Solid-state battery and method of manufacturing the same

Abstract

The application provides a solid-state battery and a preparation method thereof, and belongs to the technical field of secondary batteries.The solid-state battery comprises a solid-state electrolyte, the solid-state electrolyte comprises a sulfide electrolyte and a coating layer, the coating layer is coated on the surface of the sulfide electrolyte, and the coating layer is a single-ion conductor polymer.In the solid-state battery, the solid-state electrolyte assembled therein uses the single-ion conductor polymer to isolate the direct contact of the sulfide electrolyte with air and high-voltage positive active material, avoids the oxidative decomposition of the sulfide electrolyte in the charging and discharging process, improves the storage safety and high-voltage stability of the sulfide electrolyte in the secondary battery, can also maintain the advantages of high ionic conductivity of the sulfide electrolyte, and thus improves the electrochemical stability and ionic conductivity of the sulfide electrolyte, and further improves the charging and discharging efficiency and cycle life of the solid-state battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a solid-state battery and a preparation method thereof. BACKGROUND

[0002] With the rapid development of new energy vehicles and large-scale energy storage technology, the demand for safety, energy density, cycle life and cost of lithium ion secondary batteries is also increasing. The energy density of existing organic liquid lithium ion batteries has reached the theoretical limit; at the same time, the flammable organic liquid electrolyte also faces the risk of leakage and battery thermal runaway. The use of non-flammable solid electrolyte instead of organic liquid electrolyte in all-solid-state batteries can simplify battery design, improve battery safety performance and energy density, and expand the battery temperature range. Solid-state electrolyte is the most core component of all-solid-state battery, and the development of solid-state electrolyte with high ionic conductivity, high safety and high stability is the key to the development of high-performance all-solid-state battery.

[0003] At present, the widely studied solid-state electrolyte includes oxide, sulfide and polymer. Among them, sulfide electrolyte is concerned due to its high ionic conductivity, low Young's modulus and easy large-scale processing. However, the sulfide electrolyte is extremely sensitive to water, and instantaneously releases toxic H2S gas when exposed to a water-containing environment, which has a safety hazard; and the oxidation potential of the sulfide electrolyte is generally lower than 3V, so when the sulfide electrolyte is used with high-voltage positive electrode with a working voltage higher than 3V, the sulfide electrolyte will be oxidized and decomposed during charging and discharging, resulting in cycle failure of the battery.

[0004] Therefore, it is necessary to design a solid-state battery and a preparation method thereof to solve the above problems. SUMMARY

[0005] In view of the above shortcomings of the prior art, the present application provides a solid-state battery and a preparation method thereof to improve the technical problem that the sulfide electrolyte in the prior art has poor electrochemical stability and is difficult to be directly applied to a secondary battery.

[0006] To achieve the above object and other related objects, the present application provides a solid-state battery, which comprises a solid-state electrolyte, the solid-state electrolyte comprises a sulfide electrolyte and a coating layer, the coating layer is coated on the surface of the sulfide electrolyte, and the coating layer is a single-ion conductor polymer; the single-ion conductor monomer polymerized into the coating layer is selected from at least one of the following substances: structure formula (1), structure formula (2), structure formula (3), structure formula (4), structure formula (5) and structure formula (6).

[0007]

[0008] In the formula, R is selected from at least one of H, Cl and CH3.

[0009] In an example of the present application, the thickness of the coating layer is 1-20 nm.

[0010] In an example of the present application, the thickness of the coating layer is 7-12 nm.

[0011] In an example of the present application, the particle size of the sulfide electrolyte is 2-4 μm, and the ionic conductivity of the sulfide electrolyte is greater than 3 mS / cm.

[0012] In an example of the present application, the sulfide electrolyte comprises at least one of Li3PS4, Li7P3S 11 , Li 10 GeP2S 12 , Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5Br and Li 5.5 PS 4.5 Cl 1.5 .

[0013] The present application also provides a preparation method of the solid-state battery of any one of the above examples, which comprises providing a positive electrode sheet, a solid-state electrolyte film and a negative electrode sheet; assembling the positive electrode sheet, the solid-state electrolyte film and the negative electrode sheet into an electric core, and packaging the electric core to obtain a solid-state battery.

[0014] The preparation method of the positive electrode sheet and the solid-state electrolyte in the solid-state electrolyte film comprises:

[0015] providing a sulfide electrolyte and a single-ion conductor monomer;

[0016] mixing the sulfide electrolyte with the single-ion conductor monomer, and initiating in-situ polymerization of the single-ion conductor monomer on the surface of the sulfide electrolyte to form a coating layer, so as to obtain a solid-state electrolyte; the coating layer is a single-ion conductor polymer;

[0017] The single-ion conductor monomer is selected from at least one of the substances of structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6);

[0018]

[0019] In the formula, R is selected from at least one of H, Cl and CH3.

[0020] In an example of the present application, the sulfide electrolyte and the single-ion conductor monomer are provided, which comprises:

[0021] Disperse the sulfide electrolyte into a first solvent to obtain a first solution; wherein the first solvent is a solvent with a polarity index less than 2.5; disperse an initiator and the single-ion conductor monomer into a second solvent to obtain a second solution; wherein the initiator comprises at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dibenzoyl peroxide, ammonium persulfate, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, and benzophenone, and the second solvent is a solvent with a polarity index of 3 to 7.

[0022] In an example of the present application, the mass ratio of the sulfide electrolyte to the first solvent is (15-45):100; and the mass ratio of the single-ion conductor monomer, the initiator, and the second solvent is (0.3-3):(0.01-0.03):100.

[0023] In an example of the present application, the sulfide electrolyte and the single-ion conductor monomer are mixed, and the single-ion conductor monomer is initiated to polymerize in situ on the surface of the sulfide electrolyte to form a coating layer, to obtain a solid-state electrolyte, comprising:

[0024] Mix the first solution and the second solution to obtain a mixed solution; initiate the single-ion conductor monomer in the mixed solution to polymerize in situ on the surface of the sulfide electrolyte to form a coating layer; wherein the initiation mode is light irradiation, heating, or microwave irradiation; and remove the first solvent and the second solvent in the mixed solution to obtain a solid-state electrolyte.

[0025] The present application provides a solid-state battery, in which a solid-state electrolyte assembled in the solid-state battery is coated with a single-ion conductor polymer as a coating layer outside sulfide electrolyte particles. The single-ion conductor polymer coating layer can not only isolate the sulfide electrolyte from direct contact with air and high-voltage positive active materials, but also avoid the oxidation and decomposition of the sulfide electrolyte during charging and discharging, thereby improving the storage safety and high-voltage stability of the sulfide electrolyte in a secondary battery; at the same time, it can also maintain the high ionic conductivity advantage of the sulfide electrolyte, thereby improving the electrochemical stability and ionic conductivity of the sulfide electrolyte, and further improving the charging and discharging efficiency and cycle life of the solid-state battery. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other embodiments according to these drawings without creative labor.

[0027] Figure 1 It is a flowchart of the preparation method of the solid-state electrolyte in an embodiment of the present application.

[0028] Figure 2 A flowchart for step S1 in an embodiment of the present application is shown in the figure.

[0029] Figure 3 A flowchart for step S2 in an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0031] In the present application, it should be noted that the terms "first" and "second" are used only for description and differentiation purposes, and cannot be understood as indicating or implying relative importance.

[0032] Sulfide electrolytes have excellent application prospects as solid-state electrolytes of secondary batteries due to high ionic conductivity, low Young's modulus, and easy large-scale processing. However, the fragile structural stability of sulfide electrolytes limits their application in secondary batteries. For example, sulfide electrolytes are prone to hydrolysis to produce H2S gas, and contact with positive active materials during charging and discharging can cause oxidative decomposition. The inventors have found that to improve the chemical instability of sulfide electrolytes, existing technologies usually coat inorganic materials or organic polymers as coating layers on the surface of sulfide electrolytes. Although the coating layer of the above-mentioned materials can isolate the direct contact of sulfide electrolytes with air and positive active materials, and improve the stability of sulfide electrolytes in secondary batteries, inorganic materials or organic polymers usually do not have ionic conductivity. Coating inorganic materials or organic polymers as a coating layer causes a significant decrease in the ionic conductivity of sulfide electrolytes, affecting the cycle performance of secondary batteries.

[0033] Based on this, the present application provides a solid-state battery, wherein the solid-state electrolyte assembled in the solid-state battery is coated with a single-ion conductor polymer in situ on the surface of sulfide electrolyte particles. The coating layer composed of the single-ion conductor polymer can effectively block the entry of moisture in the air into the surface of the sulfide electrolyte, avoiding the decrease in conductivity and the release of toxic gas caused by the hydrolysis of the sulfide electrolyte. Moreover, the single-ion conductor polymer can also isolate the direct contact of the sulfide electrolyte with the positive active material while ensuring the smooth transport of lithium ions between the sulfide electrolyte and the positive active material, thereby improving the chemical stability of the sulfide electrolyte during charging and discharging, maintaining the high ionic conductivity of the sulfide electrolyte, and further improving the charging and discharging efficiency and cycle life of the solid-state battery.

[0034] The solid-state battery is a solid-state lithium ion secondary battery, which comprises a positive electrode sheet, a negative electrode sheet, and a solid-state electrolyte film, the solid-state electrolyte film being arranged between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet and serve as a lithium ion conductor between the positive electrode sheet and the negative electrode sheet.

[0035] The solid-state electrolyte in the positive electrode sheet and the solid-state electrolyte film or the positive electrode sheet, the solid-state electrolyte film and the negative electrode sheet comprises a sulfide electrolyte and a coating layer, the coating layer being coated on the surface of the sulfide electrolyte, the coating layer being a single-ion conductor polymer, the single-ion conductor polymer having lithium ion conductivity and being capable of allowing lithium ions to migrate and transfer in the coating layer. The single-ion conductor polymer in the coating layer is coated on the surface of the sulfide electrolyte by in-situ polymerization of a single-ion conductor monomer, the single-ion conductor monomer comprising a C=C double bond, a polar C=O / S=O bond and Li + The C=C double bond in the single-ion conductor monomer can produce a chain reaction of free radical polymerization under the action of an initiator, and the long-chain single-ion conductor polymer formed tightly wraps the surface of the sulfide electrolyte particles, and the Li + The lithium ions can migrate under the molecular force between the polar C=O / S=O bond and the Li

[0036] The single-ion conductor monomer is selected from at least one of the following structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6). The structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6) are as follows:

[0037]

[0038] In the formula, R is selected from at least one of H, Cl and CH3.

[0039] In some embodiments, the particle size of the sulfide electrolyte is 2-4 μm, and the ionic conductivity of the sulfide electrolyte is greater than 3 mS / cm.

[0040] In some embodiments, the sulfide electrolyte is selected from Li3PS4, Li7P3S 11 , Li10 GeP2S 12 , Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5Br and Li 5.5 PS 4.5 Cl 1.5 . That is, the sulfide electrolyte can be any one of the above listed kinds, for example, can be Li3PS4, Li7P3S 11 , Li 10 GeP2S 12 , Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5Br or Li 5.5 PS 4.5 Cl 1.5 , optionally, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 ; the sulfide electrolyte can also be a combination of any of the above listed kinds, for example, can be a combination of Li3PS4and Li7P3S 11 , or a combination of Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 , or a combination of Li 10 GeP2S 12 and Li 5.5 PS 4.5 Cl 1.5 , or a combination of Li 10 SnP2S 12 and Li 5.5 PS 4.5 Cl 1.5 , or a combination of Li6PS5Br and Li 5.5 PS 4.5 Cl 1.5 , or a combination of Li 10 SnP2S 12 , Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 . It is to be noted that when the sulfide electrolyte is a combination, the ratio between the components in the combination is not limited, and the components can be mixed in any ratio.

[0041] In some embodiments, the thickness of the coating layer is 1-20 nm, for example, the thickness of the coating layer can be 1 nm, 3 nm, 5 nm, 7 nm, 9 nm, 10 nm, 12 nm, 15 nm, 18 nm or 20 nm. Alternatively, the thickness of the coating layer is 7-12 nm, for example, the thickness of the coating layer can be 7 nm, 8 nm, 9 nm, 10 nm, 11 nm or 12 nm. The thickness of the coating layer in the above range can balance the coating effect and the electrical conductivity of the solid-state electrolyte. If the thickness of the coating layer is too thin, the coating of the sulfide electrolyte particles will be uneven or incomplete, which can easily expose part of the surface of the sulfide electrolyte to the air or directly contact the positive active material, thereby affecting the chemical stability of the solid-state electrolyte in the battery. If the thickness of the coating layer is too thick, the conduction of lithium ions between the sulfide electrolyte particles will be hindered, which will affect the ionic conductivity of the solid-state electrolyte.

[0042] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode material, a positive electrode binder, a positive electrode conductive agent and a solid-state electrolyte. The mass ratio of the positive electrode active material, the solid-state electrolyte, the positive electrode binder and the positive electrode conductive agent can be (50-75):(20-50):(0-3):(1-3). The positive electrode material is, for example, selected from one or more combinations of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium-rich manganese-based oxide (LRMO) and lithium-containing phosphate. The positive electrode binder is, for example, selected from one or more combinations of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, nitrile rubber, hydrogenated nitrile rubber, butadiene-styrene rubber. The positive electrode conductive agent is, for example, selected from one or more combinations of carbon black, ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, porous carbon, etc. In an example, the positive electrode conductive agent includes carbon black and carbon nanofibers, and the mass ratio of carbon black and carbon nanofibers is 1:(0.2-1.5).

[0043] In some embodiments, the negative electrode sheet can be a metal lithium sheet, a metal indium sheet, a lithium-containing alloy sheet (such as a lithium-tin-indium alloy sheet, a lithium-silicon alloy sheet, a lithium-tin alloy sheet, a lithium-aluminum alloy sheet). For example, in an example, the negative electrode sheet is selected from a metal lithium sheet.

[0044] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector, the negative electrode active material layer including a negative electrode material, a solid-state electrolyte, a negative electrode binder, and a negative electrode conductive agent. The mass ratio of the negative electrode active material, the solid-state electrolyte, the negative electrode binder, and the negative electrode conductive agent can be (50-75):(20-50):(0-3):(1-3). The negative electrode active material can be selected from one or more of tin, artificial graphite (single-crystal graphite, polycrystal graphite, pyrolytic graphite, graphite fiber, etc.), natural graphite (block graphite, flake graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon, or organic silicon), silicon oxide compounds, silicon carbon compounds, and nano metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles). The negative electrode conductive agent can be selected from one or more of carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers. The negative electrode binder can be selected from one or more of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), and styrene butadiene rubber (SBR).

[0045] In another aspect, the present application also provides a method for preparing a solid-state battery, the method including: providing a positive electrode tab, a solid-state electrolyte film, and a negative electrode tab; assembling the positive electrode tab, the solid-state electrolyte film, and the negative electrode tab into an electric core, and packaging the electric core to obtain a solid-state battery.

[0046] It should be noted that the positive electrode tab, the negative electrode tab, the solid-state electrolyte film, and the assembly process of the secondary battery can be prepared using conventional methods in the art.

[0047] In some embodiments, the positive electrode tab is prepared as follows: the positive electrode material, the positive electrode binder, the positive electrode conductive agent, and the solid-state electrolyte are mixed in a mass ratio of (50-75):(20-50):(0-3):(1-3), deionized water is added, the solid content of the slurry is adjusted to 55%, and then the mixture is fully stirred under vacuum to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then the positive electrode current collector aluminum foil is transferred to an oven for drying after being dried at room temperature, and then the positive electrode tab is obtained through cold pressing and slitting. The positive electrode material is selected from one or more combinations of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium-rich manganese-based oxide (LRMO), and lithium-containing phosphate. The positive electrode binder is selected from one or more combinations of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, nitrile rubber, hydrogenated nitrile rubber, and styrene-butadiene rubber. The positive electrode conductive agent is selected from one or more combinations of carbon black, ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, and porous carbon.

[0048] In some embodiments, the negative electrode tab is prepared as follows: the negative electrode material, the solid-state electrolyte, the negative electrode binder, and the negative electrode conductive agent are mixed in a mass ratio of (50-75):(20-50):(0-3):(1-3), deionized water is added, the solid content of the slurry is adjusted to 55%, and then the mixture is fully stirred under vacuum to obtain a negative electrode slurry; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil of 8 μm; and then the negative electrode tab is obtained through cold pressing, slitting, and other processes after being dried at room temperature and then being transferred to an oven for drying. The negative electrode active material is selected from one or more of tin, artificial graphite (single-crystal graphite, polycrystalline graphite, pyrolytic graphite, graphite fibers, etc.), natural graphite (block graphite, flaky graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon, or organic silicon), silicon oxide compounds, silicon carbon compounds, and nano metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles). The negative electrode conductive agent is selected from one or any proportionally mixed combination of two or more of carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers. The negative electrode binder is selected from any one or any proportionally mixed combination of several of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), and styrene-butadiene rubber (SBR).

[0049] In other embodiments, a metal lithium sheet, a metal indium sheet, or a lithium-containing alloy sheet (such as a lithium-tin-indium alloy sheet, a lithium-silicon alloy sheet, a lithium-tin alloy sheet, or a lithium-aluminum alloy sheet) is used as the negative electrode tab.

[0050] In some embodiments, the preparation process of the solid-state electrolyte film is as follows: the solid-state electrolyte and the adhesive are mixed in a mass ratio of (90-99.5):(0.5-10), then added into a low-polarity solvent, and fully stirred to obtain a slurry; the slurry is coated on a substrate, the solvent in the coating layer is dried by heating, and the coating layer is peeled off from the substrate to obtain the solid-state electrolyte film. The adhesive is selected from any one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and ethylene-tetrafluoroethylene copolymer, or a composition of several mixed in any ratio.

[0051] The assembly method of the secondary battery is described as follows: one side of the solid-state electrolyte film is integrated with a positive electrode sheet, for example, the solid-state electrolyte film is placed on the positive active material layer of the positive electrode sheet, and the solid-state electrolyte film and the positive electrode sheet are pressed into one body at a pressure of 300 MPa; then the other side of the solid-state electrolyte film is integrated with a negative electrode sheet, for example, the negative electrode sheet is placed on the other side of the solid-state electrolyte film, so that the negative active material layer of the negative electrode sheet contacts the solid-state electrolyte film, and the negative electrode sheet, the solid-state electrolyte film and the positive electrode sheet are pressed into one body at a pressure of 300 MPa; the pressed battery is sealed and packaged in a vacuum or inert atmosphere to obtain a solid-state lithium ion battery.

[0052] As shown in Figure 1 The preparation method of the solid-state electrolyte in the above solid-state battery includes the following steps:

[0053] S1, providing a sulfide electrolyte and a single-ion conductor monomer;

[0054] S2, mixing the sulfide electrolyte and the single-ion conductor monomer, and initiating in-situ polymerization of the single-ion conductor monomer on the surface of the sulfide electrolyte to form a coating layer, to obtain a solid-state electrolyte;

[0055] The coating layer is a single-ion conductor polymer formed by in-situ polymerization of the single-ion conductor monomer on the surface of the sulfide electrolyte particle, and the single-ion conductor monomer used in step S1 is selected from at least one of the substances of structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6); structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6) are as follows:

[0056]

[0057] In the formula, R is selected from at least one of H, Cl and CH3.

[0058] As shown in Figure 2 In some embodiments, step S1 includes the following steps:

[0059] S11, dispersing the sulfide electrolyte into a first solvent to obtain a first solution;

[0060] S12, dispersing an initiator and a single-ion conductor monomer into a second solvent to obtain a second solution.

[0061] In some embodiments, in step S11, the sulfide electrolyte is uniformly mixed with the first solvent at a mass ratio of (15-45): 100 to obtain the first solution;

[0062] wherein the sulfide electrolyte is selected from one or more of Li3PS4, Li7P3S 11 , Li 10 GeP2S 12 , Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5Br and Li 5.5 PS 4.5 Cl 1.5 . Optionally, the sulfide electrolyte is selected from Li 5.5 PS 4.5 Cl 1.5 . The particle size of the sulfide electrolyte selected in step S11 is 2-4 pm, and the ionic conductivity is greater than 3 mS / cm.

[0063] The first solvent is selected as a low-polarity solvent with a polarity index less than 2.5, for example, the first solvent is selected from at least one of toluene, xylene, n-pentane, hexane and cyclohexane. Optionally, the first solvent is selected as xylene.

[0064] In some embodiments, in step S12, the single-ion conductor monomer, the initiator and the second solvent are uniformly mixed at a mass ratio of (0.3-3):(0.01-0.03): 100 to obtain the second solution.

[0065] wherein the initiator is used to promote the polymerization of the single-ion conductor monomer under initiation conditions, and the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dibenzoyl peroxide, ammonium persulfate, 2,4,6-trimethylbenzoyl diphenyl phosphate and benzophenone. Optionally, the initiator is selected as azobisisobutyronitrile.

[0066] The second solvent is selected as a medium-polarity solvent with a polarity index of 3-7, for example, the second solvent is selected from at least one of ethyl acetate, butyl butyrate, benzyl acetate, acetonitrile and dichloromethane. Optionally, the second solvent is selected as butyl butyrate.

[0067] In some embodiments, the dispersion treatment in steps S11 and S12 can be a combination of one or more of ultrasonic, stirring and ball milling.

[0068] As shown in FIG. 1, in some embodiments, step S2 comprises the following steps: Figure 3

[0069] S31, mixing the first solution and the second solution to obtain a mixed solution;

[0070] S32, initiating in-situ polymerization of the single-ion conductor monomers in the mixed solution on the surface of the sulfide electrolyte to form a coating layer; wherein the initiation method is light irradiation, heating or microwave irradiation;

[0071] S33, removing the first solvent and the second solvent in the mixed solution to obtain a solid-state electrolyte.

[0072] In step S31, the thickness of the coating layer formed on the surface of the sulfide electrolyte can be controlled by adjusting the mixing ratio of the first solution and the second solution. For example, in some embodiments, the first solution and the second solution are mixed at a mass ratio of (50-100): 100 to control the thickness of the coating layer formed on the surface of the sulfide electrolyte to be 1-20 nm.

[0073] In step S31, after mixing the first solution and the second solution, the mixture is stirred at room temperature for 30-60 min to ensure uniform mixing of the first solution and the second solution.

[0074] In step S32, the initiation method is used to promote in-situ polymerization of the single-ion conductor monomers in the mixed solution on the surface of the sulfide electrolyte under the action of the initiator to form a coating layer. The initiation method can be light irradiation, heating or microwave irradiation. For example, in some embodiments, the mixed solution is placed under 100W ultraviolet light irradiation for 30 min to 2 h to promote in-situ polymerization of the single-ion conductor monomers in the mixed solution on the surface of the sulfide electrolyte; in other embodiments, the mixed solution is placed under microwave irradiation for 2 to 4 hours to promote in-situ polymerization of the single-ion conductor monomers in the mixed solution on the surface of the sulfide electrolyte; in yet other embodiments, the mixed solution is heated at a temperature of 60°C for 30 min to 2 h to promote in-situ polymerization of the single-ion conductor monomers in the mixed solution on the surface of the sulfide electrolyte.

[0075] In some embodiments, in step S33, the mixed solution is subjected to centrifugation or suction filtration, and then the mixed solution is placed in a vacuum dryer at a temperature of 45°C to 60°C for 2 to 8 hours to remove the first solvent and the second solvent in the mixed solution, thereby obtaining a solid-state electrolyte.

[0076] The technical solutions of the present application are described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art.​

[0077] Example 1

[0078] This example provides a solid-state electrolyte, which comprises a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , and the coating layer is a single-ion conductor polymer formed by polymerization of a single-ion conductor monomer of structural formula (1). The preparation method of the solid-state electrolyte is as follows:

[0079] S1, in an argon atmosphere glove box, 2.5 g of sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 and 10 g of the first solvent dimethylbenzene were placed in a 50 ml glass sample bottle, mixed and stirred at room temperature for 60 minutes to obtain a first solution; 0.01 g of a single-ion conductor monomer of structural formula (1), 0.001 g of an initiator azobisisobutyronitrile, and 10 g of the second solvent butyl butyrate were placed in another 50 ml glass sample bottle, stirred at 45°C for 60 minutes to obtain a second solution, and the R group in structural formula (1) is H;

[0080] S2, the first solution and the second solution were mixed and stirred at room temperature for 60 minutes to obtain a uniform mixed solution; then the mixed solution was heated and stirred at 60°C for 30 minutes to allow the single-ion conductor monomer in the mixed solution to polymerize in situ on the surface of the sulfide electrolyte to form a single-ion conductor polymer coating layer under the catalysis of the initiator; after centrifugation of the mixed solution, vacuum drying was carried out at a temperature of 45°C to 60°C for 2 to 8 hours to remove the first solvent and the second solvent in the mixed solution, thereby obtaining a solid-state electrolyte.

[0081] Example 2

[0082] This example prepares a solid-state electrolyte of the same system as Example 1, which comprises a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , and the coating layer is a single-ion conductor polymer formed by polymerization of a single-ion conductor monomer of structural formula (1). The difference between this example and Example 1 is that in step S1, 0.03 g of a single-ion conductor monomer of structural formula (1), 0.001 g of an initiator azobisisobutyronitrile, and 10 g of the second solvent butyl butyrate were mixed in another 50 ml glass sample bottle.

[0083] Example 3

[0084] A solid-state electrolyte of the same system as that of Example 1 was prepared, the solid-state electrolyte including a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, the sulfide electrolyte being Li 5.5 PS 4.5 Cl 1.5 , and the coating layer being a single-ion conductor polymer formed by polymerization of a single-ion conductor monomer of structural formula (1). The difference between this example and Example 1 is that in step S1, 0.06 g of the single-ion conductor monomer of structural formula (1), 0.004 g of the initiator azobisisobutyronitrile, and 10 g of the second solvent butyl butyrate were mixed in another 50-ml glass sample bottle.

[0085] Example 4

[0086] A solid-state electrolyte of the same system as that of Example 1 was prepared, the solid-state electrolyte including a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, the sulfide electrolyte being Li 5.5 PS 4.5 Cl 1.5 , and the coating layer being a single-ion conductor polymer formed by polymerization of a single-ion conductor monomer of structural formula (1). The difference between this example and Example 1 is that in step S1, 0.1 g of the single-ion conductor monomer of structural formula (1), 0.006 g of the initiator azobisisobutyronitrile, and 10 g of the second solvent butyl butyrate were mixed in another 50-ml glass sample bottle.

[0087] Example 5

[0088] A solid-state electrolyte of the same system as that of Example 1 was prepared, the solid-state electrolyte including a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, the sulfide electrolyte being Li 5.5 PS 4.5 Cl 1.5 , and the coating layer being a single-ion conductor polymer formed by polymerization of a single-ion conductor monomer of structural formula (1). The difference between this example and Example 1 is that in step S1, 0.3 g of the single-ion conductor monomer of structural formula (1), 0.02 g of the initiator azobisisobutyronitrile, and 10 g of the second solvent butyl butyrate were mixed in another 50-ml glass sample bottle.

[0089] Example 6

[0090] A solid-state electrolyte of the same system as that of Example 3 was prepared, the solid-state electrolyte including a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, the sulfide electrolyte being Li 5.5 PS 4.5 Cl 1.5, the coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (1). The difference between this embodiment and embodiment 3 is that, in step S1, 4.5 g of sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 and 10 g of the first solvent dimethylbenzene are mixed in a 50 ml glass sample bottle.

[0091] Example 7

[0092] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , and the coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (1). The difference between this embodiment and embodiment 3 is that, in step S2, the initiator used is dibenzoyl peroxide, and the mixed solution is irradiated under ultraviolet light with a power of 100 W for 30 minutes to initiate the single-ion conductor monomer in the mixed solution to form a coating layer on the surface of the sulfide electrolyte.

[0093] Example 8

[0094] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li6PS5Cl, and the coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (1). The difference between this embodiment and embodiment 3 is that, in step S1, the sulfide electrolyte is selected as Li6PS5Cl.

[0095] Example 9

[0096] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , and the coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (1). The difference between this embodiment and embodiment 3 is that, in step S1, the single-ion conductor monomer of structural formula (2) is selected, and the R group in structural formula (2) is H.

[0097] Example 10

[0098] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li5.5 PS 4.5 Cl 1.5 The coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (3). The difference between this embodiment and embodiment 3 is that in step S1, the single-ion conductor monomer of structural formula (3) is selected, and the R group in structural formula (3) is H.

[0099] Example 11

[0100] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, and the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 The coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (4). The difference between this embodiment and embodiment 3 is that in step S1, the single-ion conductor monomer of structural formula (4) is selected, and the R group in structural formula (4) is H.

[0101] Example 12

[0102] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, and the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 The coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (5). The difference between this embodiment and embodiment 3 is that in step S1, the single-ion conductor monomer of structural formula (5) is selected, and the R group in structural formula (5) is H.

[0103] Example 13

[0104] This embodiment prepares a solid-state electrolyte of the same system as embodiment 3, which includes a sulfide electrolyte and a coating layer coated on the outside of the sulfide electrolyte particles, and the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 The coating layer is a single-ion conductor polymer formed by polymerization of the single-ion conductor monomer of structural formula (6). The difference between this embodiment and embodiment 3 is that in step S1, the single-ion conductor monomer of structural formula (6) is selected, and the R group in structural formula (6) is H.

[0105] Comparative Example 1

[0106] This comparative example provides a solid-state electrolyte Li 5.5 PS 4.5 Cl 1.5 .

[0107] Comparative Example 2

[0108] This comparative example prepared a solid-state electrolyte of the same system as Example 3, which includes a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , and the coating layer is a single-ion conductor polymer formed by polymerization of a single-ion conductor monomer of structural formula (1). The difference between this comparative example and Example 3 is that in step S1, 0.8 g of a single-ion conductor monomer of structural formula (1), 0.02 g of an initiator azobisisobutyronitrile, and 10 g of a second solvent butyl butyrate are mixed in another 50 ml glass sample bottle.

[0109] Comparative Example 3

[0110] Comparative Example 3 provides a solid-state electrolyte with ordinary polymer coating, which includes a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte particles, the sulfide electrolyte is Li6PS5Cl, and the coating layer is a polymer of methyl methacrylate. The preparation method of the solid-state electrolyte is as follows:

[0111] S1, in an argon atmosphere glove box, 2.5 g of sulfide electrolyte Li6PS5Cl and 10 g of a first solvent cyclohexane are weighed into a 50 ml glass sample bottle, mixed and stirred at room temperature for 60 minutes to obtain a first solution; 0.06 g of methyl methacrylate, 0.004 g of an initiator azobisisoheptyl nitrile, and 10 g of a second solvent benzyl acetate are weighed into another 50 ml glass sample bottle, and stirred at 45°C for 60 minutes to obtain a second solution;

[0112] S2, the first solution and the second solution are mixed and stirred at room temperature for 60 minutes to obtain a uniform mixed solution; then the mixed solution is heated and stirred at 60°C for 30 minutes to allow the methyl methacrylate monomer in the mixed solution to polymerize in situ on the surface of the sulfide electrolyte under the catalysis of the initiator to form a polymer coating layer; after centrifugation of the mixed solution, vacuum drying at a temperature of 45°C to 60°C for 2 to 8 hours to remove the first solvent and the second solvent in the mixed solution, thereby obtaining a solid-state electrolyte.

[0113] To further verify the efficacy of the present application, first, the ionic conductivity of the solid-state electrolytes prepared in Examples 1 to 13 and Comparative Examples 1 to 3 and the conductivity stability when stored in air were tested to verify that the solid-state electrolyte improves the structural stability of the sulfide electrolyte when stored in air while maintaining the high ionic conductivity of the sulfide electrolyte. The test results are shown in Table 1.

[0114] Ion conductivity test: 0.1 g of the solid-state electrolyte powder prepared in the examples and the comparative examples was weighed, and the solid-state electrolyte powder was pressed into an electrolyte ceramic sheet at a pressure of 200 MPa; a stainless steel current collector was attached to both sides of the electrolyte ceramic sheet, and the electrolyte ceramic sheet was assembled into a mold cell under a pressure of 200 MPa; the alternating current impedance spectrum of the mold cell was tested using an electrochemical workstation to obtain the impedance of the electrolyte ceramic sheet, and then the ion conductivity σ of the solid-state electrolyte at room temperature was calculated based on the formula σ = L / RS; wherein L is the thickness of the electrolyte ceramic sheet (unit: cm), R is the impedance of the electrolyte ceramic sheet (unit: Ω), and S is the contact area (unit: cm 2 ).

[0115] Conductive stability test in air: 0.2 g of the solid-state electrolyte powder prepared in the examples and the comparative examples was weighed, and the solid-state electrolyte powder was pressed into an electrolyte ceramic sheet at a pressure of 200 MPa; the impedance of the electrolyte ceramic sheet was tested using an electrochemical workstation to obtain the initial ion conductivity of the solid-state electrolyte; the electrolyte ceramic sheet was placed in a 5 mL open glass bottle, and then the glass bottle was placed in a reaction box with a specific humid air flow, the relative humidity of the humid air was 10%, the gas flow was 100 ml / min, and the impedance of the electrolyte ceramic sheet was tested again after being placed at room temperature for 12 h to obtain the ion conductivity of the solid-state electrolyte after being exposed to humid air; and the ion conductivities of the solid-state electrolyte before and after exposure were compared to obtain the retention rate of the ion conductivity of the solid-state electrolyte.

[0116] Then, the solid-state electrolytes prepared in Examples 1 to 13 and Comparative Examples 1 to 3 were assembled into solid-state batteries, and the electrochemical stability of the solid-state electrolytes prepared in Examples 1 to 13 and Comparative Examples 1 to 3 in the solid-state batteries was tested, and the test results are shown in Table 2.

[0117] The solid-state battery preparation process is as follows: 0.2 g of solid-state electrolyte powder is weighed and placed in a solid-state battery mold, and is pressed at a pressure of 200 MPa for 5 minutes to obtain a solid-state electrolyte sheet. The positive electrode material, solid-state electrolyte, positive electrode adhesive nitrile rubber, positive electrode conductive agent Super P and CNT are dispersed in xylene in a mass ratio of 70:25:3:1:1, and the amount of xylene added is adjusted to control the solid content of the slurry at about 55%; the slurry is coated on the positive electrode current collector aluminum foil by doctor blade method, and the coated positive electrode sheet is placed in a blast drying oven at 100°C for 2 hours, and then rolled and compacted at a pressure of 95 MPa at a temperature of 60°C to obtain a positive electrode sheet. The solid-state electrolyte sheet is integrated on the side of the positive electrode active material layer of the positive electrode sheet, and is pressed at a pressure of 100 MPa to integrate; the lithium-indium alloy sheet is used as the negative electrode sheet, and the negative electrode sheet is integrated on the side of the solid-state electrolyte sheet away from the positive electrode sheet, and is pressed at a pressure of 100 MPa to integrate, to obtain a battery core; the battery core is heat-sealed and packaged, and then subjected to processes such as standing, hot and cold pressing, formation, clamping and capacity distribution to obtain a solid-state battery.

[0118] First coulomb efficiency test of the solid-state battery: at 25°C room temperature, the solid-state battery is subjected to first cycle charge-discharge test at a test voltage interval of 2.5V (discharge cut-off voltage) to 4.2V (charge cut-off voltage) with a charge-discharge current ratio of 0.1C / 0.1C, and the first charge capacity and the first discharge capacity of the battery are recorded. The first discharge capacity divided by the mass of the negative electrode can obtain the first discharge gram capacity, and the first coulomb efficiency can be obtained.

[0119] Cycle performance test of the solid-state battery: at 25°C room temperature, the solid-state battery is subjected to 3 cycles of charge-discharge at a test voltage interval of 2.5V (discharge cut-off voltage) to 4.2V (charge cut-off voltage) with a charge-discharge current ratio of 0.2C / 0.2C, 0.5C / 0.5C, 1C / 1C and 2C / 2C, respectively; then the solid-state battery is subjected to charge-discharge cycle with a charge-discharge current ratio of 0.5C / 0.5C, and the test is stopped when the discharge capacity of the solid-state battery reaches 80% of the first cycle discharge capacity at 0.5C rate, and the number of cycles at room temperature is recorded.

[0120] Table 1: Ion conductivity and air storage stability test results of solid-state electrolyte prepared in Examples 1 to 13 and Comparative Examples 1 to 3

[0121]

[0122] Table 2: Battery performance test results of solid-state electrolyte prepared in Examples 1 to 13 and Comparative Examples 1 to 3

[0123]

[0124]

[0125] From the test results of Examples 1 to 13 and Comparative Example 1, it can be seen that the sulfide electrolyte coated with the single-ion conductor polymer has both good electrochemical stability and high lithium ion conductivity, and the solid-state battery assembled therefrom also has better cycle performance.

[0126] From the test results of Example 3 and Comparative Example 1, it can be seen that compared with the sulfide electrolyte without coating layer, the ion conductivity of the sulfide electrolyte coated with the single-ion conductor polymer only has a slight decrease, and the decrease in ion conductivity after exposure in humid air is significantly reduced, and the retention rate of ion conductivity in humid air is significantly improved, which proves that the single-ion conductor polymer coating layer can effectively block the erosion of moisture to the sulfide electrolyte, improve the air stability and use safety of the sulfide electrolyte. Moreover, the initial coulombic efficiency and cycle capacity retention rate of the solid-state battery assembled with the coated sulfide electrolyte are also significantly improved, which proves that the solid-state electrolyte in the embodiment also has excellent electrochemical stability when the battery is used.

[0127] From the test results of Example 8 and Comparative Example 3, it can be seen that compared with the sulfide electrolyte coated with the ordinary polymer, the ion conductivity of the sulfide electrolyte coated with the single-ion conductor polymer is significantly improved, and the initial coulombic efficiency and cycle capacity retention rate of the solid-state battery assembled with the single-ion conductor polymer coated sulfide electrolyte are also improved. This is because the ion conductor polymer coating layer not only blocks the direct contact between the sulfide electrolyte particles and the positive active material particles, but also conducts ions quickly between the sulfide electrolyte particles and between the sulfide electrolyte particles and the positive active material particles, thereby reducing the charge transfer impedance of the interface.

[0128] Further, from the test results of Examples 1 to 6 and Comparative Example 2, it can be seen that when the thickness of the coating layer is optimized within an appropriate range

[0129] From the test results of Examples 1 to 6 and Comparative Example 2, it can be seen that as the thickness of the coating layer increases, the storage stability of the solid-state electrolyte in air is significantly improved, but the loss of sulfide electrolyte content and ion conductivity also increases accordingly. For example, in Comparative Example 3, when the thickness of the coating layer is greater than 20 nm, the ion conductivity of the solid-state electrolyte is only 23% of that of the uncoated sulfide electrolyte. Therefore, it is necessary to control the thickness of the coating layer to be less than 20 nm to achieve the balance of air stability and high ion conductivity.

[0130] In summary, the present application provides a solid-state electrolyte, a secondary battery and a preparation method of the solid-state electrolyte, which coats a single-ion conductor polymer as a coating layer outside the sulfide electrolyte particles. The single-ion conductor polymer coating layer can not only isolate the sulfide electrolyte from direct contact with air and high-voltage positive active material, avoid the oxidation and decomposition of the sulfide electrolyte in the charging and discharging process, and improve the storage safety and high-voltage stability of the sulfide electrolyte in the secondary battery, but also can maintain the high ionic conductivity of the sulfide electrolyte, so as to improve the electrochemical stability and ionic conductivity of the sulfide electrolyte.

[0131] The above embodiments only illustrate the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A solid-state battery, characterized by, The solid-state electrolyte comprises a sulfide electrolyte and a coating layer coated on the surface of the sulfide electrolyte, and the coating layer is a single-ion conductor polymer; the single-ion conductor monomer of the coating layer is selected from at least one of substances of structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6). In the formula, R is selected from at least one of H, Cl and CH3.

2. The solid-state battery of claim 1, wherein, The thickness of the coating layer is 1-20 nm.

3. The solid-state battery of claim 2, wherein, The thickness of the coating layer is 7-12 nm.

4. The solid-state battery of claim 1, wherein, The particle size of the sulfide electrolyte is 2-4 μm, and the ionic conductivity of the sulfide electrolyte is greater than 3 mS / cm.

5. The solid-state battery of claim 1, wherein, The sulfide electrolyte comprises at least one of Li3PS4, Li7P3S 11 10 GeP2S 12 10 SnP2S 12 Li6PS5Cl, Li6PS5Br and Li 5.5 PS 4.5 Cl 1.5 .​​ 6. A method of producing a solid-state battery, characterized by, The method comprises: Providing a positive electrode sheet, a solid-state electrolyte film and a negative electrode sheet; Assembling the positive electrode sheet, the solid-state electrolyte film and the negative electrode sheet into an electric core, and packaging the electric core to obtain a solid-state battery; The preparation method of the solid-state electrolyte in the positive electrode sheet and the solid-state electrolyte film comprises: Providing a sulfide electrolyte and a single-ion conductor monomer; Mixing the sulfide electrolyte and the single-ion conductor monomer, and initiating in-situ polymerization of the single-ion conductor monomer on the surface of the sulfide electrolyte to form a coating layer, so as to obtain a solid-state electrolyte; the coating layer is a single-ion conductor polymer; The single-ion conductor monomer is selected from at least one of substances of structural formula (1), structural formula (2), structural formula (3), structural formula (4), structural formula (5) and structural formula (6). In the formula, R is selected from at least one of H, Cl and CH3.

7. The production method according to claim 6, characterized by, Providing a sulfide electrolyte and a single-ion conductor monomer, comprising: Dispersing the sulfide electrolyte into a first solvent to obtain a first solution; wherein the first solvent is a solvent with a polarity index less than 2.5; Dispersing an initiator and the single-ion conductor monomer into a second solvent to obtain a second solution; wherein the initiator comprises at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dibenzoyl peroxide, ammonium persulfate, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, and benzophenone, and the second solvent is a solvent with a polarity index of 3-7.

8. The production method according to claim 7, characterized by, The mass ratio of the sulfide electrolyte to the first solvent is (15-45):

100.

9. The preparation method according to claim 7, characterized in that The mass ratio of the single-ion conductor monomer, the initiator and the second solvent is (0.3-3):(0.01-0.03):

100.

10. The production method according to any one of claims 7 to 9, characterized in that, Mixing the sulfide electrolyte and the single-ion conductor monomer, and initiating in-situ polymerization of the single-ion conductor monomer on the surface of the sulfide electrolyte to form a coating layer, so as to obtain a solid-state electrolyte, comprising: Mixing the first solution and the second solution to obtain a mixed solution; Initiating in-situ polymerization of the single-ion conductor monomer in the mixed solution on the surface of the sulfide electrolyte to form a coating layer; wherein the initiation mode is light irradiation, heating or microwave irradiation; Removing the first solvent and the second solvent in the mixed solution to obtain a solid-state electrolyte.

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