Preparation method of lithium-germanium-phosphorus-sulfur solid-state battery

Abstract

The invention relates to a preparation method of a lithium germanium phosphorus sulfur solid-state battery. The preparation method comprises the following steps: uniformly stirring and mixing a lithium compound, a germanium compound, a phosphorus compound and a synergist, tabletting, carrying out high-temperature heat treatment, cooling to room temperature, and carrying out ball milling to obtain the sulfur-based solid electrolyte. Uniformly mixing resin and lithium salt to obtain an organic solid electrolyte; uniformly mixing the sulfur-based solid electrolyte and the organic solid electrolyte to obtain a base material; adding the base material into the impregnation liquid for impregnation, and performing vacuum drying to obtain the lithium germanium phosphorus sulfur material for the all-solid-state battery, the preparation method comprises the following steps: dissolving a nickel-cobalt-manganese ternary positive electrode active material, a carbon nanotube, polyoxyethylene and lithium bis (trifluoromethanesulfonimide) into dimethyl amide, and stirring to obtain a uniform positive electrode precursor solution; casting the positive electrode precursor solution onto the solid electrolyte, and performing vacuum drying to obtain a positive electrode and the solid electrolyte which are in close contact; and transferring into an argon glove box, and assembling into an all-solid-state battery by taking a metal lithium sheet as a negative electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery. Background Art

[0002] With the progress of technology and the increasing demand for clean energy, lithium-ion batteries have been widely used in fields such as electric vehicles and grid energy storage1. However, the flammable organic electrolytes used in traditional lithium-ion batteries have safety hazards, such as electrolyte leakage, spontaneous combustion and explosion, which limit their further development1. All-solid-state batteries conduct ions through solid electrolytes, and are less flammable and volatile than traditional liquid batteries, with significantly improved safety, so they have become a research hotspot for the next-generation lithium-ion battery technology.

[0003] Chinese Patent CN114914527B: discloses a bismuth-doped lithium-germanium-phosphorus-sulfur solid electrolyte and its preparation method, which is to grind and mix Li2S, CeS2, Bi2S3, and P2S5 under an argon atmosphere, and then ball-mill using a ball mill to obtain a mixed powder; the obtained mixed powder is sealed and calcined in an inert gas atmosphere to obtain a bismuth-doped lithium-germanium-phosphorus-sulfur solid electrolyte with the composition: LixGe1-yBiyP2S 12 where 10 < x < 10.5, 0 < y < 0.5.

[0004] Chinese Patent CN118899435A: doped sulfide materials and their preparation methods, lithium-ion batteries. The crystal of the doped sulfide material includes: a cubic crystal form with a space point group of #imgabs0#; at least one site in the unit cell constituting the crystal is doped with a doping group, and the doping group includes: nitrogen element N.

[0005] Sulfide solid electrolytes still face many challenges in practical applications. For example, the interfacial stability between it and the electrode is poor, which easily leads to an increase in interfacial impedance and affects the charge and discharge performance of the battery; the mechanical properties of sulfide solid electrolytes are relatively weak, and cracks and breakages are likely to occur during the charge and discharge process of the battery, thereby reducing the service life of the battery; in addition, its chemical stability also needs to be improved, and it is easy to undergo chemical reactions when contacting with electrode materials, resulting in a decline in battery performance. Therefore, it is of great practical significance to develop a synergist that can effectively improve the interfacial performance of sulfide solid electrolytes, and improve their mechanical properties and chemical stability. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery, and its operation steps are as follows:

[0007] S1 Preparation of sulfur-based solid electrolyte: Mix 16-22 parts of lithium compound, 14-20 parts of germanium compound, 72-88 parts of phosphorus compound, and 0.1-0.5 part of synergist evenly by stirring, then press into tablets. After high-temperature heat treatment, cool to room temperature and carry out ball milling to obtain the sulfur-based solid electrolyte;

[0008] S2 Preparation of organic solid electrolyte: Mix 15-40 parts of resin and 5-20 parts of lithium salt evenly to obtain the organic solid electrolyte;

[0009] S3 Preparation of base material: Mix 24-36 parts of sulfur-based solid electrolyte and 15-30 parts of organic solid electrolyte evenly to obtain the base material;

[0010] S4 Preparation of lithium germanium phosphorus sulfur solid electrolyte material: Immerse the base material in the impregnating solution for 12-24 h, then carry out drying and curing under vacuum conditions with a vacuum degree of -0.06 to -0.1 MPa, a temperature of 120-160 °C, and a time of 2-4 h to obtain the lithium germanium phosphorus sulfur material for all-solid-state batteries;

[0011] S5 Preparation of cathode precursor solution: Dissolve 70-90 parts of nickel cobalt manganese ternary cathode active material, 10-20 parts of carbon nanotubes, 5-10 parts of polyethylene oxide, and 1-5 parts of lithium bis(trifluoromethanesulfonyl)imide in 5-10 parts of dimethylformamide, and stir at 50-60 °C for 4-6 h to obtain a uniform cathode precursor solution;

[0012] S6 Preparation of cathode and solid electrolyte: Cast the cathode precursor solution onto the solid electrolyte, and carry out vacuum drying at 70-80 °C for 8-12 h to obtain a cathode and solid electrolyte with close contact;

[0013] S7 Battery assembly: Transfer to an argon glove box and assemble into an all-solid-state battery with a lithium metal sheet as the negative electrode.

[0014] The lithium compound is a mixture of lithium sulfide and lithium oxide, the germanium compound is a mixture of germanium sulfide and germanium oxide, and the phosphorus compound is a mixture of phosphorus pentasulfide and phosphorus pentoxide.

[0015] The pressure for pressing the tablets is 200-300 MPa.

[0016] The temperature of the heat treatment is 650-750 °C, and the time is 200-240 min.

[0017] The ball milling speed is 350-500 r / min, and the time is 56-72 h.

[0018] The resin is one of polyethylene oxide, polyacrylonitrile, and ethylene glycol polyacrylate.

[0019] The lithium salt described above is one of lithium perchlorate, lithium bis(oxalato)borate, and lithium bis(trifluoromethanesulfonyl)imide.

[0020] The impregnating solution described above is one of dimethyl sulfoxide, dimethyl sulfite, and N,N-dimethylformamide.

[0021] The preparation method of the synergist is as follows:

[0022] A1: By weight, add 20-30 parts of tetraarm polyethylene glycol acrylamide, 10-20 parts of 1,1'-diaminferrocene, 0.35-0.7 parts of lanthanum acrylate, 2-5 parts of 1,4-diazabicyclo[2.2.2]octane, and 200-300 parts of N,N-dimethylformamide into a closed high-pressure reactor. Under the protection of nitrogen, react at a temperature of 70-90 °C for 10-15 hours.

[0023] A2: After the reaction is completed, remove N,N-dimethylformamide by distillation, and then vacuum dry at 60-70 °C for 12-18 hours to obtain the synergist.

[0024] Reaction mechanism

[0025] The acrylamide group in tetraarm polyethylene glycol acrylamide and the amino group in 1,1'-diaminferrocene undergo an addition reaction under the action of 1,4-diazabicyclo[2.2.2]octane as a catalyst. 1,4-Diazabicyclo[2.2.2]octane, as an organic base catalyst, can promote the nucleophilic addition reaction of the amino group to the carbon-carbon double bond in acrylamide to form a new chemical bond, thereby connecting tetraarm polyethylene glycol acrylamide and 1,1'-diaminferrocene. At the same time, the lanthanum ions in lanthanum acrylate can coordinate with the functional groups in the reaction product to further promote intermolecular crosslinking and form a synergist with certain structures and properties.

[0026] Technical effects

[0027] The preparation method of a lithium germanium phosphorus sulfur solid-state battery of the present invention has the following remarkable effects compared with the prior art:

[0028] 1. Improve interface performance: Tetraarm polyethylene glycol acrylamide has good flexibility and scalability, can form a stable interface layer between the sulfide solid electrolyte and the electrode, effectively reduce the interface impedance, and improve the charge and discharge efficiency of the battery; the ferrocene group in 1,1'-diaminferrocene can interact with the ions in the sulfide solid electrolyte to further enhance the stability of the interface.

[0029] 2. Improve mechanical properties: The additive of the present invention forms a three-dimensional network structure in the sulfide solid electrolyte, enhancing the mechanical strength of the electrolyte, reducing the generation of cracks and breakages during battery charge and discharge processes, and increasing the service life of the battery.

[0030] 3. Enhance chemical stability: The addition of lanthanum acrylate can undergo chemical reactions with the components in the sulfide solid electrolyte to form stable chemical bonds, inhibiting adverse reactions between the electrolyte and electrode materials and improving the chemical stability of the electrolyte.

[0031] 4. Good compatibility: The additive has good compatibility with the sulfide solid electrolyte, can be evenly dispersed in the electrolyte, and will not have a negative impact on the ionic conductivity of the electrolyte. Detailed implementation manners

[0032] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in combination with examples and comparative examples:

[0033] 1. Ionic conductivity test: The ionic conductivity of the prepared solid electrolyte was tested using an alternating current impedance spectroscopy (EIS) on an autolab workstation, and the test frequency range was from 0.1 Hz to 106 Hz; the ionic conductivity of the solid electrolyte was calculated based on the impedance value and the Arrhenius equation.

[0034] 2. Electrochemical performance test: At a 1C rate, the initial specific capacity was tested, and after 100 charge-discharge cycles, the capacity retention rate was tested.

[0035] Example 1

[0036] A preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery, and its operation steps are as follows:

[0037] S1. Prepare a sulfur-based solid electrolyte: Mix 16 g of a lithium compound, 14 g of a germanium compound, 72 g of a phosphorus compound, and 0.1 g of a synergist evenly by stirring, perform tabletting, after high-temperature heat treatment, cool to room temperature, and perform ball milling to obtain a sulfur-based solid electrolyte;

[0038] S2. Prepare an organic solid electrolyte: Mix 15 g of a resin and 5 g of a lithium salt evenly to obtain an organic solid electrolyte;

[0039] S3. Prepare a base material: Mix 24 g of the sulfur-based solid electrolyte and 15 g of the organic solid electrolyte evenly to obtain a base material;

[0040] S4 Preparation of lithium germanium phosphorus sulfur solid electrolyte material: The base material is added to the impregnating solution and impregnated for 12 h, and then dried and solidified under vacuum conditions with a vacuum degree of -0.06 MPa, a temperature of 120 °C, and a time of 2 h to obtain the lithium germanium phosphorus sulfur material for all-solid-state batteries;

[0041] S5 Preparation of the positive electrode precursor solution: 70 g of nickel cobalt manganese ternary positive electrode active material, 10 g of carbon nanotubes, 5 g of polyethylene oxide, and 1 g of lithium bis(trifluoromethanesulfonyl)imide are dissolved in 5 g of dimethylformamide and stirred at 50 °C for 4 h to obtain a uniform positive electrode precursor solution;

[0042] S6 Preparation of the positive electrode and the solid electrolyte: The positive electrode precursor solution is cast onto the solid electrolyte and vacuum dried at 70 °C for 8 h to obtain a positive electrode and a solid electrolyte with close contact;

[0043] S7 Battery assembly: Transfer to an argon glove box and assemble into an all-solid-state battery with a lithium metal sheet as the negative electrode.

[0044] The lithium compound is a mixture of lithium sulfide and lithium oxide, the germanium compound is a mixture of germanium sulfide and germanium oxide, and the phosphorus compound is a mixture of phosphorus pentasulfide and phosphorus pentoxide.

[0045] The pressure of the tablet pressing is 200 MPa.

[0046] The temperature of the heat treatment is 650 °C and the time is 200 min.

[0047] The ball milling speed is 350 r / min and the time is 56 h.

[0048] The resin is polyethylene oxide.

[0049] The lithium salt is lithium perchlorate.

[0050] The impregnating solution is dimethyl sulfoxide.

[0051] The preparation method of the synergist is as follows:

[0052] A1: 20 g of tetraarm polyethylene glycol acrylamide, 10 g of 1,1'-diaminodicyclopentadiene, 0.35 g of lanthanum acrylate, 2 g of 1,4-diazabicyclo[2.2.2]octane, and 200 g of N,N-dimethylformamide are added to a closed high-pressure reactor and reacted at 70 °C for 10 hours under nitrogen protection;

[0053] A2: After the reaction is completed, N,N-dimethylformamide is removed by distillation, and then vacuum dried at 60 °C for 12 hours to obtain the synergist.

[0054] Example 2

[0055] A preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery, and its operation steps are as follows:

[0056] S1 Prepare a sulfur-based solid electrolyte: Mix 18 g of a lithium compound, 16 g of a germanium compound, 76 g of a phosphorus compound, and 0.2 g of a synergist evenly by stirring, perform tabletting, after high-temperature heat treatment, cool to room temperature, and perform ball milling to obtain a sulfur-based solid electrolyte;

[0057] S2 Prepare an organic solid electrolyte: Mix 20 g of a resin and 10 g of a lithium salt evenly to obtain an organic solid electrolyte;

[0058] S3 Prepare a base material: Mix 28 g of the sulfur-based solid electrolyte and 20 g of the organic solid electrolyte evenly to obtain a base material;

[0059] S4 Prepare a lithium-germanium-phosphorus-sulfur solid electrolyte material: Immerse the base material in an impregnating solution for 16 h, and then perform drying and curing under vacuum conditions with a vacuum degree of -0.07 MPa, a temperature of 130 °C, and a time of 3 h to obtain a lithium-germanium-phosphorus-sulfur material for all-solid-state batteries;

[0060] S5 Prepare a positive electrode precursor solution: Dissolve 75 g of a nickel-cobalt-manganese ternary positive electrode active material, 13 g of carbon nanotubes, 6 g of polyethylene oxide, and 2 g of lithium bis(trifluoromethanesulfonyl)imide in 6 g of dimethylformamide, and stir at 55 °C for 5 h to obtain a uniform positive electrode precursor solution;

[0061] S6 Prepare a positive electrode and a solid electrolyte: Cast the positive electrode precursor solution onto the solid electrolyte, and perform vacuum drying at 75 °C for 9 h to obtain a positive electrode and a solid electrolyte with close contact;

[0062] S7 Assemble the battery: Transfer it to an argon glove box, and use a lithium metal sheet as the negative electrode to assemble an all-solid-state battery.

[0063] The lithium compound is a mixture of lithium sulfide and lithium oxide, the germanium compound is a mixture of germanium sulfide and germanium oxide, and the phosphorus compound is a mixture of diphosphorus pentasulfide and phosphorus pentoxide.

[0064] The pressure of the tabletting is 240 MPa.

[0065] The temperature of the heat treatment is 680 °C, and the time is 210 min.

[0066] The ball milling speed is 400 r / min, and the time is 60 h.

[0067] The resin is polyacrylonitrile.

[0068] The lithium salt is lithium bis(oxalato)borate.

[0069] The impregnating solution is dimethyl sulfite.

[0070] The preparation method of the synergist is as follows:

[0071] A1: Add 23 g of tetraarm polyethylene glycol acrylamide, 13 g of 1,1'-diaminof errocene, 0.45 g of lanthanum acrylate, 3 g of 1,4-diazabicyclo[2.2.2]octane, and 240 g of N,N-dimethylformamide into a closed high-pressure reaction kettle. Under the condition of nitrogen protection, react at 75 °C for 12 hours;

[0072] A2: After the reaction, remove N,N-dimethylformamide by distillation, and then vacuum dry at 65 °C for 14 hours to obtain the synergist.

[0073] Example 3

[0074] A preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery, and its operation steps are as follows:

[0075] S1 Prepare a sulfur-based solid electrolyte: Stir and mix 20 g of a lithium compound, 18 g of a germanium compound, 85 g of a phosphorus compound, and 0.4 g of a synergist evenly, perform tabletting, after high-temperature heat treatment, cool to room temperature, and perform ball milling to obtain a sulfur-based solid electrolyte;

[0076] S2 Prepare an organic solid electrolyte: Mix 35 g of a resin and 15 g of a lithium salt evenly to obtain an organic solid electrolyte;

[0077] S3 Prepare a base material: Mix 33 g of a sulfur-based solid electrolyte and 25 g of an organic solid electrolyte evenly to obtain a base material;

[0078] S4 Prepare a lithium-germanium-phosphorus-sulfur solid electrolyte material: Immerse the base material in an impregnating solution for 20 h, and then perform drying and curing under vacuum conditions, with a vacuum degree of -0.09 MPa, a temperature of 150 °C, and a time of 3 h, to obtain a lithium-germanium-phosphorus-sulfur material for an all-solid-state battery;

[0079] S5 Prepare a positive electrode precursor solution: Dissolve 85 g of a nickel-cobalt-manganese ternary positive electrode active material, 18 g of carbon nanotubes, 8 g of polyethylene oxide, and 4 g of lithium bis(trifluoromethanesulfonyl)imide in 8 g of dimethylformamide, and stir at 55 °C for 5 h to obtain a uniform positive electrode precursor solution;

[0080] S6 Prepare a positive electrode and a solid electrolyte: Cast the positive electrode precursor solution onto the solid electrolyte, and then vacuum dry at 75 °C for 11 h to obtain a positive electrode and a solid electrolyte with close contact;

[0081] S7 Assemble the battery: Transfer to an argon glove box, and use a lithium metal sheet as the negative electrode to assemble an all-solid-state battery.

[0082] The lithium compound is a mixture of lithium sulfide and lithium oxide, the germanium compound is a mixture of germanium sulfide and germanium oxide, and the phosphorus compound is a mixture of diphosphorus pentasulfide and diphosphorus pentoxide.

[0083] The pressure of the tablet pressing is 280 MPa.

[0084] The temperature of the heat treatment is 730 °C and the time is 230 min.

[0085] The ball milling speed is 450 r / min and the time is 68 h.

[0086] The resin is polyacrylonitrile.

[0087] The lithium salt is lithium bis(oxalato)borate.

[0088] The impregnating solution is dimethyl sulfite.

[0089] The preparation method of the synergist is as follows:

[0090] A1: Add 28 g of tetraarm polyethylene glycol acrylamide, 18 g of 1,1'-diaminocferrocene, 0.6 g of lanthanum acrylate, 4 g of 1,4-diazabicyclo[2.2.2]octane, and 280 g of N,N-dimethylformamide into a closed high-pressure reactor. Under the protection of nitrogen, react at 85 °C for 14 hours;

[0091] A2: After the reaction is completed, remove N,N-dimethylformamide by distillation, and then vacuum dry at 65 °C for 16 hours to obtain the synergist.

[0092] Example 4

[0093] A preparation method of a lithium germanium phosphorus sulfur solid-state battery, and its operation steps are as follows:

[0094] S1 Prepare a sulfur-based solid electrolyte: Stir and mix 22 g of lithium compound, 20 g of germanium compound, 88 g of phosphorus compound, and 0.5 g of synergist evenly, carry out tablet pressing, after high-temperature heat treatment, cool to room temperature, and carry out ball milling to obtain a sulfur-based solid electrolyte;

[0095] S2 Prepare an organic solid electrolyte: Mix 40 g of resin and 20 g of lithium salt evenly to obtain an organic solid electrolyte;

[0096] S3 Prepare a base material: Mix 36 g of sulfur-based solid electrolyte and 30 g of organic solid electrolyte evenly to obtain a base material;

[0097] S4 Preparation of lithium germanium phosphorus sulfur solid electrolyte material: The base material is added to the impregnating solution and impregnated for 24 h, and then dried and solidified under vacuum conditions. The vacuum degree is -0.1 MPa, the temperature is 160 °C, and the time is 4 h to obtain the lithium germanium phosphorus sulfur material for all-solid-state batteries;

[0098] S5 Preparation of the positive electrode precursor solution: 90 g of nickel cobalt manganese ternary positive electrode active material, 20 g of carbon nanotubes, 10 g of polyethylene oxide, and 5 g of lithium bis(trifluoromethanesulfonyl)imide are dissolved in 10 g of dimethylformamide and stirred at 60 °C for 6 h to obtain a uniform positive electrode precursor solution;

[0099] S6 Preparation of the positive electrode and the solid electrolyte: The positive electrode precursor solution is cast onto the solid electrolyte and vacuum dried at 80 °C for 12 h to obtain a positive electrode and a solid electrolyte with close contact;

[0100] S7 Battery assembly: Transfer to an argon glove box and assemble into an all-solid-state battery with a lithium metal sheet as the negative electrode.

[0101] The lithium compound is a mixture of lithium sulfide and lithium oxide, the germanium compound is a mixture of germanium sulfide and germanium oxide, and the phosphorus compound is a mixture of diphosphorus pentasulfide and phosphorus pentoxide.

[0102] The pressure of the tablet pressing is 300 MPa.

[0103] The temperature of the heat treatment is 750 °C and the time is 240 min.

[0104] The ball milling speed is 500 r / min and the time is 72 h.

[0105] The resin is polyethylene glycol acrylate.

[0106] The lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0107] The impregnating solution is N,N-dimethylformamide.

[0108] The preparation method of the synergist is as follows:

[0109] A1: 30 g of tetraarm polyethylene glycol acrylamide, 20 g of 1,1'-diaminocferrocene, 0.7 g of lanthanum acrylate, 5 g of 1,4-diazabicyclo[2.2.2]octane, and 300 g of N,N-dimethylformamide are added to a closed high-pressure reaction kettle and reacted at 90 °C for 15 h under nitrogen protection;

[0110] A2: After the reaction is completed, N,N-dimethylformamide is removed by distillation, and then vacuum dried at 70 °C for 18 h to obtain the synergist.

[0111] Comparative Example 1

[0112] Without adding synergist, other conditions are the same as in Example 1.

[0113] Comparative Example 2

[0114] Without adding tetra-arm polyethylene glycol acrylamide, other conditions are the same as in Example 1.

[0115] Comparative Example 3

[0116] Without adding 1,1'-diaminferrocene, other conditions are the same as in Example 1.

[0117] Ionic conductivity / mS / cm Initial specific capacity / mA·h / g Capacity retention rate / % Example 1 3.3 201.3 90.7 Example 2 3.6 202.8 91.1 Example 3 4.1 208.6 92.5 Example 4 4.5 211.7 92.9 Comparative Example 1 1.8 146.2 76.3 Comparative Example 2 2.5 179.1 84.4 Comparative Example 3 2.7 188.5 86.2

[0118] Through the data analysis of the above examples and comparative examples, the lithium-germanium-phosphorus-sulfur solid-state battery prepared by the present invention has a high ionic conductivity and good cycling performance.

[0119] The above is only the preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with the preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery, and its operation steps are as follows: S1 Prepare a sulfur-based solid electrolyte: Mix 16-22 parts of a lithium compound, 14-20 parts of a germanium compound, 72-88 parts of a phosphorus compound, and 0.1-0.5 part of a synergist evenly by stirring, carry out tabletting, after high-temperature heat treatment, cool to room temperature, and carry out ball milling to obtain a sulfur-based solid electrolyte; S2 Prepare an organic solid electrolyte: Mix 15-40 parts of a resin and 5-20 parts of a lithium salt evenly to obtain an organic solid electrolyte; S3 Prepare a base material: Mix 24-36 parts of a sulfur-based solid electrolyte and 15-30 parts of an organic solid electrolyte evenly to obtain a base material; S4 Prepare a lithium-germanium-phosphorus-sulfur solid electrolyte material: Immerse the base material in an impregnating solution for 12-24 h, and then carry out drying and curing under vacuum conditions, with a vacuum degree of -0.06 to -0.1 MPa, a temperature of 120-160 °C, and a time of 2-4 h, to obtain a lithium-germanium-phosphorus-sulfur material for an all-solid-state battery; S5 Prepare a positive electrode precursor solution: Dissolve 70-90 parts of a nickel-cobalt-manganese ternary positive electrode active material, 10-20 parts of carbon nanotubes, 5-10 parts of polyethylene oxide, and 1-5 parts of lithium bis(trifluoromethanesulfonyl)imide in 5-10 parts of dimethylformamide, and stir at 50-60 °C for 4-6 h to obtain a uniform positive electrode precursor solution; S6 Prepare a positive electrode and a solid electrolyte: Cast the positive electrode precursor solution onto the solid electrolyte, and carry out vacuum drying at 70-80 °C for 8-12 h to obtain a positive electrode and a solid electrolyte with close contact; S7 Assemble the battery: Transfer it to an argon glove box, use a lithium metal sheet as the negative electrode, and assemble it into an all-solid-state battery.

2. The preparation method of a lithium germanium phosphorus sulfur solid-state battery according to claim 1, characterized in that: The lithium compound is a mixture of lithium sulfide and lithium oxide, the germanium compound is a mixture of germanium sulfide and germanium oxide, and the phosphorus compound is a mixture of diphosphorus pentasulfide and phosphorus pentoxide.

3. The preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery according to claim 1, wherein: The pressure of the tabletting is 200-300 MPa.

4. The preparation method of a lithium germanium phosphorus sulfur solid-state battery according to claim 1, characterized in that: The temperature of the heat treatment is 650-750 °C, and the time is 200-240 min.

5. The preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery according to claim 1, wherein: The ball milling speed is 350-500 r / min, and the time is 56-72 h.

6. The preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery according to claim 1, wherein: The resin is one of polyethylene oxide, polyacrylonitrile, and ethylene glycol polyacrylate.

7. The preparation method of a lithium germanium phosphorus sulfur solid-state battery according to claim 1, characterized in that: The lithium salt is one of lithium perchlorate, lithium bis(oxalato)borate, and lithium bis(trifluoromethanesulfonyl)imide.

8. The preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery according to claim 1, wherein: The impregnating solution is one of dimethyl sulfoxide, dimethyl sulfite, and N,N-dimethylformamide.

9. The preparation method of a lithium-germanium-phosphorus-sulfur solid-state battery according to claim 1, characterized in that: The preparation method of the synergist is as follows: A1: By weight, add 20-30 parts of tetraarm polyethylene glycol acrylamide, 10-20 parts of 1,1'-diaminocferrocene, 0.35-0.7 part of lanthanum acrylate, 2-5 parts of 1,4-diazabicyclo[2.2.2]octane, and 200-300 parts of N,N-dimethylformamide into a closed high-pressure reaction kettle, and react at a temperature of 70-90 °C for 10-15 hours under the protection of nitrogen; A2: After the reaction is completed, remove N,N-dimethylformamide by distillation, and then carry out vacuum drying at 60-70 °C for 12-18 hours to obtain a synergist.