Sulfide solid electrolyte and preparation method and application thereof

Abstract

The application relates to a sulfide solid electrolyte and a preparation method and application thereof, and the composition is 70R2S-(30-x)SiS2-xM a O b , wherein R is Li or Na, x is 0.1-10, M a O b is a metal oxide, and a and b are natural numbers. The sulfide solid electrolyte of the application improves ion conductivity by adding a metal oxide as a network modifier in a Li2S-SiS2 sulfide solid electrolyte system. The solid electrolyte of the application has the characteristics of electrochemical stability and environmental friendliness, and provides a solid electrolyte material for a full solid-state secondary battery which has higher charge-discharge capacity while inhibiting the generation of hydrogen sulfide and can be charged and discharged at a higher current density.

Description

Technical Field

[0001] This application relates to the field of chemical energy technology, and in particular to a sulfide solid electrolyte, its preparation method and application. Background Technology

[0002] Traditional lithium-ion batteries use organic liquids as electrolytes for lithium-ion transport, but this is prone to leakage, gas buildup, and in severe cases, even battery combustion and explosion, posing safety hazards. All-solid-state lithium batteries use all-solid-state electrolytes instead of the separators and electrolytes found in traditional batteries for lithium-ion transport, making them safer than organic electrolytes. However, the application of sulfide solid electrolytes in all-solid-state lithium batteries still faces many challenges, such as electrochemical stability, compatibility with electrode materials, thermal stability, mechanical properties, and cost, all of which should be fully considered. A key issue is their sensitivity to air, easily reacting with water in the air to produce the toxic gas hydrogen sulfide. Furthermore, sulfides react with the lithium metal anode, forming substances with poor ion conductivity, which is detrimental to lithium-ion migration.

[0003] Currently, the Li2S-P2S5 sulfide solid electrolytes that have been widely reported have the following problems: P2S5 is highly toxic and unsuitable for production; the melting points of P2S5 and Li2S are too different, and when Li2S melts, the polymer macromolecular chains of P2S5 have already partially degenerated; the electrochemical performance of Li2S-P2S5 sulfide solid electrolytes is unstable and the conductivity is poor. Summary of the Invention

[0004] Based on this, this application provides a sulfide solid electrolyte and its preparation method to solve the problems of unstable electrochemical performance and poor conductivity of traditional sulfide solid electrolytes such as Li2S-P2S5.

[0005] One of the objectives of this application is to provide a sulfide solid electrolyte and its preparation method and application. By adding metal oxides as a network modifier, the ionic conductivity is improved, forming a sulfide solid electrolyte containing metal oxides, thereby improving the electrochemical stability of existing sulfide solid electrolytes and increasing ionic conductivity.

[0006] To solve this technical problem, the technical solution of this application is: a sulfide solid electrolyte and its preparation method and application, including the following steps:

[0007] A sulfide solid electrolyte, characterized in that its chemical formula is 70R2S—(30-x)SiS2—xM a O b Where R includes Li, Na, or a combination of both, x is 0.1~10, and M a O bIt is a metal oxide, and a and b are natural numbers.

[0008] In one embodiment, x is 0.1 to 5.

[0009] In one embodiment, the M a O b Including one or more of Bi2O3, Cu2O and SnO2, optionally, M a O b It is Bi2O3.

[0010] In one embodiment, its chemical formula is 70Li2S—29SiS2—1Bi2O3

[0011] In one embodiment, the method for preparing the sulfide solid electrolyte includes the following steps.

[0012] S1, R2S, SiS2 and M a O b After mixing in a preset ratio, the mixture is ground. The ground material is then mixed with an organic solvent and ball-milled to obtain a solid electrolyte precursor.

[0013] S2. The solid electrolyte precursor is heat-treated and cooled to obtain a sulfide solid electrolyte.

[0014] S3. The sulfide solid electrolyte is crushed.

[0015] In one embodiment, both the ball milling in step S1 and the heat treatment in step S2 are performed under a protective atmosphere.

[0016] In one embodiment, the ball mill in step S1 is made of cemented carbide, with a large ball diameter of 25~30mm, a small ball diameter of 5~10mm, a ball mill rotation speed of 300~500r / min, a ball milling time of 1~2h, a large ball to small ball ratio of (1~3):1, and a ball to material ratio of (5~15):1.

[0017] In one embodiment, the temperature change in step S2 is a step-by-step increase, the process includes heat treatment at 800~900℃ for 0.5~1.5h, heat treatment at 900~1000℃ for 0.5~1h, and heat treatment at 1000~1100℃ for 0.5~1h, and the temperature rise rate of the adjacent heat treatment temperature stages is 8~12℃ / min.

[0018] In one embodiment, the cooling process in step S2 is to cool to room temperature at a temperature decrease rate of 8~12°C / min.

[0019] In one embodiment, the pulverization in step S3 includes multi-stage pulverization until the particle size D50 of the pulverized solid electrolyte is 8μm~12μm.

[0020] This application also provides a secondary battery, which includes the aforementioned sulfide solid electrolyte.

[0021] This application also provides an electrical device, wherein the driving source or energy storage source of the electrical device is the secondary battery.

[0022] The sulfide solid electrolyte of this application improves ionic conductivity by adding metal oxides as network modifiers to the Li2S-SiS2 sulfide solid electrolyte system. This solves the technical problem that the ionic conductivity of existing Li2S-SiS2 sulfide solid electrolytes is inferior to that of Li2S-P2S5 sulfide solid electrolytes without adding the highly toxic substance P2S5. The solid electrolyte of this application combines electrochemical stability with environmental friendliness, and provides a solid electrolyte material for all-solid-state secondary batteries that suppresses hydrogen sulfide generation while exhibiting higher charge-discharge capacity and the ability to charge and discharge at higher current densities.

[0023] Furthermore, when at least one of the positive and negative electrodes contains the solid electrolyte material, an all-solid-state secondary battery that combines electrochemical stability and environmental friendliness can be provided. Attached Figure Description

[0024] Figure 1 Flowchart for the preparation of sulfide solid electrolytes. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments and examples. It should be understood that these embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to enable understanding, and they are not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0026] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0027] the term

[0028] The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0029] The terms “combinations thereof,” “any combination thereof,” and “any combination thereof” as used in this application include all suitable combinations of any two or more of the listed items.

[0030] In this application, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0031] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are merely used to describe implementation methods or embodiments that achieve better results, and should be understood not to limit the scope of protection of this application.

[0032] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0033] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0034] Sulfide solid electrolytes: Sulfide solid electrolytes are derived from oxide solid electrolytes. In oxide solid electrolytes, oxygen is replaced by sulfur, forming sulfide solid electrolytes.

[0035] Ball mill: A ball mill uses the impact of falling grinding media (such as steel balls, pebbles, etc.) and the grinding action between the grinding media and the inner wall of the ball mill to crush and mix materials.

[0036] Heat treatment: refers to a metal heat treatment process in which materials are heated, held at temperature and cooled in a solid state to obtain the desired structure and properties.

[0037] Inert gases: Noble gases refer to the gaseous elements corresponding to all elements in Group 0 of the periodic table, also known as inert gases. At room temperature and pressure, they are colorless and odorless monatomic gases, and are very difficult to react chemically.

[0038] One of the objectives of this application is to provide a sulfide solid electrolyte and its preparation method and application. By adding metal oxides as a network modifier, the ionic conductivity is improved, forming a sulfide solid electrolyte containing metal oxides, thereby improving the electrochemical stability of existing sulfide solid electrolytes and increasing ionic conductivity.

[0039] One embodiment of this application provides a sulfide solid electrolyte with the composition 70R2S—(30-x)SiS2—xM. a O b Where R includes Li, Na, or a combination of both, x is 0.1~10, and M a O b For metal oxides, a and b are natural numbers. The reason why sulfide solid electrolytes have better stability than existing sulfide solid electrolytes is because they are doped with M. a O b The reaction principle is based on the hard-soft acid-base theory. When soft tin replaces hard phosphorus, it more readily combines with the soft base sulfur, rather than the hard base oxygen, thus inhibiting its reaction with water in the air. The synergistic effect of both improves the (chemical) stability of the air. Hard acids have a small central atom with a high positive charge and low polarizability, while soft acids have a large central atom with a low positive charge and high polarizability. Coordinating atoms with high electronegativity, low polarizability, and difficulty in oxidation are called hard bases, and vice versa. Hard acids and hard bases are primarily driven by Coulomb forces; soft acids and soft bases are primarily driven by covalent bonds (interatomic forces in covalent compounds).

[0040] In a specific example, x is between 0.1 and 5, such as 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.

[0041] Optionally, M a O b Including one or more of Bi2O3, Cu2O and SnO2, optionally, M a O b It is Bi2O3.

[0042] In a specific example, the preparation method of the sulfide solid electrolyte uses R2S, SiS2, and M... a O b After mixing in the appropriate proportions, the mixture is ground. The ground material is then mixed with an organic solvent and ball-milled to obtain a solid electrolyte precursor.

[0043] In a specific example, its chemical formula is 70Li2S—29SiS2—1Bi2O3.

[0044] In a specific example, R2S, SiS2, and M a O b The mass percentages are Li2S 54%, SiS2 41%, and Bi2O3 5%.

[0045] In a specific example, R2S, SiS2, and M a O b The mass percentages are 47% Li2S, 38% SiS2, and 15% Bi2O3.

[0046] In a specific example, R2S, SiS2, and M a O b The mass percentages are 45% Li2S, 35% SiS2, and 20% Bi2O3.

[0047] In a specific example, R2S, SiS2, and M a O b The mass percentages are 43% Li2S, 32% SiS2, and 25% Bi2O3.

[0048] The solid electrolyte precursor was heat-treated, and after cooling, a sulfide solid electrolyte was obtained. Solvent-assisted ball milling helps shorten the preparation time because the solvent alleviates the agglomeration phenomenon induced by room-temperature sintering during ball milling, thereby improving milling efficiency. The heat treatment process crystallizes the amorphous material to obtain a material with high ionic conductivity.

[0049] The sulfide solid electrolyte is pulverized.

[0050] Optionally, both ball milling and heat treatment are carried out under a protective atmosphere, which can be nitrogen or argon. The advantages of ball milling are: it can be used for dry or wet grinding; it provides good operating conditions, as the grinding process takes place in a closed system, eliminating dust and ensuring reliable operation; the grinding media are inexpensive and easy to replace; it can be operated intermittently or continuously; and when grinding explosive materials, an inert gas can be introduced into the mill instead of air.

[0051] Alternatively, the ball mill is made of cemented carbide, with a large ball diameter of 25~30mm, a small ball diameter of 5~10mm, a ball mill speed of 300~500r / min, a ball milling time of 1~2h, a large ball to small ball ratio of (1~3):1, and a ball to material ratio of (5~15):1. For example, the cemented carbide can be tungsten-cobalt cemented carbide, tungsten-titanium-cobalt cemented carbide, tungsten-tantalum-cobalt cemented carbide, or tungsten-titanium-tantalum-cobalt cemented carbide; the diameter of the large balls can be 25, 26, 27, 28, 29, 30, etc.; the diameter of the small balls can be 5, 6, 7, 8, 9, 10, etc.; the ball milling time can be 1 hour, 1.5 hours, 2 hours, etc.; the ratio of large to small balls can be 1:1, 2:1, 3:1; the ball-to-material ratio can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc.

[0052] In some embodiments of this application, the temperature change in step S2 of the heat treatment is a stepwise increase, including heat treatment at 800~900℃ for 0.5~1.5h, 900~1000℃ for 0.5~1h, and 1000~1100℃ for 0.5~1h, with the temperature rise rate between adjacent heat treatment stages being 8~12℃ / min. During the heat treatment process, the temperature of the next stage must be higher than the previous stage. Optionally, each stage of the treatment can be a constant-temperature process. If the heat treatment temperature is too high or too low, it can lead to the formation of different phases, affecting the ionic conductivity of the resulting solid electrolyte.

[0053] In one embodiment, the cooling process in step S2 is to cool to room temperature at a temperature decrease rate of 8~12°C / min.

[0054] In one embodiment, the crushing in step S3 includes multi-stage crushing until the particle size D50 of the crushed solid electrolyte is 8μm~12μm. The sulfide solid electrolyte is subjected to primary crushing, and the primary crushing equipment includes jaw crushers, cone crushers, impact crushers, hammer crushers, and roller crushers, etc.

[0055] The equipment used to pulverize sulfide solid electrolytes includes: flat air jet mills, fluidized bed air jet mills, circulating air jet mills, impact crushers, expansion crushers, ball mills, high-speed rotary projectile mills, and high-speed rotary impact mills.

[0056] This application also provides a secondary battery, which includes the sulfide solid electrolyte described in any of the above claims.

[0057] This application also provides an electrical device, wherein the driving source or energy storage source of the electrical device is the aforementioned secondary battery. For example, the electrical device can be any device that uses a secondary battery as a driving source or energy storage source, such as a mobile phone, a navigation device, a drone, or an electric vehicle.

[0058] The sulfide solid electrolyte of this application will be further described in detail below with reference to specific embodiments. In the following embodiments, R2S is Li2S, M a O b The use of Bi2O3 is understood to be limited to other embodiments, such as using Na2S for R2S and M. a O b Using Cu2O or R2S, or Li2S, M a O b SnO2, or a combination thereof, can be used.

[0059] Example 1: Preparation of 70Li2S-30SiS2 sulfide glass-ceramic solid electrolyte

[0060] 1. In an argon-dry atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), weigh 75.14 g of Li2S10 and 924.85 g of SiS2, and ball mill them in a ball mill jar to produce a ball-milled mixture.

[0061] 2. In an argon-drying atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), the ball-milled mixture is placed in a tube furnace for sintering.

[0062] Then set the sintering temperature step-up parameters: first, maintain a constant temperature of 900℃ for 1 hour, then raise the temperature to 1000℃ and maintain a constant temperature for 1 hour, then raise the temperature to 1100℃ and maintain a constant temperature for 1 hour, with a heating rate of 10℃ / min.

[0063] Sintering temperature decrease parameters: The cooling rate is 10℃ / min, and it decreases with the furnace temperature after reaching 600℃.

[0064] After sintering, the material was cooled to room temperature to obtain a glass-ceramic type sulfide solid electrolyte 70Li2S-30SiS2.

[0065] 3. The 70Li2S-30SiS2 type solid electrolyte is subjected to primary crushing using a jaw crusher, cone crusher, impact crusher, hammer crusher, or roller crusher.

[0066] 4. The 70Li2S-30SiS2 type solid electrolyte is pulverized by means of a flat air jet mill, fluidized bed air jet mill, circulating air jet mill, impact crusher, expansion crusher, ball mill, high-speed rotary projectile mill or high-speed rotary impact mill.

[0067] 5. The particle size requirement for the 70Li2S-30SiS2 type solid electrolyte after final crushing is: D50 is 10um±2um.

[0068] Example 2: Preparation of 70Li2S—29SiS2—1Bi2O3 sulfide glass-ceramic solid electrolyte

[0069] 1. In a dry argon atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), weigh 11.93 g of Li₂S₁₀, 841.47 g of SiS₂, and 146.59 g of Bi₂O₃. Ball mill in a jar with the following parameters:

[0070] Ball-to-material ratio: 10:1; Large-to-small ball ratio: 2:1; Rotation speed: 360 r / min; Time: 60 min; Output: ball-milled mixture.

[0071] 2. In an argon-drying atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), the ball-milled mixture is placed in a tube furnace for sintering.

[0072] Then set the sintering temperature step-up parameters: first, maintain a constant temperature of 900℃ for 1 hour, then raise the temperature to 1000℃ and maintain a constant temperature for 1 hour, then raise the temperature to 1100℃ and maintain a constant temperature for 1 hour, with a heating rate of 10℃ / min.

[0073] Sintering temperature decrease parameters: The cooling rate is 10℃ / min, and it decreases with the furnace temperature after reaching 600℃.

[0074] After sintering, the material was cooled to room temperature to obtain a glass-ceramic type sulfide solid electrolyte 70Li2S—29SiS2—1Bi2O3.

[0075] 3. The 70Li2S-29SiS2-1Bi2O3 type solid electrolyte is subjected to primary crushing by selecting a jaw crusher, cone crusher, impact crusher, hammer crusher or roller crusher.

[0076] 4. The 70Li2S—29SiS2—1Bi2O3 type solid electrolyte is pulverized by selecting a flat air jet mill, fluidized bed air jet mill, circulating air jet mill, impact crusher, expansion crusher, ball mill, high-speed rotary projectile mill, or high-speed rotary impact mill.

[0077] 5. The particle size requirement for the 70Li2S—29SiS2—1Bi2O3 type solid electrolyte after final crushing is: D50 is 10um±2um.

[0078] Example 3: Preparation of 70Li2S—28SiS2—2Bi2O3 sulfide glass-ceramic solid electrolyte

[0079] 1. In a dry argon atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), weigh 955.74 g of Li₂S, 767.34 g of SiS₂, and 276.90 g of Bi₂O₃, and ball mill them in a ball mill jar. The ball milling parameters are as follows:

[0080] Ball-to-material ratio: 10:1; Large-to-small ball ratio: 2:1; Rotation speed: 360 r / min; Time: 60 min; Output: ball-milled mixture.

[0081] 2. In an argon-drying atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), the ball-milled mixture is placed in a tube furnace for sintering.

[0082] Then set the sintering temperature step-up parameters: first, maintain a constant temperature of 900℃ for 1 hour, then raise the temperature to 1000℃ and maintain a constant temperature for 1 hour, then raise the temperature to 1100℃ and maintain a constant temperature for 1 hour, with a heating rate of 10℃ / min.

[0083] Sintering temperature decrease parameters: The cooling rate is 10℃ / min, and it decreases with the furnace temperature after reaching 600℃.

[0084] After sintering, the material was cooled to room temperature to obtain a glass-ceramic type sulfide solid electrolyte 70Li2S—28SiS2—2Bi2O3.

[0085] 3. The 70Li2S-28SiS2-2Bi2O3 type solid electrolyte is subjected to primary crushing by selecting a jaw crusher, cone crusher, impact crusher, hammer crusher or roller crusher.

[0086] 4. The 70Li2S-28SiS2-2Bi2O3 solid electrolyte is pulverized by means of a flat air jet mill, fluidized bed air jet mill, circulating air jet mill, impact crusher, expansion crusher, ball mill, high-speed rotary projectile mill, or high-speed rotary impact mill.

[0087] 5. The particle size requirement for the 70Li2S—28SiS2—2Bi2O3 type solid electrolyte after final crushing is: D50 is 10um±2um.

[0088] Example 4: Preparation of 70Li2S—27SiS2—3Bi2O3 sulfide glass-ceramic solid electrolyte

[0089] 1. In a dry argon atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), weigh 905.47 g of Li₂S, 701.01 g of SiS₂, and 393.51 g of Bi₂O₃, and ball mill them in a ball mill jar with the following parameters:

[0090] Ball-to-material ratio: 10:1; Large-to-small ball ratio: 2:1; Rotation speed: 360 r / min; Time: 60 min; Output: ball-milled mixture.

[0091] 2. In an argon-drying atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), the ball-milled mixture is placed in a tube furnace for sintering.

[0092] Then set the sintering temperature step-up parameters: first, maintain a constant temperature of 900℃ for 1 hour, then raise the temperature to 1000℃ and maintain a constant temperature for 1 hour, then raise the temperature to 1100℃ and maintain a constant temperature for 1 hour, with a heating rate of 10℃ / min.

[0093] Sintering temperature decrease parameters: The cooling rate is 10℃ / min, and it decreases with the furnace temperature after reaching 600℃.

[0094] After sintering, the material was cooled to room temperature to obtain a glass-ceramic type sulfide solid electrolyte 70Li2S—27SiS2—3Bi2O3.

[0095] 3. The 70Li2S-27SiS2-3Bi2O3 type solid electrolyte is subjected to primary crushing by selecting a jaw crusher, cone crusher, impact crusher, hammer crusher or roller crusher.

[0096] 4. The 70Li2S-27SiS2-3Bi2O3 type solid electrolyte is pulverized by means of a flat air jet mill, fluidized bed air jet mill, circulating air jet mill, impact crusher, expansion crusher, ball mill, high-speed rotary projectile mill, or high-speed rotary impact mill.

[0097] 5. The particle size requirement for the 70Li2S—27SiS2—3Bi2O3 type solid electrolyte after final crushing is: D50 is 10um±2um.

[0098] Example 5: Preparation of 70Li2S—26SiS2—4Bi2O3 sulfide glass-ceramic solid electrolyte

[0099] 1. In a dry argon atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), weigh 860.21 g of Li₂S, 641.31 g of SiS₂, and 498.46 g of Bi₂O₃, and ball mill them in a ball mill jar with the following parameters:

[0100] Ball-to-material ratio: 10:1; Large-to-small ball ratio: 2:1; Rotation speed: 360 r / min; Time: 60 min; Output: ball-milled mixture.

[0101] 2. In an argon-drying atmosphere (moisture content less than 1 ppm, oxygen content less than 1 ppm), the ball-milled mixture is placed in a tube furnace for sintering.

[0102] Then set the sintering temperature step-up parameters: first, maintain a constant temperature of 900℃ for 1 hour, then raise the temperature to 1000℃ and maintain a constant temperature for 1 hour, then raise the temperature to 1100℃ and maintain a constant temperature for 1 hour, with a heating rate of 10℃ / min.

[0103] Sintering temperature decrease parameters: The cooling rate is 10℃ / min, and it decreases with the furnace temperature after reaching 600℃.

[0104] After sintering, the material was cooled to room temperature to obtain a glass-ceramic type sulfide solid electrolyte 70Li2S—26SiS2—4Bi2O3.

[0105] 3. The 70Li2S-26SiS2-4Bi2O3 type solid electrolyte is subjected to primary crushing by selecting a jaw crusher, cone crusher, impact crusher, hammer crusher or roller crusher.

[0106] 4. The 70Li2S-26SiS2-4Bi2O3 solid electrolyte is pulverized by means of a flat air jet mill, fluidized bed air jet mill, circulating air jet mill, impact crusher, expansion crusher, ball mill, high-speed rotary projectile mill, or high-speed rotary impact mill.

[0107] 5. The particle size requirement for the 70Li2S—26SiS2—4Bi2O3 type solid electrolyte after final crushing is: D50 is 10um±2um.

[0108] The conductivity results for the above five embodiments are as follows:

[0109] Serial Number Example 1 (mS / cm) Example 2 (mS / cm) Example 3 (mS / cm) Example 4 (mS / cm) Example 5 (mS / cm) 1 5.13 8.61 8.93 7.41 3.12 2 5.39 8.60 8.89 7.37 3.22 3 5.07 8.39 8.95 7.39 3.14 4 5.02 8.56 8.94 7.32 3.17 5 5.10 8.59 9.05 7.42 3.10 6 5.28 8.57 9.02 7.34 3.26 7 5.11 8.78 8.91 7.47 3.02 8 5.00 8.71 8.93 7.43 2.96 9 5.10 8.61 8.72 7.28 3.23 10 5.18 8.64 9.06 7.44 3.21 average value 5.14 8.61 8.94 7.39 3.14

[0110] As can be seen from the table above, adding 1 part of Bi2O3 can improve the conductivity of the Li2S-SiS2 system, but adding 3 parts of Bi2O3 will actually decrease the conductivity of the Li2S-SiS2 system.

[0111] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0112] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a sulfide solid electrolyte, comprising the following steps: S1, R2S, SiS2 and M a O b After mixing in a preset ratio, the mixture is ground. The ground material is then mixed with an organic solvent and ball-milled to obtain a solid electrolyte precursor. S2. Heat treatment is performed on the solid electrolyte precursor, and after cooling, sulfide solid electrolyte is obtained. S3. Crush the sulfide solid electrolyte; The chemical formula of the sulfide solid electrolyte is: 70R2S-(30-x)SiS2-xM a O b Where R is Li, x is 1 to 2, and M a O b It is Bi2O3; The temperature change in the heat treatment in step S2 is a step-by-step increase. The process includes heat treatment at 800-900℃ for 0.5-1.5h, heat treatment at 900-1000℃ for 0.5-1h, and heat treatment at 1000-1100℃ for 0.5-1h. The temperature rise rate of the adjacent heat treatment stages is 8-12℃ / min.

2. The method for preparing the sulfide solid electrolyte according to claim 1, wherein the sulfide solid electrolyte has the chemical formula: 70Li2S-29SiS2-1Bi2O3.

3. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, Both the ball milling in step S1 and the heat treatment in step S2 are carried out under a protective atmosphere.

4. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, In step S1, the ball mill is made of cemented carbide, with a large ball diameter of 25-30 mm and a small ball diameter of 5-10 mm. The ball mill speed is 300-500 r / min, the ball milling time is 1-2 h, the ratio of large to small balls is (1-3):1, and the ball-to-material ratio is (5-15):

1.

5. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, The cooling process in step S2 involves cooling the room to room temperature at a rate of 8–12 °C / min.

6. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, The pulverization in step S3 includes multi-stage pulverization until the particle size D50 of the pulverized solid electrolyte is 8μm to 12μm.

7. A secondary battery, characterized in that, The secondary battery includes a sulfide solid electrolyte prepared by the method described in any one of claims 1 to 6.

8. An electrical device, characterized in that, The driving source or energy storage source of the electrical device is the secondary battery as described in claim 7.

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