A modified sulfide solid electrolyte, a sulfide solid electrolyte membrane, and a preparation method and applications thereof

Abstract

The application belongs to the technical field of sulfide solid electrolyte films, and discloses a modified sulfide solid electrolyte, a sulfide solid electrolyte film, and a preparation method and application thereof. The preparation method of the modified sulfide solid electrolyte comprises the following steps: under an inert atmosphere, a solution containing a bidentate dithiol ligand is contacted with a sulfide solid electrolyte to react, so that the modified sulfide solid electrolyte is obtained; the bidentate dithiol ligand is selected from at least one of 1,3-dithiol derivatives, aromatic dithiols, aliphatic bidentate dithiols, cyclic bidentate dithiols, and substituted bidentate dithiols; by using the bidentate dithiol ligand to modify the surface of the sulfide solid electrolyte, the performance is synergistically improved, and the industrialization cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of sulfide solid electrolyte membrane technology, specifically to a modified sulfide solid electrolyte, a sulfide solid electrolyte membrane, its preparation method, and its application. Background Technology

[0002] The global energy transition and the large-scale application of power batteries and energy storage power stations have placed higher demands on the energy density, safety, and cycle life of lithium-ion batteries. Traditional liquid lithium-ion batteries use organic electrolytes, which pose safety hazards such as leakage, combustion, and explosion, and their energy density is already close to its theoretical limit, making it difficult to meet the application requirements of long-range and high-safety applications. All-solid-state lithium batteries replace liquid electrolytes and separators with solid electrolytes, offering advantages such as high safety, high energy density, and compatibility with lithium metal anodes, making them a core research and development direction for next-generation high-performance energy storage devices.

[0003] Sulfide solid electrolytes have high ionic conductivity at room temperature (up to 10). -3 ~10 -4 With its low ion conductivity (S / cm), low grain boundary impedance, good mechanical flexibility, and the ability to prepare dense electrolyte membranes through cold pressing / solution casting, solid-state electrolyte systems are considered one of the most promising solid-state electrolyte systems for industrialization, possessing extremely high application value in vehicle power and large-scale energy storage. Currently, the most studied sulfide solid-state electrolyte systems include sulfide-germanium sulfide solid-state electrolytes, lithium thiocyanate superionic conductor sulfide solid-state electrolytes, glassy sulfide solid-state electrolytes, and crystalline sulfide solid-state electrolytes, which have achieved excellent ion conduction and electrochemical stability at the laboratory level.

[0004] Despite the significant advantages of sulfide solid electrolytes, their industrial application still faces insurmountable technical bottlenecks, severely restricting their large-scale promotion: Firstly, their air / moisture stability is extremely poor, and the production and application environments are harsh, with sulfur in sulfide electrolytes... 2- PS4 3- The active groups readily react with moisture and oxygen in the air, rapidly hydrolyzing to produce highly toxic, flammable, and explosive H2S gas. This also causes the electrolyte crystal structure to collapse and the ionic conductivity to drop sharply, requiring processing in an ultra-dry, inert atmosphere, which is extremely costly. Secondly, it is difficult to balance the mechanical properties and density of the electrolyte membrane. Pure sulfide electrolytes are brittle, and cold-pressed films are prone to cracks and pores. Adding polymers to assist film formation reduces ionic conductivity and causes interfacial phase separation. Thirdly, the surface activity is high, and the interfacial stability is insufficient. It is prone to side reactions with the positive and negative electrode materials, forming a high-resistance passivation layer and deteriorating the battery cycle performance.

[0005] Chinese patent document CN120657262A discloses a sulfide solid electrolyte slurry, a high-density sulfide solid electrolyte film, and a method for preparing the same, belonging to the field of all-solid-state battery technology. The method for preparing the sulfide solid electrolyte slurry includes the steps of mixing polythiols, solvents, binders, and sulfide solid electrolytes, and stirring to obtain the sulfide solid electrolyte slurry; wherein the polythiols refer to thiols containing two or more mercapto groups. The core innovation lies in introducing polythiols into the sulfide solid electrolyte slurry, utilizing the SS interaction force between the mercapto groups and the sulfide solid electrolyte to effectively reduce the distance between sulfide solid electrolytes, thereby reducing the voids between them and preparing a sulfide solid electrolyte film with higher density. It is evident that this patent uses polythiols as processing aids to optimize the slurry formulation and does not involve modification of the electrolyte.

[0006] Chinese patent CN120413769A discloses a method for preparing a sulfide solid electrolyte membrane, comprising: uniformly mixing a sulfide electrolyte, a polythiol material, and a solvent to obtain a first slurry; adding an initiator and a binder to the first slurry and heating and mixing to obtain a second slurry; coating the second slurry onto a substrate and drying it to obtain a sulfide solid electrolyte membrane. In this method, the polythiol material is used only as an auxiliary additive to modify the electrolyte and does not form a synergistic effect with the binder.

[0007] Existing modification technologies struggle to address the aforementioned pain points: bulk element doping cannot improve surface activity and has limited effect on improving air stability; inorganic material coating suffers from poor lattice matching, easy detachment of the coating layer, and increased interfacial impedance; polymer composites significantly reduce ionic conductivity; monothiol surface modifications have weak bonding forces, resulting in a loose protective layer and poor long-term protective effect.

[0008] In summary, there is a lack of modification techniques and electrolyte membrane preparation schemes that can simultaneously achieve high air stability, high ionic conductivity, excellent film-forming properties, and good interfacial compatibility of sulfide solid electrolytes. Summary of the Invention

[0009] The technical problem to be solved by this invention is that existing sulfide solid electrolytes have poor air stability, high interfacial impedance, and difficulty in synergistically achieving ionic conductivity and mechanical properties. This invention provides a modified sulfide solid electrolyte, a sulfide solid electrolyte membrane, its preparation method, and its application. By using bidentate dithiol ligands to modify the surface of the sulfide solid electrolyte, multiple properties are synergistically improved, and industrialization costs are reduced.

[0010] To solve the above-mentioned technical problems, the first aspect of the present invention provides a method for preparing a modified sulfide solid electrolyte, comprising: Under an inert atmosphere, a solution containing bidentate dithiol ligands is contacted with a sulfide solid electrolyte to react and obtain the modified sulfide solid electrolyte. The bidentate dithiol ligand is selected from at least one of 1,3-dithiol derivatives, aromatic dithiols, aliphatic bidentate dithiols, cyclic bidentate dithiols, and substituted bidentate dithiols; preferably 1,3-dithiol derivatives and / or aromatic dithiols, and most preferably aromatic dithiols.

[0011] In this invention, when the bidentate dithiol ligand is selected from a combination of 1,3-dithiol derivatives and aromatic dithiols, the mass ratio of 1,3-dithiol derivatives to aromatic dithiols is (1-3):(1-7), preferably 1:1.

[0012] According to some embodiments of the present invention, the 1,3-dithiol derivative is selected from at least one of 1,3-dithiol-2-thione-4,5-dithiol (DMIT), 1,3-dithiol-2-one-4,5-dithiol (DMID), and 1,3-dithiol-2-imine-4,5-dithiol (DSDT); preferably 1,3-dithiol-2-thione-4,5-dithiol (DMIT).

[0013] According to some embodiments of the present invention, the aromatic dithiol is selected from at least one of benzene-1,2-dithiol (BDT), toluene-3,4-dithiol (TDT), and 3,6-dichlorobenzene-1,2-dithiol (Cl2BDT); preferably benzene-1,2-dithiol (BDT) and / or 3,6-dichlorobenzene-1,2-dithiol (Cl2BDT), and most preferably 3,6-dichlorobenzene-1,2-dithiol (Cl2BDT).

[0014] According to some embodiments of the present invention, the aliphatic bidentate dithiol is selected from at least one of 1,2-ethanedithiol (EDT), 1,3-propanedithiol (PDT), 1,4-butanedithiol, and 2,3-butanedithiol.

[0015] According to some embodiments of the present invention, the cyclic bidentate dithiol is selected from 1,2-benzodithiol and / or dithiothreitol (DTT).

[0016] According to some embodiments of the present invention, the substituted bidentate dithiol is selected from 2,2-dimethyl-1,3-propanedithiol (DMPDT) and / or 4-methyl-1,2-benzenedithiol (MBDT).

[0017] According to some embodiments of the present invention, the concentration of the solution containing bidentate dithiol ligands is 0.1 g / L to 100 g / L, preferably 5 g / L to 15 g / L, for example 10 g / L.

[0018] According to some embodiments of the present invention, the sulfide solid electrolyte is selected from at least one of argentite-germanium sulfide solid electrolyte, lithium thiosulfate superionic conductor sulfide solid electrolyte, glassy sulfide solid electrolyte, and crystalline sulfide solid electrolyte; preferably, the chemical formula of the argentite-germanium sulfide solid electrolyte is Li. 7-(a+b) PS 6-(a+b) X a Y b Where X and Y are the same or different, each independently being Cl or Br, and 0 ≤ a + b ≤ 1.7; and / or the chemical formula of the lithium thioate superionic conductor sulfide solid electrolyte is Li 10 SnP2S 12 Or Li 10 GeP2S 12 ; and / or, the glassy sulfide solid electrolyte has the chemical formula Li3PS4 or Li 3.2 PS4I 0.2 ; and / or, the chemical formula of the crystalline sulfide solid electrolyte is Li7P3S 11 .

[0019] According to some embodiments of the present invention, the mass ratio of the solution containing bidentate dithiol ligands to the sulfide solid electrolyte is 10:(1-5), for example 10:1, 10:2, 10:3, 10:4, 10:5.

[0020] In this invention, there are no special requirements for the preparation of solutions containing bidentate dithiol ligands, and all methods are conventional techniques in the art. For example, in some embodiments of this invention, the preparation of the solution containing bidentate dithiol ligands includes: mixing the bidentate dithiol ligands with an organic solvent to obtain the solution containing the bidentate dithiol ligands; wherein the solvent is selected from at least one of n-hexane, cyclohexane, toluene, ethylbenzene, p-xylene, isobutyl isobutyrate, acetone, butyl acetate, amyl valerate, and methyl tert-butyl ether; the mixing conditions include: a temperature of 30℃ to 55℃, preferably 35℃ to 45℃, for example 40℃; a time of 20min to 140min, preferably 40min to 100min, for example 90min; a stirring rate of 100r / min to 5000r / min, preferably 600r / min to 1000r / min, for example 800r / min; and a heating rate of 3℃ / min to 4℃ / min.

[0021] In this invention, the mixing and stirring method for preparing solutions containing bidentate dithiol ligands is not particularly limited, and all are conventional techniques in the art. For example, the stirring methods can be: ① magnetic stirring: rotation speed 600 r / min to 2000 r / min, stirring time 60 min to 120 min, heating temperature 30℃ to 50℃; ② planetary stirring: revolution speed 100 r / min to 150 r / min, rotation speed 600 r / min to 900 r / min, stirring time 60 min to 120 min, heating temperature 30℃ to 50℃; ③ high-speed shear stirring: rotation speed 3000 r / min to 5000 r / min, stirring time 20 min to 40 min, heating temperature 35℃ to 55℃; ④ double planetary stirring: revolution speed 150 r / min to 250 r / min, rotation speed 800 r / min to 1200 r / min, stirring time 80 min to 140 min, heating temperature 30℃ to 50℃.

[0022] In this invention, the preparation of the solution containing bidentate dithiol ligands is carried out in an anhydrous environment throughout the process, and the first solvent is an anhydrous solvent.

[0023] According to some embodiments of the present invention, the inert atmosphere is selected from at least one of argon, nitrogen, and helium. The inert atmosphere is an anhydrous inert atmosphere.

[0024] According to some embodiments of the present invention, the reaction conditions include: a temperature of 30°C to 80°C, preferably 32°C to 40°C, such as 32°C, 35°C, or 40°C; a time of 0.5h to 2h, preferably 1h to 1.5h, such as 1h or 1.5h; and a stirring rate of 100r / min to 3000r / min.

[0025] In this invention, when a solution containing bidentate dithiol ligands reacts with a sulfide solid electrolyte, the coordination reaction is accelerated by increasing the temperature, thus shortening the coating time of the monomolecular coating layer. Stirring ensures sufficient coordination between the ligands and the active sites on the surface of the sulfide solid electrolyte, forming a monomolecular coating layer (ligand protective layer) (one active site on the electrolyte surface corresponds to one bidentate dithiol, which is determined to be a monomolecular coating layer based on the reaction principle). There are no particular limitations on the stirring method; all methods are conventional techniques in the field. For example, the stirring method can be: ① magnetic stirring: rotation speed 600 r / min~1000 r / min. ① Time: 0.5h to 3h; ② Planetary stirring: revolution speed 100r / min to 3000r / min, preferably 100r / min to 1000r / min, for example 100r / min or 150r / min, rotation speed 120r / min to 480r / min, for example 120r / min or 480r / min, stirring time 0.5h to 3h; ③ Ball milling: use zirconia balls (ball diameter 0.5mm to 2mm), ball-to-material ratio 5:1 to 10:1, stirring speed 300r / min to 600r / min, stirring time 0.5h to 3h.

[0026] According to some embodiments of the present invention, during the reaction, the heating rate is 2°C / min to 5°C / min to avoid local overheating.

[0027] According to some embodiments of the present invention, the preparation method further includes: performing post-processing after the reaction; the post-processing includes: performing solid-liquid separation on the product obtained from the reaction to obtain a solid product, and washing the solid product; specifically, the post-processing includes: performing vacuum filtration on the mixed system (product) obtained from the reaction, collecting the solid product, and completing the preliminary solid-liquid separation. The solid product was then cleaned with a solvent, using the following method: A solvent identical to that used in the ligand solution was selected to avoid introducing new solvent impurities. This ensured that the solvent only dissolved uncoordinated residual ligands in the solid product, without disrupting the monomolecular coating structure formed by the bidentate dithiol ligands and the electrolyte surface, and without causing side reactions with the sulfide solid electrolyte. The number of cleaning cycles was controlled to 1-3 times, with 200-500g of cleaning solvent per 100g of solid product. Cleaning could be performed using stirring or ultrasonic cleaning: ① Magnetic stirring: rotation speed 200-800r / min, time 5-10min; ② Planetary stirring: revolution speed 50-100r / min, rotation speed 200-400r / min, time 5-8min; Ultrasonic cleaning parameters: power 100W-200W, time 3-5min. After cleaning, vacuum filtration is performed again to collect the solid product. After filtration, the product is quickly transferred to a vacuum drying device and vacuum dried at 70℃~90℃ for 4h~6h to obtain the modified sulfide solid electrolyte.

[0028] A second aspect of the present invention provides a modified sulfide solid electrolyte prepared by the preparation method provided in the first aspect above.

[0029] A third aspect of the present invention provides a sulfide solid electrolyte membrane, comprising a sulfur-containing binder and a modified sulfide solid electrolyte; The modified sulfide solid electrolyte is either the modified sulfide solid electrolyte prepared by the preparation method described in the first aspect or the modified sulfide solid electrolyte provided in the second aspect.

[0030] According to some embodiments of the present invention, based on the mass of the sulfide solid electrolyte membrane as 100%, the mass content of the sulfur-based binder is 2% to 10%, preferably 2% to 5%, for example 2%, 3%, 4%, 5%; and the mass content of the modified sulfide solid electrolyte is 90% to 98%, preferably 95% to 98%, for example 95%, 96%, 97%, 98%.

[0031] This invention uses bidentate dithiol coordination chemistry to form a monomolecular coating layer to improve the air stability of sulfide electrolytes. At the same time, the resulting modified sulfide solid electrolyte and sulfur-containing binder system (polyethylene glycol disulfide, polythiourea, polysulfide polyurethane) form a chemical synergistic effect.

[0032] A fourth aspect of the present invention provides a method for preparing the sulfide solid electrolyte membrane provided in the third aspect above, comprising: A modified sulfide solid electrolyte, a sulfur-based binder, and a solvent are mixed to obtain an electrolyte slurry. The electrolyte slurry is coated on the substrate to obtain a preliminary film-forming product. The preliminary film-forming product is then hot-pressed to obtain the sulfide solid electrolyte membrane.

[0033] According to some embodiments of the present invention, the solvent is selected from at least one of diethylene glycol dimethyl ether, tetrahydrofuran, ethyl tert-butyl ether, dipropylene glycol dimethyl ether, ethyl butyrate, isobutyl isovalerate, isobutyl isobutyrate, methyl hexanoate, anhydrous methyl isobutyl ketone, acetone, 3-pentanone, 4-heptanone, ethylcyclohexane, p-xylene, and decahydronaphthalene.

[0034] According to some embodiments of the present invention, the sulfur-containing binder is selected from at least one of polyethylene glycol disulfide (number average molecular weight of 1000-5000 Da, preferably 5000 Da), polyhexamethylene diamine-carbon disulfide type polythiourea (number average molecular weight of 2000-8000 Da, preferably 4000 Da), and polysulfide polyurethane (number average molecular weight of 1500-6000 Da, preferably 6000 Da); preferably polyethylene glycol disulfide and / or polyhexamethylene diamine-carbon disulfide type polythiourea, most preferably polyhexamethylene diamine-carbon disulfide type polythiourea.

[0035] According to some embodiments of the present invention, the solid content of the electrolyte slurry is 10% to 50%, preferably 30% to 45%, such as 30%, 35%, 40%, etc.

[0036] According to some embodiments of the present invention, the mixing conditions include: a temperature of 25℃ to 40℃, a time of 30 min to 90 min, and a stirring rate of 100 r / min to 1800 r / min. During the mixing process described in this invention, a dual planetary stirring method is used to achieve uniform mixing and obtain a slurry with excellent dispersibility. The unified parameters for the dual planetary stirring are: revolution speed of 100 r / min to 200 r / min, preferably 120 r / min to 180 r / min, for example, 120 r / min, 150 r / min, or 180 r / min; rotation speed of 800 r / min to 1800 r / min, preferably 1000 r / min to 1300 r / min, for example, 1000 r / min, 1200 r / min, or 1300 r / min; stirring time of 30 min to 90 min, preferably 40 min to 80 min, for example, 40 min, 60 min, or 80 min; and the system temperature is controlled at 25℃ to 40℃ during the stirring process, for example, 25℃ or 30℃.

[0037] According to some embodiments of the present invention, the substrate is selected from at least one of PTFE film, polyimide film, aluminum foil, and stainless steel foil.

[0038] According to some embodiments of the present invention, the hot pressing conditions include: a temperature of 80°C to 150°C, preferably 90°C to 110°C, such as 90°C, 100°C, or 110°C; a time of 1 hour to 2 hours, such as 1 hour, 1.5 hours, or 2 hours; and a pressure of 1 MPa to 20 MPa, preferably 5 MPa to 15 MPa, such as 5 MPa, 7 MPa, 8 MPa, or 15 MPa.

[0039] In this invention, the hot pressing is carried out using a flat plate hot pressing method. After the film layer vulcanization is completed by hot pressing, it is cooled to room temperature.

[0040] According to some embodiments of the present invention, the thickness of the sulfide solid electrolyte membrane is 10 μm to 100 μm, preferably 20 μm to 40 μm, for example 20 μm, 30 μm, 40 μm.

[0041] In this invention, the preparation of the sulfide solid electrolyte membrane is carried out entirely in an anhydrous environment. The electrolyte slurry is coated on the substrate and dried at room temperature in an anhydrous inert atmosphere to obtain a preliminary film-forming product.

[0042] In this invention, based on the hard-soft acid-base theory (HSAB) and molecular coordination chemistry, a precise surface modification of anhydrous and oxygen-free sulfide solid electrolytes is achieved using bidentate dithiol ligands and weakly polar anhydrous organic solvents such as n-hexane. The molding process of the sulfide solid electrolyte membrane is optimized by combining it with a sulfur-based binder. By utilizing the sulfur-based binder and the monomolecular coating layer to form sulfur bridges, a synergistic system of "ligand protective layer - sulfur bridge - sulfur-based binder - air-stabilized sulfide solid electrolyte - dense membrane structure" is constructed, simultaneously addressing the core technical challenges of sulfide solid electrolytes.

[0043] In this invention, the precise coordination between the ligand and the sulfide solid electrolyte occurs because the surface of the sulfide solid electrolyte contains a large number of coordinally unsaturated soft acid sites (Li). + P 5+ ) and highly active soft base groups (S 2- PS4 3-Bidentate dithiol ligands include, but are not limited to, 1,3-dithiol derivatives, aromatic dithiols, aliphatic bidentate dithiols, cyclic bidentate dithiols, and substituted bidentate dithiols. They can be used alone or in combination, and all can achieve a strong anchoring through specific coordination. Among them, aromatic dithiol ligands deprotonate to form dithiolate salts, forming a stable five-membered chelate ring with the active site on the electrolyte surface. The binding energy is significantly improved compared to monothiols. At the same time, the conjugated structure regulates the electron cloud distribution and inhibits oxidative hydrolysis. 1,3-dithiol derivative ligands form multi-point coordination through the dithiol structure. Substituent modification can regulate redox activity and avoid excessive reaction. Aliphatic bidentate dithiols, cyclic bidentate dithiols, and substituted bidentate dithiol ligands bind to the active site on the electrolyte surface through the two end thiol groups or multiple coordination sites to form a stable bidentate coordination structure, which is suitable for different coordination environments. In this invention, bidentate coordination can achieve full coverage of the monomolecular coating layer without damaging the bulk structure or blocking ion channels; the selected weakly polar organic solvent is suitable for the dissolution and coordination reactions of various bidentate dithiol ligands, avoiding side reactions between the solvent and the electrolyte.

[0044] In this invention, the monomolecular coating layer provides multiple protective functions: the monomolecular coating layer forms a dense hydrophobic interface through hydrophobic groups, blocking water vapor and oxygen; and by occupying the active sites on the electrolyte surface, it achieves passivation, reducing interfacial side reactions and lowering interfacial impedance.

[0045] In this invention, the molding and performance of the sulfide solid electrolyte membrane are synergistic: ligand coating reduces electrolyte particle aggregation and improves dispersibility and interfacial compatibility; the π-π stacking of aromatic dithiols in the bidentate dithiol ligand enhances particle binding force, and the flexible framework of the 1,3-dithiol derivative improves toughness; combined with a sulfur-containing binder, the sulfur groups in its molecule form stable sulfur bridges (SS bonds) with the thiol groups remaining on the surface of the bidentate dithiol ligand monomolecular coating layer, significantly improving the toughness and mechanical stability of the sulfide solid electrolyte membrane and preventing membrane cracking.

[0046] The fifth aspect of the present invention provides an all-solid-state battery, comprising the sulfide solid electrolyte membrane provided in the third aspect above or the sulfide solid electrolyte membrane prepared by the preparation method provided in the fourth aspect above.

[0047] Beneficial effects: The modified sulfide solid electrolyte prepared by this invention has significantly improved air stability: the monomolecular coating layer formed by the bidentate dithiol ligand can effectively block water vapor and oxygen. After the modified sulfide solid electrolyte is ground and exposed in a -45℃ dew point drying room for 30 minutes, the ionic conductivity retention rate is ≥90%. Processing and assembly can be completed without an inert atmosphere, which greatly reduces production and transportation costs. The sulfide solid electrolyte membrane prepared by this invention exhibits excellent synergistic performance in ionic conductivity and mechanical properties: the monomolecular coating layer does not block ion transport channels, and after being exposed to the environment of a -45°C dew point drying chamber for 30 minutes, the room temperature ionic conductivity of the electrolyte membrane after exposure to the -45°C dew point remains above 1 mS / cm; the sulfur bridge formed by the sulfur-containing binder and the monomolecular coating layer can strengthen the interfacial bonding, and combined with the flexible effect of the ligand, the electrolyte membrane has both good compactness and excellent toughness. The sulfide solid electrolyte membrane prepared by this invention has excellent interfacial compatibility: the ligands passivate the active sites on the surface of the sulfide solid electrolyte, reduce interfacial side reactions with the positive and negative electrode materials, reduce interfacial impedance, and improve the cycle life and rate performance of the all-solid-state battery. The sulfide solid electrolyte membrane of the present invention has a simple process and is suitable for industrialization: modification and film formation can be completed without complex equipment, and the bidentate dithiol ligand and sulfur-containing binder are widely available and low in cost, enabling large-scale production and meeting the application requirements of all-solid-state lithium batteries for vehicle power and large-scale energy storage. Attached Figure Description

[0048] Figure 1 These are comparative photographs of the solid electrolytes prepared in Preparation Example 1 and Comparative Preparation Example 2 of this invention after being ground and exposed to a dew point drying room at -45°C for 30 minutes.

[0049] Figure 2 This is a comparison of XRD patterns of the solid electrolytes prepared in Preparation Example 1 and Comparative Preparation Example 2 of the present invention after being ground and exposed in a -45°C dew point drying room for 30 minutes.

[0050] Figure 3 This is a SEM comparison image of the solid electrolytes prepared in Preparation Example 1 and Comparative Preparation Example 2 of the present invention after being ground and exposed in a -45°C dew point drying room for 30 minutes. Detailed Implementation

[0051] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0052] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of the present invention are commercially available.

[0053] Unless otherwise specified, the ambient temperature / room temperature conditions described in the embodiments and comparative examples of this invention are all 25°C.

[0054] In the embodiments and comparative examples of the present invention, the preparation methods are all carried out in an anhydrous environment; in the embodiments and comparative examples of the present invention, the solvents are all anhydrous solvents.

[0055] Preparation Example 1 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. Ligand solution preparation: 1,3-dithiol-2-thione-4,5-dithiol (DMIT) and benzene-1,2-dithiol (BDT) were mixed at a mass ratio of 1:1 and added to anhydrous acetone to prepare a 10 g / L (0.061 mol g / L) ligand solution. The solution was prepared by magnetic stirring at a speed of 800 r / min, while simultaneously heating to 40 °C at a heating rate of 3 °C / min. The mixture was stirred for 90 min until the ligand was completely dissolved and the system was homogeneous, thus obtaining the ligand solution.

[0056] Surface modification: 100g of Li6PS5Cl electrolyte was added to the ligand solution, and the mass ratio of the ligand solution to the sulfide solid electrolyte was controlled at 10:3. The mixture was stirred by planetary stirring at 35℃ under an argon atmosphere with a revolution speed of 100r / min and a rotation speed of 120r / min for 1h to complete the coordination reaction.

[0057] Post-processing: The solid product was collected by vacuum filtration, with an argon atmosphere maintained throughout the process. Anhydrous acetone, consistent with the ligand solution, was used for washing. Specifically, 1.5 times the mass of the solid product was added to the solid product, and the mixture was placed in an argon-protected reaction vessel and stirred at 300 rpm for 8 minutes to ensure that any uncoordinated residual ligands were fully dissolved in the acetone. Immediately after stirring, vacuum filtration was performed to separate the washing solution from the solid product. This washing process was repeated three times. The solid product was then transferred to a vacuum drying apparatus and vacuum dried at 70°C for 6 hours to completely remove residual acetone, yielding a monomolecular coated modified sulfide solid electrolyte (Li6PS5Cl type).

[0058] Preparation Example 2 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. Ligand solution preparation: 1,3-dithiol-2-thione-4,5-dithiol (DMIT) and benzene-1,2-dithiol (BDT) were mixed at a mass ratio of 1:1 and added to anhydrous acetone to prepare a 10 g / L (0.061 mol g / L) ligand solution. The solution was prepared by magnetic stirring at a speed of 800 r / min, while simultaneously heating to 40 °C at a heating rate of 3 °C / min. The mixture was stirred for 90 min until the ligand was completely dissolved and the system was homogeneous, thus obtaining the ligand solution.

[0059] Surface modification: 100g of Li3PS4 electrolyte was added to the ligand solution, and the mass ratio of the ligand solution to the sulfide solid electrolyte was controlled at 10:1. The mixture was stirred magnetically at 800r / min for 1h under a nitrogen atmosphere and at 32℃ to complete the coordination reaction.

[0060] Post-processing: Solid products were collected by vacuum filtration, with a nitrogen atmosphere maintained throughout. Anhydrous acetone, consistent with the ligand solution, was used for washing. Specifically, 1.5 times the volume of anhydrous acetone was added to the solid product, and the mixture was placed in a nitrogen-protected reaction vessel. The mixture was magnetically stirred at 250 r / min for 6 min to dissolve the uncoordinated residual ligands. After stirring, the mixture was vacuum filtered to separate the washing liquid from the solid product, completing two washing cycles. The solid product was then transferred to a vacuum drying apparatus and vacuum dried at 70°C for 6 h to completely remove residual acetone, yielding a monomolecular coated modified sulfide solid electrolyte (Li3PS4 type).

[0061] Preparation Example 3 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. Ligand solution preparation: 1,3-dithiol-2-thione-4,5-dithiol (DMIT) and benzene-1,2-dithiol (BDT) were mixed at a mass ratio of 1:1 and added to anhydrous acetone to prepare a 10 g / L (0.061 mol g / L) ligand solution. The solution was prepared by magnetic stirring at a speed of 800 r / min, while simultaneously heating to 40 °C at a heating rate of 3 °C / min. The mixture was stirred for 90 min until the ligand was completely dissolved and the system was homogeneous, thus obtaining the ligand solution.

[0062] Surface modification: 100g of mixed sulfide solid electrolyte, which is a mixture of Li3PS4 and Li6PS5Cl at a mass ratio of 3:1, was added to the ligand solution. The mass ratio of the ligand solution to the sulfide solid electrolyte was controlled to be 10:4. The mixture was stirred for 1.5h under an argon atmosphere and at 40℃ using a planetary stirrer with a revolution speed of 150r / min and a rotation speed of 480r / min to complete the coordination reaction.

[0063] Post-processing: Solid products were collected by vacuum filtration, with an argon atmosphere maintained throughout. Anhydrous acetone, consistent with the ligand solution, was used for cleaning. The specific procedure was as follows: cleaning was performed twice, with twice the mass of the solid product in anhydrous acetone added each time. After each addition, the product was placed in an ultrasonic cleaner with the following parameters: power 200W, time 5min, to fully dissolve the uncoordinated residual ligands. Vacuum filtration was performed after each stirring to separate the cleaning solution from the solid product. After the second cleaning and filtration, the solid product was transferred to a vacuum drying device and vacuum dried at 90℃ for 4h to completely remove residual acetone, yielding a monomolecular coated modified sulfide solid electrolyte (a mixture of Li3PS4 and Li6PS5Cl).

[0064] Preparation Example 4 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. The preparation method is the same as in Preparation Example 1, except that only 1,3-dithiol-2-one-4,5-dithiol (DMID) is selected as the bidentate dithiol ligand in the preparation of the ligand solution, and the molar concentration of the ligand solution is the same as in Preparation Example 1.

[0065] Preparation Example 5 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. The preparation method is the same as in Preparation Example 1, except that only benzene-1,2-dithiol (BDT) is selected as the bidentate dithiol ligand when preparing the ligand solution, and the molar concentration of the ligand solution is the same as in Preparation Example 1.

[0066] Preparation Example 6 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. The preparation method is the same as in Preparation Example 1, except that 3,6-dichlorobenzene-1,2-dithiol (Cl2BDT) is used instead of 1,3-dithiol-2-thione-4,5-dithiol (DMIT) and benzene-1,2-dithiol (BDT) in the preparation of the ligand solution. The molar concentration of the ligand solution is the same as in Preparation Example 1.

[0067] Preparation Example 7 This preparation example illustrates the modified sulfide solid electrolyte and its preparation method described in this invention. The preparation method is the same as in Preparation Example 1, except that the mass ratio of 1,3-dithiol-2-thione-4,5-dithiol (DMIT) to benzene-1,2-dithiol (BDT) is 3:7, and the molar concentration of the ligand solution is 0.064 mol / L.

[0068] Comparative Preparation Example 1 The preparation method is the same as in Preparation Example 1, except that monothiol ligand (benzenethiophenol) is used instead of 1,3-dithiol-2-thione-4,5-dithiol (DMIT) and benzene-1,2-dithiol (BDT) in the preparation of the ligand solution. The molar concentration of the ligand solution is the same as in Preparation Example 1.

[0069] Comparative Preparation Example 2 The preparation method is the same as in Preparation Example 1, except that no ligand coating modification is performed, as detailed below: 100g of Li6PS5Cl electrolyte was directly added to anhydrous acetone, controlling the mass ratio of anhydrous acetone to sulfide solid electrolyte to be 10:3. Under an argon atmosphere and at 35℃, a planetary stirrer was used with a revolution speed of 100 r / min and a rotation speed of 120 r / min. After stirring for 1 hour, the solid product was collected by vacuum filtration, maintaining an argon atmosphere throughout. Anhydrous acetone was used for washing. Specifically, 1.5 times the mass of the solid product was added to the solid product, and the mixture was placed in an argon-protected reaction vessel and stirred at 300 r / min for 8 minutes. After stirring, vacuum filtration was immediately performed to separate the washing liquid from the solid product. This washing process was repeated three times. The solid product was then transferred to a vacuum drying device and vacuum dried at 70℃ for 6 hours to completely remove residual acetone, yielding the unmodified sulfide solid electrolyte (Li6PS5Cl type).

[0070] Comparative preparation example 3 The preparation method is the same as in Preparation Example 1, except that 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithioundecane is used to replace 1,3-dithiol-2-thione-4,5-dithiol (DMIT) and benzene-1,2-dithiol (BDT) in the preparation of the ligand solution, and the molar concentration of the ligand solution is the same as in Preparation Example 1.

[0071] Example 1 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. Preparation of monomolecular coating layer-coated sulfide solid electrolyte membrane: The monomolecular coating layer-coated modified sulfide solid electrolyte prepared in Preparation Example 1 was mixed with polyethylene glycol disulfide (number average molecular weight 5000 Da) at a mass ratio of 97:3. The total solid mass (the sum of the masses of the monomolecular coating layer-coated modified sulfide solid electrolyte and polyethylene glycol disulfide) was calculated. Anhydrous acetone was added to control the solid content of the system to 30%. A dual planetary stirrer was used with a revolution speed of 150 r / min and a rotation speed of 1200 r / min, and stirred at 25°C for 60 min to prepare a uniform slurry. The slurry was coated onto a PTFE membrane and dried at room temperature in an argon atmosphere to obtain a preliminary film-forming product. The PTFE membrane with the preliminary film-forming product attached was placed in a mold and hot-pressed at 100°C and 15 MPa for 1.5 h. After cooling to room temperature, the PTFE membrane was peeled off to obtain a monomolecular coating layer-coated sulfide solid electrolyte membrane with a thickness of 30 μm.

[0072] Example 2 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. Preparation of monomolecular coating layer coated sulfide solid electrolyte membrane: The monomolecular coating layer coated modified sulfide solid electrolyte prepared in Preparation Example 2 was mixed with polyhexamethylenediamine-carbon disulfide type polythiourea (number average molecular weight 4000 Da) at a mass ratio of 98:2. The total solid mass (the sum of the mass of the monomolecular coating layer coated modified sulfide solid electrolyte and the mass of polyhexamethylenediamine-carbon disulfide type polythiourea) was calculated. Anhydrous p-xylene was added to control the solid content of the system to 45%. A dual planetary stirrer was used with a revolution speed of 120 r / min and a rotation speed of 1000 r / min. The mixture was stirred at 30°C for 40 min to prepare a uniform slurry. The slurry was coated on a stainless steel foil substrate and dried at room temperature in a nitrogen atmosphere to obtain a preliminary film-forming product. The copper foil substrate with the preliminary film-forming product was placed in a mold and hot-pressed at 90°C and 7 MPa for 2 h. After cooling to room temperature, a monomolecular coating layer coated sulfide solid electrolyte membrane with a thickness of 20 μm was obtained.

[0073] Example 3 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. Preparation of monomolecular coating layer-coated sulfide solid electrolyte membrane: The monomolecular coating layer-coated modified sulfide solid electrolyte prepared in Preparation Example 3 was mixed with polysulfide polyurethane (number average molecular weight 6000 Da) at a mass ratio of 96:4. The total solid mass (the sum of the mass of the monomolecular coating layer-coated modified sulfide solid electrolyte and the polysulfide polyurethane) was calculated. Anhydrous isobutyl isobutyrate was added, and the solid content of the system was controlled to be 30%. A double planetary stirrer was used with a revolution speed of 180 r / min and a rotation speed of 1300 r / min. The mixture was stirred at 30°C for 80 min to prepare a uniform slurry. The slurry was coated on a polyimide substrate and dried at room temperature in an argon atmosphere to obtain a preliminary film-forming product. The polyimide substrate with the preliminary film-forming product attached was placed in a mold and hot-pressed at 110°C and 8 MPa for 1 h. After cooling to room temperature, a monomolecular coating layer-coated sulfide solid electrolyte membrane with a thickness of 40 μm was obtained.

[0074] Example 4 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 3 is used instead of the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 1.

[0075] Example 5 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 4 is used instead of the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 1.

[0076] Example 6 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 5 is used instead of the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 1.

[0077] Example 7 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 6 is used instead of the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 1.

[0078] Example 8 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 7 is used instead of the modified sulfide solid electrolyte with a monomolecular coating layer prepared in Preparation Example 1.

[0079] Example 9 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that an equal mass of polyhexamethylenediamine-carbon disulfide type polythiourea (number average molecular weight of 4000 Da) is used instead of polyethylene glycol disulfide.

[0080] Example 10 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the sulfur-containing binder uses a combination of polyhexamethylenediamine-carbon disulfide type polythiourea (number average molecular weight of 4000 Da) and polyethylene glycol disulfide (number average molecular weight of 5000 Da) in a mass ratio of 2:8.

[0081] Example 11 This embodiment is used to illustrate the sulfide solid electrolyte membrane and its preparation method described in this invention. The preparation method is the same as in Example 1, except that the sulfur-containing binder uses a combination of polyhexamethylenediamine-carbon disulfide type polythiourea (number average molecular weight of 4000 Da) and polyethylene glycol disulfide (number average molecular weight of 5000 Da) in a mass ratio of 8:2.

[0082] Comparative Example 1 The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte prepared in Comparative Preparation Example 1 is used instead of the monomolecular coating layer-coated modified sulfide solid electrolyte prepared in Preparation Example 1.

[0083] Comparative Example 2 The preparation method is the same as in Example 1, except that the unmodified sulfide solid electrolyte prepared in Comparative Preparation Example 2 is used instead of the monomolecular coating layer-coated modified sulfide solid electrolyte prepared in Preparation Example 1.

[0084] Comparative Example 3 The preparation method is the same as in Example 1, except that the modified sulfide solid electrolyte prepared in Comparative Preparation Example 3 is used instead of the monomolecular-coated modified sulfide solid electrolyte prepared in Preparation Example 1.

[0085] Comparative Example 4 The preparation method is the same as in Example 1, except that an equal mass of non-sulfur-based binder (polyvinylidene fluoride PVDF, weight-average molecular weight of 600,000 Da) is used to replace the polyethylene glycol disulfide in Example 1.

[0086] Comparative Example 5 The preparation method is the same as in Example 1, except that the sulfur-containing binder uses a combination of polyhexamethylenediamine-carbon disulfide type polythiourea (number average molecular weight of 4000 Da) and polyethylene glycol disulfide in a mass ratio of 1:9.

[0087] To further verify the further development of the modified sulfide solid electrolyte and sulfide solid electrolyte membrane described in this invention, the modified (or unmodified) sulfide solid electrolyte prepared in the above preparation examples and comparative preparation examples, as well as the sulfide solid electrolyte membrane prepared in the examples and comparative examples, were tested as follows.

[0088] Test Example 1: The steps for testing the room temperature ionic conductivity of electrolytes are as follows: (1) In a glove box with water and oxygen concentrations less than 0.1 ppm, 100 mg of the sulfide solid electrolyte (powder) prepared in the above preparation examples 1-7 and comparative preparation examples 1-3 of the present invention were weighed and placed into a solid mold battery with a diameter of 10 mm. The battery was pressed at a pressure of 500 MPa for 2 min to form a SUS|SSE|SUS blocking battery, and a test pressure of 5 MPa was applied. (2) An electrochemical workstation was used to perform AC impedance testing. The test frequency range was 107 Hz to 0.1 Hz, the AC amplitude was 10 mV, and the temperature was 25 ℃. When the Nyquist plot only shows a linear characteristic, the intersection point with the real axis corresponds to the total impedance of the material; when the Nyquist plot has a semi-circular characteristic, the real axis coordinate of the intersection point of the semi-circle and the straight line is the total impedance of the material. (3) The room temperature ionic conductivity is calculated using the following formula: σ = L / (R × S) Where σ is the ionic conductivity, in S / cm; L is the sample thickness (blocking electrode thickness), in cm; R is the total resistance, in Ω; and S is the effective contact area between the electrode and the electrolyte, in cm². 2 .

[0089] Test Example 2 The following are the steps for testing the retention rate of ionic conductivity of electrolytes after exposure to a dew point of -45°C: Using an analytical balance, 10g of the sulfide solid electrolytes prepared in Preparation Examples 1-7 and Comparative Preparation Examples 1-3 of the present invention were weighed and placed in a mortar. After grinding and exposing to the environment of a dew point drying room at -45°C for 30min, the ionic conductivity was tested according to the steps of Test Example 1. The ionic conductivity after exposure to the dew point at -45°C is obtained. Ionic conductivity retention rate = (ionic conductivity after exposure to dew point at -45℃ ÷ ionic conductivity at room temperature) × 100%.

[0090] Test Example 3 Electrolyte electronic conductivity test after exposure to dew point at -45℃: The test procedure is as follows: (1) Using an analytical balance, 10g of the sulfide solid electrolytes prepared in Preparation Examples 1-7 and Comparative Preparation Examples 1-3 of the present invention were weighed and placed in a mortar, and ground for 30min at a dew point of -45℃; among them, the photographs, XRD and SEM images of the solid electrolytes prepared in Preparation Example 1 of the present invention and Comparative Preparation Example 2 after being ground and exposed in a dew point drying room at -45℃ for 30min are shown in the figure. Figure 1 , Figure 2 and Figure 3 ; (2) In a glove box with water and oxygen concentration less than 0.1 ppm, weigh 100 mg of sulfide solid electrolyte powder that has been ground and exposed for 30 min in a dew point drying room at -45℃ and put it into a solid mold battery with a diameter of 10 mm. Press it with a pressure of 500 MPa for 2 min to form a SUS|SSE|SUS blocking battery and apply a test pressure of 5 MPa.

[0091] (3) The electrochemical workstation was used to conduct the test using the chronoamperometry method. The test temperature was 25℃, the applied voltage was 30mV, and the test time was 3600s. The average current in the steady state was taken as the steady electron current.

[0092] (4) The electronic conductivity after exposure to a dew point of -45℃ is calculated using the following formula: σ e =(I×L) / (V×S) Where, σ e The values ​​are: I = electronic conductivity (S / cm); L = stable electronic current (A); L = sample thickness (cm); V = applied voltage (V); S = effective contact area between electrode and electrolyte (cm²). 2 .

[0093] Test Example 4 The limiting current density test of electrolyte after exposure to dew point at -45℃ is performed using the following steps: (1) Using an analytical balance, weigh 10g of the sulfide solid electrolytes prepared in the above preparation examples 1-7 and comparative preparation examples 1-3 of the present invention and place them in a mortar. Grind and expose them for 30min in a dew point drying room at -45℃. (2) In a glove box with water and oxygen concentration less than 0.1 ppm, weigh 100 mg of sulfide solid electrolyte powder that has been ground and exposed for 30 min in a dew point drying room at -45℃ and put it into a solid mold battery with a diameter of 10 mm. Press it with a pressure of 500 MPa for 2 min, and then place lithium metal foil with a diameter of 10 mm and a thickness of 50 μm on both sides to form a Li|SSE|Li symmetric battery and apply a test pressure of 5 MPa. (3) At a constant temperature of 25°C, the battery testing system was used to apply increasing currents of 0.1, 0.2, 0.3, 0.4, and 0.5 mA / cm in sequence. 2 Under DC current density, each current density was maintained for 10 to 20 minutes, and the voltage response was recorded in real time; (4) When the voltage rises significantly and exceeds 100mV, the corresponding current density is the limiting current density.

[0094] The test results of test examples 1-4 above are shown in Table 1.

[0095] Table 1

[0096] In this invention, the sulfide solid electrolytes prepared in Preparation Examples 1-7 and Comparative Preparation Examples 1-3 were all powders, meaning all test samples were sulfide solid electrolyte powders. The results showed that the room temperature ionic conductivity of the sulfide solid electrolytes prepared in Preparation Examples 1-7 remained between 4.28 mS / cm and 4.67 mS / cm, essentially the same as that of the unmodified Comparative Preparation Example 2 (4.67 mS / cm). This demonstrates that the bidentate dithiol surface modification does not disrupt the bulk ion transport channels of the electrolyte. Furthermore, after grinding and exposure in a -45°C dew point drying chamber for 30 minutes, the ionic conductivity remained between 4.11 mS / cm and 4.48 mS / cm (ionic conductivity retention ≥90%), while the electronic conductivity was only between 4.31 nS / cm and 6.01 nS / cm, with a limiting current density of 4.12 mA / cm. 2 ~4.92mA / cm 2 Among them, Preparation Example 6, modified with a single 3,6-dichlorobenzene-1,2-dithiol (Cl2BDT), showed the best limiting current density, while Preparation Example 4, modified with a single 1,3-dithiol-2-one-4,5-dithiol (DMID), exhibited the highest ionic conductivity at room temperature. In contrast, the unmodified Preparation Example 2, after being ground and exposed in a -45°C dew point drying room for 30 minutes, showed a sharp drop in ionic conductivity to 2.28 mS / cm (ionic conductivity retention rate of only 48.82%), while electronic conductivity soared to 1000.73 nS / cm, with a limiting current density of only 1.29 mA / cm. 2 In the comparative preparation example 1 of the monothiol-benzenethiophenol modification, after grinding and exposure for 30 min in a -45°C dew point drying room, the ionic conductivity plummeted to 3.19 mS / cm (ionic conductivity retention rate was only 73.84%), while the electronic conductivity increased to 147.14 S / cm, with a limiting current density of only 1.32 mA / cm. 2 In contrast, in Comparative Preparation Example 3, which used bidentate dithiol ligands not selected in this invention, the ionic conductivity plummeted to 3.07 mS / cm after grinding and exposure in a -45°C dew point drying chamber for 30 min (ionic conductivity retention was only 68.37%), while the electronic conductivity increased to 137.95 S / cm, and the limiting current density was only 1.92 mA / cm. 2The fundamental reason is that monothiols can only form weakly bound monodentate coordination, the unmodified electrolyte surface active sites react directly with water vapor, and the use of ligands not selected in this invention cannot form a dense and continuous monomolecular coating layer. Ultimately, this leads to electrolyte hydrolysis (sulfides react with water during exposure), the generation of electronically conductive byproducts, crystal structure collapse, and ion transport obstruction. This fully verifies that the bidentate dithiol ligands of this invention form a dense monomolecular coating layer through bidentate coordination, which can significantly improve the air stability of sulfide solid electrolytes, suppress electronic conductivity, and enhance lithium dendrite suppression capabilities without sacrificing intrinsic ionic conductivity.

[0097] Test Example 5 Electrochemical performance testing: The sulfide solid electrolyte membranes prepared in Examples 1-10 and Comparative Examples 1-5 of the present invention were placed in a -45°C dew point drying room and exposed for 30 minutes to obtain the exposed sulfide solid electrolyte membranes.

[0098] Preparation of all-solid-state composite cathode sheet: NCM811, Li6PS5Cl, superP and PTFE were mixed in a mass ratio of 70:20:5:5 and dispersed at 20,000 rpm for 2 minutes using a high-speed shear mill. The mixed composite cathode powder was then repeatedly rolled and sheared using a horizontal heated roller mill to obtain an areal loading of 15 mg / cm². 2 The positive electrode plate.

[0099] Preparation of all-solid-state composite negative electrode sheet: Graphite, Li6PS5Cl, superP, and PTFE were mixed in a mass ratio of 60:34:1:5 and dispersed at 20,000 rpm for 2 minutes using a high-speed shear mill. The mixed composite negative electrode powder was then repeatedly rolled and sheared using a horizontal heated roller mill to obtain an areal loading of 15 mg / cm². 2 The negative electrode.

[0100] The positive electrode, negative electrode, and the exposed sulfide solid electrolyte membranes of each embodiment and comparative example were cut into 10mm diameter discs. The negative electrode, electrolyte membrane, and positive electrode were placed in sequence. The pressure was maintained at 360MPa for 2 minutes. The battery was then removed, and the battery clamp was tightened with a torque wrench to apply a torque of 0.35N·M, so that the battery test pressure was 2MPa. During the test, the charge and discharge test range was controlled between 2.5V and 4.3V. The battery was then left to rest for 3 hours, activated by charge and discharge at 0.1C rate for 3 cycles, and cycled at 0.5C rate. The cycle capacity of the 100th cycle was recorded.

[0101] The formula for calculating capacity retention rate is: Capacity retention rate = Capacity in the 100th cycle ÷ Capacity in the 1st cycle.

[0102] Test Example 6: The sulfide solid electrolyte membranes prepared in Examples 1-10 and Comparative Examples 1-5 of the present invention were subjected to ionic conductivity tests after being exposed to static conditions in a dew point drying room at -45°C for 30 minutes. The test method was the same as that in Example 2.

[0103] Test Example 7: The sulfide solid electrolyte membranes prepared in Examples 1-10 and Comparative Examples 1-5 of the present invention were subjected to electronic conductivity tests after being exposed to static conditions in a dew point drying room at -45°C for 30 minutes. The test method was the same as that in Example 3.

[0104] Test Example 8: The sulfide solid electrolyte membranes prepared in Examples 1-10 and Comparative Examples 1-5 of the present invention were subjected to limiting current density tests after being exposed to static conditions in a dew point drying room at -45°C for 30 minutes. The test method was the same as that in Example 4.

[0105] The test results of test examples 5-8 above are shown in Table 2.

[0106] Table 2

[0107] In this invention, the sulfide solid electrolyte membranes prepared in the above embodiments and comparative examples were first exposed to static conditions in a -45°C dew point drying room for 30 minutes to simulate industrial production processing conditions before testing. The results show that the overall performance of the sulfide solid electrolyte membranes prepared in all the above embodiments of this invention reaches an excellent level suitable for industrial use, with a 0.1C discharge capacity of 200.67 mAh / g to 204.83 mAh / g, an initial coulombic efficiency of 89% to 91%, and a 100% discharge capacity of 100%. The cycle capacity retention rate was 89.70%–92.00%. After static exposure for 30 minutes in a -45°C dew point drying room, the room temperature ionic conductivity was 1.65 mS / cm–1.92 mS / cm, and the electronic conductivity remained at an extremely low level of 5.9 nS / cm–8.1 nS / cm. Among them, Example 9, which used a polyhexamethylene diamine-carbon disulfide type polythiourea single binder, achieved the best performance in all indicators. Meanwhile, Examples 1 and 3-4 also showed better performance. However, the performance of the sulfide solid electrolyte membranes prepared in Comparative Examples 1-5 deteriorated across the board. Comparative Example 2 showed a 22.47 percentage point lower capacity retention rate and a 76.6% lower ionic conductivity after exposure compared to Optimal Example 9. This is essentially because it failed to form a dense monomolecular coating layer of bidentate dithiol and a synergistic system of SS sulfur bridges between the ligand and the sulfur-based binder. This fully verifies that the technical solution of bidentate dithiol surface modification combined with sulfur-based binder can simultaneously solve the core pain points of sulfide solid electrolytes, such as poor air stability, high interfacial impedance, and difficulty in balancing ionic conductivity and mechanical properties. Furthermore, it can significantly reduce the requirements for the production environment and has significant industrialization value.

[0108] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a modified sulfide solid electrolyte, characterized in that, The preparation method includes: Under an inert atmosphere, a solution containing bidentate dithiol ligands is contacted with a sulfide solid electrolyte to react and obtain the modified sulfide solid electrolyte. The bidentate dithiol ligands are selected from at least one of 1,3-dithiol derivatives, aromatic dithiols, aliphatic bidentate dithiols, cyclic bidentate dithiols, and substituted bidentate dithiols.

2. The preparation method according to claim 1, characterized in that, The concentration of the solution containing bidentate dithiol ligands is 0.1 g / L to 100 g / L; And / or, the sulfide solid electrolyte is selected from at least one of the following: sulfide solid electrolyte of sulfide type, lithium thioide superionic conductor type, glassy sulfide solid electrolyte, and crystalline sulfide solid electrolyte; And / or, the mass ratio of the solution containing bidentate dithiol ligands to the sulfide solid electrolyte is 10:(1-5). And / or, the 1,3-dithiol derivative is selected from at least one of 1,3-dithiol-2-thionone-4,5-dithiol, 1,3-dithiol-2-one-4,5-dithiol, and 1,3-dithiol-2-imine-4,5-dithiol. And / or, the aromatic dithiol is selected from at least one of benzene-1,2-dithiol, toluene-3,4-dithiol, and 3,6-dichlorobenzene-1,2-dithiol; And / or, the aliphatic bidentate dithiol is selected from at least one of 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, and 2,3-butanedithiol; And / or, the cyclic bidentate dithiol is selected from 1,2-benzodithiol and / or dithiothreitol; And / or, the substituted bidentate dithiol is selected from 2,2-dimethyl-1,3-propanedithiol and / or 4-methyl-1,2-benzenedithiol.

3. The preparation method according to claim 2, characterized in that, The chemical formula of the silver-germanium sulfide solid electrolyte is Li 7-(a+b) PS 6-(a+b) X a Y b Where X and Y are the same or different, each independently being Cl or Br, and 0 ≤ a + b ≤ 1.7; and / or the chemical formula of the lithium thioate superionic conductor sulfide solid electrolyte is Li 10 SnP2S 12 Or Li 10 GeP2S 12 ; and / or, the glassy sulfide solid electrolyte has the chemical formula Li3PS4 or Li 3.2 PS4I 0.2 ; and / or, the chemical formula of the crystalline sulfide solid electrolyte is Li7P3S 11 .

4. The preparation method according to claim 1, characterized in that, The inert atmosphere is selected from at least one of argon, nitrogen, and helium; And / or, the reaction conditions include: a temperature of 30℃ to 80℃, a time of 0.5h to 2h, and a stirring rate of 100r / min to 3000r / min; And / or, the preparation method further includes: performing post-processing after the reaction; the post-processing includes: performing solid-liquid separation on the product obtained from the reaction to obtain a solid product, and washing the solid product.

5. A modified sulfide solid electrolyte prepared by any one of claims 1-4.

6. A sulfide solid electrolyte membrane, characterized in that, Including sulfur-based binders and modified sulfide solid electrolytes; Wherein, the modified sulfide solid electrolyte is the modified sulfide solid electrolyte as described in claim 5; Based on the mass of the sulfide solid electrolyte membrane as 100%, the mass content of the sulfur-based binder is 2% to 10%; and the mass content of the modified sulfide solid electrolyte is 90% to 98%.

7. A method for preparing a sulfide solid electrolyte membrane according to claim 6, characterized in that, The preparation method includes: A modified sulfide solid electrolyte, a sulfur-based binder, and a solvent are mixed to obtain an electrolyte slurry. The electrolyte slurry is coated on the substrate to obtain a preliminary film-forming product. The preliminary film-forming product is then hot-pressed to obtain the sulfide solid electrolyte membrane.

8. The preparation method according to claim 7, characterized in that, The solvent is selected from at least one of diethylene glycol dimethyl ether, tetrahydrofuran, ethyl tert-butyl ether, dipropylene glycol dimethyl ether, ethyl butyrate, isobutyl isovalerate, isobutyl isobutyrate, methyl hexanoate, anhydrous methyl isobutyl ketone, acetone, 3-pentanone, 4-heptanone, ethylcyclohexane, p-xylene, and decahydronaphthalene. And / or, the sulfur-containing adhesive is selected from at least one of polyethylene glycol disulfide, polyhexamethylene diamine-carbon disulfide type polythiourea, and polysulfide polyurethane; And / or, the solid content of the electrolyte slurry is 10% to 50%.

9. The preparation method according to claim 7 or 8, characterized in that, The mixing conditions include: a temperature of 25℃ to 40℃, a time of 30 min to 90 min, and a stirring rate of 100 r / min to 1800 r / min; And / or, the substrate is selected from at least one of PTFE film, polyimide film, aluminum foil, and stainless steel foil; And / or, the conditions for hot pressing include: a temperature of 80℃ to 150℃, a time of 1h to 2h, and a pressure of 1MPa to 20MPa; And / or, the thickness of the sulfide solid electrolyte membrane is 10 μm to 100 μm.

10. An all-solid-state battery, characterized in that, This includes the sulfide solid electrolyte membrane as described in claim 6 or the sulfide solid electrolyte membrane prepared by the preparation method described in any one of claims 7-9.

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