Composite sulfide solid electrolyte, positive electrode and preparation method thereof

Abstract

The invention discloses a composite sulfide solid electrolyte, a positive electrode and a preparation method thereof, the composite sulfide solid electrolyte comprises an inner core and a shell coating the surface of the inner core, the inner core comprises a nanocellulose skeleton and a sulfide solid electrolyte compounded in the nanocellulose skeleton, and the shell comprises a conductive polymer. According to the invention, an LPSC coating layer cooperatively constructed by using a nano cellulose three-dimensional skeleton and a conductive polymer conductive network provides a rapid and stable lithium ion transmission channel in the ternary positive electrode charging and discharging process, and the positive electrode material generates lattice anisotropic shrinkage caused by H1-H3 phase change during deep charging; the flexible coating structure can be tightly attached to the surface of the positive electrode by virtue of the high mechanical toughness of the framework and the elastic deformation capability of the conductive polymer, so that the coating layer is prevented from being broken.

Description

Technical Field

[0001] This application relates to the field of solid electrolyte technology, and in particular to a composite sulfide solid electrolyte, a positive electrode, and a method for preparing the same. Background Technology

[0002] With the booming development of new energy vehicles and large-scale energy storage, all-solid-state batteries are considered the ultimate solution for next-generation energy storage technology due to their "zero leakage and high energy density." Sulfide solid electrolytes (such as...) With its advantages such as room temperature conductivity close to that of liquid electrolytes and good lithium metal compatibility, sulfide electrolytes have become an ideal partner for high-nickel cathodes. However, when deeply combining sulfide electrolytes with high-nickel cathodes, existing technologies have exposed three fatal shortcomings: high-voltage-thermal coupling failure; high-nickel cathodes undergoing delithiation above 4.3 V accompanied by severe lattice contraction (H2→H3); traditional brittle sulfide coatings cannot absorb stress; microcracks propagate along grain boundaries; the coating peels off in a "scale-like" manner; interfacial impedance increases exponentially; and cycle life drops sharply. Sulfides are also air-sensitive. It is extremely sensitive to trace amounts of moisture, and irreversible hydrolysis can occur even in normal humidity environments, generating... , and Byproducts include a sharp drop in ionic conductivity and the formation of a high-resistivity interface layer; insufficient electrode preparation yield and a narrow process window severely restrict large-scale production. The lack of a three-dimensional framework and the absence of a continuous mechanical framework in traditional methods; and the low Young's modulus of the sulfide electrolyte, which easily cracks during rolling and stacking, leading to pulverization of active particles and deterioration of interfacial contact.

[0003] Existing technologies attempt to alleviate the above problems through methods such as single sulfide coating, oxide buffer layer or surface doping, but none of them can simultaneously achieve the three major functions of ion conduction, stress buffering and chemical passivation. The coating layer is prone to forming "island"-like residues during cycling, losing continuous protection.

[0004] Therefore, constructing a multi-level synergistic coating system that combines high ion transport, mechanical buffering, and chemical passivation has become a core scientific and technological bottleneck that urgently needs to be overcome in the industrialization process of sulfide-based all-solid-state high-nickel batteries. Summary of the Invention

[0005] In view of this, this application provides a method for preparing a composite sulfide solid electrolyte, which combines a nanocellulose-LPSC three-dimensional framework with a polythiophene elastic network. The three-dimensional fiber framework acts like "reinforced concrete" to suppress lattice strain transmission, while the polythiophene elastic layer absorbs micro-region deformation in real time. The two work together to make the interfacial impedance essentially change, resulting in good comprehensive performance.

[0006] This application provides a composite sulfide solid electrolyte, including a core and a shell covering the surface of the core. The core includes a nanocellulose framework and a sulfide solid electrolyte composite in the nanocellulose framework. The shell includes a conductive polymer (conductive polymer network).

[0007] This application also provides a method for preparing a composite sulfide solid electrolyte, comprising:

[0008] Sulfide solid electrolyte, nanocellulose and solvent were mixed, vacuum dried and annealed at high temperature to obtain LPSC / nanocellulose composite solid electrolyte;

[0009] The composite sulfide solid electrolyte is obtained by solvothermal reaction of LPSC / nanocellulose composite solid electrolyte, polymer monomer, crosslinking agent and oxidant.

[0010] In some specific implementations, the polymerizing monomer includes one or more of lithium thiophene-3-acetate, acetylene, pyrrole, p-phenylacetylene, thiophene, 3,4-ethylenedioxythiophene, or vinylpyrrolidone.

[0011] The crosslinking agent includes one or more of boric acid, oxalic acid, glutaraldehyde, or terephthalic acid.

[0012] The oxidant includes one or more of ferric chloride, ammonium persulfate, ferric p-toluenesulfonate, or hydrogen peroxide.

[0013] In some specific implementations, the mass ratio of the polymer monomer, crosslinking agent, oxidant and LPSC / nanocellulose composite solid electrolyte is (3.6-9):(1.4-3.5):(5-12.5):(0.02-0.1).

[0014] In some specific implementations, the solvothermal reaction is carried out in the presence of an organic solvent, which includes one or more of anisole, chlorobenzene, N,N-dimethylformamide, dimethyl sulfoxide, hexafluoroisopropanol, chloroform, acetone, tetrahydrofuran, or toluene; the mass fraction of the reaction solution in the solvothermal reaction is 5% to 40%.

[0015] The temperature of the solvothermal reaction is 60°C to 120°C, and the time of the solvothermal reaction is 4h to 24h.

[0016] The solvothermal reaction is followed by drying to obtain a composite sulfide solid electrolyte. The drying includes one or more of freeze-drying, vacuum drying, or forced-air drying. The drying time is 2 to 12 hours, and the drying temperature is 80°C to 120°C.

[0017] In some specific implementations, the sulfide solid electrolyte includes , , or One or more of the following, where X is any one or more of Cl, Br, and I, and 0.5 ≤ y ≤ 2;

[0018] The mass ratio of the sulfide solid electrolyte to nanocellulose is (4~99):1.

[0019] In some specific implementations, the solvent includes tetrahydrofuran, and the sulfide solid electrolyte has a mass percentage of 0.4 wt.% to 0.6 wt.% in the solvent.

[0020] The vacuum drying temperature is 70°C to 90°C, and the vacuum drying time is 1 hour to 3 hours; the high-temperature annealing temperature is 140°C to 160°C, and the high-temperature annealing time is 5 hours to 7 hours.

[0021] The preparation method of the sulfide solid electrolyte includes:

[0022] Lithium sulfide, lithium chloride and phosphorus pentoxide were mixed, ball-milled, heated and kept at a constant temperature to obtain a sulfide solid electrolyte.

[0023] The ball milling time is 1 hour to 4 hours, the heating rate is 0.5°C min to 5°C min, the temperature is raised to 450°C to 550°C, and the holding time is 8 hours to 24 hours.

[0024] The nanocellulose was soaked, freeze-dried, and then mixed with a sulfide solid electrolyte and a solvent.

[0025] The solvent used for soaking includes deionized water, the soaking time is 4 to 12 hours, and the number of soakings is 3 to 5.

[0026] The freeze-drying temperature is -160°C to -80°C, and the cooling and drying time is 8 hours to 24 hours.

[0027] This application also provides a composite sulfide solid electrolyte positive electrode, comprising a positive electrode material and a composite sulfide solid electrolyte coated on the surface of the positive electrode material;

[0028] The composite sulfide solid electrolyte is the composite sulfide solid electrolyte described above.

[0029] This application also provides a method for preparing a composite sulfide solid electrolyte cathode, comprising:

[0030] The positive electrode material is mixed with the composite sulfide solid electrolyte and heated and kept at that temperature to obtain the composite sulfide solid electrolyte positive electrode.

[0031] In some specific implementations, the mass ratio of the positive electrode material to the composite sulfide solid electrolyte is (0.02-0.1):(9.9-9.98).

[0032] The heating rate is 5°C / min to 10°C / min, the holding temperature is 150°C to 250°C, and the holding time is 2h to 12h.

[0033] This application utilizes an LPSC coating layer co-constructed by a three-dimensional framework of nanocellulose and a conductive polymer network. During the charge-discharge process of a high-nickel ternary cathode, this coating not only provides a fast and stable lithium-ion transport channel but also effectively suppresses interfacial side reactions. Even during deep charging, when the cathode material undergoes anisotropic lattice contraction due to the H1-H3 phase transition, this flexible coating structure, thanks to the high mechanical toughness of the nanocellulose framework and the elastic deformation capability of nanocellulose, remains tightly attached to the cathode particle surface, preventing the coating layer from cracking. This ensures highly reversible lithium-ion insertion / extraction, laying a solid foundation for long-cycle stability. Furthermore, it suppresses transition metal dissolution and interfacial side reactions, and maintains structural integrity under the dual confinement effect of nanocellulose and the conductive polymer. This multi-level buffering mechanism significantly reduces polarization growth during cycling, ensuring unobstructed lithium-ion transport pathways even after thousands of charge-discharge cycles. Detailed Implementation

[0034] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0035] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0036] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0037] The use of any and all instances or exemplary language such as “e.g.” or “include” in this document is intended merely to better illustrate the application and does not constitute a limitation on the scope of the application. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0038] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0039] Existing solutions generally employ conductive polymer coatings for the positive electrode. Because this coating layer and the softening layer cannot simultaneously absorb lattice contraction-expansion stress, microcracks arise and penetrate from the interface, exposing the highly active positive electrode surface and causing an exponential increase in charge transfer impedance. This application utilizes a polythiophene elastic network in synergy with a nanocellulose / LPSC three-dimensional framework. The elastic network undergoes reversible deformation, and the cracks are bridged by the fibers and self-heal.

[0040] The coating layer becomes unstable due to "islanding." Because existing single-layer coatings rely solely on van der Waals or weak hydrogen bonds for fixation, they peel off piece by piece under repeated expansion and contraction of the crystal lattice, forming discontinuous "islands" and disrupting ion-electron pathways. This application uses nanocellulose as "reinforcing steel," LPSC as "cement," and polythiophene as an "elastic coating." These three layers work synergistically to fix the coating through mechanical intercalation and covalent bonding. The fibers inhibit macroscopic cracking, and the elastic network reversibly heals microcracks. After multiple cycles, the coating layer remains intact and continuous, without the appearance of any "islands."

[0041] This application provides a composite sulfide solid electrolyte, including a core and a shell covering the surface of the core. The core includes a nanocellulose framework and a sulfide solid electrolyte composite in the nanocellulose framework. The shell includes a conductive polymer.

[0042] The sulfide solid electrolyte coating cathode material, which incorporates a nanocellulose crystal nucleus framework and a conductive polymer network, not only solves the interfacial stability problem of cathode materials, but also constructs a multi-level coating system that simultaneously possesses rigid ion channels, flexible stress damping, and chemical passivation barriers, thereby significantly improving the cycle stability of the battery.

[0043] This application also provides a method for preparing a composite sulfide solid electrolyte, comprising:

[0044] Sulfide solid electrolyte, nanocellulose and solvent were mixed, vacuum dried and annealed at high temperature to obtain LPSC / nanocellulose composite solid electrolyte;

[0045] The composite sulfide solid electrolyte is obtained by solvothermal reaction of LPSC / nanocellulose composite solid electrolyte, polymer monomer, crosslinking agent and oxidant.

[0046] Nanofibers act as "steel bars" to disperse mechanical stress, while sulfide solid electrolytes act as "cement" to maintain ion channels. After co-sintering, they form a continuous and crack-resistant composite skeleton, which significantly inhibits "islanding" and spalling.

[0047] This application first mixes a sulfide solid electrolyte, nanocellulose, and a solvent, then vacuum dries and anneals at high temperature to obtain an LPSC / nanocellulose composite solid electrolyte.

[0048] In some specific implementations, the sulfide solid electrolyte includes , , or One or more of the following, where X is any one or more of Cl, Br, and I, and 0.5 ≤ y ≤ 2; this application does not have special requirements for the selection of nanocellulose, and the mass ratio of the sulfide solid electrolyte to nanocellulose is (4~99):1. In some specific implementations, the diameter of the nanocellulose is 50 nm to 200 nm.

[0049] In some specific implementations, the solvent includes, but is not limited to, tetrahydrofuran. This application does not have special requirements for the selection of solvent. The mass percentage of the sulfide solid electrolyte in the solvent is 0.4 wt.% to 0.6 wt.%. The vacuum drying temperature is 70°C to 90°C, and the vacuum drying time is 1 h to 3 h. The high-temperature annealing temperature is 140°C to 160°C, and the high-temperature annealing time is 5 h to 7 h.

[0050] In some specific implementations, the preparation method of the sulfide solid electrolyte includes:

[0051] Lithium sulfide, lithium chloride and phosphorus pentoxide were mixed, ball-milled, heated and kept at a constant temperature to obtain a sulfide solid electrolyte.

[0052] The ball milling time is 1 to 4 hours, the heating rate is 0.5℃ / min, the temperature is raised to 450℃ to 550℃, and the holding time is 8 to 24 hours. The ball-to-material mass ratio in the ball milling process is (4-20):1.

[0053] In some specific implementations, the nanocellulose is soaked, freeze-dried, and then mixed with a sulfide solid electrolyte and a solvent;

[0054] The solvent used for soaking includes deionized water, the soaking time is 4 to 12 hours, and the number of soakings is 3 to 5.

[0055] The freeze-drying temperature is -160°C to -80°C, and the cooling and drying time is 8 hours to 24 hours.

[0056] This application then mixes the LPSC / nanocellulose composite solid electrolyte, polymeric monomers, crosslinking agents, and oxidants in a solvothermal reaction to obtain a composite sulfide solid electrolyte. In some specific implementations, the polymeric monomers include one or more of lithium thiophene-3-acetate, acetylene, pyrrole, p-phenylacetylene, thiophene, 3,4-ethylenedioxythiophene, or vinylpyrrolidone.

[0057] The crosslinking agent includes, but is not limited to, one or more of boric acid, oxalic acid, glutaraldehyde or terephthalic acid. This application does not have any special requirements for the selection of the crosslinking agent.

[0058] The oxidizing agent includes, but is not limited to, one or more of ferric chloride, ammonium persulfate, ferric p-toluenesulfonate, or hydrogen peroxide. This application does not have any special requirements for the selection of the oxidizing agent.

[0059] In some specific implementations, the mass ratio of the polymer monomer, crosslinking agent, oxidant and LPSC / nanocellulose composite solid electrolyte is (3.6-9):(1.4-3.5):(5-12.5):(0.02-0.1).

[0060] In some specific implementations, the solvothermal reaction is carried out in the presence of an organic solvent, which includes, but is not limited to, one or more of anisole, chlorobenzene, N,N-dimethylformamide, dimethyl sulfoxide, hexafluoroisopropanol, chloroform, acetone, tetrahydrofuran, or toluene. This application does not have specific requirements for the selection of the organic solvent; the mass fraction of the reaction solution in the solvothermal reaction is 5% to 40%.

[0061] The temperature of the solvothermal reaction is 60°C to 120°C, and the time of the solvothermal reaction is 4h to 24h.

[0062] The solvothermal reaction is followed by drying to obtain a composite sulfide solid electrolyte. The drying includes one or more of freeze-drying, vacuum drying, or forced-air drying. The drying time is 2 to 12 hours, and the drying temperature is 80°C to 120°C.

[0063] This application also provides a composite sulfide solid electrolyte positive electrode, comprising a positive electrode material and a composite sulfide solid electrolyte coated on the surface of the positive electrode material;

[0064] The composite sulfide solid electrolyte is the composite sulfide solid electrolyte described above.

[0065] In some specific implementations, the composite sulfide solid electrolyte accounts for 0.1%-5% of the mass fraction of the composite cathode material.

[0066] This application also provides a method for preparing a composite sulfide solid electrolyte cathode, comprising:

[0067] The positive electrode material is mixed with the composite sulfide solid electrolyte and heated and kept at that temperature to obtain the composite sulfide solid electrolyte positive electrode.

[0068] Slow oxidative polymerization and esterification crosslinking at a low temperature of 60°C generate a 1–2 nm polythiophene-boronate elastic network on the LPSC / fiber surface within 24 hours, forming a covalently bonded interface. The slurry ensures an ultra-thin and uniform coating layer, and long-term annealing at 150°C promotes network softening and tight adhesion to the cathode particles, achieving full surface coating and avoiding damage to polymer chains at high temperatures.

[0069] In some specific implementations, the mass ratio of the positive electrode material to the composite sulfide solid electrolyte is (0.02-0.1):(9.9-9.98).

[0070] The heating rate is 5°C / min to 10°C / min, the holding temperature is 150°C to 250°C, and the holding time is 2h to 12h. In some specific implementations, the positive electrode includes an NCM9244 positive electrode.

[0071] The present application is further illustrated below with reference to embodiments. The scope of protection of the present application is not limited to the following embodiments.

[0072] Example 1

[0073] This embodiment provides a composite sulfide solid electrolyte, the preparation method of which includes:

[0074] Step 1: Preparation of nanocellulose-solid electrolyte precursor

[0075] Take 2g of wet nanocellulose hydrogel, soak and rinse it three times with deionized water for 12 hours each time to remove residual culture medium. Freeze-dry the nanocellulose at -80°C for 24 hours to maintain its three-dimensional porous structure.

[0076] lithium sulfide With lithium chloride (LiCl) and phosphorus pentoxide The precursor was added to a ball mill jar at a preset molar ratio (5:2:1) and ball-milled at high speed for 4 hours under an inert atmosphere to form a sulfide solid electrolyte precursor. The solid precursor was then placed in a tube furnace and milled at high speed under an inert atmosphere. The temperature was raised to 500°C and held for 8 hours to obtain a composite sulfide solid electrolyte. The powder was added to anhydrous THF at a concentration of 0.5 wt%, and the mixture was magnetically stirred at 50°C for 24 h in an argon glove box until a pale yellow transparent solution was obtained. The nanocellulose framework was then impregnated with this solution and vacuum-dried at 80°C for 2 h. Finally, the composite was annealed in a vacuum tube furnace at 150°C for 6 h to allow it to... In-situ crystallization on the surface of nanocellulose forms continuous ion channels.

[0077] Step 2: Introduction and in-situ composite of polythiophene (PTh)

[0078] 3.75g of polymerization monomer (lithium thiophene-3-acetate (TAA-Li)) and 1.25g of boric acid were added. 5g oxidant Dissolve in 90g of anhydrous anisole (or chlorobenzene) to prepare a 10wt% solution;

[0079] The LPSC / fiber composite solid electrolyte was introduced into the solution to prepare a 20wt% solution. The mixture was then transferred to a polytetrafluoroethylene reactor and placed in an oven at 60°C for a solvothermal reaction for 24 hours. After the reaction was completed, the solvent and powder were separated by centrifugation and then dried in a vacuum oven at 80°C for 12 hours to remove residual solvent, thus obtaining the composite sulfide solid electrolyte.

[0080] Step 3: Coating the composite electrolyte with the cathode material

[0081] Next, 0.02g of nanocellulose framework, composite sulfide solid electrolyte, and 9.98g of dried NCM9244 cathode powder were mixed evenly using a high-speed mixer, and then placed in a tube furnace under an inert atmosphere. The temperature was raised to 150 °C and held for 12 h to obtain a composite sulfide solid electrolyte cathode.

[0082] Example 2

[0083] This embodiment provides a composite sulfide solid electrolyte, the preparation method of which includes:

[0084] Step 1: Preparation of nanocellulose-solid electrolyte precursor

[0085] Take 5g of wet nanocellulose hydrogel, soak and rinse it 5 times with deionized water for 4 hours each time to remove residual culture medium. Freeze-dry the nanocellulose at -160°C for 8 hours to maintain its three-dimensional porous structure.

[0086] Lithium sulfide, lithium chloride (LiCl), and phosphorus pentoxide were added to a ball mill jar at a predetermined molar ratio (4:3:1) and ball-milled at high speed for 3 hours under an inert atmosphere to form a sulfide solid electrolyte precursor. The solid precursor was then placed in a tube furnace and milled at high speed under an inert atmosphere. The temperature was raised to 450°C and held for 24 hours to obtain a composite sulfide solid electrolyte. The powder was added to anhydrous THF at a concentration of 0.5 wt%, and the mixture was magnetically stirred at 70°C for 12 h in an argon glove box until a pale yellow transparent solution was obtained. The nanocellulose framework was then impregnated with this solution and vacuum-dried at 80°C for 2 h. Finally, the composite was annealed in a vacuum tube furnace at 150°C for 6 h to allow it to... In-situ crystallization on the surface of nanocellulose forms continuous ion channels.

[0087] Step 2: Introduction and in-situ composite of polythiophene (PTh)

[0088] Dissolve 1.875 g of the monomer (lithium thiophene-3-acetate (TAA-Li)), 0.625 g of boric acid, and 2.5 g of oxidant in 95 g of chlorobenzene to prepare a 5 wt% solution;

[0089] The LPSC / nanocellulose composite solid electrolyte was prepared to a concentration of 30 wt%. This mixture was then transferred to a polytetrafluoroethylene (PTFE) reactor and subjected to a solvothermal reaction at 120 °C for 4 hours. After the reaction, the solvent and powder were separated by centrifugation, and then dried in a vacuum oven at 120 °C for 2 hours to remove residual solvent, yielding a product containing a nanocellulose framework and a polythiophene network. (Composite sulfide solid electrolyte cathode).

[0090] Step 3: Coating the composite electrolyte with the cathode material

[0091] Next, 0.1 g of the composite sulfide solid electrolyte cathode and 9.9 g of dried NCM9244 cathode powder were mixed evenly using a high-speed mixer, and then placed in a tube furnace under an inert atmosphere. The temperature was raised to 250 °C and held for 2 hours to obtain a composite sulfide solid electrolyte cathode.

[0092] Example 3

[0093] This embodiment provides a composite sulfide solid electrolyte, the preparation method of which includes:

[0094] Step 1: Preparation of nanocellulose-solid electrolyte precursor

[0095] Take 5g of wet nanocellulose hydrogel, soak and rinse it four times with deionized water for 8 hours each time to remove residual culture medium. Freeze-dry the nanocellulose at -120°C for 16 hours to maintain its three-dimensional porous structure.

[0096] Lithium sulfide, lithium chloride (LiCl), and phosphorus pentoxide were added to a ball mill jar at a predetermined molar ratio (4:3:1) and ball-milled at high speed for 4 hours under an inert atmosphere to form a sulfide solid electrolyte precursor. The solid precursor was then placed in a tube furnace and milled at high speed under an inert atmosphere. The temperature was raised to 550 °C and held for 8 h to obtain a composite sulfide solid electrolyte. The powder was added to anhydrous THF at a concentration of 0.5 wt%, and the mixture was magnetically stirred at 70°C for 12 h in an argon glove box until a pale yellow transparent solution was obtained. The nanocellulose framework was then impregnated with this solution and vacuum-dried at 80°C for 2 h. Finally, the composite was annealed in a vacuum tube furnace at 150°C for 6 h to allow it to... In-situ crystallization on the surface of nanocellulose forms continuous ion channels.

[0097] Step 2: Introduction and in-situ composite of polythiophene (PTh)

[0098] 5.625 g of polymer monomer (lithium thiophene-3-acetate (TAA-Li)), 1.875 g of crosslinking agent (boric acid), and 7.5 g of oxidant (ferric chloride) were dissolved in 85 g of chlorobenzene to prepare a 15 wt% solution;

[0099] LPSC / nanocellulose composite solid electrolyte was added to prepare a 40 wt% solution. The mixture was then transferred to a polytetrafluoroethylene reactor and placed in an oven at 100 °C for a solvothermal reaction for 6 h. After the reaction was completed, the solvent and powder were separated by centrifugation and then dried in a vacuum oven at 100 °C for 4 h to remove residual solvent, thus obtaining LPSC containing a nanocellulose framework and a polythiophene network.

[0100] Step 3: Coating the composite electrolyte with the cathode material

[0101] Next, 0.05 g of LPSC with a nanocellulose framework and polythiophene network was mixed with 9.95 g of dried NCM9244 cathode powder using a high-speed mixer until homogeneous. The mixture was then placed in a tube furnace and heated under an inert atmosphere. The temperature was raised to 200 °C and held for 4 h to obtain a composite sulfide solid electrolyte cathode.

[0102] Example 4

[0103] This embodiment provides a composite sulfide solid electrolyte, the preparation method of which includes:

[0104] Step 1: Preparation of nanocellulose-solid electrolyte precursor

[0105] Take 5g of wet nanocellulose hydrogel, soak and rinse it three times with deionized water for 6 hours each time to remove residual culture medium. Freeze-dry the nanocellulose at -160°C for 8 hours to maintain its three-dimensional porous structure.

[0106] Lithium sulfide, lithium chloride (LiCl), and phosphorus pentoxide were added to a ball mill jar at a predetermined molar ratio (5:2:1) and ball-milled at high speed for 4 hours under an inert atmosphere to form a sulfide solid electrolyte precursor. The solid precursor was then placed in a tube furnace and milled at high speed under an inert atmosphere. The temperature was raised to 550 °C and held for 8 h to obtain a composite sulfide solid electrolyte. The powder was added to anhydrous THF at a concentration of 0.5 wt%, and the mixture was magnetically stirred at 70°C for 12 h in an argon glove box until a pale yellow transparent solution was obtained. The nanocellulose framework was then impregnated with this solution and vacuum-dried at 80°C for 2 h. Finally, the composite was annealed in a vacuum tube furnace at 150°C for 6 h to allow it to... In-situ crystallization on the surface of nanocellulose forms continuous ion channels;

[0107] Step 2: Introduction and in-situ composite of poly(3,4-ethylenedioxythiophene)PEDOT

[0108] Dissolve 4g of polymer monomer (ethylene dioxythiophene lithium salt (EDOT-Li)), 1.2g of crosslinking agent (sodium persulfate), and 0.8g of oxidant (ferric p-toluenesulfonate) in 94g of chlorobenzene to prepare a 6wt% solution;

[0109] LPSC / nanocellulose composite solid electrolyte was added to prepare a 40 wt% solution. The mixture was then transferred to a polytetrafluoroethylene reactor and placed in an oven at 100 °C for a solvothermal reaction for 6 h. After the reaction was completed, the solvent and powder were separated by centrifugation and then dried in a vacuum oven at 100 °C for 4 h to remove residual solvent, thus obtaining LPSC containing a nanocellulose framework and a PEDOT network.

[0110] Step 3: Coating the composite electrolyte with the cathode material

[0111] Next, 0.05 g of nanocellulose framework and PEDOT network LPSC were mixed with 9.95 g of dried NCM9244 cathode powder using a high-speed mixer until homogeneous. The mixture was then placed in a tube furnace and heated under an inert atmosphere. The temperature was raised to 200 °C and held for 4 h to obtain a composite sulfide solid electrolyte cathode.

[0112] Example 5

[0113] This embodiment provides a composite sulfide solid electrolyte, the preparation method of which includes:

[0114] Step 1: Preparation of nanocellulose-solid electrolyte precursor

[0115] Take 5g of wet nanocellulose hydrogel, soak and rinse it 5 times with deionized water for 4 hours each time to remove residual culture medium. Freeze-dry the nanocellulose at -100°C for 12 hours to maintain its three-dimensional porous structure.

[0116] Lithium sulfide, lithium chloride (LiCl), and phosphorus pentoxide were added to a ball mill jar at a predetermined molar ratio (4:3:1) and ball-milled at high speed for 4 hours under an inert atmosphere to form a sulfide solid electrolyte precursor. The solid precursor was then placed in a tube furnace and milled at high speed under an inert atmosphere. The temperature was raised to 550 °C and held for 8 h to obtain a composite sulfide solid electrolyte. The powder was added to anhydrous THF at a concentration of 0.5 wt%, and the mixture was magnetically stirred at 70°C for 12 h in an argon glove box until a pale yellow transparent solution was obtained. The nanocellulose framework was then impregnated with this solution and vacuum-dried at 80°C for 2 h. Finally, the composite was annealed in a vacuum tube furnace at 150°C for 6 h to allow it to... In-situ crystallization on the surface of nanocellulose forms continuous ion channels;

[0117] Step 2: Introduction and in-situ composite of polypyrrole (PPy)

[0118] 3.0 g of polymer monomer (lithium pyrrole-3-carboxylate), 1.0 g of crosslinking agent (sodium dodecylbenzenesulfonate), and 6.0 g of oxidizing agent (ferric p-toluenesulfonate (III)) were dissolved in 90 g of anisole to prepare a 10 wt% solution;

[0119] LPSC / nanocellulose composite solid electrolyte was added to prepare a 30 wt.% solution. The mixture was then transferred to a polytetrafluoroethylene reactor and placed in an oven at 100 °C for a solvothermal reaction for 6 h. After the reaction was completed, the solvent and powder were separated by centrifugation and then dried in a vacuum oven at 100 °C for 4 h to remove residual solvent, thus obtaining LPSC containing a nanocellulose framework and a PEDOT network.

[0120] Step 3: Coating the composite electrolyte with the cathode material

[0121] Next, 0.05 g of nanocellulose framework and PEDOT network LPSC were mixed with 9.95 g of dried NCM9244 cathode powder using a high-speed mixer until homogeneous. The mixture was then placed in a tube furnace and heated under an inert atmosphere. The temperature was raised to 200 °C and held for 4 h to obtain a composite sulfide solid electrolyte cathode.

[0122] Comparative Example 1

[0123] This embodiment provides a composite sulfide solid electrolyte. The only difference between the preparation method of the composite sulfide solid electrolyte and that of Embodiment 1 is that PTh is not added.

[0124] Comparative Example 2

[0125] This embodiment provides a composite sulfide solid electrolyte. The only difference between the preparation method of the composite sulfide solid electrolyte and that of Embodiment 2 is that LPSC is not added.

[0126] Comparative Example 3

[0127] This embodiment provides a composite sulfide solid electrolyte. The preparation method of the composite sulfide solid electrolyte differs from that of Embodiment 3 only in that the composite sulfide solid electrolyte is directly mixed with NCM9244 and dispersed in chlorobenzene.

[0128] Comparative Example 4

[0129] This embodiment provides a composite sulfide solid electrolyte. The preparation method of the composite sulfide solid electrolyte differs from that of Example 4 only in that the crosslinking agent is replaced with chlorobenzene.

[0130] Comparative Example 5

[0131] This embodiment provides a composite sulfide solid electrolyte. The only difference between the preparation method of the composite sulfide solid electrolyte and that of Embodiment 5 is that freeze drying is replaced with conventional drying.

[0132] The performance of the composite sulfide solid electrolytes provided in Examples 1-5 and Comparative Examples 1-5 was tested using the following methods:

[0133] At 100 MPa, 0.1 g of sulfide solid electrolyte was first pressed into an intermediate layer sheet; then, 18.3 mg of positive electrode mixture was placed on the positive electrode side of the intermediate layer, covered with carbon-coated aluminum foil, and pressed into a sheet at 300 MPa; finally, lithium sheet was used as the negative electrode to complete the battery assembly, and tests were carried out under multiple rate conditions. The test results are shown in Table 1-2.

[0134] Table 1

[0135]

[0136] Table 1 clearly shows that the first-cycle coulombic efficiency of Examples 1-5 is significantly better than that of Comparative Examples 1-5. This fully demonstrates that the LPSC coating layer, synergistically constructed by the three-dimensional framework of nanocellulose and the polythiophene conductive network, not only provides a fast and stable lithium-ion transport channel during the charging and discharging process of the NCM9244 cathode, but also effectively suppresses interfacial side reactions. Crucially, even when the cathode material undergoes anisotropic lattice contraction caused by the H1-H3 phase transition during deep charging, this flexible coating structure can still adhere tightly to the surface of the NCM9244 particles thanks to the high mechanical toughness of the nanocellulose framework and the elastic deformation capability of polythiophene, preventing the coating layer from breaking. This ensures the high reversibility of lithium-ion insertion / extraction, laying a solid foundation for long-term cycle stability. The table above clearly shows that the cycle stability of Examples 1-5 is significantly better than that of Comparative Examples 1-5. This fully demonstrates that the LPSC coating layer, synergistically constructed by the three-dimensional framework of nanocellulose and the polythiophene conductive network, forms a composite interface on the surface of the NCM9244 cathode that combines mechanical toughness and ion transport functions. During repeated lithium insertion / extraction processes, the nanofiber framework effectively mitigates stress concentration caused by volume changes in the active material due to its interwoven nanofiber structure, while the polythiophene network provides a continuous electron conduction pathway, preventing localized electrochemical failure. Simultaneously, the LPSC coating layer, acting as an artificial SEI film, suppresses transition metal dissolution and interfacial side reactions, and maintains structural integrity under the dual confinement effect of nanofiber and polythiophene. This multi-level buffering mechanism significantly reduces polarization growth during cycling, ensuring unobstructed lithium-ion transport pathways even after thousands of charge-discharge cycles.

[0137] Table 2

[0138]

[0139] As can be clearly seen from Table 2, the impedance of the first loop in Examples 1-5 is lower than that in Comparative Examples 1-5. This indicates that the highly efficient ion / electron dual continuous transport channel constructed by the three-dimensional conductive network of nanocellulose and polythiophene significantly reduces the charge transfer resistance, making... Rapid migration at the electrode / electrolyte interface reduces irreversible capacity loss during the first charge and discharge cycle.

[0140] The internal resistance increase after 200 cycles in the all-solid-state battery in Examples 1-5 was lower than that in the comparative example. This is attributed to the synergistic stabilization mechanism of the three-dimensional framework of nanocellulose and the polythiophene network: the former effectively suppresses the anisotropic volume expansion and pulverization of NCM9244 particles during charge and discharge processes through its high-strength interwoven nanofiber structure, maintaining electrical contact between cathode particles; the latter, through its chemical stability and electronic conductivity, prevents the continuous accumulation of by-reaction products at the solid electrolyte-cathode interface. Together, they ensure the structural integrity of the LPSC coating layer and the solid electrolyte layer, significantly suppressing the increase in mass transfer impedance caused by stress accumulation and interface degradation, enabling the all-solid-state battery to maintain low polarization and efficient ion transport even after long cycles.

[0141] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A composite sulfide solid electrolyte, characterized in that, It includes a core and a shell covering the surface of the core. The core includes a nanocellulose framework and a sulfide solid electrolyte compounded in the nanocellulose framework. The shell includes a conductive polymer.

2. A method for preparing a composite sulfide solid electrolyte, characterized in that, include: Sulfide solid electrolyte, nanocellulose and solvent were mixed, vacuum dried and annealed at high temperature to obtain LPSC / nanocellulose composite solid electrolyte; The composite sulfide solid electrolyte is obtained by solvothermal reaction of LPSC / nanocellulose composite solid electrolyte, polymer monomer, crosslinking agent and oxidant.

3. The preparation method according to claim 2, characterized in that, The polymerizing monomers include one or more of lithium thiophene-3-acetate, acetylene, pyrrole, p-phenylacetylene, thiophene, 3,4-ethylenedioxythiophene, or vinylpyrrolidone. The crosslinking agent includes one or more of boric acid, oxalic acid, glutaraldehyde, or terephthalic acid. The oxidant includes one or more of ferric chloride, ammonium persulfate, ferric p-toluenesulfonate, or hydrogen peroxide.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the polymer monomer, crosslinking agent, oxidant and LPSC / nanocellulose composite solid electrolyte is (3.6-9):(1.4-3.5):(5-12.5):(0.02-0.1).

5. The preparation method according to claim 2, characterized in that, The solvothermal reaction is carried out in the presence of an organic solvent, which includes one or more of anisole, chlorobenzene, N,N-dimethylformamide, dimethyl sulfoxide, hexafluoroisopropanol, chloroform, acetone, tetrahydrofuran, or toluene; the mass fraction of the reaction solution in the solvothermal reaction is 5% to 40%. The temperature of the solvothermal reaction is 60°C to 120°C, and the time of the solvothermal reaction is 4h to 24h. The solvothermal reaction is followed by drying to obtain a composite sulfide solid electrolyte; the drying includes one or more of freeze-drying, vacuum drying or forced-air drying, the drying time is 2h to 12h, and the drying temperature is 80℃ to 120℃.

6. The preparation method according to claim 2, characterized in that, The sulfide solid electrolyte includes , , or One or more of the following, where X is any one or more of Cl, Br, and I, and 0.5 ≤ y ≤ 2; The mass ratio of the sulfide solid electrolyte to nanocellulose is (4~99):

1.

7. The preparation method according to claim 2, characterized in that, The solvent comprises tetrahydrofuran, and the sulfide solid electrolyte has a mass percentage of 0.4 wt.% to 0.6 wt.% in the solvent. The vacuum drying temperature is 70°C to 90°C, and the vacuum drying time is 1 hour to 3 hours; the high-temperature annealing temperature is 140°C to 160°C, and the high-temperature annealing time is 5 hours to 7 hours. The preparation method of the sulfide solid electrolyte includes: Lithium sulfide, lithium chloride and phosphorus pentoxide were mixed, ball-milled, heated and kept at a constant temperature to obtain a sulfide solid electrolyte. The ball milling time is 1 hour to 4 hours, the heating rate is 0.5°C min to 5°C min, the temperature is raised to 450°C to 550°C, and the holding time is 8 hours to 24 hours. The nanocellulose was soaked, freeze-dried, and then mixed with a sulfide solid electrolyte and a solvent. The solvent used for soaking includes deionized water, the soaking time is 4 to 12 hours, and the number of soakings is 3 to 5. The freeze-drying temperature is -160°C to -80°C, and the cooling and drying time is 8 hours to 24 hours.

8. A composite sulfide solid electrolyte positive electrode, characterized in that, This includes the cathode material and the composite sulfide solid electrolyte coated on the surface of the cathode material; The composite sulfide solid electrolyte is the composite sulfide solid electrolyte as described in claim 1.

9. A method for preparing a composite sulfide solid electrolyte positive electrode, characterized in that, include: The positive electrode material is mixed with the composite sulfide solid electrolyte and heated and kept at that temperature to obtain the composite sulfide solid electrolyte positive electrode.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the positive electrode material to the composite sulfide solid electrolyte is (0.02-0.1):(9.9-9.98). The heating rate is 5°C / min to 10°C / min, the holding temperature is 150°C to 250°C, and the holding time is 2h to 12h.

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