Preparation method of solid electrolyte powder and lithium ion battery

Abstract

The application provides a preparation method of solid electrolyte powder and a lithium ion battery. The preparation method comprises the following steps: step S1, performing preliminary crushing on a solid electrolyte material to obtain pre-milling powder; step S2, dispersing the pre-milling powder in a solvent and wet milling to form a slurry; and step S3, removing the solvent in the slurry to obtain the solid electrolyte powder. The solvent is a composite solvent, and the composite solvent comprises a hydrofluoroether and an ester compound. By using the composite solvent comprising the hydrofluoroether and the ester compound to wet mill the solid electrolyte material, the dispersion effect of the solid electrolyte powder is significantly improved, the solid electrolyte powder with a smaller particle size is obtained, meanwhile, the ionic conductivity of the solid electrolyte powder still maintains a high level, and the cycle stability of the battery is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a method for preparing solid electrolyte powder and a lithium-ion battery. Background Technology

[0002] With the increasing demand for high-safety, high-energy-density energy storage devices in the new energy industry, all-solid-state batteries have become the core development direction of next-generation battery technology due to their breakthrough in overcoming the thermal runaway risk limitations of traditional liquid electrolyte batteries. Among them, sulfide solid electrolytes (such as LiPSClBr) have become particularly advantageous due to their ultra-high ionic conductivity (>10). - Electrolytes (³ S / cm) have become one of the key materials. To fully utilize their performance, the particle size of electrolytes used as positive and negative electrodes in solid-state batteries needs to be below the micrometer level. However, during large-scale preparation, the nano-agglomeration of electrolyte powders can lead to blockage of ion transport channels, which severely restricts battery performance.

[0003] To address this challenge, wet grinding has been widely adopted as an effective pulverization method. Among existing electrolyte powder grinding methods, wet grinding has advantages such as small particle size, stability, and mass production capability. However, in practical applications, the selected solvent system has a series of irreconcilable defects. On the one hand, polar solvents react with electrolytes, while non-polar solvents cannot wet the electrolytes in wet processing, resulting in poor grinding effect. Moreover, most non-polar solvents are flammable, explosive, or highly toxic, which cannot meet the needs of industrial scale-up.

[0004] Currently, the solvents used in wet milling processes for solid electrolytes mainly include N-methylpyrrolidone (NMP), toluene, and chlorobenzene. While these solvents can achieve dispersion and pulverization of electrolyte powders to some extent, their use brings multiple problems: 1. Toxicity and safety issues: Solvents such as NMP and toluene are toxic and flammable, posing a threat to human health and increasing safety hazards in production. Therefore, the use of these solvents is strictly limited, affecting the compliance and sustainability of battery material preparation. 2. Chemical pollution issues: Chlorinated solvents such as chlorobenzene leave residual Cl- in the milling process. - Ions can contaminate the electrolyte, leading to a significant decrease in its ionic conductivity. This problem severely limits the performance of electrolyte materials, thereby affecting the overall performance of all-solid-state batteries.

[0005] In summary, existing solvent systems have significant shortcomings in terms of safety, environmental friendliness, process feasibility, and cost control, failing to meet green manufacturing standards. This has become a key bottleneck restricting the large-scale production of solid electrolytes. Therefore, developing a novel solvent system capable of effectively dispersing and micronizing solid electrolytes during milling while maintaining high ionic conductivity, reducing energy consumption, and ensuring environmental compliance has become a crucial technical challenge that urgently needs to be addressed in this field.

[0006] In view of the above, this application is hereby submitted. Summary of the Invention

[0007] The main objective of this invention is to provide a method for preparing solid electrolyte powder and a lithium-ion battery, in order to solve the problems in the prior art where solid electrolytes are prone to agglomeration during pulverization, making them difficult to disperse and micronize. Although wet grinding is an effective pulverization method that can achieve dispersion and pulverization of solid electrolyte powder to a certain extent, the solvents required for wet grinding currently have many drawbacks, such as being toxic and environmentally unfriendly, and causing pollution to solid electrolytes, thereby reducing the ionic conductivity of solid electrolytes.

[0008] To achieve the above objectives, according to one aspect of the present invention, a method for preparing solid electrolyte powder is provided, the method comprising the following steps: step S1, pre-crushing solid electrolyte material to obtain pre-ground powder; step S2, dispersing the pre-ground powder in a solvent and wet-milling it to form a slurry; step S3, removing the solvent from the slurry to obtain solid electrolyte powder; wherein the solvent is a composite solvent, the composite solvent comprising hydrofluoroether and ester compounds.

[0009] Furthermore, by mass percentage, the content of the hydrofluoroether in the composite solvent is 85-99 wt%, and the content of the ester compound is 1-15 wt%.

[0010] Further, the hydrofluoroether includes at least one of HFE-254, HFE-347, HFE-374, HFE-449, HFE-458, HFE-7000, HFE-7100, HFE-7160, HFE-7200, HFE-7300, HFE-7500, and HFE-7514.

[0011] Furthermore, the ester compounds include at least one of methyl formate, ethyl formate, ethyl acetate, propyl acetate, butyl propionate, pentyl propionate, hexyl propionate, butyl butyrate, hexyl butyrate, heptyl butyrate, ethyl valerate, pentyl valerate, and hexyl valerate.

[0012] Furthermore, the solid content of the slurry is 10~50wt%.

[0013] Furthermore, in step S1, the solid electrolyte material is in block form; the D50 particle size of the pre-ground powder is 3~20μm.

[0014] Furthermore, in step S3, the D50 particle size of the solid electrolyte powder is 0.7~1.7μm.

[0015] Furthermore, solid electrolyte materials include sulfide-based solid electrolytes.

[0016] Furthermore, the sulfide-based solid electrolyte includes at least one of Li2S-P2S5, Li2S-SiS2, LiX-Li2S-SiS2, LiX-Li2S-P2S5, LiX-Li2O-Li2S-P2S5, LiX-Li2S-P2O5, and LiX-Li3PO4-P2S5, wherein the "X" in LiX represents a halogen element.

[0017] Furthermore, in step S2, wet grinding is sand grinding.

[0018] Furthermore, the grinding time is 40-60 minutes.

[0019] Furthermore, the linear velocity of the sand mill is 7~12m / s.

[0020] Further, step S3 includes sequentially performing solid-liquid separation and drying on the slurry to obtain solid electrolyte powder.

[0021] Furthermore, the solid-liquid separation method is centrifugal separation.

[0022] Furthermore, the drying process includes a first drying and a second drying, wherein the temperature of the first drying is 60~80℃ and the temperature of the second drying is 100~140℃.

[0023] According to another aspect of the present invention, a lithium-ion battery is provided, the lithium-ion battery comprising a solid electrolyte, wherein the solid electrolyte is a solid electrolyte powder prepared by the preparation method provided in the first aspect above.

[0024] By applying the technical solution of this invention, wet milling of solid electrolyte materials using a composite solvent containing hydrofluoroethers and ester compounds effectively wets the solid electrolyte materials, significantly improving the dispersion of the solid electrolyte powder, reducing particle agglomeration, and yielding solid electrolyte powder with smaller particle sizes. Simultaneously, the composite solvent of hydrofluoroethers and ester compounds has minimal impact on the solid electrolyte, effectively ensuring that the solid electrolyte powder obtained after wet milling has high ionic conductivity, thereby significantly improving battery safety and electrochemical performance. Furthermore, as a non-toxic and environmentally friendly solvent, the preparation method provided in this application avoids the use of toxic and harmful solvents, complies with green manufacturing standards, and is simple to prepare, suitable for industrial-scale production, possessing broad market prospects and application value. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0026] As described in the background section of this application, existing technologies suffer from the problem that solid electrolytes tend to agglomerate during pulverization, making them difficult to disperse and micronize. While wet milling is an effective pulverization method that can achieve dispersion and pulverization of solid electrolyte powder to some extent, the solvents required for wet milling currently have many drawbacks, such as toxicity, environmental unfriendliness, and pollution of the solid electrolyte, leading to a decrease in its ionic conductivity. To address these issues, this application provides a method for preparing solid electrolyte powder and a lithium-ion battery.

[0027] In a first typical embodiment of this application, a method for preparing solid electrolyte powder is provided, the method comprising the following steps: step S1, pre-crushing the solid electrolyte material to obtain pre-ground powder; step S2, dispersing the pre-ground powder in a solvent and wet-grinding it to form a slurry; step S3, removing the solvent from the slurry to obtain solid electrolyte powder; wherein the solvent is a composite solvent, the composite solvent including hydrofluoroether and ester compounds.

[0028] By using a composite solvent containing hydrofluoroethers and esters for wet milling of solid electrolyte materials, the solid electrolyte material can be effectively wetted, significantly improving the dispersion of the solid electrolyte powder, reducing particle agglomeration, and obtaining solid electrolyte powder with smaller particle size. Simultaneously, the composite solvent of hydrofluoroethers and esters has minimal impact on the solid electrolyte, effectively ensuring that the solid electrolyte powder obtained after wet milling has high ionic conductivity, thereby significantly improving battery safety and electrochemical performance. Furthermore, as the composite solvent is non-toxic and environmentally friendly, the preparation method provided in this application avoids the use of toxic and harmful solvents, complies with green manufacturing standards, and is simple to prepare, suitable for industrial-scale production, with broad market prospects and application value.

[0029] This application first performs preliminary crushing of solid electrolyte materials to obtain pre-ground powder. This process can not only effectively reduce the particle size of the material but also reduce costs, thus preparing for subsequent wet grinding. Then, the pre-ground powder is wet-ground with a solvent, which helps to promote the dispersion of the pre-ground powder in the solvent, thereby further improving the grinding efficiency.

[0030] In some embodiments, the content of hydrofluoroether in the composite solvent is 85-99 wt%, and the content of ester compounds is 1-15 wt%, by mass percentage. At these specific amounts, the hydrofluoroether and ester compounds synergistically improve the dispersibility of the solid electrolyte powder during wet milling, further reducing the particle size of the solid electrolyte powder obtained after wet milling, while ensuring excellent ionic conductivity. Specifically, the hydrofluoroether, due to its volatility, can be quickly removed, avoiding adverse effects on the solid electrolyte and maintaining high ionic conductivity. Simultaneously, the ester compounds, as dispersants, can further improve the dispersibility of the solid electrolyte material in the composite solvent, thereby obtaining solid electrolyte powder with smaller particle size. Furthermore, as non-toxic solvents, the hydrofluoroether and ester compounds achieve a green and environmentally friendly process.

[0031] Typical, but not limiting, content of hydrofluoroethers in the complex solvent, by mass percentage, is 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, or any range of two such values; content of ester compounds is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, or any range of two such values.

[0032] To further reduce the particle size of the solid electrolyte powder and effectively ensure its excellent ionic conductivity, hydrofluoroethers are preferably one or more of HFE-254, HFE-347, HFE-374, HFE-449, HFE-458, HFE-7000, HFE-7100, HFE-7160, HFE-7200, HFE-7300, HFE-7500, and HFE-7514, as well as derivatives thereof.

[0033] To further improve the dispersibility of solid electrolyte powder during wet milling and thus reduce the particle size of the solid electrolyte powder obtained after wet milling, preferred ester compounds include any one or more of methyl formate, ethyl formate, ethyl acetate, propyl acetate, butyl propionate, pentyl propionate, hexyl propionate, butyl butyrate, hexyl butyrate, ethyl valerate, pentyl valerate, and hexyl valerate; more preferably, any one or more of isopropyl acetate, tert-butyl propionate, tert-butyl butyrate, isobutyl isobutyrate, pentyl neovalerate, hexyl neovalerate, ethyl isovalerate, isoamyl isovalerate, and isohexyl isovalerate; even more preferably, any one or more of isopropyl acetate, isobutyl isobutyrate, isoamyl isovalerate, and isohexyl isovalerate.

[0034] In some embodiments, the solid content of the slurry is 10-50 wt%. This range ensures that the solid electrolyte can be sufficiently dispersed and refined in the composite solvent during wet milling, thereby facilitating the reduction of the D50 particle size of the solid electrolyte powder and improving its ionic conductivity. Excessive solid content will cause the solid electrolyte to easily agglomerate during wet milling, leading to an increase in the particle size of the solid electrolyte powder in the slurry and further blocking of ion transport channels. Conversely, insufficient solid content will reduce the effective contact and friction between the solid electrolyte powder particles, resulting in insufficient milling and making it difficult to achieve the desired fineness of the solid electrolyte powder particle size.

[0035] Typical, but not limiting, solid content of the slurry is 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, or any range of two values.

[0036] In some embodiments, in step S1, the solid electrolyte material is in block form, and the pre-ground powder has a D50 particle size of 3~20μm, so as to further promote the uniform refinement of the solid electrolyte powder in the subsequent grinding process and improve the grinding efficiency.

[0037] To further promote uniform mixing, the mixing equipment in step S1 is preferably selected from a pneumatic mixer or an electric mixer.

[0038] In some embodiments, in step S3, the D50 particle size of the solid electrolyte powder is 0.7~1.7 μm. Having a D50 particle size within this range after wet milling is beneficial for forming a more uniform and dense electrolyte layer and an efficient ion transport network during subsequent battery assembly, thereby significantly enhancing ion conductivity and improving the overall electrochemical performance of the solid-state battery.

[0039] Typical, but not limiting, D50 particle sizes of pre-ground powders include 3 μm, 5 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or any combination of two values; D50 particle sizes of solid electrolyte powders include 0.7 μm, 0.75 μm, 0.85 μm, 0.95 μm, 1.3 μm, 1.67 μm, 1.7 μm, or any combination of two values.

[0040] The solid electrolyte materials used in this application include, but are not limited to, sulfide-based solid electrolytes. In some embodiments, sulfide-based solid electrolytes are preferred. More preferably, sulfide-based solid electrolytes include any one or more of Li₂S-P₂S₅, Li₂S-SiS₂, LiX-Li₂S-SiS₂, LiX-Li₂S-P₂S₅, LiX-Li₂O-Li₂S-P₂S₅, LiX-Li₂S-P₂O₅, and LiX-Li₃PO₄-P₂S₅, wherein the "X" in LiX represents a halogen element, preferably Cl, Br, or I. The above-mentioned solid electrolyte materials are preferred to further improve the ionic conductivity of the solid electrolyte powder, thereby enhancing the electrochemical performance of the battery.

[0041] In this application, Li2S-P2S5 refers to a material prepared using a raw material composition containing Li2S and P2S5; Li2S-SiS2 refers to a material prepared using a raw material composition containing Li2S and SiS2; LiX-Li2S-SiS2 refers to a material prepared using a raw material composition containing LiX, Li2S, and SiS2; LiX-Li2S-P2S5 refers to a material prepared using a raw material composition containing LiX, Li2S, and P2S5; LiX-Li2O-Li2S-P2S5 refers to a material prepared using a raw material composition containing LiX, Li2O, Li2S, and P2S5; LiX-Li2S-P2O5 refers to a material prepared using a raw material composition containing LiX, Li2S, and P2O5; and LiX-Li3PO4-P2S5 refers to a material prepared using a raw material composition containing LiX, Li3PO4, and P2S5.

[0042] To further improve grinding efficiency, wet grinding is preferred as sand milling.

[0043] To further ensure the production of solid electrolyte powder with small particle size and high ionic conductivity, the preferred milling time is 40-60 minutes, the milling linear speed is 7-12 m / s, and the preferred pump speed is 4-30 L / h. If the milling time is too short or the milling speed is too slow, the solid electrolyte powder cannot be sufficiently refined, resulting in larger particle sizes and thus reducing the electrochemical performance of the battery. Conversely, if the milling time is too long or the milling speed is too fast, energy consumption increases, equipment wear intensifies, and the structural stability of the solid electrolyte powder is affected, thereby reducing the electrochemical performance of the solid electrolyte.

[0044] Typical, but not limiting, milling times may be 40 min, 50 min, 60 min, or any range of two values; milling linear speeds may be 7 m / s, 10 m / s, 12 m / s, or any range of two values.

[0045] To further improve crushing efficiency, in step S1, the equipment for preliminary crushing is selected from any one or more of the following: agate mortar and pestle, high-speed stirring crusher, and ball mill.

[0046] In some embodiments, step S3 includes sequentially performing solid-liquid separation and drying on the slurry to obtain solid electrolyte powder. Firstly, solid-liquid separation removes most of the solvent from the slurry, significantly reducing the amount of solvent that needs to be evaporated during drying, thereby improving drying efficiency and reducing energy consumption. Subsequently, rapid removal of the remaining solvent through drying at lower humidity helps maintain the dispersion of the powder, further reducing the risk of agglomeration of the solid electrolyte powder in a wet state.

[0047] In some embodiments, the drying in step S3 includes a first drying and a second drying. The temperature of the first drying is 60-80°C, and the temperature of the second drying is 100-140°C. The drying process employs a gradual heating method, that is, removing hydrofluoroethers first at a lower temperature and then removing ester solvents at a higher temperature. This effectively reduces energy consumption, while suppressing the damage of high temperature to the solid electrolyte structure, further ensuring the structural integrity of the solid electrolyte powder, and improving the ionic conductivity of the solid electrolyte powder.

[0048] Typically, but not limitingly, the temperature for the first drying is 60°C, 70°C, 80°C, or any combination of two of these values; the temperature for the second drying is 100°C, 120°C, 140°C, or any combination of two of these values.

[0049] This application does not impose any particular limitation on the method of solid-liquid separation; all commonly used solid-liquid separation methods in the art can be applied to this application. To further improve separation efficiency, centrifugal separation is preferred for solid-liquid separation.

[0050] This application does not impose any particular limitation on the drying method; any drying method commonly used in the art can be applied to this application. To further improve the drying rate, vacuum drying and / or spray drying are preferred, with vacuum drying being even more preferred.

[0051] In another typical embodiment of this application, a lithium-ion battery is provided, which includes a solid electrolyte, wherein the solid electrolyte is a solid electrolyte powder prepared by the preparation method provided in the first typical embodiment above.

[0052] By using a composite solvent containing hydrofluoroethers and esters to wet-mill solid electrolyte materials, the solid electrolyte materials can be effectively wetted, significantly improving the dispersion of solid electrolyte powder, reducing particle agglomeration, and obtaining solid electrolyte powder with smaller particle size. At the same time, the composite solvent containing hydrofluoroethers and esters has little impact on the solid electrolyte, effectively ensuring that the solid electrolyte powder obtained after wet milling has high ionic conductivity, thereby significantly improving the safety and electrochemical properties of lithium-ion batteries.

[0053] Furthermore, as a non-toxic and environmentally friendly solvent, composite solvents meet green manufacturing standards, and the resulting refined solid electrolyte powders have broad market prospects and application value in lithium-ion batteries.

[0054] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0055] Example 1

[0056] This embodiment provides a method for preparing solid electrolyte powder, including the following steps:

[0057] (1) Using a high-speed stirring crusher, the sintered sulfide-based solid electrolyte LiPSClBr (LiCl-0.6LiBr-0.5P2S5-1.9Li2S) was stirred and crushed for 30s at a speed of 10000r / min. This process was repeated three times to obtain pre-ground powder. The D50 particle size of the pre-ground powder was 10μm.

[0058] (2) Weigh 736g of hydrofluoroether HFE-7000 and 64g of isoamyl isovalerate (in the composite solvent, the content of hydrofluoroether HFE-7000 is 92wt% and the content of isoamyl isovalerate is 8wt%) and mix them to obtain a composite solvent; then weigh 200g of pre-ground powder and add it to the composite solvent and mix thoroughly to obtain a mixture.

[0059] (3) Using 0.8mm zirconia beads as grinding media, fill the mixture into the sand mill chamber, start the sand mill, set the parameters of the sand mill, linear speed 7m / s, pump speed 21L / h, and continuously sand mill for 60min to form a slurry.

[0060] (4) The slurry after sand milling is placed in a centrifuge for centrifugation. The centrifuge parameters are 4000 rpm and the centrifugation time is 10 min. Then it is placed in a vacuum oven and dried continuously at 80°C for 12 h to remove the hydrofluoric ether. Then the temperature is raised to 140°C and dried continuously for 12 h to further remove the remaining solvent and obtain solid electrolyte powder.

[0061] Example 2

[0062] (1) Using a high-speed mixing crusher, the sintered sulfide-based solid electrolyte LiPSClBr was mixed and crushed at a speed of 10000r / min for 30s, and repeated three times to obtain a preliminary powder. The D50 particle size of the preliminary powder was 10um.

[0063] (2) Weigh 736g of hydrofluoroether HFE-7000 and 64g of isobutyl isobutyrate and mix them to obtain a composite solvent; (in the composite solvent, the content of hydrofluoroether HFE-7000 is 92wt% and the content of isobutyl isobutyrate is 8wt%); then weigh 200g of the prepared powder and add it to the composite solvent and mix thoroughly to obtain a mixture.

[0064] (3) Using 0.8mm zirconia beads as grinding media, fill the sand mill chamber with the mixture, start the sand mill, set the parameters of the sand mill, linear speed 7m / s, pump speed 21L / h, and continuously sand mill for 60min to form a slurry;

[0065] (4) The electrolyte slurry after sand milling is placed in a centrifuge and centrifuged at 4000 rpm for 10 min. Then it is placed in a vacuum oven and dried continuously at 80°C for 12 h to remove the hydrofluoric ether. The temperature is then increased to 140°C and dried continuously for 12 h to further remove the remaining solvent, thus obtaining solid electrolyte powder.

[0066] Example 3

[0067] The difference from Example 1 is that the amount of hydrofluoroether HFE-7000 in this example is adjusted to 776g, and the amount of isoamyl isovalerate is adjusted to 24g (in the composite solvent, the content of hydrofluoroether HFE-7000 is 97wt%, and the content of isoamyl isovalerate is 3wt%).

[0068] Example 4

[0069] The difference from Example 1 is that the amount of hydrofluoroether HFE-7000 in this example is adjusted to 720g, and the amount of isoamyl isovalerate is adjusted to 80g (in the composite solvent, the content of hydrofluoroether HFE-7000 is 90wt%, and the content of isoamyl isovalerate is 10wt%).

[0070] Example 5

[0071] The difference from Example 1 is that the amount of hydrofluoroether HFE-7000 in this example is adjusted to 792g, and the amount of isoamyl isovalerate is adjusted to 8g (in the composite solvent, the content of hydrofluoroether HFE-7000 is 99wt%, and the content of isoamyl isovalerate is 1wt%).

[0072] Example 6

[0073] The difference from Example 1 is that the amount of hydrofluoroether HFE-7000 in this example is adjusted to 680g and the amount of isoamyl isovalerate is adjusted to 120g (in the composite solvent, the content of hydrofluoroether HFE-7000 is 85wt% and the content of isoamyl isovalerate is 15wt%).

[0074] Example 7

[0075] The difference from Example 1 is that the amount of hydrofluoroether HFE-7000 in this example is adjusted to 640g, and the amount of isoamyl isovalerate is adjusted to 160g (in the composite solvent, the content of hydrofluoroether HFE-7000 is 80wt%, and the content of isoamyl isovalerate is 20wt%).

[0076] Example 8

[0077] The difference from Example 1 is that the amount of hydrofluoroether HFE-7000 in this example is adjusted to 796g, and the amount of isoamyl isovalerate is adjusted to 4g (in the composite solvent, the content of hydrofluoroether HFE-7000 is 99.5wt%, and the content of isoamyl isovalerate is 0.5wt%).

[0078] Example 9

[0079] The difference from Example 1 is that in step (2) of this example, 89g of the prepared powder is weighed and added into the composite solvent and mixed thoroughly.

[0080] Example 10

[0081] The difference from Example 1 is that in step (2) of this example, 800g of the prepared powder is weighed and put into the composite solvent and mixed thoroughly.

[0082] Example 11

[0083] The difference from Example 1 is that in this example, isoamyl isovalerate in step (2) is replaced with isopropyl acetate.

[0084] Example 12

[0085] The difference from Example 1 is that in this example, isoamyl isovalerate in step (2) is replaced with isohexyl isovalerate.

[0086] Example 13

[0087] The difference from Example 1 is that hydrofluoromethyl ether is replaced with HFE-7300 in this example.

[0088] Example 14

[0089] The difference from Example 1 is that hydrofluoromethyl ether is replaced with HFE-7200 in this example.

[0090] Example 15

[0091] The difference from Example 1 is that the composite solvent in this example is replaced with HFE-347 and isobutyl isobutyrate.

[0092] Comparative Example 1

[0093] (1) Using a high-speed stirring crusher, the sintered sulfide-based solid electrolyte LiPSClBr was stirred and crushed for 30 seconds at a speed of 10000r / min. This process was repeated three times to obtain a preliminary powder from the sintered sulfide-based solid electrolyte LiPSClBr. The D50 particle size of the preliminary powder was 10μm.

[0094] (2) Weigh 800g of hydrofluoroether HFE-7000 and 200g of pre-ground powder and put them into a beaker to mix and stir to obtain a mixture;

[0095] (3) Using 0.8mm zirconia beads as grinding media, fill the mixture into the sand mill chamber, start the sand mill, set the parameters of the sand mill, linear speed 7m / s, pump speed 21L / h, and continuously sand mill for 60min to form a slurry.

[0096] (4) The slurry after sand milling is placed in a centrifuge with centrifuge parameters of 4000 rpm and centrifugation time of 10 min; then placed in a vacuum oven at 80°C for 12 h to remove hydrofluoric ethers and obtain solid electrolyte powder.

[0097] Comparative Example 2

[0098] (1) Using a high-speed stirring crusher, the sintered sulfide-based solid electrolyte LiPSClBr was stirred and crushed for 30 seconds at a speed of 10000r / min. This process was repeated three times to obtain a preliminary powder from the sintered sulfide-based solid electrolyte LiPSClBr. The D50 particle size of the preliminary powder was 10μm.

[0099] (2) Weigh 800g of isoamyl isovalerate and 200g of pre-ground powder and put them into a beaker to mix and stir to obtain a mixture.

[0100] (3) Using 0.8mm zirconia beads as grinding media, fill the sand mill chamber with the mixture, start the sand mill, set the parameters of the sand mill, linear speed 7m / s, pump speed 21L / h, and continuously sand mill for 60min to form a slurry.

[0101] (4) The electrolyte slurry after sand milling is placed in a centrifuge and centrifuged at 4000 rpm for 10 min. Then it is placed in a vacuum oven and dried continuously at 120°C for 12 h to remove the solvent and obtain solid electrolyte powder.

[0102] Comparative Example 3

[0103] (1) Using a high-speed stirring crusher, the sintered sulfide-based solid electrolyte LiPSClBr was stirred and crushed for 30 seconds at a speed of 10000r / min. This process was repeated three times to obtain a preliminary powder from the sintered sulfide-based solid electrolyte LiPSClBr. The D50 particle size of the preliminary powder was 10μm.

[0104] (2) Weigh 800g of isobutyl isobutyrate and 200g of prepared powder and put them into a beaker to mix and stir to obtain a mixture;

[0105] (3) Using 0.8mm zirconia beads as grinding media, fill the mixture into the sand mill chamber, start the sand mill, set the parameters of the sand mill, linear speed 7m / s, pump speed 21L / h, and continuously sand mill for 60min to form a slurry.

[0106] (4) The slurry after sand milling is placed in a centrifuge and centrifuged at 4000 rpm for 10 min. Then it is placed in a vacuum oven and dried continuously at 120°C for 12 h to remove the solvent and obtain solid electrolyte powder.

[0107] Test case

[0108] 1. Take a small amount of slurry from step (3) of the above-mentioned examples and comparative examples respectively, and measure the D50 particle size of the solid electrolyte in the slurry using a laser particle size analyzer. The results are shown in Table 1.

[0109] 2. Ionic conductivity performance test:

[0110] 0.2g of the solid electrolyte powder from the above examples and comparative examples were weighed and assembled with the positive and negative electrode sheets into a battery mold. The mold was then pressed using a manual press to create a simple battery. The impedance was measured using an AC impedance meter at room temperature under a frequency range of 7000kHz to 100MHz and a current of 10mV. The results are shown in Table 1. The formula for calculating the ionic conductivity is:

[0111] σ = 4 / 2 （ 1+ 2 ）

[0112] In the formula:

[0113] s — Ionic conductivity, in Siemens units per centimeter (S / cm);

[0114] L —The thickness of the sintered sample is in centimeters (cm).

[0115] π —The value is 3.14;

[0116] D — The bottom diameter of the sintered sample, in centimeters (cm);

[0117] R 1 — Fitted sample volume impedance, in ohms (Ω);

[0118] R 2 — Fitted sample grain boundary impedance, in ohms (Ω).

[0119] 3. Cyclic stability test:

[0120] Preparation steps of the positive electrode sheet: The positive electrode active material is lithium nickel cobalt manganese oxide, the solid electrolyte is the solid electrolyte powder prepared in Examples 1-15 and Comparative Examples 1-3 above, the conductive agent is VGCF (vapor-grown carbon fiber), and the binder is SBS (styrene-butadiene-styrene copolymer). The positive electrode active material, solid electrolyte powder, conductive agent, and binder are added to anisole in a mass ratio of 85:12:1.5:1.5 and stirred to obtain a positive electrode active slurry. Then, the prepared positive electrode active slurry is coated on an aluminum foil current collector and dried to obtain the positive electrode sheet.

[0121] Preparation steps of the negative electrode sheet: The negative electrode active material is graphite, the binder is SBS (styrene-butadiene-styrene copolymer), and the solid electrolyte is the solid electrolyte powder prepared in Examples 1-15 and Comparative Examples 1-3 above. The negative electrode active material, the negative electrode active material, and the solid electrolyte are added to anisole at a mass ratio of 85:2:13 and stirred to obtain a uniformly dispersed negative electrode active material slurry. The prepared negative electrode active slurry is coated onto a copper foil current collector and dried to obtain the negative electrode sheet.

[0122] Preparation steps of solid electrolyte layer: LiPSClBr sulfide solid electrolyte (2.5μm<D50<4.0μm) and SBS are added to anisole at a mass ratio of 98:2 and mixed and stirred to prepare electrolyte slurry. The slurry is then coated on PET release film and dried to obtain solid electrolyte layer.

[0123] The preparation steps of an all-solid-state battery are as follows: the positive electrode, the solid electrolyte layer and the negative electrode are stacked together to assemble an all-solid-state battery.

[0124] Cycle stability tests were conducted on the all-solid-state batteries prepared in the above embodiments and comparative examples, and the results are shown in Table 1. The test procedure was as follows: charge and discharge performance tests were conducted in a constant temperature chamber at 25°C at a rate of 0.1C, with the test voltage range being 2.5–4.25V.

[0125] Capacity retention rate (%) after 300 cycles = Discharge capacity after 300 cycles / Discharge capacity of the first cycle × 100%.

[0126] Table 1

[0127]

[0128] Comparing the results of Examples 1, 3 to 6 with Examples 7 and 8 and Comparative Examples 1 to 3, it can be seen that in Examples 1 to 6, limiting the mass content of hydrofluoroether and ester compounds within the preferred range of this application is beneficial to improving the dispersion effect of the solid electrolyte powder, further obtaining solid electrolyte powder with smaller particle size, while maintaining a high level of ionic conductivity, thereby improving the cycle stability of the battery. In Examples 7 and Comparative Examples 2 and 3, the proportion of ester compounds in the composite solvent is too high. Although the particle size of the obtained solid electrolyte powder is smaller, the solvent has a greater impact on the solid electrolyte, resulting in a decrease in the ionic conductivity of the electrolyte after refinement, which further leads to a decrease in the cycle stability of the battery. In Example 8 and Comparative Example 1, the proportion of ester compounds in the composite solvent is too low, resulting in poor dispersibility of the solid electrolyte powder, leading to an increase in the particle size of the electrolyte after refinement, which in turn leads to a decrease in the cycle stability of the battery.

[0129] The results of Examples 1, 9, and 10 show that the solid content of the slurry is within the preferred range of this application, which is beneficial for the solid electrolyte to be fully dispersed and refined in the composite solvent, thereby reducing the particle size of the solid electrolyte powder and maintaining a high level of ionic conductivity, which in turn helps to improve the cycle stability of the battery.

[0130] The results of Examples 1, 2, 11 to 15 show that using a composite solvent containing hydrofluoric ethers and ester compounds for wet milling of solid electrolyte materials is beneficial to improving particle dispersion, promoting a reduction in particle size of the refined solid electrolyte powder, and having a relatively small impact on the solid electrolyte. This is beneficial to improving the ionic conductivity of the refined solid electrolyte powder, thereby improving the cycle stability of the battery.

[0131] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0132] By using a composite solvent containing hydrofluoroethers and esters for wet milling of solid electrolyte materials, the solid electrolyte material can be effectively wetted, significantly improving the dispersion of the solid electrolyte powder, reducing particle agglomeration, and obtaining solid electrolyte powder with smaller particle size. Simultaneously, the composite solvent of hydrofluoroethers and esters has minimal impact on the solid electrolyte, effectively ensuring that the solid electrolyte powder obtained after wet milling has high ionic conductivity, thereby significantly improving battery safety and electrochemical performance. Furthermore, as the composite solvent is non-toxic and environmentally friendly, the preparation method provided in this application avoids the use of toxic and harmful solvents, complies with green manufacturing standards, and is simple to prepare, suitable for industrial-scale production, with broad market prospects and application value.

[0133] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing solid electrolyte powder, characterized in that, The preparation method includes the following steps: Step S1: The solid electrolyte material is initially crushed to obtain pre-ground powder; Step S2: Disperse the pre-ground powder in a solvent and wet grind it to form a slurry; Step S3: Remove the solvent from the slurry to obtain solid electrolyte powder; The solvent is a composite solvent, which includes hydrofluoroethers and ester compounds.

2. The method for preparing solid electrolyte powder according to claim 1, characterized in that, By mass percentage, the content of the hydrofluoroether in the composite solvent is 85-99 wt%, and the content of the ester compound is 1-15 wt%.

3. The method for preparing solid electrolyte powder according to claim 1 or 2, characterized in that, The hydrofluoroethers include at least one of HFE-254, HFE-347, HFE-374, HFE-449, HFE-458, HFE-7000, HFE-7100, HFE-7160, HFE-7200, HFE-7300, HFE-7500, and HFE-7514.

4. The method for preparing solid electrolyte powder according to claim 1 or 2, characterized in that, The ester compounds include at least one of methyl formate, ethyl formate, ethyl acetate, propyl acetate, butyl propionate, pentyl propionate, hexyl propionate, butyl butyrate, hexyl butyrate, heptyl butyrate, ethyl valerate, pentyl valerate, and hexyl valerate.

5. The method for preparing solid electrolyte powder according to claim 1, characterized in that, The solid content of the slurry is 10~50wt%.

6. The method for preparing solid electrolyte powder according to claim 1, characterized in that, In step S1, the solid electrolyte material is in block form, and the D50 particle size of the pre-ground powder is 3~20μm; and / or, in step S3, the D50 particle size of the solid electrolyte powder is 0.7μm~1.7μm.

7. The method for preparing solid electrolyte powder according to claim 1, characterized in that, The solid electrolyte material includes a sulfide-based solid electrolyte. Preferably, the sulfide-based solid electrolyte includes at least one of Li2S-P2S5, Li2S-SiS2, LiX-Li2S-SiS2, LiX-Li2S-P2S5, LiX-Li2O-Li2S-P2S5, LiX-Li2S-P2O5, and LiX-Li3PO4-P2S5, wherein the "X" in LiX represents a halogen element.

8. The method for preparing solid electrolyte powder according to claim 1, characterized in that, In step S2, the wet grinding is sand milling, and preferably, the sand milling time is 40-60 minutes. Preferably, the linear velocity of the grinding process is 7~12m / s.

9. The method for preparing solid electrolyte powder according to claim 1, characterized in that, Step S3 includes, The slurry was subjected to solid-liquid separation and drying in sequence to obtain solid electrolyte powder; Preferably, the solid-liquid separation method is centrifugal separation; Preferably, the drying includes a first drying and a second drying, wherein the temperature of the first drying is 60~80℃ and the temperature of the second drying is 100~140℃.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a solid electrolyte, which is a solid electrolyte powder prepared by the preparation method according to any one of claims 1 to 9.

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