Silicon-based composite anode materials and their preparation methods, sulfide solid-state batteries

Abstract

This invention provides a silicon-based composite anode material and its preparation method, as well as a sulfide solid-state battery. The preparation method includes: depositing a silicon source and a carbon source onto at least one surface of a flexible carbon substrate via chemical vapor deposition to obtain a first product; placing the first product in a solution containing a phosphorus source and subjecting it to a wetting treatment to obtain a second product; subjecting the lithium source, sulfur source, and the second product to heat treatment to obtain a third product; and obtaining the silicon-based composite anode material via atomic layer deposition. This invention achieves the technical effects of improving ion transport efficiency, constraining volumetric strain, suppressing interfacial side reactions, and enhancing electrode-electrolyte interface stability through chemical vapor deposition to construct a silicon-carbon composite layer, phosphorus source wetting treatment to introduce nitrogen-phosphorus precursors, in-situ formation of a Li-P-S composite layer via a vapor-phase thermal reaction of the lithium and sulfur sources, and precise construction of a metal-oxide interface layer via atomic layer deposition.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, and more specifically, to a silicon-based composite anode material and its preparation method, and a sulfide solid-state battery. Background Technology

[0002] Sulfide-based all-solid-state batteries are considered key to next-generation energy storage technology due to their high safety and high energy density. Silicon-based anodes have a theoretical capacity of 4200 mAh / g. -1 Silicon is one of the ideal anode materials. However, combining silicon-based anodes with sulfide electrolytes faces three major challenges: (1) silicon has low intrinsic ionic conductivity and slow lithium-ion transport kinetics; (2) silicon undergoes huge volume expansion (>300%) during lithium intercalation, leading to electrode structure damage and interface contact failure; (3) silicon has poor chemical compatibility with sulfide electrolytes and is prone to side reactions that generate a high impedance layer.

[0003] To alleviate the aforementioned problems, researchers have proposed various optimization strategies. For example, CN120727780A discloses a composite anode material in which a Li3PO4 fast ion conductor layer is constructed on the surface of nitrogen-doped carbon-coated silicon nanosheets. While this approach can improve ion conduction to some extent, its effect on suppressing volume expansion and improving interface stability is limited. CN120878830A proposes coating a silicon-based material with a fluorinated carbon layer containing Li-M alloy / LiF / LiX. However, the bonding strength between this coating layer and the silicon substrate, as well as its structural integrity during long-term cycling, still need to be verified. In addition, Honda Motor Co., Ltd. (CN120727767A) discloses the introduction of a specific number of ionic liquids as donors into a composite material containing a silicon-based anode and a sulfide solid electrolyte to stabilize the interface. This method involves liquid components, and its long-term stability at high temperatures and its potential impact on the solid electrolyte still require attention.

[0004] Therefore, the technical problem to be solved in this field is how to provide a silicon-based anode material that is suitable for sulfide all-solid-state batteries, has high ion transport efficiency, can effectively alleviate the volume expansion effect of silicon materials, and significantly suppresses interfacial side reactions, and precisely constructs a stable multifunctional interface layer at the molecular / atomic level, while solving the three major problems of ion conduction, volume expansion and interfacial side reactions, so as to achieve a synergistic improvement in the high initial coulombic efficiency, excellent cycle stability and excellent rate performance of the battery. Summary of the Invention

[0005] The main objective of this invention is to provide a silicon-based composite anode material and its preparation method, as well as a sulfide solid-state battery, to solve the problems of low ion transport efficiency, significant volume expansion effect of silicon materials, and severe interfacial side reactions in existing silicon-based anode materials.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a silicon-based composite anode material, comprising: step S1, providing a flexible carbon substrate having two opposing surfaces; step S2, depositing a silicon source and a carbon source on at least one surface of the flexible carbon substrate by chemical vapor deposition, and forming a silicon-carbon composite layer on the surface to obtain a first product; step S3, placing the first product in a solution containing a phosphorus source and subjecting it to wetting treatment to obtain a second product; step S4, subjecting a lithium source, a sulfur source, and the second product to heat treatment, so that the lithium source and the sulfur source react and deposit in gaseous form on the surface of the second product, and forming a Li-PS composite layer on the surface of the silicon-carbon composite layer to obtain a third product; and step S5, forming a metal oxide layer on the surface of the Li-PS composite layer by atomic layer deposition to obtain the silicon-based composite anode material.

[0007] Further, the thickness of the flexible carbon substrate is 80μm~120μm; and / or, the flexible carbon substrate is selected from one or more of flexible carbon nonwoven fabric, flexible carbon paper and graphene flexible film; preferably, the flexible carbon substrate is flexible carbon nonwoven fabric, and the fiber diameter in the flexible carbon nonwoven fabric is 5μm~10μm.

[0008] Further, in step S2, the flow rate ratio of silicon source to carbon source is (4~6):1; and / or, the silicon source is silane; and / or, the carbon source is acrylonitrile and / or acetylene; preferably, the flow rate of silicon source is 50±5 sccm, and / or, the flow rate of carbon source is 10±2 sccm.

[0009] Further, in step S2, the chemical vapor deposition is performed at 500°C to 700°C for 0.5 h to 1.5 h; and / or, the chemical vapor deposition uses argon as a carrier; and / or, the chemical vapor deposition is performed in a protective atmosphere; preferably, the protective atmosphere is nitrogen and / or argon.

[0010] Further, in step S3, the phosphorus source in the solution contains a phosphorus source with a mass concentration of 0.2% to 1.0%; and / or, the phosphorus source is selected from one or more of a mixture of triethyl phosphate and dicyandiamide, hexachlorocyclotriphosphazene, and octachlorocyclotetraphosphazene; and / or, the immersion treatment is carried out at 20°C to 50°C for 5 to 20 seconds; preferably, the solution containing the phosphorus source uses one or more of acetonitrile, tetrahydrofuran, dichloromethane, and ethyl acetate as a solvent.

[0011] Further, in step S4, the molar ratio of lithium source to sulfur source is 1:(2~4); and / or, the lithium source is selected from one or more of Li2S, LiH and LiN3; and / or, the sulfur source is sulfur powder and / or thiourea; preferably, the lithium source is Li2S and the sulfur source is sulfur powder.

[0012] Further, step S4 includes: placing the lithium source, sulfur source and the second product in a reaction vessel with a volume of 1L to 5L, and performing heat treatment at a temperature of 250℃ to 400℃ to sublimate the lithium source and sulfur source into a gaseous form, and performing a contact reaction and deposition on the surface of the silicon-carbon composite layer for a time of 2h to 8h to obtain the third product.

[0013] Further, in step S5, the deposition temperature of atomic layer deposition is 120℃~180℃, and the number of cycles is 10~200; and / or, the metal oxide in the metal oxide layer is selected from one or more of Al2O3, SnO2 and TiO2; and / or, the thickness of the metal oxide layer is 0.5nm~5nm; preferably, step S5 includes: by atomic layer deposition, setting the deposition temperature to 150±10℃ and the number of cycles to 5~50, using trimethylaluminum and water as precursors, forming an Al2O3 layer on the surface of the Li-PS composite layer to obtain a silicon-based composite anode material.

[0014] A second aspect of the present invention provides a silicon-based composite anode material, which is prepared by the above-described method for preparing silicon-based composite anode materials.

[0015] A third aspect of the present invention provides a sulfide solid-state battery, including a negative electrode sheet, the negative electrode sheet being the aforementioned silicon-based composite negative electrode material.

[0016] By applying the technical solution of this invention, based on a flexible carbon matrix as a three-dimensional conductive framework, and through chemical vapor deposition to construct a silicon-carbon composite layer, phosphorus source wetting treatment to introduce nitrogen and phosphorus precursors, in-situ formation of a Li-PS composite layer by gas-phase thermal reaction of lithium and sulfur sources, and precise construction of a metal oxide interface layer by atomic layer deposition, the aim of constructing a multi-level synergistic functional coating structure on the surface of silicon-based active materials is achieved. This results in improving ion transport efficiency, constraining volumetric strain, suppressing interfacial side reactions, and enhancing the stability of the electrode-electrolyte interface. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As described in the background art, existing silicon-based anode materials suffer from low ion transport efficiency, significant silicon material volume expansion effect, and severe interfacial side reactions, making it difficult for the resulting battery to simultaneously achieve high initial coulombic efficiency, excellent cycle stability, and superior rate capability. To address these technical problems, the first aspect of this invention provides a method for preparing a silicon-based composite anode material, comprising: step S1, providing a flexible carbon substrate having two opposing surfaces; step S2, depositing a silicon source and a carbon source on at least one surface of the flexible carbon substrate by chemical vapor deposition, forming a silicon-carbon composite layer on the surface, thereby obtaining a first product; step S3, placing the first product in a solution containing a phosphorus source and subjecting it to wetting treatment to obtain a second product; step S4, heat-treating a lithium source, a sulfur source, and the second product to allow the lithium source and sulfur source to react and deposit in gaseous form on the surface of the second product, forming a Li-PS composite layer on the surface of the silicon-carbon composite layer, thereby obtaining a third product; and step S5, forming a metal oxide layer on the surface of the Li-PS composite layer by atomic layer deposition, thereby obtaining the silicon-based composite anode material.

[0019] This invention employs a flexible carbon matrix as a three-dimensional conductive framework, and constructs a silicon-carbon composite layer in situ via chemical vapor deposition. A phosphorus source solution is used to introduce nitrogen and phosphorus precursors. A Li-PS composite layer is deposited in situ via a solid-gas phase thermal reaction, and a metal oxide interface layer is precisely constructed via atomic layer deposition. This achieves the goal of progressively constructing a functionalized multilayer interface structure on the surface of the silicon-carbon composite layer. Specifically, in the above preparation process:

[0020] Based on a flexible carbon matrix, the in-situ growth of silicon nanostructures and carbon coating are first integrated by co-depositing silicon and carbon sources on the surface. During this process, the silicon source pyrolyzes to form silicon nuclei, which then extend directionally along the fiber surface into nanowires or nanopillars. Simultaneously, the carbon source decomposes at high temperature to generate amorphous carbon, which coats the silicon surface, forming a "silicon core-carbon shell" heterostructure. This structure enhances the electrical contact between silicon and the conductive substrate without relying on binders, shortens the lithium-ion / electron transport path, and partially buffers the volume expansion stress of silicon through the mechanical flexibility of the carbon layer. The first product is then immersed in an organic solution containing a phosphorus source. Through physical adsorption and capillary action, phosphorus source molecules adhere to the surface of the silicon-carbon composite layer, providing a locally phosphorus-rich environment for subsequent heat treatment. In step S4, the second product is co-heat-treated with a solid lithium source and a sulfur source, causing lithium and sulfur to volatilize in the gas phase and diffuse to the surface of the second product, where they react with the adsorbed phosphorus source in a gas-solid reaction, generating an amorphous Li-PS fast ion conductor phase in situ. This layer only covers the silicon-carbon composite layer and does not penetrate into it, providing a highly conductive channel for lithium ions. Furthermore, due to its isotropic ion transport characteristics, the amorphous structure avoids grain boundary impedance. Finally, an ultrathin metal oxide is deposited on the surface of the Li-PS layer using ALD technology, further preventing direct contact between the sulfide electrolyte and the silicon-carbon composite layer and suppressing interfacial reduction reactions.

[0021] The above preparation method constructs a five-layer structure consisting of a flexible carbon matrix, a silicon-carbon composite layer, a phosphorus source adsorption layer, a Li-PS conductor layer, and an ALD metal oxide layer through the synergistic effect of five steps. This achieves the technical effects of improving ion transport efficiency, constraining volumetric strain, suppressing interfacial side reactions, and enhancing the stability of the electrode-electrolyte interface.

[0022] In summary, the preparation method provided by this invention has the following advantages:

[0023] Firstly, it addresses multiple issues synergistically: the three-dimensional flexible substrate buffers volume changes, the fast-ion Li-PS composite conductor layer enhances ion conductivity, and the metal oxide layer stabilizes the interface. These three elements work together to fundamentally improve the performance shortcomings of silicon-based anodes in sulfide all-solid-state batteries.

[0024] Secondly, excellent electrochemical performance: thanks to the above-mentioned careful design, the negative electrode exhibits high initial coulombic efficiency, excellent rate performance and ultra-long cycle life after being assembled into an all-solid-state battery.

[0025] Third, the preparation process is controllable: the CVD, in-situ reaction and ALD used in the preparation process are all mature and controllable processes, which are conducive to large-scale production and quality control.

[0026] Furthermore, to achieve synergistic optimization of the overall mechanical strength and flexibility of the electrode sheet, the thickness of the flexible carbon substrate is preferably 80μm~120μm, thereby more effectively realizing the long-cycle stability of the electrode structure. Specifically, the flexible carbon substrate can be selected from one or more of flexible carbon nonwoven fabric, flexible carbon paper, and graphene flexible film. Preferably, the flexible carbon substrate is flexible carbon nonwoven fabric, and the fiber diameter in this flexible carbon nonwoven fabric is 5μm~10μm. This fiber-scale formation of a highly porosity, well-connected flexible three-dimensional network structure not only promotes more complete penetration and uniform deposition of the gaseous precursor during CVD, but also allows the generated silicon-carbon composite layer to be more deeply embedded in the fiber gaps. Consequently, in application, the electrode can autonomously deform with changes in silicon volume during cycling without breaking, ultimately more effectively alleviating stress concentration and improving the cycle life of the battery.

[0027] In step S2, the preferred flow ratio of silicon source to carbon source is (4~6):1, which allows for more effective control of the growth rate of silicon nanowires and the density of carbon coating. This results in a silicon nanowire composite structure with higher density and more uniform carbon coating on the flexible carbon substrate, thereby more effectively constraining silicon expansion during battery operation. The resulting silicon-carbon composite layer contains carbon-coated silicon nanowires. The silicon nanowires grow along the carbon fiber axis, forming a one-dimensional conductive path. The carbon layer forms a seamless coating on the silicon surface, enhancing electrical contact and constraining the radial expansion of silicon during lithium intercalation through the flexible carbon network, preventing nanowire breakage or detachment from the substrate. Ultimately, this causes the silicon active material to be encapsulated and anchored to the flexible carbon substrate surface by the in-situ carbon layer, achieving the technical effects of improved electronic conductivity, buffering volume expansion, and preventing silicon particle detachment.

[0028] Furthermore, to ensure that the silicon precursor concentration in the reaction chamber is sufficient to support continuous nucleation and directional extension, and that the carbon precursor concentration promotes continuous carbon layer coating without becoming excessively thick, thus providing a smoother and more continuous morphological basis for the uniform coverage of the subsequent Li-PS layer, preferably, the silicon source flow rate is 50 ± 5 sccm, and / or the carbon source flow rate is 10 ± 2 sccm. In practical applications, the silicon source used is silane; and / or, the carbon source used can be acrylonitrile and / or acetylene.

[0029] In step S2, chemical vapor deposition is preferably performed at 500℃~700℃ for 0.5h~1.5h to promote complete pyrolysis of the silicon and carbon sources, forming highly active free radicals and promoting uniform nucleation of silicon nuclei on the carbon fiber surface. This results in the formation of a composite silicon nanowire structure with better crystallinity, more complete carbon coating, and stronger adhesion on the substrate surface, further optimizing the various properties of the obtained anode material. In this process, argon is preferably used as an inert carrier, as it does not react with the silicon and carbon precursors, thus more effectively maintaining the purity and electrochemical activity of the silicon nanowires. Furthermore, to more effectively prevent the carbon matrix from being oxidized and maintain its conductivity and structural integrity, chemical vapor deposition is more preferably performed in a protective atmosphere (specifically, nitrogen and / or argon).

[0030] Furthermore, in step S3, the solution containing a phosphorus source preferably has a mass concentration of 0.2% to 1.0%, thereby promoting more thorough adsorption of phosphorus onto the surface of the silicon-carbon layer, forming a monolayer or sub-monolayer coverage. This satisfies the requirement for reacting with gaseous lithium-sulfur to form a dense Li-PS layer during heat treatment, while also more effectively reducing and avoiding the formation of pores, further improving the density of the interface structure and ion transport efficiency, and enhancing the electrical performance of the resulting negative electrode. Specifically, the phosphorus source can be selected from one or more of a mixture of triethyl phosphate and dicyandiamide (where the weight ratio of triethyl phosphate to dicyandiamide is (5~7):1), hexachlorocyclotriphosphazene, and octachlorocyclotetraphosphazene. The P-Cl bond in the hexachlorocyclotriphosphazene molecule can undergo dechlorination and cyclization during subsequent heat treatment, generating a polymer intermediate with a PN backbone. This intermediate can react more efficiently with gaseous lithium and sulfur sources, generating an amorphous Li-PSNO fast ion conductor phase in situ. This significantly improves the structural disorder of the layer, enhances the hopping migration ability of lithium ions in the amorphous phase, and optimizes the electrical performance of the resulting negative electrode. In practical applications, the solution containing the phosphorus source uses one or more of acetonitrile, tetrahydrofuran, dichloromethane, and ethyl acetate as solvents.

[0031] To promote more uniform physical adsorption of phosphorus source on the surface of silicon-carbon composite layer without initiating chemical reactions, the wetting treatment is preferably carried out at 20℃~50℃ for 5s~20s. This more effectively controls solvent evaporation and molecular thermal motion, allowing the phosphorus-containing solution to more fully wet the capillary structure of the fiber surface, providing more uniform reaction sites for subsequent gas-phase thermal reactions, and ultimately preparing a silicon-based composite anode material with superior electrical performance.

[0032] In step S4, the preferred molar ratio of lithium source to sulfur source is 1:(2~4) to more precisely control the relative concentrations of Li and S in the gas phase, thereby more efficiently generating a high-ionic-conductivity Li-PS composite layer on the surface of the silicon-carbon composite layer and further improving the electrical performance of the obtained silicon-based composite anode material. Specifically, the lithium source can be selected from one or more of Li2S, LiH, and LiN3; and / or, the sulfur source can be sulfur powder and / or thiourea. In several typical embodiments, the lithium source is Li2S and the sulfur source is sulfur powder. Excess sulfur promotes the complete participation of Li2S in the reaction, reducing problems such as incomplete PS bond coordination, increased crystallinity of the conductor phase, or limited ion channels caused by insufficient sulfur. Meanwhile, Li2S, as a solid lithium source, undergoes synergistic sublimation with sulfur powder during heat treatment, forming a more stable gaseous mixture (Li2S (g) + S(g)) in the reaction zone. This mixture reacts with the adsorbed phosphorus source pyrolysis products at the gas-solid interface, generating amorphous phases such as Li3PS4 and Li3PS4-N, thus forming a denser, more continuous ionic conductor layer that significantly enhances the electrical performance of the electrode.

[0033] In several typical embodiments, step S4 includes: placing the lithium source, sulfur source, and second product in a reaction vessel with a volume of 1L to 5L, and subjecting them to heat treatment at a temperature of 250℃ to 400℃ to sublimate the lithium source and sulfur source into a gaseous state, followed by a contact reaction and deposition on the surface of the silicon-carbon composite layer for 2h to 8h to obtain the third product. The above-mentioned preferred conditions promote a more uniform gas phase distribution, optimize PS-Li bonding, and result in a more uniform thickness and higher density of the obtained composite conductor layer, thereby significantly improving the electrical performance and long-cycle capability of the obtained silicon-based composite anode material.

[0034] Furthermore, in step S5, the preferred atomic layer deposition temperature is 120℃~180℃, and the number of cycles is 10~200 times, to facilitate a more efficient self-limiting surface reaction between the precursor and co-reactants, further optimizing the film quality and improving the electrical performance of the resulting material. This results in a metal oxide layer with a thickness of 0.5nm~5nm, which more effectively achieves physical isolation between the silicon-carbon active layer and the sulfide electrolyte, while also better maintaining efficient lithium-ion conduction. Preferably, the metal oxide in the metal oxide layer is selected from one or more of Al2O3, SnO2, and TiO2, all of which possess excellent chemical stability, do not react with the sulfide electrolyte, and can effectively suppress interfacial reduction reactions, significantly improving the long-term cycling stability of the electrode.

[0035] Furthermore, in several typical embodiments, preferred step S5 includes: forming an Al2O3 layer on the surface of the Li-PS composite layer by atomic layer deposition at a deposition temperature of 150±10℃ and a cycle count of 5~50 times, using trimethylaluminum and water as precursors, to obtain a silicon-based composite anode material. Based on the above preferred conditions and parameters, an Al2O3 protective layer with a more suitable thickness, dense and pinhole-free structure, and higher chemical stability is formed on the surface of the Li-PS composite layer. Its high dielectric constant and strong Lewis acidity can passivate surface active sites and inhibit the reductive decomposition of sulfide electrolytes, thereby significantly reducing the increase in interfacial impedance of the obtained anode sheet after cycling.

[0036] A second aspect of this invention provides a silicon-based composite anode material, which is prepared by the aforementioned method for preparing silicon-based composite anode materials. The resulting silicon-based composite anode material comprises a five-layer structure: a flexible carbon matrix, a CVD silicon-carbon composite layer, a phosphorus source-wetting adsorption layer, a Li-PS fast ion conductor layer generated by a gas-phase thermal reaction, and an ALD metal oxide layer. It possesses high ionic conductivity, excellent volume adaptability, and strong interfacial stability. It should be noted that due to the complex structural formation and compositional changes during the preparation process, and the limitations of the specific characteristics of electrode materials and existing testing and characterization methods, a comprehensive quantitative characterization of the complex microstructure of the aforementioned silicon-based composite anode material is difficult. However, performance test results have already shown that the silicon-based composite anode material obtained by this invention possesses superior electrical performance, especially long-cycle stability.

[0037] A third aspect of the present invention provides a sulfide solid-state battery, including a negative electrode sheet, which is the aforementioned silicon-based composite negative electrode material. The negative electrode material provided by the present invention, with its multilayer structure, can effectively suppress electrode stripping caused by silicon volume expansion, while also significantly improving the lithium-ion cross-interface migration rate and suppressing the reduction side reaction between Si and sulfides. This achieves the technical effects of low interfacial impedance, high initial efficiency, and excellent capacity retention during battery cycling.

[0038] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0039] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0040] Example 1

[0041] A method for preparing a silicon-based composite anode material:

[0042] (1) Raw material description: flexible carbon nonwoven fabric (thickness 100μm, fiber diameter 5~10μm), silane (SiH4, purity 99.999%), acrylonitrile vapor (AN, purity 99.9%), hexachlorocyclotriphosphazene (HCCP, purity 98%), lithium sulfide (Li2S, purity 99.9%), sulfur powder (S, purity 99.5%), trimethylaluminum (TMA, purity 99%), deionized water.

[0043] (2) Preparation of SiNW@C / flexible carbon cloth: The carbon nonwoven fabric was placed in a tube furnace, and an Ar / H2 mixed gas was introduced, and the temperature was raised to 600℃. Using Ar as the carrier gas, silane (50 sccm) and acrylonitrile vapor (10 sccm) were introduced into the reaction chamber together (i.e., the flow ratio of silicon source to carbon source was 5:1), and maintained for 1 hour. After the reaction was completed, it was cooled to room temperature under an Ar atmosphere to obtain a flexible composite substrate (SiNW@C / flexible carbon cloth, denoted as the first product) with carbon-coated silicon nanowires grown on its surface.

[0044] (3) Prepare a 0.5 wt% HCCP acetonitrile solution. Immerse the SiNW@C / flexible carbon cloth obtained in step (2) in the above solution for 10 seconds at 25°C, then remove and air dry at room temperature. This is recorded as the second product.

[0045] (4) The dried material, along with Li2S and S powder (in a 1:3 molar ratio of lithium source to sulfur source), is placed in a 3L sealed reactor, ensuring no direct contact. The reactor is heated to 300°C and held at that temperature for 4 hours under an Ar atmosphere. After natural cooling, a material with a Li-PSNO layer (set on top of the silicon-carbon composite layer) is obtained (Li-PSNO@SiNW@C / flexible carbon cloth, denoted as the third product).

[0046] (5) Place the above materials in an atomic layer deposition apparatus, using TMA and deionized water as precursors, and deposit at a temperature of 150°C. Perform 20 deposition cycles to further form an Al2O3 thin film layer of about 2 nm thickness on the surface of the Li-PSNO layer, thus obtaining the final product (denoted as ALD-Al2O3@Li-PSNO@SiNW@C / flexible carbon cloth).

[0047] Example 2

[0048] A method for preparing a silicon-based composite anode material:

[0049] The only difference between this embodiment and Embodiment 1 is that the mass concentration of HCCP in the HCCP acetonitrile solution in step (3) is changed to 1.0 wt%; at the same time, the heat treatment temperature in step (4) is changed to 350°C.

[0050] Example 3

[0051] A method for preparing a silicon-based composite anode material:

[0052] The only difference between this embodiment and Embodiment 1 is that the number of cycles in step (5) is changed to 25 times, thereby obtaining an Al2O3 thin film layer with a thickness of about 2.5 nm.

[0053] Example 4

[0054] A method for preparing a silicon-based composite anode material:

[0055] The only difference between this embodiment and embodiment 1 is that in step (2), the flow rate of the silicon source is changed to 30 sccm, and the flow rate ratio of the silicon source to the carbon source is changed to 3:1.

[0056] Example 5

[0057] A method for preparing a silicon-based composite anode material:

[0058] The only difference between this embodiment and embodiment 1 is that in step (2), the flow rate of the carbon source is changed to 6.25 sccm, and the flow rate ratio of the silicon source to the carbon source is changed to 8:1.

[0059] Example 6

[0060] A method for preparing a silicon-based composite anode material:

[0061] The only difference between this embodiment and embodiment 1 is that the reaction temperature in step (2) is changed to 400°C and the reaction time is changed to 2h.

[0062] Example 7

[0063] A method for preparing a silicon-based composite anode material:

[0064] The only difference between this embodiment and Embodiment 1 is that the reaction temperature in step (2) is changed to 800°C and the reaction time is changed to 0.2h.

[0065] Example 8

[0066] A method for preparing a silicon-based composite anode material:

[0067] The only difference between this embodiment and Example 1 is that the mass concentration of the HCCP acetonitrile solution in step (3) is changed to 0.1 wt%.

[0068] Example 9

[0069] A method for preparing a silicon-based composite anode material:

[0070] The only difference between this embodiment and Example 1 is that the mass concentration of the HCCP acetonitrile solution in step (3) is changed to 1.5 wt%.

[0071] Example 10

[0072] A method for preparing a silicon-based composite anode material:

[0073] The only difference between this embodiment and embodiment 1 is that the molar ratio of lithium source to sulfur source in step (4) is changed to 1:1.

[0074] Example 11

[0075] A method for preparing a silicon-based composite anode material:

[0076] The only difference between this embodiment and embodiment 1 is that the molar ratio of lithium source to sulfur source in step (4) is changed to 1:5.

[0077] Example 12

[0078] A method for preparing a silicon-based composite anode material:

[0079] The only difference between this embodiment and Embodiment 1 is that the conditions in step (4) are changed to: the dried material, Li2S, and S powder are placed together in a sealed reactor with a volume of 0.5L, ensuring that they do not come into direct contact. Under an Ar atmosphere, the reactor is heated to 200°C and kept at that temperature for 10 hours.

[0080] Example 13

[0081] A method for preparing a silicon-based composite anode material:

[0082] The only difference between this embodiment and Embodiment 1 is that the conditions in step (4) are changed to: the dried material, Li2S, and S powder are placed together in a 10L sealed reactor to ensure that they do not come into direct contact. The reactor is heated to 500°C and held at that temperature for 1 hour under an Ar atmosphere.

[0083] Example 14

[0084] A method for preparing a silicon-based composite anode material:

[0085] The only difference between this embodiment and Embodiment 1 is that the deposition temperature of atomic layer deposition in step (5) is changed to 120°C and the number of cycles is changed to 200.

[0086] Example 15

[0087] A method for preparing a silicon-based composite anode material:

[0088] The only difference between this embodiment and embodiment 1 is that the deposition temperature of atomic layer deposition in step (5) is changed to 180°C and the number of cycles is changed to 10.

[0089] Comparative Example 1

[0090] A method for preparing a silicon-based negative electrode:

[0091] Commercial micron-sized silicon powder (μSi, particle size 1~2μm) without any coating treatment was mixed with conductive carbon black and binder in a weight ratio of 8:1:1 to form a slurry, which was then coated onto copper foil as a negative electrode.

[0092] Comparative Example 2

[0093] A method for preparing a silicon-based negative electrode:

[0094] Referring to the embodiment method of patent CN120727780A, a material (Si@NC@LPO) with nitrogen-doped carbon-coated silicon nanosheets and composite Li3PO4 fast ion conductor layer was prepared and coated on copper foil as a negative electrode.

[0095] Comparative Example 3

[0096] A method for preparing a silicon-based negative electrode:

[0097] The only difference between this comparative example and Example 1 is that the second product obtained in step (2) of Example 1 is directly used as the final negative electrode sample.

[0098] Comparative Example 4

[0099] A method for preparing a silicon-based negative electrode:

[0100] The only difference between this comparative example and Example 1 is that the third product obtained in step (4) of Example 1 is directly used as the final negative electrode sample.

[0101] Battery sample assembly and performance testing: The negative electrode samples obtained from each example and comparative example were assembled into molded all-solid-state half-cells with sulfide solid electrolyte (Li6PS5Cl) and lithium indium alloy sheets, respectively. Then, the electrochemical performance of each battery sample was tested at 55°C, with a voltage range of -0.59 to 0.9 V. The results are recorded in Table 1 below.

[0102] Table 1

[0103]

[0104] In the table above, the discharge capacity is calculated based on the mass of the active material in the negative electrode slurry.

[0105] As can be seen from the above description, compared with the comparative examples, the embodiments of the present invention construct a multi-level synergistic functional coating structure on the surface of silicon-based active materials, thereby achieving the technical effects of improving ion transport efficiency, constraining volumetric strain, suppressing interfacial side reactions, and enhancing the stability of the electrode-electrolyte interface. Specifically:

[0106] A higher initial coulomb efficiency indicates a smaller irreversible capacity loss.

[0107] It exhibits exceptionally high cycling stability, with capacity retention far exceeding that of all comparative studies after 200 cycles.

[0108] It boasts excellent rate performance, delivering high capacity even at 1C high rates.

[0109] The extremely low interfacial impedance indicates that it forms a stable and efficient interface with the sulfide electrolyte in the battery.

[0110] In the various embodiments:

[0111] Comparing Examples 4 and 5 with Example 1, it can be seen that by optimizing the flow ratio of silicon source to carbon source in step S2, the growth rate of silicon nanowires and the density of carbon coating can be controlled more effectively, forming a silicon nanowire composite structure with higher density and more uniform carbon coating on the surface of flexible carbon matrix, thereby more effectively constraining silicon expansion during battery operation.

[0112] Comparing Examples 6 and 7 with Example 1, it can be seen that by optimizing the reaction temperature and reaction time in step S2, the silicon and carbon sources can be completely pyrolyzed to form highly active free radicals, promoting the uniform nucleation of silicon nuclei on the carbon fiber surface. This results in the formation of a composite silicon nanowire structure with better crystallinity, more complete carbon coating, and stronger adhesion on the matrix surface, further optimizing the various properties of the obtained anode material.

[0113] Comparing Examples 8 and 9 with Example 1, it can be seen that by optimizing the mass concentration of the phosphorus source solution in step S3, phosphorus can be more fully adsorbed onto the surface of the silicon-carbon layer, forming a monolayer or sub-monolayer coverage. This satisfies the requirement for a dense Li-PS layer to react with gaseous lithium-sulfur during heat treatment, while also more effectively reducing and avoiding pore formation, further improving the density of the interface structure and ion transport efficiency, and enhancing the electrical performance of the resulting anode material.

[0114] Comparing Examples 10 and 11 with Example 1, it can be seen that by optimizing the molar ratio of lithium source to sulfur source in step S4, the relative concentration of Li and S in the gas phase can be controlled more precisely, and a high ionic conductivity Li-PS composite layer can be generated more efficiently on the surface of the silicon-carbon composite layer, further improving the electrical performance of the obtained silicon-based composite anode material.

[0115] Comparing Examples 12 and 13 with Example 1, it can be seen that by optimizing the reaction conditions in step S4, the gas phase distribution can be made more uniform, the PS-Li bonding can be optimized, the thickness of the resulting composite conductor layer is more uniform and the density is higher, thereby significantly improving the electrical performance and long cycle capability of the resulting silicon-based composite anode material.

[0116] Comparing Examples 14 and 15 with Example 1, it can be seen that by optimizing the deposition temperature and number of cycles of atomic layer deposition in step S5, the precursor and co-reactant can undergo a more efficient self-limiting surface reaction, further optimizing the film quality and improving the electrical performance of the obtained material.

[0117] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based composite negative electrode material, characterized in that, include: Step S1, providing a flexible carbon matrix having two surfaces arranged opposite to each other; Step S2: By means of chemical vapor deposition, silicon source and carbon source are deposited on at least one side surface of the flexible carbon substrate, and a silicon-carbon composite layer is formed on the surface to obtain the first product; Step S3: The first product is placed in a solution containing a phosphorus source and subjected to immersion treatment to obtain the second product; Step S4: Heat treatment is performed on the lithium source, sulfur source and the second product so that the lithium source and the sulfur source react and deposit in gaseous form on the surface of the second product, and a Li-PS composite layer is formed on the surface of the silicon-carbon composite layer to obtain the third product. Step S5: A metal oxide layer is formed on the surface of the Li-PS composite layer by atomic layer deposition to obtain the silicon-based composite anode material.

2. The method for preparing the silicon-based composite anode material according to claim 1, characterized in that, The thickness of the flexible carbon matrix is ​​80 μm to 120 μm; and / or, The flexible carbon matrix is ​​selected from one or more of flexible carbon nonwoven fabric, flexible carbon paper, and graphene flexible film. Preferably, the flexible carbon matrix is ​​a flexible carbon nonwoven fabric, and the fiber diameter in the flexible carbon nonwoven fabric is 5μm~10μm.

3. The method for preparing a silicon-based composite negative electrode material according to claim 1 or 2, characterized in that, In step S2 The flow rate ratio of the silicon source to the carbon source is (4~6):1; and / or, The silicon source is silane; and / or, The carbon source is acrylonitrile and / or acetylene; Preferably, the flow rate of the silicon source is 50±5 sccm, and / or the flow rate of the carbon source is 10±2 sccm.

4. The method for preparing a silicon-based composite negative electrode material according to any one of claims 1 to 3, characterized in that, In step S2 The chemical vapor deposition was performed at 500℃~700℃ for 0.5h~1.5h; and / or, The chemical vapor deposition uses argon as a carrier; and / or, The chemical vapor deposition is performed in a protective atmosphere; Preferably, the protective atmosphere is nitrogen and / or argon.

5. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 4, characterized in that, In step S3 In the solution containing the phosphorus source, the mass concentration of the phosphorus source is 0.2% to 1.0%; and / or, The phosphorus source is selected from one or more of the following: a mixture of triethyl phosphate and dicyandiamide, hexachlorocyclotriphosphazene, and octachlorocyclotetraphosphazene; and / or, The immersion treatment is carried out at 20℃~50℃ for 5s~20s. Preferably, the solution containing the phosphorus source uses one or more of acetonitrile, tetrahydrofuran, dichloromethane, and ethyl acetate as a solvent.

6. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 5, characterized in that, In step S4 The molar ratio of the lithium source to the sulfur source is 1:(2~4); and / or, The lithium source is selected from one or more of Li₂S, LiH, and LiN₃; and / or, The sulfur source is sulfur powder and / or thiourea; Preferably, the lithium source is Li2S and the sulfur source is sulfur powder.

7. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 6, characterized in that, Step S4 includes: placing the lithium source, the sulfur source, and the second product in a reaction vessel with a volume of 1L to 5L, and performing heat treatment at a temperature of 250℃ to 400℃ to sublimate the lithium source and the sulfur source into a gaseous form, and performing the contact reaction and deposition on the surface of the silicon-carbon composite layer for a time of 2h to 8h to obtain the third product.

8. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 7, characterized in that, In step S5 The atomic layer deposition temperature is 120℃~180℃, and the number of cycles is 10~200; and / or, The metal oxide in the metal oxide layer is selected from one or more of Al2O3, SnO2 and TiO2; And / or, The thickness of the metal oxide layer is 0.5 nm to 5 nm; Preferably, step S5 includes: forming an Al2O3 layer on the surface of the Li-PS composite layer by atomic layer deposition, setting the deposition temperature to 150±10℃ and the number of cycles to 5~50, using trimethylaluminum and water as precursors, to obtain the silicon-based composite anode material.

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

10. A sulfide solid-state battery, comprising a negative electrode, characterized in that, The negative electrode is the silicon-based composite negative electrode material as described in claim 9.

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