An organic small molecule-sulfide composite electrolyte, a preparation method and application thereof

Abstract

The application discloses an organic small-molecule-sulfide composite electrolyte and a preparation method and application thereof, and belongs to the technical field of batteries; the method induces nano-structural transformation of sulfide electrolyte particles through self-limiting redox reactions between small-molecule solid organic additives and sulfide electrolytes, and generates an amorphous lithium-repellent protective layer on the surface of the particles in situ; the application can regulate the reactivity of small-molecule solid organic additives to sulfide electrolytes by introducing functional inorganic reactants, and the electrolyte particles after nano-structural modification can increase the contact area between particles and effectively fill pores in the cold pressing process, thereby significantly improving the cold pressing density of sulfide solid electrolytes; the amorphous lithium-repellent protective layer formed on the surface not only enhances the plastic deformation capacity of the electrolyte, but also improves the interface stability of the electrolyte to metal lithium, and finally realizes the significant improvement of the comprehensive performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte materials technology for all-solid-state batteries, specifically relating to an organic small molecule-sulfide composite electrolyte and its preparation method and application. Background Technology

[0002] All-solid-state lithium metal batteries are considered one of the ultimate solutions for next-generation energy storage technology due to their high theoretical energy density and good safety. Among them, sulfide solid electrolytes are one of the most promising electrolyte systems due to their good flexibility and ultra-high ionic conductivity comparable to liquid electrolytes.

[0003] However, when sulfide solid electrolytes are actually applied to lithium metal batteries, they face two fundamental challenges that severely restrict their commercialization: (1) the thermodynamically unstable lithium / electrolyte interface and the resulting continuous failure. Sulfide electrolytes and lithium metal are thermodynamically unstable, and a spontaneous reduction reaction occurs when they come into contact, generating initial decomposition products such as Li2S and Li3P. However, these in-situ generated interface phases have inherent defects in structure and function: their electronic insulation is insufficient, and they cannot effectively block the continuous tunneling of electrons from lithium metal to the electrolyte body, causing the reduction reaction to extend to the electrolyte continuously, continuously consuming active lithium and electrolyte; at the same time, they lack the physicochemical guidance ability for lithium deposition behavior, and cannot inhibit lithium invasion, resulting in extremely low critical current density of the battery, usually <1.0 mA cm⁻¹. -2 (2) Limited solid-solid interface contact and its resulting mechanical failure. To achieve excellent electrochemical performance, all-solid-state batteries require close contact between the electrodes and the electrolyte, as well as between the electrolyte particles themselves, to ensure unobstructed lithium-ion pathways. Cold-pressed sulfide electrolyte sheets still have high porosity, which can easily introduce microcracks or internal stresses into the brittle sulfide electrolyte. These mechanical defects are prone to expand into channels for preferential penetration of lithium dendrites during battery cycling, especially under the local stress caused by uneven lithium metal deposition. This creates a vicious cycle with the interfacial electrochemical instability problem, which together exacerbates battery failure.

[0004] To address these challenges, there is an urgent need to propose an innovative material design and preparation method that can reconstruct the structure of sulfide electrolyte particles and regulate the interface composition to construct a sulfide electrolyte layer with high density and high lithium stability while maintaining high ionic conductivity. This would improve the interfacial instability and mechanical failure issues, thereby promoting the practical application of high-performance, low-cost all-solid-state lithium metal batteries. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical defects of existing sulfide solid electrolytes in lithium metal battery applications, such as thermodynamic instability of the lithium / electrolyte interface and limited solid-solid interface contact. This invention provides an organic small molecule-sulfide composite electrolyte, its preparation method and application. This composite electrolyte can achieve particle nanostructuring and generate a lithium-repellent protective layer in situ, while improving cold pressing density and interface stability, thereby significantly improving the electrochemical performance and cycle stability of all-solid-state lithium metal batteries.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows: An organic small molecule-sulfide composite electrolyte, comprising organic additives and sulfide solid electrolyte.

[0007] Preferably, the molar ratio of organic additives to sulfide solid electrolyte is 1:30~50.

[0008] Preferably, the organic additives include solid small organic molecules or pretreated solid small organic molecules.

[0009] Preferably, the pretreated solid organic small molecules are obtained by pretreating solid organic small molecules with functional inorganic reactants.

[0010] Preferably, the molecular structure of the solid organic small molecule includes a conjugated backbone consisting of at least one aromatic ring, which may include a benzene ring or a naphthalene ring.

[0011] Preferably, at least one carbonyl group and at least one electron-withdrawing group are directly bonded to the conjugated skeleton. The electron-withdrawing group includes one or more of the following: fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, trifluoromethyl group, trichloromethyl group, carboxyl group, ester group, amide group, and sulfonyl group. Preferably, the sulfide electrolyte includes Li₂S-P₂S₅ and its doped system, Li₂S-P₂S₅-LiI and its doped system, and Li 6-x PS 5-x X 1+x and its doped systems, Li 6-x-y PS 5-x-y Cl 1+y Br x , where 0≤x≤0.7, 0.3≤y<0.6, and X includes one of Cl, Br and I.

[0012] Preferably, the solid organic small molecule includes one or more of tetrafluoro-1,4-benzoquinone, tetrachloro-1,4-benzoquinone, tetracyano-1,4-benzoquinone, 2,3,4,5-tetrafluorobenzoic acid, 2-trifluoromethylbenzoic acid, tetrafluoroterephthalic acid, 1,4-naphthoquinone, 5-fluoro-1,4-naphthoquinone, and 2-chloro-1,4-naphthoquinone.

[0013] Preferably, the functional inorganic reactants include inorganic compounds that have reducing or Lewis acidity.

[0014] Preferably, the functional inorganic reactants include one or more of lithium sulfide, lithium iodide, lithium selenide, lithium phosphide, aluminum iodide, gallium iodide, and aluminum chloride.

[0015] The small-molecule solid organic additive used in this invention undergoes a self-limited redox reaction with the sulfide electrolyte. The reactivity and chemical composition of this organic additive can be precisely controlled by introducing functional inorganic reactants. This maintains the high ionic conductivity of the sulfide electrolyte while ensuring its limited reactivity, and allows for the in-situ formation of a chemically tunable amorphous lithium-repellent protective layer on the surface of the composite electrolyte through reactant composition control, achieving controllable design and performance optimization of the interface layer. Simultaneously, after the redox reaction, the surface of the sulfide electrolyte particles undergoes a controllable nanostructural transformation, forming a uniformly sized secondary nanoparticle layer on the originally smooth particle surface. These surface nanoparticles can play a role in tableting. It has multiple advantages. First, it generates a mechanical interlocking effect, with particles interlocking with each other, changing the contact form from traditional surface contact to volume contact, greatly increasing the contact area and friction between particles. Second, it effectively reduces yield stress. The nano-sized secondary particles have both higher surface energy and better plastic deformation ability. Combined with the amorphous organic layer on the surface, the electrolyte can achieve flow and rearrangement under lower pressure. Third, it fully fills the pores. The nanoparticles generated in situ can effectively fill the original gaps between large particles, improving the cold pressing density of the electrolyte. The amorphous lithium-repellent protective layer formed in situ on the surface of the composite electrolyte can also give the lithium metal / electrolyte interface excellent mechanical toughness, which can well adapt to the volume changes during the lithium deposition / stripping process.

[0016] A method for preparing an organic small molecule-sulfide composite electrolyte includes the following steps: Under an inert atmosphere protected by argon, organic additives and sulfide solid electrolytes were mechanically ball-milled using zirconia ball milling beads at a speed of 80-150 rpm for 20-40 min and a ball-to-material mass ratio of 30-50:1 to obtain composite electrolyte powder.

[0017] Application of an organic small molecule-sulfide composite electrolyte in all-solid-state lithium metal batteries, wherein the negative electrode of the all-solid-state lithium metal battery is metallic lithium or a lithium alloy.

[0018] Preferably, the all-solid-state lithium metal battery includes a composite cathode, wherein the active material of the composite cathode includes one or more of NCM ternary materials, lithium cobalt oxide, and sulfur.

[0019] Preferably, the electrolyte of the all-solid-state lithium metal battery is an organic small molecule-sulfide composite electrolyte.

[0020] Preferably, the composite positive electrode sheet includes a binder and a binding aid.

[0021] Preferably, the binder comprises polyvinylidene fluoride-hexafluoropropylene copolymer, and the bonding aid comprises 1,4,5,8-naphthalenetetracarboxylic anhydride.

[0022] 1,4,5,8-Naphthalenetetracarboxylic anhydride, as a binder for composite cathode sheets, can effectively optimize the bonding performance between the components of the cathode sheet, reduce the interfacial contact resistance between the electrode and the electrolyte, and lower the initial interfacial impedance of the all-solid-state lithium metal battery. At the same time, this binder can improve the compatibility of the cathode interface, reduce the problem of interface detachment and cracking during battery charging, discharging and rate changes, improve the stability of the electrode structure, and thus enhance the cycle stability and rate adaptability of the battery.

[0023] Preferably, the mass ratio of the adhesive additive to the adhesive is 0.5~2.5:19.

[0024] Preferably, the composite positive electrode sheet includes a conductive agent and a conductive additive.

[0025] Preferably, the conductive agent includes Ketjen black, and the conductive additive includes 3,4,9,10-pyrene tetracarboxydiimide.

[0026] 3,4,9,10-Pyrenetetracarboxydiimide, as a conductive additive for composite cathode sheets, can significantly improve the electronic conductivity of the cathode sheet, accelerate the electrochemical reaction rate, and meet the rapid charge and discharge requirements of batteries at high rates. At the same time, this conductive additive can synergistically work with binders to further optimize the solid-solid interface contact of the electrode / electrolyte, significantly reduce the initial interface impedance of the battery, improve the dual transport efficiency of ions and electrons, effectively improve the performance stability of the battery at different rates, and improve the capacity recovery rate.

[0027] Preferably, the mass ratio of conductive additive to conductive agent is 1:10~20.

[0028] Preferably, the composite positive electrode dry film thickness is 5~25μm, and the active material areal density is 1.5~2.5mg / cm³. 2 .

[0029] More preferably, the composite positive electrode sheet includes an interface stabilizing additive, which includes oxazolo[5,4-d]pyrimidine-2-ylmethylamine, and the mass ratio of the interface stabilizing additive to the positive electrode active material is 0.5~3:200.

[0030] Oxazolo[5,4-d]pyrimidine-2-ylmethylamine, as an interface stabilizing additive for composite cathode sheets in all-solid-state lithium metal batteries, can effectively suppress electrochemical side reactions on the cathode side, stabilize the interface structure between the electrode and electrolyte, and form a synergistic effect with the binder 1,4,5,8-naphthalenetetracarboxylic anhydride and the conductive additive 3,4,9,10-pyrenetetracarboxydiimide, significantly reducing the initial interface impedance of the battery. At the same time, it can stabilize the electrode / electrolyte interface during high-rate charge and discharge of the battery, suppress the rapid increase of interface polarization, effectively improve the performance stability of the battery during high- and low-rate switching, and make the battery capacity recovery rate reach the optimal level. It has better compatibility with the cathode system of all-solid-state lithium metal batteries.

[0031] This invention also provides a method for preparing an all-solid-state lithium metal battery, including steps for preparing composite electrolyte powder, composite cathode sheet, composite electrolyte sheet, and the all-solid-state lithium metal battery, as detailed below: Step 1, the preparation steps of the composite electrolyte powder, include: Organic additives were mixed with sulfide solid electrolytes and mechanically ball-milled using zirconia ball milling beads. After the mixture was homogeneous, a composite electrolyte powder was obtained.

[0032] Preferably, the organic additives include solid organic small molecules.

[0033] Preferably, the molecular structure of the solid organic small molecule includes a conjugated skeleton composed of at least one aromatic ring, the aromatic ring including a benzene ring or a naphthalene ring; at least one carbonyl group and at least one electron-withdrawing group are directly bonded to the conjugated skeleton, the electron-withdrawing group including one or more of fluorine atom, chlorine atom, bromine atom, iodine atom, cyano, nitro, trifluoromethyl, trichloromethyl, carboxyl, ester group, amide group and sulfonyl group.

[0034] Preferably, the solid organic small molecule includes one or more of tetrafluoro-1,4-benzoquinone, tetrachloro-1,4-benzoquinone, tetracyano-1,4-benzoquinone, 2,3,4,5-tetrafluorobenzoic acid, 2-trifluoromethylbenzoic acid, tetrafluoroterephthalic acid, 1,4-naphthoquinone, 5-fluoro-1,4-naphthoquinone, and 2-chloro-1,4-naphthoquinone.

[0035] Preferably, the sulfide electrolyte includes Li₂S-P₂S₅ and its doped system, Li₂S-P₂S₅-LiI and its doped system, and Li 6-x PS 5-x X 1+x and its doped systems, Li 6-x-y PS 5-x-y Cl 1+y Br x, where 0≤x≤0.7, 0.3≤y<0.6, and X includes one of Cl, Br and I.

[0036] Preferably, the molar ratio of organic additives to sulfide solid electrolyte is 1:30~50.

[0037] Preferably, the ball milling speed is 80~150 rpm, the ball milling time is 20~40 min, and the ball-to-material mass ratio is 30~50:1.

[0038] More preferably, the organic additive includes pretreated solid organic small molecules, which are obtained by pretreating solid organic small molecules with functional inorganic reactants. The pretreatment includes mixing the solid organic small molecules with functional inorganic reactants and mechanically ball-milling them with zirconia ball milling beads. After the mixture is uniformly mixed by ball milling, the pretreated solid organic small molecules are obtained.

[0039] More preferably, the functional inorganic reactants include one or more of lithium sulfide, lithium iodide, lithium selenide, lithium phosphide, aluminum iodide, gallium iodide, and aluminum chloride.

[0040] More preferably, the molar ratio of solid organic small molecules to functional inorganic reactants is 1:1 to 4.

[0041] More preferably, the ball milling speed is 80~150 rpm, the ball milling time is 20~40 min, and the ball-to-material mass ratio is 30~50:1.

[0042] Step 2, the preparation steps of the composite positive electrode sheet include, Under an inert atmosphere protected by argon, the binder is mixed with anhydrous N-methylpyrrolidone and stirred for 4-8 hours to obtain a homogeneous binder solution. The positive electrode active material, conductive agent and composite electrolyte powder are ground for 5-15 minutes until they are mixed evenly, transferred to a stirring container, the binder solution is added, and stirred for 2-6 hours to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of an aluminum foil current collector, allowed to stand for 20-40 minutes, and then vacuum dried at 70-90℃ for 10-14 hours. The composite positive electrode sheet is then cut to obtain the composite positive electrode sheet.

[0043] Preferably, the binder comprises polyvinylidene fluoride-hexafluoropropylene copolymer.

[0044] Preferably, in the adhesive solution, the mass ratio of the adhesive to anhydrous N-methylpyrrolidone is 1:5~15.

[0045] Preferably, the positive electrode active material is one or more of the following: NCM ternary material, lithium cobalt oxide, and sulfur.

[0046] Preferably, the conductive agent includes Ketjen black.

[0047] Preferably, the mass ratio of the conductive agent to the positive electrode active material is 1:10~15.

[0048] Preferably, the mass ratio of the composite electrolyte powder to the positive electrode active material is 1:4 to 2:7.

[0049] Preferably, the mass ratio of binder to positive electrode active material is 1:10~15.

[0050] Preferably, the adhesive solution includes an adhesive aid, which includes 1,4,5,8-naphthalenetetracarboxylic anhydride.

[0051] Preferably, the mass ratio of the adhesive additive to the adhesive is 0.5~2.5:19.

[0052] Preferably, the viscosity of the positive electrode slurry is 5000~7000 mPa·s.

[0053] Preferably, the dry film thickness of the composite positive electrode is 5~25μm, and the surface density of the active material is 1.5~2.5mg / cm².

[0054] More preferably, the positive electrode slurry includes a conductive additive, which includes 3,4,9,10-pyrene tetracarboxydiimide.

[0055] More preferably, the mass ratio of the conductive additive to the conductive agent is 1:10~20.

[0056] More preferably, the positive electrode slurry includes an interface stabilizing additive, which includes oxazolo[5,4-d]pyrimidine-2-methylamine.

[0057] More preferably, the mass ratio of the interface stabilizing additive to the positive electrode active material is 0.5~3:200.

[0058] Step 3, the preparation steps of the composite electrolyte sheet include, Under an inert atmosphere protected by argon, the composite electrolyte powder prepared above is passed through a 180-220 mesh sieve, transferred to a circular mold adapted for button batteries and spread evenly. It is then cold-pressed under a pressure of 300-400 MPa for 3-7 minutes, and subsequently vacuum-dried at 50-70°C for 1-3 hours to obtain a composite electrolyte sheet.

[0059] Preferably, the composite electrolyte sheet has a diameter of 15-17 mm and a thickness of 0.8-1.0 mm.

[0060] Step four, the fabrication steps of the all-solid-state lithium metal battery include, Under an inert atmosphere protected by argon, take the negative electrode shell of the button cell and place a stainless steel gasket and a spring in the center of the bottom of the shell. Place a lithium metal or lithium alloy sheet in the center of the spring, coaxial with the spring and gasket. Cover the center of the lithium metal or lithium alloy sheet with a composite electrolyte sheet, and then place the composite positive electrode sheet in the center of the other side of the composite electrolyte sheet, coaxial with the lithium metal or lithium alloy sheet below. Place a glass fiber separator on the outside of the composite positive electrode sheet. Cover the positive electrode shell of the button cell and transfer it to a button cell sealing machine under an inert atmosphere. Seal it for 3-5 seconds under a sealing pressure of 400-600 Pa to obtain an all-solid-state lithium metal battery.

[0061] Preferably, the stainless steel gasket has a thickness of 0.4~0.6mm and a diameter of 14~16mm.

[0062] Preferably, the thickness of the spring sheet is 0.2~0.4mm and the diameter is 14~16mm.

[0063] Preferably, the thickness of the lithium metal or lithium alloy sheet is 0.08~0.12mm.

[0064] Preferably, the diameter of the glass fiber diaphragm is 15~17mm.

[0065] This invention utilizes a self-limited redox reaction between a specific structured solid organic small molecule and a sulfide solid electrolyte, and introduces functional inorganic reactants to regulate reaction activity. Simultaneously, it employs synergistic optimization design of binders, conductive agents, and interface stabilizing additives in the composite cathode sheet, thus completing the preparation of a composite electrolyte and an all-solid-state lithium metal battery. Therefore, it has the following beneficial effects: it achieves the nanostructural transformation of sulfide electrolyte particles, generating an amorphous lithium-repellent protective layer in situ, significantly improving the electrolyte's cold-pressing density and lithium interface stability, and effectively suppressing lithium dendrite growth and interface side reactions; it optimizes the solid-solid interface contact of the electrode / electrolyte, significantly reducing the initial interface impedance of the battery, and improving electrode structural stability, electronic conductivity, and ion transport efficiency; at the same time, the preparation process is characterized by mild conditions, controllable parameters, and simple operation, requiring no harsh high-temperature and high-pressure conditions, and having low equipment requirements, making it suitable for large-scale industrial production. Ultimately, the resulting all-solid-state lithium metal battery exhibits high critical current density, high first-cycle coulombic efficiency, long cycle life, and excellent rate performance, resulting in a qualitative improvement in overall electrochemical performance. Therefore, this invention is an organic small molecule-sulfide composite electrolyte with a scientifically sound design, significant performance advantages, simple preparation process, and suitability for industrial production needs. It can effectively solve the technical bottlenecks of traditional sulfide solid electrolytes, such as unstable interface and limited solid-solid contact, and promote the practical application of all-solid-state lithium metal batteries. Attached Figure Description

[0066] Figure 1 Li, for Comparative Example 1 5.5 PS4.5 Cl 1.5 Field emission scanning electron microscope image of electrolyte powder.

[0067] Figure 2 Li, for Comparative Example 1 5.5 PS 4.5 Cl 1.5 Field emission scanning electron microscope image of the electrolyte sheet.

[0068] Figure 3 The image shows a field emission scanning electron microscope image of the composite electrolyte powder prepared in Example 2.

[0069] Figure 4 The image shows a field emission scanning electron microscope image of the composite electrolyte sheet prepared in Example 2.

[0070] Figure 5 The image shows a cryo-transmission electron microscope image of the composite electrolyte powder prepared in Example 2.

[0071] Figure 6 The constant current charge-discharge voltage-time curves of the lithium symmetric battery assembled with the composite electrolyte sheet of Example 2 are shown.

[0072] Figure 7 Li, for Comparative Example 1 5.5 PS 4.5 Cl 1.5 Constant current charge-discharge voltage-time curves of lithium symmetric batteries assembled with electrolyte sheets. Detailed Implementation

[0073] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0075] Example 1: This embodiment provides an all-solid-state lithium metal battery. The preparation steps mainly include the preparation steps of composite electrolyte powder, composite cathode sheet, composite electrolyte sheet and all-solid-state lithium metal battery, as detailed below.

[0076] Step 1: Preparation of composite electrolyte powder: In an argon-protected glove box, the organic additive and the sulfide solid electrolyte were mechanically ball-milled for 30 minutes at 110 rpm to obtain the composite electrolyte powder. The sulfide solid electrolyte was Li. 5.5 PS 4.5 Cl 1.5 The organic additive is a solid small organic molecule, specifically p-tetrafluorobenzoquinone, which reacts with Li... 5.5 PS 4.5 Cl 1.5 The molar ratio is 1:40; the grinding balls are zirconia grinding balls with a ball-to-material mass ratio of 40:1.

[0077] Step 2: Preparation of composite positive electrode sheet: In an argon-protected glove box, the binder and anhydrous N-methylpyrrolidone are mixed evenly and stirred for 6 hours to obtain a binder solution; the positive electrode active material, conductive agent and composite electrolyte powder are added to an agate mortar and manually ground for 10 minutes until uniformly mixed, then transferred to a polytetrafluoroethylene beaker, the binder solution is added, and stirred for 4 hours to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the surface of an aluminum foil current collector, allowed to stand for 30 minutes, and then vacuum dried at 80℃ for 12 hours, and cut into round pieces with a diameter of 14 mm to obtain a composite positive electrode sheet. In the binder solution, the binder is polyvinylidene fluoride-hexafluoropropylene copolymer, and the mass ratio of binder to anhydrous N-methylpyrrolidone is 1:9; the positive electrode active material is NCM83125 ternary positive electrode, the conductive agent is Ketjen Black, and the mass ratio of conductive agent to positive electrode active material is 1:14; the mass ratio of composite electrolyte powder to positive electrode active material is 2:7; the mass of the binder solution is measured by the mass of the binder, and the mass ratio of binder to positive electrode active material is 1:14; the viscosity of the positive electrode slurry is 6000 mPa·s, the dry film thickness of the composite positive electrode sheet is 20 μm, and the areal density of the active material is 2.0 mg / cm³. 2 .

[0078] Step 3: Preparation of the composite electrolyte sheet: In an argon-protected glove box, the composite electrolyte powder was passed through a 200-mesh sieve and transferred to a circular mold adapted for the CR2025 button battery. The powder was evenly spread and cold-pressed at 360 MPa for 5 minutes, then vacuum-dried at 60°C for 2 hours to obtain the composite electrolyte sheet. The composite electrolyte sheet has a diameter of 16 mm and a thickness of 0.9 mm.

[0079] Step 4: Preparation of the all-solid-state lithium metal battery: In an argon-protected glove box, take a CR2025 type negative electrode shell, place a stainless steel gasket at the center of the bottom of the shell, and place a spring sheet on the gasket; place the lithium metal sheet in the center of the spring sheet, coaxial with the spring sheet and gasket; cover the center of the lithium metal sheet with a composite electrolyte sheet, and place the composite positive electrode sheet in the center of the other side of the electrolyte sheet, coaxial with the lithium sheet below; place a glass fiber separator on the outside of the composite positive electrode sheet; cover with the CR2025 type positive electrode shell, transfer to a button battery sealing machine in the glove box, set the sealing pressure to 500Pa, and seal for 4s to obtain the all-solid-state lithium metal battery. The stainless steel gasket is 0.5mm thick and 15mm in diameter; the spring sheet is 0.3mm thick and 15mm in diameter; the lithium metal sheet is 0.1mm thick; and the glass fiber separator is 16mm in diameter.

[0080] Example 2: This embodiment provides an all-solid-state lithium metal battery, which differs from Embodiment 1 only in the preparation steps of the composite electrolyte powder.

[0081] Step 1: Preparation of composite electrolyte powder: In an argon-protected glove box, the solid organic small molecule and the functional inorganic reactant were mechanically ball-milled for 10 min at 110 rpm to obtain an organic additive; the organic additive and the sulfide solid electrolyte were then mechanically ball-milled for 30 min at 110 rpm to obtain the composite electrolyte powder. The solid organic small molecule was p-tetrafluorobenzoquinone, the functional inorganic reactant was lithium sulfide, and the molar ratio of p-tetrafluorobenzoquinone to lithium sulfide was 1:2; the sulfide solid electrolyte was Li... 5.5 PS 4.5 Cl 1.5 p-Tetrafluorobenzoquinone and Li 5.5 PS 4.5 Cl 1.5 The molar ratio is 1:40; the grinding balls are zirconia grinding balls with a ball-to-material mass ratio of 40:1.

[0082] Example 3: This embodiment provides an all-solid-state lithium metal battery, which differs from Embodiment 1 only in the preparation steps of the composite electrolyte powder.

[0083] Step 1: Preparation of composite electrolyte powder: In an argon-protected glove box, the solid organic small molecule and the functional inorganic reactant were mechanically ball-milled for 10 min at 110 rpm to obtain an organic additive; the organic additive and the sulfide solid electrolyte were then mechanically ball-milled for 30 min at 110 rpm to obtain the composite electrolyte powder. The solid organic small molecule was p-tetrafluorobenzoquinone, the functional inorganic reactant was aluminum iodide, and the molar ratio of p-tetrafluorobenzoquinone to aluminum iodide was 1:0.5; the sulfide solid electrolyte was Li... 5.5 PS4.5 Cl 1.5 p-Tetrafluorobenzoquinone and Li 5.5 PS 4.5 Cl 1.5 The molar ratio is 1:40; the grinding balls are zirconia grinding balls with a ball-to-material mass ratio of 40:1.

[0084] Example 4: This embodiment provides an all-solid-state lithium metal battery, which differs from Embodiment 1 only in the preparation steps of the composite electrolyte powder.

[0085] Step 1: Preparation of composite electrolyte powder: In an argon-protected glove box, the organic additive and the sulfide solid electrolyte were mechanically ball-milled for 30 minutes at 110 rpm to obtain the composite electrolyte powder. The sulfide solid electrolyte was Li. 5.5 PS 4.5 Cl 1.5 The organic additive is a solid small organic molecule, specifically 2,3,5,6-tetracyano-1,4-benzoquinone. 2,3,5,6-tetracyano-1,4-benzoquinone reacts with Li... 5.5 PS 4.5 Cl 1.5 The molar ratio is 1:40; the grinding balls are zirconia grinding balls with a ball-to-material mass ratio of 40:1.

[0086] Example 5: This embodiment provides an all-solid-state lithium metal battery. The only difference from Embodiment 1 is the preparation steps of the composite cathode.

[0087] Step 2: Preparation of composite positive electrode sheet: In an argon-protected glove box, binder, binding aid and anhydrous N-methylpyrrolidone are mixed evenly and stirred for 6 hours to obtain binder solution; positive electrode active material, conductive agent and composite electrolyte powder are added to an agate mortar and manually ground for 10 minutes until uniformly mixed, transferred to a polytetrafluoroethylene beaker, binder solution is added, and stirred for 4 hours to obtain positive electrode slurry; positive electrode slurry is evenly coated on the surface of aluminum foil current collector, allowed to stand for 30 minutes, vacuum dried at 80℃ for 12 hours, and cut into round pieces with a diameter of 14 mm to obtain composite positive electrode sheet. In the binder solution, the binder is polyvinylidene fluoride-hexafluoropropylene copolymer, with a mass ratio of binder to anhydrous N-methylpyrrolidone of 1:9; the binder aid is 1,4,5,8-naphthalenetetracarboxylic anhydride, with a mass ratio of binder aid to binder of 1:19; the positive electrode active material is NCM83125 ternary positive electrode, the conductive agent is Ketjen Black, with a mass ratio of conductive agent to positive electrode active material of 1:14, and the mass ratio of composite electrolyte powder to positive electrode active material of 2:7; the mass of the binder solution is measured by the mass of the binder therein, with a mass ratio of binder to positive electrode active material of 1:14; the viscosity of the positive electrode slurry is 6000 mPa·s, the dry film thickness of the composite positive electrode sheet is 20 μm, and the areal density of the active material is 2.0 mg / cm³. 2 .

[0088] Example 6: This embodiment provides an all-solid-state lithium metal battery. The only difference from embodiment 5 is that the mass ratio of the binder to the binder is adjusted from 1:19 in embodiment 5 to 2:19 in embodiment 6.

[0089] Example 7: This embodiment provides an all-solid-state lithium metal battery, which differs from Embodiment 6 only in the preparation steps of the composite cathode.

[0090] Step 2: Preparation of composite positive electrode sheet: In an argon-protected glove box, the binder, binding aid, and anhydrous N-methylpyrrolidone are uniformly mixed and stirred for 6 hours to obtain a binder solution; the positive electrode active material, conductive agent, conductive aid, and composite electrolyte powder are added to an agate mortar and manually ground for 10 minutes until uniformly mixed, then transferred to a polytetrafluoroethylene beaker, the binder solution is added, and stirred for 4 hours to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on the surface of an aluminum foil current collector, allowed to stand for 30 minutes, and then vacuum dried at 80℃ for 12 hours, and cut into round sheets with a diameter of 14 mm to obtain the composite positive electrode sheet. In the binder solution, the binder is polyvinylidene fluoride-hexafluoropropylene copolymer, with a mass ratio of binder to anhydrous N-methylpyrrolidone of 1:9; the binder aid is 1,4,5,8-naphthalenetetracarboxylic anhydride, with a mass ratio of binder aid to binder of 2:19; the positive electrode active material is NCM83125 ternary positive electrode; the conductive agent is Ketjen Black, with a mass ratio of conductive agent to positive electrode active material of 1:14; the conductive aid is 3,4,9,10-pyrenetetracarboxylic diimide, with a mass ratio of conductive aid to conductive agent of 1:15; and the mass ratio of composite electrolyte powder to positive electrode active material is 2:7. The mass of the binder solution is measured by the mass of the binder therein, with a mass ratio of binder to positive electrode active material of 1:14. The viscosity of the positive electrode slurry is 6000 mPa·s, the dry film thickness of the composite positive electrode sheet is 20 μm, and the areal density of the active material is 2.0 mg / cm³. 2 .

[0091] Example 8: This embodiment provides an all-solid-state lithium metal battery, which differs from Embodiment 7 only in the preparation steps of the composite cathode.

[0092] Step 2: Preparation of composite positive electrode sheet: In an argon-protected glove box, binder, binding aid and anhydrous N-methylpyrrolidone are mixed evenly and stirred for 6 hours to obtain binder solution; positive electrode active material, conductive agent, conductive aid, composite electrolyte powder and additives are added to an agate mortar and manually ground for 10 minutes until uniformly mixed, transferred to a polytetrafluoroethylene beaker, binder solution is added, and stirred for 4 hours to obtain positive electrode slurry; positive electrode slurry is evenly coated on the surface of aluminum foil current collector, allowed to stand for 30 minutes, vacuum dried at 80℃ for 12 hours, and cut into round pieces with a diameter of 14 mm to obtain composite positive electrode sheet. In the binder solution, the binder is polyvinylidene fluoride-hexafluoropropylene copolymer, with a mass ratio of binder to anhydrous N-methylpyrrolidone of 1:9; the binder aid is 1,4,5,8-naphthalenetetracarboxylic anhydride, with a mass ratio of binder aid to binder of 2:19; the positive electrode active material is NCM83125 ternary positive electrode; the conductive agent is Ketjen Black, with a mass ratio of conductive agent to positive electrode active material of 1:14; the conductive aid is 3,4,9,10-pyrenetetracarboxydiimide, with a mass ratio of conductive aid to conductive agent of 1:14. The mass ratio of the composite electrolyte powder to the positive electrode active material is 1:15, and the mass ratio of the composite electrolyte powder to the positive electrode active material is 2:7; the additive is oxazolo[5,4-d]pyrimidine-2-ylmethylamine, and the mass ratio of the additive to the positive electrode active material is 1:200; the mass of the binder solution is measured by the mass of the binder therein, and the mass ratio of the binder to the positive electrode active material is 1:14; the viscosity of the positive electrode slurry is 6000 mPa·s, the dry film thickness of the composite positive electrode sheet is 20 μm, and the areal density of the active material is 2.0 mg / cm³. 2 .

[0093] Comparative Example 1: This comparative example provides an all-solid-state lithium metal battery. The only difference from Example 1 is that Comparative Example 1 uses a pure sulfide electrolyte without added organic additives, with Li... 5.5 PS 4.5 Cl 1.5 The electrolyte powder was used to prepare composite positive electrode sheets, electrolyte sheets, and all-solid-state lithium metal batteries.

[0094] Comparative Example 2: This comparative example provides an all-solid-state lithium metal battery. The only difference between this example and Example 5 is that the mass ratio of the binder to the binder in Comparative Example 2 is adjusted from 1:19 in Example 5 to 3:19.

[0095] Comparative Example 3: This comparative example provides an all-solid-state lithium metal battery. The only difference from Example 7 is that the conductive additive in the composite cathode of Comparative Example 3 is changed from 3,4,9,10-pyrene tetracarboxylic diimide in Example 7 to pyromellitic diimide.

[0096] Comparative Example 4: This comparative example provides an all-solid-state lithium metal battery. The only difference from Example 8 is that the additive in the composite cathode of Comparative Example 4 is changed from oxazolo[5,4-d]pyrimidine-2-ylmethylamine in Example 8 to 2-methylaminopyrimidine.

[0097] Experimental Example 1: Microscopic morphology characterization of electrolytes.

[0098] Test samples: Composite electrolyte powder and composite electrolyte sheet prepared in Example 2, and Li from Comparative Example 1. 5.5 PS 4.5 Cl 1.5 Electrolyte powder, electrolyte tablets.

[0099] Test method: Field emission scanning electron microscope (SEM) was used with an accelerating voltage of 15kV and a working distance of 8mm. The particle morphology of electrolyte powder and the cross-sectional micromorphology of electrolyte sheet were observed, and SEM images were taken and the microscopic features of the samples were analyzed.

[0100] Li prepared in Comparative Example 1 5.5 PS 4.5 Cl 1.5 Field emission scanning electron microscope image of electrolyte powder as shown below Figure 1 As shown, the Li prepared in Comparative Example 1 exhibits a smooth particle surface and a large particle size; 5.5 PS 4.5 Cl 1.5 Field emission scanning electron microscope image of the electrolyte sheet as shown below Figure 2 As shown, the composite electrolyte powder exhibits discontinuous contact at the microscopic level and has high porosity; the field emission scanning electron microscope image of the composite electrolyte powder prepared in Example 2 is shown below. Figure 3 As shown, the field emission scanning electron microscope image of the composite electrolyte powder sheet prepared in Example 2 is as follows. Figure 4 As shown, the surface of the large particles is composed of nano-sized secondary particles. This special surface structure enables particle rearrangement and pore filling after cold pressing, resulting in higher density.

[0101] Experimental Example 2: Microstructure characterization of electrolytes.

[0102] Test sample: Composite electrolyte powder prepared in Example 2.

[0103] Test method: Cryo-TEM was used. The sample was dispersed in anhydrous n-hexane, dropped onto a copper grid and rapidly frozen before testing. The accelerating voltage was set to 200 kV. The microstructure of the electrolyte particles was observed, and the phase composition and interface characteristics were analyzed.

[0104] The cryo-transmission electron microscope image of the composite electrolyte powder prepared in Example 2 is shown below. Figure 5 As shown, the edge region of the electrolyte particles is an amorphous phase and contains unreacted Li. 5.5 PS 4.5 Cl 1.5 The lattice fringes indicate that the reaction between the small molecule solid organic additive and the sulfide electrolyte is self-limiting, forming an amorphous region that coats the sulfide electrolyte particles.

[0105] Experimental Example 3: Critical Current Density Test of Lithium Symmetric Cells.

[0106] Test samples: The composite electrolyte sheet prepared in Example 2 and the Li in Comparative Example 1 5.5 PS 4.5 Cl 1.5 Electrolyte tablets.

[0107] Test method: 150 mg of the composite electrolyte powder prepared in Example 2 was simultaneously mixed with Li from Comparative Example 1. 5.5 PS 4.5 Cl 1.5 Electrolyte powder was pressed into tablets at 360 MPa for 3 minutes to obtain electrolyte sheets. A CR2025 negative electrode shell was placed on the glove box operating table, with a stainless steel gasket placed at the center of the shell bottom and a spring sheet placed on the gasket. A lithium metal sheet was placed in the center of the spring sheet, coaxial with the spring sheet and gasket. The electrolyte sheet was placed over the center of the lithium metal sheet. The lithium metal sheet was placed on the other side of the electrolyte sheet, coaxial with the lithium sheet below. The CR2025 positive electrode shell was then covered and transferred to a button battery sealing machine in the glove box. The sealing pressure was set to 500 Pa and the sealing time was 4 seconds to obtain a lithium symmetric battery. A battery testing system was used to perform a constant current charge-discharge test on the lithium symmetric battery at room temperature, gradually increasing the current density by 0.2 mA cm⁻¹ each time. -2 Cycle for 10 hours at each current density level until the battery short-circuits. Record the current density at this point, which is the critical current density.

[0108] The constant current charge-discharge voltage-time curve of the lithium symmetric battery assembled from the composite electrolyte sheet prepared in Example 2 is shown below. Figure 6 As shown, Li in Comparative Example 1 5.5 PS 4.5 Cl 1.5 The constant current charge / discharge voltage-time curves of the lithium symmetric battery assembled with electrolyte sheets are shown below. Figure 7 As shown in Table 1, the test results of the critical current density of lithium symmetric batteries are as follows.

[0109] Table 1. Test results of critical current density of lithium symmetric batteries

[0110] Example 2 exhibits a higher critical current density and higher lithium stability compared to the comparative example.

[0111] Test Example 4: Constant Current Charge-Discharge Cycle Performance Test of All-Solid-State Lithium Metal Battery.

[0112] Test samples: All-solid-state lithium metal batteries prepared in Examples 1-4 and Comparative Example 1.

[0113] Test method: A battery test system was used to conduct constant current charge-discharge cycle tests at a rate of 0.5C within a voltage range of 2.8~4.3V at room temperature. The coulombic efficiency of the battery in the first cycle and the discharge specific capacity at different cycle numbers were recorded, and the capacity retention rate after cycling was calculated.

[0114] The test results of the constant current charge-discharge cycle performance of the all-solid-state lithium metal battery are shown in Table 2.

[0115] Table 2. Test results of constant current charge-discharge cycle performance of all-solid-state lithium metal batteries

[0116] The pure sulfide electrolyte battery in Comparative Example 1 had a coulombic efficiency of only 76.3% in the first cycle and a capacity retention of 73% after 100 cycles. In contrast, the composite electrolyte batteries in Examples 1-4 all achieved a coulombic efficiency of over 79.0% in the first cycle and a significant increase in the number of cycles. Among them, the battery in Example 2 had the best performance, with a coulombic efficiency of 82.6% in the first cycle and a capacity retention of 94.0% after 1500 cycles, demonstrating excellent cycle stability.

[0117] Experimental Example 5: Half-cell coulombic efficiency test.

[0118] Test samples: Composite electrolyte sheets prepared in Examples 1-4 and Comparative Example 1.

[0119] Test Method: Assemble a CR2025 lithium metal half-cell. The assembly structure consists of a battery casing, a silver-plated copper foil current collector, an electrolyte sheet, a lithium metal sheet, a spring, a gasket, and a battery cover. The lithium metal sheet serves as the counter electrode and reference electrode, and the silver-plated copper foil serves as the working electrode. A battery testing system is used at room temperature with a 0.1 mA cm⁻¹ temperature. -2 Current density, 1mAh cm -2 The battery was subjected to constant current charge-discharge cycle testing at its maximum capacity, and the first-cycle coulombic efficiency, number of cycles, and average coulombic efficiency were recorded.

[0120] The results of the half-cell coulombic efficiency test are shown in Table 3.

[0121] Table 3. Results of half-cell coulombic efficiency test

[0122] The half-cell of Comparative Example 1 had a first-cycle coulombic efficiency of 88.1%, could only cycle stably for 30 cycles, and had an average coulombic efficiency of 95.0%. The composite electrolyte half-cells of Examples 1-4 all had first-cycle coulombic efficiencies of over 90.5%, increased to 70 cycles or more, and had average coulombic efficiencies of over 98.9%. Among them, the half-cell of Example 2 had the best performance, with a first-cycle coulombic efficiency of 93.6% and an average coulombic efficiency of 99.4% after 100 cycles. This shows that the composite electrolyte of the present invention can effectively suppress interfacial side reactions and improve the reversibility of lithium metal deposition / stripping.

[0123] Experimental Example 6: Initial Interfacial Impedance Test of All-Solid-State Lithium Metal Batteries Test samples: All-solid-state lithium metal batteries prepared in Examples 1, 5-8 and Comparative Examples 2-4.

[0124] Test method: A battery test system was used to conduct constant current charge-discharge cycle tests at a rate of 0.5C within a voltage range of 2.8 to 4.3V at room temperature. An AC impedance spectrometer was used to test the interface impedance of the battery within a frequency range of 100kHz to 0.01Hz, and the initial interface impedance value was recorded.

[0125] The initial interface impedance test results of the all-solid-state lithium metal battery are shown in Table 4.

[0126] Table 4. Initial interfacial impedance test results of all-solid-state lithium metal batteries

[0127] Example 5, based on Example 1, added a binder 1,4,5,8-naphthalenetetracarboxylic anhydride, resulting in a decrease in initial interfacial impedance. The introduction of the binder optimized the bonding performance between the components of the positive electrode, reduced interfacial contact resistance, and improved battery cycle stability. Example 6 adjusted the mass ratio of binder to binder to 2:19. Compared to Example 5, the first-cycle coulombic efficiency and capacity retention were further improved, and the interfacial impedance continued to decrease, indicating that the binder was more effective at this ratio and could better improve the compatibility of the positive electrode interface. Example 7 added a conductive additive 3,4,9,10-pyrenetetracarboxylic diimide, resulting in a significant decrease in interfacial impedance. The addition of the conductive additive improved the electronic conductivity of the positive electrode and, synergistically with the binder, further optimized the electrode / electrolyte interface contact, significantly improving electrochemical performance. Example 8 introduced oxazolo[5,4-d]pyrimidin-2-ylmethylamine as an additive, resulting in the lowest initial interfacial impedance. This additive effectively suppressed side reactions on the positive electrode side, stabilized the electrode interface structure, and... The binder and conductive additive work together to significantly improve the overall electrochemical performance of the battery. In Comparative Example 2, the mass ratio of binder to binder was adjusted to 3:19. Compared to Example 5, the interfacial impedance increased significantly because excessive binder was added, which damaged the conductive network inside the positive electrode and reduced battery performance. In Comparative Example 3, the conductive additive was replaced with pyromellitic diimide. Compared to Example 7, the electrochemical performance decreased significantly, indicating that 3,4,9,10-pyrene tetracarboxylic diimide... The electrical properties and compatibility with the cathode system are superior, and the replaced conductive additive cannot achieve the same interface optimization and conductivity enhancement effect. In Comparative Example 4, the additive was replaced with 2-methylaminopyrimidine. Compared with Example 8, its first-cycle coulombic efficiency and capacity retention rate decreased slightly, and the interface impedance increased. This indicates that oxazolo[5,4-d]pyrimidine-2-ylmethylamine is better than 2-methylaminopyrimidine in suppressing cathode side reactions and stabilizing interface structure. The additive selected in this invention has better compatibility with the cathode system.

[0128] Test Example 7: Rate Performance Test of All-Solid-State Lithium Metal Batteries Test samples: All-solid-state lithium metal batteries prepared in Examples 1, 5-8 and Comparative Examples 2-4.

[0129] Test method: Using a battery testing system, constant current charge and discharge tests were performed sequentially at rates of 0.2C, 0.5C, 1C, 2C, and 5C within a voltage range of 2.8~4.3V at room temperature. Each rate was cycled 10 times, and the average discharge specific capacity of the battery at each rate was recorded. After the 5C rate test was completed, the test was resumed at the 0.2C rate for another 10 cycles, and the average discharge specific capacity after the recovery was recorded. The capacity recovery rate was calculated.

[0130] The rate performance test results of the all-solid-state lithium metal battery are shown in Table 5.

[0131] Table 5. Rate performance test results of all-solid-state lithium metal batteries

[0132] Compared to Example 1, Example 5 optimized the bonding structure of the positive electrode by introducing the binder 1,4,5,8-naphthalenetetracarboxylic anhydride, reducing interface detachment and cracking during rate changes and improving the battery's rate adaptability. In Example 6, after adjusting the binder ratio, the capacity recovery rate was slightly improved compared to Example 5, indicating that the optimal binder ratio can further reduce ion transport resistance and improve the battery's performance stability at different rates. In Example 7, the capacity recovery rate was further improved after adding the conductive additive 3,4,9,10-pyrenetetracarboxylic diimide, as 3,4,9,10-pyrenetetracarboxylic diimide effectively improved the electronic conductivity of the positive electrode, accelerated the electrochemical reaction rate, and met the rapid charge and discharge requirements at high rates. In Example 8, the capacity recovery rate reached its highest level after adding oxazolo[5,4-d]pyrimidin-2-ylmethylamine, as this additive can stabilize the electrode / electrolyte interface at high rates and inhibit interfacial polarity. The rapid increase in capacitance allows the battery to maintain excellent performance stability during high and low rate switching. In Comparative Example 2, due to excessive addition of binder, the internal conductive and ion transport networks of the positive electrode were damaged, resulting in a lower discharge specific capacity at all rates compared to Example 5. The performance degradation was more significant at high rates, and the capacity recovery rate was also lower, indicating that excessive binder can seriously affect the rate performance of the battery. In Comparative Example 3, after replacing the conductive additive with pyromellitic diimide, the discharge specific capacity at all rates decreased compared to Example 7, especially at high rates, and the capacity recovery rate also decreased. In Comparative Example 4, after replacing the additive with 2-methylaminopyrimidine, the discharge specific capacity and capacity recovery rate at high rates decreased slightly compared to Example 8, indicating that 2-methylaminopyrimidine is not as effective as oxazolo[5,4-d]pyrimidine-2-ylmethylamine in stabilizing the high-rate interface and suppressing polarization. The additive selected in this invention is more suitable for the high-rate operation requirements of all-solid-state lithium metal batteries.

[0133] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any way. Any person skilled in the art can make some modifications or alterations to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as the technology or embodiments that are substantially the same as the present invention.

[0134] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. An organic small molecule-sulfide composite electrolyte, characterized in that: The composite electrolyte comprises an organic additive and a sulfide solid electrolyte, wherein the molar ratio of the organic additive to the sulfide solid electrolyte is 1:30~50; the organic additive comprises a solid organic small molecule or a pretreated solid organic small molecule, wherein the pretreated solid organic small molecule is obtained by pretreatment of the solid organic small molecule with a functional inorganic reactant; the molecular structure of the solid organic small molecule comprises a conjugated skeleton consisting of at least one aromatic ring, wherein the aromatic ring comprises a benzene ring or a naphthalene ring; at least one carbonyl group and at least one electron-withdrawing group are directly bonded to the conjugated skeleton, wherein the electron-withdrawing group comprises one or more of the following: fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, trifluoromethyl group, trichloromethyl group, carboxyl group, ester group, amide group, and sulfonyl group.

2. The organic small molecule-sulfide composite electrolyte according to claim 1, characterized in that: The sulfide electrolyte includes Li₂S-P₂S₅ and its doped system, Li₂S-P₂S₅-LiI and its doped system, and Li 6-x PS 5-x X 1+x and its doped systems, Li 6-x-y PS 5-x-y Cl 1+y Br x , where 0≤x≤0.7, 0.3≤y<0.6, and X includes one of Cl, Br and I.

3. The organic small molecule-sulfide composite electrolyte according to claim 1, characterized in that: The solid organic small molecules include one or more of tetrafluoro-1,4-benzoquinone, tetrachloro-1,4-benzoquinone, tetracyano-1,4-benzoquinone, 2,3,4,5-tetrafluorobenzoic acid, 2-trifluoromethylbenzoic acid, tetrafluoroterephthalic acid, 1,4-naphthoquinone, 5-fluoro-1,4-naphthoquinone, and 2-chloro-1,4-naphthoquinone.

4. The organic small molecule-sulfide composite electrolyte according to claim 1, characterized in that: The functional inorganic reactants include inorganic compounds that have reducing or Lewis acid properties.

5. The organic small molecule-sulfide composite electrolyte according to claim 4, characterized in that: The functional inorganic reactants include one or more of lithium sulfide, lithium iodide, lithium selenide, lithium phosphide, aluminum iodide, gallium iodide, and aluminum chloride.

6. A method for preparing an organic small molecule-sulfide composite electrolyte according to any one of claims 1-5, characterized in that: Includes the following steps, Under an inert atmosphere protected by argon, organic additives and sulfide solid electrolytes were mechanically ball-milled using zirconia ball milling beads at a speed of 80-150 rpm for 20-40 min and a ball-to-material mass ratio of 30-50:1 to obtain composite electrolyte powder.

7. The application of the organic small molecule-sulfide composite electrolyte according to any one of claims 1-5 in an all-solid-state lithium metal battery, characterized in that, The negative electrode of the all-solid-state lithium metal battery is metallic lithium or a lithium alloy. The all-solid-state lithium metal battery includes a composite positive electrode. The active material of the composite positive electrode includes one or more of NCM ternary materials, lithium cobalt oxide, and sulfur. The electrolyte of the all-solid-state lithium metal battery is an organic small molecule-sulfide composite electrolyte.

8. The application according to claim 7, characterized in that: The composite positive electrode sheet includes a binder and a binding aid. The binder includes polyvinylidene fluoride-hexafluoropropylene copolymer, and the binding aid includes 1,4,5,8-naphthalenetetracarboxylic anhydride. The mass ratio of the binding aid to the binder is 0.5~2.5:

19.

9. The application according to claim 7, characterized in that: The composite positive electrode sheet includes a conductive agent and a conductive additive. The conductive agent includes Ketjen black, and the conductive additive includes 3,4,9,10-pyrene tetracarboxydiimide. The mass ratio of the conductive additive to the conductive agent is 1:10~20.

10. The application according to claim 7, characterized in that: The composite positive electrode sheet has a dry film thickness of 5~25μm and an active material areal density of 1.5~2.5mg / cm³. 2 .

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