A surface modification preparation method of an air-stable lithium phosphorus sulfur bromide compound

Abstract

The application relates to a surface modification preparation method of an air-stable lithium phosphorus sulfur bromide compound and relates to the technical field of solid electrolytes. Lithium sulfide, diphosphorus pentasulfide, elemental sulfur, lithium bromide and a dispersing agent are mixed and ball milled to obtain a lithium phosphorus sulfur bromide compound precursor; a scandium oxide dopant is added to the precursor and high-temperature sintering is carried out to obtain a doped modified lithium phosphorus sulfur bromide compound; the doped modified lithium phosphorus sulfur bromide compound is placed in a reaction furnace, acetylene is used as a carbon source and phosphoric acid is used as a phosphorus source, a phosphorus modified carbon nanotube coating layer is formed on the surface of the compound, and an air-stable lithium phosphorus sulfur bromide compound is obtained after cooling; the dispersing agent is prepared from N-vinylpyrrolidone, tripropyleneglycol diacrylate, ethyl acetate and azobisisobutyronitrile; the application realizes the synergistic improvement of air stability and ionic conductivity, has good electrochemical performance and good compatibility with a lithium metal negative electrode.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and in particular to a method for preparing air-stabilized lithium phosphorus sulfide bromide compounds by surface modification. Background Technology

[0002] All-solid-state lithium batteries have become a research hotspot in the field of next-generation lithium batteries due to their advantages such as high energy density, good safety, and no risk of leakage. Solid-state electrolytes, as the core component of all-solid-state lithium batteries, directly determine the overall performance of the battery. Lithium-phosphorus-sulfur-bromine compounds, as an important branch of sulfide solid electrolytes, possess high lithium-ion conductivity, good mechanical ductility, and low grain boundary resistance. They can be densified through cold pressing processes, forming close contact with the electrodes and significantly reducing interfacial impedance. Furthermore, they do not contain flammable organic solvents, fundamentally eliminating the risk of thermal runaway in traditional lithium-ion batteries, and are considered one of the most commercially promising solid electrolyte systems.

[0003] Chinese Patent CN120149518A discloses a method for preparing a lithium-phosphorus-sulfur-bromine solid electrolyte, relating to the field of solid-state lithium battery technology. The solid electrolyte is prepared by raw material pretreatment, mechanochemical ball milling, high-temperature crystallization, and post-treatment processes; dynamic bromine atmosphere control is employed, combined with sulfur partial pressure adjustment and particle size gradient design.

[0004] Chinese Patent CN121292383A: Belonging to the field of solid-state battery technology, this invention provides a lithium-sulfur-phosphorus-chlorine-bromine solid electrolyte, its preparation method, and an all-solid-state battery. The preparation method includes the following steps: mixing lithium sulfide and phosphorus sulfide and then ball-milling to obtain a lithium-sulfur-phosphorus ternary mixture; in a protective gas atmosphere, mixing the lithium-sulfur-phosphorus ternary mixture, lithium chloride, and lithium bromide and then ball-milling to obtain a lithium-sulfur-phosphorus-chlorine-bromine mixture; and in a protective gas atmosphere, heat-treating the lithium-sulfur-phosphorus-chlorine-bromine mixture to obtain the lithium-sulfur-phosphorus-chlorine-bromine solid electrolyte.

[0005] Existing technologies mainly employ doping or surface coating. Doping can lead to crystal structure distortion and reduce lithium-ion conductivity. Surface coating, on the other hand, can cause the coating layer to fall off easily and increase interfacial impedance, affecting lithium-ion transport efficiency and making it difficult to achieve a balance between stability and conductivity. Summary of the Invention

[0006] To address the above problems, this invention provides a method for preparing air-stabilized lithium phosphorus sulfide bromine compounds through surface modification. The operation steps are as follows, in parts by mass: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 22-44 parts lithium sulfide, 29-57 parts phosphorus pentasulfide, 7-13 parts elemental sulfur, 15-27 parts lithium bromide, and 1-5 parts dispersant evenly, and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfur bromide compound precursor. S3: Add 0.2-2 parts of scandium oxide dopant to 60-100 parts of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0007] In some embodiments, the vacuum drying temperature in S1 is 100-120°C and the time is 12-16 hours.

[0008] In some embodiments, the particles in S1 are crushed and screened to a particle size of 30-50 μm.

[0009] In some embodiments, the ball-to-material ratio in S2 is 30-40:1, the ball milling speed is 300-400 r / min, and the ball milling time is 8-12 h.

[0010] In some embodiments, the sintering temperature in S3 is 500-600℃, and the sintering time is 3-6h.

[0011] In some embodiments, the acetylene flow rate in S4 is 20-30 mL / min, and the phosphoric acid flow rate is 10-15 mL / min.

[0012] In some embodiments, the reaction temperature in S4 is 700-800°C and the reaction time is 60-120 min.

[0013] In some embodiments, the coating layer thickness in S4 is 20-50 nm.

[0014] In some embodiments, the dispersant in S2 is prepared by: According to the mass fractions, 10-20 parts of N-vinylpyrrolidone, 8-16 parts of tripropylene glycol diacrylate, 100-200 parts of ethyl acetate, and 0.4-0.8 parts of azobisisobutyronitrile are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 20-40 minutes, the temperature is raised to react, and ethyl acetate is removed by vacuum distillation to obtain the dispersant.

[0015] In some embodiments, the heating reaction temperature during the preparation of the dispersant is 60-70°C, and the time is 4-8 hours.

[0016] Reaction mechanism This reaction uses azobisisobutyronitrile (AIBN) as a thermal initiator. Under nitrogen protection and at 60-70°C, a free radical solution copolymerization reaction occurs. Upon heating, AIBN homolytically cleaves to generate isobutyronitrile free radicals, which sequentially initiate the opening of the carbon-carbon double bonds of N-vinylpyrrolidone and tripropylene glycol diacrylate, resulting in free radical addition. Monomer molecules continuously and alternately insert into the growing chain to form the polymer backbone. The diacrylate structure of tripropylene glycol diacrylate provides branching points and imparts sterically hindered chain segments, while N-vinylpyrrolidone introduces polar anchoring groups. Finally, through chain termination and free radical coupling / disproportionation reactions, a stable tripropylene glycol-based copolymer dispersant is formed. After removing the ethyl acetate solvent by vacuum distillation, the target product is obtained.

[0017] Technical effects: The present invention provides a surface modification preparation method for air-stabilized lithium phosphorus sulfide bromide compounds. Compared with the prior art, the present invention has the following significant advantages: 1. A dual modification strategy of scandium oxide doping and phosphorus-modified carbon nanotube coating is adopted to synergistically improve air stability and ionic conductivity. By inhibiting hydrolysis through strong chemical bonds, controlling the crystal structure through doping, and isolating air moisture through the coating layer, the air stability of the material is improved from the root.

[0018] 2. The prepared material has excellent room temperature ion conductivity and stable electrochemical performance, which can meet the high-efficiency ion transport requirements of all-solid-state lithium batteries.

[0019] 3. The material has good compatibility with lithium metal anodes, which can effectively reduce interface impedance and cyclic overpotential, and improve the long-term cycle reliability of all-solid-state batteries. Detailed Implementation

[0020] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples: 1. Ionic conductivity detection: using an electrochemical workstation (frequency 0.01Hz~1×10⁻⁶). 6 The impedance of the mold battery was tested using a frequency (Hz, amplitude 10mV), and the ionic conductivity was calculated using the formula σ=d / (S×R) (where σ is the ionic conductivity, unit S·cm). -1 d represents the thickness of the disc in cm; S represents the area of ​​the disc in cm². 2 R is the impedance value, in Ω).

[0021] 2. Ionic conductivity retention rate: The ionic conductivity of the test sample before exposure (room temperature 25℃) and after exposure (25℃, relative humidity 50% exposure for 24h) is used to calculate the ionic conductivity retention rate (retention rate = ionic conductivity after exposure / ionic conductivity before exposure × 100%).

[0022] 3. Compatibility testing with lithium metal: Using lithium metal as electrodes, assemble lithium|lithium symmetric cells at 0.1 mA·cm⁻¹. -2 Constant current cycling was performed at a current density, and the overpotential was recorded after 600 hours of cycling. The lower the overpotential, the better the compatibility with lithium metal. Example 1

[0023] A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 22g lithium sulfide, 29g phosphorus pentasulfide, 7g elemental sulfur, 15g lithium bromide, and 1g dispersant evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfide bromide compound precursor. S3: Add 0.2g of scandium oxide dopant to 60g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0024] The vacuum drying in S1 is performed at a temperature of 100°C for 12 hours.

[0025] The particles in S1 are crushed and screened to a particle size of 30 μm.

[0026] In S2, the ball-to-material ratio of the ball mill is 30:1, the ball milling speed is 300 r / min, and the ball milling time is 8 h.

[0027] The sintering temperature of the high-temperature sintering in S3 is 500℃, and the sintering time is 3h.

[0028] The acetylene flow rate in S4 is 20 mL / min, and the phosphoric acid flow rate is 10 mL / min.

[0029] The reaction temperature in S4 is 700℃ and the reaction time is 60min.

[0030] The coating layer in S4 has a thickness of 20 nm.

[0031] The method for preparing the dispersant in S2 is as follows: 10g of N-vinylpyrrolidone, 8g of tripropylene glycol diacrylate (CAS No. 42978-66-5), 100g of ethyl acetate, and 0.4g of azobisisobutyronitrile were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 20 minutes, and the reaction was carried out at a higher temperature. Ethyl acetate was removed by vacuum distillation to obtain the dispersant.

[0032] The dispersant was prepared at a temperature of 60°C for 4 hours. Example 2

[0033] A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 30g lithium sulfide, 36g phosphorus pentasulfide, 9g elemental sulfur, 19g lithium bromide, and 2g dispersant evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfur bromide compound precursor. S3: Add 1g of scandium oxide dopant to 70g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0034] The vacuum drying in S1 is performed at a temperature of 105°C for 13 hours.

[0035] The particles in S1 are crushed and screened to a particle size of 40 μm.

[0036] In S2, the ball-to-material ratio of the ball mill is 35:1, the ball milling speed is 350 r / min, and the ball milling time is 9 h.

[0037] The sintering temperature of S3 is 540℃, and the sintering time is 4h.

[0038] The acetylene flow rate in S4 is 24 mL / min, and the phosphoric acid flow rate is 12 mL / min.

[0039] The reaction temperature in S4 is 740℃ and the reaction time is 80 min.

[0040] The coating layer in S4 has a thickness of 30 nm.

[0041] The method for preparing the dispersant in S2 is as follows: 14g of N-vinylpyrrolidone, 10g of tripropylene glycol diacrylate (CAS No. 42978-66-5), 140g of ethyl acetate, and 0.5g of azobisisobutyronitrile were added to a reaction vessel, and nitrogen gas was introduced to remove oxygen for 25 minutes. The reaction was then heated, and ethyl acetate was removed by vacuum distillation to obtain the dispersant.

[0042] The dispersant was prepared at a temperature of 65°C for 5 hours. Example 3

[0043] A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 40g lithium sulfide, 52g phosphorus pentasulfide, 11g elemental sulfur, 23g lithium bromide and 4g dispersant evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfur bromide compound precursor. S3: Add 1.5g of scandium oxide dopant to 90g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0044] The vacuum drying in S1 is performed at a temperature of 115°C for 15 hours.

[0045] The particles in S1 are crushed and screened to a particle size of 40 μm.

[0046] In S2, the ball-to-material ratio of the ball mill is 35:1, the ball milling speed is 350 r / min, and the ball milling time is 11 h.

[0047] The sintering temperature of the high-temperature sintering in S3 is 580℃, and the sintering time is 5h.

[0048] The acetylene flow rate in S4 is 25 mL / min, and the phosphoric acid flow rate is 14 mL / min.

[0049] The reaction temperature in S4 is 780℃ and the reaction time is 100min.

[0050] The coating layer in S4 has a thickness of 40 nm.

[0051] The method for preparing the dispersant in S2 is as follows: 18g of N-vinylpyrrolidone, 14g of tripropylene glycol diacrylate (CAS No. 42978-66-5), 180g of ethyl acetate, and 0.7g of azobisisobutyronitrile were added to a reaction vessel, and nitrogen gas was introduced to remove oxygen for 35 minutes. The reaction was then heated, and ethyl acetate was removed by vacuum distillation to obtain the dispersant.

[0052] The dispersant was prepared at a temperature of 65°C for 7 hours. Example 4

[0053] A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 44g lithium sulfide, 57g phosphorus pentasulfide, 13g elemental sulfur, 27g lithium bromide and 5g dispersant evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfur bromide compound precursor. S3: Add 2g of scandium oxide dopant to 100g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0054] The vacuum drying in S1 is performed at a temperature of 120°C for 16 hours.

[0055] The particles in S1 are crushed and screened to a particle size of 50 μm.

[0056] In S2, the ball-to-material ratio of the ball mill is 40:1, the ball milling speed is 400 r / min, and the ball milling time is 12 h.

[0057] The sintering temperature of the high-temperature sintering in S3 is 600℃, and the sintering time is 6h.

[0058] The acetylene flow rate in S4 is 30 mL / min, and the phosphoric acid flow rate is 15 mL / min.

[0059] The reaction temperature in S4 is 800℃ and the reaction time is 120 min.

[0060] The coating layer in S4 has a thickness of 50 nm.

[0061] The method for preparing the dispersant in S2 is as follows: 20g of N-vinylpyrrolidone, 16g of tripropylene glycol diacrylate (CAS No. 42978-66-5), 200g of ethyl acetate, and 0.8g of azobisisobutyronitrile were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 40 minutes, and the reaction was carried out at a higher temperature. Ethyl acetate was removed by vacuum distillation to obtain the dispersant.

[0062] The dispersant was prepared at a temperature of 70°C for 8 hours.

[0063] Comparative Example 1 A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 22g lithium sulfide, 29g phosphorus pentasulfide, 7g elemental sulfur, and 15g lithium bromide evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfide bromide compound precursor. S3: Add 0.2g of scandium oxide dopant to 60g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0064] The vacuum drying in S1 is performed at a temperature of 100°C for 12 hours.

[0065] The particles in S1 are crushed and screened to a particle size of 30 μm.

[0066] In S2, the ball-to-material ratio of the ball mill is 30:1, the ball milling speed is 300 r / min, and the ball milling time is 8 h.

[0067] The sintering temperature of the high-temperature sintering in S3 is 500℃, and the sintering time is 3h.

[0068] The acetylene flow rate in S4 is 20 mL / min, and the phosphoric acid flow rate is 10 mL / min.

[0069] The reaction temperature in S4 is 700℃ and the reaction time is 60min.

[0070] The coating layer in S4 has a thickness of 20 nm.

[0071] Comparative Example 2 A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 22g lithium sulfide, 29g phosphorus pentasulfide, 7g elemental sulfur, 15g lithium bromide, and 1g dispersant evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfide bromide compound precursor. S3: Add 0.2g of scandium oxide dopant to 60g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0072] The vacuum drying in S1 is performed at a temperature of 100°C for 12 hours.

[0073] The particles in S1 are crushed and screened to a particle size of 30 μm.

[0074] In S2, the ball-to-material ratio of the ball mill is 30:1, the ball milling speed is 300 r / min, and the ball milling time is 8 h.

[0075] The sintering temperature of the high-temperature sintering in S3 is 500℃, and the sintering time is 3h.

[0076] The acetylene flow rate in S4 is 20 mL / min, and the phosphoric acid flow rate is 10 mL / min.

[0077] The reaction temperature in S4 is 700℃ and the reaction time is 60min.

[0078] The coating layer in S4 has a thickness of 20 nm.

[0079] The method for preparing the dispersant in S2 is as follows: 8g of tripropylene glycol diacrylate (CAS No. 42978-66-5), 100g of ethyl acetate, and 0.4g of azobisisobutyronitrile were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 20 minutes, the temperature was raised, and the reaction was carried out. Ethyl acetate was removed by vacuum distillation to obtain the dispersant.

[0080] The dispersant was prepared at a temperature of 60°C for 4 hours.

[0081] Comparative Example 3 A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 22g lithium sulfide, 29g phosphorus pentasulfide, 7g elemental sulfur, 15g lithium bromide, and 1g dispersant evenly and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfide bromide compound precursor. S3: Add 0.2g of scandium oxide dopant to 60g of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped and modified lithium phosphorus sulfide bromide compound is placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction is carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer is deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound is obtained.

[0082] The vacuum drying in S1 is performed at a temperature of 100°C for 12 hours.

[0083] The particles in S1 are crushed and screened to a particle size of 30 μm.

[0084] In S2, the ball-to-material ratio of the ball mill is 30:1, the ball milling speed is 300 r / min, and the ball milling time is 8 h.

[0085] The sintering temperature of the high-temperature sintering in S3 is 500℃, and the sintering time is 3h.

[0086] The acetylene flow rate in S4 is 20 mL / min, and the phosphoric acid flow rate is 10 mL / min.

[0087] The reaction temperature in S4 is 700℃ and the reaction time is 60min.

[0088] The coating layer in S4 has a thickness of 20 nm.

[0089] The method for preparing the dispersant in S2 is as follows: 10g of N-vinylpyrrolidone, 100g of ethyl acetate, and 0.4g of azobisisobutyronitrile were added to a reaction vessel, nitrogen gas was introduced to remove oxygen for 20 minutes, the temperature was raised to react, and ethyl acetate was removed by vacuum distillation to obtain the dispersant.

[0090] The dispersant was prepared at a temperature of 60°C for 4 hours.

[0091] Table 1 shows the ionic conductivity, ionic conductivity retention rate, and overpotential detection results of lithium, phosphorus, sulfide, and bromide compounds in the specific implementation plan. <![CDATA[Ionic conductivity (mS·cm -1 ).]]> Ion conductivity retention rate (%) Overpotential (mV) after 600 hours of cycling Example 1 5.69 89.7 63 Example 2 5.76 90.5 61 Example 3 5.85 91.3 57 Example 4 5.93 92.1 55 Comparative Example 1 4.01 62.6 122 Comparative Example 2 5.17 82.8 93 Comparative Example 3 5.22 83.5 87 Table 1. Summary of ionic conductivity, ionic conductivity retention, and overpotential detection results for lithium, phosphorus, sulfide, and bromide compounds after 600 hours of cycling. All indicators in the examples are significantly better than those in the comparative examples, fully verifying that the preparation method can achieve a synergistic improvement in air stability and ionic conductivity. The tripropylene glycol-based dispersant plays a key role: the polar anchoring group of N-vinylpyrrolidone can tightly adsorb onto the powder surface and enhance the dispersion effect; tripropylene glycol diacrylate provides steric hindrance to avoid particle agglomeration; and azobisisobutyronitrile (AIBN) acts as an initiator to ensure efficient copolymerization. The synergistic effect of the three makes the raw material mixing more uniform and the ball milling and sintering reactions more complete, ultimately improving the ionic conductivity, air stability and compatibility with lithium metal anodes of the material.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification, comprising the following steps, in parts by mass: S1: Lithium sulfide is vacuum dried in an argon glove box; phosphorus pentasulfide, elemental sulfur, and lithium bromide are crushed and sieved in an argon atmosphere. S2: Mix 22-44 parts lithium sulfide, 29-57 parts phosphorus pentasulfide, 7-13 parts elemental sulfur, 15-27 parts lithium bromide, and 1-5 parts dispersant evenly, and place them in a planetary ball mill. Ball milling is carried out under the protection of argon to obtain lithium phosphorus sulfur bromide compound precursor. S3: Add 0.2-2 parts of scandium oxide dopant to 60-100 parts of precursor, mix evenly, place in a tube furnace, sinter at high temperature under argon atmosphere, and then cool naturally to room temperature to obtain doped modified lithium phosphorus sulfide bromide compound. S4: The doped modified lithium phosphorus sulfide bromide compound was placed in a reactor, with acetylene as the carbon source and phosphoric acid as the phosphorus source. The reaction was carried out under an argon atmosphere, and a phosphorus-modified carbon nanotube coating layer was deposited on the surface of the compound. After cooling, an air-stable lithium phosphorus sulfide bromide compound was obtained. The dispersant in S2 is prepared by reacting N-vinylpyrrolidone, tripropylene glycol diacrylate, and azobisisobutyronitrile.

2. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification according to claim 1, characterized in that: The vacuum drying temperature in S1 is 100-120℃, and the time is 12-16h.

3. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification according to claim 1, characterized in that: The particles in S1 are crushed and screened to a particle size of 30-50 μm.

4. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification according to claim 1, characterized in that: In S2, the ball-to-material ratio of the ball mill is 30-40:1, the ball milling speed is 300-400 r / min, and the ball milling time is 8-12 h.

5. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification according to claim 1, characterized in that: The sintering temperature of the high-temperature sintering in S3 is 500-600℃, and the sintering time is 3-6h.

6. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound according to claim 1, characterized in that: The acetylene flow rate in S4 is 20-30 mL / min, and the phosphoric acid flow rate is 10-15 mL / min.

7. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound by surface modification according to claim 1, characterized in that: The reaction temperature in S4 is 700-800℃, and the reaction time is 60-120 min.

8. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound according to claim 1, characterized in that: The coating layer in S4 has a thickness of 20-50 nm.

9. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound according to claim 1, characterized in that: The method for preparing the dispersant in S2 is as follows: According to the mass fractions, 10-20 parts of N-vinylpyrrolidone, 8-16 parts of tripropylene glycol diacrylate, 100-200 parts of ethyl acetate, and 0.4-0.8 parts of azobisisobutyronitrile are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 20-40 minutes, the temperature is raised to react, and ethyl acetate is removed by vacuum distillation to obtain the dispersant.

10. The method for preparing an air-stabilized lithium phosphorus sulfide bromide compound according to claim 9, characterized in that: The heating reaction temperature during the preparation of the dispersant is 60-70℃, and the time is 4-8 hours.