Metal organic framework precursor, solid-state lithium metal battery negative electrode and preparation method of solid-state lithium metal battery negative electrode

Abstract

The invention provides a metal organic framework precursor, a solid-state lithium metal battery negative electrode and a preparation method of the solid-state lithium metal battery negative electrode, and provides an optimized preparation process aiming at the problems of large lithium ion transmission resistance, unstable interface, lithium dendrite generation and the like in the prior art, so that the cycling stability and the energy density of a solid-state lithium metal battery are improved. Due to the introduction of ferrocene and zirconium-cobalt bimetal combination, the metal organic framework precursor can effectively improve the energy density and cycling stability of the battery when being used as a lithium metal battery negative electrode coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium metal batteries, and particularly relates to a metal-organic framework precursor, a negative electrode of a solid-state lithium metal battery, and a preparation method thereof. Background Art

[0002] Traditional lithium-ion batteries usually use liquid electrolytes, which expose some key bottlenecks today with the increasing demand for high energy density, mainly reflected in terms of safety and energy density.

[0003] To overcome the disadvantages of traditional lithium-ion batteries, solid-state lithium batteries, as the next-generation high-energy-density energy storage technology, have gradually become a research hotspot. Solid-state lithium batteries use solid electrolytes to replace traditional liquid electrolytes and use lithium metal negative electrodes to improve energy density, with the following significant advantages: higher energy density, improved safety, and longer cycle life.

[0004] The patent application with the publication number CN108336417A discloses a manufacturing method of an all-solid-state lithium-ion battery using a thermosetting resin-coated laminated battery. Even when charging and discharging the all-solid-state lithium-ion battery after being coated with the thermosetting resin, the rupture of the thermosetting resin can be suppressed. The manufacturing method of the all-solid-state lithium-ion battery includes: a first step of laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer to form a laminated battery having both end faces and side faces in the lamination direction; a second step of charging the laminated battery to a charging rate of 100% or more and 112% or less; a third step of covering at least the side faces of the charged laminated battery with an uncured thermosetting resin; and a fourth step of heating the thermosetting resin to cure it.

[0005] The patent application with the publication number CN114883641A discloses a preparation method of an LATP-based solid electrolyte interface layer and an LATP-based solid-state lithium battery. A preparation method of an LATP-based solid electrolyte interface layer includes: drying a commercial boron nitride release agent slurry into powder, placing it around an LATP cold-pressed tablet, and performing high-temperature sintering to coat the powder on the surface of the LATP cold-pressed tablet to form the interface layer; processing an interface layer on the LATP solid electrolyte, and after processing a lithium metal negative electrode on the side of the solid electrolyte containing the interface layer, assembling it with a positive electrode to form a solid-state lithium battery.

[0006] Although solid-state lithium batteries have great potential, they still face many challenges in practical applications, especially in the preparation of negative electrodes: Large lithium ion transport resistance: Solid electrolytes usually have lower ionic conductivity than liquid electrolytes. Especially at the interface between the lithium metal anode and the solid electrolyte, a high-impedance interface is easily formed, hindering the effective transport of lithium ions. This problem directly affects the rate performance and energy density of the battery.

[0007] Unstable interface: The interface between lithium metal and solid electrolyte often easily forms an unstable interfacial layer. This layer is usually generated by electrochemical reactions and will cause an increase in interfacial resistance during cycling, thereby affecting the cycle life and safety of the battery.

[0008] Lithium dendrite problem: Although solid electrolytes can inhibit the growth of lithium dendrites to a certain extent, due to the volume change of lithium metal and interfacial inhomogeneity, lithium dendrites may still grow inside the solid electrolyte, thus triggering a short-circuit risk. Summary of the Invention

[0009] To solve the above technical problems existing in the prior art, the present invention provides a metal-organic framework precursor, a solid-state lithium metal battery anode, and a preparation method thereof. Aiming at the problems of large lithium ion transport resistance, unstable interface, and lithium dendrite formation in the prior art, an optimized preparation process is provided to improve the cycle stability and energy density of solid-state lithium metal batteries.

[0010] The present invention provides a metal-organic framework precursor for the coating of a solid-state lithium metal battery anode. The preparation method of the metal-organic framework precursor includes the following steps: S1. Mix and react a zirconium source, a cobalt source, and 2,2'-bipyridine-5,5'-dicarbonyl chloride in a first solvent. The zirconium ions in the zirconium source and the cobalt ions in the cobalt source coordinate with the nitrogen and oxygen atoms in 2,2'-bipyridine-5,5'-dicarbonyl chloride to form a zirconium-cobalt / 2,2'-bipyridine-5,5'-dicarbonyl chloride complex; S2. Perform an esterification reaction on the zirconium-cobalt / 2,2'-bipyridine-5,5'-dicarbonyl chloride complex and ferrocenyl ethanol to obtain the metal-organic framework precursor.

[0011] Preferably, the zirconium source is zirconium chloride, zirconyl chloride, zirconium sulfate, or zirconium acetate, and the cobalt source is cobalt chloride, cobalt nitrate, cobalt sulfate, or cobalt acetate. These zirconium sources and cobalt sources respectively provide zirconium ions and cobalt ions to participate in the reaction to form a MOF complex precipitate, while the anions in the zirconium source and cobalt source do not participate in the reaction and will be removed finally. The first solvent is at least one of dichloroethane, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, benzene, and toluene.

[0012] Preferably, in step S1, the mass ratio of each raw material is zirconium source∶cobalt source∶2,2'-bipyridine-5,5'-dicarbonyl chloride∶solvent = 10-20∶0.05-0.4∶28-54∶200-300.

[0013] Further preferably, in step S1, the mass ratio of each raw material is zirconium source∶cobalt source∶2,2-bipyridine-5,5-dicarbonyl chloride∶solvent = 15-20∶0.2-0.4∶42-54∶250-300, and the energy density and cycle life of the lithium metal battery prepared are better.

[0014] Preferably, in step S2, the mass ratio of ferrocenyl ethanol to 2,2-bipyridine-5,5-dicarbonyl chloride in step S1 is 0.05-0.4∶28-54.

[0015] Further preferably, in step S2, the mass ratio of ferrocenyl ethanol to 2,2-bipyridine-5,5-dicarbonyl chloride in step S1 is 0.2-0.4∶42-54, and the energy density and cycle life of the lithium metal battery prepared are better.

[0016] Preferably, in step S2, the catalyst for the esterification reaction is triethylamine; the mass ratio of the triethylamine to ferrocenyl ethanol is 0.5-2.4∶0.05-0.4.

[0017] Further preferably, the mass ratio of the triethylamine to ferrocenyl ethanol is 1.5-2.4∶0.2-0.4, and the energy density and cycle life of the lithium metal battery prepared are better.

[0018] Preferably, in step S1, the reaction temperature is 45-55°C, and the reaction time is 30-60 minutes.

[0019] Preferably, in step S2, the reaction temperature of the esterification reaction is 80-105°C, and the reaction time is 16-20 hours.

[0020] The present invention provides a method for preparing a negative electrode of a solid-state lithium metal battery, comprising the following steps: (1) Electrochemically deposit lithium metal on both sides of a copper foil current collector to form a lithium metal layer on each side; (2) Polymerize a polymer monomer under an initiator to obtain a polymer solution A; Dissolve the above metal-organic framework precursor in a second solvent to obtain a solution B; Mix the solution A, the solution B and a lithium salt uniformly to obtain a coating slurry; (3) Uniformly coat the coating slurry obtained in step (2) on the surface of the lithium metal layer obtained in step (1), and remove the second solvent to make the coating slurry form an interface layer, thus obtaining the negative electrode of the solid-state lithium metal battery.

[0021] Preferably, in step (2), the concentration of the solution B is 0.5-1.0 mol / L.

[0022] Preferably, in step (2), the mass ratio of solution A, solution B and the lithium salt during mixing is 1:8:1.

[0023] Preferably, the polymer monomer is at least one of methyl methacrylate, polyethylene glycol methacrylate, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate and polyvinylidene fluoride.

[0024] Preferably, the initiator is azobisisobutyronitrile.

[0025] Preferably, the mass ratio of the polymer monomer to the initiator is 100:1.

[0026] Preferably, the lithium salt is at least one of LiClO4, LiPF6, LiBF4, LiFSI and LiTFSI.

[0027] Preferably, the second solvent is ethanol or methanol.

[0028] Preferably, in step (1), the purity of the lithium metal is not less than 99.9%.

[0029] Preferably, in step (1), the current density of the electrochemical deposition is 1-5 mA / cm 2 , and the deposition temperature is 25-35 °C.

[0030] Preferably, in step (3), the second solvent is removed by a heat treatment method, and the heat treatment temperature is 95-110 °C.

[0031] The present invention also provides a negative electrode for a solid-state lithium metal battery, and the negative electrode for a solid-state lithium metal battery is prepared by the preparation method of the negative electrode for a solid-state lithium metal battery described above.

[0032] Compared with the prior art, the present invention has the following beneficial effects: (1) Improve the electrochemical performance: Due to the introduction of ferrocene and zirconium-cobalt bimetallic combination, the metal-organic framework precursor of this MOF material in the present invention can effectively improve the energy density and cycle stability of the battery when used as a coating for the negative electrode of a lithium metal battery. Ferrocene can promote electron transfer, and the presence of zirconium and cobalt optimizes the adsorption and release process of lithium ions, thereby improving the electrochemical performance.

[0033] (2) Enhance the mechanical stability: The metal-organic framework precursor has excellent mechanical stability due to its highly cross-linked structure. When used as a battery electrode material, this stability can effectively inhibit the growth of lithium dendrites and avoid short-circuit problems caused by dendrite penetration through the separator.

[0034] (3) Optimize interfacial compatibility: The porous nature of the metal-organic framework precursor enables the electrolyte to penetrate better into the electrode material, increasing the solid-liquid contact area and optimizing the interfacial compatibility. This is crucial for reducing the interfacial resistance during charge and discharge of the battery and improving its charge and discharge efficiency.

[0035] (4) Provide long-term stability: Metal ions supported and protected by the organic framework can ensure stability during the long-term use of the battery, extending the battery's service life, especially in complex battery operating environments. Brief Description of the Drawings

[0036] Figure 1 It is a cycle curve graph obtained by performing cycle life tests on Examples 1-5 and Comparative Examples 1-3. Detailed Implementation Modes

[0037] Example 1 A preparation method for the negative electrode of a high-energy density solid-state lithium metal battery, and its operating steps are as follows: a) Preparation of the lithium metal negative electrode: Deposit high-purity lithium metal on both sides of a copper foil current collector with a thickness of 10 microns by electrochemical deposition, and form a uniform lithium metal layer with a thickness of 8 microns on each side; b) Construct a solid electrolyte interface layer: First, stir the reaction monomer and initiator at 60 °C for 8 h to obtain a polymer viscous solution A. Then, prepare an iron-zirconium-cobalt metal-organic framework precursor solution B. Then, add solution B to solution A and add a lithium salt, and stir at room temperature for 24 h to obtain a polymer-iron-zirconium-cobalt metal-organic framework solution. Coat it evenly on both sides of the lithium metal negative electrode, and perform heat treatment for 1 hour after coating. The thickness of a single interface layer is controlled at 10 microns; c) Assembly and encapsulation of the negative electrode: In an argon atmosphere, stack and assemble the prepared lithium metal negative electrode with a separator and an NCM ternary positive electrode, and encapsulate the assembled battery core under vacuum.

[0038] In step a), the purity of the high-purity lithium metal is not less than 99.9%.

[0039] In step a), the current density of the electrochemical deposition is controlled at 1 mA / cm 2 , and the deposition temperature is 25 °C.

[0040] In step b), the reaction monomer is polyethylene glycol methacrylate (PEGMMA), and the dosage is 10 g; the initiator is azobisisobutyronitrile, and the dosage is 0.1 g.

[0041] In step b), the lithium salt is LiFSI.

[0042] In step b), the concentration of the iron-zirconium-cobalt metal-organic framework precursor solution is 0.5 mol / L.

[0043] In step b), the preparation method of the iron-zirconium-cobalt metal-organic framework precursor solution is as follows: S1. Mix 10 g of zirconium chloride (ZrCl4), 0.05 g of cobalt chloride (CoCl2), and 28 g of 2,2-bipyridine-5,5-dicarbonyl chloride with 200 g of dichloroethane as the solvent, carry out the reaction, control the reaction temperature at 45 °C, the pressure is the autogenous pressure, and the reaction time is 30 minutes; S2. Then add 0.05 g of ferrocenylethanol and 0.5 g of triethylamine, react at 80 °C for 16 hours, separate and purify after the reaction is completed to obtain the iron-zirconium-cobalt metal-organic framework precursor, and dissolve it in anhydrous ethanol to obtain the iron-zirconium-cobalt metal-organic framework precursor solution.

[0044] In step b), the mixed solution is mixed in a mass ratio of solution A∶solution B∶lithium salt = 1∶8∶1.

[0045] In step b), the heat treatment temperature is 95 °C.

[0046] In step c), the requirement for the argon atmosphere is that the water content is less than 10 ppm and the oxygen content is less than 1 ppm.

[0047] In step c), the encapsulation pressure is controlled at 60 Pa.

[0048] Example 2

[0049] A preparation method for the negative electrode of a high-energy density solid-state lithium metal battery, and its operation steps are as follows: a) Preparation of the lithium metal negative electrode: Deposit high-purity lithium metal on both sides of a copper foil current collector with a thickness of 20 μm by electrochemical deposition, and form a uniform lithium metal layer with a thickness of 9 μm on each side; b) Construction of the solid electrolyte interface layer: First, stir the reaction monomer and the initiator at 60 °C for 8 h to obtain a polymer viscous solution A, then prepare an iron-zirconium-cobalt metal-organic framework precursor solution B, then add solution B to solution A and add a lithium salt and stir at room temperature for 24 h to obtain a polymer-iron-zirconium-cobalt metal-organic framework solution, and uniformly coat it on both sides of the lithium metal negative electrode. After coating, perform heat treatment for 1.5 hours, and control the thickness of a single interface layer at 12.5 μm; c) Assembly and encapsulation of the negative electrode: In an argon atmosphere, stack and assemble the prepared lithium metal negative electrode, the separator, and the NCM ternary positive electrode, and encapsulate the assembled battery core under vacuum.

[0050] In step a), the purity of the high-purity lithium metal is not less than 99.9%.

[0051] In step a), the electrochemically deposited current density is controlled at 2.5 mA / cm 2 , and the deposition temperature is 30 °C.

[0052] In step b), the reaction monomer is polyethylene glycol methacrylate (PEGMMA) with a dosage of 10 g; the initiator is azobisisobutyronitrile with a dosage of 0.1 g.

[0053] In step b), the lithium salt is LiFSI.

[0054] In step b), the concentration of the iron-zirconium-cobalt metal-organic framework precursor solution is 0.75 mol / L.

[0055] In step b), the preparation method of the iron-zirconium-cobalt metal-organic framework precursor solution is as follows: S1. Mix 15 g of zirconium chloride (ZrCl4), 0.2 g of cobalt chloride (CoCl2), and 42 g of 2,2-bipyridine-5,5-dicarbonyl chloride; react in 250 g of dichloroethane, control the reaction temperature at 50 °C, the pressure is the self-generated pressure, and the reaction time is 45 minutes; S2. Then add 0.2 g of ferrocenylethanol and 1.5 g of triethylamine, react at 95 °C for 18 hours, separate and purify after the reaction is completed to obtain the iron-zirconium-cobalt metal-organic framework precursor, and dissolve it in anhydrous ethanol to obtain the iron-zirconium-cobalt metal-organic framework precursor solution.

[0056] In step b), the mixed solution is mixed according to the mass ratio of solution A∶solution B∶lithium salt = 1∶8∶1.

[0057] In step b), the heat treatment temperature is 105 °C.

[0058] In step c), the requirement for the argon atmosphere is that the moisture content is lower than 10 ppm and the oxygen content is lower than 1 ppm.

[0059] In step c), the encapsulation pressure is controlled at 70 Pa.

[0060] Example 3

[0061] A preparation method for the negative electrode of a high-energy density solid-state lithium metal battery, and its operation steps are as follows: a) Preparation of the lithium metal negative electrode: Deposit high-purity lithium metal on both sides of a copper foil current collector with a thickness of 30 μm by electrochemical deposition, and form a uniform lithium metal layer with a thickness of 10 μm on each side; b) Construction of the solid electrolyte interface layer: First, stir the reaction monomers and initiator at 60 °C for 8 h to obtain a viscous polymer solution A. Then, prepare an iron-zirconium-cobalt metal-organic framework precursor solution B. Next, add solution B to solution A and add a lithium salt, and stir at room temperature for 24 h to obtain a polymer-iron-zirconium-cobalt metal-organic framework solution. Coat it evenly on both sides of the lithium metal anode. After coating, conduct heat treatment for 2 hours, and control the thickness of a single interface layer at 15 microns; c) Assembly and encapsulation of the anode: In an argon atmosphere, stack and assemble the prepared lithium metal anode, separator, and NCM ternary cathode, and encapsulate the assembled battery core under vacuum.

[0062] In step a), the purity of the high-purity lithium metal is not less than 99.9%.

[0063] In step a), the electrochemical deposition current density is controlled at 5 mA / cm 2 , and the deposition temperature is 35 °C.

[0064] In step b), the reaction monomer is polyethylene glycol methacrylate (PEGMMA), and the dosage is 10 g; the initiator is azobisisobutyronitrile, and the dosage is 0.1 g.

[0065] In step b), the lithium salt is LiFSI.

[0066] In step b), the concentration of the iron-zirconium-cobalt metal-organic framework precursor solution is 1.0 mol / L.

[0067] The preparation method of the iron-zirconium-cobalt metal-organic framework precursor solution in step b) is as follows: S1. Mix 20 g of zirconium chloride (ZrCl4), 0.4 g of cobalt chloride (CoCl2), and 54 g of 2,2-bipyridine-5,5-dicarbonyl chloride; react in 300 g of dichloroethane, control the reaction temperature at 55 °C, the pressure is the autogenous pressure, and the reaction time is 60 minutes; S2. Then add 0.4 g of ferrocenyl ethanol and 2.4 g of triethylamine, react at 105 °C for 20 hours, and after the reaction is completed, separate and purify to obtain the iron-zirconium-cobalt metal-organic framework precursor, and dissolve it in absolute ethanol to obtain the iron-zirconium-cobalt metal-organic framework precursor solution.

[0068] Furthermore, in step b), the mixed solution is mixed in a mass ratio of solution A∶solution B∶lithium salt = 1∶8∶1.

[0069] In step b), the heat treatment temperature is 110 °C.

[0070] In step c), the argon atmosphere requires a water content of less than 10 ppm and an oxygen content of less than 1 ppm.

[0071] In step c), the encapsulation pressure is controlled at 80 Pa.

[0072] Example 4

[0073] Replace zirconium chloride in Example 3 with zirconium acetate, and replace cobalt chloride with cobalt acetate.

[0074] Example 5

[0075] Replace zirconium chloride in Example 3 with zirconium sulfate, and replace cobalt chloride with cobalt sulfate.

[0076] Comparative Example 1 This example is a comparative example of Example 1. During the preparation of the iron-zirconium-cobalt metal-organic framework precursor solution, cobalt chloride is not added, and the rest is the same as in Example 1.

[0077] Comparative Example 2 This example is a comparative example of Example 1. During the preparation of the iron-zirconium-cobalt metal-organic framework precursor solution, 2,2'-bipyridine-5,5'-dicarbonyl chloride is not added, and the rest is the same as in Example 1.

[0078] Comparative Example 3 This example is a comparative example of Example 1. During the preparation of the iron-zirconium-cobalt metal-organic framework precursor solution, ferrocenylethanol is not added, and the rest is the same as in Example 1.

[0079] Detection Example 1 (1) Energy density detection Detection method: Assemble a battery using a standard 7 Ah soft-pack battery and perform charge and discharge tests on the battery at 25°C. Perform charge and discharge cycles on the battery at a rate of 0.1C, and record the discharge capacity of the battery.

[0080] Calculate the energy density according to the following formula: Energy density = (discharge capacity × average discharge voltage) / battery weight (2) Cycle life detection Detection method: Use the same soft-pack battery and perform charge and discharge cycles at a rate of 0.5C at 25°C. Record the capacity retention rate of the battery after 200 cycles.

[0081] The results of the energy density detection and the cycle life detection are shown in Table 1, and the cycle curve graph obtained from the cycle life detection is shown in Figure 1 .

[0082] Table 1

[0083] As can be seen from the above table, with the introduction of ferrocene and the zirconium-cobalt bimetallic combination, this MOF material of the metal-organic framework precursor of the present invention can effectively improve the energy density and capacity retention rate of the battery when used as the negative electrode coating of a lithium metal battery. Ferrocene can promote electron transfer, and the presence of zirconium and cobalt optimizes the adsorption and release processes of lithium ions, thereby improving the electrochemical performance.

[0084] Through the above detection methods and comparison results, it can be seen that the high-energy-density solid-state lithium metal battery prepared by the method of the present invention has a significant improvement in terms of energy density and cycle life, demonstrating the technical advantages of the present invention in optimizing the interfacial structure between the lithium metal negative electrode and the solid electrolyte.

Claims

1. A metal-organic framework precursor for a negative electrode coating of a solid-state lithium metal battery, characterized in that, The preparation method comprises the following steps: S1. Mix and react a zirconium source, a cobalt source, and 2,2'-bipyridine-5,5'-dicarbonyl chloride in a first solvent. The zirconium ions in the zirconium source and the cobalt ions in the cobalt source coordinate with the nitrogen atoms and oxygen atoms in 2,2'-bipyridine-5,5'-dicarbonyl chloride to form a zirconium-cobalt / 2,2'-bipyridine-5,5'-dicarbonyl chloride complex; S2. Carry out an esterification reaction between the zirconium-cobalt / 2,2'-bipyridine-5,5'-dicarbonyl chloride complex and ferrocenyl ethanol to obtain the metal-organic framework precursor.

2. The metal-organic framework precursor according to claim 1, wherein, The zirconium source is zirconium chloride, zirconyl chloride, zirconium sulfate, or zirconium acetate; The cobalt source is cobalt chloride, cobalt nitrate, cobalt sulfate, or cobalt acetate; The first solvent is at least one of dichloroethane, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, benzene, and toluene; 3. The metal-organic framework precursor according to claim 1, wherein In step S1, the mass ratio of each raw material is zirconium source∶cobalt source∶2,2'-bipyridine-5,5'-dicarbonyl chloride∶first solvent = 10 - 20∶0.05 - 0.4∶28 - 54∶200 - 300; In step S2, the mass ratio of ferrocenyl ethanol to 2,2'-bipyridine-5,5'-dicarbonyl chloride in step S1 is 0.05 - 0.4∶28 - 54.

4. The metal-organic framework precursor according to claim 1, characterized in that, In step S1, the reaction temperature is 45 - 55°C, and the reaction time is 30 - 60 minutes; in step S2, the reaction temperature of the esterification reaction is 80 - 105°C, and the reaction time is 16 - 20 hours.

5. The metal-organic framework precursor according to claim 1, characterized in that, In step S2, the catalyst for the esterification reaction is triethylamine; the mass ratio of the triethylamine to ferrocenyl ethanol is 0.5 - 2.4∶0.05 - 0.

4.

6. A method for preparing a negative electrode of a solid-state lithium metal battery, characterized in that, Comprises the following steps: (1) Deposit lithium metal on both sides of a copper foil current collector by electrochemical deposition, and a lithium metal layer is formed on each side; (2) Polymerize a polymer monomer under an initiator to obtain a polymer solution A; Dissolve the metal-organic framework precursor according to any one of claims 1 - 5 in a second solvent to obtain a solution B; Mix the solution A, the solution B, and a lithium salt uniformly to obtain a coating slurry; (3) Uniformly coat the coating slurry obtained in step (2) on the surface of the lithium metal layer obtained in step (1), and remove the second solvent to make the coating slurry form an interface layer, thus obtaining the negative electrode of the solid-state lithium metal battery.

7. The method for preparing the negative electrode of the solid-state lithium metal battery according to claim 6, wherein In step (2), the concentration of the solution B is 0.5 - 1.0 mol / L; the mass ratio of the solution A, the solution B, and the lithium salt during mixing is 1∶8∶1; In step (1), the purity of the lithium metal is not less than 99.9%; In step (1), the current density of the electrochemical deposition is 1 - 5 mA / cm 2 , and the deposition temperature is 25 - 35 °C; In step (3), the second solvent is removed by a heat treatment method, and the heat treatment temperature is 95 - 110°C.

8. The method for preparing the negative electrode of the solid-state lithium metal battery according to claim 6, characterized in that In step (2), the polymer monomer is at least one of methyl methacrylate, polyethylene glycol methacrylate, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and polyvinylidene fluoride; The initiator is azobisisobutyronitrile; The lithium salt is at least one of LiClO4, LiPF6, LiBF4, LiFSI, and LiTFSI; The second solvent is ethanol or methanol.

9. A negative electrode of a solid-state lithium metal battery, characterized in that, The negative electrode of the solid-state lithium metal battery is prepared by the preparation method of the negative electrode of the solid-state lithium metal battery according to any one of claims 6 - 8.

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