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

Abstract

The invention discloses a solid electrolyte refining method based on a hydrogen bond self-assembly composite aprotic solvent and application of the solid electrolyte refining method. The composite aprotic solvent system is composed of acetonitrile and tetramethylurea, and solvent molecules are driven to be self-assembled to form the ordered aggregate through the interaction of C-H... O type weak hydrogen bonds between a nitrile group (C = N) and a carbonyl group (C = O). In order to further enhance the hydrogen bond network and improve the stability of the electrolyte, (2, 4, 6-tri (3, 4, 5-trifluorophenyl) boroxane is introduced into the system as an additive, the additive and solvent molecules form a synergistic hydrogen bond through the electron deficiency characteristic of a B-O bond, a three-dimensional supramolecular network is constructed, and meanwhile particle aggregation is inhibited through the dynamic template effect. Experiments show that by adding the cyclic boroxane into the composite aprotic solvent, the sulfide powder D50 can be reduced to 500nm, the ionic conductivity can be improved by more than 300%, and an innovative solution is provided for the development of high-performance solid-state batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a solid-state electrolyte refinement method based on hydrogen bond self-assembly composite aprotic solvent and an application thereof, which are used for sand milling refinement treatment of sulfide solid-state electrolyte materials. Background Art

[0002] All-solid-state batteries have become a key direction for the next generation of battery technology due to their high safety and high energy density potential. Sulfide solid electrolytes are considered to be a solid electrolyte system with great application prospects due to their high ionic conductivity, good ductility and cost advantages.

[0003] In order to improve the performance of sulfide solid electrolytes, refinement is essential. Refinement can increase the specific surface area, improve grain boundary contact, optimize the electrode / electrolyte interface, and ultimately improve ionic conductivity, battery performance, and electrolyte membrane quality. Particle size distribution and dispersibility directly affect the rheology of the slurry, which in turn affects processing and production.

[0004] As a highly efficient wet ultrafine grinding technology, sand milling technology has the advantages of efficient refinement, controllable particle size, continuous production and wet operation. It shows great potential in the preparation of sulfide solid electrolyte powders and can meet the requirements of high-performance materials for particle size and uniformity.

[0005] 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.

[0006] Compatibility issues: Solvents need to avoid adverse reactions with sulfide electrolytes.

[0007] Balance between efficiency and performance: Excessive grinding may damage the material structure and reduce performance.

[0008] 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.

[0009] The present invention innovatively proposes a composite aprotic solvent system based on hydrogen bond self-assembly for sand milling of sulfide electrolytes. The core innovation is to use hydrogen bond self-assembly to control solvent properties rather than simple mixing.

[0010] The present invention has the following potential advantages: Stronger dispersibility: Hydrogen bond self-assembly structure enhances solvation and improves dispersibility.

[0011] Higher refinement efficiency: Optimizing solvent properties to improve energy transfer efficiency.

[0012] Better performance protection: Gentle thinning process reduces structural damage.

[0013] The solvent system is highly designable: solvents can be customized for different sulfide systems.

[0014] The present invention is expected to break through the bottleneck of existing sulfide solid electrolyte sand grinding and refinement technology, and provide key technical support for high-performance all-solid-state batteries. Summary of the invention

[0015] In view of this, the purpose of the present invention is to provide a solid electrolyte refinement method based on hydrogen bond self-assembly composite aprotic solvent and its application. The solvent system used in the method forms a self-assembly with a specific structure through hydrogen bond interaction between solvent molecules, so that the sulfide solid electrolyte can be more effectively dispersed and refined, the sand milling refinement efficiency and uniformity can be improved, and finally the performance of the sulfide electrolyte material can be improved.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The hydrogen bond self-assembly structure of the present invention enhances solvation and improves dispersibility. The particle size D50 of the sulfide after refinement is reduced by 50% compared with the traditional refinement, and the ionic conductivity of the sulfide fine powder is increased by about 300%.

[0020] The core of the present invention is to construct a composite aprotic solvent system based on hydrogen bond self-assembly. The solvent system is composed of at least two aprotic solvent components, and the solvent components can self-assemble through hydrogen bond interactions to form a composite solvent system with a hydrogen bond self-assembly structure. This hydrogen bond self-assembly structure gives the composite solvent system unique properties, making it more suitable for sand milling and refining of sulfide electrolytes.

[0021] Hydrogen bond self-assembly mechanism: Acetonitrile contains a nitrile group (-CN) in its molecular structure, which can act as a hydrogen bond acceptor (HBA). The molecular structure of tetramethyl urea contains a carbonyl group (C=O) and four methyl-substituted nitrogen atoms. The carbonyl group can act as a hydrogen bond donor (HBA). The methyl substitution on the nitrogen atom of the amide group weakens its hydrogen bond donor ability, but tetramethyl urea can still form a weak hydrogen bond interaction of the O···HC type (CH···O hydrogen bond) with the adjacent acetonitrile molecule through the carbonyl oxygen atom. In addition, the tetramethyl urea molecule itself also has a certain dipole moment, which promotes self-assembly through dipole-dipole interactions. Importantly, this composite solvent system is not a simple mixture, but is driven by intermolecular hydrogen bonds (and possible dipole effects) to form a dynamic solvent aggregate with a certain structure. This aggregate structure may change the polarity, viscosity, surface tension and other properties of the solvent, making it more suitable for the dispersion and refinement of sulfide electrolytes. At the same time, it can protect the crystal structure of the solid electrolyte and avoid being destroyed during the refinement process, and the integrity of the crystal structure can improve the conductivity.

[0022] Regulation of solvent polarity: The introduction of tetramethylurea may fine-tune the polarity of acetonitrile, making it more suitable for interaction with the sulfide electrolyte surface and enhancing the solvation ability.

[0023] Changing solvent viscosity and surface tension: Hydrogen bond self-assembly may lead to a slight increase in the viscosity of the solvent system and a decrease in the surface tension, which may be conducive to the formation of a more uniform liquid film during sand milling and improve the dispersion efficiency.

[0024] Constructing a solvation layer: The solvent aggregates formed by self-assembly may form a more effective solvation layer on the surface of sulfide electrolyte particles, preventing particle agglomeration and improving dispersion stability.

[0025] Hydrogen bond self-assembly and additive synergistic mechanism: Optimization of the composite solvent system: The molar ratio of acetonitrile to tetramethylurea (8:2) formed dynamic self-assembled aggregates through CH···O hydrogen bonds, which reduced the solvent surface tension and improved the dispersion efficiency.

[0026] Introduction of cyclic boroxane: (1) Hydrogen bond synergy: The BO bond of boroxane acts as a strong hydrogen bond acceptor, forming a BO···HC≡N bond with acetonitrile C≡N. At the same time, the rigid ring structure induces the directional arrangement of the carbonyl group of tetramethyl urea, and the hydrogen bond density can be improved.

[0027] (2) Interface stabilization: Boroxane is adsorbed on the surface of sulfide particles through host-guest interaction. The hydrophobic group (trifluorophenyl) reduces the interaction between particles, and the polar BO group guides the orderly arrangement of the solvent, which can further improve the refinement efficiency.

[0028] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The present application provides a solid electrolyte refinement method based on hydrogen bond self-assembly composite aprotic solvent, comprising the following steps: S1, mixing tetramethyl urea and acetonitrile according to a molar ratio to obtain a composite aprotic solvent; S2, adding 2,4,6-tris(3,4,5-trifluorophenyl)boroxine (additive), and performing ultrasonic dispersion to obtain a composite refinement solvent; S3, adding the sulfide solid electrolyte into the composite refining solvent, performing sand milling, and drying the obtained slurry to obtain the refined sulfide solid electrolyte powder.

[0029] As an embodiment of the present invention, in step S1, the preparation process of the composite aprotic solvent needs to be carried out in a dry atmosphere (argon) to avoid moisture absorption.

[0030] As an embodiment of the present invention, in step S1, the molar ratio of tetramethylurea to acetonitrile is 75-85:15-25, preferably 8:2.

[0031] As an embodiment of the present invention, in step S2, the amount of 2,4,6-tris(3,4,5-trifluorophenyl)boroxine added is 0.1-1.0 wt%, preferably 0.5 wt%, of the composite aprotic solvent. The small amount of 2,4,6-tris(3,4,5-trifluorophenyl)boroxine added has a synergistic effect with the composite aprotic solvent: (1) it acts as a hydrogen bond cross-linking node to form a BO···HC≡N bond with the C≡N group of acetonitrile; (2) it induces the directional arrangement of the carbonyl groups of tetramethyl urea to form a three-dimensional hydrogen bond network enhanced by CH···O bonds; (3) it reduces the van der Waals force between sulfide particles through the hydrophobic group to inhibit agglomeration.

[0032] As an embodiment of the present invention, in step S2, the ultrasonic dispersion time is 20-40 min, preferably 30 min. The ultrasonic dispersion is carried out under argon protection.

[0033] As an embodiment of the present invention, in step S3, the temperature of the sand grinding treatment is 8-12°C, preferably 10°C.

[0034] The sand mill cooling system is set at a constant low temperature of about 10°C to ensure stable temperature throughout the sand milling process. Low temperature is conducive to the formation and stability of the hydrogen bond self-assembly structure of tetramethylurea and acetonitrile. At this temperature, the thermal motion of tetramethylurea and acetonitrile molecules is weakened, which is conducive to the interaction between the two molecules, thereby enhancing the self-assembly effect and improving the dispersion ability of the composite solvent system.

[0035] As an embodiment of the present invention, in step S3, the sulfide solid electrolyte includes one or more of Li2S-P2S5-based, Li2S-GeS2-based, and Li2S-SiS2-based sulfide solid electrolytes.

[0036] As an embodiment of the present invention, in step S3, the solid-liquid ratio (sulfide solid electrolyte: composite refinement solvent) of the sand milling treatment is 1:8-12 (g / mL), preferably 1:10.

[0037] As an embodiment of the present invention, in step S3, the filling amount during sand milling is 60%-80%. The grinding medium for sand milling is zirconium oxide beads with a particle size of 0.1-1 mm.

[0038] As an embodiment of the present invention, in step S3, the rotation speed of the sand grinding treatment is 1000-2000 rpm, and the time is 30-120 min; preferably, the time is 40-80 min.

[0039] As an embodiment of the present invention, in step S3, the drying temperature is 50-70°C, preferably 60°C, the drying time is 10-14h, preferably 12h. The drying is vacuum drying.

[0040] As an embodiment of the present invention, in step S3, the D50 particle size of the refined sulfide solid electrolyte powder is 400-600 nm.

[0041] The present application also provides an application of the refinement method in the preparation of solid-state batteries.

[0042] Compared with the all-solid-state lithium metal battery in the prior art, the beneficial effects of the present invention are: (1) More efficient and uniform sulfide electrolyte refinement effect: Compared with traditional solvents or simple mixed solvents, the composite solvent system of the present invention can achieve smaller and more uniform particle size distribution. This is attributed to the optimization and regulation of the solvent properties by the hydrogen bond self-assembly structure.

[0043] (2) Significantly improve the performance of sulfide electrolytes: The refined sulfide electrolytes show higher ionic conductivity, which is due to the more uniform particle size distribution and improved inter-particle contact, which are closely related to the effective dispersion of the hydrogen bond self-assembly solvent system.

[0044] (3) Gentle refinement process to better protect the structure of sulfide electrolytes: Based on the solvent system of hydrogen bond self-assembly, the force is mild and controllable, avoiding the side reactions or structural damage that may be introduced by traditional solvents. It is beneficial to maintain the chemical integrity and stability of sulfide electrolyte materials.

[0045] (4) The solvent system is easy to prepare, simple to operate, and has prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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

[0047] 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.

[0048] Conventional particle powders, such as graphite, carbon, metal, and alloy, are chemically stable, inert to water and common organic solvents, almost insoluble in common organic solvents, insensitive to structural defects, and have relatively stable conductivity. When refining, the main issue is size control, and the influence of the refining solvent is relatively small.

[0049] The refined sulfide solid electrolytes of the present invention, such as Li6PS5Cl, have significant differences in chemical and physical properties from graphite particles, which leads to completely different problems faced by them during the sand milling and refining process. Sulfide solid electrolyte particles have high surface energy, are easy to agglomerate, are difficult to disperse, and may have a certain solubility in some organic solvents. In addition, they have poor chemical stability, are sensitive to water and protic solvents, are easily hydrolyzed and decomposed, and solvent selection is limited. Since the ionic conductivity of sulfide solid electrolytes is sensitive to changes in crystal structure, mechanical force, and chemical environment, and these factors are affected by sand milling conditions and solvents, the performance of sulfide electrolytes is more susceptible to sand milling conditions and solvents.

[0050] For sulfide solid electrolytes, the following types of hydrogen bonding interactions need to be considered when selecting aprotic solvent components for constructing hydrogen-bonded self-assembly composite solvent systems: Hydrogen Bond Donor (HBD): refers to a solvent containing a group that can provide hydrogen atoms in its molecular structure, such as an amide group (-NHCO-), etc. In the present invention, non-protonic HBD solvents can be selected, such as certain urea derivatives, which do not contain active protons but can still serve as hydrogen bond donors.

[0051] Hydrogen Bond Acceptor (HBA): refers to a group in the molecular structure that can accept hydrogen atoms, such as nitrile (-CN), etc. Commonly used aprotic solvents such as acetonitrile can be used as HBA solvents.

[0052] Additives: 2,4,6-tris(3,4,5-trifluorophenyl)boroxine) can promote the formation of hydrogen bonds, increase the density of hydrogen bonds in the solvent, and enhance the effect of the composite solvent.

[0053] The dispersing solvent of sulfide electrolyte needs to comprehensively consider the dispersion effect and performance protection. The tetramethyl urea (TMU) and acetonitrile (ACN) of the present invention, under suitable ratios and under specific temperature conditions, can form a stable hydrogen bond self-assembly structure, which improves the dispersion ability of the composite solvent system while having a certain protective effect on the electrolyte crystal structure, thereby preventing the crystal structure from being destroyed during refinement. Furthermore, boroxane is adsorbed on the surface of sulfide particles through host-guest interaction, the hydrophobic group (trifluorophenyl) reduces the interaction between particles, and the polar BO group guides the orderly arrangement of the solvent, and the refinement efficiency can be further improved.

[0054] Tetramethylurea (TMU) and acetonitrile (ACN) play a role in the following aspects: (1) Avoid proton decomposition reactions The tetramethylurea (TMU) and acetonitrile (ACN) of the present invention are both typical aprotic organic solvents, which do not contain active hydrogen atoms and will not undergo proton decomposition reactions with the sulfide electrolyte. At the same time, in the embodiments of the present invention, it is emphasized to use anhydrous grade TMU and acetonitrile, and take drying measures to minimize the moisture content in the solvent system, effectively avoiding the risk of hydrolysis of the sulfide electrolyte due to the introduction of moisture into the solvent, and ensuring the chemical stability of the sulfide electrolyte.

[0055] The tetramethylurea and acetonitrile of the present invention are superior to water or alcohol solvents. Obviously, protic solvents such as water or alcohols are completely unsuitable for wet refinement of sulfide electrolytes. Even some weakly polar protic solvents may have a certain risk of hydrolysis. The present invention selects non-protic TMU and acetonitrile, which fundamentally avoids the hydrolysis problem caused by protic solvents.

[0056] (2) Does not destroy the crystal structure and plays a protective role The composite aprotic solvent of the present invention can solve the problem of ionic conductivity performance sensitivity: gentle dispersion and protective structure. As aprotic solvents, TMU and ACN have relatively mild solvation capabilities and moderate interaction forces with sulfide electrolytes, and will not excessively erode or destroy the crystal structure of sulfide electrolytes. Compared with some highly polar or corrosive solvents, the TMU and ACN system can provide a milder sanding and refining environment, which can better protect the lattice structure integrity of the sulfide electrolyte while achieving effective dispersion, minimize performance damage caused by mechanical force, and help maintain the high ionic conductivity performance of the sulfide electrolyte.

[0057] The composite aprotic solvent of the present invention is superior to solvents that introduce structural damage: some solvent systems that pursue dispersion effects may have strong solvation ability or corrosiveness, which can improve dispersion efficiency but may also cause irreversible damage to the structure of the sulfide electrolyte, resulting in performance degradation. The TMU / ACN system of the present invention takes into account both dispersion effect and performance protection, achieving a balance between refinement efficiency and performance retention.

[0058] (3) Good dispersion effect The composite aprotic solvent of the present invention has moderate polarity and good dispersibility. Both TMU and ACN are medium polar aprotic solvents with moderate polarity. They can provide a certain solvation effect on the surface of sulfide electrolyte particles, reduce the agglomeration force between particles, and achieve a better dispersion effect, but will not cause excessive solubility in sulfide electrolytes due to excessive polarity. The mixed use of TMU and ACN can further fine-tune the polarity of the solvent system by adjusting the ratio of the two (8:2), optimize the dispersion performance, and make it more suitable for the dispersion requirements of sulfide electrolytes of different systems.

[0059] The composite aprotic solvent of the present invention is superior to non-polar solvents. Although non-polar solvents (such as hexane) can reduce the solubility risk, their dispersion ability is extremely poor and they cannot effectively disperse sulfide electrolytes. The sand milling efficiency is low. The TMU / ACN system of the present invention selects a medium polar solvent and achieves a good balance between solubility and dispersibility.

[0060] (4) Low solubility The composite aprotic solvent of the present invention has low solubility, which can reduce the risk of material loss. The solubility of sulfide electrolytes such as Li6PS5Cl in TMU and ACN is relatively low. During the sand milling process, the dissolution loss of the material can be controlled at a low level, ensuring the product yield.

[0061] Composite aprotic solvents are better than solvents with high solubility. Some highly polar aprotic solvents (such as DMSO and N,N-dimethylformamide (DMF)) may have high solubility for some sulfide electrolytes. Although the dispersion effect may be good, the risk of material dissolution loss is high and it is not suitable for long-term wet sand milling. The TMU / ACN system of the present invention has moderate solubility and is more suitable as a sand milling dispersion medium.

[0062] (5) Introduction of cyclic boroxane additives: The introduction of cyclic boroxane additives can not only form hydrogen bond synergy with acetonitrile through the BO bond as a strong hydrogen bond acceptor and induce the directional arrangement of tetramethylurea carbonyl groups to increase the hydrogen bond density, but also adsorb on the surface of sulfide particles through host-guest interaction, reduce the interaction between particles by hydrophobic groups, and stabilize the interface by guiding the orderly arrangement of the solvent with the help of polar BO groups, ultimately further improving the refinement efficiency.

[0063] Example 1 This embodiment provides a composite solvent system based on hydrogen bond self-assembly and its sand grinding and refinement in a sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this embodiment is Li6PS5Cl (Yili Technology), the hydrogen bond donor solvent is tetramethyl urea (99%, Acros), and the hydrogen bond acceptor solvent is acetonitrile (99%, Adamas).

[0064] The preparation method of the ionic liquid electrowetting modified electrolyte comprises the following steps: S1. Preparation of composite solvent system: Accurately measure analytically pure anhydrous acetonitrile and tetramethylurea, and mix them in a dry beaker according to a specific molar ratio (acetonitrile: tetramethylurea = 8:2). Stir magnetically for 1 hour at room temperature to ensure that tetramethylurea is fully dissolved to form a uniform and transparent composite aprotic solvent system. The preparation process must be carried out in a dry atmosphere (argon) to avoid moisture absorption.

[0065] S2. Introduction of additives: To the composite aprotic solvent prepared in S1, 2,4,6-tris(3,4,5-trifluorophenyl)boroxine (McLean, 99%) additive was added, with a mass of 0.5 wt% of the composite aprotic solvent, and ultrasonic dispersion was performed under argon protection for 30 minutes to obtain a composite refined solvent.

[0066] S3. Sand grinding experiment of sulfide electrolyte: Weigh 5g of sulfide electrolyte powder (Li6PS5Cl) and add it to [50mL] of composite refining solvent, and control the solid-liquid ratio to [1:10 (g / mL)]. Add the mixture to the RTSM-AJ horizontal sand mill, and use zirconia beads as the grinding medium, with a particle size of 5 mm and a filling amount of 70%. Set the sand mill speed to 1500 rpm and the grinding time to 60 minutes. The temperature of the sand milling process is controlled at 10°C. After the sand milling is completed, the grinding medium and the slurry are separated by centrifugation. The slurry is dried at 60°C for 12 hours by vacuum drying to obtain the refined sulfide electrolyte powder with a particle size distribution as shown in Figure 1 As shown, the body impedance is Figure 3 shown.

[0067] Example 2 This embodiment provides a composite solvent system based on hydrogen bond 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 acetonitrile and tetramethyl urea is 5:5.

[0068] Example 3 This embodiment provides a composite solvent system based on hydrogen bond 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).

[0069] Comparative Example 1 This comparative example provides a composite solvent system not based on hydrogen bond 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 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), and the solvent is acetonitrile (99%, Adamas). The difference from the implementation scheme is that this comparative example only uses a single solvent acetonitrile, does not add tetramethyl urea, and does not require the preparation step of the composite solvent.

[0070] Meanwhile, no additives were introduced into this comparative example, and the steps were the same as those of Example 1.

[0071] The particle size distribution of the refined sulfide electrolyte powder is as follows: Figure 2 As shown, the body impedance is Figure 3 As shown. The powder particle size obtained by grinding for 60 minutes in this comparative example is about 900nm, but the ionic conductivity decreases significantly. Although further sand grinding for 10-12h can further reduce the particle size, the electrolyte crystal structure will be further reduced and the conductivity will be worse.

[0072] Comparative Example 2 This comparative example provides a composite solvent system not based on hydrogen bond 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. All operations are carried out in a dry inert atmosphere), and the solvent is a simple mixed solvent (acetonitrile + hexane) (99%, Adamas).

[0073] S1. Preparation of mixed solvent: In an inert atmosphere glove box, accurately measure dry acetonitrile and hexane and mix them in a dry beaker according to the molar ratio (acetonitrile: hexane = 8:2). Stir magnetically for 1 hour at room temperature to form a uniform composite solvent system. The preparation process must be carried out in a dry atmosphere (argon) to avoid moisture absorption.

[0074] Meanwhile, no additives were introduced into this comparative example, and the remaining steps were the same as those of Example 1.

[0075] Comparative Example 3 This comparative example provides a composite solvent system not based on hydrogen bond 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 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), and the solvent is tetramethylurea (99%, Acros). The difference from the implementation scheme is that this comparative example only uses a single solvent tetramethylurea, does not add acetonitrile, and does not require the preparation step of the composite solvent.

[0076] Meanwhile, no additives were introduced into this comparative example, and the remaining steps were the same as those of Example 1.

[0077] Comparative Example 4 This comparative example provides a composite solvent system based on hydrogen bond self-assembly and its sand grinding and refinement in a sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (Yili Technology), and the hydrogen bond acceptor solvent is acetonitrile (99%, Adamas). This comparative example is different from Example 1 in that the hydrogen bond donor solvent is replaced by acetamide (99%, Adamas) from tetramethyl urea (99%, Acros).

[0078] Other preparation method step parameters are the same as in Example 1.

[0079] Comparative Example 5 This comparative example provides a composite solvent system based on hydrogen bond self-assembly and its sand grinding and refinement in a sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (Yili Technology), and the hydrogen bond acceptor solvent is acetonitrile (99%, Adamas). This comparative example is different from Example 1 in that the hydrogen bond donor solvent is replaced by pyrrole (99%, Adamas) from tetramethyl urea (99%, Acros).

[0080] Other preparation method step parameters are the same as in Example 1.

[0081] Comparative Example 6 This comparative example provides a composite solvent system based on hydrogen bond self-assembly and its sand grinding refinement in sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (Yili Technology), the hydrogen bond donor solvent is tetramethyl urea (99%, Acros), and this comparative example is different from Example 1 in that the hydrogen bond acceptor solvent is replaced by acetone (99%, Adamas) from acetonitrile (99%, Adamas). Other preparation method step parameters are the same as Example 1.

[0082] Comparative Example 7 This comparative example provides a composite solvent system based on hydrogen bond self-assembly and its sand grinding refinement in sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (Yili Technology), the hydrogen bond donor solvent is tetramethyl urea (99%, Acros), and this comparative example is different from Example 1 in that the hydrogen bond acceptor solvent is replaced by DMF (99%, Adamas) from acetonitrile (99%, Adamas). Other preparation method step parameters are the same as Example 1.

[0083] Comparative Example 8 This comparative example provides a composite solvent system based on hydrogen bond self-assembly and its sand grinding and refinement in a sulfide solid electrolyte and its preparation method. The sulfide electrolyte used in this comparative example is Li6PS5Cl (Yili Technology), the hydrogen bond donor solvent is tetramethyl urea (99%, Acros), and the hydrogen bond acceptor solvent is acetonitrile (99%, Adamas). This comparative example is different from Example 1 in that there is no S2 and no additives.

[0084] Other preparation method step parameters are the same as in Example 1.

[0085] 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 of electrolytes before and after refinement in Examples and Comparative Examples

[0086] According to the experimental data in Table 1, it can be clearly seen that relying solely on simple solvent mixing strategies, such as physical mixing of acetonitrile and hexane, although it can reduce the particle size of the sulfide electrolyte to a certain extent, its performance improvement effect is pale and powerless, the improvement of ionic conductivity is very limited, and the dispersion uniformity and long-term stability are still difficult to guarantee. The root cause is that these simple solvent mixing systems are essentially still stacked at the macroscopic level of solvent components, lacking effective design and fine regulation of the microstructure between solvent molecules, resulting in the optimization of solvent properties and performance improvement cannot go deep into the molecular level, and it is naturally difficult to fully tap the full potential of solvents in the dispersion and efficient refinement of sulfide electrolytes. More noteworthy is that when trying to use other types of hydrogen bond acceptor solvents (such as acetone or DMF with strong polarity) or hydrogen bond donor solvents (such as acetamide or pyrrole), and replacing acetonitrile or tetramethyl urea in the preferred composite solvent system of the present invention in equal amounts and containing additives, the experimental results show that the performance improvement effect of the sulfide electrolyte after refinement is far inferior to that of the system of the present invention, and the advantages are not outstanding. This phenomenon profoundly reveals a key issue: not all simple combinations of hydrogen bond donors and acceptor solvents can effectively improve the refinement effect of sulfide electrolytes. Simply relying on the hydrogen bond donor or acceptor ability of the solvent does not automatically achieve significant optimization of material performance. For example, highly polar hydrogen bond acceptor solvents such as acetone or DMF, although they have certain hydrogen bond acceptor capabilities, may produce unfavorable or even destructive interactions with sulfide electrolytes due to their own high polarity, ultimately offsetting the potential advantages of the hydrogen bond self-assembly strategy and limiting performance improvement. Similar problems may also occur in highly polar hydrogen bond donor solvents such as acetamide and pyrrole. Excessive polarity or mismatched solvation ability may hinder the effective improvement of performance.

[0087] However, in sharp contrast to the above-mentioned technical status, the acetonitrile + tetramethylurea hydrogen bond self-assembly composite solvent system proposed in the present invention, especially after the innovative introduction of cyclic boroxine additives, has shown remarkable technical breakthroughs and performance leaps. Thanks to the introduction of cyclic boroxine additives, the hydrogen bond synergy between acetonitrile and tetramethylurea is further strengthened and optimized, which not only induces the tetramethylurea carbonyl group to achieve directional arrangement, effectively improves the density of the hydrogen bond network, and constructs a unique and sophisticated hydrogen bond self-assembly structure, but also cleverly uses the host-guest effect of the additive to enable it to be efficiently adsorbed on the surface of sulfide particles, and creatively uses the hydrophobic group of the additive to reduce the interaction between particles. At the same time, the polar BO group is used to cleverly guide the orderly arrangement of solvent molecules, achieving effective stabilization of the interface. It is this multiple synergistic innovative mechanism that enables the composite solvent system of the present invention to more significantly and efficiently improve the dispersion state of the sulfide electrolyte, greatly improve the sand grinding efficiency, and under the premise of ensuring the chemical stability of the material to the greatest extent, ultimately achieve a comprehensive and leapfrog improvement in various key performance indicators of the sulfide solid electrolyte, including ionic conductivity and electrochemical properties.

[0088] 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 hydrogen bond self-assembly composite aprotic solvent, characterized in that: The steps include: S1, mixing tetramethyl urea and acetonitrile according to a molar ratio to obtain a composite aprotic solvent; S2, adding 2,4,6-tris(3,4,5-trifluorophenyl)boroxine and dispersing by ultrasonic to obtain a composite refinement solvent; S3, adding the sulfide solid electrolyte into the composite refining solvent, performing sand milling, and drying 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 tetramethylurea to acetonitrile is 75-85:15-25.

3. The solid electrolyte refinement method according to claim 1, characterized in that: In step S2, the amount of 2,4,6-tris(3,4,5-trifluorophenyl)boroxine added is 0.1-1.0 wt % of the composite aprotic solvent.

4. The solid electrolyte refinement method according to claim 1, characterized in that: In step S3, the temperature of the sanding treatment is 8-12°C.

5. The solid electrolyte refinement method according to claim 1, characterized in that: In step S3, 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 S3, the solid-liquid ratio of the sand milling process is 1:8-12.

7. The solid electrolyte refinement method according to claim 1, characterized in that: In step S3, 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 S3, the drying temperature is 50-70°C and the drying time is 10-14 hours.

9. The solid electrolyte refinement method according to claim 1, characterized in that: In step S3, the D50 particle size of the refined sulfide solid electrolyte powder is 400-600 nm.

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

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