中M为Ge、Si、Sn、Sb中的一种或几种；X为F、Cl、Br、I中的一种或几种；0.01≤a≤1。作为示例，氧化物电解质可选自Li 3PS 4、Li 10GeP 2S 12、Li 6PS 5Cl中的一种或几种。
在一些实施例中，聚合物固态电解质可包括聚醚类(PEO)、聚丙烯腈类(PAN)、聚丙烯酸酯类(PMMA)、聚偏二氟乙烯类(PVDF)中的一种或几种。
在一些实施方式中，粘结剂可以包括苯乙烯-丁二烯-苯乙烯三嵌段热塑性弹性体(SBS)、乙烯-丁烯共聚物(SEBS)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸锂(PAALi)、丁苯橡胶、丁腈橡胶、丁烯橡胶、苯乙烯橡胶或聚氨酯中的一种或几种。
在一些实施方式中，导电剂可以包括导电炭黑(super-P)、乙炔黑、气相生长炭纤维(Vapor-grown carbon fiber，简称VGCF)、碳纳米管、石墨烯中的一种或几种。
在正极浆料中，溶剂可选自有机溶剂，例如醚类溶剂、烃类溶剂、酯类溶剂、腈类溶剂、酰胺类溶剂、醇类溶剂、卤代烃类溶剂中的一种或几种。具体的，醚类溶剂可选自乙醚、四氢呋喃(THF)、乙二醇二甲醚中的一种或几种。烃类溶剂可选自正戊烷、正己烷、环己烷、甲苯、二甲苯、三甲苯中的一种或几种。酯类溶剂可选自乙酸乙酯、甲酸甲酯、邻苯二甲酸二甲酯中的一种或几种。腈类溶剂可包括乙腈。酰胺类溶剂可选自N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)中的一种或几种。醇类溶剂可包括乙醇。卤代烃类溶剂可选自二氯甲烷、1,2-二氯乙烷中的一种或几种。在一些实施例中，正极浆料的溶剂可以是N-甲基吡咯烷酮(NMP)和/或四氢呋喃(THF)。
干燥和压实采用本领域已知的方法和设备进行。在一些实施例中，正极浆料包含正极固态电解质，干燥、压实可选的在保护气体保护下进行。保护气体可以为氮气或惰性气体，例如氩气。在这些实施例中，压实的压力可以为20MPa～500MPa，例如200MPa～300MPa。压实的温度可以为20℃～160℃，例如20℃～100℃。正极活性材料层的压实密度可以为1.8g/cm 3～4.2g/cm 3，例如2.8g/cm 3～4.0g/cm 3。
在一些实施方式中，正极活性材料层中包含正极活性材料、正极固态电解质、导电剂和粘结剂。合理调控正极活性材料层中各组分的含量可以构建良好的电子和锂离子导通网络，提升电池的循环性能。
可选的，正极活性材料在正极活性材料层中的质量占比为48％～90％，例 如60％～75％，70％～85％，或65％～80％。正极活性材料在正极活性材料层中具有合适的占比，既有利于电子和锂离子的传递，还有利于电池获得较高的能量密度。可选的，正极固态电解质在正极活性材料层中的质量占比为8％～50％，例如10％～40％，15％～30％，或10％～25％。导电剂在正极活性材料层中的质量占比可以为1％～10％，例如2％～8％，3％～6％，4％～7％，或2％～5％。粘结剂在正极活性材料层中的质量占比可以为1％～10％，例如2％～8％，3％～6％，4％～7％，或2％～5％。
在一些实施方式中，正极活性材料层的厚度可以为10μm～200μm。例如，正极活性材料层的厚度为40μm～160μm，60μm～120μm，或80μm～140μm等。正极活性材料层的厚度在适当范围内，有利于提高正极的容量，使电池获得较高的能量密度；同时还可以使正极活性材料层内具有较低的锂离子传输阻抗，减小极化，从而使电池兼具较高的循环性能。
[电解质]
本申请的锂金属电池中，电解质可以采用本领域已知的电解质，本领域技术人员可根据需求选择。例如，电解质可选自固态电解质膜、或液态电解质(即电解液)。
在一些实施方式中，电解质采用固态电解质膜。固态电解质膜设置于负极极片和正极极片之间，进行传导离子。固态电解质膜可选自无机固态电解质膜、固态聚合物电解质膜及无机-有机复合固态电解质膜中的一种或几种。相较于电解液来说，采用固态电解质膜没有液体泄露的风险，进一步提高电池的安全性能。在这些实施例中，锂金属电池为全固态电池或半固态电池。
在一些实施例中，固态电解质膜选自无机固态电解质膜。采用无机固态电解质膜有利于提升电池的电压窗口，从而可提升能量密度。锂金属负极表面具有聚合物修饰层，其具有适当的柔性，可显著改善锂金属负极与无机固态电解质膜之间的接触，降低界面阻抗，并且聚合物修饰层还可以改善锂的沉积和溶出，因此能大幅度减少锂枝晶的生长，降低电池内短路风险，提升安全性能。进一步地，电池的循环性能也能得到改善。
无机固态电解质膜包括无机固态电解质和可选的粘结剂。
在无机固态电解质膜中，无机固态电解质可包括氧化物电解质和硫化物电解质中的一种或几种。
在一些实施例中，氧化物电解质可包括NASICON结构的化合物、具有LISICON结构的化合物、具有石榴石结构的化合物和具有钙钛矿结构的化合物中的一种或几种。作为示例，氧化物电解质可选自NaE 2(PO 4) 3，其中E表示Ti、Zr或Ge；Li 14Zn(GeO 4) 4；Li 7La 3L 2O 12，其中L表示Zr或Sn；Li 3xLa 1-3xTiO 3，其中0<x<0.16。
在一些实施例中，硫化物电解质可包括Li 10MP 2S 12、Li 6(P 1-aM a)S 5X、Li 3PS 4、Li 7P 3S 11，其中M选自Ge、Si、Sn、Sb中的一种或几种；X选自F、Cl、Br、I中的一种或几种；0.01≤a≤1。作为示例，氧化物电解质可选自Li 3PS 4、Li 10GeP 2S 12、Li 6PS 5Cl中的一种或几种。
在无机固态电解质膜中，粘结剂可以选自苯乙烯-丁二烯-苯乙烯三嵌段热塑 性弹性体(SBS)、乙烯-丁烯共聚物(SEBS)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸锂(PAALi)、偏氟乙烯-六氟丙烯共聚物(PVDF-HFP)、丁苯橡胶、丁腈橡胶、丁烯橡胶、苯乙烯橡胶或聚氨酯中的一种或几种。
在无机固态电解质膜中，无机固态电解质和粘结剂质量比可以为99～50:1～50，例如98～80:2～20。无机固态电解质和粘结剂的质量比在适当范围内，可以使无机固态电解质膜获得较高的强度和韧性，以及较高的锂离子的传输性能，因此能提升电池的循环性能。
无机固态电解质膜可商购获得或采用本领域已知的方法制备得到，例如由包含无机固态电解质和可选的粘结剂的电解质浆料成膜获得。示例性制备方法如下：将无机固态电解质和粘结剂分散于有机溶剂中形成电解质浆料；将电解质浆料均匀涂布于基材(例如塑料基材、玻璃基材等)上，干燥后，经加压压制成型，得到无机固态电解质膜。
电解质浆料中，有机溶剂需不与固态电解质发生反应，例如可选自醚类溶剂、烃类溶剂、酯类溶剂、腈类溶剂、酰胺类溶剂、醇类溶剂、卤代烃类溶剂中的一种或几种。例如，它们分别可以包括本文所描述的那些。在一些实施例中，有机溶剂包括N-甲基吡咯烷酮(NMP)和/或四氢呋喃(THF)。
在无机固态电解质膜的制备中，有机溶剂的用量可根据电解质浆料粘度进行调控。可选的，电解质浆料的粘度为5000mPa·s～200000mPa·s，例如5000mPa·s～100000mPa·s，或10000mPa·s～50000mPa·s。电解质浆料的粘度在适当范围内，可以方便涂膜，并且可以减少无机固态电解质膜中的孔洞，在一定程度上降低电池内短路的风险，提高安全性能。
浆料的涂布、干燥和加压压制均可以采用本领域已知的方法和设备进行。在一些实施方式中，干燥步骤可包括：将涂层自然晾干1～1.5小时后，再真空干燥1～3小时。
在一些实施方式中，加压方式可以是一步压制，也可以是分步压制。加压压力可以为1MPa～500MPa，例如100MPa～300MPa。加压温度可以为20℃～160℃，例如20℃～100℃，40℃～100℃，或60℃～90℃。加压压力和温度在适当范围内，有利于膜片获得较高的致密度，使膜片具有良好的强度；并且还能确保固态电解质膜具有良好的离子传输性能。
在一些实施方式中，电解质还可以采用电解液。电解液包括电解质锂盐和溶剂。其中电解质锂盐和溶剂均可以采用本领域已知的物质，本领域技术人员可以根据需要选择。
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。
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、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯(FEC)、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的一种或几种。
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。
采用电解液的锂金属电池、以及半固态锂金属电池中，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隔离膜。在一些实施方式中，隔离膜可选自玻璃纤维膜、无纺布、聚乙烯膜、聚丙烯膜及聚偏二氟乙烯膜中的一种或包含它们中的两种以上的多层复合薄膜。
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。作为一个示例，将正极极片、无机固态电解质膜和锂金属负极依次堆叠，其中无机固态电解质膜介于正极极片和锂金属负极之间；将堆叠单元加压复合在一起，形成固态锂金属电池的电极组件。其中，加压复合的压力可以为1MPa～500MPa，例如100MPa～300MPa。加压复合的温度为20℃～160℃，例如25℃～60℃，或60℃～120℃。
在一些实施方式中，锂金属电池可包括外包装。外包装可用于封装电极组件，以及需要时的电解液。
在一些实施方式中，锂金属电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。锂金属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。
本申请对锂金属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锂金属电池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，以封闭容纳腔。正极极片、无机固态电解质膜和锂金属负极可经叠片工艺形成电极组件52。电极组件52封装于容纳腔。锂金属电池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，锂金属电池可以组装成电池模块，电池模块所含锂金属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，多个锂金属电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂金属电池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，多个锂金属电池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。
本申请还提供一种装置，所述装置包括本申请的锂金属电池、电池模块、或电池包中的至少一种。锂金属电池、电池模块或电池包可以用作装置的电源，也可以用作装置的能量存储单元。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。
装置可以根据其使用需求来选择锂金属电池、电池模块或电池包。
图7是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。该装置可以采用电池包或电池模块。
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
1、混合溶液制备
向LiFSI/FEC/EMC(质量比15:30:55)的单体溶液中加入3％的路易斯酸AlCl 3，混合均匀，得到混合溶液。其中，路易斯酸的添加量(％)＝路易斯酸的质量/单体溶液的质量×100％。经计算，基于100重量份的单体FEC，路易斯酸AlCl 3为10重量份，锂盐LiFSI为50重量份，反应缓和剂为183.3重量份。
2、锂金属负极制备
在干燥房中，将25μm锂金属箔通过压延法贴于铜箔表面，切片。使用刮刀将上述混合溶液涂覆于锂金属层表面，静置50min后，在锂金属层表面形成厚度为3μm的聚合物修饰层。
3、正极极片制备
手套箱中，将正极活性材料LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、硫化物固态电解质Li 3PS 4、导电剂VGCF、粘结剂丁苯橡胶(数均分子量约为50万)按重量比70:20:5:5，混合于THF溶剂中，充分搅拌混合均匀后，得到正极浆料；将正极浆料涂覆于铝箔表面，自然晾干后经60℃烘干、冷压、切片，得到正极极片。其中，正极活性材料层的厚度为50μm，压实密度为3g/cm 3。
4、无机固态电解质膜制备
手套箱中，将硫化物固态电解质Li 3PS 4和粘结剂丁苯橡胶按重量比99:1，混合于THF溶剂中，配制成电解质浆料；将电解质浆料涂于玻璃基材表面，并在60℃下干燥，再进行切片后，得到硫化物固态电解质膜。其中硫化物固态电解质膜的厚度为50μm。
5、全固态锂金属电池制备
将正极极片、硫化物固态电解质膜、锂金属负极按顺序中心对齐叠片，在室温(25℃)、250MPa下冷压2min得到叠片单元；将10个叠片单元叠层并冷压后，置于外包装中封装，经成型后得到固态锂金属电池。
6、Li/Li对称电池制备
将上述锂金属负极、硫化物固态电解质膜、锂金属片按顺序中心对齐叠片，在室温、250MPa下冷压2min得到叠片单元，然后置于外包装中封装，经成型后，得到固态对称锂金属电池。
实施例2～19及对比例1～3
制备方法与实施例1类似，不同的是：调控锂金属负极制备步骤中的相关参数，得到相应的锂金属电池，详见表1。
实施例17中，无机填料采用粒径为500nm的Al 2O 3，其中无机填料的添加量(％)＝无机填料的质量/单体溶液的质量×100％。
测试部分
1、Li/Li对称电池的测试
采用恒流充放电的方式进行循环测试，其中，沉积与溶出容量限定为6mAh/cm 2，测试电流密度约为0.39mA/cm 2，测试温度为25℃。
图8示出了实施例1和对比例1的Li/Li对称锂金属电池的循环曲线。由图8可知，实施例1的Li/Li对称电池采用本申请的锂金属负极，其中在锂基金属层表面由路易斯酸催化形成导离子聚合物修饰层，并且路易斯酸中含有能与锂形成合金系活性材料的金属的阳离子，由此提高了锂金属负极与无机固态电解质膜之间的界面稳定性，使得Li/Li对称电池表现出良好的循环稳定性。其中首周过电位高于第二周，可能原因在于发生了锂合金化过程。而对比例1的Li/Li对称电池采用未修饰的锂金属负极，其充放电曲线较为紊乱，前期过电位较高，锂负极表面与电解质之间的副反应发生，导致两者界面阻抗较大，循环后期发生快速的电压变化，极化严重。
2、固态锂金属电池的测试
1)25℃下，将实施例和对比例制备得到的固态锂金属电池采用恒流充放电的方式进行测试，具体为：以0.1C(电流密度约为0.13mA/cm 2)恒流充电至电压为4.2V，之后恒压充电至电流为0.05C，记录首周充电比容量；静置5min，再以0.1C恒流放电至电压为2.8V，记录首周放电比容量。将电池按照上述的方法进行循环充放电测试，记录第200周循环的放电比容量。
固态锂金属电池的首周库伦效率＝首周放电比容量/首周充电比容量×100％。
固态锂金属电池循环200周容量保持率＝第200周放电比容量/首周放电比容量×100％。
2)短路率：按照1)中的方法将电池进行200周循环充放电测试，统计100块固态锂金属电池的测试过程中，发生短路的固态锂金属电池的数量，统计发生短路的固态锂金属电池所占的比例。
实施例1～19以及对比例1～3的测试结果见表2。
表1
Figure PCTCN2021128641-appb-000007
Figure PCTCN2021128641-appb-000008
表2
Figure PCTCN2021128641-appb-000009
由表2的结果再次证明，本申请的锂金属负极中，通过在锂基金属层表面由路易斯酸催化形成导离子聚合物修饰层，并且路易斯酸中含有能与锂形成合金系活性材料的金属的阳离子，能有效降低采用其的锂金属电池发生内短路的风险，提高了电池的安全性能。进一步地，通过优化聚合物修饰层的制备参数或结构参数，能在提升电池安全性能的同时，还使电池获得较高的循环性能、首周放电比容量和首周库伦效率。
对比例1～3不满足本申请的条件，锂金属电池发生内短路的风险较大，降低了电池的安全性能，另外还不利于电池循环性能、首周放电比容量和首周库伦效率的改善。
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 (23)

  1. 一种锂金属负极，包括：
    负极集流体；
    至少一个锂基金属层，设置于所述负极集流体的至少一个表面上；以及
    导离子的聚合物修饰层，所述聚合物修饰层位于至少一个所述锂基金属层的表面上，并包含至少催化量的路易斯酸，所述路易斯酸包含能与锂形成合金系活性材料的金属的阳离子。
  2. 根据权利要求1所述的锂金属负极，其中，所述聚合物修饰层的厚度为100nm～10μm，可选的为300nm～5μm，进一步可选的为500nm～3μm。
  3. 根据权利要求1或2所述的锂金属负极，其中，所述路易斯酸选自式(1)所示的化合物中的一种或几种：
    A nL m  (1)
    其中，A表示Al、Zn、Mg、Pb、Ge、Sn或Sb的阳离子，可选的，A表示Al或Zn的阳离子；
    L独立地表示F －、Cl －、Br －、I －或式(2)所示阴离子，
    Figure PCTCN2021128641-appb-100001
    其中，X和Y分别独立地表示F、Cl、Br、I、碳原子数为1～4的烷基、或碳原子数为1～4的卤代烷基，可选的，X和Y分别独立地表示F或F取代的碳原子数为1～4的烷基，
    z为0、1、2、3或4；
    n和m满足：A的价数×n＝L的价数×m。
  4. 根据权利要求3所述的锂金属负极，其中，所述L表示F －、Cl －、Br －、I －、[(FSO 2) 2N] －、[(CF 3SO 2) 2N] －、[(FSO 2)(CF 3SO 2)N] －、[(FSO 2)(C 2F 5SO 2)N] －、或[(FSO 2)(C 4F 9SO 2)N] －。
  5. 根据权利要求1或2所述的锂金属负极，其中，所述路易斯酸选自AlCl 3、ZnCl 2、Al[(FSO 2) 2N] 3和Zn[(FSO 2) 2N] 2中的一种或几种。
  6. 根据权利要求1～5任一项所述的锂金属负极，其中，所述聚合物修饰层的压缩弹性模量为0.01MPa～1MPa，可选的为0.02MPa～0.78MPa。
  7. 根据权利要求1～6任一项所述的锂金属负极，其中，所述聚合物包括聚醚、聚酯和聚亚胺中的一种或几种，可选的包括聚碳酸酯、聚硫酸酯、聚亚硫酸酯和聚磺酸酯中的一种或几种。
  8. 根据权利要求1～7中任一项所述的锂金属负极，其中，所述聚合物修饰层通过 单体在所述路易斯酸的催化下，在所述锂基金属层的表面原位聚合得到。
  9. 根据权利要求8所述的锂金属负极，其中，所述单体包括环状碳酸酯、环状磺酸酯、环状硫酸酯、环状亚硫酸酯及其卤代衍生物中的一种或多种，可选的包括环状碳酸酯及其卤代衍生物中的一种或多种。
  10. 根据权利要求8所述的锂金属负极，其中，所述单体包括碳酸亚乙酯、碳酸亚丙酯及它们的卤代衍生物中的一种或几种，可选的包括碳酸亚乙酯、氟代碳酸亚乙酯中的一种或几种，进一步可选的包括氟代碳酸亚乙酯。
  11. 根据权利要求1～10任一项所述的锂金属负极，其中，所述聚合物修饰层还包括锂盐，所述锂盐在所述聚合物修饰层中的重量占比≤60％，可选的为10％～40％。
  12. 根据权利要求11所述的锂金属负极，其中，所述锂盐包括LiPF 6、LiBF 4、LiClO 4、LiAsF 6、LiBOB、LiDFOB、LiTFOP、LiN(SO 2R F) 2和LiN(SO 2F)(SO 2R F)中的一种或几种，其中R F表示C nF 2n+1，n为0～10的整数；可选的，所述锂盐包括LiN(SO 2F) 2、LiDFOB、LiN(SO 2F)(SO 2CF 3)中的一种或几种。
  13. 根据权利要求1～12任一项所述的锂金属负极，其中，所述聚合物修饰层还包括无机填料，所述无机填料在所述修饰层中的重量占比≤10％；可选的，所述无机填料在所述修饰层中的重量占比为1％～5％。
  14. 根据权利要求13所述的锂金属负极，其中，所述无机填料包括二氧化硅(SiO 2)、氧化钛(TiO 2)、氧化铝(Al 2O 3)、氧化镁(MgO)、氧化锆(ZrO 2)、氧化锌(ZnO)、氧化铁(Fe 3O 4)、钛酸钡(BaTiO 3)、钛酸铅(PbTiO 3)、氮化锂(Li 3N)、铝酸锂(LiAlO 2)、蒙脱土和分子筛中的一种或几种；和/或，
    所述无机填料的体积平均粒径D v50为50nm～1000nm，可选的为100nm～800nm。
  15. 一种锂金属负极的制备方法，包括如下步骤：
    提供待修饰的锂金属负极，所述待修饰的锂金属负极包括负极集流体及设置于所述负极集流体至少一个表面上的锂基金属层；
    提供混合溶液，所述混合溶液包含路易斯酸和单体，所述路易斯酸包含能与锂形成合金系活性材料的金属的阳离子；
    使所述混合溶液覆盖于至少一个所述锂基金属层的表面，所述路易斯酸催化所述单体发生聚合，形成导离子的聚合物修饰层，得到锂金属负极。
  16. 根据权利要求15所述的制备方法，其中，基于100重量份的所述单体，所述路易斯酸的重量份为1～35，可选的为3～30，进一步可选的为10～20。
  17. 根据权利要求15～16任一项所述的制备方法，其中，所述混合溶液还包括反应缓和剂，其中，基于100重量份的所述单体，所述反应缓和剂的重量份为大于0小于等于800，可选的为100～200。
  18. 根据权利要求17所述的制备方法，其中，所述反应缓和剂包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、甲酸甲酯、甲酸乙酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、乙酸乙酯、N-甲基吡咯烷酮、N-甲基甲酰胺、N-甲基乙酰胺、乙腈、环丁砜、二甲亚砜、甲硫醚、亚硫酸二乙酯、亚硫酸二甲酯、四氢呋喃、如式(I)所示 的环状酯中的一种或几种，可选的包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯中的一种或几种；
    Figure PCTCN2021128641-appb-100002
    其中，Q表示O或S，R 1和R 2独立地表示H、F、或碳原子数为1～4的氟代烷基，R 3表示碳原子数为1～3的氟代亚烷基。
  19. 根据权利要求15～18任一项所述的制备方法，其中，所述混合溶液还包括锂盐，所述锂盐的含量基于100重量份的所述单体计为200重量份以下，可选的为30～80重量份；和/或，
    所述混合溶液还包括无机填料，所述无机填料的含量基于100重量份的所述单体计为30重量份以下，可选的为10～20重量份。
  20. 一种锂金属电池，包括正极极片和负极极片，所述负极极片为根据权利要求1～14任一项所述的锂金属负极或权利要求15～19任一项所述的方法制备的锂金属负极。
  21. 根据权利要求20所述的锂金属电池，其中，所述正极极片包括正极集流体以及设置于所述正极集流体至少一个表面且包括正极活性材料的正极膜层，所述正极活性材料包括橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物中的一种或几种；
    可选的，所述正极活性材料包括满足式(3)的锂过渡金属氧化物及其改性化合物中的一种或几种，
    Li aNi bCo cM dO eA f  (3)
    其中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，A选自N、F、S及Cl中的一种或几种。
  22. 根据权利要求20～21任一项所述的锂金属电池，其中，所述锂金属电池还包括固态电解质膜，所述固态电解质膜设置于所述负极极片和正极极片之间；可选的，所述固态电解质膜选自无机固态电解质膜。
  23. 一种装置，包括根据权利要求20～22任一项所述的锂金属电池。
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JP7459288B2 (ja) 2024-04-01
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US20230223545A1 (en) 2023-07-13
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