Method for Refining Solid Electrolyte Based on Self-Assembly of π-π Stacking Composite Aprotic Solvent and Its Application

Abstract

The present invention discloses a method for refining a solid electrolyte based on π-π stacking self-assembled composite aprotic solvents and its application, which is used for the sanding and refining of sulfide solid electrolyte materials. Aiming at the problems of poor dispersion and low efficiency in the sanding and refining of sulfide solid electrolytes in the prior art, the present invention innovatively designs a composite solvent system composed of tetrathiafulvalene (TTF) and hexafluorobenzene, and introduces 1,8-naphthalenedicarboximide as an additive. Through the π-π stacking interaction between TTF (electron-rich π-π donor) and hexafluorobenzene (electron-deficient π-π acceptor), and the synergistic regulation of 1,8-naphthalenedicarboximide, the system forms self-assembled aggregates with a layered structure. Experiments show that the system significantly improves the sanding and refining efficiency of sulfide electrolytes. After refining, the D50 of the powder is as low as 400 nm, and the ionic conductivity reaches 10 mS / cm, which is 120% higher than that of the traditional solvent system.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and specifically relates to a method for refining a solid electrolyte based on π-π stacking self-assembled composite aprotic solvents and its application. Specifically, it is the efficient application of a composite solvent system of TTF / hexafluorobenzene / 1,8-naphthalimide in the sanding and refining of sulfide solid electrolytes. Background Art

[0002] All-solid-state batteries are regarded as the development direction of next-generation battery technologies due to their high energy density and safety. Sulfide solid electrolytes have become key materials 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] Ionic transport in sulfide solid electrolytes mainly occurs at grain boundaries and particle surfaces. After the particle size is reduced, the specific surface area of the particles increases significantly, and the number of grain boundaries also increases accordingly. This provides more transport channels for lithium ions, effectively reducing the grain boundary resistance and the contact resistance between particles, thereby enhancing the overall ionic conductivity of the electrolyte material. A higher ionic conductivity means a 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, high-power energy storage devices, etc. Therefore, all-solid-state batteries prepared with small-sized sulfide electrolytes have a significantly improved capacity retention rate and a smaller energy density decay under high-rate charge and discharge conditions, can meet the requirements of fast charging and discharging, and achieve high-power solid-state batteries.

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

[0005] In addition, the reduction of particle size can also bring about an improvement in low-temperature performance. Ionic conductivity usually decreases significantly with decreasing temperature, especially at grain boundaries. The increase in grain boundaries brought about by particle size reduction can partially compensate for the decrease in the grain boundary ion transport rate at low temperatures, improving the low-temperature performance of the battery. For example, in a low-temperature environment (such as -20°C, -30°C), all-solid-state batteries using small-sized sulfide electrolytes have a smaller capacity decay, a higher charge and discharge platform voltage, and better low-temperature working performance.

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

[0007] The existing technology for sand grinding and refining sulfide solid electrolytes still faces challenges, with the core lying in solvent selection:

[0008] Insufficient dispersibility: The dispersion effect of traditional solvents is limited, making it difficult to achieve efficient and uniform refinement;

[0009] Compatibility issues: The solvent needs to avoid adverse reactions with sulfide electrolytes;

[0010] Balance between efficiency and performance: Excessive grinding may damage the material structure and reduce performance;

[0011] Lack of a dedicated optimized solvent system: The existing solvent selection lacks systematicness and is difficult to fully meet the refinement requirements. There is an urgent need for a dedicated solvent system to break through the bottleneck.

[0012] To effectively address the challenges faced by the existing technology in the sand grinding and refining 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 grinding and refining process of sulfide solid electrolytes. The core innovative concept of the present invention is: abandoning the idea of simple mixing of traditional solvents, but instead cleverly utilizing the π-π stacking interaction existing 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 grinding and refining efficiency and product performance of sulfide solid electrolytes.

[0013] Compared with the traditional solvents or simply mixed solvents commonly used in the existing technology, the composite solvent system based on π-π stacking self-assembly proposed by the present invention exhibits the following potential significant advantages in the application of sand grinding and refining of sulfide solid electrolytes:

[0014] Significantly enhance the dispersibility 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 the solvent, and laying a foundation for efficient sand grinding and refining.

[0015] Greatly improve the sand grinding and refining efficiency: The solvent system regulated by π-π stacking self-assembly, with its optimized solvent properties, may effectively enhance the energy transfer efficiency between the grinding medium and sulfide particles, improve the utilization rate of grinding energy, thereby achieving a faster refinement speed, shorter grinding time, and smaller final particle size under the same sand grinding process conditions, and greatly improving the sand grinding and refining efficiency.

[0016] The solvent system design has strong flexibility and controllability: The type, strength, and self-assembled structure of π-π stacking can be achieved through the selection of solvent component types and precise regulation of ratios, which provides a broad design space and flexible regulation means for developing customized sanding and refining solvent systems for sulfide solid electrolyte materials with different chemical systems and different performance requirements. Summary of the Invention

[0017] In view of this, the present invention aims to provide a method for refining solid electrolytes based on π-π stacking self-assembled composite aprotic solvents and its applications. Through the π-π stacking interaction between solvent molecules, this solvent system forms self-assemblies with specific structures, which can efficiently disperse and refine sulfide solid electrolytes, improve the refining efficiency and uniformity, and protect the material properties.

[0018] Although reducing the particle size can improve the performance of electrolytes, and conventional refining treatments (such as sanding and ball milling) can also refine electrolytes to a D50 particle size of about 500 nm, a long sanding time (more than 10 h) is required. However, the long sanding time will damage the crystal structure of the electrolyte, resulting in a significant decrease in ionic conductivity, which will greatly offset the improvement effect brought by the reduced 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 D50 particle size of the obtained powder about 500 nm within a short sanding time (within 2 h), while also reducing the damage to the crystal structure (protective effect and short sanding time), with less decrease in ionic conductivity. In later applications, the refined electrolytes have more advantages in overall performance.

[0019] The present invention innovatively combines the constant-temperature and low-temperature process conditions with the π-π stacking self-assembled composite solvent system and cleverly introduces 1,8-naphthalenedicarboximide as an additive to construct a more efficient and stable solution for sanding and refining sulfide solid electrolytes. The constant-temperature and low-temperature and π-π stacking self-assembly are not simply superimposed but produce a significant synergistic effect, jointly enhancing the protection and refining effects on sulfide electrolytes at the molecular level and macroscopic level. The π-π stacking self-assembled structure of the present invention enhances the solvation effect and improves the dispersibility. The D50 of the refined sulfide particle size is reduced by 50% compared with traditional refining, and the ionic conductivity of the sulfide fine powder increases by about 1000%.

[0020] Potential advantages of π-π stacking self-assembly in the refinement of solid electrolytes compared to hydrogen bond self-assembly: (1) Stronger structural stability and controllability: π-π stacking: The strength of π-π interactions can be more precisely regulated 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 more stable and robust layered structures, which may more effectively resist shear and impact forces during the sanding process, maintain the integrity of the solvent system, thereby continuously exerting a dispersing effect, and is also more conducive to the protection of crystal structures. (2) Hydrogen bond self-assembly: The strength of hydrogen bonds is relatively weak and is easily broken by environmental factors (such as trace moisture, temperature). Although hydrogen bonds have a high degree of directionality and can form specific structures, in a severe sanding environment, the self-assembled structures formed by them may not be as stable as those formed by π-π stacking.

[0021] 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 15 °C constant temperature can fundamentally slow down the thermal motion of solvent molecules. The weakening of molecular thermal motion significantly reduces the kinetic energy that destroys intermolecular interactions, and is more conducive to the efficient formation and stable existence of π-π stacking interactions between tetrathiafulvalene (TTF) and hexafluorobenzene molecules. Thus, the "molecular-level hydrophobic barrier" structure formed by π-π stacking self-assembly will be denser, more ordered, and more stable, laying a solid foundation for subsequent dispersion and protection mechanisms.

[0022] In the present invention, we fix the parameters of the π-π donor solvent and the π-π acceptor solvent at an optimal ratio of 1:5 (molar ratio) to ensure the maximization of the π-π stacking interaction strength and the optimization of the self-assembled structure.

[0023] To further enhance the effect of π-π stacking self-assembly, the present invention innovatively introduces 1,8-naphthalenedicarboximide as an additive, and cleverly utilizes the unique structural characteristics of 1,8-naphthalenedicarboximide molecules to exert its multiple synergistic effects:

[0024] (1) Construction of a two-way π-π stacking complementary network: 1,8-naphthalenedicarboximide molecules have both an electron-rich region (HOMO orbital) and an electron-deficient region (LUMO orbital).

[0025] Electron-rich region (HOMO orbital): The imide group of 1,8-naphthalenedicarboximide 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;

[0026] Electron-deficient region (LUMO orbital): The planar conjugated skeleton of 1,8-naphthalenedicarboximide can act as a π-π acceptor, forming an inverse π-π interaction with the electron-rich aromatic ring of tetrathiafulvalene (TTF). Thus, 1,8-naphthalenedicarboximide becomes a key "bridge" and "crosslinking node" in the π-π stacking network, jointly constructing a two-way charge-complementary π-π stacking network with TTF and hexafluorobenzene, significantly enhancing the overall density and strength of the π-π stacking, and improving the efficiency and orderliness of solvent self-assembly.

[0027] (2) Dynamic template-directed layered supramolecular structure: The planar structure of 1,8-naphthalenedicarboximide can serve as a molecular template to guide the ordered stacking of TTF and hexafluorobenzene molecules on both sides of it. Through the "sandwich-type" stacking mode (TTF-1,8-naphthalenedicarboximide-hexafluorobenzene), a highly ordered layered supramolecular structure is induced to form. This layered superstructure can significantly enhance the wettability of the solvent aggregates to sulfide particles, improve the penetration ability of solvent molecules into the particle gaps, thereby more efficiently disintegrating particle agglomeration and increasing the dispersion efficiency.

[0028] (3) Interface charge regulation to enhance dispersion stability: 1,8-Naphthalenedicarboximide molecules have strong electron affinity and are easily adsorbed on the surface of sulfide particles. Through surface dipole interaction, 1,8-naphthalenedicarboximide can effectively neutralize some of the charges on the surface of sulfide particles, reduce the electrostatic repulsion or attraction between particles, and significantly weaken the aggregation forces such as van der Waals forces, thus fundamentally reducing the tendency of fine powder agglomeration and greatly improving the long-term stability of the dispersion system.

[0029] To achieve the above object, the technical solution adopted in the present invention is as follows:

[0030] <First aspect>

[0031] The present invention provides a method for refining a solid-state electrolyte based on π-π stacking self-assembly composite aprotic solvent, comprising the following steps:

[0032] S1. Mix tetrathiafulvalene (TTF) and 1,8-naphthalenedicarboximide (additive) and dissolve them in hexafluorobenzene to obtain a composite aprotic solvent;

[0033] S2. Add the sulfide solid-state electrolyte to the composite aprotic solvent, perform sanding treatment, and dry the obtained slurry to obtain the refined sulfide solid-state electrolyte powder.

[0034] 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.

[0035] As an embodiment of the present invention, in step S1, the content of 1,8-naphthalenedicarboximide in the composite aprotic solvent is 0.4 - 0.6 wt%, preferably 0.5 wt%. 1,8-Naphthalenedicarboximide is used to enhance the π-π stacking density and the orderliness of the solvent layer structure.

[0036] As an embodiment of the present invention, in step S1, the temperature during dissolution is 65 - 75 °C, preferably 70 °C. Stirring is carried out 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 realizes the uniform dispersion of TTF by heating to 60 - 80 °C.

[0037] 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.

[0038] As an embodiment of the present invention, in step S2, the temperature of the sanding treatment is 10 - 20 °C, preferably 14 - 16 °C, and more preferably 15 °C. The sanding and refining process is carried out under the protection of an inert atmosphere, and the grinding temperature is controlled below room temperature.

[0039] As an embodiment of the present invention, in step S2, the solid-liquid ratio of the sanding treatment (sulfide solid electrolyte: composite refining solvent) is 1:8 - 12 (g / mL), preferably 1:10.

[0040] As an embodiment of the present invention, in step S2, the filling amount during the sanding treatment is 60% - 80% (volume ratio). The grinding medium for the sanding treatment is zirconia beads with a particle size of 0.1 - 1 mm.

[0041] As an embodiment of the present invention, in step S2, the rotation speed of the sanding treatment is 1000 - 2000 rpm, and the time is 30 - 120 min; the time is preferably 40 - 80 min. The sanding and refining process is preferably carried out using a horizontal sand mill.

[0042] As an embodiment of the present invention, in step S2, the drying temperature is 340 - 380 °C, preferably 360 °C, and the time is 10 - 14 h, preferably 12 h. The drying is vacuum drying.

[0043] The vacuum drying temperature of the present invention is about 360 °C. At this temperature, TTF will volatilize, leaving only the refined electrolyte. However, there may be a small probability of residual TTF. The π-π stacking characteristics of this part of TTF help to form a certain connection between the electrolyte particles, improve the contact between the particles, and thus reduce the interfacial impedance.

[0044] 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.

[0045] The present application also provides an application of the above solid electrolyte refinement method in the preparation of solid-state batteries.

[0046] Compared with the all-solid-state lithium metal batteries in the prior art, the beneficial effects of the present invention are as follows:

[0047] (1) High-efficiency refinement effect of sulfide electrolyte: The constant-temperature low-temperature synergistic π-π stacking self-assembly composite solvent system of the present invention can achieve faster and more thorough refinement of sulfide electrolyte, with smaller particle size (D50 as low as 550 nm) and narrower particle size distribution. This is mainly due to the significant improvement in the solvent dispersion ability of the π-π stacking self-assembly structure.

[0048] (2) Significantly improve the performance of sulfide electrolyte: The sulfide electrolyte refined by the method of the present invention exhibits higher ionic conductivity (up to 10 mS / cm at most, a 120% increase compared to the traditional solvent system). This is mainly attributed to the more uniform particle size distribution and significantly improved interfacial contact, both of which are closely related to the efficient dispersion and low-temperature synergistic protection mechanism of the π-π stacking self-assembly solvent system.

[0049] (3) The solvent system is easy to prepare, simple to operate, and has industrial application prospects: The composite solvent system of the present invention has simple and easily available components, the preparation process is simple and controllable, and the process parameters of sanding refinement are easy to adjust and optimize, showing good industrial amplification and practical application prospects. Description of the Drawings

[0050] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes, and advantages of the present invention will become more obvious:

[0051] Figure 1 Particle size distribution diagram of the refined sulfide electrolyte for Example 1;

[0052] Figure 2 Particle size distribution diagram of the refined sulfide electrolyte for Comparative Example 1;

[0053] Figure 3 Comparison diagram of the bulk impedance diagrams of the refined sulfide electrolytes of Example 1 and Comparative Example 1. Detailed Embodiments

[0054] The present invention will be 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 do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, several adjustments and improvements can be made without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0055] The core of the composite solvent system of the present invention lies in realizing solvent self-assembly by using π-π stacking interactions. The component selection and action mechanism are as follows:

[0056] Principle for constructing the 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 interactions to form a composite solvent system with a π-π stacking self-assembly structure. The π-π stacking self-assembly structure endows the composite solvent system with unique properties, making it more suitable for the sanding and refinement of sulfide electrolytes.

[0057] Selection of aprotic organic solvents with aromatic ring structures: To construct the π-π stacking self-assembly composite solvent system, the present invention preferably selects aprotic organic solvents with aromatic ring structures as components.

[0058] π-π stacking donor (π-Donor): Tetrathiafulvalene (TTF) is selected as the π-π stacking donor. The tetrathiafulvalene molecule has a highly symmetric electron-rich aromatic ring structure, with a high π electron cloud density and strong π electron donor ability, and can effectively provide π electrons to have a strong interaction with the π-π stacking acceptor solvent.

[0059] π-π stacking acceptor (π-Acceptor): Hexafluorobenzene is selected as the π-π stacking acceptor. Six strongly electron-withdrawing fluorine atoms are introduced into the molecular structure of hexafluorobenzene, significantly reducing the π electron cloud density of the aromatic ring and having strong π electron acceptor ability, and can effectively accept π electrons to form a stable π-π stacking interaction with the π-π stacking donor solvent.

[0060] π-π stacking self-assembly mechanism of the tetrathiafulvalene + hexafluorobenzene composite solvent system: There is a significant electron density difference between tetrathiafulvalene (π-Donor) and hexafluorobenzene (π-Acceptor). After they are mixed in a molar ratio of 1:5, through strong π-π stacking interactions, they spontaneously form an ordered molecular aggregate. This aggregate is not randomly stacked, but is driven by π-π stacking interactions 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 with each other, and the π-π stacking interaction runs through the entire solvent system, constructing a unique and functionalized composite solvent microenvironment.

[0061] Advantages brought by π-π stacking self-assembly structure:

[0062] Constructing an efficient layered solvent microenvironment to enhance penetration and solvation: π-π stacking self-assembly constructs a unique layered solvent microenvironment around sulfide electrolyte particles. The layered microenvironment has an "interlayer channel" effect, which is conducive to the faster and deeper penetration of solvent molecules into the gaps and interiors of sulfide particles, significantly enhancing solvation, thereby more effectively reducing the agglomeration force between particles and improving the dispersion efficiency.

[0063] Precisely regulating 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 make it more compatible with the surface properties of sulfide electrolytes, 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 grinding media and the circulation of materials, and improve the sanding efficiency. At the same time, an appropriate viscosity is also conducive to maintaining the stability of the dispersion system, preventing particle sedimentation and re-agglomeration.

[0064] Enhancing the dispersion stability: The layered solvent microenvironment may form a protective layer on the surface of sulfide particles to prevent direct contact and agglomeration of particles, improving the dispersion stability.

[0065] Example 1

[0066] This example aims to provide a composite solvent system based on π-π stacking self-assembly and innovatively introduce 1,8-naphthalenedicarboximide additive to prepare refined sulfide solid electrolytes more efficiently and stably. The sulfide electrolyte used in this example 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-naphthalenedicarboximide.

[0067] The method for preparing refined sulfide electrolytes using the composite solvent system based on π-π stacking self-assembly includes the following steps:

[0068] S1. Preparation of a composite solvent system containing 1,8-naphthalenedicarboximide additive (tetrathiafulvalene + hexafluorobenzene + 1,8-naphthalenedicarboximide):

[0069] (1)Accurate weighing of solid components: In a dry glove box, accurately weigh analytical pure solid tetrathiafulvalene (TTF) and solid 1,8-naphthalenedicarboximide, and place them in a dry and clean beaker according to the preset molar ratio and weight ratio (the molar ratio of tetrathiafulvalene to hexafluorobenzene is 1:5, and the addition amount of 1,8-naphthalenedicarboximide is 0.5 wt% of the total weight of the composite solvent system).

[0070] (2)Addition and mixing of liquid components: Use a pipette to accurately measure liquid hexafluorobenzene and add it to the beaker containing solid tetrathiafulvalene and 1,8-naphthalenedicarboximide according to the preset molar ratio. The addition order of liquid hexafluorobenzene should be after the solid components to facilitate the full contact and mixing of the solid and liquid components.

[0071] (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-naphthalenedicarboximide in hexafluorobenzene is limited, the beaker can be placed on a heating platform, control the heating temperature at 70 °C, and perform heating magnetic stirring to promote the dissolution of the solid components and accelerate the formation of the π-π stacking self-assembled composite solvent system. The stirring time is controlled at 1.5 hours to ensure the full dissolution of the solid components and the uniform mixing of each component, forming a homogeneous and transparent composite solvent system.

[0072] (4)Preparation environment control: The entire preparation process needs to be carried out in a strictly dry atmosphere (argon atmosphere), and all glassware and measuring tools need to be dried in advance to avoid moisture absorption to the greatest extent and ensure the anhydrous characteristics and purity of the composite solvent system.

[0073] S2. Sanding and refining experiment of sulfide electrolyte:

[0074] (1)Material mixing: Accurately weigh 5 g of sulfide electrolyte powder (Li6PS5Cl), quickly add it to the prepared [50 mL] tetrathiafulvalene + hexafluorobenzene composite solvent containing 1,8-naphthalenedicarboximide additive, and control the solid-liquid ratio to be [1:10 (g / mL)].

[0075] (2)Sanding and refining: Quickly transfer the mixed material to the grinding cylinder of the RTSM-AJ horizontal sand mill. The grinding medium is selected as zirconia beads with a particle size of 0.5 mm, and the filling amount is controlled at 70% (volume ratio). Set the rotation speed of the sand mill to 1500 rpm and the grinding time to 60 minutes.

[0076] (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.

[0077] (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 1 As 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.

[0078] (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.

[0079] Example 2

[0080] 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.

[0081] Example 3

[0082] 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).

[0083] Comparative Example 1

[0084] This comparative example provides a composite solvent system that does not self-assemble based on π-π stacking, its use in the sanding and refinement of sulfide solid electrolytes, and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (the same as in the implementation example, using the same batch of high-purity Li6PS5Cl powder with a consistent particle size distribution. The operations are all carried out in a dry inert atmosphere), and the solvent is hexafluorobenzene (99%, Sigma-Aldrich). The difference from the implementation example 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.

[0085] S1. Mixing of sulfide electrolyte powder and solvent:

[0086] Same as the implementation example, 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). Place the mixture in a grinding cup and stir magnetically for 30 minutes for preliminary dispersion.

[0087] S2 is the same as Example 1.

[0088] The particle size distribution of the refined sulfide electrolyte powder is as Figure 2 shown, and the bulk impedance is as Figure 3 shown.

[0089] Comparative Example 2

[0090] This comparative example provides a composite solvent system based on π-π stacking self-assembly, its use in the sanding and refinement of sulfide solid electrolytes, and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (the same as in Example 1 and Comparative Example 1, using the same batch of high-purity Li6PS5Cl powder with a consistent particle size distribution, and the operations are all carried out in a dry inert atmosphere), and the solvent (tetrathiafulvalene (donor) + DMF (acceptor)) (99%, Sigma-Aldrich).

[0091] S1. Preparation of mixed solvent:

[0092] (1) Accurate weighing of solid components: In a dry glove box, accurately weigh analytical pure solid tetrathiafulvalene (TTF) and solid 1,8-naphthalenedicarboximide, and place them in a dry and clean beaker according to the preset molar ratio and weight ratio (the molar ratio of tetrathiafulvalene to DMF is 1:5, and the addition amount of 1,8-naphthalenedicarboximide is 0.5 wt% of the total weight of the composite solvent system).

[0093] (2) Addition and mixing of liquid components: Use a pipette to accurately measure the liquid DMF and add it to a beaker containing solid tetrathiafulvalene and 1,8-naphthalenedicarboximide according to the preset molar ratio. The liquid DMF should be added after the solid components to facilitate full contact and mixing between the solid and liquid components.

[0094] The parameters of other steps are the same as those in Example 1.

[0095] Comparative Example 3

[0096] This comparative example provides a composite solvent system based on π-π stacking self-assembly and its use in the sanding and refinement of sulfide solid electrolytes and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (the same as in the implementation example and Comparative Example 1, using high-purity Li6PS5Cl powder of the same batch and consistent particle size distribution. The operations are all carried out in a dry inert atmosphere.), and the solvent is (tetrathiafulvalene (donor) + DMP (acceptor)) (99%, Sigma-Aldrich).

[0097] S1. Preparation of mixed solvent:

[0098] (1) Accurate weighing of solid components: In a dry glove box, accurately weigh analytical pure solid tetrathiafulvalene (TTF) and solid 1,8-naphthalenedicarboximide, and place them in a dry and clean beaker according to the preset molar ratio and weight ratio (the molar ratio of tetrathiafulvalene to DMP is 1:5, and the addition amount of 1,8-naphthalenedicarboximide is 0.5 wt% of the total weight of the composite solvent system).

[0099] (2) Addition and mixing of liquid components: Use a pipette to accurately measure the liquid DMP and add it to a beaker containing solid tetrathiafulvalene and 1,8-naphthalenedicarboximide 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.

[0100] The parameters of other steps are the same as those in Example 1.

[0101] Comparative Example 4

[0102] This comparative example provides a composite solvent system based on π-π stacking self-assembly and its use in the sanding and refinement of sulfide solid electrolytes and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (the same as in the implementation example and Comparative Example 1, using high-purity Li6PS5Cl powder of the same batch and consistent particle size distribution, and the operations are all carried out in a dry inert atmosphere), and the solvent is (toluene (donor) + hexafluorobenzene (acceptor)) (99%, Sigma-Aldrich).

[0103] S1. Preparation of mixed solvent:

[0104] In an inert atmosphere glove box, precisely 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. Precisely weigh analytical pure solid 1,8-naphthalenedicarboximide, and place it in a dry and clean beaker according to the preset weight ratio (the addition amount of 1,8-naphthalenedicarboximide is 0.5 wt% of the total weight of the composite solvent system).

[0105] The other step parameters are the same as those in Example 1.

[0106] Comparative Example 5

[0107] This comparative example provides a composite solvent system based on π-π stacking self-assembly and its method for sanding and refining a sulfide solid electrolyte and its preparation. The sulfide electrolyte used in this comparative example is Li6PS5Cl (the same as in the implementation example and Comparative Example 1, using the same batch of high-purity Li6PS5Cl powder with a consistent particle size distribution, and the operations are all carried out in a dry inert atmosphere), and the solvent is (o-xylene (donor) + hexafluorobenzene (acceptor)) (99%, Sigma-Aldrich).

[0108] S1. Preparation of the mixed solvent:

[0109] In an inert atmosphere glove box, precisely 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. Precisely weigh analytical pure solid 1,8-naphthalenedicarboximide, and place it in a dry and clean beaker according to the preset weight ratio (the addition amount of 1,8-naphthalenedicarboximide is 0.5 wt% of the total weight of the composite solvent system).

[0110] The other step parameters are the same as those in Example 1.

[0111] Comparative Example 6

[0112] 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 those in Example 1.

[0113] Performance Test Example

[0114] Measure the AC impedance values of the refined sulfide electrolytes prepared in the above examples and comparative examples using an electrochemical workstation, and calculate the ionic conductivity. The calculation formula is σ = L / RS. Where 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 the examples and comparative examples, 120 mg of the electrolyte was weighed and pressed into a tablet, and all were pressed into a thin sheet with an area of 0.785 cm 2 and a thickness of 1 mm. Then, the bulk impedance (R) of the electrolyte was measured. The bulk impedance of different electrolyte sheets was measured using electrochemical impedance spectroscopy (EIS) on an Es-Lab. Two stainless steels (SS) were used as blocking electrodes, and the measurement was carried out at room temperature in the frequency range of 7000 kHz - 100 mHz and with an AC amplitude of 10 mV. The sulfide electrolyte was dispersed using analytical pure, anhydrous, and dry dispersant (acetonitrile), and the particle size was measured using a laser particle size analyzer. The results are shown in Table 1 below:

[0115] Table 1 Ionic Conductivity

[0116]

[0117] 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 sanding and refinement of sulfide electrolytes, with limited performance improvement and even deterioration. Although the particle size in the comparative examples decreased to some extent, the increase in ionic conductivity was not obvious, and some even decreased, indicating that simple solvent mixing is difficult to effectively solve the dispersion problem and cannot improve the material performance. The reason may be the lack of regulation of the solvent microstructure. The solvent optimization only stays at the macroscopic level and cannot conduct fine performance regulation at the molecular level.

[0118] In contrast, the tetrathiafulvalene + hexafluorobenzene + 1,8-naphthalenedicarboximide π-π stacking self-assembled composite solvent system innovatively proposed in the present invention (Example 1) exhibits excellent performance and breakthrough refinement effect by virtue of its unique π-π stacking self-assembled structure and the synergistic enhancement effect of the 1,8-naphthalenedicarboximide additive. Table 1 shows that Example 1 not only significantly refined the particle size (D50 decreased from 8 µm to 550 nm), but also improved the ionic conductivity (increased from 2 mS / cm to 10 mS / cm), with the best comprehensive performance. In particular, by comparing Example 1 (containing 1,8-naphthalenedicarboximide) and Comparative Example 6 (the same solvent system without 1,8-naphthalenedicarboximide), it was found that although the particle size of Comparative Example 6 was similar to that of Example 1 (both were 550 nm), the ionic conductivity was only 8 mS / cm, far lower than 10 mS / cm of Example 1, strongly proving that the 1,8-naphthalenedicarboximide additive is the key to performance improvement, and its introduction significantly enhances the advantages of π-π stacking self-assembly, improving the dispersion effect and performance. The experimental comparative analysis incontrovertibly confirms that the π-π stacking self-assembled composite solvent system of the present invention, especially the introduction of the 1,8-naphthalenedicarboximide additive, can more effectively optimize the dispersion, greatly improving the refinement efficiency and material performance. The distinct contrast between Example 1 and other comparative examples (especially Comparative Example 6) highlights the excellent advantages and application value of the "π-π stacking self-assembly" strategy, strongly verifying the uniqueness and breakthrough of the technical solution of the present invention, and indicating its broad prospects in the field of high-performance solid-state batteries.

[0119] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications 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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