Silicon negative electrode and preparation method thereof and sulfide solid-state battery

Abstract

This application provides a silicon anode, its preparation method, and a sulfide solid-state battery, relating to the field of solid-state battery technology. A method for preparing a silicon anode involves mixing a silicon-based material, a conductive additive, a first polymer, and a first solvent to obtain an electrospinning precursor solution; electrospinning the precursor solution to form a fiber film on one side of a receiving substrate; sintering to obtain a silicon anode precursor; mixing a sulfide solid electrolyte, a second polymer, and a second solvent to obtain an electrolyte composite slurry; coating the slurry onto the surface of the silicon anode precursor to obtain a silicon anode; the total amount of the silicon-based material, conductive additive, and first polymer is 100%, with the silicon-based material comprising 60%–80%, the conductive additive 10%–20%, and the first polymer 10%–20%; the total amount of the sulfide solid electrolyte and the second polymer is 100%, with the sulfide solid electrolyte comprising 70%–90% and the second polymer 10%–30%. This application improves the ionic and electronic conductivity of the silicon anode and alleviates the volume expansion of the silicon anode.

Description

Technical Field

[0001] This disclosure relates to the field of solid-state battery technology, and in particular to a silicon anode, a method for preparing the same, and a sulfide solid-state battery. Background Technology

[0002] Silicon-based anodes are known for their high theoretical specific capacity (Li). 22 Si5, 4200 mAh g -1 ) and low electrode potential (0.4 Vvs Li + Silicon anodes, with their advantages such as lithium-ion peroxide (Li₂O₃) and silicon-based materials, are widely used in solid-state lithium-ion batteries. However, their inherent volume effect and low electronic conductivity hinder the efficient transport of lithium ions within the silicon anode and continuously disrupt the structural integrity of the conductive network, ultimately leading to significant distortion of the electrochemical reaction field and stress within the silicon anode. This not only reduces the utilization rate of the active material but also accelerates the irreversible degradation of the silicon anode structure, ultimately limiting the battery's cycle life and rate performance. Therefore, regulating the synergistic distribution of ions and electrons within the silicon anode and effectively suppressing the volume expansion of silicon materials is the core path to overcoming the current technological challenges of silicon-based anodes. Summary of the Invention

[0003] This application provides a silicon anode, a method for preparing the same, and a sulfide solid-state battery, to at least solve one of the technical problems existing in the prior art.

[0004] In a first aspect, this application provides a method for preparing a silicon anode, the method comprising: A silicon-based material, conductive additive, first polymer, and first solvent are uniformly mixed to obtain an electrospinning precursor solution; using a negative electrode current collector as a receiving substrate, the electrospinning precursor solution is electrospinned to form a fiber film on one side of the receiving substrate; then, it is sintered in an inert atmosphere to obtain a silicon negative electrode precursor. A sulfide solid electrolyte, a second polymer, and a second solvent are uniformly mixed to obtain an electrolyte composite slurry. The electrolyte composite slurry is uniformly coated onto the surface of the fiber membrane of the silicon anode precursor and then vacuum dried to obtain the silicon anode. Wherein, based on the total mass of the silicon-based material, conductive additive, and first polymer as 100%, the mass percentage of the silicon-based material is 60%~80%, the mass percentage of the conductive additive is 10%~20%, and the mass percentage of the first polymer is 10%~20%; the solid content of the electrospinning precursor solution is 10%~30%. Based on the total mass of the sulfide solid electrolyte and the second polymer as 100%, the mass percentage of the sulfide solid electrolyte is 70% to 90%, and the mass percentage of the second polymer is 10% to 30%; the solid content of the electrolyte composite slurry is 10% to 30%.

[0005] In one embodiment, based on the total mass of the silicon-based material, conductive additive, and first polymer being 100%, the mass percentage of the silicon-based material is 70% to 80%, the mass percentage of the conductive additive is 10% to 15%, and the mass percentage of the first polymer is 10% to 15%. The solid content of the electrospinning precursor solution is 10%~20%.

[0006] In one embodiment, with the total mass of the sulfide solid electrolyte and the second polymer being 100%, the mass percentage of the sulfide solid electrolyte is 80% to 90%, and the mass percentage of the second polymer is 10% to 20%. The solid content of the electrolyte composite slurry is 10%~20%.

[0007] In one embodiment, the porosity of the silicon anode precursor is 60% to 80%.

[0008] In one embodiment, the thickness of the fiber film of the silicon anode precursor is 5-10 μm; the thickness of the silicon anode is 20-35 μm.

[0009] In one embodiment, the electrospinning requires a voltage of 20 kV, a flow rate of 2 mL / h, and a receiving distance of 10 cm.

[0010] In one embodiment, the sintering temperature is 500℃~700℃, and the sintering time is 1h~5h; The vacuum drying temperature is 80℃~100℃, and the vacuum drying time is 8h~12h.

[0011] In one embodiment, the silicon-based material is at least one of nano-Si particles, micron-sized Si particles, Si nanowires, Si nanotubes, nanoporous Si, micron-sized porous Si, Si nanofilms, SiOx, Si / C, Si alloys, Si-metal oxide composite materials, pre-lithiated Si-based materials, Si-graphite composite particles, and Si-based core-shell structures. The conductive additive is at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, graphene, carbon nanofibers, carbonized polymer-derived carbon, and MXene materials. The first polymer is at least one of polyether, polyester and polyolefin; The first solvent is at least one of dimethylformamide, dimethylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, diethyl carbonate, dimethyl carbonate, and ethylene carbonate; The sulfide solid electrolyte is Li3PS4 or Li7P3S. 11 Li6PS5Cl, Li5.5 PS 4.5 Cl 1.5 Li 5.8 PS 4.8 Cl 1.2 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li6PS5Br, Li6PS5I, Li7P2S8I, Li 10 SnP2S 12 Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 At least one of S4 and 70Li2S·30P2S5; The second polymer is at least one of nitrile rubber, hydrogenated nitrile rubber, polybutadiene, polyisoprene, polystyrene, polyisobutylene, polyethylene, polypropylene, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer, styrene-ethylene-styrene block copolymer, styrene-butene-styrene block copolymer, and polydimethylsiloxane; The second solvent is at least one selected from butyl butyrate, toluene, xylene, ethylbenzene, mesitylene, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, and decahydronaphthalene.

[0012] Secondly, this application provides a silicon anode, which is prepared by any of the preparation methods described above.

[0013] Thirdly, this application provides a sulfide solid-state battery, including a silicon anode prepared by any of the above-described preparation methods, or the silicon anode described above.

[0014] Compared with the prior art, the advantages of this application are: (1) significantly improving the ionic and electronic conductivity inside the silicon anode electrode: A three-dimensional conductive network was constructed through electrospinning, forming a continuous electron transport pathway. Subsequently, capillary action was used to uniformly fill the pores with an electrolyte composite slurry prepared from a sulfide solid electrolyte, constructing a continuous ion transport channel. This integrated structure, where the "electronic framework" and "ion channels" are intertwined, achieves simultaneous optimization of ion and electron transport paths, significantly reduces the interfacial impedance inside the silicon anode electrode, and improves charge transport dynamics.

[0015] (2) Effectively alleviates the volume expansion of silicon anodes and improves structural stability: The three-dimensional porous fiber framework provides ample buffer space for the massive volume expansion (~300%) of the silicon-based material during charge and discharge. Simultaneously, high-temperature sintering enhances the mechanical strength of the framework, while the subsequently filled electrolyte composite slurry acts as a flexible binder. This structural design effectively adapts to volume changes, preventing the pulverization of active materials and the collapse of the electrode structure, thereby significantly improving the cycle life of the silicon anode electrode.

[0016] (3) Achieving an ultra-thin integrated silicon anode electrode structure helps to improve battery energy density: An integrated ultrathin silicon anode with a total thickness of only 20-35 micrometers was successfully fabricated, exhibiting a high active material loading. This ultrathin design significantly reduces the proportion of inactive materials, providing a key technological path for improving the gravimetric and volumetric energy density of all-solid-state batteries.

[0017] (4) The process also has the potential for large-scale production: The key steps of this process (electrospinning, coating, and drying) have controllable parameters and mild conditions, and are highly compatible with existing battery manufacturing processes, laying the foundation for the controllable preparation and large-scale production of high-performance solid-state battery electrodes.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Detailed Implementation

[0019] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below in conjunction with the embodiments of this disclosure. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0020] In a first aspect, this application provides a method for preparing a silicon anode, the method comprising the following steps: Step 1) A silicon-based material, conductive additive, first polymer and first solvent are uniformly mixed to obtain an electrospinning precursor solution; the electrospinning precursor solution is passed through an electrospinning process to form a fiber film on one side of the receiving substrate using a negative electrode current collector as the receiving substrate; and then sintered in an inert atmosphere to obtain a silicon negative electrode precursor. Step 2) The sulfide solid electrolyte, the second polymer and the second solvent are uniformly mixed to obtain an electrolyte composite slurry. The electrolyte composite slurry is uniformly coated on the surface of the fiber membrane of the silicon anode precursor and vacuum dried to obtain the silicon anode. Of these, taking the total mass of silicon-based materials, conductive additives, and the first polymer as 100%, the mass percentage of silicon-based materials is 60%–80%, the mass percentage of conductive additives is 10%–20%, and the mass percentage of the first polymer is 10%–20%; the solid content of the electrospinning precursor solution is 10%–30%. Based on the total mass of the sulfide solid electrolyte and the second polymer as 100%, the mass ratio of the sulfide solid electrolyte is 70%~90%, and the mass ratio of the second polymer is 10%~30%; the solid content of the electrolyte composite slurry is 10%~30%.

[0021] For example, in this application, copper foil is used as the negative electrode current collector material, serving as the receiving substrate. The thickness of the copper foil is 10~15 μm. Choosing this thickness helps reduce the overall mass and volume of the silicon negative electrode, increasing the battery energy density, while ensuring that the substrate has sufficient mechanical strength to support the deposition and transfer of the electrospun fiber membrane.

[0022] For example, in the method of this application, silicon-based materials, conductive additives, and a first polymer are uniformly dispersed in a first solvent to form an electrospinning precursor solution. A three-dimensional continuous fiber network is then constructed on a copper foil receiving substrate using an electrospinning process (i.e., using copper foil as the receiving substrate, the electrospinning precursor solution is spun into a three-dimensional network structure fiber membrane (i.e., a fiber membrane) under set voltage, flow rate, and receiving distance). The conductive additives coat and connect the silicon-based particles, forming an electron transport pathway that runs through the electrode. Subsequently, high-temperature sintering in an inert atmosphere removes the organic components (including the first polymer and the first solvent), resulting in a three-dimensional porous ultrathin silicon anode precursor with an open pore structure (i.e., the silicon-based material and conductive additives are further combined and densified in the fiber structure, ultimately obtaining an ultrathin silicon anode precursor with a three-dimensional porous framework structure (i.e., a silicon anode precursor)). This porous framework provides a buffer space for the volume expansion of silicon while maintaining the continuity of the electronic conductivity network.

[0023] Further, a sulfide solid electrolyte and a second polymer are compounded in a second solvent to prepare an electrolyte composite slurry. This slurry is then coated onto the surface of the aforementioned ultrathin silicon anode precursor. The slurry's spontaneous penetration and capillary action fill the pores, forming a continuous ion transport channel at the interface between the silicon-based material and the conductive network. After vacuum drying, a dense, uniformly distributed, integrated ultrathin silicon anode (hereinafter referred to as "silicon anode") is obtained. This method achieves parallel, efficient ion / electron transport paths by constructing a tightly contacted three-phase composite structure of "ions-electrons-active material" in situ within a three-dimensional porous framework, significantly reducing charge transfer impedance. Simultaneously, the mechanical buffering of the porous framework and the interfacial adaptability of the sulfide electrolyte synergistically suppress the volume expansion of the silicon material, thereby simultaneously improving the electrode's cycle stability, active material utilization, and reaction kinetics. Furthermore, the entire process route has good compatibility with existing lithium-ion battery electrode manufacturing processes and has the potential for large-scale application.

[0024] In some embodiments, in step 1), based on the total mass of the silicon-based material, conductive additive, and first polymer being 100%, the mass percentage of the silicon-based material is 60% to 80%, preferably 70% to 80%. A high proportion of silicon-based material ensures that the electrode has sufficient capacity contribution. Exemplarily, the mass percentage of the silicon-based material is 60%, 65%, 70%, 75%, 80%, and any value between adjacent values.

[0025] In step 1), based on the total mass of silicon-based material, conductive additive, and first polymer being 100%, the mass percentage of conductive additive is 10% to 20%, preferably 10% to 15%. Selecting this mass percentage of conductive additive allows for the formation of a continuous conductive network while avoiding excessive addition that could decrease the proportion of active material. For example, the mass percentage of conductive additive can be 10%, 12.5%, 15%, 17.5%, 20%, or any value between two adjacent values.

[0026] In step 1), based on the total mass of silicon-based material, conductive additive, and first polymer being 100%, the mass percentage of the first polymer is 10% to 20%, preferably 10% to 15%. Selecting this mass percentage of the first polymer ensures the spinnability of the solution and the fiber forming strength; too low a percentage will lead to spinning difficulties, while too high a percentage will reduce the content of the effective components in the electrode. For example, the mass percentage of the first polymer is 10%, 12.5%, 15%, 17.5%, 20%, and any value between two adjacent values.

[0027] In some embodiments, in step 1), the solid content of the electrospinning precursor solution is 10% to 30%, preferably 10% to 20%. This range balances solution viscosity and spinnability; if the solid content is too low, the fiber forming strength will be insufficient, and if it is too high, the solution viscosity will be too high, affecting jet stretching and fiber morphology. Exemplarily, the solid content of the electrospinning precursor solution is 10%, 15%, 20%, 25%, 30%, and any value between adjacent values.

[0028] In some embodiments, in step 1), the electrospinning process voltage is 20 kV, the flow rate is 2 mL / h, and the receiving distance is 10 cm. The 20 kV high voltage provides sufficient electric field force to promote stable stretching and refinement of the jet, resulting in nanofibers with uniform diameter and regular morphology; the low spinning speed of 2 mL / h facilitates the full evaporation of solvent, avoids fiber adhesion, and improves the controllability of the pore structure of the fiber membrane; the 10 cm receiving distance can maintain the stability of the spinning process while the jet is fully solidified, ensuring that the fibers are uniformly deposited on the copper foil surface to form a film.

[0029] In some embodiments, in step 1), the sintering temperature is 500°C. o C~700 o C, preferably 600 o C~650 o C. This temperature range allows for the complete decomposition of the first polymer and the first solvent, while preventing significant grain growth or agglomeration of silicon particles. This helps maintain the high specific surface area and structural stability of the active material, optimizing the interfacial bonding between the conductive network and the silicon-based material while ensuring complete removal of organic matter. For example, the sintering temperature is 500°C. o C. 550℃, 600℃, 650℃, 700 o C and any value between the two adjacent values.

[0030] In some embodiments, in step 1), the sintering time is 1 h to 5 h, preferably 2 h to 3 h. This time range, within the preferred temperature, ensures complete polymer pyrolysis and allows the conductive additive and silicon-based material to form a stable composite structure at high temperatures. Too short a time may result in residual organic matter, affecting electrode conductivity and electrochemical stability. Too long a time may lead to energy waste and unnecessary crystallization or sintering of the material.

[0031] In some embodiments, in step 1), the porosity of the ultrathin silicon anode precursor is 60% to 80%, preferably 60% to 70%. This porosity provides continuous electrolyte permeation channels, while reserving buffer space for silicon volume expansion and maintaining the integrity of the three-dimensional conductive network and electronic conduction stability, thereby achieving synergistic optimization among ion transport, volume expansion buffering, and electronic conduction.

[0032] In some embodiments, in step 1), the thickness of the fiber film of the ultrathin silicon anode precursor (i.e., the thickness of the fiber film formed on the surface of the receiving substrate) is 5~10 μm.

[0033] In some embodiments, in step 2), based on the total mass of the sulfide solid electrolyte and the second polymer being 100%, the mass percentage of the sulfide solid electrolyte is 70% to 90%, preferably 80% to 90%. A high percentage of sulfide solid electrolyte ensures the continuity of ionic conductivity and ion transport pathways in the electrode. Exemplarily, the mass percentage of the sulfide solid electrolyte is 70%, 75%, 80%, 85%, 90%, or any value between adjacent values.

[0034] In some embodiments, in step 2), based on the total mass of the sulfide solid electrolyte and the second polymer being 100%, the mass percentage of the second polymer is 10% to 30%, preferably 10% to 20%; an appropriate amount of the second polymer serves as a binder and film-forming component, improving the stability of the slurry coating and the mechanical strength of the electrolyte layer. Exemplarily, the mass percentage of the second polymer is 10%, 15%, 20%, 25%, 30%, or any value between adjacent values.

[0035] In some embodiments, in step 2), the solid content of the electrolyte composite slurry is 10% to 30%, preferably 10% to 20%. Selecting this range balances slurry flowability and coating uniformity, ensuring that the slurry can fully penetrate the pores of the ultrathin silicon anode precursor to form a dense and continuous electrolyte layer. Exemplarily, the solid content of the electrolyte composite slurry is 10%, 15%, 20%, 25%, 30%, and any value between adjacent values.

[0036] In some embodiments, in step 2), the temperature for vacuum drying is 80°C. o C~100 o C, preferably 80 o C~90 o C. This temperature range can effectively promote the volatilization of the second solvent in a vacuum environment, while avoiding the decomposition or interfacial side reactions of the sulfide solid electrolyte due to excessive temperature, which is beneficial to maintaining the integrity of the electrolyte structure and its ion transport performance.

[0037] In some embodiments, in step 2), the vacuum drying time is 8 h to 12 h, preferably 10 h to 12 h. Sufficient time ensures that the second solvent is completely removed from the internal pores of the electrode, avoiding residual solvent from causing side reactions or reducing interface stability during battery cycling, while ensuring that the silicon anode electrode structure is dense and the components are evenly distributed.

[0038] In some embodiments, in step 2), the thickness of the ultrathin silicon anode (including the thickness of the receiving substrate and the material thickness of the surface of the receiving substrate) is 20~35 μm.

[0039] In some embodiments, in step 1), the silicon-based material includes, but is not limited to, at least one of nano-Si particles, micron-sized Si particles, Si nanowires, Si nanotubes, nanoporous Si, micron-sized porous Si, Si nanofilms, SiOx, Si / C, Si alloys, Si-metal oxide composites, pre-lithiated Si-based materials, Si-graphite composite particles, and Si-based core-shell structures. Exemplarily, the nano-Si particles have a particle size of 50-500 nm, and the micron-sized Si particles have a particle size of 1-5 μm.

[0040] Conductive additives include, but are not limited to, at least one of conductive carbon black (Super P), acetylene black, Ketjen black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, graphene, carbon nanofibers, carbonized polymer-derived carbon, and MXene materials.

[0041] The first polymer includes, but is not limited to, at least one of polyether, polyester, and polyolefin.

[0042] Polyethers include, but are not limited to, at least one of polyethylene oxide, polyethylene glycol, polypropylene oxide, polytetrahydrofuran, and ethylene oxide-propylene oxide copolymers.

[0043] Polyesters include, but are not limited to, at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polymethyl methacrylate, polyethylene glycol methyl ether methacrylate, polycarbonate, polypropylene carbonate, polypropylene carbonate, polycaprolactone, polylactic acid, polyethylene terephthalate, and polybutylene succinate.

[0044] Polyolefins include, but are not limited to, at least one of polyvinylidene fluoride, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyacrylonitrile, polytetrafluoroethylene, polybutene, polyisobutylene, ethylene-propylene copolymer, polyvinylidene fluoride-hexafluoropropylene, and polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.

[0045] The first solvent includes, but is not limited to, at least one of dimethylformamide, dimethylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, diethyl carbonate, dimethyl carbonate, and ethylene carbonate.

[0046] In some embodiments, in step 2), the sulfide solid electrolyte includes, but is not limited to, Li3PS4 and Li7P3S. 11 Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 5.8 PS 4.8Cl 1.2 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li6PS5Br, Li6PS5I, Li7P2S8I, Li 10 SnP2S 12 Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 At least one of S4 and 70Li2S·30P2S5.

[0047] The second polymer includes, but is not limited to, at least one of nitrile rubber, hydrogenated nitrile rubber, polybutadiene, polyisoprene, polystyrene, polyisobutylene, polyethylene, polypropylene, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer, styrene-ethylene-styrene block copolymer, styrene-butene-styrene block copolymer, and polydimethylsiloxane.

[0048] The second solvent includes, but is not limited to, at least one of butyl butyrate, toluene, xylene, ethylbenzene, mesitylene, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, and decahydronaphthalene.

[0049] Secondly, this application proposes an ultrathin silicon anode for sulfide solid-state batteries, comprising a silicon-based material, a conductive additive, and a sulfide solid electrolyte. The silicon-based material serves as the active component, providing capacity; it forms a three-dimensional continuous conductive network with the conductive additive through electrospinning. The conductive additive coats and connects the silicon-based particles, constructing electron transport channels. The sulfide solid electrolyte fills the pores and interfaces of the three-dimensional porous framework structure composed of the conductive network and silicon-based particles, forming a continuous ion conduction path. This structure achieves in-situ construction and uniform distribution of the "ion-electron-active material" three-phase interface, establishing parallel, highly efficient ion / electron transport paths, significantly reducing charge transfer impedance, and improving reaction kinetics and active material utilization. Simultaneously, this three-dimensional porous framework structure provides a buffer space for the volume expansion of silicon during cycling, and the mechanical flexibility of the sulfide solid electrolyte and the constraint effect of the conductive network synergistically suppress structural damage caused by volume changes, thereby effectively maintaining the integrity of the silicon anode electrode and significantly improving cycle stability. Furthermore, this silicon anode structure design is compatible with existing electrode processes and has good prospects for large-scale application.

[0050] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0051] Example 1 The preparation process of the ultrathin silicon anode in Example 1 is as follows: Step (1): Nano-Si particles, vapor-grown carbon fibers, and polyvinylidene fluoride (PVDF) were dissolved in dimethylpyrrolidone (DMF) to obtain an electrospinning precursor solution. Based on a total mass of 100% for the nano-Si particles (100 nm), vapor-grown carbon fibers, and PVDF, the nano-Si particles accounted for 75% of the mass, the vapor-grown carbon fibers for 12.5%, and the PVDF for 12.5%. The solid content of the electrospinning precursor solution was 15%. Using copper foil as the receiving substrate, the electrospinning precursor solution was electrospinned to form a three-dimensional network fiber film on a single side of the copper foil. The copper foil thickness was 10 μm. The electrospinning voltage was 20 kV, the flow rate was 2 mL / h, and the receiving distance was 10 cm. Then, high-temperature sintering was performed under an inert atmosphere to completely remove PVDF and DMF, ultimately obtaining an ultrathin silicon anode precursor; the high-temperature sintering temperature was 620 °C. o C, the high-temperature sintering time is 2.5h. The porosity of the ultrathin silicon anode precursor is 65%, and the thickness of the fiber film of the ultrathin silicon anode precursor is 7μm.

[0052] Step (2): Li6PS5Cl and hydrogenated nitrile butadiene rubber are dissolved in xylene to prepare an electrolyte composite slurry. Based on a total mass of 100% for Li6PS5Cl and hydrogenated nitrile butadiene rubber, Li6PS5Cl accounts for 85% of the mass, and hydrogenated nitrile butadiene rubber accounts for 15%. The solid content of the electrolyte composite slurry is 15%. The electrolyte composite slurry is uniformly coated onto the surface of the fiber membrane of the ultrathin silicon anode precursor, fully filling its internal pores; subsequently, it is vacuum dried to obtain the ultrathin silicon anode. The vacuum drying temperature is 85°C. o C, the vacuum drying time is 10 h, and the thickness of the ultrathin silicon anode is 25 μm.

[0053] Example 2 The difference between the preparation process of the ultrathin silicon anode in Example 2 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 2, based on the total mass of nano-Si particles, vapor-grown carbon fibers and polyvinylidene fluoride being 100%, the mass ratio of the nano-Si particles is 70%.

[0054] Example 3 The difference between the preparation process of the ultrathin silicon anode in Example 3 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 3, based on the total mass of nano-Si particles, vapor-grown carbon fibers and polyvinylidene fluoride being 100%, the mass ratio of nano-Si particles is 80%.

[0055] Example 4 The difference between the preparation process of the ultrathin silicon anode in Example 4 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 4, based on the total mass of the nano-Si particles, vapor-grown carbon fibers and polyvinylidene fluoride being 100%, the mass ratio of vapor-grown carbon fibers is 10%.

[0056] Example 5 The difference between the preparation process of the ultrathin silicon anode in Example 5 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 5, based on the total mass of nano-Si particles, vapor-grown carbon fibers and polyvinylidene fluoride being 100%, the mass percentage of vapor-grown carbon fibers is 15%.

[0057] Example 6 The difference between the preparation process of the ultrathin silicon anode in Example 6 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 6, by controlling the solid content of the electrospinning precursor solution to 10%, an ultrathin silicon anode precursor with a porosity of 60% is obtained, and the fiber film thickness of the ultrathin silicon anode precursor is 5μm.

[0058] Example 7 The difference between the preparation process of the ultrathin silicon anode in Example 7 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 7, by controlling the solid content of the electrospinning precursor solution to 20%, an ultrathin silicon anode precursor with a porosity of 70% is obtained, and the fiber film thickness of the ultrathin silicon anode precursor is 10 μm.

[0059] Example 8 The difference between the preparation process of the ultrathin silicon anode in Example 8 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (2) of Example 8, based on the total mass of Li6PS5Cl and hydrogenated nitrile rubber being 100%, the mass percentage of Li6PS5Cl is 80%.

[0060] Example 9 The difference between the preparation process of the ultrathin silicon anode in Example 9 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (2) of Example 9, based on the total mass of Li6PS5Cl and hydrogenated nitrile rubber being 100%, the mass percentage of Li6PS5Cl is 90%.

[0061] Example 10 The difference between the preparation process of the ultrathin silicon anode in Example 10 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (2) of Example 10, an ultrathin silicon anode with a thickness of 20 μm is obtained by controlling the solid content of the electrolyte composite slurry to 10%.

[0062] Example 11 The difference between the preparation process of the ultrathin silicon anode in Example 11 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (2) of Example 11, an ultrathin silicon anode with a thickness of 30 μm is obtained by controlling the solid content of the electrolyte composite slurry to 20%.

[0063] Example 12 The difference between the preparation process of the ultrathin silicon anode in Example 12 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 12, the silicon-based material is replaced with micron-sized Si particles (particle size of 2 μm).

[0064] Example 13 The difference between the preparation process of the ultrathin silicon anode in Example 13 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (1) of Example 13, the conductive additive is replaced with carbon nanotubes.

[0065] Example 14 The difference between the preparation process of the ultrathin silicon anode in Example 14 and the preparation process of the ultrathin silicon anode in Example 1 is as follows: In step (2) of Example 14, the sulfide solid electrolyte is replaced with Li 10 GeP2S 12 .

[0066] Comparative Example 1 The fabrication process of the ultrathin silicon anode in Comparative Example 1 is as follows: Nano-sized Si particles, vapor-grown carbon fibers, Li6PS5Cl, and hydrogenated nitrile butadiene rubber were dissolved in xylene to obtain an electrode coating slurry. Based on a total mass of 100% for the nano-sized Si particles, vapor-grown carbon fibers, Li6PS5Cl, and hydrogenated nitrile butadiene rubber, the nano-sized Si particles accounted for 40% of the mass, the vapor-grown carbon fibers for 6.7%, the Li6PS5Cl for 45.3%, and the hydrogenated nitrile butadiene rubber for 8%. The solid content of the electrode coating slurry was 15%. The electrode coating slurry was uniformly coated onto the surface of a copper foil, and then vacuum dried to obtain an ultrathin silicon anode. The thickness of the copper foil was 10 μm. The vacuum drying temperature was 85°C. oC, vacuum drying time is 10 h. The thickness of this ultrathin silicon anode is 30 μm.

[0067] Comparative Example 2 The preparation process of the ultrathin silicon anode in Comparative Example 2 is as follows: Nano-sized Si particles, vapor-grown carbon fibers, and polyvinylidene fluoride (PVDF) were dissolved in dimethylpyrrolidone to obtain a conventional electrode coating slurry. Based on a total mass of 100% for the nano-sized Si particles, vapor-grown carbon fibers, and PVDF, the nano-sized Si particles accounted for 75% of the mass, the vapor-grown carbon fibers for 12.5%, and the PVDF for 12.5%. The solid content of the conventional electrode coating slurry was 15%. This conventional electrode coating slurry was uniformly coated onto the surface of a copper foil, and then vacuum dried to obtain an ultrathin silicon anode. The copper foil thickness was 10 μm. The vacuum drying temperature was 85°C. o C, vacuum drying time is 10 h. The thickness of the ultrathin silicon anode is 30 μm.

[0068] Performance test To verify the performance of the ultrathin silicon anode provided in this application, further tests were conducted on the performance of the ultrathin silicon anodes prepared in each embodiment and comparative example. Details are as follows: (1) Electrode conductivity test Stainless steel | Ultra-thin silicon anode | Stainless steel, lithium metal | Li6PS5Cl | Ultra-thin silicon anode | Li6PS5Cl | Lithium metal symmetric cells were used for DC polarization testing under applied voltages of 0.5V and 5mV, respectively. The formula for calculating conductivity (σ) is as follows:

[0069] Where I is the steady-state current, L is the thickness of the ultrathin silicon anode, U is the applied voltage, and S is the cross-sectional area of ​​the ultrathin silicon anode.

[0070] (2) Electrode expansion rate test 1) Solid-state battery assembly: The battery is assembled in an argon-protected glove box with ultra-thin silicon anode as the working electrode and lithium metal as the counter electrode.

[0071] 2) Solid-state battery cycling and disassembly: The solid-state battery was tested using the Blue Electric testing system, with a voltage range of 0V-1.5V and charge / discharge conditions of 0.1C cycling at room temperature. The solid-state battery was disassembled, the ultra-thin silicon anode was removed, cleaned, and dried.

[0072] 3) Expansion rate calculation: The thickness of the ultrathin silicon anode was recorded using a high-precision micrometer after the initial discharge, the first discharge (lithiation of silicon-based materials), and the 10th discharge.

[0073]

[0074] Where T0 is the initial average thickness, T n The average thickness after the nth discharge (n=1, 10).

[0075] (3) Cyclic performance test 1) Solid-state battery assembly: Solid-state batteries are assembled in an argon-protected glove box with ultra-thin silicon anode as the working electrode and lithium metal as the counter electrode.

[0076] 2) The solid-state battery was tested using the Blue Electric test system. The voltage range was 0 V to 1.5 V, and the charge and discharge conditions were room temperature and 0.1C cycling. After 100 cycles, the corresponding capacity retention rate was calculated.

[0077] The performance test results of the ultrathin silicon anodes in the examples and comparative examples are shown in Table 1.

[0078] Table 1 Performance test results of the ultrathin silicon anodes in the examples and comparative examples

[0079] As shown in Table 1, Example 1, through the stable conductive framework constructed by electrospinning and the dense ion channels formed by the in-situ penetration of sulfide electrolyte, achieved excellent synergy between ionic conductivity of 0.32 mS / cm and electronic conductivity of 8.5 mS / cm. This resulted in a 95.8% cycle capacity retention rate even at a 135% initial discharge expansion rate, demonstrating optimal overall performance. Any deviation of a key component from its optimal window would lead to performance degradation. Excessive silicon content would exacerbate volume expansion and compress ion transport paths, while insufficient content would weaken capacity and electron network connectivity. Insufficient conductive additive content would limit electron conduction, while excessive content would encroach on the pores required for ion transport. A reduced proportion of sulfide solid electrolyte would directly cause a 44% decrease in ionic conductivity, while an excessively high proportion might affect interfacial bonding strength. Process parameters also influence electrode performance by affecting the microstructure. Too low a solid content in the electrospinning precursor solution results in a loose fiber membrane structure and poor mechanical strength, while too high a content easily leads to closed pores hindering electrolyte permeation. Similarly, too low a solid content in the electrolyte composite slurry may result in incomplete pore filling, while too high a content easily forms a dense layer on the surface, affecting internal wetting. Comparison with traditional processes further highlights the advantages of this application. Comparative Example 1, using a conventional blending coating process, exhibits ionic and electronic conductivity of only 0.08 mS / cm and 1.2 mS / cm, respectively, with a capacity retention rate as low as 62%, indicating that disordered mixed structures cannot establish efficient dual-continuous transport channels. Comparative Example 2, completely free of sulfide solid electrolytes, has near-zero ionic conductivity and rapidly pulverizes the electrode structure, confirming that sulfide solid electrolytes simultaneously play an irreplaceable dual role in ion conduction and mechanical constraint in this system.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0081] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this disclosure can be achieved, and this is not limited herein.

[0082] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0083] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for preparing a silicon anode, characterized in that, The preparation method includes: A silicon-based material, conductive additive, first polymer, and first solvent are uniformly mixed to obtain an electrospinning precursor solution; using a negative electrode current collector as a receiving substrate, the electrospinning precursor solution is electrospinned to form a fiber film on one side of the receiving substrate; then, it is sintered in an inert atmosphere to obtain a silicon negative electrode precursor. A sulfide solid electrolyte, a second polymer, and a second solvent are uniformly mixed to obtain an electrolyte composite slurry. The electrolyte composite slurry is uniformly coated onto the surface of the fiber membrane of the silicon anode precursor and then vacuum dried to obtain the silicon anode. Wherein, based on the total mass of the silicon-based material, conductive additive, and first polymer as 100%, the mass percentage of the silicon-based material is 60%~80%, the mass percentage of the conductive additive is 10%~20%, and the mass percentage of the first polymer is 10%~20%; the solid content of the electrospinning precursor solution is 10%~30%. Based on the total mass of the sulfide solid electrolyte and the second polymer as 100%, the mass percentage of the sulfide solid electrolyte is 70% to 90%, and the mass percentage of the second polymer is 10% to 30%; the solid content of the electrolyte composite slurry is 10% to 30%.

2. The preparation method according to claim 1, characterized in that, Based on the total mass of the silicon-based material, conductive additive, and first polymer being 100%, the silicon-based material accounts for 70% to 80% of the mass, the conductive additive accounts for 10% to 15% of the mass, and the first polymer accounts for 10% to 15% of the mass. The solid content of the electrospinning precursor solution is 10%~20%.

3. The preparation method according to claim 1, characterized in that, With the total mass of the sulfide solid electrolyte and the second polymer being 100%, the mass percentage of the sulfide solid electrolyte is 80% to 90%, and the mass percentage of the second polymer is 10% to 20%. The solid content of the electrolyte composite slurry is 10%~20%.

4. The preparation method according to claim 1, characterized in that, The porosity of the silicon anode precursor is 60%~80%.

5. The preparation method according to claim 1, characterized in that, The thickness of the fiber film of the silicon anode precursor is 5~10μm; the thickness of the silicon anode is 20~35μm.

6. The preparation method according to claim 1, characterized in that, The electrospinning requires a voltage of 20 kV, a flow rate of 2 mL / h, and a receiving distance of 10 cm.

7. The preparation method according to claim 1, characterized in that, The sintering temperature is 500℃~700℃, and the sintering time is 1h~5h; The vacuum drying temperature is 80℃~100℃, and the vacuum drying time is 8h~12h.

8. The preparation method according to any one of claims 1-7, characterized in that, The silicon-based material is at least one of the following: nano-Si particles, micron-sized Si particles, Si nanowires, Si nanotubes, nanoporous Si, micron-sized porous Si, Si nanofilms, SiOx, Si / C, Si alloys, Si-metal oxide composite materials, pre-lithiated Si-based materials, Si-graphite composite particles, and Si-based core-shell structures. The conductive additive is at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, vapor-grown carbon fiber, carbon nanotubes, graphene, carbon nanofibers, carbonized polymer-derived carbon, and MXene materials. The first polymer is at least one of polyether, polyester and polyolefin; The first solvent is at least one of dimethylformamide, dimethylpyrrolidone, dimethyl sulfoxide, dimethylacetamide, diethyl carbonate, dimethyl carbonate, and ethylene carbonate; The sulfide solid electrolyte is Li3PS4 or Li7P3S. 11 Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 Li 5.8 PS 4.8 Cl 1.2 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li6PS5Br, Li6PS5I, Li7P2S8I, Li 10 SnP2S 12 Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 At least one of S4 and 70Li2S·30P2S5; The second polymer is at least one of nitrile rubber, hydrogenated nitrile rubber, polybutadiene, polyisoprene, polystyrene, polyisobutylene, polyethylene, polypropylene, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer, styrene-ethylene-styrene block copolymer, styrene-butene-styrene block copolymer, and polydimethylsiloxane; The second solvent is at least one selected from butyl butyrate, toluene, xylene, ethylbenzene, mesitylene, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, and decahydronaphthalene.

9. A silicon anode, characterized in that, The silicon anode is prepared by the preparation method according to any one of claims 1-8.

10. A sulfide solid-state battery, characterized in that, The silicon anode prepared by the preparation method according to any one of claims 1-8, or the silicon anode according to claim 9.

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