Solid-state electrolyte, solid-state electrolyte membrane and preparation method thereof, and solid-state battery

Abstract

The invention discloses a solid-state electrolyte, a solid-state electrolyte membrane and a preparation method thereof, and a solid-state battery, and relates to the technical field of batteries. The chemical formula of the solid electrolyte is Li6-xPS5-xQ1 + x, X is more than or equal to 0 and less than or equal to 0.6, and Q is selected from at least one of Cl, Br and I; the ionic conductivity is greater than or equal to 3mS / cm; and the particle size distribution Df satisfies the following formula: 0.9 < = Df = (D90-D10) / D50 < = 2.0. The solid electrolyte has the characteristics of small particle size, narrow particle size distribution, small specific surface area and high ionic conductivity; the tempering treatment during preparation of the solid electrolyte is beneficial to repair of grain boundary defects, reduction of surface energy, promotion of optimized arrangement of crystal grains, more concentration of particle size distribution and remarkable improvement of ionic conductivity, effectively solves the problem that the ionic conductivity of the solid electrolyte is reduced along with reduction of the particle size, and is beneficial to improvement of the electrochemical performance of the solid battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to solid electrolytes, solid electrolyte membranes and their preparation methods, and solid batteries. Background Technology

[0002] With the rapid development of electric vehicles, people are paying increasing attention to battery safety. Lithium-ion batteries commonly use liquid organic electrolytes, which are prone to leakage, leading to safety hazards such as flammability, corrosion, and explosion. All-solid-state batteries use solid electrolytes instead of flammable liquid electrolytes, and are therefore considered the next generation of energy storage devices with high safety and energy density.

[0003] Compared to liquid electrolytes, solid electrolytes have inherent drawbacks such as poor chemical stability, hardness, non-flowability, and the presence of voids and side reactions at the interface. To address these issues, using small-sized electrolyte particles, especially nanoscale particles, can potentially create a better contact interface with active materials, conductive carbon, and binders. This would improve ion conduction and enhance battery performance.

[0004] Among solid-state electrolytes, sulfide electrolytes are widely used due to their high ionic conductivity, low cost, and relatively low Young's modulus, resulting in excellent processability and the formation of good solid / solid interfaces in solid-state batteries. However, their softness makes it difficult to refine sulfide solid-state electrolytes into small-sized particles. Furthermore, even when small-sized sulfide solid-state electrolytes are obtained, they often exhibit a wide particle size distribution and large specific surface area, increasing side reactions with the cathode and hindering effective battery performance improvements. Moreover, as the particle size of sulfide electrolytes decreases, their ionic conductivity inevitably declines.

[0005] Obtaining solid electrolytes with narrow particle size distribution, small overall particle size, small specific surface area, but high ionic conductivity, as well as their preparation methods and applications, is one of the technical challenges that urgently need to be solved in this field.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a solid electrolyte, a solid electrolyte membrane and a method for preparing the same, and a solid battery to improve the above-mentioned technical problems.

[0008] This invention is implemented as follows: In a first aspect, embodiments of the present invention provide a solid electrolyte with the chemical formula Li. 6- x PS 5-x Q 1+xWhere 0 ≤ X ≤ 0.6, and Q is selected from at least one of Cl, Br, and I; The ionic conductivity of the solid electrolyte is ≥3 mS / cm; the particle size distribution Df satisfies: 0.9≤Df=(D90-D10) / D50≤2.0.

[0009] Secondly, embodiments of the present invention provide a method for preparing a solid electrolyte as described above, comprising the following steps: Solid electrolyte raw materials are mixed in proportion and subjected to solid-phase ball milling to obtain precursor powder. The precursor powder was sintered to obtain a solid electrolyte intermediate. The solid electrolyte intermediate was subjected to liquid-phase ball milling and then tempering to obtain the solid electrolyte. Among them, the temperature of sintering treatment is greater than the temperature of tempering treatment.

[0010] Thirdly, embodiments of the present invention provide a solid electrolyte membrane, including a solid electrolyte as described above or a solid electrolyte prepared by the preparation method described above.

[0011] Fourthly, embodiments of the present invention provide a method for preparing a solid electrolyte membrane as described above, comprising the following steps: A slurry is prepared by mixing solid electrolyte raw materials with an organic solvent in a mass ratio of 1:5 to 1:20. The slurry is coated onto the substrate to obtain a wet film with a thickness of 10μm-500μm; The prepared wet membrane was dried at a temperature of room temperature to 120°C for 0.5 h to 24 h to obtain a solid electrolyte membrane.

[0012] Fifthly, embodiments of the present invention provide a solid-state battery, including a solid electrolyte as described above, a solid electrolyte prepared by the preparation method described above, a solid electrolyte membrane as described above, or a solid electrolyte membrane prepared by the preparation method described above.

[0013] The present invention has the following beneficial effects: The solid electrolyte provided in this invention features small particle size, narrow particle size distribution, small specific surface area, and high ionic conductivity. During the preparation of the solid electrolyte, a tempering treatment is performed, effectively solving the common problem of decreased ionic conductivity in sulfide solid electrolytes as particle size decreases. Specifically, after tempering, the BET specific surface area of ​​the solid electrolyte decreases, the particle size distribution becomes more concentrated, and the ionic conductivity is significantly improved. The tempering treatment of the solid electrolyte in this invention helps repair grain boundary defects, reduce surface energy, and promote optimized grain arrangement, which is beneficial for improving the electrochemical performance of solid-state batteries. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The morphology test results are for the sulfide solid electrolyte obtained after tempering. Figure 2 The results show the morphology of the second sulfide solid electrolyte intermediate prepared before tempering. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0017] In a first aspect, embodiments of the present invention provide a solid electrolyte with the chemical formula Li. 6- x PS 5-x Q 1+x Where 0 ≤ X ≤ 0.6, and Q is selected from at least one of Cl, Br, and I; The ionic conductivity of the solid electrolyte is ≥3 mS / cm; the particle size distribution Df satisfies: 0.9≤Df=(D90-D10) / D50≤2.0.

[0018] It should be noted that the solid electrolyte provided by the present invention is a sulfide solid electrolyte, which has high ionic conductivity while having a small particle size.

[0019] In an optional embodiment, the D10 of the solid electrolyte is 600nm-1000nm, preferably 700nm-900nm; And / or, D50 is 1000nm-3000nm, preferably 1500nm-2500nm; And / or, D90 is 3000nm-5000nm, preferably 3500nm-4500nm; And / or, the specific surface area of ​​the solid electrolyte is 2m². 2 / g-10m 2 / g, preferably 6m 2 / g-8m 2 / g; And / or, the ionic conductivity of the solid electrolyte is 3 mS / cm-18 mS / cm.

[0020] It should be noted that when the particle size, specific surface area, and particle size distribution of the solid electrolyte are within the aforementioned ranges, they can synergize with each other. This not only increases the effective contact area between the solid electrolyte and the active materials in the positive or negative electrode, improving the utilization rate of the active materials and forming a continuous ionic conductive network, thus enhancing ionic conductivity, but also effectively reduces uneven contact coating between particles. This can effectively reduce the occurrence of side reactions between the solid electrolyte and the positive or negative electrode, reduce the tortuosity of ion migration on the electrode, and improve electrochemical performance. Simultaneously, it also facilitates an increase in the tap density of the solid electrolyte, which is beneficial for improving the rate cycle performance of the battery's positive and negative electrode sides.

[0021] Secondly, embodiments of the present invention provide a method for preparing a solid electrolyte as described above, comprising the following steps: Solid electrolyte raw materials are mixed in proportion and subjected to solid-phase ball milling to obtain precursor powder. The precursor powder was sintered to obtain a solid electrolyte intermediate. The solid electrolyte intermediate was subjected to liquid-phase ball milling and then tempering to obtain the solid electrolyte. Among them, the temperature of sintering treatment is greater than the temperature of tempering treatment.

[0022] It should be noted that traditional methods for preparing sulfide solid electrolytes typically involve multiple and varied crushing processes of intermediate or final products. This often results in irregular particle morphology (e.g., flaky particles), a wide particle size distribution, and numerous surface defects. These factors can lead to an excessively large specific surface area and low ionic conductivity for a given particle size. The preparation method provided by this invention, through the coordinated steps, yields sulfide solid electrolytes with regular particle morphology. This method helps reduce surface defects, allowing for small particle size while maintaining a low specific surface area and a narrow particle size distribution.

[0023] In an optional embodiment, the solid electrolyte raw materials include lithium source, phosphorus source, sulfur source and halogen source in a molar ratio of (5.4-6):1:(4.4-5):(1-1.6); And / or, the average particle size of the solid electrolyte raw material is independently 0.5 μm-10 μm, preferably 0.5 μm-8 μm; It should be noted that if the particle sizes of the raw materials differ significantly, segregation is prone to occur during the mixing process. Pre-treating the raw materials to similar and fine particle sizes helps to obtain a precursor powder with highly uniform composition after ball milling, which is a fundamental guarantee for the synthesis of high-purity single-phase materials. Inhomogeneous mixing will lead to the presence of impurity phases in the sintered product, severely impairing the ionic conductivity. Because the reaction occurs at the contact interface of the raw material particles, a larger contact area means shorter element diffusion paths and more reaction sites, thereby significantly improving the rate and completeness of the solid-state reaction and facilitating the synthesis of pure-phase target materials at lower temperatures.

[0024] The lithium source is selected from at least one of lithium sulfide, lithium oxide and lithium carbonate; preferably lithium sulfide. The phosphorus source is selected from at least one of phosphorus pentasulfide and phosphorus trisulfide; preferably phosphorus pentasulfide. The sulfur source is selected from at least one of lithium sulfide, phosphorus pentasulfide, and phosphorus trisulfide; preferably phosphorus pentasulfide. The halogen source is selected from at least one of lithium chloride, lithium bromide and lithium iodide; lithium chloride is preferred.

[0025] For example, the molar ratio of lithium source, phosphorus source, sulfur source and halogen source can be selected from any one of 5.4:1:4.4:1, 5.5:1:4.6:1.3, 5.8:1:4.7:1.5, 6:1:4.8:1.8 and 6:1:5:1.6, or other values ​​within the range of (5.4-6):1:(4.4-5):(1-1.6) according to actual needs.

[0026] In an optional embodiment, the ball-to-material ratio of the solid-phase ball milling treatment is (5:1)-(40:1), the rotation speed is 200rpm-600rpm, and the time is 4h-20h; It's important to note that if the ball density is low, the number of grinding balls is small, and the amount of powder is relatively large, the collision frequency between balls is low, the probability of individual powder particles being impacted is small, and the energy input is insufficient, which may lead to uneven mixing and poor powder refinement. Conversely, if the ball density is high, the number of grinding balls is large, and the powder is fully surrounded. The collision frequency between balls and between balls and the container wall is extremely high, resulting in strong impact and shearing effects on the powder. The energy input rate is high, which can more effectively pulverize particles and promote inter-element diffusion and chemical reactions. However, excessive collision friction generates too much heat, which may cause the powder to react with the container or grinding balls at high temperatures, introducing impurities.

[0027] For example, the ball-to-material ratio in solid-phase ball milling can be selected from any one of 5:1, 10:1, 15:1, 20:1, 28:1, 30:1, 32:1, 35:1 and 40:1, or other values ​​in the range of (5:1) to (40:1).

[0028] During the ball milling process, the grinding balls can be selected from at least one of the following: zirconia balls, alumina balls, zirconium silicate balls, silicon nitride balls, and tungsten carbide balls. The specific material can be chosen according to actual needs.

[0029] It should be noted that high rotation speed or long time will result in significant impact energy, which will accelerate the wear of the grinding balls and the container (such as zirconia), allowing a large amount of impurities to enter the powder and contaminate the precursor powder. If the rotation speed or time is too low, the expected particle size cannot be achieved, and ball milling will be required again. In the embodiments of this invention, the rotation speed and time of the solid-phase ball mill are reasonably adjusted according to the actual amount of material processed.

[0030] For example, the rotational speed of the solid-phase ball milling process can be selected from any one of 200 rpm, 300 rpm, 350 rpm, 400 rpm, 500 rpm and 600 rpm, or other values ​​within the range of 200 rpm to 600 rpm; the time can be selected from any one of 4 h, 6 h, 8 h, 10 h, 15 h and 20 h, or other values ​​within the range of 4 h to 20 h. And / or, the sintering temperature is 400℃-700℃ and the time is 8h-16h; in the embodiments of the present invention, the product after sintering is referred to as the first sulfide solid electrolyte intermediate.

[0031] It should be noted that the sintering process has the highest temperature to provide sufficient energy to drive the bulk diffusion of atoms / ions in the raw materials, overcome the energy barrier, and achieve grain growth and porosity elimination. It has the following characteristics: it allows powder particles to diffuse and fuse at high temperatures to form micron-sized grains, which is conducive to the elimination of porosity between particles, volume shrinkage, and a significant increase in density. It can reduce grain boundary resistance and prevent lithium dendrite penetration, thereby achieving material densification.

[0032] For example, the sintering temperature can be any one of 400°C, 450°C, 500°C, 550°C, 600°C, 650°C and 700°C, or other values ​​within the range of 400°C to 700°C.

[0033] And / or, the ball-to-material ratio of the liquid-phase ball milling treatment is (4:1)-(20:1), the liquid-to-material ratio is (1:1)-(5:1), the rotation speed is 200rpm-600rpm, and the ball milling time is 4h-20h; in the embodiments of the present invention, the product after liquid-phase ball milling treatment is referred to as the second sulfide solid electrolyte intermediate.

[0034] It should be noted that in liquid-phase ball milling, the liquid medium disperses the raw material powder. Through the high-energy impact and shearing of the grinding balls, particles of different components are continuously torn, broken, and have new surfaces formed, and then rapidly contact and diffuse in the liquid environment. The liquid acts as a "diluent" and a "transfer medium," preventing the broken particles from re-aggregating.

[0035] The ball milling solvent in this invention can act as a surfactant, which can inhibit the agglomeration between microparticles during liquid-phase ball milling, thereby reducing particle size and improving particle uniformity.

[0036] And / or, the tempering temperature is 160℃-250℃, and the time is 5min-20min.

[0037] It should be noted that the tempering process has the following characteristics: it allows elements to diffuse slowly between grains and grain boundaries, resulting in a more uniform composition and repairing lithium deficiency; it promotes a more ordered lattice arrangement, improving mechanical stability; it reduces the BET specific surface area of ​​the solid electrolyte, leading to a more concentrated particle size distribution and a significant increase in ionic conductivity. Furthermore, it helps repair grain boundary defects, reduce surface energy, and promote optimized grain arrangement, thus improving the electrochemical performance of solid-state batteries.

[0038] If the tempering temperature exceeds the initial sintering temperature, it is equivalent to a secondary sintering process. This can lead to abnormal grain growth, causing some large grains to engulf surrounding smaller grains, resulting in decreased material density, re-emergence of porosity, and deterioration of the grain boundary structure. The material becomes more porous and easier to be pierced by lithium dendrites; the decreased density significantly increases bulk and grain boundary resistance.

[0039] For example, the tempering temperature can be selected from any one of 160°C, 170°C, 180°C, 190°C, 220°C and 250°C, or other values ​​in the range of 160°C to 250°C.

[0040] In an optional embodiment, the liquid phase ball milling process is further followed by a drying process to remove the solvent; the drying temperature is 30°C-150°C. Preferably, the drying temperature is lower than the tempering temperature; It should be noted that the purpose of drying is primarily to physically remove the liquid solvent added during ball milling through evaporation, resulting in a dry, loose, and uniform material. Low-temperature treatment ensures that the solvent evaporates at a controllable rate, preventing the powder particles from being dispersed, agglomerated, or forming a hard shell due to violent vaporization.

[0041] If the drying temperature is too high, surface diffusion may occur prematurely between powder particles, forming strong "neck" connections, causing powder agglomeration and reduced activity. In addition, it may also lead to an increase in impurity phases in the solid electrolyte obtained after final tempering, a decrease in the purity of the main phase, and a significant reduction in total ionic conductivity.

[0042] For example, the drying temperature can be selected from any one of 30°C, 40°C, 50°C, 80°C, 100°C, 120°C and 150°C, or other values ​​in the range of 30°C to 150°C.

[0043] Preferably, the solvent used in the liquid-phase ball milling process is selected from at least one of benzene-based organic solvents, ether-based organic solvents, and ester-based organic solvents; Among them, benzene-based organic solvents are selected from at least one of toluene, p-xylene, and trimethylbenzene; The ether organic solvent is selected from at least one of dimethyl ether, dipropyl ether, dibutyl ether, methyl ethyl ether, and anisole; The ester organic solvent is selected from at least one of ethyl acetate, butyl butyrate, hexyl butyrate, and isobutyl isobutyrate.

[0044] It should be noted that when the present invention uses the above-mentioned ball milling solvent, the sulfide solid electrolyte raw material can present a stable suspension state in the solvent, rather than rapidly settling in the solvent. Moreover, the solvent has low reactivity with the sulfide solid electrolyte raw material, which can disperse the electrolyte raw material and promote the reduction of particle size during the pulverization process.

[0045] Thirdly, embodiments of the present invention provide a solid electrolyte membrane, including a solid electrolyte as described above or a solid electrolyte prepared by the preparation method described above.

[0046] Fourthly, embodiments of the present invention provide a method for preparing a solid electrolyte membrane as described above, comprising the following steps: A slurry is prepared by mixing solid electrolyte raw materials with an organic solvent in a mass ratio of (1:5) to (1:20). It should be noted that the preparation of the solid electrolyte membrane provided by the present invention belongs to the wet film formation process, and the viscosity of the slurry for wet film formation is less than 6000 mPa·s.

[0047] The slurry mixing method is selected from at least one of ball milling, ultrasonication and stirring, and the mixing time is 0.5h-12h; the specific mixing time can be reasonably adjusted according to the actual amount of material to be processed.

[0048] The slurry is coated onto the substrate to obtain a wet film with a thickness of 10μm-500μm; The substrate is BOPET (biaxially oriented polyester film).

[0049] It should be noted that the thickness setting of the wet film affects the thickness of the final solid electrolyte film. If the thickness is too thin, the slurry may not be able to completely cover the substrate, forming "film defects" or "pinholes". These defects will become short-circuit paths for ion transport and are also the preferred growth sites for lithium dendrites, which can easily lead to battery short circuits. It may also be extremely sensitive to the flatness of the substrate. Any tiny unevenness of the substrate will be magnified in the ultrathin film, resulting in uneven thickness.

[0050] If the thickness is too great, it poses a challenge to the leveling properties of the slurry. Thick slurries are more difficult to level using surface tension in a short time, easily leaving scraper marks and resulting in uneven thickness with "stripes." This can also cause drying stress cracking. During the drying process, the surface solvent evaporates first, forming a dense shell, which hinders the outward diffusion and evaporation of the internal solvent, generating enormous drying stress. When the stress exceeds the wet film strength, the film will crack, curl, or wrinkle. It can also cause a "skinning" effect, leading to rapid drying of the surface and the formation of a hard shell that hinders the evaporation of the internal solvent. During sintering, the decomposition and vaporization of the remaining binder inside can destroy the surface layer, causing fatal defects such as bubbling and delamination.

[0051] The prepared wet membrane was dried at a temperature of room temperature to 120°C for 0.5 h to 24 h to obtain a solid electrolyte membrane.

[0052] It should be noted that the drying process of wet membranes involves a mass transfer process. In this process, the diffusion path of the solvent from the inside to the surface reaches equilibrium with the evaporation rate, resulting in uniform shrinkage of the membrane as a whole and minimizing internal stress. If the thickness of the wet membrane is unreasonable, it will lead to an uncontrolled drying rate, either causing the outer surface to crack or the inside to remain wet for a long time, ultimately resulting in a loose microstructure and poor strength.

[0053] For example, the drying temperature of the wet membrane can be selected from any one of room temperature, 30°C, 40°C, 50°C, 80°C, 100°C, and 120°C, or other values ​​within the range of room temperature to 120°C; the drying time can be selected from any one of 0.5h, 2h, 3.5h, 5h, 10h, 15h, 20h, and 24h, or other values ​​within the range of 0.5h to 24h. Specifically, it can be reasonably adjusted according to the actual thickness of the wet membrane and the final required thickness of the solid electrolyte membrane.

[0054] In an optional embodiment, the preparation of the slurry further includes a binder, wherein the mass of the binder is 1%-10% of the mass of the solid electrolyte raw material; Preferably, the adhesive is selected from at least one of polyvinylidene fluoride and its copolymers, polyacrylates, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene oxide; It should be noted that solid electrolyte raw materials are loose powders and cannot be used directly. The binder, through its adhesiveness, forms strong "bonding bridges" between powder particles and between particles and the current collector (if needed), thus obtaining a green body with a certain mechanical strength and intact shape after tableting (e.g., cold pressing). Without a binder, the pressed tablets would be loose and brittle, like a sandcastle. The addition of a binder enhances the strength of the green body, ensuring the feasibility of the process. Furthermore, the binder completely decomposes and volatilizes during sintering, leaving pores. This provides space for particle rearrangement, diffusion, and densification in subsequent high-temperature stages. The type and content of the binder can regulate the initial pore structure of the green body, thereby indirectly affecting the final density and microstructure, and consequently influencing the mechanical and electrochemical properties of the electrolyte.

[0055] And / or, the organic solvent is selected from at least one of acetonitrile, tetrahydrofuran, and N-methylpyrrolidone; And / or, the coating method is selected from any one of blade coating, slot coating, spraying and spin coating, and the coating speed is 0.1m / min-10m / min; It should be noted that the coating method should be selected reasonably according to actual needs. If the coating speed is too slow, the slurry has more time to overflow and level under the doctor blade. The actual amount of slurry carried out may be slightly less than expected, but it is more likely to cause discontinuities, "orange peel" phenomenon, and horizontal streaks, resulting in low production efficiency. If the coating speed is too fast, the slurry is quickly dragged out, the hydrodynamic effect is enhanced, the leveling time is extremely short, and traces cannot be eliminated. The surface is rough after curing, which may cause the actual wet film thickness to be slightly greater than the theoretical gap value, leading to stability problems.

[0056] For example, the coating speed can be selected from any one of 0.1 m / min, 1.5 m / min, 2 m / min, 3 m / min, 5 m / min, 6 m / min, 8 m / min and 10 m / min, or other values ​​in the range of 0.1 m / min to 10 m / min.

[0057] And / or, the drying process is carried out in a vacuum environment or a protective atmosphere, wherein the protective atmosphere is selected from at least one of argon, helium, and nitrogen, to prevent the sulfide material from reacting with water or oxygen in the air.

[0058] Fifthly, embodiments of the present invention provide a solid-state battery, including a solid electrolyte as described above, a solid electrolyte prepared by the preparation method described above, a solid electrolyte membrane as described above, or a solid electrolyte membrane prepared by the preparation method described above.

[0059] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0060] Example 1 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method includes the following steps: S1: Weigh the following substances according to the chemical formula molar ratio: 91.9g Li2S, 63.585g LiCl and 111.135g P2S5, and mix them evenly under an argon atmosphere to obtain a mixture. The mixture is then subjected to solid-phase ball milling in a ball mill jar under an argon atmosphere. The solid-phase ball milling conditions are as follows: zirconia balls are used as the ball milling medium, the mass ratio of the mixture to the zirconia balls is 1:32, the ball milling speed is 300 rpm, and the ball milling time is 10 h to obtain the precursor powder.

[0061] S2: The ball-milled precursor powder obtained in step S1 is compacted in a square crucible under an argon atmosphere. The compacted crucible is then placed in a muffle furnace and sintered at 500°C under an argon atmosphere for 12 hours. After cooling, the product is designated as the first sulfide solid electrolyte intermediate with the chemical formula Li. 5.5 PS 4.5 Cl 1.5 .

[0062] S3: The first sulfide solid electrolyte intermediate obtained in step S2 is initially crushed in a mortar and then subjected to liquid-phase ball milling and grinding with a planetary mill to obtain powders with D10=410nm / D50=1434nm / D90=3700nm respectively; wherein, the ball milling medium is zirconium balls, the mass ratio of the first sulfide solid electrolyte intermediate to zirconium balls is 1:20, the ball milling solvent is p-xylene, the liquid-to-material ratio is 4:1, the ball milling speed is 300rpm, and the time is 4h; Then, the product was dried at 100°C for 10 hours to remove the ball milling solvent. The product was designated as the second sulfide solid electrolyte intermediate.

[0063] S4: Temper the second sulfide solid electrolyte intermediate obtained in step S3 at 200°C for 10 min to obtain the sulfide solid electrolyte; wherein, D10=812nm / D50=1567nm / D90=3789nm.

[0064] S5: The sulfide solid electrolyte material prepared in step S4 is mixed with the organic solvent NMP (N-methylpyrrolidone) and stirred to form a uniformly dispersed slurry; wherein the mass ratio of the sulfide solid electrolyte material to NMP is 1:10, and styrene-butadiene rubber binder at 5% of the mass of the sulfide solid electrolyte material is added during mixing, and the mixture is stirred for 5 hours to form a uniform and stable slurry.

[0065] S6: The slurry obtained in step S5 is uniformly coated onto a biaxially oriented polyester film (BOPET) substrate using a doctor blade; the coating speed is 10 m / min, and a wet film with a thickness of 20 μm is obtained.

[0066] S7: The wet membrane obtained in step S6 is dried together with the substrate at 120°C for 10 hours; the drying process can be carried out in argon gas; a sulfide solid electrolyte membrane is obtained.

[0067] Example 2 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S1: The mass ratio of the mixture to the zirconia balls is 1:30.

[0068] S2: Sintering treatment at 500℃ for 15 hours.

[0069] S3: Grinding and crushing with a planetary mill to obtain powders with D10=452nm / D50=1427nm / D90=3757nm respectively; The ball milling solvent was removed by drying at 120°C for 10 hours, and the product was designated as the second sulfide solid electrolyte intermediate.

[0070] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 160°C for 10 min to obtain a sulfide solid electrolyte; wherein, D10=824nm / D50=1521nm / D90=3790nm.

[0071] Example 3 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grinding and crushing with a planetary mill to obtain powders with D10=456nm / D50=1485nm / D90=3712nm respectively.

[0072] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 250°C for 10 min to obtain a sulfide solid electrolyte; wherein, D10=823nm / D50=1569nm / D90=3741nm.

[0073] Example 4 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grinding and crushing with a planetary mill to obtain powders with D10=472nm / D50=1467nm / D90=3745nm respectively.

[0074] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 200°C for 5 minutes to obtain a sulfide solid electrolyte; wherein, D10=863nm / D50=1578nm / D90=3703nm.

[0075] Example 5 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grinding and crushing with a planetary mill to obtain powders with D10=491nm / D50=1419nm / D90=3759nm respectively.

[0076] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 200°C for 20 min to obtain a sulfide solid electrolyte; wherein, D10=842nm / D50=1569nm / D90=3776nm.

[0077] Example 6 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grind and crush using a planetary mill to obtain powders with D10=203nm / D50=1050nm / D90=3010nm respectively.

[0078] S4: In the prepared sulfide solid electrolyte, D10=612nm / D50=1301nm / D90=3110nm.

[0079] Example 7 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5The preparation method is the same as in Example 1, except that: S3: Grinding and crushing with a planetary mill to obtain powders with D10=603nm / D50=2056nm / D90=4859nm respectively.

[0080] S4: In the prepared sulfide solid electrolyte, D10=932nm / D50=2145nm / D90=4857nm.

[0081] Example 8 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Br 1.5 The preparation method is the same as in Example 1, except that: S1: Weigh the following substances according to their chemical formula molar ratio: 91.9g Li2S, 111.135g P2S5 and 130.273g LiBr, and mix them evenly under an argon atmosphere to obtain a mixture.

[0082] S3: Grinding and crushing with a planetary mill to obtain powders with D10=430nm / D50=1402nm / D90=3789nm respectively.

[0083] S4: In the prepared sulfide solid electrolyte, D10=851nm / D50=1547nm / D90=3697nm.

[0084] Example 9 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 I 1.5 The preparation method is the same as in Example 1, except that: S1: Weigh the following substances according to their chemical formula molar ratio: 91.9g Li2S, 111.135g P2S5 and 200.775g LiI, and mix them evenly under an argon atmosphere to obtain a mixture.

[0085] S3: Grinding and crushing with a planetary mill to obtain powders with D10=420nm / D50=1431nm / D90=3791nm respectively.

[0086] S4: In the prepared sulfide solid electrolyte, D10=820nm / D50=1586nm / D90=3754nm.

[0087] S5: The mass ratio of sulfide solid electrolyte material to NMP is 1:15.

[0088] Example 10 This application provides a sulfide solid electrolyte membrane, wherein the chemical formula of the sulfide solid electrolyte is Li. 5.7 PS 4.5 Cl 1.3 The preparation method is the same as in Example 1, except that: S1: Weigh the following substances according to their chemical formula molar ratio: 96.495g Li2S, 55.107g LiCl and 111.135g P2S5, and mix them evenly under an argon atmosphere to obtain a mixture.

[0089] S3: Grinding and crushing with a planetary mill to obtain powders with D10=403nm / D50=1443nm / D90=3741nm respectively.

[0090] S4: In the prepared sulfide solid electrolyte, D10=813nm / D50=1569nm / D90=3716nm.

[0091] Comparative Example 1 This application provides a sulfide solid electrolyte membrane as a comparative example. The chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grind and crush using a planetary mill to obtain powders with D10=432nm / D50=1402nm / D90=3705nm respectively.

[0092] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 150°C for 10 min to obtain a sulfide solid electrolyte; wherein, D10=478nm / D50=2458nm / D90=3744nm.

[0093] Comparative Example 2 This application provides a sulfide solid electrolyte membrane as a comparative example. The chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grinding and crushing with a planetary mill to obtain powders with D10=426nm / D50=1475nm / D90=3781nm respectively.

[0094] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 300°C for 10 min to obtain a sulfide solid electrolyte; wherein, D10=1012nm / D50=3120nm / D90=5318nm.

[0095] Comparative Example 3 This application provides a sulfide solid electrolyte membrane as a comparative example. The chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grinding and crushing with a planetary mill to obtain powders with D10=456nm / D50=1489nm / D90=3758nm respectively.

[0096] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 200°C for 30 min to obtain a sulfide solid electrolyte; wherein, D10=965nm / D50=2489nm / D90=3778nm.

[0097] Comparative Example 4 This application provides a sulfide solid electrolyte membrane as a comparative example. The chemical formula of the sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 The preparation method is the same as in Example 1, except that: S3: Grind and crush using a planetary mill to obtain powders with D10=454nm / D50=1476nm / D90=3754nm respectively.

[0098] S4: The second solid electrolyte intermediate obtained in step S3 is tempered at 200°C for 2 minutes to obtain a sulfide solid electrolyte; wherein, D10=452nm / D50=1475nm / D90=3771nm.

[0099] Test Example 1 This test example tested the ionic conductivity (abbreviated as post-milling ionic conductivity) of the materials after S3 liquid-phase ball milling treatment and the ionic conductivity (abbreviated as post-tempering ionic conductivity) of the materials after S4 tempering treatment in Examples 1-10 and Comparative Examples 1-4, respectively. The particle size (D10, D50) and specific surface area (BET) of the materials obtained by S3 and S4 were summarized, and the relevant data are summarized in Table 1.

[0100] The particle size analysis equipment was a Malvern 3000 laser particle size analyzer, and the test method was in accordance with GB / T19077-2016. The particle size distribution Df = (D90-D10) / D50. In Table 1, Df1 is the particle size distribution before tempering, and Df2 is the particle size distribution after tempering.

[0101] The surface area testing equipment was a McMeter test instrument, and the test method referred to GB / T19587-2017.

[0102] The ionic conductivity testing equipment is SP-200. The testing method is as follows: Weigh 0.11g-0.14g of powder and place it in a mold with a diameter of 10mm. The area is S=0.5×0.5×π. The pressure is 300MPa. Hold the pressure for 10min-15min. Use the Donghua Electrochemical Workstation to test the impedance and obtain the impedance data (R / Ω). Then, take out the sheet and test the thickness (H / mm). According to the formula, ionic conductivity = H / S / R.

[0103] Table 1 Data Summary

[0104] As can be seen from the data in Table 1, by comparing Examples 1-10 and Comparative Examples 1-2, the tempering temperature was too low and could not achieve the corresponding effect, while the tempering temperature was too high and caused abnormal particle growth, and the ion conductance was severely attenuated. By comparing Examples 1-10 and Comparative Examples 3-4, the tempering holding time was too long and caused abnormal particle growth and severe ion conductance attenuation, while the tempering holding temperature was too short and could not achieve the improvement effect.

[0105] Test Example 2 This test example uses the products prepared in Examples 1, 2, 7-10 and Comparative Examples 1 and 4 as examples to test the tap density and average capacity decay per cycle before tempering, and the tap density and average capacity decay per cycle after tempering, and the results are summarized in Table 2.

[0106] Table 2 Performance Data

[0107] As can be seen from the data in Table 2, Examples 1-10 show that the tap density is improved after tempering. This is due to the rounded particle morphology and reduced size difference after tempering. The rounded morphology and excellent ionic conductivity lead to a decrease in the cycle capacity decay rate. Comparing Examples 1 and 4, it can be seen that tempering temperature and time exceeding the patent limit cannot achieve excellent performance improvement.

[0108] Test Example 3 This test example uses Example 1 as an example. Morphological analysis was performed on the second sulfide solid electrolyte intermediate prepared before tempering and the sulfide solid electrolyte prepared after tempering. The relevant results are as follows: The test results of the sulfide solid electrolyte prepared after tempering are shown in […]. Figure 1 The test results of the second sulfide solid electrolyte intermediate prepared before tempering are shown in [reference needed]. Figure 2 .

[0109] Combination Figure 1 and Figure 2It can be seen that the sulfide solid electrolyte obtained after tempering has a regular and rounded morphology, while the intermediate second sulfide solid electrolyte obtained before tempering has an irregular particle morphology and more surface defects.

[0110] In summary, the solid electrolyte provided in this invention features small particle size, narrow particle size distribution, small specific surface area, and high ionic conductivity. The tempering treatment during solid electrolyte preparation effectively solves the common problem of decreased ionic conductivity in sulfide solid electrolytes as particle size decreases. Specifically, after tempering, the BET specific surface area of ​​the solid electrolyte decreases, the particle size distribution becomes more concentrated, and the ionic conductivity is significantly improved. The tempering treatment of the solid electrolyte in this invention helps repair grain boundary defects, reduce surface energy, and promote optimized grain arrangement, which is beneficial for improving the electrochemical performance of solid-state batteries.

[0111] 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 solid electrolyte, characterized in that, The chemical formula of the solid electrolyte is Li 6-x PS 5-x Q 1+x Where 0 ≤ X ≤ 0.6, and Q is selected from at least one of Cl, Br, and I; The solid electrolyte has an ionic conductivity ≥3 mS / cm; the particle size distribution Df satisfies: 0.9≤Df=(D90-D10) / D50≤2.

0.

2. The solid electrolyte according to claim 1, characterized in that, The solid electrolyte has a D10 of 600nm-1000nm, preferably 700nm-900nm; And / or, D50 is 1000nm-3000nm, preferably 1500nm-2500nm; And / or, D90 is 3000nm-5000nm, preferably 3500nm-4500nm; And / or, the specific surface area of ​​the solid is 2m². 2 / g-10m 2 / g, preferably 6m 2 / g-8m 2 / g; And / or, the ionic conductivity of the solid electrolyte is 3 mS / cm-18 mS / cm.

3. A method for preparing a solid electrolyte as described in any one of claims 1-2, characterized in that, Includes the following steps: Solid electrolyte raw materials are mixed in proportion and subjected to solid-phase ball milling to obtain precursor powder. The precursor powder was sintered to obtain a solid electrolyte intermediate. The solid electrolyte intermediate was subjected to liquid-phase ball milling and then tempering to obtain a solid electrolyte. Among them, the temperature of sintering treatment is greater than the temperature of tempering treatment.

4. The preparation method according to claim 3, characterized in that, The solid electrolyte raw materials include lithium source, phosphorus source, sulfur source and halogen source in a molar ratio of (5.4-6):1:(4.4-5):(1-1.6); And / or, the average particle size of the solid electrolyte raw material is independently 0.5μm-10μm, preferably 0.5μm-8μm; The lithium source is selected from at least one of lithium sulfide, lithium oxide and lithium carbonate; The phosphorus source is selected from at least one of phosphorus pentasulfide and phosphorus trisulfide; The sulfur source is selected from at least one of lithium sulfide, phosphorus pentasulfide and phosphorus trisulfide; The halogen source is selected from at least one of lithium chloride, lithium bromide and lithium iodide.

5. The preparation method according to claim 3, characterized in that, The ball-to-material ratio for the solid-phase ball milling process is (5:1)-(40:1), the rotation speed is 200rpm-600rpm, and the time is 4h-20h. And / or, the sintering treatment is performed at a temperature of 400℃-700℃ for a time of 8h-16h; And / or, the ball-to-material ratio of the liquid-phase ball milling process is (4:1)-(20:1), the liquid-to-material ratio is (1:1)-(5:1), the rotation speed is 200rpm-600rpm, and the ball milling time is 4h-20h; And / or, the tempering treatment is performed at a temperature of 160℃-250℃ for a time of 5min-20min.

6. The preparation method according to claim 5, characterized in that, The liquid phase ball milling process also includes a drying process to remove the solvent; the drying process is performed at a temperature of 30℃-150℃. Preferably, the drying temperature is lower than the tempering temperature; Preferably, the solvent used in the liquid-phase ball milling process is selected from at least one of benzene-based organic solvents, ether-based organic solvents, and ester-based organic solvents; The benzene-based organic solvent is selected from at least one of toluene, p-xylene, and trimethylbenzene; The ether organic solvent is selected from at least one of dimethyl ether, dipropyl ether, dibutyl ether, methyl ethyl ether, and anisole; The ester organic solvent is selected from at least one of ethyl acetate, butyl butyrate, hexyl butyrate, and isobutyl isobutyrate.

7. A solid electrolyte membrane, characterized in that, Includes the solid electrolyte as described in any one of claims 1-2 or the solid electrolyte prepared by the preparation method as described in any one of claims 3-6.

8. A method for preparing a solid electrolyte membrane as described in claim 7, characterized in that, Includes the following steps: A slurry is prepared by mixing solid electrolyte raw materials with an organic solvent in a mass ratio of (1:5) to (1:20). The slurry is coated onto a substrate to obtain a wet film with a thickness of 10μm-500μm; The prepared wet membrane was dried at a temperature of room temperature to 120°C for 0.5 h to 24 h to obtain a solid electrolyte membrane.

9. The preparation method according to claim 8, characterized in that, The preparation of the slurry also includes a binder, wherein the mass of the binder is 1%-10% of the mass of the solid electrolyte raw material; Preferably, the adhesive is selected from at least one of polyvinylidene fluoride and its copolymers, polyacrylates, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, and polyethylene oxide; Preferably, the slurry mixing method is selected from at least one of ball milling, ultrasonication and stirring, and the mixing time is 0.5h-12h; And / or, the organic solvent is selected from at least one of acetonitrile, tetrahydrofuran, and N-methylpyrrolidone; And / or, the coating method is selected from any one of blade coating, slot coating, spraying and spin coating, and the coating speed is 0.1m / min-10m / min; And / or, the drying process is carried out in a vacuum environment or a protective atmosphere, wherein the protective atmosphere is selected from at least one of argon, helium and nitrogen.

10. A solid-state battery, characterized in that, This includes the solid electrolyte as described in any one of claims 1-2, the solid electrolyte prepared by the preparation method as described in any one of claims 3-6, the solid electrolyte membrane as described in claim 7, or the solid electrolyte membrane prepared by the preparation method as described in any one of claims 8-9.

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