Sulfide solid electrolyte and method for preparing the same

Abstract

The application provides a sulfide solid electrolyte and a preparation method thereof, and particularly relates to the technical field of secondary batteries. The sulfide solid electrolyte is a lithium phosphorus oxysulfide, and the chemical formula of the lithium phosphorus oxysulfide is Li7P3S 7.5+x‑5y O 3.5‑x+5y ; wherein, 0<=x<=3.5, 0<=y<=1.5, -7.5

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a sulfide solid electrolyte and a preparation method thereof. Background Art

[0002] Since the commercialization of lithium-ion batteries, the energy density of liquid lithium-ion batteries has gradually approached its theoretical limit. Consequently, solid-state batteries, offering high safety and energy density, have attracted widespread attention. Among the various solid-state battery technologies, sulfide solid electrolytes are considered to have great development potential due to their ultra-high ionic conductivity and excellent thermal stability, comparable to liquid electrolytes.

[0003] While existing pure sulfide solid electrolytes are renowned for their high conductivity, their extreme air sensitivity necessitates that the entire synthesis, storage, and battery assembly process be performed under an inert atmosphere (e.g., an Ar glove box) or an ultra-dry environment (dew point < -50°C), significantly increasing process complexity and operational difficulties. Furthermore, even brief exposure to air can trigger irreversible hydrolysis reactions (e.g., to form H₂S and LiOH), severely restricting their scalable production and practical application.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a sulfide solid electrolyte, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0006] A second object of the present invention is to provide a method for preparing a sulfide solid electrolyte.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0008] The first aspect of the present invention provides a sulfide solid electrolyte, wherein the sulfide solid electrolyte is lithium phosphorus sulfur oxide, and the chemical formula of the lithium phosphorus sulfur oxide is Li7P3S 7.5+x-5y O 3.5-x+5y ;

[0009] Among them, 0≤x≤3.5, 0≤y≤1.5, -7.5 <x-5y<3.5。

[0010] The lithium phosphorus sulfur oxide is a sulfur-oxygen mixed coordination structure, wherein x is the molar amount of lithium sulfide in the raw material, and y is the molar amount of phosphorus pentoxide in the raw material. The S / O ratio is optimized by adjusting x and y together.

[0011] Furthermore, the Li7P3S 7.5+x-5y O 3.5-x+5y In, 1≤x≤3.5, y=0.

[0012] The raw materials for preparing the lithium phosphorus sulfide oxide do not contain phosphorus pentoxide.

[0013] The second aspect of the present invention provides a method for preparing the sulfide solid electrolyte, comprising mixing lithium oxide, lithium sulfide, phosphorus pentasulfide, and phosphorus pentoxide, ball milling the mixture, and then heat treating the mixture to obtain the sulfide solid electrolyte; wherein the ball milling speed is 1000-2000 rpm; the ball milling beads used in the ball milling have a radius of 0.4-0.7 cm and a density of 5.6-15.6 g / cm 3 .

[0014] Furthermore, the bead-to-material ratio of the ball mill is 7-12:1; the ball mill beads include zirconia beads, stainless steel beads and tungsten carbide beads.

[0015] Furthermore, the ball milling is carried out in a ball mill jar, and the height-to-diameter ratio of the ball mill jar is 1.2-1.4.

[0016] Furthermore, during the ball milling process, the total volume of the ball milling beads and the material does not exceed 70% of the volume of the ball milling jar, and the total ball milling energy is ≥455mJ.

[0017] Furthermore, the ball milling time is 1 to 30 hours.

[0018] Furthermore, the moisture content of the ball milling environment is less than 0.01 ppm, and the oxygen content is less than 1 ppm.

[0019] Furthermore, the heat treatment process is: in an inert atmosphere, the temperature is increased from room temperature to 250-300° C. at a heating rate of 1-5° C. / min, and kept at this temperature for 1-3 hours.

[0020] Furthermore, the molar ratio of the lithium oxide, the lithium sulfide, the phosphorus pentasulfide and the phosphorus pentoxide is (3.5-x):x:(1.5-y):y; wherein 0≤x≤3.5, 0≤y≤1.5, -7.5 <x-5y<3.5。

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] The sulfide solid electrolyte provided by this invention, specifically lithium phosphorus oxysulfide, partially replaces sulfur with oxygen, significantly improving air stability and electrochemical window while maintaining high ionic conductivity. This represents a significant breakthrough towards the practical application of sulfur-based solid electrolytes. With an ionic conductivity of up to 1 mS / cm, lithium phosphorus oxysulfide helps improve battery charge and discharge efficiency and performance, ensuring safety and long-term stability.

[0023] The preparation process provided by the present invention utilizes high-energy ball milling to achieve particle refinement while thoroughly mixing the raw materials, helping to shorten the ion transport path. The heat treatment step performed after ball milling allows the mixed materials to fully react, ultimately forming the desired sulfide solid electrolyte. This preparation method not only improves the efficiency of solid-state electrolyte preparation but also helps to obtain electrolyte materials with uniform performance and a dense structure, thus providing reliable performance guarantees for all-solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Li7P3S 8.5 O 2.5 Relationship curve between ionic conductivity and ball milling energy. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0028] The first aspect of the present invention provides a sulfide solid electrolyte, wherein the sulfide solid electrolyte is lithium phosphorus sulfur oxide, and the chemical formula of the lithium phosphorus sulfur oxide is Li7P3S 7.5+x-5y O 3.5-x+5y ;

[0029] Among them, 0≤x≤3.5, 0≤y≤1.5, -7.5 <x-5y<3.5。

[0030] The lithium phosphorus sulfur oxide is a sulfur-oxygen mixed coordination structure, wherein x is the molar amount of lithium sulfide in the raw material, and y is the molar amount of phosphorus pentoxide in the raw material. The S / O ratio is optimized by adjusting x and y together.

[0031] The sulfide solid electrolyte provided by this invention, specifically lithium phosphorus oxysulfide, partially replaces sulfur with oxygen, significantly improving air stability and electrochemical window while maintaining high ionic conductivity. This represents a significant breakthrough towards the practical application of sulfur-based solid electrolytes. With an ionic conductivity of up to 1 mS / cm, lithium phosphorus oxysulfide helps improve battery charge and discharge efficiency and performance, ensuring safety and long-term stability.

[0032] In a specific implementation process, the chemical formula of the lithium phosphorus sulfur oxide can be, for example, Li7P3S 1.25 O 9.75 、Li7P3S 3.5 O 7.5 、Li7P3S 3.75 O 7.25 、Li7P3S 6.25 O 4.75 、Li7P3S 7.5 O 3.5 、Li7P3S 8.5 O 2.5 、Li7P3S 9.5 O 1.5 、Li7P3S 10.5 O 0.5 , using oxygen to partially replace sulfur can improve the stability of lithium phosphorus sulfur oxide.

[0033] Furthermore, the Li7P3S 7.5+x-5y O 3.5-x+5y , 1≤x≤3.5, y=0. The raw materials for preparing the lithium phosphorus oxysulfide do not contain phosphorus pentoxide.

[0034] In a specific implementation process, the chemical formula of the lithium phosphorus sulfur oxide can be, for example, Li7P3S 8.5 O 2.5 、Li7P3S 9.5 O 1.5 、Li7P3S 10.5 O 0.5 , the most preferred is Li7P3S 8.5 O 2.5 .

[0035] The second aspect of the present invention provides a method for preparing the sulfide solid electrolyte, comprising mixing lithium oxide, lithium sulfide, phosphorus pentasulfide, and phosphorus pentoxide, ball milling the mixture, and then heat treating the mixture to obtain the sulfide solid electrolyte; wherein the ball milling speed is 1000-2000 rpm; the ball milling beads used in the ball milling have a radius of 0.4-0.7 cm and a density of 5.6-15.6 g / cm 3 .

[0036] The preparation process provided by the present invention utilizes high-energy ball milling to achieve particle refinement while thoroughly mixing the raw materials. This helps shorten the ion transport path and reduce grain boundary resistance. The heat treatment step performed after ball milling allows the mixed materials to fully react, ultimately forming the desired sulfide solid electrolyte. This preparation method not only improves the efficiency of solid-state electrolyte preparation but also helps obtain electrolyte materials with uniform performance and a dense structure, thus providing reliable performance guarantees for all-solid-state batteries.

[0037] High-energy ball milling technology at 1000-2000rpm can significantly improve the grinding efficiency and microscopic uniformity of material preparation. This speed range uses high-intensity centrifugal force to drive the ball mill to high-speed collision, with a linear speed of up to 20m / s, allowing samples to be quickly and evenly ground in a short period of time, thereby improving research efficiency. This speed range of the high-energy ball mill, through the combination of friction and collision forces, enables ultra-fine grinding of materials. In addition, during the high-energy ball milling process, the sample is subjected to uniform collision and friction, which helps to improve the uniformity and stability of the sample.

[0038] Typically but not limitatively, the rotation speed of the ball mill can be, for example, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm or 2000 rpm, or any value within the range of 1000 rpm to 2000 rpm.

[0039] Typically, but not limiting, the radius of the ball milling beads may be, for example, 0.4 cm, 0.5 cm, 0.6 cm or 0.7 cm, or any value within the range of 0.4 to 0.7 cm.

[0040] Furthermore, the bead-to-material ratio of the ball mill is 7 to 12:1; the ball mill beads include zirconia beads, stainless steel beads, and tungsten carbide beads. The ball mill jars are made of materials that match the ball mill beads, including zirconia jars, stainless steel jars, and tungsten carbide jars. Zirconia beads have high density and wear resistance, achieving faster grinding efficiency and finer particle size during the grinding process. They do not react with the ground material, ensuring high product quality and purity. The high-strength metal matrix of the stainless steel beads provides deformation resistance. Tungsten carbide beads have an ultra-hard carbide lattice structure, which reduces impurity release.

[0041] Using this ball-to-material ratio during the preparation of solid electrolytes can effectively improve grinding efficiency and quality, reduce energy consumption, and extend the service life of the ball mill. This ratio helps achieve uniform mixing of materials and optimizes their microstructure, thereby improving the electrochemical properties of the materials, especially ionic conductivity. Typical, but non-limiting, ball-to-material ratios can be 7.0:1, 7.5:1, 8.0:1, 8.5:1, 9.0:1, 9.5:1, 10.0:1, 10.5:1, 11:1, 11.5:1, or 12:1, or any value within the range of 7:1 to 12:1.

[0042] Furthermore, the ball milling is performed in a ball mill having a height-to-diameter ratio of 1.2 to 1.4. Typically, but not limiting, the height-to-diameter ratio of the ball mill can be, for example, 1.2, 1.25, 1.3, 1.35, or 1.4, or any value within the range of 1.2 to 1.4.

[0043] Furthermore, during the ball milling process, the combined volume of the milling beads and the material does not exceed 70% of the milling jar volume, and the total milling energy is ≥455 mJ. This high-energy milling method achieves thorough mixing and refinement of the raw materials while avoiding overheating or structural damage that could occur at excessively high speeds. The post-milling heat treatment step allows the mixed materials to fully react, ultimately forming the desired solid electrolyte.

[0044] During the ball milling process, different ball milling energies are achieved by adjusting the particle size of the ball milling beads, the bead-to-material ratio, and the rotation speed. When the total ball milling energy is ≥455mJ, the ionic conductivity of the obtained solid electrolyte is greater than 0.1mS / cm.

[0045] The ball milling energy is calculated as follows: According to the kinetic energy theorem, the kinetic energy E (mJ) of each ball milling bead is related to its mass m (g) and speed V (m / s): E 单 = (1 / 2) mV 2 ; where m is the mass of a single ball milling bead, which is related to the radius r (cm) and density ρ (g / cm 3 ), m=(4 / 3)πr 3 ρ; where V is the linear velocity, which is related to the radius of the ball mill R (cm) and the ball mill speed n (r / min): V = 2πRn / 60, so the total kinetic energy of ball milling E can be obtained. 总 =aE=(1 / 2)a×(4 / 3πr 3 ρ)×[2π(Rr)ω / 60] 2 , a is the total number of ball milling beads.

[0046] Furthermore, the ball milling time is 1 to 30 hours.

[0047] Furthermore, the ball milling environment has a moisture content of less than 0.01 ppm and an oxygen content of less than 1 ppm. Such limitations prevent oxidation and hydrolysis of the material during the grinding process, avoid unnecessary chemical reactions, reduce agglomeration and overheating, improve grinding efficiency, and ensure a uniform and fine powder. Furthermore, it helps stabilize the grinding process, control temperature, and avoid thermal runaway, thereby protecting the chemical stability of the material and ensuring the high quality and consistency of the final product.

[0048] Furthermore, the heat treatment process is: in an inert atmosphere, the temperature is increased from room temperature to 250-300° C. at a heating rate of 1-5° C. / min, and kept at this temperature for 1-3 hours.

[0049] Typically, but not limiting, the heat treatment process is to increase the temperature from room temperature to 250°C, 260°C, 270°C, 280°C, 290°C or 300°C in an inert atmosphere, for example, at a heating rate of 1°C / min, 2°C / min, 3°C / min, 4°C / min or 5°C / min, and keep it at that temperature for 1 hour, 2 hours or 3 hours.

[0050] Furthermore, the molar ratio of the lithium oxide, the lithium sulfide, the phosphorus pentasulfide and the phosphorus pentoxide is (3.5-x):x:(1.5-y):y; wherein 0≤x≤3.5, 0≤y≤1.5, -7.5 <x-5y<3.5。

[0051] The present invention is further illustrated below by specific examples and comparative examples. However, it should be understood that these examples are merely for the purpose of further explanation and should not be construed as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, unless otherwise specified, were prepared under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0052] The ball mill used in the following examples and comparative examples was made of stainless steel, had a volume of 65 mL, and a height-to-diameter ratio of 1.25.

[0053] Example 1

[0054] This embodiment provides a sulfide solid electrolyte, and the preparation method is as follows:

[0055] (1) In an argon-filled glove box (moisture content less than 0.01 ppm, oxygen content less than 1 ppm), lithium oxide, lithium sulfide, phosphorus pentasulfide, and phosphorus pentoxide were weighed in a molar ratio of 0.5:3:0.9:0.6. Stainless steel beads with a particle size of 10 mm were then prepared at a bead-to-batch ratio of 8:1. The weighed raw materials and ball milling beads were placed in a sealed ball milling jar. Finally, high-energy ball milling was performed at 1800 rpm for 6 h.

[0056] (2) The ball-milled material was transferred into a quartz crucible, and the temperature was raised from room temperature to 270°C at a rate of 2°C / min, and kept at this temperature for 2 hours; after cooling naturally to room temperature, the crucible was taken out to obtain a chemical formula of Li7P3S 7.5 O 3.5 sulfide solid electrolyte.

[0057] Example 2

[0058] This embodiment provides a sulfide solid electrolyte. The difference from Example 1 is that the molar ratio of lithium oxide, lithium sulfide, phosphorus pentasulfide and phosphorus pentoxide is 3:0.5:1.4:0.1. The remaining steps are the same as those in Example 1 and are not repeated here.

[0059] Example 3

[0060] This embodiment provides a sulfide solid electrolyte. The difference from Example 1 is that the molar ratio of lithium oxide, lithium sulfide, phosphorus pentasulfide and phosphorus pentoxide is 3.4:0.1:1.48:0.02. The remaining steps are the same as those in Example 1 and are not repeated here.

[0061] Example 4

[0062] This embodiment provides a sulfide solid electrolyte. The difference from Example 1 is that the molar ratio of lithium oxide to phosphorus pentasulfide is 3.5:1.5. The remaining steps are the same as those in Example 1 and are not repeated here.

[0063] Example 5

[0064] This embodiment provides a sulfide solid electrolyte, and the preparation method is as follows:

[0065] (1) In an argon-filled glove box (moisture content less than 0.01 ppm, oxygen content less than 1 ppm), lithium oxide, phosphorus pentasulfide, and phosphorus pentoxide were weighed in a molar ratio of 3.5:1.25:0.25. Stainless steel beads with a particle size of 10 mm were then prepared at a bead-to-batch ratio of 8:1. The weighed raw materials and ball milling beads were placed in a sealed ball milling jar. Finally, high-energy ball milling was performed at 1800 rpm for 6 h.

[0066] (2) The ball-milled material was transferred into a quartz crucible, and the temperature was raised from room temperature to 270°C at a rate of 2°C / min, and kept at this temperature for 2 hours; after cooling naturally to room temperature, the crucible was taken out to obtain the chemical formula Li7P3S 6.25 O 4.75 sulfide solid electrolyte.

[0067] Example 6

[0068] This embodiment provides a sulfide solid electrolyte. The difference from Example 5 is that the molar ratio of lithium oxide, phosphorus pentasulfide and phosphorus pentoxide is 3.5:0.75:0.75. The remaining steps are the same as those in Example 5 and are not repeated here. The chemical formula is Li7P3S 3.75 O 7.25 sulfide solid electrolyte.

[0069] Example 7

[0070] This embodiment provides a sulfide solid electrolyte. The difference from Example 5 is that the molar ratio of lithium oxide, phosphorus pentasulfide and phosphorus pentoxide is 3.5:0.25:1.25. The remaining steps are the same as those in Example 5 and will not be repeated here. The chemical formula is Li7P3S 1.25 O 9.75 sulfide solid electrolyte.

[0071] Example 8

[0072] This embodiment provides a sulfide solid electrolyte. The difference from Example 5 is that the molar ratio of lithium sulfide to phosphorus pentoxide is 3.5:1.5. The remaining steps are the same as those in Example 5 and will not be repeated here. The chemical formula is Li7P3S 3.5 O 7.5 sulfide solid electrolyte.

[0073] Example 9

[0074] This embodiment provides a sulfide solid electrolyte. The difference from Example 5 is that the molar ratio of lithium oxide, lithium sulfide and phosphorus pentasulfide is 2.5:1:1.5. The remaining steps are the same as those in Example 5 and will not be repeated here. The chemical formula is Li7P3S 8.5 O 2.5 sulfide solid electrolyte.

[0075] Example 10

[0076] This embodiment provides a sulfide solid electrolyte. The difference from Example 5 is that the molar ratio of lithium oxide, lithium sulfide and phosphorus pentasulfide is 1.5:2:1.5. The remaining steps are the same as those in Example 5 and will not be repeated here. The chemical formula is Li7P3S9.5 O 1.5 sulfide solid electrolyte.

[0077] Example 11

[0078] This embodiment provides a sulfide solid electrolyte. The difference from Example 5 is that the molar ratio of lithium oxide, lithium sulfide and phosphorus pentasulfide is 0.5:3:1.5. The remaining steps are the same as those in Example 5 and will not be repeated here. The chemical formula is Li7P3S 10.5 O 0.5 sulfide solid electrolyte.

[0079] Example 12

[0080] This embodiment provides a sulfide solid electrolyte. The difference from embodiment 9 is that the bead-to-material ratio is 10:1. The remaining steps are the same as those in embodiment 9 and will not be repeated here. The chemical formula is Li7P3S 8.5 O 2.5 sulfide solid electrolyte.

[0081] Example 13

[0082] This embodiment provides a sulfide solid electrolyte. The difference from embodiment 9 is that the bead-to-material ratio is 12:1. The remaining steps are the same as those in embodiment 9 and will not be repeated here. The chemical formula is Li7P3S 8.5 O 2.5 sulfide solid electrolyte.

[0083] Example 14

[0084] This embodiment provides a sulfide solid electrolyte, and the preparation method is as follows:

[0085] (1) Same as the steps in Example 9.

[0086] (2) The ball-milled material was transferred into a quartz crucible, and the temperature was raised from room temperature to 250°C at a rate of 2°C / min, and kept at this temperature for 2 hours; after cooling naturally to room temperature, the crucible was taken out to obtain the chemical formula Li7P3S 8.5 O 2.5 of solid electrolytes.

[0087] Example 15

[0088] This embodiment provides a sulfide solid electrolyte, and the preparation method is as follows:

[0089] (1) Same as the steps in Example 9.

[0090] (2) The ball-milled material was transferred into a quartz crucible, and the temperature was raised from room temperature to 290°C at a rate of 2°C / min, and kept at this temperature for 2 hours; after cooling naturally to room temperature, the crucible was taken out to obtain a chemical formula of Li7P3S 8.5 O 2.5 sulfide solid electrolyte.

[0091] Comparative Example 1

[0092] This comparative example provides a solid electrolyte. The difference from Example 9 is that the rotation speed of the high-energy ball mill is 500 rpm and the ball milling time is 20 h. The remaining raw materials and preparation methods are the same as those in Example 9 and are not repeated here.

[0093] The comparative example failed to prepare Li7P3S 8.5 O 2.5 of solid electrolytes.

[0094] Comparative Example 2

[0095] This comparative example provides a solid electrolyte. The difference from Example 9 is that the stainless steel beads used are 5 mm, the ball milling time is 6 h, and the other raw materials and preparation methods are the same as those in Example 1.

[0096] The comparative example failed to prepare Li7P3S 8.5 O 2.5 of solid electrolytes.

[0097] Comparative Example 3

[0098] This comparative example provides a solid electrolyte. The difference from Example 9 is that the 10 mm stainless steel beads are replaced with 10 mm agate beads, the ball milling time is 6 h, and the remaining raw materials and preparation method are the same as those in Example 1.

[0099] The comparative example failed to prepare Li7P3S 8.5 O 2.5 of solid electrolytes.

[0100] Test Example 1

[0101] The solid electrolyte obtained in the example was tested for ionic conductivity and electronic conductivity.

[0102] Ionic conductivity: Weigh 0.13g of the above solid electrolyte and place it in a stainless steel mold for tableting. Place a piece of carbon-coated aluminum foil at each end as a blocking electrode. Press it into a small disc with a diameter of 10mm at 10MPa. Use a micrometer to measure the thickness of the sulfide electrolyte disc as L (unit: mm). Use an electrochemical workstation to test the above sample using the AC impedance method at 25°C, where the frequency range is 1Hz to 7MHz, and calculate the ionic conductivity σ; σ = L / Re×S; where Re represents the impedance of the sample being tested (ohm), obtained from the intersection of the semicircle and the oblique line in the electrochemical impedance spectrum; S represents the area of ​​the electrode (cm 2 ).

[0103] Electronic conductivity: Weigh 0.13g of the above-mentioned sulfide electrolyte and place it in a stainless steel mold for tableting. Place a piece of carbon-coated aluminum foil at each end as a blocking electrode. Press it into a small disc with a diameter of 10mm at 10MPa. Use a micrometer to measure the thickness of the sulfide electrolyte disc as d (unit: mm). Use an electrochemical workstation to test the above sample using the DC polarization method at 25℃, and calculate the electronic conductivity G; G = d / R×S, R = U / I; where R represents the impedance of the sample being tested (ohm), U is the test applied voltage, I is the measured current, and S represents the area of ​​the electrode (cm 2 ).

[0104] The obtained data are shown in Table 1 below.

[0105] Table 1

[0106]

[0107] Table 1 shows the following conclusions: Solid electrolytes with the same chemical formula can be obtained using different molar ratios of raw materials, that is, using different values ​​for x and y. Furthermore, the greater the amount of phosphorus pentoxide (P2S5) and the smaller the amount of lithium oxide (Li2O), that is, the smaller the value of y and the larger the value of x, the higher the ionic conductivity of the resulting solid electrolyte.

[0108] Table 2

[0109]

[0110] From Table 2 above, we can see that using raw materials with different molar ratios, that is, different values ​​of x and y, we can also obtain solid electrolytes with different chemical formulas. 7.5 O 3.5 Doping is performed on the basis of this. When phosphorus pentoxide (P2O5) is doped, the smaller the y value is, the higher the ionic conductivity is. When lithium sulfide (Li2S) is doped, the ionic conductivity is highest when x is about 1.

[0111] Table 3

[0112]

[0113] It can be seen from Table 3 above that in Examples 9, 12 and 13, appropriately increasing the bead-to-material ratio during the ball milling process, that is, increasing the ball milling energy, is conducive to synthesizing products with higher ion conductivity. It can be seen from Examples 9, 14 and 15 that for Li7P3S 8.5 O 2.5 The optimal annealing temperature is about 270℃.

[0114] Li7P3S in Comparative Examples 1-3 and Examples 9, 12 and 13 8.5 O 2.5 The relationship between ball milling energy and ionic conductivity is plotted. Figure 1 .from Figure 1 It can be seen that as the ball milling energy increases, the ionic conductivity of the product decreases. In order to balance the ball milling efficiency and preparation cost, it is recommended that the ball milling energy be ≥455mJ.

[0115] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A sulfide solid electrolyte, characterized in that: The sulfide solid electrolyte is lithium phosphorus sulfur oxide, and the chemical formula of the lithium phosphorus sulfur oxide is Li7P3S 7.5+x-5y O 3.5-（x-5y） ; Among them, 0≤x≤3.5, 0≤y≤1.5, -7.5 <x-5y≤2,1.5≤3.5-(x-5y)<11; The lithium phosphorus oxysulfide is a sulfur-oxygen mixed coordination structure, wherein x is the molar amount of lithium sulfide in the raw material, and y is the molar amount of phosphorus pentoxide in the raw material, and the ratio of S / O is adjusted by x and y; The sulfide solid electrolyte is prepared by mixing lithium oxide, lithium sulfide, phosphorus pentasulfide and phosphorus pentoxide, ball milling the mixture, and then heat treating the mixture to obtain the sulfide solid electrolyte. Wherein, the total ball milling energy is ≥455mJ.

2. The sulfide solid electrolyte according to claim 1, characterized in that The Li7P3S 7.5+x-5y O 3.5-（x-5y） In, 1≤x≤3.5, y=0.

3. The sulfide solid electrolyte according to claim 1, characterized in that The ball milling speed is 1000-2000 rpm; The radius of the ball milling beads used in the ball milling is 0.4-0.7 cm, and the density is 5.6-15.6 g / cm 3 .

4. The sulfide solid electrolyte according to claim 3, characterized in that The bead-to-material ratio of the ball mill is 7-12:1; The ball milling beads include zirconia beads, stainless steel beads and tungsten carbide beads.

5. The sulfide solid electrolyte according to claim 4, characterized in that The ball milling is performed in a ball mill jar having a height-to-diameter ratio of 1.2 to 1.

4.

6. The sulfide solid electrolyte according to claim 5, characterized in that During the ball milling process, the total volume of the ball milling beads and the material does not exceed 70% of the volume of the ball milling jar.

7. The sulfide solid electrolyte according to any one of claims 1 to 6, characterized in that The ball milling time is 1 to 30 hours.

8. The sulfide solid electrolyte according to any one of claims 1 to 6, characterized in that The moisture content of the ball milling environment is less than 0.01 ppm, and the oxygen content is less than 1 ppm.

9. The sulfide solid electrolyte according to any one of claims 1 to 6, characterized in that The heat treatment process is as follows: in an inert atmosphere, the temperature is increased from room temperature to 250-300° C. at a heating rate of 1-5° C. / min, and the temperature is kept at this temperature for 1-3 hours.

10. The sulfide solid electrolyte according to any one of claims 1 to 6, characterized in that The molar ratio of the lithium oxide, the lithium sulfide, the phosphorus pentasulfide and the phosphorus pentoxide is (3.5-x):x:(1.5-y):y; Among them, 0≤x≤3.5, 0≤y≤1.5, -7.5 <x-5y≤2。

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