Lithium metal-polymer composite negative electrode, lithium metal battery and preparation method of lithium metal-polymer composite negative electrode

Abstract

The invention provides a lithium metal-polymer composite negative electrode, a lithium metal battery and a preparation method of the lithium metal-polymer composite negative electrode. The preparation method of the lithium metal-polymer composite negative electrode comprises the following steps: dissolving a polymerizable monomer in a solvent, and mixing with a cross-linking agent and an initiator to prepare a polymerizable monomer solution; a polymerizable monomer solution is coated on the surface of a lithium metal matrix, and is cross-linked and cured on the surface of the lithium metal matrix through ultraviolet irradiation to form a polymer skeleton. According to the preparation method of the lithium metal-polymer composite negative electrode, the polymer skeleton is formed on the surface of the lithium metal matrix, so that lithium metal can be protected, dew point protection is not needed during battery assembly, the preparation method can be carried out in a conventional production environment, and the production cost and the process complexity are remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, in particular to a reusable secondary battery in new energy, and more particularly to a lithium metal-polymer composite negative electrode, a lithium metal battery, and a preparation method thereof. Background Art

[0002] With the rapid development of electric vehicles and high-end electronic devices, all-solid-state lithium batteries are considered a potentially revolutionary battery technology, promising to surpass traditional liquid electrolyte lithium batteries in terms of safety and energy density. Although graphite is a commonly used anode material in commercial batteries, its low energy density (372 mAh / g) cannot meet the requirements of electric vehicles and large-scale energy storage devices. In contrast, lithium metal, due to its ultra-high theoretical specific capacity (3860 mAh / g) and extremely low electrochemical potential (-3.04 V), has become an ideal anode material for next-generation lithium batteries. However, lithium metal is extremely sensitive to water and air, and is prone to the formation of lithium dendrites. This formation not only reduces lithium battery performance but can also lead to safety hazards such as short circuits and thermal runaway. Therefore, improving the stability and safety of lithium metal anodes in air is of paramount importance.

[0003] Currently, modification strategies for lithium metal anodes primarily focus on forming a highly stable solid electrolyte interface (SEI) through electrolyte additives to inhibit dendrite growth and enhance lithium ion conductivity. While this approach is effective, its complex preparation process and high cost limit its widespread application. Solid polymer electrolytes, as an emerging solution, offer significant advantages in preventing lithium dendrite growth, providing a tough interfacial layer, and enhancing air stability. Therefore, the use of in-situ polymerization techniques to form stable polymer films on the surface of lithium metal anodes is becoming an important research direction for improving lithium battery performance and production efficiency. This research could promote the development of all-solid-state lithium metal batteries to meet the growing market demand for high-tech electronic devices and electric vehicles.

[0004] Currently, the industry still uses traditional in-situ polymerization technology to construct a polymer electrolyte film on the lithium metal surface to protect the lithium metal anode. This involves initiating polymerization of monomers and electrolytes to form the polymer electrolyte film. While the polymer electrolyte film can protect the lithium metal, the lithium metal anode still requires dew point protection during subsequent battery assembly to prevent contamination of the electrolyte in the polymer electrolyte film by moisture and impurities in the air. This dew point protection undoubtedly increases production complexity and costs. Summary of the Invention

[0005] To address these challenges, the present invention provides a lithium metal-polymer composite anode, a lithium metal battery, and a method for preparing the same. This method forms a polymer skeleton on the surface of a lithium metal substrate, protecting the lithium metal. It also eliminates the need for dew point protection during battery assembly and can be performed in conventional production environments, significantly reducing production costs and process complexity.

[0006] To achieve the above object, the first aspect of the present invention provides a method for preparing a lithium metal-polymer composite negative electrode, comprising the steps of: (1) dissolving a polymerizable monomer in a solvent, and then mixing it with a cross-linking agent and an initiator to prepare a polymerizable monomer solution; (2) The polymerizable monomer solution is coated on the surface of the lithium metal substrate, and is cross-linked and cured by ultraviolet light to form a polymer skeleton on the surface of the lithium metal substrate.

[0007] In the method for preparing the lithium metal-polymer composite negative electrode of the present invention, a polymerizable monomer is pre-prepared into a polymerizable monomer solution, and polymerization is initiated by light on the surface of the lithium metal, which can simplify the production process and improve production efficiency. Introducing a crosslinking agent into the polymer backbone can enhance the mechanical strength of the polymer backbone, prevent the polymer backbone from cracking and peeling, and improve the long-term stability after assembly into a battery. The polymerizable monomer, crosslinking agent, and initiator are in situ cross-linked and cured on the surface of the lithium metal to form a polymer backbone. The polymer backbone not only acts as a protective film to effectively protect the lithium metal in an atmospheric environment, but also serves as a polymer matrix for a semi-solid electrolyte, which not only "locks" the liquid electrolyte but also improves the thermodynamic stability of the lithium metal. More importantly, the prepared polymer backbone does not contain an electrolyte that requires dew point protection. Therefore, the subsequent battery assembly can be carried out in a conventional production environment (such as an air environment), which can overcome the application bottleneck of lithium metal negative electrodes in air environments and significantly reduce production costs and process complexity.

[0008] As a technical solution of the present invention, the polymerizable monomer accounts for 5-30 wt.% of the mass of the solvent.

[0009] As a technical solution of the present invention, the polymerizable monomer is a condensation polymer, and the condensation polymer is selected from at least one of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride-fluoropolypropylene and polyethylene terephthalate.

[0010] As a technical solution of the present invention, the initiator accounts for 1-10 wt.% of the mass of the polymerizable monomer.

[0011] As a technical solution of the present invention, the initiator is a photoinitiator, and the photoinitiator is selected from one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, benzophenone and benzoin dimethyl ether.

[0012] As a technical solution of the present invention, the cross-linking agent accounts for 5-20 wt.% of the mass of the polymerizable monomer.

[0013] As a technical solution of the present invention, the cross-linking agent is selected from one or more of 1,3,6-hexanetrinitrile, trimethylolpropane trivinyl ether, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyethylene glycol methyl ether methacrylate, poly (ethylene glycol) methacrylate and polyethylene glycol dimethacrylate.

[0014] As a technical solution of the present invention, the solvent is selected from one or more of tetrahydrofuran, acetonitrile, acetone, dichloromethane, ethyl acetate, butyl acetate and 1,4-dioxane.

[0015] As a technical solution of the present invention, the wavelength of the ultraviolet light is 365 nm, and the irradiation time is 0.5 to 10.0 min.

[0016] A second aspect of the present invention provides a method for preparing a lithium metal-polymer composite negative electrode, comprising the steps of: (1) After mixing the polymerizable monomer and the cross-linking agent, an initiator is added and mixed to prepare a polymerizable monomer solution; (2) The polymerizable monomer solution is coated on the surface of the lithium metal substrate, and is cross-linked and solidified by heating to form a polymer skeleton on the surface of the lithium metal substrate.

[0017] In the method for preparing the lithium metal-polymer composite negative electrode of the present invention, a polymerizable monomer is pre-prepared into a polymerizable monomer solution, and polymerization is initiated by heat on the surface of the lithium metal, which can simplify the production process and improve production efficiency. Introducing a cross-linking agent into the polymer backbone can enhance the mechanical strength of the polymer backbone, prevent the polymer backbone from cracking and peeling, and improve the long-term stability after assembly into a battery. The polymerizable monomer, cross-linking agent, and initiator are in situ cross-linked and cured on the surface of the lithium metal to form a polymer backbone. The polymer backbone not only acts as a protective film to effectively protect the lithium metal in an atmospheric environment, but also serves as a polymer matrix for a semi-solid electrolyte, which can not only "lock" the liquid electrolyte but also improve the thermodynamic stability of the lithium metal. More importantly, the prepared polymer backbone does not contain an electrolyte that requires dew point protection. Therefore, the subsequent battery assembly can be carried out in a conventional production environment (such as an air environment), which can break through the application bottleneck of lithium metal negative electrodes in an air environment and significantly reduce production costs and process complexity.

[0018] As a technical solution of the present invention, the polymerizable monomer is selected from carbonate monomers, and the carbonate monomer is selected from one or more of vinylene carbonate, ethylene carbonate, and dimethyl carbonate.

[0019] As a technical solution of the present invention, the polymerizable monomer is selected from acrylate monomers, and the acrylate monomer is selected from one or more of methyl methacrylate, ethylene glycol dimethacrylate, tripropylene glycol diacrylate, triethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate.

[0020] As a technical solution of the present invention, the initiator accounts for 0.1-10.0 wt.% of the mass of the polymerizable monomer.

[0021] As a technical solution of the present invention, the initiator is a thermal initiator, and the thermal initiator is selected from one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

[0022] As a technical solution of the present invention, the cross-linking agent accounts for 5-20 wt.% of the mass of the polymerizable monomer.

[0023] As a technical solution of the present invention, the cross-linking agent is selected from one or more of 1,3,6-hexanetrinitrile, trimethylolpropane trivinyl ether, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyethylene glycol methyl ether methacrylate, poly (ethylene glycol) methacrylate and polyethylene glycol dimethacrylate.

[0024] As a technical solution of the present invention, the heating temperature is 50-100° C. and the heating time is 0.5-2.0 h.

[0025] A third aspect of the present invention provides a lithium metal-polymer composite anode comprising a lithium metal matrix and a polymer skeleton encapsulating the lithium metal matrix. This polymer skeleton not only protects the lithium metal but also, after the battery is assembled and filled, "locks" the liquid electrolyte, improving the interfacial properties between the lithium metal and the electrolyte and enhancing the thermodynamic stability of the lithium metal.

[0026] As a technical solution of the present invention, the lithium metal matrix is ​​selected from lithium metal sheets or lithium metal strips.

[0027] The fourth aspect of the present invention provides a lithium metal battery, comprising a positive electrode sheet, a separator, a negative electrode sheet and a liquid electrolyte, wherein the negative electrode sheet is a lithium metal-polymer composite negative electrode prepared by the aforementioned method for preparing a lithium metal-polymer composite negative electrode or the aforementioned lithium metal-polymer composite negative electrode.

[0028] As a technical solution of the present invention, the positive electrode sheet contains a positive electrode active material, and the positive electrode active material is selected from one of lithium iron phosphate materials, lithium nickel cobalt manganate materials, lithium nickel cobalt aluminum oxide materials, lithium cobalt oxide materials and lithium manganate materials.

[0029] As a technical solution of the present invention, the separator is selected from a polyethylene separator, a polypropylene separator, a polyimide separator, a cellulose separator, a glass fiber separator, a polyethylene terephthalate separator or a non-woven separator.

[0030] As a technical solution of the present invention, the liquid electrolyte includes a lithium salt and a non-aqueous organic solvent.

[0031] As a technical solution of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate, lithium difluorophosphate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium lower aliphatic carboxylate, lithium difluorobisoxalatophosphate, lithium bisfluorosulfonyl imide, lithium chloroborane and lithium tetraphenylborate, and the non-aqueous organic solvent is selected from ethylene carbonate, propylene carbonate, butylene carbonate, methyl amyl carbonate, dimethyl carbonate, diethyl carbonate At least one of esters, ethyl methyl carbonate, methylpropyl carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether and diethylene glycol dimethyl ether.

[0032] The fifth aspect of the present invention provides a method for preparing a lithium metal battery, comprising the steps of: in an air environment, using the lithium metal-polymer composite negative electrode prepared by the aforementioned method for preparing a lithium metal-polymer composite negative electrode or the aforementioned lithium metal-polymer composite negative electrode as a negative electrode sheet, assembling it with the diaphragm and the positive electrode sheet, injecting the liquid electrolyte, letting it stand, and forming.

[0033] In the lithium metal battery manufacturing method of the present invention, the polymer-coated negative and positive electrodes and the separator are assembled before the liquid electrolyte is injected. This assembly process is similar to that of conventional lithium secondary batteries, thus requiring no major process adjustments. Furthermore, the entire assembly process does not require dew point protection and can be performed in an air environment, significantly reducing production costs and process complexity. DETAILED DESCRIPTION

[0034] The present invention forms a polymer skeleton in situ on the surface of lithium metal through process improvement, which can not only protect the lithium metal but also avoid dew point protection during battery assembly, which is greatly beneficial to process promotion.

[0035] The lithium metal battery of the present invention comprises a positive electrode sheet, a separator, a negative electrode sheet and a liquid electrolyte.

[0036] The positive electrode sheet can be a conventional lithium secondary battery positive electrode sheet, i.e., it includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material is selected from one of lithium iron phosphate materials, lithium nickel cobalt manganate materials, lithium nickel cobalt aluminum oxide materials, lithium cobalt oxide materials, and lithium manganate materials. The lithium iron phosphate material can be lithium iron phosphate or a doped or coated modified lithium iron phosphate; the lithium nickel cobalt manganate material can be nickel cobalt manganese oxide or a doped or coated modified nickel cobalt manganese oxide; the lithium nickel cobalt aluminum oxide material can be nickel cobalt aluminum oxide or a doped or coated modified nickel cobalt aluminum oxide; the lithium cobalt oxide material can be lithium cobalt oxide or a doped or coated modified lithium cobalt oxide; and the lithium manganate material can be lithium manganate or a doped or coated modified lithium manganate. The conductive agent can be graphene, acetylene black, Super P, KS-6, etc. The binder can be polyvinylidene fluoride, polyvinyl alcohol, etc. The specific composition and preparation process of the positive electrode sheet can refer to the conventional positive electrode sheet preparation process and be adjusted according to actual conditions. It is not the focus of the present invention and will not be described in detail here.

[0037] The separator is selected from a polyethylene separator, a polypropylene separator, a polyimide separator, a cellulose separator, a glass fiber separator, a polyethylene terephthalate separator, or a non-woven separator. Of course, to improve the performance of the separator, a ceramic layer may be provided on the polyethylene separator, the polypropylene separator, the polyimide separator, the cellulose separator, the glass fiber separator, the polyethylene terephthalate separator, or the non-woven separator.

[0038] The liquid electrolyte comprises a lithium salt and a non-aqueous organic solvent. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate, lithium difluorophosphate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium lower aliphatic carboxylate, lithium difluorobisoxalatophosphate, lithium bisfluorosulfonyl imide, lithium chloroborane, and lithium tetraphenylborate. The non-aqueous organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, methyl amyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Conventional additives may also be added to the liquid electrolyte to improve the performance of the lithium metal battery.

[0039] The lithium metal battery manufacturing method of the present invention comprises the steps of assembling a negative electrode sheet, a separator, and a positive electrode sheet in an air environment, injecting a liquid electrolyte, allowing the battery to stand for formation. This manufacturing method can be performed in an air environment, does not require a strict process environment, and utilizes conventional negative electrode sheet, separator, and positive electrode sheet assembly steps and liquid electrolyte injection steps.

[0040] The negative electrode sheet of the lithium metal battery of the present invention can utilize a lithium metal-polymer composite negative electrode. The lithium metal-polymer composite negative electrode comprises a lithium metal substrate and a polymer skeleton encapsulating the lithium metal substrate. The lithium metal substrate is selected from a lithium metal sheet or a lithium metal ribbon. The polymer skeleton is formed by curing a polymerizable monomer with a crosslinking agent and an initiator by heating or ultraviolet light. The thickness of the polymer skeleton can be 20 to 100 μm. For example, but not limited to, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0041] The lithium metal-polymer composite negative electrode of the present invention can be prepared in a variety of ways. One preparation method may include the following steps: (1) dissolving a polymerizable monomer in a solvent, and then mixing it with a cross-linking agent and an initiator to prepare a polymerizable monomer solution; (2) The polymerizable monomer solution is coated on the surface of the lithium metal substrate, and is cross-linked and cured by ultraviolet light to form a polymer skeleton on the surface of the lithium metal substrate.

[0042] The polymerizable monomer accounts for 5 to 30 wt.% of the solvent. For example, the proportion of the polymerizable monomer may be, but is not limited to, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, or 30 wt.%. The solvent is selected from one or more of tetrahydrofuran, acetonitrile, acetone, dichloromethane, ethyl acetate, butyl acetate, and 1,4-dioxane. The polymerizable monomer is a condensation polymer selected from at least one of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride-fluoropolypropylene, and polyethylene terephthalate. The solvent may be removed by heating after crosslinking and curing to improve the purity of the polymer backbone.

[0043] Polyacrylonitrile (PAN) is used as the polymerizable monomer for UV-light cross-linking and curing. This is based on its high mechanical strength and rigidity, enabling it to form a dense and robust polymer film that effectively inhibits the growth of lithium dendrites. Furthermore, the cyano (-CN) functional groups in the molecular chain have strong polarity, enhancing the mechanical properties of the material through tight intermolecular forces. Furthermore, the cyano functional groups can weakly interact with lithium ions, promoting their transport and improving the ionic conductivity of the electrolyte. Furthermore, the linear structure and polar functional groups of polyacrylonitrile give it good solubility and dispersibility in solvents, facilitating the formation of a uniform polymerizable monomer solution that can rapidly polymerize to form a dense and uniform polymer skeleton membrane structure.

[0044] When polyethylene oxide is used as a polymerizable monomer, under the action of a crosslinker, polyethylene oxide forms a stable three-dimensional network structure, significantly improving mechanical strength, inhibiting lithium dendrite growth, and enhancing safety and cycle life. Simultaneously, thermal stability is also improved, preventing the locked electrolyte from softening at high temperatures after subsequent injection of a liquid electrolyte, thereby optimizing battery safety. By selecting and controlling the crosslinker content, the polyethylene oxide polymer backbone can maintain high ionic conductivity, thereby improving lithium ion transport, reducing interfacial impedance, and enhancing the cycle performance and coulombic efficiency of lithium metal batteries.

[0045] Polyvinylidene fluoride-fluoropolypropylene (PVDF-HFP), through its partially crystalline structure and fluorinated groups, combines moderate mechanical strength and flexibility, adapting to the volume changes of lithium metal and inhibiting dendrite growth. Its excellent chemical stability and wide electrochemical window effectively reduce interfacial side reactions. Its good solubility and film-forming properties facilitate processing. Furthermore, the crosslinking effect of a crosslinking agent forms a crosslinked network between polymer chains, enhancing the material's mechanical strength and flexibility, enabling it to demonstrate excellent performance in lithium metal anode protection. This crosslinked network effectively restricts molecular chain motion, reducing brittleness at low temperatures and fluidity at high temperatures, thereby improving film stability and heat resistance. Furthermore, crosslinking enhances ionic conductivity and facilitates lithium ion migration by providing more lithium ion transport pathways, thereby optimizing battery charge and discharge performance. Importantly, the crosslinked network structure helps improve interfacial interactions with the lithium metal surface, inhibiting lithium dendrite formation and reducing interfacial impedance, thereby enhancing the safety and cycle life of lithium metal batteries.

[0046] Polyethylene terephthalate (PET), as a polymerizable monomer, can improve the cycling performance and interfacial safety of lithium metal batteries to a certain extent due to its excellent electrochemical stability and mechanical properties. However, it still has some drawbacks. For example, PET's rigid structure makes it difficult to form a flexible polymer backbone, resulting in poor interfacial contact with the lithium metal anode and prone to voids and dendrite growth. Furthermore, PET's low ionic conductivity, high melting point, and poor solubility increase its processing difficulties. The present invention modifies PET with a crosslinker to significantly improve its processing and electrochemical properties. For example, the crosslinker 1,3,6-hexanetrinitrile is used to form a stable three-dimensional network structure between PET molecular chains. This not only enhances mechanical strength and thermal stability but also improves flexibility, allowing it to better adapt to volume changes of the lithium metal anode and reducing the risk of interfacial voids and dendrite growth. The free volume in the crosslinked structure provides channels for lithium ion transport, optimizing ionic conductivity. Furthermore, the crosslinked PET forms a denser and more uniform polymer film, reducing interfacial side reactions with the lithium metal anode and lowering interfacial impedance, thereby improving battery cycling performance and safety. In addition, cross-linking modification also reduces the crystallinity of PET, improves its solubility and processing properties, and facilitates large-scale production.

[0047] The initiator accounts for 1 to 10 wt.% of the mass of the polymerizable monomer. For example, the proportion of the initiator can be, but is not limited to, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, and 10 wt.%. The initiator is a photoinitiator selected from one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, benzophenone, and benzoin dimethyl ether.

[0048] The crosslinking agent accounts for 5 to 20 wt.% of the mass of the polymerizable monomer. For example, the proportion of the crosslinking agent may be, but is not limited to, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, and 20 wt.%. The crosslinking agent is selected from one or more of 1,3,6-hexanetrinitrile, trimethylolpropane trivinyl ether, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyethylene glycol methyl ether methacrylate, poly(ethylene glycol) methacrylate, and polyethylene glycol dimethacrylate. Preferably, the crosslinking agent is 1,3,6-hexanetrinitrile or trimethylolpropane trivinyl ether.

[0049] The wavelength of the ultraviolet light is 365 nm, and the irradiation time is 0.5~10.0 min. As an example, the irradiation time can be, but is not limited to, 0.5 min, 1.0 min, 1.5 min, 2.0 min, 2.5 min, 3.0 min, 3.5 min, 4.0 min, 4.5 min, 5.0 min, 5.5 min, 6.0 min, 6.5 min, 7.0 min, 7.5 min, 8.0 min, 8.5 min, 9.0 min, 9.5 min, and 10.0 min.

[0050] Another method for preparing the lithium metal-polymer composite negative electrode of the present invention may include the steps of: (1) After mixing the polymerizable monomer and the cross-linking agent, an initiator is added and mixed to prepare a polymerizable monomer solution; (2) The polymerizable monomer solution is coated on the surface of the lithium metal substrate, and is cross-linked and solidified on the surface of the lithium metal substrate by heating to form a polymer skeleton.

[0051] The polymerizable monomer is selected from a carbonate monomer or an acrylate monomer. The carbonate monomer is selected from one or more of vinylene carbonate, ethylene carbonate, and dimethyl carbonate. The acrylate monomer is selected from one or more of methyl methacrylate, ethylene glycol dimethacrylate, tripropylene glycol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate. Carbonate monomers or acrylate monomers can be readily thermally polymerized to obtain the corresponding polymer backbone.

[0052] Polyvinylene carbonate is prepared by thermal polymerization using vinylene carbonate as a polymerizable monomer as a polymer skeleton to protect lithium metal. If polyvinylene carbonate is used alone, it has several significant deficiencies in electrochemical performance, mainly in terms of ionic conductivity, mechanical strength, thermal stability and interfacial interaction. However, by introducing a cross-linking agent, a stable three-dimensional network structure can be formed between the polyvinylene carbonate molecular chains through cross-linking, which can significantly improve the mechanical strength and toughness of polyvinylene carbonate, thereby effectively improving its brittleness. During the cross-linking process, the cross-linking agent reacts with the active groups in the polyvinylene carbonate chain to form covalent bonds, which restricts the free movement of the molecular chain, helps to enhance the temperature resistance of the material, reduces the fluidity of the chain segments at high temperatures, and thus effectively prevents the breakage of the formed polymer skeleton. In addition, the formation of a three-dimensional network structure can improve the thermal stability of polyvinylene carbonate, making it less likely to decompose in a high-temperature environment, further improving the safety and reliability of the battery. The initiator accounts for 0.1 to 10.0 wt% of the mass of the polymerizable monomer. For example, the initiator may account for, but is not limited to, 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, 5.0 wt%, 6.0 wt%, 7.0 wt%, 8.0 wt%, 9.0 wt%, and 10.0 wt%. The initiator is a thermal initiator selected from one or more of azobisisobutyronitrile and azobisisoheptonitrile.

[0053] The cross-linking agent accounts for 5 to 20 wt.% of the mass of the polymerizable monomer. For example, the proportion of the cross-linking agent may be, but is not limited to, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, and 20 wt.%. The cross-linking agent is selected from one or more of 1,3,6-hexanetrinitrile, trimethylolpropane trivinyl ether, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyethylene glycol methyl ether methacrylate, poly(ethylene glycol) methacrylate, and polyethylene glycol dimethacrylate.

[0054] The heating temperature is 50-100° C., for example, the temperature may be, but is not limited to, 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., and 100° C. The heating time is 0.5-2.0 h, for example, the heating time may be, but is not limited to, 0.5 h, 1.0 h, 1.5 h, and 2.0 h.

[0055] In order to better illustrate the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0056] Example 1 This embodiment is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0057] (1) Weigh 0.75 g of polyacrylonitrile and dissolve it in 15 mL of tetrahydrofuran and stir for 2 h to obtain a uniform mixed solution. Add 0.037 g of 1,3,6-hexanetrinitrile and 0.0075 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0058] (2) A polymerizable monomer solution was coated on the surface of a lithium metal strip and irradiated with ultraviolet light at a wavelength of 365 nm for 3.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The tetrahydrofuran was removed by heating at 70°C for 10 min to obtain a lithium metal-polymer composite negative electrode.

[0059] Example 2 This embodiment is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0060] (1) Weigh 0.75 g of polyethylene oxide and dissolve it in 20 ml of acetonitrile and stir for 3 h to obtain a uniform mixed solution. Add 0.075 g of trimethylolpropane trivinyl ether and 0.0095 g of 1-hydroxy-cyclohexyl-phenyl ketone to the uniform mixed solution and stir at room temperature for 2.0 h to obtain a polymerizable monomer solution.

[0061] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 5.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The acetonitrile was removed by heating at 85°C for 15 min to obtain a lithium metal-polymer composite negative electrode.

[0062] Example 3 This embodiment is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0063] (1) Weigh 0.85 g of polyvinylidene fluoride-fluoropolypropylene and dissolve it in 15 mL of dichloromethane and stir for 2 h to obtain a uniform mixed solution. Add 0.075 g of pentaerythritol tetraacrylate and 0.05 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0064] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 4.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The dichloromethane was removed by heating at 45°C for 5 min to obtain a lithium metal-polymer composite negative electrode.

[0065] Example 4 This embodiment is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0066] (1) Weigh 0.70 g of polyethylene terephthalate and dissolve it in 15 mL of acetone. Stir for 2 h to obtain a uniform mixed solution. Add 0.057 g of ethoxylated trimethylolpropane triacrylate and 0.0075 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution and stir at room temperature for 2.5 h to obtain a polymerizable monomer solution.

[0067] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 4.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The acetone was removed by heating at 60°C for 10 min to obtain a lithium metal-polymer composite negative electrode.

[0068] Example 5 This embodiment is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0069] (1) Weigh 1.0 g of vinylene carbonate and 0.1 g of pentaerythritol tetraacrylate and stir for 30 min to obtain a uniform mixed solution. Add 0.003 g of azobisisobutyronitrile to the uniform mixed solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0070] (2) The polymerizable monomer solution is coated on the surface of the lithium metal strip and heated at 50°C for 30 minutes to obtain a polymer skeleton with a thickness of 50±3 μm, thereby obtaining a lithium metal-polymer composite negative electrode.

[0071] Example 6 This embodiment is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0072] (1) Weigh 1 g of tripropylene glycol diacrylate and 0.1 g of polyethylene glycol methyl ether acrylate and stir for 5 min to obtain a uniform mixed solution. Add 0.003 g of azobisisobutyronitrile to the uniform mixed solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0073] (2) The polymerizable monomer solution is coated on the surface of the lithium metal strip and heated at 65°C for 30 minutes to obtain a polymer skeleton with a thickness of 50±3 μm, thereby obtaining a lithium metal-polymer composite negative electrode.

[0074] Comparative Example 1 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0075] (1) Weigh 0.70 g of polyacrylonitrile and dissolve it in 15 mL of tetrahydrofuran and stir for 2 h to obtain a uniform mixed solution. Add 0.0075 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0076] (2) A polymerizable monomer solution was coated on the surface of a lithium metal strip and irradiated with ultraviolet light at a wavelength of 365 nm for 3.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The tetrahydrofuran was removed by heating at 70°C for 10 min to obtain a lithium metal-polymer composite negative electrode.

[0077] Comparative Example 2 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0078] (1) Weigh 0.75 g of polyethylene oxide and dissolve it in 20 ml of acetonitrile and stir for 3 h to obtain a uniform mixed solution. Add 0.0095 g of 1-hydroxy-cyclohexyl-phenyl ketone to the uniform mixed solution and stir at room temperature for 2.0 h to obtain a polymerizable monomer solution.

[0079] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 5.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The acetonitrile was removed by heating at 85°C for 15 min to obtain a lithium metal-polymer composite negative electrode.

[0080] Comparative Example 3 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0081] (1) Weigh 0.85 g of polyvinylidene fluoride-fluoropolypropylene and dissolve it in 15 mL of dichloromethane and stir for 2 h to obtain a uniform mixed solution. Add 0.05 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0082] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 4.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The dichloromethane was removed by heating at 45°C for 5 min to obtain a lithium metal-polymer composite negative electrode.

[0083] Comparative Example 4 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0084] (1) Weigh 0.70 g of polyethylene terephthalate and dissolve it in 15 mL of acetone and stir for 2 h to obtain a uniform mixed solution. Add 0.0075 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution and stir at room temperature for 2.5 h to obtain a polymerizable monomer solution.

[0085] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 4.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The acetone was removed by heating at 60°C for 10 min to obtain a lithium metal-polymer composite negative electrode.

[0086] Comparative Example 5 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0087] (1) Weigh 1.0 g of vinylene carbonate and dissolve it in a 20 mL sample bottle. Add 0.003 g of azobisisobutyronitrile to the above solution and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0088] (2) The polymerizable monomer solution is coated on the surface of the lithium metal strip and heated at 50°C for 30 minutes to obtain a polymer skeleton with a thickness of 50±3 μm, thereby obtaining a lithium metal-polymer composite negative electrode.

[0089] Comparative Example 6 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0090] (1) Weigh 1 g of tripropylene glycol diacrylate and 0.003 g of azobisisobutyronitrile and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0091] (2) The polymerizable monomer solution is coated on the surface of the lithium metal strip and heated at 65°C for 30 minutes to obtain a polymer skeleton with a thickness of 50±3 μm, thereby obtaining a lithium metal-polymer composite negative electrode.

[0092] Comparative Example 7 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0093] (1) Weigh 0.70 g of polyacrylonitrile and dissolve it in 15 mL of tetrahydrofuran and stir for 2 h to obtain a uniform mixed solution. Add 0.0075 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution, and then add 60 μL of liquid electrolyte (14 g of LiPF6 + 86 g of a mixed solvent, wherein the mixed solvent is ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7) and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0094] (2) A polymerizable monomer solution was coated on the surface of a lithium metal strip and irradiated with ultraviolet light at a wavelength of 365 nm for 3.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The tetrahydrofuran was removed by heating at 70°C for 10 min to obtain a lithium metal-polymer composite negative electrode.

[0095] Comparative Example 8 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0096] (1) Weigh 0.75 g of polyethylene oxide and dissolve it in 20 ml of acetonitrile. Stir for 3 h to obtain a uniform mixed solution. Add 0.0095 g of 1-hydroxy-cyclohexyl-phenyl ketone to the uniform mixed solution. Then add 60 μL of liquid electrolyte (14 g of LiPF6 + 86 g of a mixed solvent consisting of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7) and stir at room temperature for 2.0 h to obtain a polymerizable monomer solution.

[0097] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 5.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The acetonitrile was removed by heating at 85°C for 15 min to obtain a lithium metal-polymer composite negative electrode.

[0098] Comparative Example 9 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0099] (1) Weigh 0.85 g of polyvinylidene fluoride-fluoropolypropylene and dissolve it in 15 mL of dichloromethane and stir for 2 h to obtain a uniform mixed solution. Add 0.05 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution, and then add 60 μL of liquid electrolyte (14 g of LiPF6 + 86 g of mixed solvent, the mixed solvent is ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7) and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0100] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 4.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The dichloromethane was removed by heating at 45°C for 5 min to obtain a lithium metal-polymer composite negative electrode.

[0101] Comparative Example 10 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0102] (1) Weigh 0.70 g of polyethylene terephthalate (PET) and dissolve it in 15 mL of acetone, stirring for 2 h to obtain a uniform mixed solution. Add 0.0075 g of 2-hydroxy-2-methyl-1-phenyl-1-propanone to the uniform mixed solution, and then add 60 μL of liquid electrolyte (14 g of LiPF6 + 86 g of a mixed solvent, wherein the mixed solvent is ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7) and stir at room temperature for 2.5 h to obtain a polymerizable monomer solution.

[0103] (2) The polymerizable monomer solution was coated on the surface of the lithium metal strip and irradiated with ultraviolet light of wavelength 365 nm for 4.0 min to obtain a polymer skeleton with a thickness of 50±3 μm. The acetone was removed by heating at 60°C for 10 min to obtain a lithium metal-polymer composite negative electrode.

[0104] Comparative Example 11 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0105] (1) Weigh 1.0 g of vinylene carbonate and dissolve it in a 20 mL sample bottle. Take 0.003 g of azobisisobutyronitrile and add it to the above solution. Then add 60 μL of liquid electrolyte (14 g LiPF6 + 86 g mixed solvent, the mixed solvent is vinylene carbonate and ethyl methyl carbonate with a volume ratio of 3:7) and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0106] (2) The polymerizable monomer solution is coated on the surface of the lithium metal strip and heated at 50°C for 30 minutes to obtain a polymer skeleton with a thickness of 50±3 μm, thereby obtaining a lithium metal-polymer composite negative electrode.

[0107] Comparative Example 12 This comparative example is a method for preparing a lithium metal-polymer composite negative electrode, which includes the following steps.

[0108] (1) Weigh 1 g of tripropylene glycol diacrylate and 0.003 g of azobisisobutyronitrile, mix them, add 60 μL of liquid electrolyte (14 g of LiPF6 + 86 g of mixed solvent, the mixed solvent is ethylene carbonate and ethyl methyl carbonate with a volume ratio of 3:7), and stir at room temperature for 1.5 h to obtain a polymerizable monomer solution.

[0109] (2) The polymerizable monomer solution is coated on the surface of the lithium metal strip and heated at 65°C for 30 minutes to obtain a polymer skeleton with a thickness of 50±3 μm, thereby obtaining a lithium metal-polymer composite negative electrode.

[0110] In an air environment, batteries were assembled using the lithium metal-polymer composite negative electrodes prepared in Examples 1-6 and Comparative Examples 1-6 as the negative electrode sheet, a LiCoO2 positive electrode sheet, and a polypropylene separator. 60 μL of liquid electrolyte (14 g LiPF6 + 86 g mixed solvent, consisting of ethylene carbonate and ethyl methyl carbonate in a 3:7 volume ratio) was injected. After room temperature stabilization, chemical formation, and high-temperature stabilization, lithium metal batteries #1-12 were obtained.

[0111] In an environment with O₂ <0.01 ppm and H₂O <0.01 ppm, the lithium metal-polymer composite negative electrode prepared in Comparative Examples 7-12 was used as the negative electrode, and then assembled with a LiCoO₂ positive electrode and a polypropylene separator to form a battery. After room temperature stabilization, formation, and high-temperature stabilization, lithium metal batteries #13-18 were obtained.

[0112] The lithium metal batteries 1~18# were charged and discharged cyclically at a current density of 0.5mA / cm 2 , charge for one hour and then discharge for one hour, record the number of cycles and polarization voltage, the results are shown in Table 1.

[0113] Table 1 Charge and discharge test data of lithium metal batteries 1~18#

[0114] Comparing the results of lithium metal batteries 1 to 6# and lithium metal batteries 7 to 12# in Table 1, it can be seen that the lithium metal-polymer composite negative electrode prepared by adding a cross-linking agent can make the lithium metal battery have better cycle performance. This is because the introduction of the cross-linking agent into the polymer skeleton can enhance the mechanical strength of the polymer skeleton and prevent the polymer skeleton from breaking and peeling, thereby improving the long-term stability after assembly into a battery.

[0115] Comparing the results of lithium metal batteries #1-6 and #13-18 in Table 1, it can be seen that the lithium metal battery that first prepares the anode sheet with a polymer skeleton and then assembles it before injecting the liquid electrolyte has the same better cycle performance as the lithium metal battery that first prepares the anode sheet with a polymer electrolyte and then assembles it. A comparison of the two preparation processes shows that the former can be assembled in an air environment, while the latter requires controlling the humidity and oxygen in the assembly environment to prevent the electrolyte LiPF6 from being contaminated by moisture and impurities in the air. Therefore, the assembly process of lithium metal batteries #1-6 is simpler and can break through the application bottleneck of lithium metal anodes in air environments.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a lithium metal-polymer composite negative electrode, characterized in that: Including steps: (1) dissolving a polymerizable monomer in a solvent, and then mixing it with a cross-linking agent and an initiator to prepare a polymerizable monomer solution; (2) The polymerizable monomer solution is coated on the surface of the lithium metal substrate, and is cross-linked and cured by ultraviolet light to form a polymer skeleton on the surface of the lithium metal substrate.

2. The method for preparing a lithium metal-polymer composite negative electrode according to claim 1, wherein: Includes at least one of the following features (1) to (8): (1) The polymerizable monomer accounts for 5 to 30 wt.% of the solvent; (2) The polymerizable monomer is a condensation polymer, and the condensation polymer is selected from at least one of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride-fluoropolypropylene and polyethylene terephthalate; (3) The initiator accounts for 1-10 wt.% of the mass of the polymerizable monomer; (4) The initiator is a photoinitiator, and the photoinitiator is selected from one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, benzophenone and benzoin dimethyl ether; (5) The cross-linking agent accounts for 5-20 wt.% of the mass of the polymerizable monomer; (6) The crosslinking agent is selected from one or more of 1,3,6-hexanetrinitrile, trimethylolpropane trivinyl ether, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyethylene glycol methyl ether methacrylate, poly(ethylene glycol) methacrylate, and polyethylene glycol dimethacrylate; (7) The solvent is selected from one or more of tetrahydrofuran, acetonitrile, acetone, dichloromethane, ethyl acetate, butyl acetate and 1,4-dioxane; (8) The wavelength of the ultraviolet light is 365 nm, and the irradiation time is 0.5 to 10.0 min.

3. A method for preparing a lithium metal-polymer composite negative electrode, characterized in that: Including steps: (1) After mixing the polymerizable monomer and the cross-linking agent, an initiator is added and mixed to prepare a polymerizable monomer solution; (2) The polymerizable monomer solution is coated on the surface of the lithium metal substrate, and is cross-linked and solidified by heating to form a polymer skeleton on the surface of the lithium metal substrate.

4. The method for preparing a lithium metal-polymer composite negative electrode according to claim 3, wherein: The invention comprises at least one of the following features (I) to (VII): (I) the polymerizable monomer is selected from carbonate monomers, and the carbonate monomer is selected from one or more of vinylene carbonate, ethylene carbonate, and dimethyl carbonate; (II) the polymerizable monomer is selected from acrylate monomers, and the acrylate monomer is selected from one or more of methyl methacrylate, ethylene glycol dimethacrylate, tripropylene glycol diacrylate, triethylene glycol dimethacrylate and tetraethylene glycol dimethacrylate; (III) the initiator accounts for 0.1-10.0 wt.% of the mass of the polymerizable monomer; (IV) the initiator is a thermal initiator, and the thermal initiator is selected from one or more of azobisisobutyronitrile and azobisisoheptanenitrile; (V) the cross-linking agent accounts for 5-20 wt.% of the mass of the polymerizable monomer; (VI) the crosslinking agent is selected from one or more of 1,3,6-hexanetrinitrile, trimethylolpropane trivinyl ether, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyethylene glycol methyl ether methacrylate, poly(ethylene glycol) methacrylate, and polyethylene glycol dimethacrylate; (VII) The heating temperature is 50-100° C. and the heating time is 0.5-2.0 h.

5. The lithium metal-polymer composite negative electrode prepared by the method for preparing a lithium metal-polymer composite negative electrode according to any one of claims 1 to 4, characterized in that: The invention comprises a lithium metal matrix and a polymer skeleton wrapping the lithium metal matrix.

6. The lithium metal-polymer composite negative electrode according to claim 5, characterized in that The lithium metal matrix is ​​selected from lithium metal sheets or lithium metal strips.

7. A lithium metal battery, characterized in that: The invention comprises a positive electrode sheet, a separator, a negative electrode sheet and a liquid electrolyte, wherein the negative electrode sheet is a lithium metal-polymer composite negative electrode prepared by the preparation method of the lithium metal-polymer composite negative electrode according to any one of claims 1 to 4 or a lithium metal-polymer composite negative electrode according to any one of claims 5 to 6.

8. The lithium metal battery according to claim 7, characterized in that The invention comprises at least one of the following features (i) to (iii): (i) the positive electrode sheet comprises a positive electrode active material, wherein the positive electrode active material is selected from one of lithium iron phosphate materials, lithium nickel cobalt manganate materials, lithium nickel cobalt aluminum oxide materials, lithium cobalt oxide materials, and lithium manganate materials; (ii) the separator is selected from a polyethylene separator, a polypropylene separator, a polyimide separator, a cellulose separator, a glass fiber separator, a polyethylene terephthalate separator or a non-woven separator; (iii) The liquid electrolyte comprises a lithium salt and a non-aqueous organic solvent.

9. The lithium metal battery according to claim 8, characterized in that The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate, lithium difluorophosphate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium lower aliphatic carboxylate, lithium difluorobisoxalatophosphate, lithium bisfluorosulfonyl imide, lithium chloroborane and lithium tetraphenylborate, and the non-aqueous organic solvent is selected from ethylene carbonate, propylene carbonate, butylene carbonate, methyl amyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate At least one of esters, methylpropyl carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether and diethylene glycol dimethyl ether.

10. The method for preparing a lithium metal battery according to any one of claims 7 to 9, wherein: The method comprises the following steps: in an air environment, using a lithium metal-polymer composite negative electrode prepared by the preparation method of a lithium metal-polymer composite negative electrode according to any one of claims 1 to 4 or a lithium metal-polymer composite negative electrode according to any one of claims 5 to 6 as a negative electrode sheet, assembling the negative electrode sheet with the separator and the positive electrode sheet, injecting the liquid electrolyte, allowing the negative electrode to stand, and forming the negative electrode.

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