A sulfide electrolyte material based on thioamide compounds, a preparation method and a full solid-state battery

Abstract

The application discloses a sulfide electrolyte material prepared based on a thioamide compound, a preparation method and a full solid-state battery, and comprises the following steps: step 1: under an inert atmosphere, a sulfur-containing organic compound is ball-milled and mixed with a lithium source to obtain a mixed precursor; the application utilizes the characteristics that a thermal decomposition byproduct of the sulfur-containing organic compound is a gas, realizes self-purification of a reaction process, and omits complicated purification steps such as washing, filtering and drying in a traditional liquid-phase method, so that the technological process is greatly simplified. Meanwhile, by using the sulfur-containing organic compound and the lithium source as raw materials and through accurately controlled solid-phase reaction conditions, large-scale preparation of high-purity electrolyte is realized, the selected raw materials are cheap and easy to obtain, and the reaction conversion rate is high, so that the preparation cost is obviously reduced while the high purity of the product is ensured.

Description

Technical Field

[0001] This invention belongs to the field of solid-state batteries and relates to a sulfide electrolyte material based on thioamide compounds, a preparation method thereof, and an all-solid-state battery. Background Technology

[0002] All-solid-state lithium batteries achieve a significant increase in energy density by replacing flammable liquid electrolytes with solid electrolytes. Among various solid electrolytes, sulfide systems are widely regarded as one of the most promising technological approaches due to their unique ion transport characteristics.

[0003] The synthesis of sulfide solid electrolytes currently faces multiple technical obstacles. Traditional preparation methods generally suffer from incomplete reactions, insufficient product purity, and complex processes. In particular, byproduct residues caused by the liquid-phase synthesis environment can trigger Gibbs free energy mixing effects, causing the chemical reaction to reach equilibrium before complete conversion. This fundamental defect makes it difficult for existing methods to control costs while ensuring product purity. Furthermore, the extremely high price of the key raw material, high-purity lithium sulfide (Li₂S), has become a major bottleneck restricting the commercial application of sulfide solid electrolytes. Summary of the Invention

[0004] In order to overcome at least one deficiency of the prior art, the present invention provides a sulfide electrolyte material based on thioamide compounds, a preparation method thereof, and an all-solid-state battery.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing sulfide electrolyte materials based on thioamide compounds, comprising the following steps: Step 1: Under an inert atmosphere, the sulfur-containing organic compound and the lithium source are ball-milled and mixed to obtain a mixed precursor; Step 2: Under an inert atmosphere, the mixed precursors are sintered at high temperature. The released active sulfur source reacts with the lithium source, and the generated gaseous byproducts are removed from the reaction system to obtain secondary precursor materials. Step 3: Under an inert atmosphere, the secondary precursor material, thiophosphate precursor, and halogen-containing lithium source compound are ball-milled to obtain a ball-milled mixture. Step 4: Under an inert atmosphere, the ball-milled mixture is sintered a second time to obtain a sulfide solid electrolyte material with an argyrodite-type crystal structure.

[0006] Furthermore, the sulfur-containing organic compound is an organic sulfide that undergoes controlled thermal decomposition in a moderate temperature range to release an active sulfur source, and whose byproducts are gaseous substances.

[0007] Furthermore, the byproduct is at least one gaseous substance selected from CO2, NH3, low-molecular-weight amines, or hydrocarbons.

[0008] Furthermore, the sulfur-containing organic compound is selected from at least one of thioamides and thiocarbamates as the sulfur source.

[0009] Furthermore, the thermal decomposition byproducts of the lithium source are gases.

[0010] Furthermore, in step 2, the high-temperature sintering adopts a three-stage temperature control: the first stage is to raise the temperature from room temperature to 300°C, so that the residual solvent and low-boiling-point by-products can slowly evaporate; the second stage is to raise the temperature to 500-600°C, so that the sulfur-containing organic compounds can be fully decomposed; and the third stage is to raise the temperature to 750-850°C and hold it at that temperature.

[0011] Furthermore, the molar ratio of the sulfur-containing organic compound to the lithium source is (1.0-1.5):2, and the molar ratio of the secondary precursor, the thiophosphate precursor, and the halogen-containing lithium source compound is (5.0-6.0):(0.8-1.2):(1.0-2.0).

[0012] Furthermore, in step 3, the thiophosphate is at least one of P2S5, P4S7, and Li3PS4, and the halogenated lithium source compound is at least one of LiCl, lithium bromide, and lithium iodide.

[0013] A sulfide electrolyte material, prepared by the aforementioned preparation method, wherein the sulfide electrolyte material has an argyrodite-type crystal structure and the general chemical formula Li. 5+x PS 4-x Cl 1+x Where 0 ≤ x ≤ 1; room temperature ionic conductivity not less than 0.3 mS / cm -1 .

[0014] An all-solid-state battery is prepared from the sulfide solid electrolyte material and includes a positive electrode composite material, an electrolyte layer and a negative electrode material stacked together. The positive electrode composite material is prepared from the sulfide solid electrolyte material and the positive electrode active material, and the electrolyte layer is prepared by cold pressing the sulfide solid electrolyte material.

[0015] In summary, the advantages of this invention are: This invention utilizes the gaseous nature of the thermal decomposition byproducts of sulfur-containing organic compounds to achieve self-purification of the reaction process, eliminating the cumbersome purification steps of traditional liquid-phase methods such as washing, filtration, and drying, thus greatly simplifying the process. Simultaneously, using sulfur-containing organic compounds and lithium sources as raw materials, and through precisely controlled solid-phase reaction conditions, it achieves the large-scale preparation of high-purity electrolytes. The selected raw materials are inexpensive and readily available, and the reaction conversion rate is high, ensuring high product purity while significantly reducing preparation costs. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a method for preparing lithium sulfide according to an embodiment of the present invention.

[0017] Figure 2 The image shows the XRD pattern of the secondary precursor obtained in Experimental Example 1 of this invention.

[0018] Figure 3 Li prepared in Experimental Example 1 of this invention 5.5 PS 4.5 Cl 1.5 XRD pattern.

[0019] Figure 4 Li prepared in Experimental Example 1 of this invention 5.5 PS 4.5 Cl 1.5 EIS diagram.

[0020] Figure 5 Li prepared in Experimental Example 1 of this invention 5.5 PS 4.5 Cl 1.5 The rate performance diagram.

[0021] Figure 6 Li prepared in Experimental Example 1 of this invention 5.5 PS 4.5 Cl 1.5 The cyclic performance diagram.

[0022] Figure 7 The image shows the XRD pattern of the secondary precursor obtained in Experimental Example 2 of this invention.

[0023] Figure 8 Li prepared in Experimental Example 2 of this invention 5.5 PS 4.5 Cl 1.5 XRD pattern.

[0024] Figure 9 Li prepared in Experimental Example 2 of this invention 5.5 PS 4.5 Cl 1.5 EIS diagram.

[0025] Figure 10 Li prepared in Experimental Example 2 of this invention 5.5 PS 4.5 Cl 1.5 The rate performance diagram.

[0026] Figure 11 Li prepared in Experimental Example 2 of this invention 5.5 PS 4.5 Cl 1.5 The cyclic performance diagram.

[0027] Figure 12 The image shows the XRD pattern of the secondary precursor obtained in Experimental Example 3 of this invention.

[0028] Figure 13 The Li prepared in Experimental Example 3 of this invention 5.5 PS 4.5 Cl 1.5 XRD pattern.

[0029] Figure 14 The Li prepared in Experimental Example 3 of this invention 5.5 PS 4.5 Cl 1.5 EIS diagram.

[0030] Figure 15 The Li prepared in Experimental Example 3 of this invention 5.5 PS 4.5 Cl 1.5 The rate performance diagram.

[0031] Figure 16 The diagram shows the cycling performance of Li5.5PS4.5Cl1.5 prepared in Experimental Example 3 of this invention. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0033] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with conventional techniques or conditions described in the literature in this field and the techniques or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. The source, trade name, and, where necessary, composition of the reagents used shall be indicated upon their first appearance; thereafter, unless otherwise specified, the same information shall apply to the same reagents used.

[0034] Example: like Figure 1 As shown, a method for preparing a sulfide electrolyte material based on thioamide compounds includes the following steps: Step 1: Under an inert atmosphere, the sulfur-containing organic compound and the lithium source are ball-milled and mixed to obtain a mixed precursor; Step 2: Under an inert atmosphere, the mixed precursors are sintered at high temperature. The released active sulfur source reacts with the lithium source, and the generated gaseous byproducts are removed from the reaction system to obtain high-purity secondary precursor materials. Step 3: Under an inert atmosphere, the secondary precursor, thiophosphate precursor, and halogen-containing lithium source compound are ball-milled to obtain a ball-milled mixture. Step 4: Under an inert atmosphere, the ball-milled mixture is sintered a second time to obtain a sulfide solid electrolyte material with an argyrodite-type crystal structure.

[0035] In step 1, the sulfur-containing organic compound undergoes controlled thermal decomposition in a moderate temperature range (typically 400°C to 800°C) to release an active sulfur source (active S). 2- The method involves the synthesis of organic sulfides containing at least one gaseous substance, such as CO2, NH3, low-molecular-weight amines, or hydrocarbons, as byproducts. Under solid-phase reaction conditions, the gaseous byproducts can spontaneously and completely detach from the solid-phase reaction system, avoiding the mixed Gibbs free energy (ΔG_mix) effect seen in liquid-phase reactions. This fundamentally drives the solid-phase reaction equilibrium to continuously shift towards the products, ensuring that the reactants can be almost completely converted into the target intermediate. This achieves high-purity synthesis of secondary precursor materials, thus fundamentally solving the technical bottlenecks of incomplete reaction, low product purity, and the need for complex subsequent purification steps caused by byproduct residues in traditional liquid-phase metathesis methods.

[0036] The sulfur-containing organic compound uses at least one of thioamides or thiocarbamates as the sulfur source, which enables this efficient and clean reaction pathway.

[0037] Thioamides include thiourea (CH4N2S), thioacetamide (CH3CSNH2), thiopropionamide (CH3CH2CSNH2), thioisobutyramide (C4H9NS), N-methylthioacetamide (CH3CSNHCH3), and thiooxazone (H2NCCSCNH2); thiocarbamates include copper dibutyldithiocarbamate (C... 18 H 36 CuN2S4), sodium diethyldithiocarbamate ((CH3CH2)2NCS2Na), ammonium piperidine dithiocarbamate (C5H) 10 NCS2NH4), sodium ethylene didithiocarbamate (C4H6N2S4Na2).

[0038] The thermal decomposition byproducts of lithium sources are gases.

[0039] The lithium sources used are lithium hydroxide (LiOH), lithium carbonate (Li2CO3), lithium acetate (LiCH3COO), lithium nitrate (LiNO3), lithium oxalate (Li2C2O4), lithium citrate (Li3C6H5O7), and lithium formate (LiHCOO). The decomposition temperature of the above lithium sources is moderate, ranging from 600 to 900℃, and the byproducts are gases that are easily volatilized.

[0040] The molar ratio of sulfur-containing organic compounds to lithium sources is (1.0-1.5):2. This ratio range ensures sufficient decomposition of the sulfur source and provides adequate sulfur. 2- Used in reactions.

[0041] The ball mill speed is 300-500 rpm, and the milling time is 6-10 hours. The grinding media includes one or more types of stainless steel balls, tungsten carbide balls, ceramic balls, alumina balls, and zirconia balls with diameters of 30-10 mm, 9-5 mm, and >5 mm. The ratio of large balls to medium balls is between 1:1 and 1:3, with the remainder being small balls. The ratio of the total mass of the grinding media to the mass of the raw material is (50-60):1 or (15-25):1. This grinding media ratio can effectively improve the ball milling efficiency and ensure thorough mixing of the raw materials.

[0042] The inert atmosphere is argon or nitrogen, with a purity of not less than 99.99%, and the oxygen content and moisture concentration are controlled below 1 ppm. The gas flow rate of the inert atmosphere is 0.5-2 SCCM. This flow rate range can effectively maintain the inert environment of the reaction system, while avoiding excessive gas flow that could lead to raw material loss.

[0043] In step 2, the mixed precursor is placed in a sintering furnace and sintered under a protective atmosphere using a programmed temperature rise method. The sintering temperature range is 600-900°C, the heating rate is controlled at 1-5°C / min, and the holding time is 4-12 hours. Preferably, the sintering temperature is 750-850°C.

[0044] The sintering furnace is a tube furnace or a box furnace, and the atmosphere inside the furnace is high-purity argon or nitrogen, with an oxygen concentration of ≤5 ppm and a moisture concentration of ≤1 ppm.

[0045] The programmed temperature sintering employs a three-stage temperature control: the first stage raises the temperature from room temperature to 300°C at a rate of 2-3°C / min, allowing residual solvents and low-boiling-point byproducts to slowly evaporate; the second stage raises the temperature to 500-600°C at a rate of 3-5°C / min, achieving complete decomposition of sulfur-containing organic compounds; the third stage raises the temperature to 750-850°C at a rate of 1-2°C / min, holding for 6-10 hours. At this sintering temperature, sulfur-containing organic compounds undergo thermal decomposition to produce active sulfur sources and byproducts. The active sulfur sources react with lithium sources in a solid-phase metathesis reaction to generate highly crystalline secondary precursor materials; byproducts such as CO2 and NH3 are discharged from the system in gaseous form.

[0046] Experiments show that when the sintering temperature is below 700°C, the reaction is incomplete, leaving unreacted lithium source residues in the secondary precursor material. When the temperature is above 900°C, the secondary precursor material undergoes partial volatilization, leading to deviations in the stoichiometry. However, within the optimized temperature range of 750-850°C, a large amount of product is retained with a uniform grain size distribution, providing high-quality secondary precursor material for subsequent electrolyte synthesis.

[0047] The flow rate of the protective atmosphere gas is controlled within the range of 0.5-2 L / min to maintain a slightly positive pressure inside the furnace. The protective atmosphere is argon, with a flow rate of 1 L / min. This flow rate ensures timely removal of gaseous byproducts while preventing excessive gas flow from causing the mixed precursor powder to scatter.

[0048] Scanning electron microscopy (SEM) experiments were performed on the secondary precursor material. The SEM images showed that the secondary precursor material was in the form of irregular particles, with a particle size mainly distributed in the range of 1-5 μm, exhibiting good sintering activity. The specific surface area of ​​the secondary precursor material ranged from 2-5 m². 2 / g, this range ensures sufficient reactivity while avoiding agglomeration caused by excessively high surface energy.

[0049] In step 3, the molar ratio of the secondary precursor, the thiophosphate precursor, and the halogen-containing lithium source compound is (5.0-6.0):(0.8-1.2):(1.0-2.0).

[0050] The thiophosphate is at least one of P2S5, P4S7, and Li3PS4.

[0051] The halogenated lithium source compound is at least one of LiCl, lithium bromide, and lithium iodide.

[0052] The ball milling speed is 350-450 rpm, and the ball milling time is 6-10 hours.

[0053] Preferably, P2S5 is used as the thiophosphate, and LiCl is used as the halogenated lithium source compound. The molar ratio of the secondary precursor, P2S5, and LiCl is 5.5 : 1.0 : 1.5. This molar ratio can obtain the stoichiometric target product Li. 5.5 PS 4.5 Cl 1.5 The chemical stoichiometric ratio.

[0054] The grinding media for the ball mill include one or more types of stainless steel balls, tungsten carbide balls, ceramic balls, alumina balls, and zirconia balls with diameters of 9-5 mm and >5 mm. The ratio of large balls to medium balls is between 1:5 and 1:15, and the ratio of the total mass of the grinding media to the mass of the raw material is between (5-60):1; the ratio of the total mass of the grinding media to the total mass of the raw material is between (15-25):1. This grinding media ratio can effectively improve the ball milling efficiency and ensure thorough mixing of secondary precursors, thiophosphate precursors, and halogenated lithium source compounds.

[0055] In step 4, the secondary precursor powder reacts with thiophosphate and a halogen-containing lithium source compound to form Li. 5.5 PS 4.5 Cl 1.5 Sulfides.

[0056] The secondary sintering temperature is 450-550°C, the heating rate is 1-3°C / min, and the holding time is 10-14 hours; preferably, the secondary sintering temperature is 500°C, the holding time is 12 hours, and the heating rate is 2°C / min. Under these optimized conditions, the secondary precursor powder can fully generate the final product with a regular argyrodite crystal structure through a solid-state reaction with thiophosphate and halogen-containing lithium source compound.

[0057] The inert atmosphere is argon or nitrogen, with a purity of not less than 99.99%, and the oxygen content and moisture concentration are both controlled below 1 ppm. The gas flow rate of the inert atmosphere is 0.5-2 SCCM. This flow rate range can effectively maintain the inert environment of the reaction system while avoiding raw material loss due to excessive gas flow.

[0058] A sulfide electrolyte material is prepared using a method for preparing sulfide electrolyte materials based on thioamide compounds. The sulfide electrolyte material has an argyrodite-type crystal structure and the general chemical formula Li. 5+x PS 4-x Cl 1+x Where 0 ≤ x ≤ 1; preferably, x = 0.5. The room temperature ionic conductivity of the material is not less than 0.3 mS / cm. -1 .

[0059] A method for preparing an all-solid-state battery includes the following steps: S1: The sulfide solid electrolyte material and the positive electrode active material are mixed at a mass ratio of (2:8) to (4:6) to obtain a uniform positive electrode composite material; The positive electrode active material is at least one of layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811), lithium cobalt oxide (LiCoO2), or lithium-rich manganese-based material, and the mass ratio of the positive electrode active material to the sulfide solid electrolyte material is 3:7. The two are mixed in an agate mortar or by ball milling for 20-60 minutes to obtain a uniform mixed positive electrode powder.

[0060] S2: The sulfide solid electrolyte material powder is cold-pressed for the first time and formed into a dense electrolyte layer under a pressure of 1-4 tons; Preferably, the pressure of the first cold press is 2 tons, and the pressure holding time is 30-90 seconds.

[0061] S3: Add positive electrode composite material to the electrolyte layer and perform a second cold pressing to form a tight interface between the positive electrode layer and the electrolyte layer under a pressure of 2-5 tons. Preferably, the pressure of the second cold press is 3 tons, and the pressure holding time is 30-90 seconds.

[0062] S4: Assemble the negative electrode material on the counter electrode side and seal the battery under an inert atmosphere, with the sealing torque controlled at 10-30 N·m, preferably 20 N·m.

[0063] The negative electrode materials are indium and lithium sheets, with the indium sheet having a thickness of 0.05-0.15 mm and the lithium sheet having a thickness of 0.05-0.15 mm. Preferably, the indium sheet has a thickness of 0.1 mm and the lithium sheet has a thickness of 0.1 mm, and they are brought into contact with the counter electrode by cold pressing.

[0064] Preferably, the sealing torque is 20 N·m. This torque range ensures sufficient contact pressure between the components inside the battery, while preventing the electrolyte sheet from breaking due to excessive pressure.

[0065] The entire process of preparing all-solid-state batteries is carried out under inert gas protection. The inert atmosphere is argon or nitrogen, with a purity of not less than 99.99%, and the oxygen content and moisture concentration are controlled below 1 ppm. The gas flow rate of the inert atmosphere is 0.5-2 SCCM. This flow rate range can effectively maintain the inert environment of the reaction system while avoiding raw material loss due to excessive gas flow.

[0066] An all-solid-state battery includes a positive electrode composite material, an electrolyte layer, and a negative electrode material stacked together. The all-solid-state battery retains no less than 75% of its capacity after 270 cycles at 1C rate.

[0067] This application uses thiourea (CH4N2S), thioacetamide (CH3CSNH2), and thioisobutyramide (C4H9NS) as sulfur-containing organic compounds to prepare sulfide solid electrolyte materials sequentially according to the preparation method of sulfide solid electrolyte materials in the examples. X-ray diffraction and electrochemical performance tests were performed on the sulfide solid electrolyte materials to verify the improvement effect of the electrochemical performance of the sulfide solid electrolyte materials. The specific process is shown in Experiment Examples 1-3.

[0068] Experimental Example 1 Li 5.5 PS 4.5 Cl 1.5 Solid-phase preparation of electrolytes Initial ball milling: Thiourea (CH4N2S) and lithium hydroxide (LiOH) were placed in a 250 mL ball milling jar at a molar ratio of 1.2:2 and mixed with zirconia balls (D10 balls, D8 balls, and D5 balls with a diameter of 10 mm were added in a certain proportion). The mixture was ball milled at 400 rpm for 8 h to obtain a mixed precursor.

[0069] Primary sintering: The obtained precursor powder is placed in a tube furnace under an argon atmosphere, heated to 800℃ and held for 8 h to obtain secondary precursor powder.

[0070] Secondary ball milling: Take the secondary precursor, phosphorus pentasulfide (P2S5) and lithium chloride (LiCl) and place them in a 100mL vacuum ball mill jar at a molar ratio of 5.5:1.0:1.5 and mix them with zirconia balls (D10 balls, D5 balls and D2 balls with a diameter of 10 mm are added in a certain proportion). Ball mill at 400 rpm for 8 h to obtain the mixed precursor.

[0071] Secondary sintering: The obtained sulfide solid electrolyte precursor powder was placed in a tube furnace under an argon atmosphere, heated to 500℃ and held for 12 hours to obtain the sulfide solid electrolyte Li. 5.5 PS 4.5 Cl 1.5 powder.

[0072] X-ray diffraction test results are as follows: Figures 2-3 As shown, the electrochemical performance test results are as follows: Figures 2-6 As shown, Structural characterization: X-ray diffraction (XRD) was used to characterize the secondary precursor materials Li₂S and Li₂S. 5.5 PS 4.5 Cl 1.5 Phase identification was performed, and the images showed that the main diffraction peaks of the product were consistent with the standard phase, and no obvious secondary phases were observed, indicating that the sample had good crystallization and high purity.

[0073] Ionic conductivity test: The synthesized Li5.5 PS 4.5 Cl 1.5 The powder was cold-pressed into electrolyte discs with a diameter of 10 mm and a thickness of approximately 1 mm (without binder). Electrochemical impedance spectroscopy (EIS) was performed at room temperature, and Nyquist curve fitting results showed that the room-temperature ionic conductivity of this material was 3.041 mS / cm. -1 .

[0074] Rate performance testing: using sulfide solid electrolyte Li 5.5 PS 4.5 Cl 1.5 Commercial NCM811 powder (positive electrode) and lithium indium (negative electrode) were assembled into a full cell, and constant current charge-discharge tests were conducted using the Newway Battery Testing System to analyze the rate performance. The results showed that the discharge capacities at 0.2 C rate were 167.88, 167.62, 166.91, 166.67, and 166.38 mAhg, respectively. -1 Although the discharge capacity varied slightly in the first week due to the use of the same positive and negative electrodes, it remained at 167 mAh g⁻¹ overall. -1 The results of 5-week charge-discharge tests at 0.33 C and 0.5 C rates were good, remaining essentially unchanged. However, some capacity degradation was observed in tests at 1 C and 2 C rates; despite this, the capacity retention rate at 2 C rate was still 80.27%.

[0075] Cyclic performance testing: First, activation was performed for 5 weeks at a low rate of 0.2 C, followed by a long-cycle test at a rate of 1 C. The results are as follows... Figure 6 As shown, the discharge capacity of the sample remained essentially unchanged after 270 charge-discharge cycles, indicating that the material has good cycle performance.

[0076] Experiment Example 2 Li 5.5 PS 4.5 Cl 1.5 Solid-phase preparation of electrolytes Initial ball milling: Thioacetamide (CH3CSNH2) and lithium hydroxide (LiOH) were mixed with zirconia balls (D10, D8, and D5 balls with a diameter of 10 mm were added in a certain proportion) in a 250 mL ball milling jar at a molar ratio of 1.2:2, and ball milled at 400 rpm for 8 h to obtain a mixed precursor.

[0077] Primary sintering: The obtained precursor powder is placed in a tube furnace under an argon atmosphere, heated to 950℃ and held for 8 hours to obtain secondary precursor powder.

[0078] Secondary ball milling: Take the secondary precursor, phosphorus pentasulfide (P2S5) and lithium chloride (LiCl) and place them in a 100mL vacuum ball mill jar at a molar ratio of 5.5:1.0:1.5 and mix them with zirconia balls (D10 balls, D5 balls and D2 balls with a diameter of 10 mm are added in a certain proportion). Ball mill at 400 rpm for 8 h to obtain the mixed precursor.

[0079] Secondary sintering: The obtained sulfide solid electrolyte precursor powder was placed in a tube furnace under an argon atmosphere, heated to 500℃ and held for 12 hours to obtain the sulfide solid electrolyte Li. 5.5 PS 4.5 Cl 1.5 powder.

[0080] X-ray diffraction test results are as follows: Figures 7-8 As shown, the electrochemical performance test results are as follows: Figures 9-11 As shown, Structural characterization: X-ray diffraction (XRD) was used to characterize the secondary precursor materials Li₂S and Li₂S. 5.5 PS 4.5 Cl 1.5 Phase identification was performed, and the images showed that the main diffraction peaks of the product were consistent with the standard phase, and no obvious secondary phases were observed, indicating that the sample had good crystallization and high purity.

[0081] Ionic conductivity test: The synthesized Li 5.5 PS 4.5 Cl 1.5 The powder was cold-pressed into electrolyte discs with a diameter of 10 mm and a thickness of approximately 1 mm (without binder). Electrochemical impedance spectroscopy (EIS) was performed at room temperature, and Nyquist curve fitting results showed that the room-temperature ionic conductivity of this material was 2.242 mS / cm. -1 .

[0082] Rate performance testing: using sulfide solid electrolyte Li 5.5 PS 4.5 Cl 1.5 Commercial NCM811 powder (positive electrode) and lithium indium (negative electrode) were assembled into a full cell, and constant current charge-discharge tests were conducted using the Newway Battery Testing System to analyze rate performance. The results showed that its first-cycle discharge capacity at 0.2 C rate was 119.55 mAh g⁻¹. -1 The discharge capacity decreases with increasing number of cycles, but it remains relatively good at discharge rates of 0.33 C, 0.5 C, 1 C and 2 C.

[0083] Cyclic performance testing: First, activation was performed for 5 weeks at a low rate of 0.2 C, followed by a long-cycle test at a rate of 1 C. The results are as follows... Figure 11 As shown, the discharge capacity decreases with increasing cycle number, and the discharge capacity retention rate of the sample is 75.0% after 270 charge-discharge cycles.

[0084] Experimental Example 3 Li 5.5 PS 4.5 Cl 1.5 Solid-phase preparation of electrolytes Initial ball milling: Thioisobutyramide (C4H9NS) and lithium hydroxide (LiOH) were mixed with zirconia balls (D10, D8, and D5 balls with a diameter of 10 mm were added in a certain proportion) in a 250 mL ball milling jar at a molar ratio of 1.2:2, and ball milled at 400 rpm for 8 h to obtain a mixed precursor.

[0085] Primary sintering: The obtained precursor powder is placed in a tube furnace under an argon atmosphere, heated to 900℃ and held for 8 h to obtain secondary precursor powder.

[0086] Secondary ball milling: Take the secondary precursor, phosphorus pentasulfide (P2S5) and lithium chloride (LiCl) and place them in a 100mL vacuum ball mill jar at a molar ratio of 5.5:1.0:1.5 and mix them with zirconia balls (D10 balls, D5 balls and D2 balls with a diameter of 10 mm are added in a certain proportion). Ball mill at 400 rpm for 8 h to obtain the mixed precursor.

[0087] Secondary sintering: The obtained sulfide solid electrolyte precursor powder was placed in a tube furnace under an argon atmosphere, heated to 500℃ and held for 12 h to obtain the sulfide solid electrolyte Li. 5.5 PS 4.5 Cl 1.5 powder.

[0088] X-ray diffraction test results are as follows: Figures 12-13 As shown, the electrochemical performance test results are as follows: Figures 14-16 As shown, Ionic conductivity test: The synthesized Li 5.5 PS 4.5 Cl 1.5 The powder was cold-pressed into electrolyte discs with a diameter of 10 mm and a thickness of approximately 1 mm (without binder). Electrochemical impedance spectroscopy (EIS) was performed at room temperature, and Nyquist curve fitting results showed that the room-temperature ionic conductivity of this material was 0.381 mS / cm. -1 .

[0089] Rate performance testing: using sulfide solid electrolyte Li 5.5 PS 4.5 Cl1.5 Commercial NCM811 powder (positive electrode) and lithium indium (negative electrode) were assembled into a full cell, and constant current charge-discharge tests were conducted using the Newway Battery Testing System to analyze rate performance and long-cycle stability. The results showed that its first-cycle discharge capacity at 0.2 C rate was 126.07 mAh g⁻¹. -1 The discharge capacity decreases with increasing number of cycles, but it remains relatively good at discharge rates of 0.33 C, 0.5 C, 1 C and 2 C.

[0090] Cyclic performance testing: First, activation was performed for 5 weeks at a low rate of 0.2 C, followed by a long-cycle test at a rate of 1 C. The results are as follows... Figure 16 As shown, the discharge capacity of the sample remained essentially unchanged after 250 charge-discharge cycles, indicating that the material has good cycle performance.

[0091] The solid-phase preparation process provided by this invention utilizes specific sulfur-containing organic compounds (such as thiourea and thioacetamide) to react with easily decomposable lithium sources. By leveraging the fact that the reaction byproducts are gaseous substances, the reaction is driven to completion, avoiding complex subsequent purification steps, thus significantly reducing production costs at the source. Table 2 shows the cost calculation data. When using the optimal thiourea (CH4N2S) as the sulfur source, the cost of synthesizing 100g of Li5.5PS4.5Cl1.5 solid electrolyte is approximately RMB 1037.9, a cost reduction of approximately 78.2% compared to the market purchase price (approximately RMB 4752 / 100g). Even using the lower-cost thioacetamide (CH3CSNH2), its synthesis cost (RMB 4072.4 / 100g) is still lower than the market price, possessing a cost advantage of approximately 14.3%. This fully demonstrates the enormous economic potential of the method of this invention in large-scale production.

[0092] The cost advantage stems from the low-cost synthesis of the key precursor, lithium sulfide (Li2S). Traditional high-purity Li2S is extremely expensive (approximately RMB 7333 / 100g, see Table 1), posing a significant bottleneck to the industrialization of sulfide electrolytes. This invention, however, uses thiourea and lithium hydroxide as raw materials to prepare high-purity secondary precursor Li2S through a one-step solid-state reaction, at a cost of only RMB 260.4 / 100g, approximately 96.4% lower than the market purchase price. This low cost of the core secondary precursor material is the fundamental reason for the significant reduction in the overall cost of the final electrolyte material. This method utilizes readily available raw materials, simplifies the process, and eliminates the need for expensive purification equipment, providing a highly commercially competitive technological path for the large-scale, low-cost preparation of argyrodite-type sulfide solid electrolytes.

[0093] Table 1

[0094] Table 2

[0095] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing sulfide electrolyte materials based on thioamide compounds, characterized in that: Includes the following steps Step 1: Under an inert atmosphere, the sulfur-containing organic compound and the lithium source are ball-milled and mixed to obtain a mixed precursor; Step 2: Under an inert atmosphere, the mixed precursors are sintered at high temperature. The released active sulfur source reacts with the lithium source, and the generated gaseous byproducts are removed from the reaction system to obtain secondary precursor materials. Step 3: Under an inert atmosphere, the secondary precursor material, thiophosphate precursor, and halogen-containing lithium source compound are ball-milled to obtain a ball-milled mixture. Step 4: Under an inert atmosphere, the ball-milled mixture is sintered a second time to obtain a sulfide solid electrolyte material with an argyrodite-type crystal structure.

2. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 1, characterized in that: The sulfur-containing organic compounds are organic sulfides that undergo controllable thermal decomposition in a medium temperature range to release active sulfur sources, with gaseous byproducts.

3. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 2, characterized in that: The byproduct is at least one gaseous substance selected from CO2, NH3, low-molecular-weight amines, or hydrocarbons.

4. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 1, characterized in that: The sulfur-containing organic compound is selected from at least one of thioamides and thiocarbamates as the sulfur source.

5. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 1, characterized in that: The thermal decomposition byproducts of the lithium source are gases.

6. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 1, characterized in that: In step 2, the high-temperature sintering adopts a three-stage temperature control: the first stage is to raise the temperature from room temperature to 300°C to allow the residual solvent and low-boiling-point byproducts to slowly evaporate; the second stage is to raise the temperature to 500-600°C to fully decompose the sulfur-containing organic compounds; and the third stage is to raise the temperature to 750-850°C and hold it at that temperature.

7. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 1, characterized in that: The molar ratio of the sulfur-containing organic compound to the lithium source is (1.0-1.5):2, and the molar ratio of the secondary precursor, the thiophosphate precursor, and the halogen-containing lithium source compound is (5.0-6.0):(0.8-1.2):(1.0-2.0).

8. The method for preparing sulfide electrolyte materials based on thioamide compounds according to claim 1, characterized in that: In step 3, the thiophosphate is at least one of P2S5, P4S7, and Li3PS4, and the halogenated lithium source compound is at least one of LiCl, lithium bromide, and lithium iodide.

9. A sulfide electrolyte material, characterized in that: The sulfide electrolyte material is prepared by the preparation method according to any one of claims 1-8, and the sulfide electrolyte material has an argyrodite-type crystal structure and a general chemical formula of Li. 5+ x PS 4-x Cl 1+x Where 0 ≤ x ≤ 1; room temperature ionic conductivity not less than 0.3 mS / cm -1 .

10. An all-solid-state battery, characterized in that: The preparation of the sulfide solid electrolyte material according to claim 9 includes a positive electrode composite material, an electrolyte layer and a negative electrode material stacked together, wherein the positive electrode composite material is prepared by the sulfide solid electrolyte material and the positive electrode active material, and the electrolyte layer is prepared by cold pressing the sulfide solid electrolyte material.

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