Modified sulfur-based solid electrolyte and preparation method thereof, solid-state lithium-ion battery

Abstract

The present invention provides a modified sulfur-based solid electrolyte and a preparation method thereof, and a solid-state lithium-ion battery. The modified sulfur-based solid electrolyte includes a sulfur-based solid electrolyte body and a coating layer attached to the surface of the sulfur-based solid electrolyte body, wherein the coating layer includes a modified polyacrylamide gel, the sulfur-based solid electrolyte body includes an aggregate of sulfur-based solid electrolyte particles, the sulfur-based solid electrolyte particles include sulfur-based solid electrolyte powder and a coating layer coated on the surface of the sulfur-based solid electrolyte powder, and the coating layer includes a Li2O‑2B2O3 coating layer. The Li2O‑2B2O3 coating layer helps to suppress the chemical reaction between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, greatly improving the interface compatibility between the sulfur-based solid electrolyte powder and the lithium metal negative electrode. At the same time, it effectively alleviates the interfacial stress between the solid electrolyte powder and the lithium metal negative electrode, thereby reducing the interface resistance and improving the electrical performance of the solid-state lithium-ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and in particular to a modified sulfur-based solid electrolyte and a preparation method thereof, and a solid-state lithium-ion battery. Background Art

[0002] Lithium-ion batteries have become a necessity in our lives, playing a vital role in all aspects of daily life. Traditional liquid lithium-ion batteries primarily utilize solvents and lithium salts, using organic ester or organic ether electrolytes to dissolve the lithium salts and adding film-forming protective agents to achieve safe, long-term lithium-ion battery cycling. However, these organic solvents are volatile and flammable, posing significant safety risks. Furthermore, organic electrolytes can easily catch fire when a battery short circuits or internal heat accumulates, leading to serious safety incidents. Furthermore, the addition of organic electrolytes increases the overall proportion of inactive substances, reducing the overall specific energy of the lithium-ion battery.

[0003] Unlike organic liquid electrolytes, inorganic solid electrolytes are non-flammable and have a higher starting temperature for thermal runaway. Therefore, inorganic solid electrolytes exhibit high chemical stability, high ionic conductivity and safety, and have attracted much attention. Using non-flammable solid electrolytes instead of flammable liquid electrolytes as a carrier for lithium ion transmission can greatly improve the safety performance of batteries. In addition, solid electrolyte materials generally have a wide electrochemical window and are suitable for high-voltage electrode materials. Among them, sulfur-based solid electrolytes in inorganic solid electrolytes are currently reported to have an ionic conductivity comparable to that of liquid electrolytes at room temperature. The S element in sulfur-based solid electrolytes basically exists in the form of non-bridging sulfur, which gives it higher ionic conductivity. It is considered to be the solid electrolyte most likely to be industrially produced in the future.

[0004] In addition, since the binding force between S and Li is relatively weak, it is conducive to the continuous complexation and dissociation of lithium ions for transmission during the lithium ion transmission process, thereby improving the ion conductivity of the sulfur-based solid electrolyte. And by controlling the preparation conditions and element synthesis, a sulfur-based solid electrolyte with a fast ion conductor structure of lithium ion transmission channels can be obtained, thereby greatly improving its ion conductivity. Therefore, the conductivity of sulfur-based solid electrolytes is relatively high compared to other solid electrolytes such as oxides. However, the interface impedance of sulfur-based solid electrolytes is large. When assembled into a solid-state lithium metal battery, as the cycle deepens, tiny cracks will appear at the interface, leading to the failure of the solid-state lithium metal battery. Specifically, the analysis is as follows:

[0005] (1) Since solid electrolytes do not have the fluidity of liquid electrolytes, the solid-solid contact area between the solid electrolyte and the electrode material is small, resulting in a large solid-solid interface impedance between the electrode material and the electrolyte material. (2) Interface stability issues, which mainly include the chemical stability and electrochemical stability of the interface between the solid electrolyte and the electrode. The solid electrolyte material and the electrode material react in contact or at a certain potential to generate interface substances that are not conducive to lithium ion conduction, or element diffusion occurs at the interface during the cycle, causing the interface resistance to increase, thereby causing the performance of the all-solid-state battery to decline. (3) Interface stress issues, due to the different volume expansion coefficients of the solid electrolyte and the electrode material, as the battery cycle deepens during the charge and discharge process, the volume expansion and contraction caused by the lithium insertion and delithiation process of the electrode material causes the interface contact between the electrode material and the solid electrolyte to deteriorate, thereby causing the battery performance to decline. Summary of the Invention

[0006] The main purpose of the present invention is to provide a modified sulfur-based solid electrolyte and its preparation method, and a solid-state lithium-ion battery, so as to solve the problems in the prior art of sulfur-based solid electrolytes such as large interface impedance, low ion transfer efficiency, poor interface stability and large interface stress, which lead to poor electrical performance of solid-state lithium metal batteries.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a modified sulfur-based solid electrolyte is provided, which comprises a sulfur-based solid electrolyte body and a coating layer attached to the surface of the sulfur-based solid electrolyte body, wherein the coating layer comprises a modified polyacrylamide gel, the sulfur-based solid electrolyte body comprises an aggregate of sulfur-based solid electrolyte particles, the sulfur-based solid electrolyte particles comprise sulfur-based solid electrolyte powder and a coating layer coated on the surface of the sulfur-based solid electrolyte powder, and the coating layer comprises a Li2O-2B2O3 coating layer.

[0008] Furthermore, the thickness of the coating layer is 2-4 μm, and the mass ratio of the coating layer to the sulfur-based solid electrolyte body is preferably 2-4:96-98.

[0009] Furthermore, the sulfur-based solid electrolyte particles are selected from (1+x)Li2S·xP2S5, Li4P2S6, Li3PS4, Li7P3S 11 、Li 6-y PS 5-y X 1+y He Li 11-z M 2-z P 1+z S 12Any one or more of, wherein 0<x<1, 0≤y≤0.6, 0.5≤z≤1.5, M is selected from any one or more of Ge, Sn, and Si, and X is a halogen, preferably X is selected from any one or more of Cl, Br, and I.

[0010] According to one aspect of the present invention, a method for preparing the aforementioned modified sulfur-based solid electrolyte is provided, the preparation method comprising: step S1, mixing a sulfur-based solid electrolyte precursor, Li2O-2B2O3 and a solvent to obtain a mixture; step S2, ball milling, drying and sintering the mixture in sequence to obtain sulfur-based solid electrolyte particles; step S3, molding the sulfur-based solid electrolyte particles to obtain a sulfur-based solid electrolyte body; and step S4, coating the surface of the sulfur-based solid electrolyte body with modified polyacrylamide gel and then baking to obtain a modified sulfur-based solid electrolyte.

[0011] Furthermore, in the above step S2, the D50 particle size of the sulfur-based solid electrolyte particles is 0.370-0.520 μm; the ball milling speed is preferably 300-350 r / min, and the ball milling time is preferably 4-6 h; the drying temperature is preferably 90-100° C., and the drying time is preferably 2-3 h; the sintering temperature is preferably 270-300° C., and the sintering time is preferably 30-40 min.

[0012] Furthermore, the preparation process of the modified polyacrylamide gel comprises: immersing polyacrylamide in a LiBr solution to obtain the modified polyacrylamide; preferably, the concentration of the LiBr solution is 2 to 4 mol / L, and the immersion time is preferably 30 to 60 min.

[0013] Furthermore, the baking temperature is 150-180° C., and the baking time is preferably 2-3 hours.

[0014] Furthermore, the above-mentioned forming process includes: cold pressing the sulfur-based solid electrolyte particles to obtain a sulfur-based solid electrolyte body; preferably, the pressure of the cold pressing process is 260 to 300 MPa, and the time of the cold pressing process is preferably 90 to 120 seconds.

[0015] Furthermore, in the above step S1, the solvent is selected from any one or more of methanol, ethanol, acetone, and diethyl ether; the preparation process of the preferred sulfur-based solid electrolyte precursor includes: in an argon atmosphere, grinding a lithium source, a phosphorus source, and a sulfur source, and then stirring and mixing them with an organic solvent to obtain a mixed solution, drying the mixed solution and then heat-treating it to obtain a sulfur-based solid electrolyte precursor; the preferred lithium source is selected from at least one of Li2S, Li2CO3, Li2O, LiOH, LiCl, Li2SO4, LiNO3 or Li; the preferred phosphorus source is selected from any one or more of sulfur-free diphosphorus, diammonium dihydrogen phosphate, monoammonium dihydrogen phosphate, pyrophosphoric acid, calcium phosphide, and sodium phosphide; the preferred sulfur source is selected from any one or more of carbon disulfide, molybdenum disulfide, elemental sulfur, copper sulfide, and silver sulfide; the preferred organic solvent is selected from any one or more of acetonitrile, ethylene glycol dimethyl ether, and tetrahydrofuran; the preferred grinding time is 10 to 30 minutes, and the preferred stirring and mixing temperature is 45 to 52°C.

[0016] According to one aspect of the present invention, a solid-state lithium-ion battery is provided, comprising a solid-state electrolyte, wherein the solid-state electrolyte is the aforementioned modified sulfur-based solid-state electrolyte.

[0017] By applying the technical solution of the present invention, on the one hand, the Li2O-2B2O3 coating layer coated on the surface of the sulfur-based solid electrolyte powder can block the direct contact between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby helping to inhibit the chemical reaction between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby greatly improving the interface compatibility between the sulfur-based solid electrolyte powder and the lithium metal negative electrode. On the other hand, the Li2O-2B2O3 coating layer can effectively alleviate the structural deformation of the sulfur-based solid electrolyte powder during the cycle, thereby effectively alleviating the interface stress between the solid electrolyte powder and the lithium metal negative electrode, thereby reducing the interface resistance. At the same time, the Li2O-2B2O3 coating layer blocks the side reactions of the solid electrolyte powder with moisture and oxygen in the air during processing, thereby significantly improving the stability of the modified sulfur-based solid electrolyte during processing. In addition, the modified polyacrylamide gel plays the role of a buffer layer and increases the contact area between the sulfur-based solid electrolyte body and the lithium metal negative electrode. Due to the difference in lattice parameters during battery cycling, stress and distortion exist. According to Li + Vacancy formation energy and Li + Migration energy, Li in sulfur-based solid electrolytes + Will migrate to the interface, thus forming a space charge region, which will increase the internal resistance of the battery and reduce the electrochemical performance. The presence of the buffer layer can effectively reduce the space charge region of the interface, which is beneficial to the Li + transmission, thereby effectively alleviating the interface stress and improving the stability of the battery, and further improving the electrical performance of the solid-state lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 The figure shows a SEM image of a modified sulfur-based solid electrolyte provided according to Example 1 of the present invention. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] As analyzed in the background technology of this application, the existing technology has the problems of large interfacial impedance, low ion transfer efficiency, poor interface stability and large interfacial stress of sulfur-based solid electrolytes, which lead to poor electrical performance of solid-state lithium metal batteries. In order to solve this problem, the present application provides a modified sulfur-based solid electrolyte and its preparation method, and a solid-state lithium-ion battery.

[0022] In a typical embodiment of the present application, a modified sulfur-based solid electrolyte is provided, which includes a sulfur-based solid electrolyte body and a coating layer attached to the surface of the sulfur-based solid electrolyte body, wherein the coating layer includes a modified polyacrylamide gel, the sulfur-based solid electrolyte body includes an aggregate of sulfur-based solid electrolyte particles, the sulfur-based solid electrolyte particles include sulfur-based solid electrolyte powder and a coating layer coated on the surface of the sulfur-based solid electrolyte powder, and the coating layer includes a Li2O-2B2O3 coating layer.

[0023] On the one hand, the Li2O-2B2O3 coating layer coated on the surface of the sulfur-based solid electrolyte powder can block the direct contact between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby helping to inhibit the chemical reaction between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby greatly improving the interfacial compatibility between the sulfur-based solid electrolyte powder and the lithium metal negative electrode. On the other hand, the Li2O-2B2O3 coating layer can effectively alleviate the structural deformation of the sulfur-based solid electrolyte powder during the cycle, thereby effectively alleviating the interfacial stress between the solid electrolyte powder and the lithium metal negative electrode, thereby reducing the interface resistance. At the same time, the Li2O-2B2O3 coating layer blocks the side reactions of the solid electrolyte powder with moisture and oxygen in the air during processing, thereby significantly improving the stability of the modified sulfur-based solid electrolyte during processing. In addition, the modified polyacrylamide gel plays the role of a buffer layer and increases the contact area between the sulfur-based solid electrolyte body and the lithium metal negative electrode. Due to the difference in lattice parameters during battery cycling, stress and distortion exist. According to Li + Vacancy formation energy and Li + Migration energy, Li in sulfur-based solid electrolytes+ Will migrate to the interface, thus forming a space charge region, which will increase the internal resistance of the battery and reduce the electrochemical performance. The presence of the buffer layer can effectively reduce the space charge region of the interface, which is beneficial to the Li + transmission, thereby effectively alleviating the interface stress and improving the stability of the battery, and further improving the electrical performance of the solid-state lithium-ion battery.

[0024] In one embodiment of the present application, the thickness of the coating layer is 2-4 μm, and the mass ratio of the coating layer to the sulfur-based solid electrolyte body is preferably 2-4:96-98.

[0025] The preferred thickness of the coating layer facilitates the effectiveness of the modified polyacrylamide gel, allowing the formed buffer layer to more effectively reduce the interfacial space charge region, thereby improving battery stability. The preferred mass ratio facilitates the synergistic effect of the coating layer, coating layer, and sulfur-based solid electrolyte, thereby helping to reduce the interfacial impedance of the modified sulfur-based solid electrolyte, improve the interfacial contact and stability of the modified sulfur-based solid electrolyte, and further fully utilize the high chemical stability, high ionic conductivity, and high safety properties of the sulfur-based solid electrolyte.

[0026] Preferably, the sulfur-based solid electrolyte particles are selected from (1+x)Li2S·xP2S5, Li4P2S6, Li3PS4, Li7P3S 11 、Li 6-y PS 5-y X 1+y He Li 11-z M 2-z P 1+z S 12 Any one or more of, wherein 0<x<1, 0≤y≤0.6, 0.5≤z≤1.5, M is selected from any one or more of Ge, Sn, and Si, X is a halogen, and preferably X is selected from any one or more of Cl, Br, and I, thereby helping to improve the full synergistic cooperation between the sulfur-based solid electrolyte particles and the coating layer and the coating layer, thereby making the comprehensive electrical properties of the modified sulfur-based solid electrolyte better.

[0027] In another typical embodiment of the present application, a method for preparing the aforementioned modified sulfur-based solid electrolyte is provided, the preparation method comprising: step S1, mixing a sulfur-based solid electrolyte precursor, Li2O-2B2O3 and a solvent to obtain a mixture; step S2, ball milling, drying and sintering the mixture in sequence to obtain sulfur-based solid electrolyte particles; step S3, molding the sulfur-based solid electrolyte particles to obtain a sulfur-based solid electrolyte body; and step S4, coating the surface of the sulfur-based solid electrolyte body with modified polyacrylamide gel and then baking to obtain a modified sulfur-based solid electrolyte.

[0028] The above step S1 makes the solid electrolyte precursor and Li2O-2B2O3 uniformly mixed, and the mixture is ball-milled, dried and sintered in step S2 to obtain sulfur-based solid electrolyte particles with a Li2O-2B2O3 coating layer on the surface. The molding process in step S3 obtains a sulfur-based solid electrolyte body that meets the application requirements. After step S4, the surface of the sulfur-based solid electrolyte body is modified and baked to form a coating layer on the surface of the sulfur-based solid electrolyte body. The Li2O-2B2O3 coating layer coated on the surface of the sulfur-based solid electrolyte powder can block the direct contact between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby helping to inhibit the chemical reaction between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby greatly improving the interfacial compatibility between the sulfur-based solid electrolyte powder and the lithium metal negative electrode. On the other hand, the Li2O-2B2O3 coating layer can effectively alleviate the structural deformation of the sulfur-based solid electrolyte powder during the cycle, thereby effectively alleviating the interfacial stress between the solid electrolyte powder and the lithium metal negative electrode, thereby reducing the interface resistance. At the same time, the Li2O-2B2O3 coating layer blocks the side reactions between the solid electrolyte powder and the moisture and oxygen in the air during processing, thereby significantly improving the stability of the modified sulfur-based solid electrolyte during processing. In addition, the modified polyacrylamide gel plays the role of a buffer layer and increases the contact area between the sulfur-based solid electrolyte and the lithium metal negative electrode. Due to the difference in lattice parameters during battery cycling, stress and distortion exist. According to Li + Vacancy formation energy and Li + Migration energy, Li in sulfur-based solid electrolytes + Will migrate to the interface, thus forming a space charge region, which will increase the internal resistance of the battery and reduce the electrochemical performance. The presence of the buffer layer can effectively reduce the space charge region of the interface, which is beneficial to the Li + The above preparation method is simple and low in cost.

[0029] In one embodiment of the present application, in the above step S2, the D50 particle size of the sulfur-based solid electrolyte particles is 0.370-0.520 μm; the ball milling speed is preferably 300-350 r / min, and the ball milling time is preferably 4-6 h; the drying temperature is preferably 90-100° C., and the drying time is preferably 2-3 h; the sintering temperature is preferably 270-300° C., and the sintering time is preferably 30-40 min.

[0030] The above ball milling conditions such as 300r / min, 310r / min, 320r / min, 330r / min, 340r / min or 350r / min are preferred to improve the efficiency of the ball milling process and more efficiently obtain sulfur-based solid electrolyte particles in the above particle size range. Drying before sintering and controlling the drying at the above temperature such as 90°C, 95°C or 100°C helps to remove the organic solvent in the particles obtained by ball milling, thereby making the sintering step more conducive. The above sintering conditions are conducive to perfecting the structure of the sulfur-based solid electrolyte precursor to a crystalline state and helping to more evenly coat Li2O-2B2O3 on the surface of the sulfur-based solid electrolyte powder.

[0031] In one embodiment of the present application, the preparation process of the modified polyacrylamide gel includes: immersing polyacrylamide in a LiBr solution to obtain modified polyacrylamide; preferably, the concentration of the LiBr solution is 2 to 4 mol / L, and the immersion time is preferably 30 to 60 min.

[0032] Through the above impregnation, a certain amount of lithium ions are loaded between the molecular chains of the polyacrylamide, thereby improving the lithium ion transmission capacity of the modified polyacrylamide and further enhancing the effect of its buffer layer.

[0033] Preferably, acrylamide: carrageenan: N, N-methylene acrylamide: KCl: deionized water are weighed in a mass ratio of 7.5:1.5:5:0.09:41 (expanded range), mixed, placed in an oil bath at 90-95° C. and stirred for 4-6 hours, poured into a culture dish and treated at 5-7° C. for 1-2 hours, and placed under an ultraviolet lamp for 2-3 hours to obtain polyacrylamide, which is more conducive to the convenient, fast and low-cost preparation of polyacrylamide by those skilled in the art.

[0034] Preferably, the baking temperature is 150-180° C., and the baking time is 2-3 hours, which helps to improve the firmness of the bonding between the coating layer and the sulfur-based solid electrolyte body.

[0035] In one embodiment of the present application, the above-mentioned forming process includes: cold pressing the sulfur-based solid electrolyte particles to obtain a sulfur-based solid electrolyte body; preferably, the cold pressing pressure is 260 to 300 MPa, and the cold pressing time is preferably 90 to 120 seconds.

[0036] The above cold pressing treatment conditions can not only reduce the impact on the performance of the sulfur-based solid electrolyte particles, but also quickly and efficiently achieve uniform adhesion of the modified polyacrylamide to the sulfur-based solid electrolyte body.

[0037] In some embodiments of the present application, in the above step S1, the solvent is preferably selected from any one or more of methanol, ethanol, acetone, and ether, so as to help improve the uniformity of dispersion of the sulfur-based solid electrolyte precursor, Li2O-2B2O3 and the solvent; the preparation process of the sulfur-based solid electrolyte precursor preferably comprises: in an argon atmosphere, grinding a lithium source, a phosphorus source, and a sulfur source, stirring and mixing them with an organic solvent to obtain a mixed solution, drying the mixed solution and then heat-treating it to obtain a sulfur-based solid electrolyte precursor; the lithium source is preferably selected from Li2S, Li2CO3, Li2O, LiOH, At least one of LiCl, Li2SO4, LiNO3 or Li; the phosphorus source is preferably selected from any one or more of non-sulfurized diphosphorus, diammonium dihydrogen phosphate, monoammonium dihydrogen phosphate, pyrophosphoric acid, calcium phosphide, and sodium phosphide; the sulfur source is preferably selected from any one or more of carbon disulfide, molybdenum disulfide, elemental sulfur, copper sulfide, and silver sulfide; the organic solvent is preferably selected from any one or more of acetonitrile, ethylene glycol dimethyl ether, and tetrahydrofuran; the grinding treatment time is preferably 10 to 30 minutes, and the stirring and mixing temperature is preferably 45 to 52° C., thereby facilitating the low-cost preparation of a sulfur-based solid electrolyte precursor.

[0038] In addition, the actual preparation process takes into account the possibility of a certain degree of air leakage in the glove box. Therefore, the total content of moisture and oxygen in the argon atmosphere is controlled to be less than 0.1 ppm as much as possible.

[0039] In another typical embodiment of the present application, a solid-state lithium-ion battery is provided, comprising a solid-state electrolyte, wherein the solid-state electrolyte is the aforementioned modified sulfur-based solid-state electrolyte.

[0040] The solid-state lithium-ion battery comprising the modified sulfur-based solid electrolyte of the present application has higher ionic conductivity, better capacity and cycle performance.

[0041] The beneficial effects of the present application will be further illustrated below with reference to examples.

[0042] Example 1

[0043] A method for modifying a sulfide solid electrolyte in a lithium-ion battery, characterized by comprising the following steps:

[0044] S1. Lithium source and phosphorus source were weighed according to the molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 10 minutes, and added to the organic solution of acetonitrile. The mixture was magnetically stirred at 200 rpm at 52 ° C for 80 hours, and the mixture was baked in an oven at 90 ° C for 4 hours. The dried powder was heat-treated at 270 ° C for 60 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0045] S2. H3BO4 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 200 rpm at 75°C for 4 hours until the solvent was completely evaporated. The mixture was heat treated at 500°C for 9 hours and then naturally cooled to room temperature to obtain a coating layer B (Li2O-2B2O3). Precursor powder A and coating layer B were added to the methanol solution in a glove box and ball-milled at 350 rpm for 4 hours. The mixture was then baked at 100°C for 2 hours. The dried powder was heat treated at 270°C for 30 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS coated with Li2O-2B2O3, whose D50 particle size was 0.374 μm.

[0046] S3. Acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water were weighed in a mass ratio of 7.5:1.5:5:0.09:41, mixed, and placed in a 90°C oil bath with magnetic stirring at 200 rpm for 6 h. The mixture was poured into a Petri dish and refrigerated at 5°C for 2 h. After that, it was taken out and placed under a UV lamp for 3 h. After cooling naturally, it was immersed in 2 mol·L -1 LiBr solution for 30 min to obtain modified polyacrylamide gel C.

[0047] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 300 MPa for 120 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 2 μm, and bake it at 150°C for 3 hours to obtain the final modified sulfur-based solid electrolyte, wherein the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 2:98.

[0048] Example 2

[0049] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 15 minutes, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 300 rpm at 50°C for 60 hours, and the mixture was baked in an oven at 95°C for 3 hours. The dried powder was heat-treated at 270°C for 60 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0050] S2. H3BO4 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 300 rpm at 80°C for 3 hours until the solvent was completely evaporated. The mixture was heat treated at 520°C for 8 hours and then naturally cooled to room temperature to obtain a coating layer B (Li2O-2B2O3). Precursor powder A and coating layer B were added to the methanol solution in a glove box and ball-milled at 350 rpm for 4 hours. The mixture was then baked at 90°C for 3 hours. The dried powder was heat treated at 280°C for 35 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS coated with Li2O-2B2O3, with a D50 particle size of 0.469 μm.

[0051] S3. Weigh acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water in a mass ratio of 7.5:1.5:5:0.09:41, mix them, place them in a 95°C oil bath, and stir them magnetically at 300 rpm for 4 h. Pour the mixture into a Petri dish and cool it at 5°C for 2 h. Then take it out and place it under ultraviolet light for 3 h. After cooling naturally, immerse it in 2 mol·L -1 The modified polyacrylamide gel C was obtained by immersing the gel in a LiBr solution for 30 min.

[0052] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 300 MPa for 120 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 2 μm, and bake it at 150°C for 3 hours to obtain the final modified sulfur-based solid electrolyte, wherein the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 2.5:97.5.

[0053] Example 3

[0054] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 20 min, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 300 rpm at 50 ° C for 70 h, and the mixture was baked in an oven at 85 ° C for 3 h. The dried powder was heat-treated at 270 ° C for 60 min and cooled naturally to obtain Li7P3S 11 Precursor A.

[0055] S2. H3BO3 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 300 rpm at 75°C for 4 hours until the solvent was completely evaporated. After heat treatment at 480°C for 10 hours, the coating layer B (Li2O-2B2O3) was obtained by naturally cooling to room temperature. The precursor powder A and the coating layer B were added to the methanol solution in a glove box and ball-milled at 300 rpm for 6 hours. The mixture was then baked at 90°C for 3 hours. The dried powder was heat treated at 280°C for 35 minutes and naturally cooled to room temperature to obtain the Li2O-2B2O3-coated solid electrolyte LPS with a D50 particle size of 0.486 μm.

[0056] S3. Acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water were weighed in a mass ratio of 7.5:1.5:5:0.09:41, mixed, and placed in a 90°C oil bath with magnetic stirring at 300 rpm for 4 h. The mixture was poured into a Petri dish and placed in a 7°C cold treatment for 1 h. After that, it was taken out and placed under a UV lamp for 3 h. After cooling naturally, it was immersed in 2 mol·L -1 The modified polyacrylamide gel C was obtained by immersing the gel in a LiBr solution for 40 min.

[0057] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 260 MPa for 100 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 2 μm, and bake it at 150°C for 3 hours to obtain the final modified sulfur-based solid electrolyte, wherein the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 3:97.

[0058] Example 4

[0059] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 25 minutes, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 300 rpm at 50°C for 70 hours, and the mixture was baked in an oven at 80°C for 3 hours. The dried powder was heat-treated at 260°C for 60 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0060] S2. H3BO3 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 300 rpm at 78°C for 3 hours until the solvent was completely evaporated. After heat treatment at 520°C for 8 hours, the coating layer B (Li2O-2B2O3) was obtained by naturally cooling to room temperature. The precursor powder A and the coating layer B were added to the methanol solution in a glove box and ball-milled at 300 rpm for 5 hours, and then baked at 100°C for 3 hours. The dried powder was heat treated at 300°C for 30 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS coated with Li2O-2B2O3, whose D50 particle size was 0.496 μm.

[0061] S3. Acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water were weighed in a mass ratio of 7.5:1.5:5:0.09:41, mixed, and placed in a 92°C oil bath with magnetic stirring at 300 rpm for 5 h. The mixture was poured into a Petri dish and cooled at 7°C for 1 h. After that, it was taken out and placed under ultraviolet light for 3 h. After cooling naturally, it was immersed in 2 mol·L -1 The modified polyacrylamide gel C was obtained by immersing the gel in a LiBr solution for 40 min.

[0062] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 280 MPa for 100 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet. The coating layer has a thickness of 4 μm, and bake it at 180°C for 3 hours to obtain the final modified sulfur-based solid electrolyte. The mass ratio of the Li2O-2B2O3 coating layer, the coating layer, and the solid electrolyte sheet is 3.5:96.5.

[0063] Example 5

[0064] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 30 minutes, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 300 rpm at 52°C for 60 hours, and the mixture was baked in an oven at 80°C for 4 hours. The dried powder was heat-treated at 290°C for 45 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0065] S2. H3BO3 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 200 rpm at 70°C for 4 hours until the solvent was completely evaporated. After heat treatment at 480°C for 8 hours, the coating layer B (Li2O-2B2O3) was obtained by naturally cooling to room temperature. The precursor powder A and the coating layer B were added to the methanol solution in a glove box and ball-milled at 300 rpm for 6 hours. The mixture was then baked at 90°C for 3 hours. The dried powder was heat treated at 270°C for 30 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS coated with Li2O-2B2O3, whose D50 particle size was 0.395 μm.

[0066] S3. Acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water were weighed in a mass ratio of 7.5:1.5:5:0.09:41, mixed, and placed in a 90°C oil bath with magnetic stirring at 200 rpm for 4 h. The mixture was poured into a Petri dish and placed in a cold treatment at 7°C for 2 h. After that, it was taken out and placed under a UV lamp for 3 h. After natural cooling, the polymer was obtained and immersed in 2 mol·L -1 The modified polyacrylamide gel C was obtained by immersing the gel in a LiBr solution for 60 min.

[0067] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 260 MPa for 90 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 4 μm, and bake it at 150°C for 3 hours to obtain the final modified sulfur-based solid electrolyte, wherein the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 4:96.

[0068] Example 6

[0069] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 10 min, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 300 rpm at 52 ° C for 60 h, and the mixture was baked in an oven at 80 ° C for 4 h. The dried powder was heat-treated at 290 ° C for 45 min and cooled naturally to obtain Li7P3S 11 Precursor A,

[0070] S2, press Li7P3S 11: Lithium source molar ratio 2:1 H3BO3 and LiOH·H2O were weighed, placed in a methanol solution and magnetically stirred at 200 rpm at 70°C for 4 hours until the solvent was completely evaporated. After heat treatment at 480°C for 8 hours, it was naturally cooled to room temperature to obtain the coating layer B (Li2O-2B2O3). The precursor powder A and the coating layer B were added to the methanol solution in a glove box and ball milled at 300 rpm for 6 hours, and then placed at 90°C for 3 hours. The dried powder was heat treated at 300°C for 40 minutes and naturally cooled to room temperature to obtain the solid electrolyte LPS coated with Li2O-2B2O3, whose D50 particle size was 0.395μm.

[0071] S3. Weigh acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water in a mass ratio of 7.5:1.5:5:0.09:41, mix them, place them in a 90°C oil bath, and stir them magnetically at 200 rpm for 6 h. Pour the mixture into a Petri dish and cool it at 6°C for 2 h. Then take it out and place it under ultraviolet light for 3 h. After cooling naturally, immerse it in 4 mol·L -1 LiBr solution for 60 min to obtain the final modified polyacrylamide gel C;

[0072] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 260 MPa for 90 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 2 μm, and bake it at 180°C for 3 hours to obtain the final modified sulfur-based solid electrolyte, wherein the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 2:98.

[0073] Example 7

[0074] A method for modifying a sulfide solid electrolyte in a lithium-ion battery, characterized by comprising the following steps:

[0075] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 30 min, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 200 rpm at 52 ° C for 80 h, and the mixture was baked in an oven at 95 ° C for 4 h. The dried powder was heat-treated at 290 ° C for 60 min and cooled naturally to obtain Li7P3S 11 Precursor A.

[0076] S2. H3BO3 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 300 rpm at 75°C for 4 hours until the solvent was completely evaporated. After heat treatment at 500°C for 8 hours, the coating layer B (Li2O-2B2O3) was obtained by naturally cooling to room temperature. The precursor powder A and the coating layer B were added to the methanol solution in a glove box and ball-milled at 350 rpm for 6 hours. The mixture was then baked at 90°C for 2 hours. The dried powder was heat treated at 300°C for 40 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS coated with Li2O-2B2O3, whose D50 particle size was 0.453 μm.

[0077] S3. Acrylamide: carrageenan: N,N-methylene acrylamide: KCl: deionized water were weighed in a mass ratio of 7.5:1.5:5:0.09:41, mixed, and placed in a 95°C oil bath with magnetic stirring at 200 rpm for 6 h. The mixture was poured into a Petri dish and cooled at 5°C for 1 h. After that, it was taken out and placed under a UV lamp for 3 h. After natural cooling, the polymer was obtained and immersed in 4 mol·L -1 The modified polyacrylamide gel C was obtained by immersing the gel in a LiBr solution for 60 min.

[0078] S4. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, and cold press it at a pressure of 260 MPa for 120 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 4 μm, and bake it at 150°C for 2 hours to obtain the final modified sulfur-based solid electrolyte, wherein the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 4:96.

[0079] Example 8

[0080] The difference from Example 3 is that the thickness of the coating layer is 4 μm, and a modified sulfur-based solid electrolyte is finally obtained.

[0081] Example 9

[0082] The difference from Example 3 is that the thickness of the coating layer is 1 μm, and a modified sulfur-based solid electrolyte is finally obtained.

[0083] Example 10

[0084] The difference from Example 3 is that the thickness of the coating layer is 5 μm, and a modified sulfur-based solid electrolyte is finally obtained.

[0085] Example 11

[0086] The difference from Example 3 is that the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 4:96, and a modified sulfur-based solid electrolyte is finally obtained.

[0087] Example 12

[0088] The difference from Example 3 is that the mass ratio of the Li2O-2B2O3 coating layer to the solid electrolyte sheet is 1:99, and a modified sulfur-based solid electrolyte is finally obtained.

[0089] Example 13

[0090] The difference from Example 3 is that the sintering temperature is 300° C., and a modified sulfur-based solid electrolyte is finally obtained.

[0091] Example 14

[0092] The difference from Example 3 is that the sintering temperature is 265° C., and a modified sulfur-based solid electrolyte is finally obtained.

[0093] Example 15

[0094] The difference from Example 3 is that the concentration of the LiBr solution is 4 mol / L, and a modified sulfur-based solid electrolyte is finally obtained.

[0095] Example 16

[0096] The difference from Example 3 is that the concentration of the LiBr solution is 1.8 mol / L, and a modified sulfur-based solid electrolyte is finally obtained.

[0097] Example 17

[0098] The difference from Example 3 is that the baking temperature is 180° C., and a modified sulfur-based solid electrolyte is finally obtained.

[0099] Comparative Example 1

[0100] A method for modifying a sulfide solid electrolyte in a lithium-ion battery, characterized by comprising the following steps:

[0101] S1. Lithium source and phosphorus source were weighed according to the molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 10 minutes, and then added to the organic solution of acetonitrile. The mixture was magnetically stirred at 200 rpm at 52 ° C for 80 hours, and the mixture was baked in an oven at 90 ° C for 4 hours. The dried powder was heat-treated at 270 ° C for 60 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0102] S2. In a glove box, the precursor powder A was added to a methanol solution and dispersed by ball milling at 350 rpm for 4 h. The precursor powder was then baked at 100 °C for 2 h. The dried powder was heat treated at 270 °C for 30 min and naturally cooled to room temperature to obtain a solid electrolyte LPS.

[0103] S3. Acrylamide: carrageenan: N, N-methylene acrylamide: KCl: deionized water were weighed in a mass ratio of 7.5:1.5:5:0.09:41, mixed, and placed in a 90°C oil bath with magnetic stirring at 200 rpm for 6 h. The mixture was poured into a Petri dish and placed in a 5°C cold treatment for 2 h. After that, it was taken out and placed under a UV lamp for 3 h. After cooling naturally, it was immersed in 2 mol·L -1 The modified polyacrylamide gel C was obtained by immersing the gel in a LiBr solution for 30 min.

[0104] S4. Pour the solid electrolyte LPS powder into a mold and cold press it at a pressure of 300 MPa for 120 seconds to obtain a solid electrolyte sheet. Then, coat the modified polyacrylamide gel C on the electrolyte sheet with a coating thickness of 2 μm and bake it at 150°C for 3 hours to obtain the final modified sulfur-based solid electrolyte.

[0105] Comparative Example 2

[0106] S1. Lithium source and phosphorus source were weighed according to the molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 15 minutes, and added to the organic solution of acetonitrile. The mixture was magnetically stirred at 200 rpm at 52 ° C for 80 hours, and the mixture was baked in an oven at 90 ° C for 4 hours. The dried powder was heat-treated at 270 ° C for 60 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0107] S2. H3BO3 and LiOH·H2O were weighed in a boric acid: lithium source molar ratio of 2:1, placed in a methanol solution and magnetically stirred at 200 rpm at 75°C for 4 hours until the solvent was completely evaporated. After heat treatment at 500°C for 9 hours, the coating layer B (Li2O-2B2O3) was obtained by naturally cooling to room temperature. The precursor powder A and the coating layer B were added to the methanol solution in a glove box and ball-milled at 350 rpm for 4 hours. The mixture was then baked at 100°C for 2 hours. The dried powder was heat treated at 270°C for 30 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS coated with Li2O-2B2O3.

[0108] S3. Pour the Li2O-2B2O3-coated solid electrolyte LPS powder into a mold, cold press it at a pressure of 300 MPa for 120 seconds to obtain a solid electrolyte sheet, and bake it at 150°C for 3 hours to obtain the final modified sulfur-based solid electrolyte.

[0109] Comparative Example 3

[0110] S1. Lithium source and phosphorus source were weighed at a molar ratio of Li2S:P2S5 of 7:3, ground in a mortar for 25 minutes, and added to an organic solution of acetonitrile. The mixture was magnetically stirred at 300 rpm at 50°C for 70 hours, and the mixture was baked in an oven at 80°C for 3 hours. The dried powder was heat-treated at 260°C for 60 minutes and cooled naturally to obtain Li7P3S 11 Precursor A.

[0111] S2, in the glove box, the precursor Li7P3S 11 After being added to a methanol solution and dispersed by ball milling at 300 rpm for 5 hours, it was then placed at 100°C for 3 hours. The dried powder was heat-treated at 300°C for 30 minutes and naturally cooled to room temperature to obtain a solid electrolyte LPS.

[0112] S3. Pour the solid electrolyte LPS powder into a mold, cold press it at a pressure of 280 MPa for 100 seconds to obtain a solid electrolyte sheet, and bake it at 180°C for 3 hours to obtain the final sulfur-based solid electrolyte.

[0113] Performance testing:

[0114] Composite cathode materials were prepared using the modified sulfur-based solid electrolytes of Examples 1 to 17 and Comparative Examples 1 to 3, respectively, in a ratio of Li2S:conductive carbon black:modified sulfur-based solid electrolyte = 55:30:15. 2-3 mg of composite cathode material powder was evenly spread on one side of the electrolyte and then cold-pressed into tablets on a tablet press at 360 MPa for 3 minutes. A lithium sheet was then attached to the other side of the electrolyte. Finally, the battery case was enclosed to isolate it from air and allowed to stand for a period of time before use. The entire battery assembly process was performed in an argon-filled glove box.

[0115] The ionic conductivity of each modified sulfur-based solid electrolyte was tested. Under the test conditions of 2.8-5.0 V, the 0.5C discharge specific capacity, 1C discharge specific capacity and 55°C / 50 cycle capacity retention rate at 25°C were tested. The test results are listed in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0120] On the one hand, the Li2O-2B2O3 coating layer coated on the surface of the sulfur-based solid electrolyte powder can block the direct contact between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby helping to inhibit the chemical reaction between the sulfur-based solid electrolyte powder and the lithium metal negative electrode, thereby greatly improving the interfacial compatibility between the sulfur-based solid electrolyte powder and the lithium metal negative electrode. On the other hand, the Li2O-2B2O3 coating layer can effectively alleviate the structural deformation of the sulfur-based solid electrolyte powder during the cycle, thereby effectively alleviating the interfacial stress between the solid electrolyte powder and the lithium metal negative electrode, thereby reducing the interface resistance. At the same time, the Li2O-2B2O3 coating layer blocks the side reactions of the solid electrolyte powder with moisture and oxygen in the air during processing, thereby significantly improving the stability of the modified sulfur-based solid electrolyte during processing. In addition, the modified polyacrylamide gel plays the role of a buffer layer and increases the contact area between the sulfur-based solid electrolyte body and the lithium metal negative electrode. Due to the difference in lattice parameters during battery cycling, stress and distortion exist. According to Li + Vacancy formation energy and Li + Migration energy, Li in sulfur-based solid electrolytes + Will migrate to the interface, thus forming a space charge region, which will increase the internal resistance of the battery and reduce the electrochemical performance. The presence of the buffer layer can effectively reduce the space charge region of the interface, which is beneficial to the Li + transmission, thereby effectively alleviating the interface stress and improving the stability of the battery, and further improving the electrical performance of the solid-state lithium-ion battery.

[0121] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A modified sulfur-based solid electrolyte, characterized in that: The modified sulfur-based solid electrolyte comprises a sulfur-based solid electrolyte body and a coating layer attached to the surface of the sulfur-based solid electrolyte body, wherein the coating layer comprises a modified polyacrylamide gel, the sulfur-based solid electrolyte body comprises an aggregate of sulfur-based solid electrolyte particles, the sulfur-based solid electrolyte particles comprise sulfur-based solid electrolyte powder and a coating layer coated on the surface of the sulfur-based solid electrolyte powder, and the coating layer comprises a Li2O-2B2O3 coating layer; The preparation process of the modified polyacrylamide gel comprises: immersing polyacrylamide in a LiBr solution to obtain the modified polyacrylamide; The thickness of the coating layer is 2-4 μm, and the mass ratio of the coating layer to the sulfur-based solid electrolyte body is 2-4: 96-98.

2. The modified sulfur-based solid electrolyte according to claim 1, characterized in that The sulfur-based solid electrolyte particles are selected from (1+x)Li2S·xP2S5, Li4P2S6, Li3PS4, Li7P3S 11 、Li 6-y PS 5-y X 1+y He Li 11-z M 2-z P 1+z S 12 Any one or more of, wherein 0<x<1, 0≤y≤0.6, 0.5≤z≤1.5, M is selected from any one or more of Ge, Sn, and Si, and X is selected from any one or more of Cl, Br, and I.

3. The modified sulfur-based solid electrolyte according to claim 1, characterized in that The concentration of the LiBr solution is 2-4 mol / L.

4. The modified sulfur-based solid electrolyte according to claim 1, characterized in that The immersion time is 30 to 60 minutes.

5. A method for preparing the modified sulfur-based solid electrolyte according to claim 1 or 2, characterized in that: The preparation method comprises: Step S1, mixing a sulfur-based solid electrolyte precursor, Li2O-2B2O3 and a solvent to obtain a mixture; Step S2, ball milling, drying, and sintering the mixture in sequence to obtain sulfur-based solid electrolyte particles; Step S3, forming the sulfur-based solid electrolyte particles to obtain a sulfur-based solid electrolyte body; and Step S4: coating the surface of the sulfur-based solid electrolyte with modified polyacrylamide gel and then baking the modified sulfur-based solid electrolyte to obtain the modified sulfur-based solid electrolyte.

6. The preparation method according to claim 5, characterized in that In step S2, the D50 particle size of the sulfur-based solid electrolyte particles is 0.370-0.520 μm.

7. The preparation method according to claim 5, characterized in that The rotation speed of the ball milling process is 300-350 r / min.

8. The preparation method according to claim 5, characterized in that The ball milling time is 4 to 6 hours.

9. The preparation method according to claim 5, characterized in that The drying temperature is 90-100°C.

10. The preparation method according to claim 5, characterized in that The drying time is 2 to 3 hours.

11. The preparation method according to claim 5, characterized in that The sintering temperature is 270-300°C.

12. The preparation method according to claim 5, characterized in that The sintering time is 30 to 40 minutes.

13. The preparation method according to any one of claims 5 to 12, characterized in that The baking temperature is 150-180°C.

14. The preparation method according to any one of claims 5 to 12, characterized in that The baking time is 2 to 3 hours.

15. The preparation method according to any one of claims 5 to 12, characterized in that The molding process includes: The sulfur-based solid electrolyte particles are subjected to cold pressing to obtain the sulfur-based solid electrolyte body.

16. The preparation method according to claim 15, characterized in that The pressure of the cold pressing treatment is 260-300 MPa.

17. The preparation method according to claim 15, characterized in that The cold pressing treatment time is 90 to 120 seconds.

18. The preparation method according to any one of claims 5 to 12, characterized in that In step S1, the solvent is selected from any one or more of methanol, ethanol, acetone, and ether.

19. The preparation method according to any one of claims 5 to 12, characterized in that The preparation process of the sulfur-based solid electrolyte precursor includes: in an argon atmosphere, The lithium source, phosphorus source and sulfur source are ground and then stirred and mixed with an organic solvent to obtain a mixed solution. The mixed solution is dried and then heat-treated to obtain the sulfur-based solid electrolyte precursor.

20. The preparation method according to claim 19, characterized in that The lithium source is selected from at least one of Li2S, Li2CO3, Li2O, LiOH, LiCl, Li2SO4, LiNO3 or Li.

21. The preparation method according to claim 19, characterized in that The phosphorus source is selected from any one or more of non-sulfurized diphosphorus, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, pyrophosphoric acid, calcium phosphide, and sodium phosphide.

22. The preparation method according to claim 19, characterized in that The sulfur source is selected from any one or more of carbon disulfide, molybdenum disulfide, elemental sulfur, copper sulfide, and silver sulfide.

23. The preparation method according to claim 19, characterized in that The organic solvent is selected from any one or more of acetonitrile, ethylene glycol dimethyl ether, and tetrahydrofuran.

24. The preparation method according to claim 19, characterized in that The grinding time is 10 to 30 minutes.

25. The preparation method according to claim 19, characterized in that The temperature of the stirring and mixing is 45-52°C.

26. A solid-state lithium-ion battery comprising a solid electrolyte, characterized in that: The solid electrolyte is the modified sulfur-based solid electrolyte according to claim 1 or 2.

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