A composite modification method of lithium phosphorus sulfur bromide compound coated with nano-oxide

Abstract

This invention relates to a composite modification method for coating lithium phosphorus, sulfide, and bromine compounds with nano-oxides, and pertains to the field of solid-state electrolyte technology. The method involves drying lithium phosphorus, sulfide, and bromine powder, adding a dispersant, and performing graded ball milling to obtain a lithium phosphorus, sulfide, and bromine substrate powder. Nano-alumina powder is dispersed in anhydrous ethanol, and oleic acid and polyvinylidene fluoride are added to obtain a nano-oxide coating solution. The lithium phosphorus, sulfide, and bromine substrate powder is slowly added to the coating solution to perform an in-situ coating reaction, forming a coating precursor. The coating precursor is then vacuum dried and subjected to low-temperature crystallization to obtain a primary composite modified material. The primary composite modified material is then subjected to secondary ball milling and sieving to obtain a nano-oxide-coated lithium phosphorus, sulfide, and bromine compound composite modified material. This invention can significantly improve the room temperature ionic conductivity, water and oxygen stability, and battery cycle performance of the material.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and in particular to a composite modification method for coating lithium, phosphorus, sulfide, and bromine compounds with nano-oxides. Background Technology

[0002] In solid-state electrolyte systems, sulfide-based solid-state electrolytes have attracted widespread attention due to their high room-temperature ionic conductivity, low interfacial impedance, and excellent electrochemical stability. Among them, the lithium-phosphorus-sulfur-bromine system with a sulfo-silver-germanium mineral structure is a typical sulfide solid-state electrolyte material, which shows great application potential in the field of all-solid-state lithium batteries due to its high ionic conductivity, good chemical stability, and low interfacial impedance.

[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 material is subjected to raw material pretreatment, mechanochemical ball milling, high-temperature crystallization treatment, and post-treatment processes to obtain the lithium-phosphorus-sulfur-bromine solid electrolyte.

[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 nano-oxide coating processes suffer from problems such as easy agglomeration of nanoparticles, difficulty in controlling coating layer thickness, and poor synergy between coating and crystallization processes, resulting in poor modification effects. Summary of the Invention

[0006] To address the above problems, this invention provides a method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, the operation steps of which are as follows: S1: Under an argon atmosphere, 100-150 parts of lithium phosphorus sulfide bromine powder are vacuum dried, 2-7 parts of dispersant are added, and then graded ball milling is performed to obtain lithium phosphorus sulfide bromine base powder with uniform particle size. S2: Disperse 5-15 parts of nano-alumina powder in 100-200 parts of anhydrous ethanol, add 0.5-3 parts of oleic acid and 1-5 parts of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 100-150 parts of lithium phosphorus sulfur bromide base material powder to 50-80 parts of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is ball-milled a second time and passed through a 200-300 mesh sieve to remove agglomerated particles, resulting in a 5-20 nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0007] Optionally, the vacuum drying temperature in S1 is 80-120℃, and the drying time is 4-8h.

[0008] Optionally, the graded ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 200-300 r / min and the time is 2-4 h. The fine grinding speed is 400-500 r / min and the time is 1-2 h. The ball-to-material ratio is 80-120:1 and the particle size of the substrate powder after ball milling is 1-5 μm.

[0009] Optionally, the ultrasonic dispersion power in S2 is 150-250W, and the time is 30-60min.

[0010] Optionally, the stirring speed in S2 is 300-500 r / min, and the stirring time is 1-2 h.

[0011] Optionally, in step S3, the stirring temperature is 40-60℃, the stirring speed is 200-300 r / min, and the coating reaction time is 2-4 h.

[0012] Optionally, the vacuum drying temperature in S4 is 60-80℃, and the drying time is 6-10h.

[0013] Optionally, the low-temperature crystallization temperature in S4 is 200-400℃, and the crystallization time is 4-8h.

[0014] Optionally, in S5, the secondary ball milling speed is 300-400 r / min, and the time is 30-60 min.

[0015] Optionally, the dispersant in S1 is prepared by: According to the mass fractions, 10-20 parts of perfluorooctyl polyoxyethylene ether, 6-12 parts of 85wt% concentrated phosphoric acid, 0.05-0.5 parts of allyl glycidyl ether, copolymer of ethylene glycol, 100-200 parts of toluene, and 0.1-0.4 parts of triethylamine are added to the reactor. Nitrogen gas is introduced to remove oxygen for 15-30 minutes, and the temperature is raised to 75-85℃ to react for 4-8 hours. Toluene is removed by vacuum distillation, and the mixture is washed and dried under vacuum at 65-75℃ for 4-8 hours to obtain the dispersant.

[0016] Reaction mechanism: This reaction uses perfluorooctyl polyoxyethylene ether and concentrated phosphoric acid as the main raw materials. Under the conditions of triethylamine catalysis, toluene as an inert solvent, and nitrogen protection, esterification and phosphorylation reactions occur at 75-85℃. The terminal hydroxyl groups of perfluorooctyl polyoxyethylene ether undergo dehydration esterification with the P-OH groups of concentrated phosphoric acid to generate mono / dialkyl phosphate structures. At the same time, allyl glycidyl ether-ethylene glycol copolymer (CAS: 41630-20-0) is introduced as an active dispersant and modifying component. The molecular chain is branched and stabilized through ring-opening addition of epoxy groups, hydroxyl groups, and phosphoric acid groups. Triethylamine neutralizes the protons generated in the reaction to promote the forward esterification equilibrium. After the reaction is completed, toluene is removed by vacuum distillation, followed by washing, purification, and vacuum drying to finally obtain a stable perfluorooctyl polyoxyethylene ether phosphate product.

[0017] Technical effects: This invention provides a composite modification method for coating lithium, phosphorus, sulfide, and bromide compounds with nano-oxides. Compared with existing technologies, this invention has the following significant advantages: 1. By using in-situ coating of nano-alumina and low-temperature crystallization for synergistic modification, a uniform and dense protective layer is formed on the material surface, stabilizing the crystal structure and significantly improving room temperature ion conduction performance.

[0018] 2. The nano-oxide coating effectively isolates water and oxygen erosion, inhibits material degradation, and significantly enhances the air and water oxygen stability of lithium, phosphorus, sulfur, and bromine compounds.

[0019] 3. Optimize interface contact state and reduce interface impedance to significantly improve the cycle stability and long-term service 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. Room temperature ionic conductivity detection: The AC impedance method was used with an electrochemical workstation at room temperature (25℃), with a frequency range of 1Hz~1MHz and an amplitude of 5mV. The impedance spectrum of the sample was tested, and the room temperature ionic conductivity (σ=d / (R×S)) was calculated from the impedance spectrum.

[0021] 2. Water and oxygen stability test: Place the sample in air at room temperature (25℃) and humidity of 50%±5% for 72 hours. Detect the change rate of ionic conductivity of the sample before and after standing. Change rate = (conductivity before standing - conductivity after standing) / conductivity before standing × 100%. The smaller the change rate, the better the water and oxygen stability.

[0022] 3. Capacity retention test: The all-solid-state lithium battery (positive electrode: LiCoO2, negative electrode: metallic Li, electrolyte: lithium phosphorus sulfur bromide compound prepared in the examples and comparative examples) was assembled and charged and discharged at a rate of 0.5C at room temperature (25°C). The capacity retention rate after 500 cycles was tested (discharge capacity after 500 cycles / initial discharge capacity × 100%). Example 1

[0023] A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 100g of lithium phosphorus sulfide bromide powder was vacuum dried, 2g of dispersant was added, and then the powder was subjected to graded ball milling to obtain lithium phosphorus sulfide bromide base powder with uniform particle size. S2: Disperse 5g of nano-alumina powder in 100g of anhydrous ethanol, add 0.5g of oleic acid and 1g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 100g of lithium phosphorus sulfur bromide substrate powder to 50g of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 200-mesh sieve to remove agglomerated particles, resulting in a 5nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0024] The vacuum drying temperature in S1 is 80℃, and the drying time is 4h.

[0025] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 200 r / min and the time is 2 h; the fine grinding speed is 400 r / min and the time is 1 h. The ball-to-material ratio is 80:1 and the particle size of the substrate powder after ball milling is 1 μm.

[0026] In S2, the ultrasonic dispersion power is 150W and the time is 30min.

[0027] In S2, the stirring speed is 300 r / min and the stirring time is 1 h.

[0028] The stirring temperature in S3 is 40℃, the stirring speed is 200r / min, and the coating reaction time is 2h.

[0029] The vacuum drying temperature in S4 is 60℃, and the drying time is 6h.

[0030] The low-temperature crystallization temperature in S4 is 200℃, and the crystallization time is 4h.

[0031] In S5, the secondary ball milling speed is 300 r / min and the time is 30 min.

[0032] The method for preparing the dispersant in S1 is as follows: 10g of perfluorooctyl polyoxyethylene ether, 6g of 85wt% concentrated phosphoric acid, 0.05g of allyl glycidyl ether, a copolymer of ethylene glycol (CAS: 41630-20-0), 100g of toluene, and 0.1g of triethylamine were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 15 minutes, and the temperature was raised to 75℃ and reacted for 4 hours. Toluene was removed by vacuum distillation, and the mixture was washed and dried under vacuum at 65℃ for 4 hours to obtain the dispersant. Example 2

[0033] A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 110g of lithium phosphorus sulfide bromine powder was vacuum dried, 3g of dispersant was added, and then graded ball milling was performed to obtain lithium phosphorus sulfide bromine base powder with uniform particle size. S2: Disperse 8g of nano-alumina powder in 140g of anhydrous ethanol, add 1.5g of oleic acid and 2g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 110g of lithium phosphorus sulfur bromide base powder to 60g of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form coating precursor; S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 250-mesh sieve to remove agglomerated particles, resulting in a 10nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0034] The vacuum drying temperature in S1 is 90℃, and the drying time is 5h.

[0035] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 250 r / min and the time is 3 h; the fine grinding speed is 450 r / min and the time is 1.5 h. The ball-to-material ratio is 90:1 and the particle size of the substrate powder after ball milling is 2 μm.

[0036] In S2, the ultrasonic dispersion power is 180W and the time is 40min.

[0037] In S2, the stirring speed is 400 r / min and the stirring time is 1.5 h.

[0038] The stirring temperature in S3 is 45℃, the stirring speed is 250r / min, and the coating reaction time is 3h.

[0039] The vacuum drying temperature in S4 is 65℃, and the drying time is 7h.

[0040] The low-temperature crystallization temperature in S4 is 250℃, and the crystallization time is 5h.

[0041] In S5, the secondary ball milling speed is 350 r / min and the time is 40 min.

[0042] The method for preparing the dispersant in S1 is as follows: 14g of perfluorooctyl polyoxyethylene ether, 8g of 85wt% concentrated phosphoric acid, 0.2g of allyl glycidyl ether, a copolymer of ethylene glycol (CAS: 41630-20-0), 140g of toluene, and 0.2g of triethylamine were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 20 minutes, and the temperature was raised to 78℃ and reacted for 5 hours. Toluene was removed by vacuum distillation, and the mixture was washed and dried under vacuum at 68℃ for 5 hours to obtain the dispersant. Example 3

[0043] A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 140g of lithium phosphorus sulfide bromine powder was vacuum dried, 6g of dispersant was added, and then graded ball milling was performed to obtain lithium phosphorus sulfide bromine base powder with uniform particle size. S2: Disperse 13g of nano-alumina powder in 180g of anhydrous ethanol, add 2.5g of oleic acid and 4g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 140g of lithium phosphorus sulfur bromide substrate powder to 70g of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 250-mesh sieve to remove agglomerated particles, resulting in a 15nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0044] The vacuum drying temperature in S1 is 110℃, and the drying time is 7h.

[0045] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 250 r / min and the time is 3 h; the fine grinding speed is 450 r / min and the time is 1.5 h. The ball-to-material ratio is 110:1 and the particle size of the substrate powder after ball milling is 4 μm.

[0046] In S2, the ultrasonic dispersion power is 230W and the time is 50min.

[0047] In S2, the stirring speed is 400 r / min and the stirring time is 1.5 h.

[0048] The stirring temperature in S3 is 55℃, the stirring speed is 250r / min, and the coating reaction time is 3h.

[0049] The vacuum drying temperature in S4 is 75℃, and the drying time is 9h.

[0050] The low-temperature crystallization temperature in S4 is 350℃, and the crystallization time is 7h.

[0051] In S5, the secondary ball milling speed is 350 r / min and the time is 50 min.

[0052] The method for preparing the dispersant in S1 is as follows: 18g of perfluorooctyl polyoxyethylene ether, 10g of 85wt% concentrated phosphoric acid, 0.4g of allyl glycidyl ether, a copolymer of ethylene glycol (CAS: 41630-20-0), 180g of toluene, and 0.3g of triethylamine were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 25 minutes, and the temperature was raised to 83℃ and reacted for 7 hours. Toluene was removed by vacuum distillation, and the mixture was washed and dried under vacuum at 73℃ for 7 hours to obtain the dispersant. Example 4

[0053] A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 150g of lithium phosphorus sulfide bromide powder was vacuum dried, 7g of dispersant was added, and then the powder was subjected to graded ball milling to obtain lithium phosphorus sulfide bromide base powder with uniform particle size. S2: Disperse 15g of nano-alumina powder in 200g of anhydrous ethanol, add 3g of oleic acid and 5g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 150g of lithium phosphorus sulfur bromine substrate powder to 80g of coating solution, and carry out in-situ coating reaction under constant temperature stirring to form coating precursor; S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 300-mesh sieve to remove agglomerated particles, resulting in a 20nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0054] The vacuum drying temperature in S1 is 120℃, and the drying time is 8h.

[0055] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 300 r / min and the time is 4 h; the fine grinding speed is 500 r / min and the time is 2 h. The ball-to-material ratio is 120:1 and the particle size of the substrate powder after ball milling is 5 μm.

[0056] In S2, the ultrasonic dispersion power is 250W and the time is 60min.

[0057] In S2, the stirring speed is 500 r / min and the stirring time is 2 h.

[0058] The stirring temperature in S3 is 60℃, the stirring speed is 300r / min, and the coating reaction time is 4h.

[0059] The vacuum drying temperature in S4 is 80℃, and the drying time is 10h.

[0060] The low-temperature crystallization temperature in S4 is 400℃, and the crystallization time is 8h.

[0061] In S5, the secondary ball milling speed is 400 r / min and the time is 60 min.

[0062] The method for preparing the dispersant in S1 is as follows: 20g of perfluorooctyl polyoxyethylene ether, 12g of 85wt% concentrated phosphoric acid, 0.5g of allyl glycidyl ether, a copolymer of ethylene glycol (CAS: 41630-20-0), 200g of toluene, and 0.4g of triethylamine were added to a reactor. Nitrogen gas was introduced to remove oxygen for 30 minutes, and the temperature was raised to 85℃ and reacted for 8 hours. Toluene was removed by vacuum distillation, and the mixture was washed and dried under vacuum at 75℃ for 8 hours to obtain the dispersant.

[0063] Comparative Example 1 A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 100g of lithium phosphorus sulfide bromine powder was vacuum dried and then subjected to graded ball milling to obtain lithium phosphorus sulfide bromine base powder with uniform particle size. S2: Disperse 5g of nano-alumina powder in 100g of anhydrous ethanol, add 0.5g of oleic acid and 1g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 100g of lithium phosphorus sulfur bromide substrate powder to 50g of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 200-mesh sieve to remove agglomerated particles, resulting in a 5nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0064] The vacuum drying temperature in S1 is 80℃, and the drying time is 4h.

[0065] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 200 r / min and the time is 2 h; the fine grinding speed is 400 r / min and the time is 1 h. The ball-to-material ratio is 80:1 and the particle size of the substrate powder after ball milling is 1 μm.

[0066] In S2, the ultrasonic dispersion power is 150W and the time is 30min.

[0067] In S2, the stirring speed is 300 r / min and the stirring time is 1 h.

[0068] The stirring temperature in S3 is 40℃, the stirring speed is 200r / min, and the coating reaction time is 2h.

[0069] The vacuum drying temperature in S4 is 60℃, and the drying time is 6h.

[0070] The low-temperature crystallization temperature in S4 is 200℃, and the crystallization time is 4h.

[0071] In S5, the secondary ball milling speed is 300 r / min and the time is 30 min.

[0072] Comparative Example 2 A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 100g of lithium phosphorus sulfide bromide powder was vacuum dried, 2g of dispersant was added, and then the powder was subjected to graded ball milling to obtain lithium phosphorus sulfide bromide base powder with uniform particle size. S2: Disperse 5g of nano-alumina powder in 100g of anhydrous ethanol, add 0.5g of oleic acid and 1g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 100g of lithium phosphorus sulfur bromide substrate powder to 50g of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 200-mesh sieve to remove agglomerated particles, resulting in a 5nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0073] The vacuum drying temperature in S1 is 80℃, and the drying time is 4h.

[0074] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 200 r / min and the time is 2 h; the fine grinding speed is 400 r / min and the time is 1 h. The ball-to-material ratio is 80:1 and the particle size of the substrate powder after ball milling is 1 μm.

[0075] In S2, the ultrasonic dispersion power is 150W and the time is 30min.

[0076] In S2, the stirring speed is 300 r / min and the stirring time is 1 h.

[0077] The stirring temperature in S3 is 40℃, the stirring speed is 200r / min, and the coating reaction time is 2h.

[0078] The vacuum drying temperature in S4 is 60℃, and the drying time is 6h.

[0079] The low-temperature crystallization temperature in S4 is 200℃, and the crystallization time is 4h.

[0080] In S5, the secondary ball milling speed is 300 r / min and the time is 30 min.

[0081] The method for preparing the dispersant in S1 is as follows: 6g of 85wt% concentrated phosphoric acid, 0.05g of allyl glycidyl ether, a copolymer of ethylene glycol (CAS: 41630-20-0), 100g of toluene, and 0.1g of triethylamine were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 15 minutes, and the temperature was raised to 75℃ and reacted for 4 hours. Toluene was removed by vacuum distillation, and the mixture was washed and dried under vacuum at 65℃ for 4 hours to obtain the dispersant.

[0082] Comparative Example 3 A method for composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps: S1: Under an argon atmosphere, 100g of lithium phosphorus sulfide bromide powder was vacuum dried, 2g of dispersant was added, and then the powder was subjected to graded ball milling to obtain lithium phosphorus sulfide bromide base powder with uniform particle size. S2: Disperse 5g of nano-alumina powder in 100g of anhydrous ethanol, add 0.5g of oleic acid and 1g of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 100g of lithium phosphorus sulfur bromide substrate powder to 50g of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is subjected to secondary ball milling and passed through a 200-mesh sieve to remove agglomerated particles, resulting in a 5nm thick nano-oxide-coated lithium phosphorus sulfur bromine compound composite modified material.

[0083] The vacuum drying temperature in S1 is 80℃, and the drying time is 4h.

[0084] The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 200 r / min and the time is 2 h; the fine grinding speed is 400 r / min and the time is 1 h. The ball-to-material ratio is 80:1 and the particle size of the substrate powder after ball milling is 1 μm.

[0085] In S2, the ultrasonic dispersion power is 150W and the time is 30min.

[0086] In S2, the stirring speed is 300 r / min and the stirring time is 1 h.

[0087] The stirring temperature in S3 is 40℃, the stirring speed is 200r / min, and the coating reaction time is 2h.

[0088] The vacuum drying temperature in S4 is 60℃, and the drying time is 6h.

[0089] The low-temperature crystallization temperature in S4 is 200℃, and the crystallization time is 4h.

[0090] In S5, the secondary ball milling speed is 300 r / min and the time is 30 min.

[0091] The method for preparing the dispersant in S1 is as follows: 10g of perfluorooctyl polyoxyethylene ether, 0.05g of allyl glycidyl ether, and a copolymer of ethylene glycol (CAS: 41630-20-0), 100g of toluene, and 0.1g of triethylamine were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen for 15 minutes, and the temperature was raised to 75°C and reacted for 4 hours. Toluene was removed by vacuum distillation, and the mixture was washed and dried under vacuum at 65°C for 4 hours to obtain the dispersant.

[0092] Table 1. Results of room temperature ionic conductivity, 72-hour static conductivity change rate, and capacity retention of lithium, phosphorus, sulfide, and bromide compounds in the specific implementation scheme. <![CDATA[Room temperature ionic conductivity (×10 -3 S / cm)]]> Change rate of conductivity of air after 72 hours of static storage (%) Capacity retention rate (%) Example 1 3.28 2.83 95.28 Example 2 3.33 2.75 95.33 Example 3 3.45 2.66 95.46 Example 4 3.52 2.59 95.57 Comparative Example 1 1.13 13.61 75.61 Comparative Example 2 2.76 6.35 88.74 Comparative Example 3 2.84 5.81 89.95 The example significantly outperformed the comparative example in terms of room temperature ionic conductivity, water and oxygen stability, and cycle capacity retention, fully demonstrating the outstanding effect of this composite modification method. The perfluorooctyl polyoxyethylene ether phosphate dispersant components synergistically play a key role: perfluorooctyl polyoxyethylene ether provides strong hydrophobicity and surface anchoring ability, improving powder dispersibility and water and oxygen resistance; concentrated phosphoric acid provides phosphate ester active sites, enhancing the binding force between the dispersant and the particle surface; allyl glycidyl ether-ethylene glycol copolymer improves the compatibility and film uniformity of the dispersant, avoiding coating defects; triethylamine acts as a catalyst to ensure efficient and complete reaction, improving the purity and stability of the dispersant. The synergistic effect of these components leads to more uniform ball milling, more complete coating, and more thorough crystallization, ultimately achieving a simultaneous improvement in material conductivity, stability, and battery cycle performance.

[0093] 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 composite modification of lithium, phosphorus, sulfide, and bromine compounds by coating nano-oxides, comprising the following steps, in parts by mass: S1: Under an argon atmosphere, 100-150 parts of lithium phosphorus sulfide bromine powder are vacuum dried, 2-7 parts of dispersant are added, and then graded ball milling is performed to obtain lithium phosphorus sulfide bromine base powder with uniform particle size. S2: Disperse 5-15 parts of nano-alumina powder in 100-200 parts of anhydrous ethanol, add 0.5-3 parts of oleic acid and 1-5 parts of polyvinylidene fluoride, and then disperse and mix by ultrasonication to obtain a uniform and stable nano-oxide coating solution. S3: Slowly add 100-150 parts of lithium phosphorus sulfur bromide base material powder to 50-80 parts of coating solution, and carry out in-situ coating reaction under constant temperature and stirring conditions to form a coating precursor. S4: The coated precursor is vacuum dried to remove the solvent, and then placed in an argon atmosphere for low-temperature crystallization treatment to obtain a primary composite modified material. S5: The primary composite modified material is ball-milled twice and passed through a 200-300 mesh sieve to remove agglomerated particles, resulting in a lithium phosphorus sulfur bromine compound composite modified material with a coating layer thickness of 5-20nm nano-oxide. The dispersant in S1 is prepared by reacting a copolymer of perfluorooctyl polyoxyethylene ether, 85wt% concentrated phosphoric acid, allyl glycidyl ether, ethylene glycol, and triethylamine.

2. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The vacuum drying temperature in S1 is 80-120℃, and the drying time is 4-8h.

3. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The ball milling in S1 is divided into coarse grinding and fine grinding. The coarse grinding speed is 200-300 r / min and the time is 2-4 h. The fine grinding speed is 400-500 r / min and the time is 1-2 h. The ball-to-material ratio is 80-120:

1. The particle size of the substrate powder after ball milling is 1-5 μm.

4. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The ultrasonic dispersion power in S2 is 150-250W, and the time is 30-60min.

5. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The stirring speed in S2 is 300-500 r / min, and the stirring time is 1-2 h.

6. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The stirring temperature in S3 is 40-60℃, the stirring speed is 200-300r / min, and the coating reaction time is 2-4h.

7. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The vacuum drying temperature in S4 is 60-80℃, and the drying time is 6-10h.

8. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The low-temperature crystallization temperature in S4 is 200-400℃, and the crystallization time is 4-8h.

9. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: In S5, the secondary ball milling speed is 300-400 r / min, and the time is 30-60 min.

10. The method for composite modification of lithium, phosphorus, sulfide, and bromine compounds coated with nano-oxides according to claim 1, characterized in that: The method for preparing the dispersant in S1 is as follows: According to the mass fractions, 10-20 parts of perfluorooctyl polyoxyethylene ether, 6-12 parts of 85wt% concentrated phosphoric acid, 0.05-0.5 parts of allyl glycidyl ether, copolymer of ethylene glycol, 100-200 parts of toluene, and 0.1-0.4 parts of triethylamine are added to the reactor. Nitrogen gas is introduced to remove oxygen for 15-30 minutes, and the temperature is raised to 75-85℃ to react for 4-8 hours. Toluene is removed by vacuum distillation, and the mixture is washed and dried under vacuum at 65-75℃ for 4-8 hours to obtain the dispersant.