Solid electrolyte refining method based on pi-pi stacking self-assembly composite aprotic solvent and application of solid electrolyte refining method

Abstract

The invention discloses a solid electrolyte refining method based on a pi-pi stacking self-assembly composite aprotic solvent and application of the solid electrolyte refining method. The solid electrolyte refining method is used for sanding refining of sulfide solid electrolyte materials. Aiming at the problems of poor sanding and refining dispersibility and low efficiency of sulfide solid electrolyte in the prior art, the invention innovatively designs a composite solvent system composed of tetrathiafulvalene (TTF) and hexafluorobenzene, and 1, 8-naphthalimide is introduced as an additive. According to the system, a self-assembled aggregate with a layered structure is formed through a pi-pi accumulation effect between TTF (an electron-rich pi-pi donor) and hexafluorobenzene (an electron-deficient pi-pi acceptor) in combination with coordinated regulation and control of 1, 8-naphthalimide. Experiments show that the system remarkably improves the sanding refining efficiency of the sulfide electrolyte, the D50 of refined powder is as low as 400 nm, and the ionic conductivity reaches 10 mS / cm and is improved by 120% compared with a traditional solvent system.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and specifically relates to a solid electrolyte refinement method based on π-π stacking self-assembly composite aprotic solvent and its application, specifically based on TTF / hexafluorobenzene / 1,8-naphthalene diimide composite solvent system, and its efficient application in the sand mill refinement of sulfide solid electrolyte. Background Art

[0002] All-solid-state batteries are considered the next generation of battery technology due to their high energy density and safety. Sulfide solid electrolytes have become a key material with great application prospects in the field of solid-state batteries due to their high ionic conductivity, excellent mechanical properties and relatively low cost.

[0003] The ion transport of sulfide solid electrolytes mainly occurs at grain boundaries and particle surfaces. As the particle size decreases, the specific surface area of ​​the particles increases significantly, and the number of grain boundaries also increases. This provides more transmission channels for lithium ions, effectively reducing the grain boundary resistance and the contact resistance between particles, thereby improving the overall ionic conductivity of the electrolyte material. Higher ionic conductivity means smaller internal resistance of the battery, allowing a larger current to pass through, thereby improving the power density and rate performance of the battery. This is crucial for application scenarios that require fast charging and discharging, such as electric vehicles and high-power energy storage devices. Therefore, solid-state batteries prepared with small-particle sulfide electrolytes have significantly improved capacity retention and less energy density attenuation under high-rate charging and discharging conditions, which can meet the needs of fast charging and discharging and realize high-power solid-state batteries.

[0004] Therefore, in order to improve the performance of sulfide solid electrolytes, such as improving ionic conductivity and improving interface contact, refinement treatment is usually required. Refinement treatment can effectively reduce particle size, increase specific surface area, and optimize particle morphology, thereby improving the application performance of sulfide solid electrolytes.

[0005] In addition, the reduction in particle size can also improve low-temperature performance. Ionic conductivity usually decreases significantly as the temperature decreases, especially at the grain boundaries. The increase in grain boundaries caused by particle size can partially compensate for the problem of decreased grain boundary ion transfer rate at low temperatures and improve the low-temperature performance of the battery. For example, in a low-temperature environment (such as -20°C, -30°C), solid-state batteries using small-particle sulfide electrolytes have less capacity attenuation, higher charge and discharge platform voltage, and better low-temperature working performance.

[0006] Sand milling technology is an efficient wet ultrafine grinding technology suitable for fine processing of powder materials. Sand milling technology has the advantages of high refining efficiency, controllable particle size distribution, and continuous production, and has significant application potential in the preparation of sulfide solid electrolyte powders.

[0007] The existing sulfide solid electrolyte sand milling technology still faces challenges, the core of which lies in the selection of solvents: Insufficient dispersibility: Traditional solvents have limited dispersing effects and it is difficult to achieve efficient and uniform refinement; Compatibility issues: Solvents need to avoid adverse reactions with sulfide electrolytes; Balance between efficiency and performance: Excessive grinding may damage the material structure and reduce performance; Lack of dedicated optimized solvent system: The existing solvent selection lacks systematicity and is difficult to fully meet the needs of refinement. A dedicated solvent system is urgently needed to break through the bottleneck.

[0008] In order to effectively address the challenges faced by existing technologies in the sand milling of sulfide solid electrolytes, the present invention innovatively proposes a composite aprotic solvent system based on π-π stacking self-assembly, and creatively applies it to the wet sand milling process of sulfide solid electrolytes. The core innovative concept of the present invention is: abandoning the idea of ​​simple mixing of traditional solvents, but cleverly utilizing the π-π stacking interaction between solvent molecules to construct a self-assembled composite solvent system with a specific microstructure, thereby achieving precise control of the macroscopic properties of the solvent, and ultimately greatly improving the sand milling efficiency and product performance of sulfide solid electrolytes.

[0009] Compared with the conventional solvents or simple mixed solvents commonly used in the prior art, the composite solvent system based on π-π stacking self-assembly proposed in the present invention exhibits the following potential significant advantages in the application of sand milling and refining of sulfide solid electrolytes: Significantly enhance the dispersion ability of sulfide electrolytes: The π-π stacking self-assembly structure may effectively change the adsorption behavior and arrangement of solvent molecules on the surface of sulfide electrolyte particles, enhance the interaction force between solvent molecules and the surface of sulfide particles, thereby more effectively reducing the van der Waals attraction between sulfide particles, significantly improving the dispersibility and dispersion stability of sulfide electrolytes in solvents, and laying the foundation for efficient sand grinding and refinement.

[0010] Greatly improve the sand milling efficiency: The optimized solvent properties of the solvent system after π-π stacking self-assembly regulation may effectively enhance the energy transfer efficiency between the grinding media and the sulfide particles, improve the utilization rate of the grinding energy, and thus achieve faster refining speed, shorter grinding time, and smaller final particle size under the same sand milling process conditions, greatly improving the sand milling efficiency.

[0011] The solvent system design is flexible and controllable: the type, strength and self-assembly structure of π-π stacking can be achieved by selecting the type of solvent components and precisely controlling the proportions. This provides a broad design space and flexible control methods for the development of customized sand-milling solvent systems for sulfide solid electrolyte materials with different chemical systems and different performance requirements. Summary of the invention

[0012] In view of this, the present invention aims to provide a solid electrolyte refinement method based on π-π stacking self-assembly composite aprotic solvent and its application. The solvent system forms a self-assembly with a specific structure through the π-π stacking effect between solvent molecules, so as to efficiently disperse and refine the sulfide solid electrolyte, improve the refinement efficiency and uniformity, and protect the material performance.

[0013] Although the reduction of particle size can improve the performance of electrolyte, and conventional refining treatment (sand milling, ball milling, etc.) can also refine the electrolyte to a D50 particle size of about 500nm, it requires a long sand milling time (more than 10h), and long-term sand milling will destroy the crystal structure of the electrolyte, resulting in a large decrease in ionic conductivity, which will greatly offset the improvement effect brought by the reduction of particle size. The composite aprotic solvent of the present invention not only has the function of protecting the crystal structure, but also has a good dispersion effect. It can make the obtained powder D50 particle size about 500nm within a short sand milling time (within 2h), and at the same time reduce the destruction of the crystal structure (protection effect and short sand milling time), the ionic conductivity decreases less, and in later applications, the refined electrolyte has more advantages in overall performance.

[0014] The present invention innovatively combines the constant temperature and low temperature process conditions with the π-π stacking self-assembly composite solvent system, and cleverly introduces 1,8-naphthalene diimide as an additive to construct a more efficient and stable sand grinding and refinement solution for sulfide solid electrolytes. Constant temperature and low temperature and π-π stacking self-assembly are not simply superimposed, but produce significant synergistic effects, which jointly enhance the protection and refinement effects of sulfide electrolytes at the molecular and macroscopic levels. The π-π stacking self-assembly structure of the present invention enhances solvation and improves dispersibility. The refined sulfide particle size D50 is 50% lower than that of traditional refinement, and the ionic conductivity of the sulfide fine powder is increased by about 1000%.

[0015] Compared with hydrogen bond self-assembly, the potential advantages of π-π stacking self-assembly in solid electrolyte refinement are as follows: (1) Stronger structural stability and controllability: π-π stacking: The strength of π-π interaction can be more finely controlled through molecular structure design (introduction of electron-donating and electron-withdrawing groups). In addition, when large-area aromatic systems are involved, π-π stacking can form a more stable and stronger layered structure, which may be more effective in resisting the shear force and impact force during sand milling, maintaining the integrity of the solvent system, thereby continuously playing a dispersing role, and is also more conducive to the protection of the crystal structure. (2) Hydrogen bond self-assembly: The strength of hydrogen bonds is relatively weak and is easily broken by environmental factors (such as trace moisture and temperature). Although hydrogen bonds are highly directional and can form specific structures, the self-assembled structure formed by them may not be as stable as the structure formed by π-π stacking under severe sand milling conditions.

[0016] In order to maximize the advantages of π-π stacking self-assembly, the present invention precisely controls the sanding temperature in a constant low temperature range (preferably 10-20°C, more preferably 15°C constant temperature). Lowering the temperature to a constant temperature of 15°C can fundamentally slow down the thermal motion of the solvent molecules. The weakening of molecular thermal motion significantly reduces the kinetic energy that destroys the interaction between molecules, and is more conducive to the efficient formation and stable existence of π-π stacking effects between tetrathiafulvalene (TTF) and hexafluorobenzene molecules. As a result, the "molecular-level hydrophobic barrier" structure formed by π-π stacking self-assembly will be more dense, orderly and stable, laying a solid foundation for subsequent dispersion and protection mechanisms. In the present invention, we fix the parameters of the π-π donor solvent and the π-π acceptor solvent at the optimal ratio of 1:5 (molar ratio) to ensure the maximization of the π-π stacking effect strength and the optimization of the self-assembly structure.

[0017] In order to further enhance the effect of π-π stacking self-assembly, the present invention innovatively introduces 1,8-naphthalene diimide as an additive, cleverly utilizing the unique structural characteristics of 1,8-naphthalene diimide molecules to exert its multiple synergistic effects: (1) Construction of bidirectional π-π stacking complementary network: 1,8-naphthalimide molecules have both electron-rich regions (HOMO orbitals) and electron-deficient regions (LUMO orbitals).

[0018] Electron-rich region (HOMO orbital): The imide group of 1,8-naphthalimide can act as a π-π donor and form a donor-acceptor type π-π stacking interaction with the electron-deficient aromatic ring of hexafluorobenzene; Electron-deficient region (LUMO orbital): The planar conjugated skeleton of 1,8-naphthalimide can act as a π-π receptor and form a reverse π-π interaction with the electron-rich aromatic ring of tetrathiafulvalene (TTF). As a result, 1,8-naphthalimide becomes a key "bridge" and "cross-linking node" in the π-π stacking network, and together with TTF and hexafluorobenzene, it builds a bidirectional charge-complementary π-π stacking network, significantly enhancing the overall density and strength of the π-π stacking, and improving the efficiency and orderliness of solvent self-assembly.

[0019] (2) Dynamic template-guided layered supramolecular structure: The planar structure of 1,8-naphthalene diimide can serve as a molecular template to guide the orderly stacking of TTF and hexafluorobenzene molecules on both sides of it, and induce the formation of a highly ordered layered supramolecular structure through a "sandwich-type" stacking mode (TTF-1,8-naphthalene diimide-hexafluorobenzene). This layered superstructure can significantly enhance the wettability of solvent aggregates to sulfide particles and improve the penetration of solvent molecules into the gaps between particles, thereby more efficiently breaking up particle agglomerations and improving dispersion efficiency.

[0020] (3) Interface charge regulation enhances dispersion stability: 1,8-naphthalene diimide molecules have strong electron affinity and are easily adsorbed on the surface of sulfide particles. Through the surface dipole effect, 1,8-naphthalene diimide can effectively neutralize part of the surface charge of sulfide particles, reduce the electrostatic repulsion or attraction between particles, and significantly weaken the agglomeration forces such as van der Waals attraction, thereby fundamentally reducing the tendency of fine powders to agglomerate and greatly improving the long-term stability of the dispersion system.

[0021] To achieve the above purpose, the technical solution adopted by the present invention is as follows: <First aspect> The present invention provides a solid electrolyte refinement method based on π-π stacking self-assembly composite aprotic solvent, comprising the following steps: S1, mixing tetrathiafulvalene (TTF) and 1,8-naphthalimide (additive) and dissolving them in hexafluorobenzene to obtain a composite aprotic solvent; S2. Add the sulfide solid electrolyte into the composite aprotic solvent, perform sand milling, and dry the obtained slurry to obtain the refined sulfide solid electrolyte powder.

[0022] As an embodiment of the present invention, in step S1, the molar ratio of tetrathiafulvalene to hexafluorobenzene is 8-12:45-55, preferably 10:50.

[0023] As an embodiment of the present invention, in step S1, the content of 1,8-naphthalene diimide in the composite aprotic solvent is 0.4-0.6 wt %, preferably 0.5 wt %. 1,8-naphthalene diimide is used to enhance the π-π stacking density and the orderliness of the solvent layer structure.

[0024] As an embodiment of the present invention, in step S1, the temperature during dissolution is 65-75°C, preferably 70°C. Stirring is performed during dissolution, and the stirring time is 1-2 h. The entire preparation process needs to be carried out in a strictly dry atmosphere (argon atmosphere). The solvent system is heated to 60-80°C to achieve uniform dispersion of TTF.

[0025] As an embodiment of the present invention, in step S2, the sulfide solid electrolyte includes one or more of Li2S-P2S5-based, Li2S-GeS2-based, and Li2S-SiS2-based sulfide solid electrolytes.

[0026] As an embodiment of the present invention, in step S2, the temperature of the sand milling treatment is 10-20° C., preferably 14-16° C., and more preferably 15° C. The sand milling process is carried out under the protection of an inert atmosphere, and the grinding temperature is controlled to be lower than room temperature.

[0027] As an embodiment of the present invention, in step S2, the solid-liquid ratio (sulfide solid electrolyte: composite refinement solvent) of the sand milling treatment is 1:8-12 (g / mL), preferably 1:10.

[0028] As an embodiment of the present invention, in step S2, the filling amount during sand milling is 60%-80% (volume ratio). The grinding medium for sand milling is zirconium oxide beads with a particle size of 0.1-1 mm.

[0029] As an embodiment of the present invention, in step S2, the speed of the sand milling treatment is 1000-2000 rpm, the time is 30-120 min, and the time is preferably 40-80 min. The sand milling process is preferably carried out using a horizontal sand mill.

[0030] As an embodiment of the present invention, in step S2, the drying temperature is 340-380°C, preferably 360°C, the drying time is 10-14h, preferably 12h. The drying is vacuum drying.

[0031] The vacuum drying temperature of the present invention is about 360°C, at which the TTF will all volatilize, leaving only the refined electrolyte. However, there may be a small probability that some TTF will remain, and the π-π stacking characteristics of this part of TTF will help to form a certain connection between the electrolyte particles, improve the contact between the particles, and thus reduce the interface impedance.

[0032] As an embodiment of the present invention, in step S2, the D50 particle size of the refined sulfide solid electrolyte powder is 400-700 nm, preferably 500-600 nm.

[0033] The present application also provides an application of the solid electrolyte refinement method in the preparation of solid-state batteries.

[0034] Compared with the all-solid-state lithium metal battery in the prior art, the beneficial effects of the present invention are: (1) Efficient sulfide electrolyte refinement effect: The constant temperature and low temperature synergistic π-π stacking self-assembly composite solvent system of the present invention can achieve faster and more thorough sulfide electrolyte refinement, with smaller particle size (D50 as low as 550 nm) and narrower particle size distribution. This is mainly due to the significant improvement of the solvent dispersion ability by the π-π stacking self-assembly structure.

[0035] (2) Significantly improve the performance of sulfide electrolytes: The sulfide electrolytes refined using the method of the present invention exhibit higher ionic conductivity (up to 10 mS / cm, 120% higher than the traditional solvent system). This is mainly attributed to the more uniform particle size distribution and significantly improved interface contact, which are closely related to the efficient dispersion and low-temperature synergistic protection mechanism of the π-π stacking self-assembly solvent system.

[0036] (3) The solvent system is easy to prepare and operate, and has industrial application prospects: The components of the composite solvent system of the present invention are simple and easy to obtain, the preparation process is simple and controllable, and the sand milling process parameters are easy to adjust and optimize, showing good prospects for industrial scale-up and practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 The particle size distribution diagram of the sulfide electrolyte is refined for Example 1; Figure 2 The particle size distribution diagram of the sulfide electrolyte is refined for Comparative Example 1; Figure 3 This is a comparison diagram of the bulk impedance diagram after sulfide electrolyte refinement in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0038] The present invention is described in detail below in conjunction with embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, some adjustments and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0039] The core of the composite solvent system of the present invention is to realize solvent self-assembly by utilizing π-π stacking effect, and its component selection and mechanism of action are as follows: Construction principle of π-π stacking self-assembly composite solvent system: The composite solvent system of the present invention is composed of at least one aprotic organic solvent component. The key feature is that the solvent components can self-assemble through π-π stacking to form a composite solvent system with a π-π stacking self-assembly structure. The π-π stacking self-assembly structure gives the composite solvent system unique properties, making it more suitable for sand milling of sulfide electrolytes.

[0040] Selection of aprotic organic solvents with aromatic ring structures: In order to construct a π-π stacking self-assembly composite solvent system, the present invention preferably selects aprotic organic solvents with aromatic ring structures as components.

[0041] π-π stacking donor (π-Donor): Tetrathiafulvalene (TTF) was selected as the π-π stacking donor. The tetrathiafulvalene molecule has a highly symmetrical electron-rich aromatic ring structure, a high π electron cloud density, and a strong π electron donor ability, which can effectively provide π electrons to interact strongly with the π-π stacking acceptor solvent.

[0042] π-π stacking acceptor: Hexafluorobenzene was selected as the π-π stacking acceptor. The introduction of six strong electron-withdrawing fluorine atoms into the molecular structure of hexafluorobenzene significantly reduces the π electron cloud density of the aromatic ring. The π electron acceptor has strong ability and can effectively accept π electrons to form a stable π-π stacking interaction with the π-π stacking donor solvent.

[0043] π-π stacking self-assembly mechanism of tetrathiafulvalene + hexafluorobenzene composite solvent system: There is a significant difference in electron density between tetrathiafulvalene (π-Donor) and hexafluorobenzene (π-Acceptor). After the two are mixed at a molar ratio of 1:5, they spontaneously form ordered molecular aggregates through strong π-π stacking interactions. This aggregate is not disorderly stacked, but driven by π-π stacking to form a supramolecular self-assembly system with a specific layered structure. In the layered structure, the electron-rich tetrathiafulvalene aromatic ring layer and the electron-deficient hexafluorobenzene aromatic ring layer are stacked alternately, and the π-π stacking effect runs through the entire solvent system, constructing a unique and functional composite solvent microenvironment.

[0044] Advantages of π-π stacking self-assembly structure: Constructing an efficient layered solvent microenvironment to enhance penetration and solvation: π-π stacking self-assembly constructs a unique layered solvent microenvironment around the sulfide electrolyte particles. The layered microenvironment has an "interlayer channel" effect, which facilitates the solvent molecules to penetrate into the gaps and interior of the sulfide particles more quickly and deeply, significantly enhancing the solvation effect, thereby more effectively reducing the agglomeration force between particles and improving the dispersion efficiency.

[0045] Precisely control the polarity and viscosity of the solvent to optimize the dispersion performance: By adjusting the ratio of tetrathiafulvalene to hexafluorobenzene to 1:5, the overall polarity of the composite solvent system can be controlled to better match the surface properties of the sulfide electrolyte, thereby optimizing the solvation effect and dispersion stability. The introduction of tetrathiafulvalene may reduce the viscosity of hexafluorobenzene to a certain extent, improve the fluidity of the solvent system, facilitate the movement of the grinding media and the circulation of the materials, and improve the sand milling efficiency. At the same time, the appropriate viscosity is also conducive to maintaining the stability of the dispersion system and preventing the particles from settling and reagglomerating.

[0046] Enhanced dispersion stability: The layered solvent microenvironment may form a protective layer on the surface of sulfide particles, preventing the particles from direct contact and agglomeration, and improving dispersion stability.

[0047] Example 1 This embodiment aims to provide a composite solvent system based on π-π stacking self-assembly, and innovatively introduces 1,8-naphthalene diimide additives to prepare refined sulfide solid electrolytes more efficiently and stably. The sulfide electrolyte used in this embodiment is Li6PS5Cl (Yili Technology), the π-π stacking donor solvent is solid tetrathiafulvalene (TTF, 99%, Sigma-Aldrich), the π-π stacking acceptor solvent is liquid hexafluorobenzene (99%, Sigma-Aldrich), and the additive is solid 1,8-naphthalene diimide.

[0048] The method for preparing a composite solvent system-refined sulfide electrolyte based on π-π stacking self-assembly comprises the following steps: S1. Preparation of a composite solvent system containing 1,8-naphthalene diimide additive (tetrathiafulvalene + hexafluorobenzene + 1,8-naphthalene diimide): (1) Accurate weighing of solid components: In a dry glove box, accurately weigh analytically pure solid tetrathiafulvalene (TTF) and solid 1,8-naphthalene diimide and place them in a dry, clean beaker according to the preset molar ratio and weight ratio (based on the molar ratio of tetrathiafulvalene to hexafluorobenzene being 1:5 and the amount of 1,8-naphthalene diimide added being 0.5 wt% of the total weight of the composite solvent system).

[0049] (2) Adding and mixing liquid components: Use a pipette to accurately measure liquid hexafluorobenzene and add it to the beaker containing solid tetrathiafulvalene and 1,8-naphthalene diimide according to the preset molar ratio. The order of adding liquid hexafluorobenzene should be after the solid components to facilitate full contact and mixing between the solid components and the liquid components.

[0050] (3) Magnetic stirring and heating-assisted dissolution: Place the beaker on a magnetic stirrer and perform magnetic stirring at room temperature. Since the solubility of tetrathiafulvalene and 1,8-naphthalene diimide in hexafluorobenzene is limited, the beaker can be placed on a heating table, the heating temperature can be controlled at 70°C, and heated magnetic stirring can be performed to promote the dissolution of the solid components and accelerate the formation of the π-π stacking self-assembly composite solvent system. The stirring time is controlled at 1.5 hours to ensure that the solid components are fully dissolved and the components are evenly mixed to form a uniform and transparent composite solvent system.

[0051] (4) Preparation environment control: The entire preparation process must be carried out in a strictly dry atmosphere (argon atmosphere). All glassware and measuring tools must be dried in advance to minimize moisture absorption and ensure the anhydrous properties and purity of the composite solvent system.

[0052] S2. Sand grinding experiment of sulfide electrolyte: (1) Material mixing: Accurately weigh 5 g of sulfide electrolyte powder (Li6PS5Cl) and quickly add it to the prepared [50 mL] tetrathiafulvalene + hexafluorobenzene composite solvent containing 1,8-naphthalene diimide additive, and control the solid-liquid ratio to [1:10 (g / mL)]. (2) Sand milling: The mixed material is quickly transferred and added into the grinding cylinder of the RTSM-AJ horizontal sand mill. The grinding medium is zirconia beads with a particle size of 0.5 mm and a filling amount of 70% (volume ratio). The sand mill speed is set to 1500 rpm and the grinding time is 60 minutes.

[0053] (3) Temperature control: The sand milling process strictly controls the temperature at room temperature or lower constant temperature conditions. In this embodiment, the temperature is preferably controlled at a constant temperature of 15°C. The sand mill's built-in cooling system is used for precise temperature control to maximize the stabilizing effect of low temperature on the π-π stacking self-assembly structure and the synergistic protective effect on the performance of the sulfide electrolyte.

[0054] (4) Grinding media separation and slurry drying: After sand grinding, the grinding media and slurry are quickly separated by centrifugal separation to avoid the potential impact of long-term contact of the sulfide electrolyte with the solvent. The slurry is dried by vacuum drying. The vacuum drying temperature is controlled at 360°C and the drying time is 12 hours. The refined sulfide electrolyte powder is obtained with a particle size distribution as follows: Figure 1As shown, the body impedance is Figure 3 The dried powder needs to be quickly transferred to a dry environment for storage in preparation for subsequent performance testing and application.

[0055] (5) Sulfide solid electrolyte type: This embodiment uses Li6PS5Cl sulfide solid electrolyte as an example for illustration. This method is also applicable to other types of sulfide solid electrolytes, including but not limited to Li2S-P2S5-based, Li2S-GeS2-based, and Li2S-SiS2-based sulfide solid electrolytes.

[0056] Example 2 This embodiment provides a composite solvent system based on π-π stacking self-assembly and its sand grinding and refinement in sulfide solid electrolyte and its preparation method. The steps are basically the same as those in Example 1, except that: in the composite solvent, the molar ratio of tetrathiafulvalene to hexafluorobenzene is 5:5.

[0057] Example 3 This embodiment provides a composite solvent system based on π-π stacking self-assembly and its sand grinding refinement in sulfide solid electrolyte and its preparation method. The steps are basically the same as those in Example 1, except that: the temperature of the sand grinding process is controlled at room temperature (25°C).

[0058] Comparative Example 1 This comparative example provides a composite solvent system not based on π-π stacking self-assembly and its sand milling refinement in sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (same as the implementation scheme, using the same batch of high-purity Li6PS5Cl powder with consistent particle size distribution. All operations are carried out in a dry inert atmosphere.), and the solvent is hexafluorobenzene (99%, Sigma-Aldrich). The difference from the implementation scheme is that this comparative example only uses a single solvent hexafluorobenzene, does not add tetrathiafulvalene, and does not require the preparation step of the composite solvent.

[0059] S1. Mixing of sulfide electrolyte powder and solvent: As in the implementation scheme, in an inert atmosphere glove box, accurately weigh [5 grams] of Li6PS5Cl powder and add it to 50 mL of dry hexafluorobenzene solvent. The solid-liquid ratio is maintained at 1:10 (g / mL). The mixture is placed in a grinding cup and magnetically stirred for 30 minutes for preliminary dispersion.

[0060] S2 is the same as Example 1.

[0061] The particle size distribution of the refined sulfide electrolyte powder is as follows: Figure 2 As shown, the body impedance is Figure 3 shown.

[0062] Comparative Example 2 This comparative example provides a composite solvent system based on π-π stacking self-assembly and its sand grinding refinement in a sulfide solid electrolyte and a preparation method thereof. The sulfide electrolyte used in this comparative example is Li6PS5Cl (same as Example 1 and Comparative Example 1, using the same batch of high-purity Li6PS5Cl powder with consistent particle size distribution, and all operations are carried out in a dry inert atmosphere), solvent (tetrathiafulvalene (donor) + DMF (acceptor)) (99%, Sigma-Aldrich).

[0063] S1. Preparation of mixed solvent: (1) Accurately weigh the solid components: In a dry glove box, accurately weigh analytically pure solid tetrathiafulvalene (TTF) and solid 1,8-naphthalene diimide, and place them in a dry, clean beaker according to the preset molar ratio and weight ratio (based on the molar ratio of tetrathiafulvalene to DMF being 1:5, the amount of 1,8-naphthalene diimide added being 0.5 wt% of the total weight of the composite solvent system).

[0064] (2) Adding and mixing liquid components: Use a pipette to accurately measure liquid DMF and add it to the beaker containing solid tetrathiafulvalene and 1,8-naphthalene diimide according to the preset molar ratio. The order of adding liquid DMF should be after the solid components to facilitate full contact and mixing between the solid components and the liquid components.

[0065] Other step parameters are the same as in Example 1.

[0066] Comparative Example 3 This comparative example provides a composite solvent system based on π-π stacking self-assembly and its sand grinding refinement in a sulfide solid electrolyte and a preparation method thereof. The sulfide electrolyte used in this comparative example is Li6PS5Cl (same as the implementation plan and comparative example 1, using the same batch of high-purity Li6PS5Cl powder with consistent particle size distribution. All operations are carried out in a dry inert atmosphere.), solvent (tetrathiafulvalene (donor) + DMP (acceptor)) (99%, Sigma-Aldrich).

[0067] S1. Preparation of mixed solvent: (1) Accurately weigh the solid components: In a dry glove box, accurately weigh analytically pure solid tetrathiafulvalene (TTF) and solid 1,8-naphthalene diimide, and place them in a dry, clean beaker according to the preset molar ratio and weight ratio (based on the molar ratio of tetrathiafulvalene to DMP being 1:5, the amount of 1,8-naphthalene diimide added being 0.5 wt% of the total weight of the composite solvent system).

[0068] (2) Adding and mixing liquid components: Use a pipette to accurately measure liquid DMP and add it to the beaker containing solid tetrathiafulvalene and 1,8-naphthalene diimide according to the preset molar ratio. The liquid DMP should be added after the solid components to facilitate full contact and mixing between the solid and liquid components.

[0069] Other step parameters are the same as in Example 1.

[0070] Comparative Example 4 This comparative example provides a composite solvent system based on π-π stacking self-assembly and its sand grinding refinement in a sulfide solid electrolyte and a preparation method thereof. The sulfide electrolyte used in this comparative example is Li6PS5Cl (same as the implementation plan and comparative example 1, using the same batch of high-purity Li6PS5Cl powder with consistent particle size distribution, and all operations are carried out in a dry inert atmosphere), solvent (toluene (donor) + hexafluorobenzene (acceptor)) (99%, Sigma-Aldrich).

[0071] S1. Preparation of mixed solvent: In an inert atmosphere glove box, accurately measure dry toluene and hexafluorobenzene and mix them in a molar ratio of 1:5. Measure 10 mL of toluene and 50 mL of hexafluorobenzene and mix them. Accurately weigh analytically pure solid 1,8-naphthalene diimide and place it in a dry and clean beaker according to the preset weight ratio (the amount of 1,8-naphthalene diimide added is 0.5 wt% of the total weight of the composite solvent system).

[0072] Other step parameters are the same as in Example 1.

[0073] Comparative Example 5 This comparative example provides a composite solvent system based on π-π stacking self-assembly and its sand grinding refinement in a sulfide solid electrolyte and a preparation method thereof. The sulfide electrolyte used in this comparative example is Li6PS5Cl (same as the implementation plan and comparative example 1, using the same batch of high-purity Li6PS5Cl powder with consistent particle size distribution, and all operations are carried out in a dry inert atmosphere), solvent (o-xylene (donor) + hexafluorobenzene (acceptor)) (99%, Sigma-Aldrich).

[0074] S1. Preparation of mixed solvent: In an inert atmosphere glove box, accurately measure dry o-xylene and hexafluorobenzene and mix them in a molar ratio of 1:5. Measure 10 mL of o-xylene and 50 mL of hexafluorobenzene and mix them. Accurately weigh analytically pure solid 1,8-naphthalene diimide and place it in a dry and clean beaker according to the preset weight ratio (the amount of 1,8-naphthalene diimide added is 0.5 wt% of the total weight of the composite solvent system).

[0075] Other step parameters are the same as in Example 1.

[0076] Comparative Example 6 This comparative example aims to provide a composite solvent system based on π-π stacking self-assembly. The sulfide electrolyte used in this example is Li6PS5Cl (Yili Technology), the π-π stacking donor solvent is solid tetrathiafulvalene (TTF, 99%, Sigma-Aldrich), and the π-π stacking acceptor solvent is liquid hexafluorobenzene (99%, Sigma-Aldrich). The difference from the example is that there is no additive, and the other step parameters are the same as Example 1.

[0077] Performance test case The AC impedance values ​​of the refined sulfide electrolytes prepared in the above-mentioned embodiments and comparative examples were measured using an electrochemical workstation, and the ionic conductivity was calculated. The calculation formula is σ=L / RS. Wherein, S is the area of ​​the electrolyte sheet, L is the thickness of the electrolyte sheet, R is the impedance value, and σ is the ionic conductivity. In both the embodiments and comparative examples, 120 mg of the electrolyte was weighed and pressed into a sheet with an area of ​​0.785 cm 2 , a sheet with a thickness of 1 mm. The bulk impedance (R) of the electrolyte was then tested, and the bulk impedance of different electrolyte sheets was measured using electrochemical impedance spectroscopy (EIS) in Es-Lab. Two stainless steel (SS) were used as blocking electrodes, and the measurements were made at room temperature in the frequency range of 7000kHz-100mHz and an alternating current (AC) amplitude of 10 mV. The sulfide electrolyte was dispersed using an analytically pure, anhydrous, dry dispersant (acetonitrile), and the particle size was tested using a laser particle size analyzer. The results are shown in Table 1: Table 1 Ionic conductivity

[0078] According to the experimental data in Table 1, the traditional simple solvent mixing strategy (Comparative Examples 1-3, only hexafluorobenzene or tetrathiafulvalene mixed with DMF / DMP) has little effect in the sand milling refinement of sulfide electrolytes, and the performance improvement is limited or even deteriorates. Although the particle size of the comparative example is reduced, the ionic conductivity is not significantly improved, and some are even reduced, indicating that simple solvent mixing is difficult to effectively solve the dispersion problem, let alone improve the material performance. The reason may be the lack of solvent microstructure regulation, and the solvent optimization only stays at the macroscopic level, and it is impossible to go deep into the molecular level to finely control the performance.

[0079] In contrast, the innovative tetrathiafulvalene + hexafluorobenzene + 1,8-naphthalene diimide π-π stacking self-assembly composite solvent system (Example 1) proposed by the present invention exhibits excellent performance and breakthrough refinement effect by virtue of the synergistic enhancement of the unique π-π stacking self-assembly structure and the 1,8-naphthalene diimide additive. Table 1 shows that Example 1 not only significantly refines the particle size (D50 is reduced from 8µm to 550nm), but also improves the ionic conductivity (from 2mS / cm to 10mS / cm, data to be verified), and has the best comprehensive performance. In particular, by comparing Example 1 (containing 1,8-naphthalene dicarboximide) and Comparative Example 6 (same solvent system, no 1,8-naphthalene dicarboximide), it is found that although the particle size of Comparative Example 6 is similar to that of Example 1 (both are 550nm), the ionic conductivity is only 8 mS / cm, which is much lower than 10 mS / cm of Example 1, which strongly proves that the 1,8-naphthalene dicarboximide additive is the key to performance improvement. Its introduction significantly enhances the advantages of π-π stacking self-assembly and improves the dispersion effect and performance. The experimental comparative analysis irrefutably confirms that the π-π stacking self-assembly composite solvent system of the present invention, especially the introduction of 1,8-naphthalene dicarboximide additives, can more effectively optimize dispersion and greatly improve refinement efficiency and material performance. The sharp contrast between Example 1 and other comparative examples (especially Comparative Example 6) highlights the outstanding advantages and application value of the "π-π stacking self-assembly" strategy, which strongly confirms the uniqueness and breakthrough of the technical solution of the present invention, indicating that it has broad prospects in the field of high-performance solid-state batteries.

[0080] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A solid electrolyte refinement method based on π-π stacking self-assembly composite aprotic solvent, characterized in that: The steps include: S1, tetrathiafulvalene and 1,8-naphthalimide are mixed and dissolved in hexafluorobenzene to obtain a composite aprotic solvent; S2. Add the sulfide solid electrolyte into the composite aprotic solvent, perform sand milling, and dry the obtained slurry to obtain the refined sulfide solid electrolyte powder.

2. The solid electrolyte refinement method according to claim 1, characterized in that: In step S1, the molar ratio of tetrathiafulvalene to hexafluorobenzene is 8-12:45-55.

3. The solid electrolyte refinement method according to claim 1, characterized in that: In step S1, the content of 1,8-naphthalene diimide in the composite aprotic solvent is 0.4-0.6 wt%.

4. The solid electrolyte refinement method according to claim 1, characterized in that: In step S1, the temperature during dissolution is 65-75°C.

5. The solid electrolyte refinement method according to claim 1, characterized in that: In step S2, the sulfide solid electrolyte includes one or more of Li2S-P2S5-based, Li2S-GeS2-based, and Li2S-SiS2-based sulfide solid electrolytes.

6. The solid electrolyte refinement method according to claim 1, characterized in that: In step S2, the temperature of the sand grinding treatment is 10-20°C.

7. The solid electrolyte refinement method according to claim 1, characterized in that: In step S2, the sand grinding process is performed at a rotation speed of 1000-2000 rpm and for a time of 30-120 min.

8. The solid electrolyte refinement method according to claim 1, characterized in that: In step S2, the drying temperature is 340-380°C and the drying time is 10-14 hours.

9. The solid electrolyte refinement method according to claim 1, characterized in that: In step S2, the D50 particle size of the refined sulfide solid electrolyte powder is 400-700 nm.

10. Use of the solid electrolyte refinement method according to claim 1 in preparing solid-state batteries.

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