Lithium metal negative electrode, solid-state lithium ion battery and preparation method of solid-state lithium ion battery

Abstract

The invention relates to the technical field of energy storage batteries, in particular to a lithium metal negative electrode, a solid-state lithium ion battery and a preparation method of the solid-state lithium ion battery. The lithium metal negative electrode comprises a lithium metal body, a second protective layer arranged on one side of the lithium metal body, and a first protective layer arranged on one side, far away from the lithium metal body, of the second protective layer; the first protective layer comprises a lithium-containing functional material; the lithium-containing functional material comprises an inorganic solid electrolyte or a lithium-containing inorganic salt; and the second protective layer comprises a three-dimensional skeleton and a degradable polymer filled in the three-dimensional skeleton. The whole scheme is high in process compatibility, easy to industrialize and suitable for the field of high-energy-density and high-safety solid-state lithium metal batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage batteries, in particular to a lithium metal negative electrode, a solid-state lithium ion battery and a preparation method thereof. BACKGROUND

[0002] With the continuous upgrading of the demand for battery energy density, cycle life and safety of electric vehicles, large-scale energy storage and portable electronic devices, traditional lithium-ion batteries based on graphite negative electrodes (theoretical specific capacity of only 372 mAh / g) and liquid electrolytes have gradually approached the performance ceiling. Under this background, lithium metal negative electrode, with its extremely high theoretical specific capacity (3860 mAh / g) and the lowest redox potential (-3.04 V vs. standard hydrogen electrode), has become a core candidate material to break through the technical bottleneck of high-energy-density batteries. Sulfide solid-state electrolyte, with high room-temperature ionic conductivity (some systems can reach 10-3-10-2 S / cm, close to the level of liquid electrolyte), excellent mechanical toughness (flexible films can be made by cold pressing), and good compatibility with electrode materials, is considered as a key direction to solve the safety problems of liquid electrolyte leakage and combustion. The combination of the two has become the core of research in the field of solid-state lithium metal batteries.

[0003] However, in practical applications, the poor interface matching and insufficient cycle stability of lithium metal negative electrode and sulfide solid-state electrolyte seriously restrict the industrialization process of the system. The natural oxide layer (mainly composed of Li2O, LiOH, Li2CO3) exists on the surface of lithium metal, and its own is a dense metal structure. When it is combined with sulfide solid-state electrolyte (mostly particle agglomerates), micron-sized voids are easily formed at the interface, resulting in a significant increase in interface impedance and seriously hindering ion transport. More importantly, the high reducibility of lithium metal will react with sulfide electrolyte (such as Li2S-P2S5, Li7P3S 11The reaction not only consumes active lithium and electrolyte, but also forms a brittle reaction layer at the interface, further exacerbating the poor interface contact. At the same time, the gas produced during the reaction will cause the interface to peel off, causing the battery internal resistance to continue to rise. Secondly, lithium metal will undergo significant volume changes during charging and discharging cycles. Theoretically, for every 1 μm thickness of lithium metal deposited, the volume expansion rate can be more than 100%. In actual cycles, due to the uneven deposition of lithium, the local expansion rate can even exceed 300%. This severe volume expansion will cause the lithium metal foil to wrinkle and crack, damaging the bonding interface with the protective layer, extruding the sulfide electrolyte layer, causing the electrolyte particles to break, causing the conductive path of the electrolyte layer to break, causing the protective layer formed at the interface to fall off and lose its protective effect, forming a vicious cycle of "expansion-damage-acceleration of side reactions", and ultimately leading to complete failure of the electrode structure. The microscopic protrusions, defects or interface gaps on the surface of the lithium metal will cause uneven current distribution, and high local current density will accelerate the reduction and deposition of lithium ions in this area, forming lithium dendrites. The growth of lithium dendrites not only pierces the sulfide electrolyte layer and causes internal short circuits in the battery, but also causes a large amount of lithium metal to be converted into "dead lithium", causing the battery capacity to rapidly decay. In addition, the growth of lithium dendrites will extrude the interface, further deteriorating the interface contact and SEI film stability, forming a complex situation with multiple problems superimposed.

[0004] The solid electrolyte interface (SEI) film is the key to ensuring the stable cycling of the lithium metal anode, but in the sulfide solid-state electrolyte system, the formation and stability of the SEI film face double challenges. On the one hand, the side reaction products of lithium metal and sulfide electrolyte will randomly dope into the SEI film, resulting in uneven composition of the SEI film, poor mechanical properties, and easy breakage of the SEI film during lithium metal volume change. On the other hand, the traditional SEI film has low ionic conductivity in the sulfide system, which cannot meet the demand for efficient ion transport. The breakage of the SEI film and the low ionic conductivity will cause the newly exposed lithium metal surface to continue to react with the electrolyte, consume active substances, and further increase the ion transport impedance at the interface, resulting in a significant decrease in battery performance. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies and shortcomings of the prior art and provide a lithium metal anode, a solid-state lithium ion battery and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the following solutions are adopted in the present application:

[0007] A lithium metal anode, comprising a lithium metal body, a second protective layer arranged on one side of the lithium metal body, and a first protective layer arranged on the side of the second protective layer away from the lithium metal body.

[0008] The first protective layer comprises a lithium-containing functional material; the lithium-containing functional material comprises an inorganic solid-state electrolyte or a lithium-containing inorganic salt;

[0009] The second protective layer comprises a three-dimensional skeleton and a degradable polymer filled in the three-dimensional skeleton.

[0010] The lithium ion conductivity of the first protective layer is ≥10 -4 S / cm, and the porosity is <5%, preferably prepared by in-situ generation, magnetron sputtering, electron beam evaporation, nano-spraying or atomic layer deposition process.

[0011] The thickness of the first protective layer is 10nm-1000nm; used for improving the interface contact with the solid-state electrolyte layer and inhibiting the sulfide side reaction; the first protective layer and the solid-state electrolyte layer have no chemical reaction in the battery working temperature and voltage range, and do not generate Li3P, Li2S, PH3 and other by-products; ion conductivity: lithium ion conductivity ≥10 -4 S / cm (25℃), avoiding becoming an interface ion transmission bottleneck; film layer denseness: porosity <5%, ensuring physical barrier of direct contact between lithium metal and electrolyte; process compatibility:

[0012] The inorganic solid-state electrolyte of the first protective layer is at least one of oxide inorganic solid-state, sulfide inorganic solid-state electrolyte and halide inorganic solid-state electrolyte;

[0013] Preferably, the oxide inorganic electrolyte comprises at least one of garnet type, perovskite type, NASICON type, LISICON type, NaCl type, LiPON;

[0014] Preferably, the garnet type is LLZO; the perovskite type is LLTO; the NASICON type is LATP or LAGP;

[0015] Preferably, the sulfide inorganic electrolyte comprises at least one of argyrodite type, LGPS type, LPS-based glass ceramic and lithium thiophosphate glass;

[0016] Preferably, the argyrodite type comprises at least one of Li6PS5Cl, medium-chlorine LPSC and high-chlorine LPSC;

[0017] Preferably, the LPS-based glass ceramic comprises Li7P3S 11 ;

[0018] The halide inorganic electrolyte comprises at least one of Li3MX6 type simple halide, complex salt electrolyte, oxygen-containing halide and fluorine-containing halide;

[0019] Preferably, the simple halide of Li3MX6 type includes at least one of Li3YCl6, Li3InCl6;

[0020] Preferably, the complex salt electrolyte includes Li2ZrCl6-LiCl;

[0021] Preferably, the oxygen-containing halide includes at least one of LZOC, LNOC, LTOC;

[0022] Preferably, the fluorine-containing halide includes at least one of Li3YF6 and Li3YCl6 nanocrystal composite;

[0023] The lithium-containing inorganic salt includes one or several of Li3PO4, Li2CO3, LiF, Li2O, Li3N in composite;

[0024] The three-dimensional framework of the second protective layer has an electronic conductivity of ≥100 S / cm, a pore size of 1-30 μm, and a porosity of 50%-80%.

[0025] The three-dimensional framework is used to inhibit the volume expansion of lithium metal and disperse local current, and the degradable polymer is filled in the pores of the three-dimensional framework to optimize the interface ion transmission and stabilize the SEI film. The three-dimensional framework has the following characteristics: chemical compatibility, the three-dimensional framework has no chemical reaction with lithium metal and the degradable polymer within the working temperature and voltage range of the battery, and no by-products such as Li-C alloy and intermetallic compound affecting the performance are generated; the degradation product of the degradable polymer has good compatibility with lithium metal and the solid-state electrolyte layer; high electronic and ionic conductivity, the electronic conductivity of the three-dimensional framework is ≥100 S / cm, which ensures uniform electronic transmission; the small molecule monomers formed after the degradation of the degradable polymer can coordinate with Li + , reduce the ion migration energy barrier, make the overall lithium ion transmission efficiency of the composite structure meet the battery demand, and avoid becoming an ion transmission bottleneck; high structural performance, the three-dimensional framework has a pore size of 1-30 μm and a porosity of 50%-80%, which can provide sufficient space for lithium metal deposition, effectively inhibit the volume expansion rate of lithium metal, and disperse local current through the porous structure to reduce the difference in local current density); good process compatibility, the three-dimensional framework can be prepared by template method, chemical etching method, and powder metallurgy method, the degradable polymer can be filled by impregnation process, the composite structure has no conflict with the thermal compression composite process of lithium metal body, and no skeleton collapse or premature degradation of the polymer occurs; after the composite structure is formed, there is no obvious crack or hole, the polymer is uniformly filled in the pores of the skeleton, which ensures that there is no local exposure during the lithium metal deposition process, and avoids the growth of lithium dendrites from the defects.

[0026] The thickness of the second protective layer is 1-20 mu m, which is used for inhibiting the volume expansion in the lithium metal charging and discharging process, dispersing the local current to reduce the lithium dendrite growth, optimizing the interface ion transmission efficiency and assisting in building a stable SEI film; the three-dimensional skeleton after filling the polymer is combined with the lithium metal body through hot pressing, so that the second protective layer is combined closely with the lithium metal body, and the interlayer bonding force is greater than or equal to 5 N / m.

[0027] Preferably, the three-dimensional skeleton material is any one of a self-porous carbon skeleton or a porous metal skeleton;

[0028] Preferably, the porous carbon skeleton is any one of a graphite-based porous carbon skeleton or a carbon nanotube-based porous carbon skeleton;

[0029] Preferably, the porous metal skeleton is any one of a porous copper, a porous aluminum or a porous nickel;

[0030] Preferably, the degradable polymer is one or more of polycaprolactone (PCL), polylactic acid (PLA), polyglycolic acid (PGA), PCL-PLA copolymer, PGA-caprolactone copolymer, polybutylene carbonate (PBC), polyvinylidene carbonate (PEC) and polypropylene carbonate (PPC);

[0031] The filling rate of the degradable polymer is 60%-90% of the filling amount to the pore volume of the skeleton; the degradable polymer is filled into the three-dimensional skeleton through a solution immersion and vacuum drying process;

[0032] The thickness ratio of the first protective layer to the second protective layer is 1:(8-16)

[0033] The lithium metal body is at least one of pure lithium metal, a binary lithium alloy, a ternary lithium alloy and a quaternary lithium alloy;

[0034] Preferably, the binary lithium alloy is at least one of a lithium-magnesium alloy, a lithium-indium alloy, a lithium-boron alloy and a lithium-silver alloy;

[0035] Preferably, the ternary lithium alloy is at least one of a lithium-boron-silver alloy and a lithium-boron-magnesium alloy

[0036] Preferably, the thickness of the lithium metal body is 20-200 mu m;

[0037] Preferably, the lithium metal body is attached to the surface of a metal current collector; and preferably, the metal current collector is selected from one of a copper foil, an aluminum foil, a nickel foil, a stainless steel foil, a copper-aluminum composite foil and a nickel-plated copper foil.

[0038] The application also includes a preparation method of the lithium metal negative electrode, which comprises the following steps:

[0039] 1) preparation of the second protective layer; 2) the lithium metal body and the double-layer interface protection structure are integrated by pressure compounding; specifically comprising the following steps: the lithium metal body is laid on the surface of the metal current collector, the second protective layer film is first attached to the flat surface of the lithium metal body, then the first protective layer mixture is sprayed to the surface of the second protective layer film to form a laminated structure; the laminated structure is put into an isostatic pressing machine to obtain a lithium metal negative electrode by pressure compounding; the interlayer bonding force is greater than or equal to 5N / m.

[0040] The application also includes a solid-state battery, characterized in that it comprises the lithium metal negative electrode, the solid-state electrolyte layer and the positive electrode; the active material of the positive electrode is LiCoO2, NCM or LiFePO4.

[0041] The application also includes a preparation method of the solid-state battery, comprising the following steps: the sulfide electrolyte powder is laid on the bottom of the mold, and after the sulfide solid-state electrolyte layer is formed by pressure, the first protective layer of the lithium metal negative electrode is attached to one side and the positive electrode is attached to the other side to form a sandwich structure of "lithium metal negative electrode-solid-state electrolyte layer-positive electrode"; pressure is applied to the mold, and the upper end nut of the mold is tightened to fix, and the solid-state battery is obtained.

[0042] Compared with the prior art, the application has the following beneficial effects:

[0043] The first protective layer in the double-layer interface protection structure can effectively improve the interface contact performance with the sulfide solid-state electrolyte, reduce the interface gap, and at the same time inhibit the occurrence of sulfide side reactions, protect the structural stability of the sulfide solid-state electrolyte, and prolong the service life of the electrolyte.

[0044] The small molecule monomers produced by the degradation of the degradable polymer in the second protective layer can significantly improve the interface ion transmission efficiency, reduce the ion transmission impedance, and improve the rate performance of the battery. The three-dimensional skeleton structure in the second protective layer has good mechanical support effect, which can effectively inhibit the volume expansion of the lithium metal negative electrode during the charging and discharging process, and avoid the destruction of the electrode structure caused by the volume change; at the same time, the porous characteristics of the three-dimensional skeleton structure can disperse the current, reduce the local current density, reduce the growth of lithium dendrites, and improve the cycle stability and safety of the battery. The second protective layer can provide a stable interface environment for the formation of the SEI film, which is helpful to build a SEI film with complete structure and stable performance, further improve the interface stability, and reduce the occurrence of interface side reactions.

[0045] The first protective layer effectively improves the interface contact and inhibits the sulfide side reaction, reduces the interface impedance, the second protective layer has a three-dimensional skeleton that reduces the volume expansion rate of lithium metal and disperses the local current to avoid lithium dendrite growth; the degradable polymer optimizes ion transmission after degradation and assists in forming a stable SEI film; the overall scheme has strong process compatibility and is easy to industrialize, and is suitable for the field of high-energy density and high-safety solid-state lithium metal batteries. DETAILED DESCRIPTION

[0046] The application will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0047] A lithium metal negative electrode, comprising a lithium metal body, a second protective layer arranged on one side of the lithium metal body, and a first protective layer arranged on the side of the second protective layer away from the lithium metal body;

[0048] Embodiment 1: The thickness ratio of the first protective layer to the second protective layer of the lithium metal negative electrode of this embodiment is 1:16;

[0049] The first protective layer comprises inorganic lithium salt composite powder (Li3PO4-Li2CO3, the mass ratio of the two is 1:1), non-fibrous binder, and electrolyte additive, and the mass ratio is 85:10:5; the non-fibrous binder of the first protective layer is polyvinylidene fluoride, the electrolyte additive is polyether modified siloxane, the lithium ion conductivity of the first protective layer is ≥1*10 -4 S / cm, and the porosity is 4.5%;

[0050] The lithium metal body used in this embodiment is a 100um lithium-indium alloy foil, the metal current collector is a copper foil current collector, and the sulfide solid electrolyte layer is LPSC;

[0051] I. A method for preparing a lithium metal negative electrode, comprising the following steps:

[0052] 1. As a three-dimensional skeleton, the substance of the powder material can be added with a dispersing agent and a fibrous binder to form a film. Specifically, the graphite-based porous carbon powder, PCL, CNT and PTFE (mass ratio 50:40:5:5) corresponding to the mass ratio of the second protective layer are added into a high-speed mixer and mixed for 15 minutes, and then transferred into a double screw extruder for homogenization to obtain the fibrous second protective layer material; the second protective layer material is formed into a film using a dry film forming machine, and thinned to 20μm, the three-dimensional skeleton has a pore size of 1μm and a porosity of 53%, to obtain a second protective layer film;

[0053] 2. The lithium metal body and the double-layer interface protection structure are integrally formed by pressure compounding; the lithium-indium alloy is laid on the carbon-coated side of the copper foil current collector, the second protection layer film is first attached to the surface of the lithium metal foil (away from the current collector side), and then the mixture of the first protection layer film is sprayed to the surface of the second protection layer film (away from the lithium metal side), to form a laminated structure of “copper foil current collector-lithium-indium alloy-second protection layer-first protection layer”; the laminated structure is placed into an isostatic press, and is subjected to isostatic pressing at a pressure of 50 MPa and a temperature of 80°C for 10 min, to obtain a lithium metal negative electrode sheet with a surface capacity of 5 mAh / cm 2 .

[0054] II. The preparation steps of the solid-state lithium ion battery are as follows: in an argon atmosphere glove box (O2 content ≤0.1 ppm, H2O content ≤0.1 ppm), the sulfide solid-state electrolyte powder is laid on the bottom of a mold, and the solid-state electrolyte film layer is obtained by pressure forming, then a lithium metal negative electrode is attached on one side (the first protection layer side faces the sulfide solid-state electrolyte layer), and a positive electrode is attached on the other side, to assemble a sandwich structure of “lithium metal negative electrode-solid-state electrolyte layer-positive electrode sheet”; a pressure is applied to the mold, and the upper end nut of the mold is tightened after being kept for 30 s, to obtain a solid-state battery.

[0055] Comparative Example 1: The difference between the comparative example and Example 1 is only that a 100 um lithium-indium alloy foil is directly used as the negative electrode to prepare a solid-state lithium ion battery.

[0056] Example 2: The thickness ratio of the first protection layer to the second protection layer of the lithium metal negative electrode in this example is 1:8.

[0057] The first protection layer is composed of a solid-state electrolyte (LLZTO), a non-fibrous binder and an electrolyte additive, with a mass ratio of 85:10:5; the non-fibrous binder of the first protection layer is polyvinylidene fluoride, and the electrolyte additive is polyether-modified siloxane; the lithium ion conductivity of the first protection layer is 4*10 -4 S / cm, and the porosity is 4%.

[0058] The second protection layer comprises a three-dimensional skeleton and a degradable polymer, with a mass ratio of 50:50; the three-dimensional skeleton material of the second protection layer is a nickel metal three-dimensional skeleton, with a pore size of 3 μm and a porosity of 65%; and the degradable polymer is polycarbonate propylene.

[0059] The lithium metal body used in this example is a 100 um lithium-indium alloy foil, and the metal current collector is a copper foil current collector; the sulfide solid-state electrolyte layer is LPSC.

[0060] I. A preparation method of a lithium metal negative electrode, comprising the following steps:

[0061] 1. For the three-dimensional skeleton itself is film-like, can adopt the method of impregnation to prepare: the degradable polymer PPC is dissolved in tetrahydrofuran, and a solution with a mass concentration of 8% is prepared, and the three-dimensional metal skeleton is impregnated by vacuum assisted, and the solvent is removed by vacuum drying to realize uniform filling of the polymer, and a second protective layer film is obtained.

[0062] 2. The lithium-indium alloy foil is laid on the carbon coating side of the copper foil current collector, the second protective layer film is first attached to the surface of the lithium metal foil (away from the current collector side), and the first protective layer film is sprayed to the surface of the second protective layer film (away from the lithium metal side), forming a "metallic current collector copper foil-lithium-indium alloy-second protective layer-first protective layer" laminated structure; the laminated structure is placed into an isostatic press, and is subjected to isostatic pressing at a pressure of 50 MPa and a temperature of 80°C for 10 min, to obtain a lithium metal negative electrode sheet with a surface capacity of 5 mAh / cm 2 .

[0063] The preparation steps of the solid-state lithium ion battery are as follows: in an argon atmosphere glove box (O2 content ≤0.1 ppm, H2O content ≤0.1 ppm), the sulfide solid electrolyte powder is laid on the bottom of the mold, and after being pressed into a sheet, one side is attached to the lithium metal negative electrode (the first protective layer side faces the electrolyte layer), and the other side is attached to the positive electrode sheet, to form a "lithium metal negative electrode-solid-state electrolyte layer-positive electrode" sandwich structure; a pressure is applied to the mold, and after being kept for 30 s, the upper end nut of the mold is tightened to fix, to obtain a special lithium metal negative electrode lithium ion battery for a sulfide solid electrolyte system.

[0064] Example 3: The preparation method is consistent with that of Example 1, except that the lithium-containing functional material of the first protective layer in Example 3 is LLZTO, the lithium ion conductivity is ≥3.8*10 -4 S / cm, the porosity is 4%, the three-dimensional skeleton material of the second protective layer is a graphite-based porous carbon layer, the degradable polymer is polypropylene carbonate, and the lithium metal body is a lithium metal foil.

[0065] Example 4: The preparation method is consistent with that of Example 2, except that the lithium-containing functional material of the first protective layer in Example 3 is LiF+Li2O (1:1) composite powder, the three-dimensional skeleton material of the second protective layer is a foam copper, the degradable polymer is PLC, and the lithium metal body is a lithium metal foil.

[0066] The test results of Examples 1-4 and Comparative Example 1 are shown in Table 1.

[0067] Table 1

[0068]

[0069] In summary, the application adopts a double-layer interface protection structure, the first protective layer can effectively improve the interface contact performance with the sulfide solid electrolyte, reduce the interface gap, and at the same time inhibit the occurrence of sulfide side reactions, protect the structural stability of the sulfide solid electrolyte, and prolong the service life of the electrolyte.

[0070] The small molecule monomers generated after the degradation of the degradable polymer in the second protective layer can significantly improve the interface ion transmission efficiency, reduce the ion transmission impedance, and improve the rate performance of the battery. The three-dimensional skeleton structure in the second protective layer has good mechanical support effect, which can effectively inhibit the volume expansion of the lithium metal anode during the charging and discharging process, and avoid the destruction of the electrode structure caused by the volume change; at the same time, the porous characteristics of the three-dimensional skeleton structure can disperse the current, reduce the local current density, reduce the growth of lithium dendrites, and improve the cycle stability and safety of the battery. The second protective layer can provide a stable interface environment for the formation of the SEI film, which is helpful to build a SEI film with complete structure and stable performance, further improve the interface stability, and reduce the occurrence of interface side reactions.

[0071] The above shows and describes the basic principles and main features of the present application and the advantages of the present application, and it is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application;

[0072] Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

[0073] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that those skilled in the art can understand.

Claims

1. A lithium metal anode, characterized in that, It includes a lithium metal body, a second protective layer disposed on one side of the lithium metal body, and a first protective layer disposed on the side of the second protective layer away from the lithium metal body; The first protective layer includes a lithium-containing functional material; the lithium-containing functional material includes an inorganic solid electrolyte or a lithium-containing inorganic salt. The second protective layer includes a three-dimensional skeleton and a biodegradable polymer filled within the three-dimensional skeleton.

2. The lithium metal anode according to claim 1, characterized in that, The first protective layer has a lithium-ion conductivity ≥10. -4 S / cm, porosity <5%, preferably prepared by in-situ generation, magnetron sputtering, electron beam evaporation, nano-spraying or atomic layer deposition processes.

3. The lithium metal anode according to claim 1, characterized in that, The inorganic solid electrolyte is at least one of oxide inorganic solid electrolyte, sulfide inorganic solid electrolyte, and halide inorganic solid electrolyte; Preferably, the oxide inorganic electrolyte includes at least one of garnet type, perovskite type, NASICON type, LISICON type, sodalite type, and LiPON; preferably, the garnet type is LLZO; the perovskite type is LLTO; and the NASICON type is LATP or LAGP. Preferably, the sulfide inorganic electrolyte includes at least one of silver-germanium sulfide type, LGPS type, LPS-based glass ceramic, and lithium thiophosphate glass; preferably, the silver-germanium sulfide type includes at least one of Li5PS5Cl, medium-chlorine LPSC, and high-chlorine LPSC; preferably, the LPS-based glass ceramic includes Li7P3S 11 ; Preferably, the halide inorganic electrolyte includes at least one of Li3MX6 type simple halides, complex salt electrolytes, oxygen-containing halides, and fluorine-containing halides; preferably, the Li3MX5 type simple halides include at least one of Li3YCl5 and Li3InCl5; preferably, the complex salt electrolyte includes Li2ZrCl6-LiCl. Preferably, the oxygen-containing halide includes at least one of LZOC, LNOC, and LTOC; preferably, the fluorine-containing halide includes at least one of Li3YF5 and Li3YF5 nanocrystalline composite. Preferably, the lithium-containing inorganic salt includes one or more of Li3PO4, Li2CO3, LiF, Li2O, and Li3N.

4. The lithium metal anode according to claim 1, characterized in that, The three-dimensional framework has an electronic conductivity ≥100 S / cm, a pore size of 1–30 μm, and a porosity of 50%–80%. Preferably, the three-dimensional framework material is any one of a porous carbon framework or a porous metal framework; preferably, the porous carbon framework is any one of a graphite-based porous carbon framework or a carbon nanotube-based porous carbon framework; preferably, the porous metal framework is any one of porous copper, porous aluminum, or porous nickel. Preferably, the biodegradable polymer is one or more of polycaprolactone (PCL), polylactic acid (PLA), polyglycolic acid (PGA), PCL-PLA copolymer, PGA-caprolactone copolymer, polybutylene carbonate (PBC), polyvinyl carbonate (PEC), and polypropylene carbonate (PPC). The biodegradable polymer is filled at a rate of 60% to 90% of the pore volume of the skeleton.

5. The lithium metal anode according to claim 1, characterized in that, The thickness ratio of the first protective layer to the second protective layer is 1:(8-16).

6. The lithium metal anode according to claim 1, characterized in that, The lithium metal body is at least one of pure lithium metal, binary lithium alloy, ternary lithium alloy, and quaternary lithium alloy; Preferably, the binary lithium alloy is at least one of lithium-magnesium alloy, lithium-indium alloy, lithium-boron alloy, and lithium-silver alloy; Preferably, the ternary lithium alloy is at least one of lithium-boron-silver alloy and lithium-boron-magnesium alloy. Preferably, the thickness of the lithium metal body is 20–200 μm; Preferably, the lithium metal body is attached to the surface of the metal current collector; preferably, the metal current collector is selected from one of copper foil, aluminum foil, nickel foil, stainless steel foil, copper-aluminum composite foil, and nickel-plated copper foil.

7. The method for preparing a lithium metal anode according to claims 1-6, characterized in that, The process includes the following steps: 1) preparing a second protective layer; 2) bonding the lithium metal body to the second protective layer and then spraying the first protective layer onto the surface of the second protective layer: pressurized composite to obtain a lithium metal anode.

8. The preparation method according to claim 7, characterized in that, Step 2) The specific steps are as follows: the lithium metal body is laid flat on the surface of the metal current collector, the second protective layer film is first attached to the flat surface of the lithium metal body, and then the first protective layer mixture is sprayed onto the surface of the second protective layer film to form a stacked structure; the stacked structure is placed in an isostatic press for pressure bonding to obtain the lithium metal anode; the interlayer bonding force is ≥5N / m.

9. A solid-state battery, characterized in that, It includes the lithium metal anode, solid electrolyte layer and positive electrode as described in claims 1-7; the active material of the positive electrode is LiCoO2, NCM or LiFePO4.

10. A method for preparing a solid-state battery according to claim 9, comprising the following steps: spreading sulfide electrolyte powder on the bottom of a mold, pressing it into a sulfide solid electrolyte layer, attaching the first protective layer of the lithium metal anode to one side, and attaching the positive electrode to the other side, assembling a sandwich structure of "lithium metal anode-solid electrolyte layer-positive electrode"; applying pressure to the mold, and tightening the nut at the top of the mold to fix it, thereby obtaining a solid-state battery.

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