Sulfide solid electrolyte and preparation method thereof

Abstract

The invention discloses a preparation method of a sulfide solid electrolyte, and relates to the field of solid-state batteries, the preparation method comprises the following steps: preparing Li2S-coated LiCl core-shell nanoparticles, and carrying out airflow collision grinding on the Li2S-coated LiCl core-shell nanoparticles and P2S5 nanopowder to obtain composite powder; the composite powder is placed in a reaction furnace for heating deposition, then heating crystallization is carried out, and Li6PS5Cl nanoparticles are obtained; the Li6PS5Cl nanoparticles are placed in a ball milling tank to be treated, then annealing treatment is conducted, and the sulfide solid electrolyte is obtained after treatment is completed. Through combination of the core-shell structure precursor and the vapor deposition technology, the core contradiction that nanocrystallization and high ionic conductivity are difficult to consider at the same time in the sulfide solid electrolyte field is effectively solved, and the problems of interface contact defects caused by micron-sized particles and crystal defects caused by mechanical refinement in a traditional process are effectively solved; the problem is solved through construction of Li2S-coated LiCl core-shell nanoparticles and activation treatment of airflow on collision and grinding.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, and more particularly to a sulfide solid electrolyte and its preparation method. Background Technology

[0002] All-solid-state lithium batteries are considered key to the next generation of energy storage technology due to their high safety and high energy density. The core of their performance lies in the solid electrolyte. Among the many solid electrolytes, sulfide solid electrolytes have attracted much attention due to their extremely high ionic conductivity and good mechanical ductility.

[0003] The sulfide electrolyte particles prepared by traditional solid-state or liquid-phase ball milling methods are typically in the micrometer range. When micrometer-sized sulfide electrolyte particles come into contact with micrometer-sized cathode material particles, the small physical contact area leads to poor interfacial contact and numerous internal pores during the composite process, making it difficult to form a continuous ionic conductive network. If the sulfide electrolyte particles are further refined to the submicrometer or nanometer scale through subsequent mechanical crushing, a large number of crystal defects and interfacial contamination will inevitably be introduced, resulting in a significant decrease in ionic conductivity. In addition, existing synthesis processes generally suffer from lengthy procedures and high energy consumption, such as long-term high-temperature sintering or ball milling for tens of hours, which seriously restricts production efficiency and cost control.

[0004] Therefore, a sulfide solid electrolyte and its preparation method are proposed to solve the problems mentioned above, such as the difficulty in forming a continuous ionic conductive network and the significant decay of ionic conductivity. Summary of the Invention

[0005] The purpose of this invention is to provide a sulfide solid electrolyte and its preparation method, which solves the problems of difficulty in forming a continuous ionic conductive network and significant decay of ionic conductivity.

[0006] To achieve this objective, the present invention adopts the following technical solution: A method for preparing a sulfide solid electrolyte, the method comprising the following steps: Step S1: Prepare Li2S@LiCl core-shell nanoparticles and perform airflow collision milling on them with P2S5 nanoparticles to obtain composite powder; Step S2: The composite powder is placed in a reactor for heating and deposition, and then heated and crystallized to obtain Li6PS5Cl nanoparticles. Step S3: After treating the Li6PS5Cl nanoparticles in a ball mill jar, they are then annealed to obtain a sulfide solid electrolyte.

[0007] Step S1 specifically includes the following steps: Step S11: Disperse and mix Li2S@LiCl core-shell nanoparticles with P2S5 nanoparticles to form a dry mixture; Step S12: Place the dry mixture in the protective atmosphere of the airflow impact mill for impact treatment, and obtain composite powder after the treatment is completed.

[0008] In step S11, the D50 of the P2S5 nanopowder is <1μm, and the dispersion and mixing time is 30-60min and the rotation speed is 60-80rpm. In step S12, the working pressure of the collision treatment is 0.5-0.8 MPa, and the treatment time is 5-15 min.

[0009] The Li2S@LiCl core-shell nanoparticles were obtained according to the following steps: Step S111: In a protective atmosphere, disperse Li2S powder in anhydrous acetonitrile a to form a suspension; Step S112: Dissolve LiCl in anhydrous acetonitrile b to form a clear solution; Step S113: Add the clear liquid dropwise to the suspension and stir to obtain a slurry. Then, vacuum dry the slurry. After drying, obtain Li2S@LiCl core-shell nanoparticles.

[0010] In step S111, the particle size of the Li2S powder is 100-200 nm, and the mass ratio of the Li2S powder to anhydrous acetonitrile a is 1:(1.8-2.2). In step S112, the mass ratio of LiCl to anhydrous acetonitrile is (0.3-0.5):1; In step S113, the drop rate of the clarified liquid is 1-2 drops / s, the stirring time is 1-3 hours and the rotation speed is 300-500 rpm, and the vacuum drying temperature is 50℃ and the vacuum degree is -0.1 MPa.

[0011] Step S2 specifically includes the following steps: Step S21: Spread the composite powder in a container, then send the container into the reaction tube of the reactor. The reactor is then heated to the first temperature to heat and deposit the composite powder. After the heating and deposition are completed, an amorphous precursor is obtained. Step S22: After heating the reactor to the second temperature, the amorphous precursor is heated and crystallized. After the heating and crystallization is completed, it is cooled to room temperature to obtain Li6PS5Cl nanoparticles.

[0012] In step S21, the first temperature is 320-350℃, the heating rate is 8-12℃ / min, and the holding time is 30-60min; In step S22, the second temperature is 380-420℃, the heating rate is 3-6℃ / min, the holding time is 60-90min, and the Li6PS5Cl nanoparticles have an aluminosilicate crystal structure.

[0013] Step S3 specifically includes the following steps: Step S31: Feed the Li6PS5Cl nanoparticles into a ball milling jar containing grinding beads, and ball mill at a speed of 300-500 rpm for 30-60 min to obtain primary powder; wherein, the grinding beads are zirconia beads, the size of the grinding beads is 3-6 mm, and the mass ratio of grinding beads to Li6PS5Cl nanoparticles is (18-22):1. Step S32: Place the primary powder in a vacuum annealing furnace, evacuate the furnace to -0.1MPa, fill it with protective gas, and then anneal the primary powder at an annealing temperature of 200-300℃ for 2-3 minutes, and cool the primary powder to below 50℃ within 1-2 minutes. Step S33: Repeat step S32 to anneal the primary powder 5-10 times to obtain a solid electrolyte.

[0014] A sulfide solid electrolyte, wherein the sulfide solid electrolyte is prepared by the method for preparing sulfide solid electrolyte as described above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a sulfide solid electrolyte and its preparation method. By combining a core-shell structured precursor with vapor deposition technology, it effectively solves the core contradiction in the field of sulfide solid electrolytes: the difficulty of simultaneously achieving nanoscale structure and high ionic conductivity. Furthermore, the interfacial contact defects caused by micron-sized particles and the crystal defects caused by mechanical refinement in traditional processes are resolved through the construction of Li2S@LiCl core-shell nanoparticles and activation treatment by airflow impact milling. This not only achieves uniform molecular-level mixing of reactants at the nanoscale but also exposes a highly active interface through the controllable exfoliation of the LiCl shell. Subsequent vapor deposition further enhances the P2S5 content. The precursor reacts uniformly with the surface of the core-shell particles in a solid-gas reaction, forming a homogeneous amorphous precursor at low temperature, thus avoiding grain coarsening caused by high-temperature sintering. At the same time, Li6PS5Cl nanocrystals with an argentite-type crystal structure are prepared through the crystallization process, which not only maintains the interfacial advantages of nanomaterials but also obtains a complete crystal framework. Finally, the crystal defects are repaired and the stability is controlled at the nanoscale through cyclic annealing, so that the solid electrolyte formed can achieve the extreme value of ionic conductivity while maintaining the nanomorphic morphology. This represents a dual breakthrough in the microstructure and macroscopic performance of sulfide solid electrolytes. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0018] Figure 1 This is a flowchart of the preparation method in this invention. Detailed Implementation

[0019] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0021] Example 1: Please see Figure 1 This embodiment describes a method for preparing a sulfide solid electrolyte, the method comprising the following steps: Step S1: Prepare Li2S@LiCl core-shell nanoparticles and perform airflow collision milling on them with P2S5 (phosphorus pentasulfide) nanoparticles to obtain composite powder; Step S2: The composite powder is placed in a reaction furnace for heating and deposition, and then heated and crystallized to obtain Li6PS5Cl (lithium phosphorus sulfur chloride) nanoparticles. Step S3: After treating the Li6PS5Cl nanoparticles in a ball mill jar, they are then annealed to obtain a sulfide solid electrolyte.

[0022] Specifically, in step S1, Li2S@LiCl core-shell nanoparticles are prepared and then subjected to airflow collision milling with P2S5 nanoparticles to obtain composite powder. Step S1 specifically includes the following steps: Step S11: Disperse and mix Li2S@LiCl core-shell nanoparticles with P2S5 nanoparticles to form a dry mixture; In step S11, the D50 of the P2S5 nanopowder is <1μm, and the dispersion and mixing time is 30-60min and the rotation speed is 60-80rpm; preferably, the dispersion and mixing time is 45min and the rotation speed is 70rpm; it is understood that the methods and techniques for obtaining P2S5 nanopowder are well known to those skilled in the art, and will not be described in this embodiment.

[0023] It should be noted that by stirring at low speed for 30-60 minutes and 60-80 rpm, the two powders can achieve a macroscopic and roughly uniform distribution, which ensures that each batch of material fed in during the subsequent airflow impact mill has a basically consistent initial ratio, thereby ensuring the uniformity of the chemical composition of the composite powder.

[0024] Step S12: Place the dry mixture in the protective atmosphere of the airflow impact mill for impact treatment, and obtain composite powder after the treatment is completed.

[0025] In step S12, the working pressure of the collision treatment is 0.5-0.8 MPa, and the treatment time is 5-15 min; preferably, the working pressure of the collision treatment is 0.65 MPa, and the treatment time is 10 min; the process of placing the dry mixture in an airflow collision mill is well known to those skilled in the art, and will not be described in this embodiment.

[0026] It should be noted that, under the action of airflow impact milling, the two types of particles in the composite powder collide and impact each other. During this process, because the LiCl shell of the Li2S@LiCl core-shell nanoparticles is more brittle than the Li2S (lithium sulfide) core, the impact force will preferentially cause the LiCl to break and peel off, thereby reducing the shell thickness and exposing the fresh surface of the core Li2S. At the same time, the P2S5 particles break under the impact, reducing their particle size. The impact force will also pin and weld the P2S5 fragments to the surface of the activated Li2S@LiCl core-shell nanoparticles. In addition, the high stress in this process will also cause a large number of defects such as dislocations and vacancies to be generated in the lattice of the near-surface region of the Li2S@LiCl core-shell nanoparticles. These defects will also provide highly active sites for subsequent processing.

[0027] It should also be noted that after high-speed collision, the shell of the Li2S@LiCl core-shell nanoparticles is uniformly thinned, and the Li2S core is exposed. The P2S5 particles are also refined and tightly embedded in the surface and depressions of the Li2S@LiCl core-shell nanoparticles, maximizing the contact area between the particles and improving the surface energy.

[0028] It is known that the airflow impact milling process has a shorter processing time, and this method is more efficient than the traditional ball milling process.

[0029] The Li2S@LiCl core-shell nanoparticles were obtained according to the following steps: Step S111: In a protective atmosphere, disperse Li2S powder in anhydrous acetonitrile a to form a suspension; In step S111, the particle size of the Li2S powder is 100-200 nm, and the mass ratio of the Li2S powder to anhydrous acetonitrile a is 1:(1.8-2.2); preferably, the particle size of the Li2S powder is 150 nm, and the mass ratio of the Li2S powder to anhydrous acetonitrile a is 1:2. Step S112: Dissolve LiCl (lithium chloride) in anhydrous acetonitrile b to form a clear solution; In step S112, the mass ratio of LiCl to anhydrous acetonitrile is (0.3-0.5):1; preferably, the mass ratio of LiCl to anhydrous acetonitrile is 0.4:1. It is known that acetonitrile can effectively dissolve LiCl to form a homogeneous clear liquid, which facilitates its full contact with the Li2S surface. Furthermore, acetonitrile does not react chemically with Li2S, thus maintaining the morphology and structural integrity of Li2S particles and helping LiCl molecules adsorb on the Li2S surface, promoting heterogeneous nucleation. In addition, acetonitrile has a low boiling point and can be effectively removed in subsequent processing, avoiding residues.

[0030] It is understood that the methods and techniques for obtaining LiCl and Li2S powders are well known to those skilled in the art, and will not be described in this embodiment.

[0031] Step S113: Add the clear liquid dropwise to the suspension and stir to obtain a slurry. Then, vacuum dry the slurry. After drying, obtain Li2S@LiCl core-shell nanoparticles.

[0032] In step S113, the drip rate of the clarified liquid is 1-2 drops / s, the stirring time is 1-3 hours and the rotation speed is 300-500 rpm, the vacuum drying temperature is 40-60℃ and the vacuum degree is (-0.09)-(-0.15) MPa; preferably, the drip rate of the clarified liquid is 1 drop / s, the stirring time is 2 hours and the rotation speed is 400 rpm, the vacuum drying temperature is 50℃ and the vacuum degree is -0.1 MPa; it is understood that the vacuum drying method is well known to those skilled in the art and will not be described in this embodiment.

[0033] It should be noted that when the clarified liquid is added to the suspension, a large number of solid-liquid interfaces will exist. When LiCl molecules diffuse to the surface of Li2S particles, due to the polar forces on the surface of Li2S crystals and the tendency to reduce surface energy, LiCl molecules will be adsorbed on the Li2S surface, forming an adsorption layer. The dropping acceleration rate of 1 drop / s can prevent the local concentration from being too high, which would lead to homogeneous nucleation of LiCl and the generation of independent LiCl crystals. This ensures that nucleation occurs preferentially on the Li2S surface. The continuous stirring for 2 hours provides sufficient time for molecular diffusion and surface adsorption, making the adsorption process tend to be balanced and uniform. Subsequently, during the vacuum drying process of the slurry, acetonitrile molecules escape rapidly, and LiCl in the slurry quickly reaches supersaturation. However, since the adsorption layer already existing on the Li2S surface serves as a ready-made heterogeneous nucleation site, the supersaturated LiCl is forced to continue to deposit and grow on the Li2S surface. Finally, LiCl completely encapsulates the Li2S core in the form of nanocrystals, forming a core-shell structure.

[0034] It should also be noted that in step S113, by stirring, LiCl molecules diffuse to the surface of Li2S particles and undergo physical / chemical adsorption, forming an adsorption layer of one or several molecular layers thick on the Li2S surface. In the subsequent vacuum drying, LiCl grows epitaxially or accumulates disorderly on the adsorption layer, and the shell layer gradually thickens to form a shell structure, so that each Li2S particle is covered with a dense and continuous amorphous LiCl shell layer, thereby forming Li2S@LiCl core-shell nanoparticles.

[0035] It is known that by dissolving LiCl, the precise modification of Li2S by LiCl molecules is achieved, ensuring that each Li2S particle can obtain an equal amount of uniformly distributed LiCl for reaction within its closest distance during subsequent vacuum drying. This completely eliminates the situation where impurities such as Li3PS4 (lithium trithiophosphate) or residual Li2S are generated due to insufficient or excessive local LiCl. In addition, the size of the final Li2S@LiCl core-shell nanoparticles is limited by the original size of the Li2S particles, thus avoiding the problem of excessively large particle size from the source.

[0036] It is worth noting that under vacuum drying, acetonitrile evaporates very quickly, and LiCl molecules are rapidly fixed from the supersaturated solution onto the Li2S surface. LiCl molecules do not have enough time and energy for long-range migration and orderly arrangement to form regular crystals. Therefore, they exist in an amorphous form with long-range disorder and short-range order. The amorphous LiCl shell has higher activity, which is beneficial to subsequent reactions.

[0037] Specifically, in step S2, the composite powder is placed in a reactor for heating and deposition, and then heated and crystallized to obtain Li6PS5Cl nanoparticles. Step S2 specifically includes the following steps: Step S21: Spread the composite powder in a container, then send the container into the reaction tube of the reactor. The reactor is then heated to the first temperature to heat and deposit the composite powder. After the heating and deposition are completed, an amorphous precursor is obtained. It is understood that the process of processing composite powders in a reactor is well known to those skilled in the art, and will not be described further in this embodiment.

[0038] In step S21, the first temperature is 320-350℃, the heating rate is 8-12℃ / min, and the holding time is 30-60min; preferably, the first temperature is 330℃, the heating rate is 10℃ / min, and the holding time is 45min. Understandably, the uniform LiCl shell of the Li2S@LiCl core-shell nanoparticles ensures a continuous supply of LiCl, and the exposed Li2S core and embedded P2S5 provide a large number of uniform and highly active reaction sites for subsequent processing.

[0039] It should be noted that after the composite powder is heated to the first temperature, because this temperature is much higher than the sublimation point of P2S5 (300℃) and insufficient to trigger large-scale crystallization, the P2S5 solid molecules gain enough kinetic energy to overcome the lattice energy and directly sublimate into P4S. 10Gaseous molecular clusters such as tetraphosphorus decasulfide diffuse throughout the powder layer under the influence of an inert gas flow and a concentration gradient, and adsorb onto the surface of the activated core-shell composite particles. Subsequently, the adsorbed P2S5 gas reacts with the outermost Li2S and LiCl of the particles in a solid-gas interface reaction, initially generating an amorphous compound of lithium-phosphorus-sulfur-chlorine. The selection of the first temperature and the holding temperature are to allow P2S5 to react with all the core-shell particles in a controlled and sufficient manner, rather than being consumed too quickly in a localized area.

[0040] It is known that in the above process, P2S5 in the composite powder is transformed from solid to gaseous phase. The gaseous P2S5 molecules are adsorbed and reacted on the surface of Li2S@LiCl core-shell nanoparticles to form an amorphous Li-PS-Cl precursor. In this process, the nanomorphic morphology of Li2S@LiCl core-shell nanoparticles is maintained, but the internal structure becomes long-range disorder.

[0041] It should also be noted that the first temperature can effectively allow P2S5 to sublimate continuously, ensuring the continuous progress of the reaction. If the first temperature is too high, it will cause a large amount of P2S5 to vaporize instantly, the reaction will be too violent, and it will easily cause uneven product composition, coarse grains or molten state, thus affecting the subsequent reaction.

[0042] It is important to emphasize that sublimation transforms P2S5 directly from a solid state to a gaseous state. The gaseous molecules of P2S5 have extremely high permeability and fluidity, allowing them to diffuse into every pore of the entire composite powder layer without dead angles, and to be uniformly adsorbed on the surface of each Li2S@LiCl core-shell particle, achieving molecular-level mixing in three-dimensional space. In addition, the initial temperature is lower than the temperature of large-scale crystallization, and the reaction takes place on the solid surface, effectively inhibiting premature grain growth and coarsening, and protecting the original nano-morphology. Compared with direct high-temperature sintering, this gas-solid reaction is more mild and controllable, avoiding local melting or component segregation caused by violent exothermic reaction.

[0043] In step S22, the second temperature is 380-420℃, the heating rate is 3-6℃ / min, and the holding time is 60-90min; preferably, the second temperature is 400℃, the heating rate is 5℃ / min, and the holding time is 70min.

[0044] Step S22: After heating the reactor to the second temperature, the amorphous precursor is heated and crystallized. After the heating and crystallization is completed, it is cooled to room temperature to obtain Li6PS5Cl nanoparticles.

[0045] It should be noted that when the temperature rises to the second temperature, the amorphous precursor obtains sufficient energy, and the atoms and ions gain higher migration ability. At the defects and compositional fluctuations of the amorphous precursor, tiny argentite phase nuclei will spontaneously form. After the nuclei are formed, the surrounding atoms / ions will be added to the nuclei through bulk diffusion or grain boundary diffusion according to the arrangement of the argentite lattice, so that the crystal grows.

[0046] It should also be noted that at the second temperature, a large number of nanoscale argentite phase nuclei appear inside the amorphous Li-PS-Cl precursor and gradually grow, transforming from long-range disorder to long-range order. During this process, the amorphous phase of the Li-PS-Cl precursor disappears and gradually transforms into Li6PS5Cl powder with a cubic crystal system and nanocrystalline structure.

[0047] It is known that, due to the high uniformity of the precursor, the crystallized argentite-type Li6PS5Cl nanoparticles provide an efficient migration channel for lithium ions, thereby achieving high intrinsic ionic conductivity, while the primary nanoparticles are retained.

[0048] Specifically, in step S3, Li6PS5Cl nanoparticles are placed in a ball mill jar for treatment, followed by annealing. After the treatment is completed, a sulfide solid electrolyte is obtained.

[0049] Step S3 specifically includes the following steps: Step S31: Feed Li6PS5Cl nanoparticles into a ball milling jar containing grinding balls, and ball mill at 300-500 rpm for 30-60 min to obtain primary powder; wherein the grinding balls are zirconia beads, the size of the grinding balls is 3-6 mm, and the mass ratio of grinding balls to Li6PS5Cl nanoparticles is (18-22):1; preferably, feed Li6PS5Cl nanoparticles into a ball milling jar containing grinding balls, and ball mill at 400 rpm for 45 min to obtain primary powder; wherein the grinding balls are zirconia beads, the size of the grinding balls is 5 mm, and the mass ratio of grinding balls to Li6PS5Cl nanoparticles is 20:1; It should be noted that by ball milling Li6PS5Cl nanoparticles, the van der Waals forces and electrostatic attraction between nanoparticles can be overcome, breaking up soft aggregates that are physically gathered together into a state closer to primary particles. During the ball milling process, the particle contact points are subjected to high pressure at the moment of collision, causing the atoms on the particle surface to rearrange and produce a fresh surface. This pressure causes the particles to undergo plastic deformation and interatomic bonding at the contact points, thereby forming a solid neck connection between the particles.

[0050] It is known that ball milling breaks down the soft aggregates of Li6PS5Cl nanoparticles rather than crushing them. After the soft aggregates are broken down, their fluidity is enhanced, and the neck connections between particles form a more stable, open chain or network structure.

[0051] Understandably, Li6PS5Cl nanoparticles are prone to agglomeration due to their high specific surface area. If solid electrolytes are formed, they will leave a large number of pores, increasing ion transport impedance. However, the neck connections between particles and their high fluidity can more effectively fill the gaps during subsequent forming, forming a highly dense, low-porosity solid electrolyte, thereby reducing interfacial impedance between particles and improving macroscopic ionic conductivity. Through the neck connections between particles, a three-dimensional physical contact network can be formed in the powder. During the subsequent solid electrolyte forming, the three-dimensional physical contact network can guide the particles to rearrange and combine more effectively to improve density, transforming point contacts between particles into surface contacts, and reducing the transport impedance of lithium ions at the particle interface.

[0052] Step S32: Place the primary powder in a vacuum annealing furnace, evacuate the furnace to -0.1 MPa, fill it with a protective gas, and then anneal the primary powder at an annealing temperature of 200-300°C for 2-3 minutes, and cool the primary powder to below 50°C within 1-2 minutes; preferably, place the primary powder in a vacuum annealing furnace, evacuate the furnace to -0.1 MPa, fill it with a protective gas, and then anneal the primary powder at an annealing temperature of 250°C for 2 minutes, and cool the primary powder to below 50°C within 1 minute; Step S33: Repeat step S32 to anneal the primary powder 5-10 times to obtain a solid electrolyte; repeat step S32 to anneal the primary powder 8 times to obtain a solid electrolyte.

[0053] It should be noted that by annealing the primary powder, energy is provided to the primary powder, which enables point defects inside the crystal to be annihilated through short-range diffusion, allowing dislocations to slip or recombine, thereby reducing lattice distortion energy and achieving defect repair to improve the integrity of the crystal. In the subsequent cooling process, long-range diffusion of atoms is suppressed, avoiding grain boundary migration and grain merging and growth.

[0054] It should also be noted that by performing cyclic annealing, the primary powder undergoes multiple heating-cooling cycles, which reduces the defect density inside the crystal, makes the crystal lattice more complete, and prevents the grain size from increasing, thereby improving the crystallinity of the obtained solid electrolyte.

[0055] It is known that the solid electrolyte obtained by the above preparation method is a nanoparticle. When combined with the positive electrode material, it has a large contact area, which can effectively fill the pores and form a continuous and dense ion-conducting network. In addition, in the preparation method, nanocrystals are directly synthesized by vapor deposition, and defects are repaired by cyclic annealing, which protects and optimizes the crystal structure. This ensures that the ion conductivity not only does not decrease but is maximized, avoiding the need for high-intensity mechanical crushing to refine the particles. Furthermore, the steps of airflow impact milling and vapor deposition shorten the process cycle and improve efficiency compared with traditional ball milling and long-term sintering.

[0056] Understandably, when the primary powder is rapidly heated to a first temperature—enough to activate ion migration but far below the threshold for rapid grain growth—the point defects and dislocations introduced by the previous process within the primary powder crystal gain the energy required for short-range migration and recombination. During this brief heating window of 2-3 minutes, atoms or ions can move a distance of several atomic spacings, causing point defects to annihilate, dislocations to slip, or to rearrange themselves, thereby effectively repairing lattice defects, reducing lattice distortion energy, and improving crystal integrity. Subsequently, the material is cooled to below 50°C within 1 minute, dynamically freezing the positions of the atoms and preventing grain boundary migration and grain merging and growth.

[0057] It should be emphasized that step S33 amplifies and accumulates the effect of this non-equilibrium state treatment by repeating the above heating-cooling cycle 5-10 times, further eliminating defects. Each cooling is a refreezing process, which ensures the nanoscale size of the formed solid electrolyte.

[0058] Specifically, after steps S32 and S33, the primary powder undergoes a change. The defect density within its crystal is systematically reduced to a minimum, and the lattice arrangement becomes more perfect. This significantly reduces the scattering centers for lithium-ion migration, thereby pushing the intrinsic ionic conductivity of the material to its limit. At the same time, the average particle size of the primary particles does not increase significantly, and its valuable nanoscale characteristics are well preserved. This results in a solid electrolyte that combines the ultra-high ionic conductivity brought about by high crystallinity with the excellent interfacial contact capability with electrode materials due to nanoscale size. This solves the problem of crystal structure destruction and ionic conductivity decay caused by mechanical refinement, while ensuring that the product can build an efficient ionic conductive network in macroscopic applications.

[0059] In addition, the solid electrolyte obtained by the above method has no organic solvent residue and has a complete crystal structure, which reduces interfacial side reactions when in contact with lithium metal anode or high-voltage cathode materials, thereby improving the cycle life and safety of all-solid-state batteries and reducing the use of organic solvents and subsequent processing.

[0060] The following is a comparison of test data for the solid electrolyte obtained by this invention (Group A), solid electrolyte obtained by the traditional solid-phase method (Group B), and solid electrolyte obtained by the traditional liquid-phase method (Group C): Table 1 compares the ionic conductivity and temperature dependence of each group. Table 2 shows the electrochemical performance and cycle stability of each group. Table 3 shows the microstructure and physical compactness of each group. As shown in Table 1, the solid electrolyte obtained in group A exhibits significantly higher ionic conductivity than groups B and C at both room temperature and high temperature. This indicates that group A retains the size advantage of nanoparticles through the Li2S@LiCl core-shell structure, while avoiding the particle coarsening and lattice defect problems found in groups B and C. The improved conductivity of the solid electrolyte at high temperature demonstrates that group A achieves a lower migration barrier through effective nanostructure and high crystallinity maintenance, thereby significantly improving ionic conductivity.

[0061] As shown in Table 2, Group A exhibits superior electrochemical stability. The interfacial resistance and initial overpotential of the solid electrolyte are significantly lower than those of Groups B and C. This indicates that Group A has a clear advantage in the interfacial contact between the electrolyte and the electrode, reducing the problems of poor interfacial contact and unstable electrochemical reactions found in Groups B and C.

[0062] As shown in Table 3, the solid electrolyte in Group A has a particle size maintained at the nanometer level and has a high specific surface area and low porosity, which ensures the high density and low ion transport resistance of the electrolyte. In contrast, Groups B and C, due to long-term ball milling and high-temperature sintering, usually result in particle coarsening and grain boundary expansion, which in turn increases the contact resistance between particles and causes higher porosity, thus reducing the overall performance of the electrolyte.

[0063] In summary, the preparation method proposed by Group A not only successfully solves the limitations of traditional methods in terms of ionic conductivity and interfacial contact, but also overcomes common problems in traditional methods such as excessively large particle size and performance degradation caused by defects by precisely controlling the core-shell structure, airflow impact milling, vapor deposition, and annealing. It is understood that σ (ionic conductivity) and initial interfacial resistance are obtained using AC impedance spectroscopy according to IEC 62620; the initial overpotential of the Li symmetric cell is obtained using constant current cycling according to IEC 61960; particle size is obtained using transmission electron microscopy according to ISO 13322-1; BET (Brunauer-Emmett-Teller method) specific surface area is obtained using static capacity method according to ISO 9277:2010; and relative density is obtained using geometric density method according to ASTM B962. The corresponding testing equipment is well known to those skilled in the art and will not be described further in this embodiment.

[0064] Example 2: This embodiment provides a sulfide solid electrolyte, which is prepared using the method described above.

[0065] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte, characterized in that, The preparation method includes the following steps: Step S1: Prepare Li2S@LiCl core-shell nanoparticles and perform airflow collision milling on them with P2S5 nanoparticles to obtain composite powder; Step S2: The composite powder is placed in a reactor for heating and deposition, and then heated and crystallized to obtain Li6PS5Cl nanoparticles. Step S3: After treating the Li6PS5Cl nanoparticles in a ball mill jar, they are then annealed to obtain a sulfide solid electrolyte.

2. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, Step S1 specifically includes the following steps: Step S11: Disperse and mix Li2S@LiCl core-shell nanoparticles with P2S5 nanoparticles to form a dry mixture; Step S12: Place the dry mixture in the protective atmosphere of the airflow impact mill for impact treatment, and obtain composite powder after the treatment is completed.

3. The method for preparing the sulfide solid electrolyte according to claim 2, characterized in that, In step S11, the D50 of the P2S5 nanopowder is <1μm, and the dispersion and mixing time is 30-60min and the rotation speed is 60-80rpm. In step S12, the working pressure of the collision treatment is 0.5-0.8 MPa, and the treatment time is 5-15 min.

4. The method for preparing the sulfide solid electrolyte according to claim 2, characterized in that, The Li2S@LiCl core-shell nanoparticles were obtained according to the following steps: Step S111: In a protective atmosphere, disperse Li2S powder in anhydrous acetonitrile a to form a suspension; Step S112: Dissolve LiCl in anhydrous acetonitrile b to form a clear solution; Step S113: Add the clear liquid dropwise to the suspension and stir to obtain a slurry. Then, vacuum dry the slurry. After drying, obtain Li2S@LiCl core-shell nanoparticles.

5. The method for preparing the sulfide solid electrolyte according to claim 4, characterized in that, In step S111, the particle size of the Li2S powder is 100-200 nm, and the mass ratio of the Li2S powder to anhydrous acetonitrile a is 1:(1.8-2.2). In step S112, the mass ratio of LiCl to anhydrous acetonitrile is (0.3-0.5):1; In step S113, the drop rate of the clarified liquid is 1-2 drops / s, the stirring time is 1-3 hours and the rotation speed is 300-500 rpm, and the vacuum drying temperature is 50℃ and the vacuum degree is -0.1 MPa.

6. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, Step S2 specifically includes the following steps: Step S21: Spread the composite powder in a container, then send the container into the reaction tube of the reactor. The reactor is then heated to the first temperature to heat and deposit the composite powder. After the heating and deposition are completed, an amorphous precursor is obtained. Step S22: After heating the reactor to the second temperature, the amorphous precursor is heated and crystallized. After the heating and crystallization is completed, it is cooled to room temperature to obtain Li6PS5Cl nanoparticles.

7. The method for preparing the sulfide solid electrolyte according to claim 6, characterized in that, In step S21, the first temperature is 320-350℃, the heating rate is 8-12℃ / min, and the holding time is 30-60min; In step S22, the second temperature is 380-420℃, the heating rate is 3-6℃ / min, the holding time is 60-90min, and the Li6PS5Cl nanoparticles have an aluminosilicate crystal structure.

8. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, Step S3 specifically includes the following steps: Step S31: Feed the Li6PS5Cl nanoparticles into a ball milling jar containing grinding beads, and ball mill at a speed of 300-500 rpm for 30-60 min to obtain primary powder; wherein, the grinding beads are zirconia beads, the size of the grinding beads is 3-6 mm, and the mass ratio of grinding beads to Li6PS5Cl nanoparticles is (18-22):

1. Step S32: Place the primary powder in a vacuum annealing furnace, evacuate the furnace to -0.1MPa, fill it with protective gas, and then anneal the primary powder at an annealing temperature of 200-300℃ for 2-3 minutes, and cool the primary powder to below 50℃ within 1-2 minutes. Step S33: Repeat step S32 to anneal the primary powder 5-10 times to obtain a solid electrolyte.

9. A sulfide solid electrolyte, characterized in that, The sulfide solid electrolyte is prepared using the method described in claims 1-8.

Images