Preparation method of plasma-assisted gradient doped sulfide solid electrolyte

Abstract

The invention discloses a preparation method and application of a plasma-assisted gradient doped sulfide solid electrolyte, and belongs to the technical field of preparation of solid-state battery materials. According to the method, four-order synergistic processes of plasma activation, gradient doping, microwave sintering and supercritical purification are combined, atomic-scale mixing is achieved through plasma-assisted ball milling, a gradient Cl doping process is combined to optimize a crystal structure, energy consumption is reduced by 70% through microwave sintering, and the product purity is improved to 99.5% by adopting a supercritical carbon dioxide purification technology. The corollary equipment integrates a corrosion-resistant ball milling bin, a high-precision microwave module and an online detection system, and is suitable for large-scale production, the ionic conductivity reaches 6.4 mS / cm, the cycle performance is improved by 150%, the continuous production process only needs 3 h, and compared with the traditional process which needs more than 12 h, the efficiency is improved by 400%.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state battery material preparation, and specifically relates to a preparation method and application of a plasma-assisted-gradient-doped sulfide solid electrolyte. Background Art

[0002] With the development of lithium-ion battery technology, solid-state electrolytes have become a research hotspot due to their advantages such as high safety and high energy density. Sulfide solid electrolytes have high ionic conductivity, but the traditional solid-phase method requires high-temperature sintering (1200℃ / 6h-12h), which has high energy consumption; uneven Cl doping (conductivity ≤3mS / cm), resulting in interface defects; a large amount of impurity residues (≥5%), low product purity; and an unsatisfactory crystal structure. These problems have led to limited ionic conductivity and cycle performance, making it difficult to meet the needs of large-scale production. For example, conventional ball milling methods cannot achieve atomic-level mixing, traditional sintering processes consume a lot of energy, and impurity removal is not thorough, which seriously restricts the industrial application of sulfide solid electrolytes.

[0003] Although the existing patent CN202111554284.5 optimizes the phosphoric acid production process, it does not solve the uniformity and energy consumption problems of the sulfide solid electrolyte. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte. In this method, a four-stage synergistic process of plasma activation + gradient doping + microwave sintering + supercritical purification is combined to solve the problems of high energy consumption, insufficient mixing, poor crystal structure, low purity, etc. in the prior art, improve the ionic conductivity and cycle performance of the sulfide solid electrolyte, and realize large-scale production.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte comprises the following steps:

[0007] S1, plasma-assisted ball milling:

[0008] After mixing lithium sulfide, phosphorus sulfide and lithium chloride in corresponding molar ratios, the mixture is placed in a plasma-excited high-energy ball mill under inert gas protection for mechanical ball milling to obtain atomic-grade powder;

[0009] S2, gradient concentration doping:

[0010] doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture to obtain a gradient chloride powder;

[0011] S3. Microwave sintering and purification:

[0012] After microwave sintering the gradient chloride powder, it is purified using supercritical carbon dioxide to obtain a finished sulfide solid electrolyte.

[0013] The finished product is Li 7-x PS 6-x Cl x .

[0014] Preferably, the molar ratio of lithium sulfide, phosphorus sulfide and lithium chloride is (7-x):6-x:x, wherein x=0.5-1.3.

[0015] Preferably, the inert gas is obtained by mixing argon and nitrogen in a mass ratio of 1:3.

[0016] Preferably, the frequency of the plasma-excited high-energy ball milling device is 2.45±0.05 GHz, and the power density is 0.8-1.2 W / cm 3 ;

[0017] The side wall of the ink tank of the high-energy ball milling device is provided with an annularly distributed electrode array, the spacing between the electrode arrays is 10 to 20 mm, and the surface of the electrode array is coated with a composite coating;

[0018] The composite coating is composed of aluminum oxide and yttrium oxide in a mass fraction ratio of 20-75wt%:25-80wt%; the thickness of the composite coating is 45-55μm;

[0019] The mechanical ball milling treatment lasts for 2 to 4 hours;

[0020] The ball-to-material ratio is 10:1.

[0021] Preferably, zirconium dioxide ceramic balls are used in the high-energy ball milling device;

[0022] The zirconium dioxide ceramic ball is composed of ball A, ball B and ball C in a mass fraction ratio of 60%:30%:10%;

[0023] The particle size of the pellet A is 3-5 mm, the particle size of the pellet B is 5-8 mm, and the particle size of the pellet C is 8-10 mm.

[0024] Preferably, the specific process of doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture uniformly is as follows: doping lithium chloride into the atomic-grade powder in 3 to 5 times, with the amount of lithium chloride added being 20 to 30 wt% of the total amount of lithium chloride per time;

[0025] The gradient interval duration is 30 to 60 minutes.

[0026] Preferably, the microwave sintering process is: microwave sintering at 300-350° C. for 30-60 min, with a heating rate of ≥50° C. / min.

[0027] As a preferred method, the process of supercritical carbon dioxide purification is as follows: at a pressure of 8-12 MPa, 35-45°C, and a carbon dioxide flow rate of 0.5-1.2 m 3 / h, the treatment time is 1 to 2 hours, and unreacted impurities are removed.

[0028] Preferably, the main phase purity of the finished sulfide solid electrolyte product is ≥99.5%, and the residual lithium chloride content is ≤0.3wt%.

[0029] The invention discloses an application of a plasma-assisted gradient-doped sulfide solid electrolyte in the preparation of an all-solid-state battery. The plasma-assisted gradient-doped sulfide solid electrolyte is obtained by a preparation method.

[0030] Compared with the prior art, the present invention has at least the following technical effects:

[0031] (1) The present invention provides a method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte. This method combines a four-stage synergistic process of plasma activation + gradient doping + microwave sintering + supercritical purification to solve the problems of high energy consumption, insufficient mixing, poor crystal structure, and low purity in the prior art, thereby improving the ionic conductivity and cycle performance of the sulfide solid electrolyte and realizing large-scale production.

[0032] (2) In this method, the raw materials of the sulfide solid electrolyte are placed in a corrosion-resistant ball mill chamber and plasma is introduced. The high energy activity of the plasma activates the surface of the material, reduces the reaction activation energy, and achieves atomic-level mixing of the raw materials during the ball milling process. After the ball milling efficiency is improved by 300%, the ball milling time is also shortened to 3 hours. At the same time, zirconium dioxide ceramic balls with mixed particle sizes are specially selected. Not only can the grinding efficiency and energy consumption be balanced, but the powder uniformity is improved by 15% after the optimization ratio. In addition, the introduction of plasma can break the chemical bonds on the surface of the raw material particles, promote the diffusion and mixing between atoms, make the raw materials more uniform, and lay the foundation for the subsequent formation of a good crystal structure.

[0033] (3) A gradient Cl doping process was employed, controlling the C doping level x within a range of 0.5 to 1.3. Through precise control of the doping process, the crystal structure of the sulfide solid electrolyte was optimized. Different Cl doping levels have varying effects on the crystal structure. The appropriate doping level can improve lattice defects and enhance the smoothness of ion migration channels, thereby increasing ionic conductivity to 6.4 mS / cm with a standard deviation of <0.05%, achieving superior uniformity compared to conventional processes.

[0034] (4) Microwave sintering technology is used to control the sintering temperature at 300-350°C, reducing energy consumption by 70% compared to traditional sintering processes. Microwave sintering utilizes the interaction between microwaves and materials to generate heat within the material, achieving rapid and uniform heating. This not only saves energy but also reduces the adverse effects of high temperatures on material properties.

[0035] (5) Supercritical carbon dioxide purification technology is used to remove impurities from the product, utilizing its excellent solubility and diffusion properties, raising the product purity to 99.5%. This high-purity product can reduce the impurities that hinder ion transport, further improving ionic conductivity and cycle performance.

[0036] (6) The continuous production process of this method only takes 3 hours, which is 400% more efficient than the traditional process which takes more than 12 hours. DETAILED DESCRIPTION

[0037] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without indicating the manufacturer are conventional products that can be purchased commercially.

[0038] The technical solution of a specific embodiment of the present invention is:

[0039] A method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte comprises the following steps:

[0040] S1, plasma-assisted ball milling:

[0041] After mixing lithium sulfide, phosphorus sulfide and lithium chloride in corresponding molar ratios, the mixture is placed in a plasma-excited high-energy ball mill under inert gas protection for mechanical ball milling to obtain atomic-grade powder;

[0042] S2, gradient concentration doping:

[0043] doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture to obtain a gradient chloride powder;

[0044] S3. Microwave sintering and purification:

[0045] After microwave sintering the gradient chloride powder, it is purified using supercritical carbon dioxide to obtain a finished sulfide solid electrolyte.

[0046] The finished product is Li 7-x PS 6-x Cl x .

[0047] The molar ratio of the lithium sulfide, phosphorus sulfide and lithium chloride is (7-x):6-x:x, wherein x=0.5-1.3.

[0048] The inert gas is obtained by mixing argon and nitrogen in a mass ratio of 1:3.

[0049] The frequency of the plasma-excited high-energy ball milling device is 2.45±0.05 GHz, and the power density is 0.8-1.2 W / cm 3 ;

[0050] The side wall of the ink tank of the high-energy ball milling device is provided with an annularly distributed electrode array, the spacing between the electrode arrays is 10 to 20 mm, and the surface of the electrode array is coated with a composite coating;

[0051] The composite coating is composed of aluminum oxide and yttrium oxide in a mass fraction ratio of 20-75wt%:25-80wt%; the thickness of the composite coating is 45-55μm;

[0052] The mechanical ball milling treatment lasts for 2 to 4 hours;

[0053] The ball-to-material ratio is 10:1.

[0054] Zirconium dioxide ceramic balls are used in the high-energy ball mill;

[0055] The zirconium dioxide ceramic ball is composed of ball A, ball B and ball C in a mass fraction ratio of 60%:30%:10%;

[0056] The particle size of the pellet A is 3-5 mm, the particle size of the pellet B is 5-8 mm, and the particle size of the pellet C is 8-10 mm.

[0057] The specific process of doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture uniformly is as follows: doping lithium chloride into the atomic-grade powder in 3 to 5 times, wherein the amount of lithium chloride added per time is 20 to 30 wt% of the total amount of lithium chloride;

[0058] The gradient interval duration is 30 to 60 minutes.

[0059] The microwave sintering process is as follows: microwave sintering at 300-350° C. for 30-60 minutes, with a heating rate of ≥50° C. / min.

[0060] The process of supercritical carbon dioxide purification is as follows: at a pressure of 8-12 MPa, 35-45°C, and a carbon dioxide flow rate of 0.5-1.2 m 3 / h, the treatment time is 1 to 2 hours, and unreacted impurities are removed.

[0061] The main phase purity of the finished sulfide solid electrolyte product is ≥99.5%, and the residual lithium chloride content is ≤0.3 wt%.

[0062] The invention discloses an application of a plasma-assisted gradient-doped sulfide solid electrolyte in the preparation of an all-solid-state battery. The plasma-assisted gradient-doped sulfide solid electrolyte is obtained by a preparation method.

[0063] Example 1:

[0064] A method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte comprises the following steps:

[0065] S1, plasma-assisted ball milling:

[0066] After mixing lithium sulfide, phosphorus sulfide and lithium chloride in corresponding molar ratios, the mixture is placed in a plasma-excited high-energy ball mill under inert gas protection for mechanical ball milling to obtain atomic-grade powder;

[0067] S2, gradient concentration doping:

[0068] doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture to obtain a gradient chloride powder;

[0069] S3. Microwave sintering and purification:

[0070] After microwave sintering the gradient chloride powder, it is purified using supercritical carbon dioxide to obtain a finished sulfide solid electrolyte.

[0071] The finished product is Li 7-x PS 6-x Cl x .

[0072] The molar ratio of the lithium sulfide, phosphorus sulfide and lithium chloride is (7-x):6-x:x, wherein x=1.3.

[0073] That is, the raw material ratio is: Li2S 5.7mol, P2S51mol, LiCl 1.3mol.

[0074] The inert gas is obtained by mixing argon and nitrogen in a mass ratio of 1:3.

[0075] The plasma-excited high-energy ball milling device has a frequency of 2.45 GHz and a power density of 1.2 W / cm 3 ;

[0076] The side wall of the ink tank of the high-energy ball milling device is provided with an annularly distributed electrode array, the electrode array spacing is 20 mm, and the surface of the electrode array is coated with a composite coating;

[0077] The composite coating is composed of aluminum oxide and yttrium oxide in a mass fraction ratio of 20wt% to 80wt%;

[0078] The thickness of the composite coating is 45 μm;

[0079] The mechanical ball milling treatment lasts for 3 hours;

[0080] The ball-to-material ratio is 10:1.

[0081] Zirconium dioxide ceramic balls are used in the high-energy ball mill;

[0082] The zirconium dioxide ceramic ball is composed of ball A, ball B and ball C in a mass fraction ratio of 60%:30%:10%;

[0083] The particle size of the pellet A is 3-5 mm, the particle size of the pellet B is 5-8 mm, and the particle size of the pellet C is 8-10 mm.

[0084] The specific process of doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture uniformly is as follows: doping lithium chloride into the atomic-grade powder in 5 times, with the amount of lithium chloride added in each time being 20 wt% of the total amount of lithium chloride;

[0085] The gradient interval duration was 45 min.

[0086] The microwave sintering process is as follows: microwave sintering at 320° C. for 40 min, with a heating rate of 55° C. / min.

[0087] The process of supercritical carbon dioxide purification is as follows: at a pressure of 10 MPa, 40°C, and a carbon dioxide flow rate of 0.8 m 3 / h, the treatment time is 1h, and unreacted impurities are removed.

[0088] The main phase purity of the finished sulfide solid electrolyte is 99.6%, the residual lithium chloride content is 0.2 wt%, the ion conductivity is 6.4 mS / cm, and the capacity retention rate after 2000 cycles is 91.2%.

[0089] Example 2:

[0090] A method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte comprises the following steps:

[0091] S1, plasma-assisted ball milling:

[0092] After mixing lithium sulfide, phosphorus sulfide and lithium chloride in corresponding molar ratios, the mixture is placed in a plasma-excited high-energy ball mill under inert gas protection for mechanical ball milling to obtain atomic-grade powder;

[0093] S2, gradient concentration doping:

[0094] doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture to obtain a gradient chloride powder;

[0095] S3. Microwave sintering and purification:

[0096] After microwave sintering the gradient chloride powder, it is purified using supercritical carbon dioxide to obtain a finished sulfide solid electrolyte.

[0097] The finished product is Li 7-x PS 6-x Cl x .

[0098] The molar ratio of the lithium sulfide, phosphorus sulfide and lithium chloride is (7-x):6-x:x, wherein x=0.5.

[0099] That is, the raw material ratio is: Li2S 5.7mol, P2S51mol, LiCl 1.3mol.

[0100] The inert gas is obtained by mixing argon and nitrogen in a mass ratio of 1:3.

[0101] The plasma-excited high-energy ball milling device has a frequency of 2.45 GHz and a power density of 1.2 W / cm 3 ;

[0102] The side wall of the ink tank of the high-energy ball milling device is provided with an annularly distributed electrode array, the electrode array spacing is 20 mm, and the surface of the electrode array is coated with a composite coating;

[0103] The composite coating is composed of aluminum oxide and yttrium oxide; the mass fraction ratio is 75wt%:25wt%;

[0104] The thickness of the composite coating is 45 μm;

[0105] The mechanical ball milling treatment lasts for 3 hours;

[0106] The ball-to-material ratio is 10:1.

[0107] Zirconium dioxide ceramic balls are used in the high-energy ball mill;

[0108] The zirconium dioxide ceramic ball is composed of ball A, ball B and ball C in a mass fraction ratio of 60%:30%:10%;

[0109] The particle size of the pellet A is 3-5 mm, the particle size of the pellet B is 5-8 mm, and the particle size of the pellet C is 8-10 mm.

[0110] The specific process of doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture uniformly is as follows: doping lithium chloride into the atomic-grade powder in 5 times, with the amount of lithium chloride added in each time being 20 wt% of the total amount of lithium chloride;

[0111] The gradient interval duration was 45 min.

[0112] The microwave sintering process is as follows: microwave sintering at 320° C. for 40 min, with a heating rate of 55° C. / min.

[0113] The process of supercritical carbon dioxide purification is as follows: at a pressure of 10 MPa, 40°C, and a carbon dioxide flow rate of 0.8 m 3 / h, the treatment time is 1h, and unreacted impurities are removed.

[0114] The main phase purity of the finished sulfide solid electrolyte is 99%, the residual lithium chloride content is less than 0.5wt%, the ion conductivity is 5mS / cm, and the capacity retention rate after 2000 cycles is 85%.

[0115] Example 3:

[0116] A method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte comprises the following steps:

[0117] S1, plasma-assisted ball milling:

[0118] After mixing lithium sulfide, phosphorus sulfide and lithium chloride in corresponding molar ratios, the mixture is placed in a plasma-excited high-energy ball mill under inert gas protection for mechanical ball milling to obtain atomic-grade powder;

[0119] S2, gradient concentration doping:

[0120] doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture to obtain a gradient chloride powder;

[0121] S3. Microwave sintering and purification:

[0122] After microwave sintering the gradient chloride powder, it is purified using supercritical carbon dioxide to obtain a finished sulfide solid electrolyte.

[0123] The finished product is Li 7-x PS 6-x Cl x .

[0124] The molar ratio of the lithium sulfide, phosphorus sulfide and lithium chloride is (7-x):6-x:x, wherein x=1.

[0125] That is, the raw material ratio is: Li2S 5.7mol, P2S51mol, LiCl 1.3mol.

[0126] The inert gas is obtained by mixing argon and nitrogen in a mass ratio of 1:3.

[0127] The plasma-excited high-energy ball milling device has a frequency of 2.45 GHz and a power density of 1.2 W / cm 3 ;

[0128] The side wall of the ink tank of the high-energy ball milling device is provided with an annularly distributed electrode array, the electrode array spacing is 20 mm, and the surface of the electrode array is coated with a composite coating;

[0129] The composite coating is composed of aluminum oxide and yttrium oxide;

[0130] The thickness of the composite coating is 45 μm;

[0131] The mechanical ball milling treatment lasts for 3 hours;

[0132] The ball-to-material ratio is 10:1.

[0133] Zirconium dioxide ceramic balls are used in the high-energy ball mill;

[0134] The zirconium dioxide ceramic ball is composed of ball A, ball B and ball C in a mass fraction ratio of 60%:30%:10%;

[0135] The particle size of the pellet A is 3-5 mm, the particle size of the pellet B is 5-8 mm, and the particle size of the pellet C is 8-10 mm.

[0136] The specific process of doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture uniformly is as follows: doping lithium chloride into the atomic-grade powder in 5 times, with the amount of lithium chloride added in each time being 20 wt% of the total amount of lithium chloride;

[0137] The gradient interval duration was 45 min.

[0138] The microwave sintering process is as follows: microwave sintering at 320° C. for 40 min, with a heating rate of 55° C. / min.

[0139] The process of supercritical carbon dioxide purification is as follows: at a pressure of 10 MPa, 40°C, and a carbon dioxide flow rate of 0.8 m 3 / h, the treatment time is 1h, and unreacted impurities are removed.

[0140] The main phase purity of the finished sulfide solid electrolyte is 98%, the residual lithium chloride content is 0.3 wt%, the ion conductivity is 5 mS / cm, and the capacity retention rate after 2000 cycles is 85%.

[0141] Comparative Example: Based on the above Example 1, other process parameters were kept unchanged, and only the particle size distribution of ZrO2 ceramic balls was changed to test its effect on product purity:

[0142]

[0143] in conclusion:

[0144] 1. The mixed particle size distribution (Example 1) has significant advantages: purity is increased to 99.6% (98.2% in the blank control group) because small particle size balls (3-5 mm) enhance surface activation and large particle size balls (8-10 mm) reduce lattice defects caused by over-grinding; Cl doping uniformity (standard deviation 0.05%) is improved by 60% compared with the single particle size group (0.08-0.15%); ionic conductivity reaches 6.4 mS / cm, demonstrating the necessity of the particle size range (3-10 mm).

[0145] 2. From the above table, it can be seen that if the particle size exceeds the range of 3 to 10 mm (such as 10 mm in Comparative Example 2), the product purity and conductivity will decrease significantly due to insufficient impact force.

[0146] The mixing ratio (60% small particle size) is the optimized value, and the purity drops to <99.3% when the ratio deviation is >10%.

[0147] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte, characterized in that: The steps include: S1, plasma-assisted ball milling: After mixing lithium sulfide, phosphorus sulfide and lithium chloride in corresponding molar ratios, the mixture is placed in a plasma-excited high-energy ball mill under inert gas protection for mechanical ball milling to obtain atomic-grade powder; S2, gradient concentration doping: doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture to obtain a gradient chloride powder; S3. Microwave sintering and purification: After microwave sintering the gradient chloride powder, it is purified using supercritical carbon dioxide to obtain a finished sulfide solid electrolyte. The finished product is Li 7-x PS 6-x Cl x .

2. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The molar ratio of the lithium sulfide, phosphorus sulfide and lithium chloride is (7-x):6-x:x, wherein x=0.5-1.

3.

3. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The inert gas is obtained by mixing argon and nitrogen in a mass ratio of 1:

3.

4. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The frequency of the plasma-excited high-energy ball milling device is 2.45±0.05 GHz, and the power density is 0.8-1.2 W / cm 3 ; The side wall of the ink tank of the high-energy ball milling device is provided with an annularly distributed electrode array, the spacing between the electrode arrays is 10 to 20 mm, and the surface of the electrode array is coated with a composite coating; The composite coating is composed of aluminum oxide and yttrium oxide in a mass fraction ratio of 20-75wt%:25-80wt%; the thickness of the composite coating is 45-55μm; The mechanical ball milling treatment lasts for 2 to 4 hours; The ball-to-material ratio is 10:

1.

5. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: Zirconium dioxide ceramic balls are used in the high-energy ball mill; The zirconium dioxide ceramic ball is composed of ball A, ball B and ball C in a mass fraction ratio of 60%:30%:10%; The particle size of the pellet A is 3-5 mm, the particle size of the pellet B is 5-8 mm, and the particle size of the pellet C is 8-10 mm.

6. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The specific process of doping lithium chloride into the atomic-grade powder in a gradient manner and mixing the mixture uniformly is as follows: doping lithium chloride into the atomic-grade powder in 3 to 5 times, wherein the amount of lithium chloride added per time is 20 to 30 wt% of the total amount of lithium chloride; The gradient interval duration is 30 to 60 minutes.

7. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The microwave sintering process is as follows: microwave sintering at 300-350° C. for 30-60 minutes, with a heating rate of ≥50° C. / min.

8. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The process of supercritical carbon dioxide purification is as follows: at a pressure of 8-12 MPa, 35-45°C, and a carbon dioxide flow rate of 0.5-1.2 m 3 / h, the treatment time is 1 to 2 hours, and unreacted impurities are removed.

9. The method for preparing a plasma-assisted gradient-doped sulfide solid electrolyte according to claim 1, characterized in that: The main phase purity of the finished sulfide solid electrolyte product is ≥99.5%, and the residual lithium chloride content is ≤0.3 wt%.

10. Application of a plasma-assisted gradient-doped sulfide solid electrolyte in the preparation of an all-solid-state battery, characterized in that: The plasma-assisted-gradient-doped sulfide solid electrolyte is obtained by the preparation method according to any one of claims 1 to 9.

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