Micron silicon-based lithium ion battery negative electrode material, negative electrode and preparation method and application of micron silicon-based lithium ion battery negative electrode material
By modifying the surface and structure of photovoltaic micron-sized silicon waste, a fluorine-modified coating layer was constructed, which solved the problems of high energy consumption and strong acid corrosion of micron-sized silicon-based lithium-ion battery anode materials, and achieved efficient resource recycling and improved electrochemical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN CHMM-SUNWARDS NEW MATERIAL CO LTD
- Filing Date
- 2025-12-25
- Publication Date
- 2026-05-19
AI Technical Summary
Existing methods for preparing micron-sized silicon-based lithium-ion battery anode materials suffer from high energy consumption, strong acid corrosion, and toxic gases. Furthermore, nano-scale processes involve high equipment investment, difficulties in large-scale mass production, easy failure of the carbon coating layer, severe electrode pulverization when directly mixed with graphite, and insufficient cycle life.
By recycling photovoltaic micron-sized silicon waste, surface modification and structural alteration are performed. A fluorine-modified coating layer is constructed on the surface of micron-sized silicon using bridging compounds. Combined with the mixing of micron-sized silicon and graphite materials, a stable fluorine-modified coating layer is formed, thereby improving electrochemical performance.
It reduces raw material costs, enables resource recycling, alleviates silicon volume expansion, and improves the structural integrity, electrochemical stability, and rate performance of anode materials.
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Figure CN122067993A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery anode material technology, specifically to a micron-sized silicon-based lithium-ion battery anode material, the anode itself, its preparation method, and its application. Background Technology
[0002] Anode materials are one of the four key materials for lithium-ion batteries, mainly divided into carbon materials and non-carbon materials. Currently, the research and industrialization of silicon-based anode materials for lithium-ion batteries is accelerating to overcome the energy density bottleneck of traditional graphite anodes. Silicon-based anodes, with their ultra-high theoretical specific capacity and low potential characteristics, are considered core materials for next-generation high-energy-density batteries. However, problems such as up to 300% volume expansion during lithium intercalation, low conductivity, and insufficient initial efficiency severely restrict their commercial application. At the technical level, nano-silicon anodes alleviate volume stress through particle nano-sizing (10-100 nm) and improve conductivity and structural stability by combining carbon coating (such as CVD vapor deposition and pyrolytic carbon). However, nano-silicon preparation processes (such as plasma-enhanced chemical vapor deposition and laser-induced chemical vapor deposition) suffer from high equipment investment and difficulties in large-scale mass production. Furthermore, the carbon coating layer is prone to failure due to silicon particle agglomeration, leading to insufficient cycle life. In comparison, while micron-sized silicon anodes are cheaper, their more dramatic volume expansion leads to severe electrode pulverization when directly mixed with graphite, resulting in a significant deterioration in rate performance. Existing solutions, such as porous silicon structure design or the introduction of highly elastic binders (e.g., polyacrylic acid), still struggle to balance capacity and cycle stability. It is worth noting that the photovoltaic industry generates a large amount of micron-sized silicon waste annually during processes such as silicon wafer slicing and grinding. If this high-purity waste is transformed into high-performance anode materials through appropriate recycling processes, it can not only solve environmental problems but also effectively reduce the cost of silicon anodes.
[0003] In existing technologies, for example, patent document CN 104112850 A purifies photovoltaic silicon waste through acid washing, water washing, organic solvent cleaning and high-temperature impurity removal, and uses strong oxidants (such as concentrated HNO3) to modify the surface to generate silanol functional groups, and then physically mixes it with graphite materials. The process relies on specific polymer binders to alleviate the volume expansion of micron-sized silicon. At the same time, particle size control depends on wet etching, and the anisotropic etching precision is difficult to control, which can easily cause excessive corrosion of silicon materials or uneven particle size distribution.
[0004] Patent document CN 105336922 A enhances photovoltaic silicon pretreatment and improves conductivity through in-situ graphite carbon coating, while introducing metal cation crosslinking via a binder system to form a high-strength network. However, metal salt catalysts may retain residual metal impurities during carbon coating, reducing the electrochemical purity of the material. Furthermore, the binder relies on metal ions, requiring precise control of the ion addition amount; excessive addition can easily lead to electrode embrittlement.
[0005] Patent document CN 113387343 A describes a method for breaking photovoltaic silicon wafers to nanoscale using high-energy ball milling, then mixing them with PVP and polyacrylonitrile before electrospinning them into a fiber film, followed by carbonization to obtain a binder-free anode material. However, the ball milling nanoscale process easily introduces iron impurities, reducing silicon purity, and agglomeration still occurs after ball milling dispersion. Furthermore, the stability of the electrospinning process used in this method needs improvement, resulting in limited production yield. Summary of the Invention
[0006] The main objective of this invention is to provide a micron-based silicon anode material, an anode, a method for preparing micron-based silicon lithium-ion battery anode material, and its application, in order to solve the problems of high energy consumption, strong acid corrosion, and toxic gases in existing methods for preparing micron-based silicon lithium-ion battery anode materials.
[0007] To achieve the above objectives, the present invention provides a method for preparing a micron-sized silicon-based lithium-ion battery anode material, comprising the following steps: S1: Recycling micron-sized silicon waste: Recycling photovoltaic micron-sized silicon waste to obtain recycled silicon material A; S2: Surface modification: Recycled silicon material A is added to a bridging compound solution, and the surface of recycled silicon material A is modified and grafted through chemical bonding. After the reaction is completed, it is dried to obtain micron-sized silicon material B. S3: Structural modification: Micron-sized silicon material B is dispersed in a polar solvent, and fluorinated polymerizable monomers and chain initiators are added sequentially. The reaction is carried out under heating conditions to form a stable fluorinated modified coating layer in micron-sized silicon material B. After drying the reactants, micron-sized silicon material C is obtained. S4: Preparation of negative electrode material: Micron-sized silicon material C and graphite negative electrode material are mixed in a ratio of 1:8-10 to obtain micron-sized silicon-based lithium-ion battery negative electrode material.
[0008] Preferably, in step S1, the photovoltaic micron-sized silicon waste is subjected to acid washing, water washing, powdering and grading, alkali washing and water washing and drying, and then passed through a 325-mesh standard sieve to obtain recycled silicon material A.
[0009] Preferably, in step S1, the acid used in the pickling step is one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, and the molar concentration of the pickling is 0.05~2 M; the processing equipment for powdering and grading is a ball mill, vibratory mill, sand mill, roller mill, or air jet mill; the particle size of the micronized silicon powder in powdering and grading is Dv50=2.0~50.0μm, more preferably Dv50=2.0~20.0μm; the alkali used in the alkaline washing step is potassium hydroxide or sodium hydroxide, and the molar concentration of the alkaline washing is 0.05~2 M, the alkaline washing is performed with ultrasonic assistance at 50-100℃ for 0.1-1h, and the volume-to-mass ratio of the alkaline washing aqueous solution to the micronized silicon waste is 1~50 mL / g.
[0010] Specifically, the acid washing molar concentration is further preferably 0.1~1 M, and the powder-making and classification equipment is preferably an air jet mill; the particle size of the powder-making and classification micronized silicon powder is Dv50=2.0~50.0μm, further preferably Dv50=2.0~20.0μm; the purpose of the alkaline washing process is to remove the silicon oxide contained in the micronized photovoltaic silicon waste and the silicon oxide layer on the surface of the powder-making and classification process. In order to improve the silicon oxide alkaline washing removal efficiency, ultrasonic assistance can be used and alkaline washing can be carried out at 50-100℃ for 0.1-1h; the volume-to-mass ratio of the alkaline washing aqueous solution to the micronized silicon waste is further preferably 5~25 mL / g.
[0011] Preferably, in step S2, the bridging compound is added to a mixture of ethanol and water, stirred and dispersed, and the pH value of the solution is controlled at 3-4. After the bridging compound is evenly dispersed, a bridging compound solution is obtained. The recycled silicon material A is added to the bridging compound solution, and the surface of the recycled silicon material A is modified and grafted through chemical bonding. After the reaction is completed, the silicon material B is dried to obtain micron-sized silicon material B.
[0012] Preferably, in step S2, the bridging compound is one or more of silane coupling agents, titanate coupling agents, aluminate coupling agents, metal composite coupling agents, phosphate coupling agents, and borate coupling agents; the volume ratio of ethanol to water is 0.2 to 1, and the pH value of the mixture is adjusted by glacial acetic acid.
[0013] Specifically, in the surface modification of the recovered silicon material A in correction S2, the volume ratio of ethanol to water is 0.2~1, and the pH value of the mixture is adjusted by glacial acetic acid to 3~4; the bridging compound is further preferably a silane coupling agent; the silane coupling agent can be one or more of aminosilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, mercaptosilane coupling agents, methacryloyloxysilane coupling agents, and sulfur-containing silane coupling agents, and is further preferably a vinylsilane coupling agent. The vinylsilane coupling agent can be selected as vinyltrimethoxysilane (Dow Corning Z-6300, Momentive VS-142), vinyltriethoxysilane (Shin-Etsu KBE-1003), 3-methacryloyloxypropyltrimethoxysilane (KH570, Momentive A-174, Dow Corning Z-6030), 3-acryloyloxypropyltrimethoxysilane (Gelest One or more of the following (SIA0590).
[0014] Preferably, in step S3, micron-sized silicon material B is dispersed in a polar solvent, and nitrogen gas is continuously introduced into the solvent. Then, fluorinated polymeric monomers and chain initiators are added sequentially. Under heating conditions, the chain initiator decomposes to generate free radicals, which initiate the copolymerization reaction of the fluorinated polymeric monomers to form a cross-linked polymer network. A stable fluorinated modified coating layer is formed on the micron-sized silicon material B. The reactants are washed and dried with an ethanol aqueous solution to obtain micron-sized silicon material C.
[0015] Preferably, in step S3, the polar solvent is one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), acetonitrile (ACN), tetrahydrofuran (THF), and dimethylacetamide (DMAc); the chain initiator is one or more of dicumyl peroxide (DCP), benzoyl peroxide (BPO), hydrocumyl peroxide, azobisisobutyronitrile (AIBN), and azobisisoheptanenitrile (AVBN); the fluorinated polymerizable monomer is a polyfluorinated or perfluorinated monomer with fluorinated substituents on the ester side chain, fluorinated substituents at the α-position, fluorinated substituents at the β-position, or fluorinated substituents on the main chain; the mass ratio of micron-sized silica material B to the fluorinated polymerizable monomer is 1-5; the mass ratio of the fluorinated polymerizable monomer to the initiator is 33-100; the polymerization temperature is 40-120℃, and the polymerization reaction time is 8-24h; the percentage content of CF species M and Si in the fluorinated modified coating layer on the surface of micron-sized silica material C is... 0 The ratio of the percentage of N in Si-O and Si-OC species is M / N = 5~15.
[0016] Specifically, the polar solvent is further preferably N,N-dimethylformamide (DMF); preferably, the chain initiator is further preferably azobisisobutyronitrile (AIBN).
[0017] Optionally, fluorinated polymeric monomers can be classified as: polyfluorinated or perfluorinated monomers with fluorinated substituents on the ester side chain, fluorinated substituents on the α-position (near the double bond), and fluorinated substituents on the β-position or main chain.
[0018] Fluorine-substituents on the ester side chain are strong electron-withdrawing groups. Through inductive effects, they reduce the electron density of the monomer's double bond, making it more susceptible to free radical attack and thus increasing polymerization activity. Examples of such fluorinated monomers include trifluoromethyl ethyl methacrylate (TFEMA), hexafluorobutyl methacrylate (HFBMA), and trifluoroethyl acrylate (TFEA). Fluorine-substituents at the α-position affect free radical polymerization through steric hindrance and electronic effects. Electron-withdrawing reduces the highest occupied molecular orbital (HOMO) energy level, making the monomer more readily bind to free radicals, but may reduce the degree of polymerization due to steric hindrance. Examples of such fluorinated monomers include hexafluoroisopropyl methacrylate (HFIPMA) and α-fluoroacrylates. Fluorine-substituents at the β-position or on the main chain slightly affect double bond activity through conjugation effects, but primarily enhance the polymer's chemical inertness. Examples of such fluorinated monomers include perfluoroalkyl vinyl ethers and vinyl fluorides. Polyfluorinated or perfluorinated monomers optimize interfacial adsorption through high electronegativity, but excessive fluorine atoms may reduce polymer elasticity and affect its ability to buffer volume expansion. These fluorinated polymer monomers can be perfluorooctyl ethyl methacrylate (FOMA), trifluoromethyl methacrylate (TFMA), etc.
[0019] Optionally, in S3, to reduce the oxygen content of the system, the system can be sonicated for 0.5 hours; Preferably, the polymerization temperature is controlled at 40~120℃, and more preferably at 60~90℃; Preferably, the polymerization reaction time is controlled at 8~24h, during which static conditions are maintained in the system to avoid stirring from interfering with the polymerization; The present invention also provides a micron-sized silicon-based lithium-ion battery anode material, which is prepared by the preparation method described above.
[0020] The present invention also provides a negative electrode, which is prepared using the micron-sized silicon-based lithium-ion battery negative electrode material as described above.
[0021] The present invention also provides an application of the micron-sized silicon-based lithium-ion battery anode material prepared according to the above preparation method as a battery anode material.
[0022] The micron-sized silicon-based lithium-ion battery anode material, anode, and its preparation method and application in this invention include the following steps: impurity removal, surface modification, and structural modification of photovoltaic micron-sized silicon waste. The photovoltaic micron-sized silicon material is silicon waste generated during photovoltaic silicon processing, mainly comprising micron-sized silicon from cutting, amorphous silicon oxide, polyethylene glycol from cutting fluid, and trace amounts of metallic impurities. Through impurity removal, surface modification, and structural modification of the photovoltaic micron-sized silicon waste, a silicon-based lithium-ion anode material with excellent electrochemical performance is obtained. The surface modification and structural modification involve constructing an elastic and fluorine-rich polymer layer on the surface of micron-sized photovoltaic silicon using bridging compounds. This fluorine-modified layer not only provides mechanical buffering but also induces the formation of a stable LiF-rich SEI layer in the electrolyte, thereby improving the electrochemical performance of the micron-sized silicon-based lithium-ion anode. In this invention, photovoltaic waste silicon is used as a raw material. Through purification and modification, the resource utilization of photovoltaic silicon waste is achieved, avoiding the complex synthesis process of high-purity silicon for silicon-based anode materials, significantly reducing raw material costs, and realizing resource recycling. This invention achieves effective coating of a fluoropolymer-modified layer on the surface of recycled silicon material by constructing an "inorganic-organic" bridging interface. A silane coupling agent forms a strong Si-O-Si covalent bond through condensation with hydroxyl groups on the micron-sized silicon surface. Simultaneously, the remaining active double bonds of the bridging silane coupling agent undergo free radical polymerization with fluorinated monomers under initiator conditions, forming a growing chain and ultimately constructing an elastic polymer layer. The fluorinated groups in the modified layer, as strong electron-withdrawing groups, reduce interfacial energy and effectively promote LiF generation during electrochemical processes. Furthermore, the constructed fluorinated modified layer alleviates silicon expansion, reduces particle breakage, and minimizes repeated SEI rupture. This simultaneously improves the structural integrity, electrochemical stability, and rate performance of the micron-sized silicon-based anode. Attached Figure Description
[0023] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram illustrating the preparation of the fluorine-modified layer on the surface of the micron-sized silicon-based anode material in this invention.
[0024] Figure 2 This is an electron microscope image of the micron-sized silicon material C in Example 1 of the present invention.
[0025] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0026] The technical problems solved by the embodiments of the present invention, the technical solutions adopted, and the technical effects achieved will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other equivalent or obvious variations of embodiments obtained by those skilled in the art without creative effort fall within the protection scope of the present invention. The embodiments of the present invention can be embodied in various different ways as defined and covered by the claims.
[0027] It should be noted that many specific details are given in the following description for ease of understanding. However, it is obvious that the present invention may be implemented without these specific details.
[0028] It should be noted that, in the absence of explicit limitations or conflicts, the various embodiments and their technical features in this invention can be combined with each other to form a technical solution.
[0029] Example 1: S1: Removal of impurities from photovoltaic micron-sized silicon waste Photovoltaic micronized silicon waste was washed and filtered in a 0.5M hydrochloric acid solution, rinsed with water and dried. The acid-washed micronized silicon waste was then powdered and classified using an air jet mill. The air jet mill classification and frequency were adjusted to obtain micronized silicon powder with a particle size Dv50 = 10.8 μm. The obtained micronized silicon powder was then added to a 1M sodium hydroxide aqueous solution, and ultrasonic cleaning was performed at a controlled temperature of 50-100℃ for 0.1-1 h. After centrifugation and drying, the residue was passed through a 325-mesh standard sieve to obtain recycled silicon material A. S2: Surface modification of micron-sized silicon The silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) was added to a mixture of ethanol and water, wherein the volume ratio of ethanol to water was 0.2~1. After stirring and dispersing, glacial acetic acid was added to control the pH of the mixture to 3~4. After the vinyl silane coupling agent was evenly dispersed, recycled silicon material A was added to the mixture. After the reaction was completed, the mixture was washed with water and dried to obtain micron-sized silicon material B. S3: Structural modification of micron-sized silicon Micron-sized silica material B was dispersed in DMF solvent, and nitrogen gas was continuously introduced into the solvent. Then, a fluorinated polymeric monomer (fluorinated substituents on the ester side chain), trifluoromethyl ethyl methacrylate (CF3-CH2-CH2-O-CO-C(CH3)=CH2, TFEMA), and a chain initiator, azobisisobutyronitrile (AIBN), were added sequentially. Under heating conditions of 60–90 °C, the chain initiator decomposed to generate free radicals, forming a stable fluorinated modified coating layer on the micron-sized silica material B. After washing with an ethanol-water solution and drying at 60 °C, micron-sized silica material C was obtained. S4: Micron-sized silicon material C is blended with commercial artificial graphite (Dv50=10.2μm, specific capacity: 350 mAh / g), wherein the mass blending ratio of graphite to micron-sized silicon material C is 9:1. After blending and sieving, it is used as a lithium-ion anode material.
[0030] Example 2: S1: Removal of impurities from photovoltaic micron-sized silicon waste Photovoltaic micronized silicon waste was washed and filtered in a 0.5M hydrochloric acid solution, rinsed with water and dried. The acid-washed micronized silicon waste was then powdered and classified using an air jet mill. The air jet mill classification and frequency were adjusted to obtain micronized silicon powder with a particle size Dv50 = 10.8 μm. The obtained micronized silicon powder was then added to a 1M sodium hydroxide aqueous solution, and ultrasonic cleaning was performed at a controlled temperature of 50-100℃ for 0.1-1 h. After centrifugation and drying, the residue was passed through a 325-mesh standard sieve to obtain recycled silicon material A. S2: Surface modification of micron-sized silicon The silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) was added to a mixture of ethanol and water, wherein the volume ratio of ethanol to water was 0.2~1. After stirring and dispersing, glacial acetic acid was added to control the pH of the mixture to 3~4. After the vinyl silane coupling agent was evenly dispersed, recycled silicon material A was added to the mixture. After the reaction was completed, the mixture was washed with water and dried to obtain micron-sized silicon material B. S3: Structural modification of micron-sized silicon Micron-sized silica material B was dispersed in DMF solvent, and nitrogen gas was continuously introduced into the solvent. Then, a fluorinated polymeric monomer (fluorinated substituents on the ester side chain), hexafluorobutyl methacrylate (CF3-(CF2)5-CH2-CH2-O-CO-C(CH3)=CH2, HFBMA), and a chain initiator, azobisisobutyronitrile (AIBN), were added sequentially. Under heating conditions of 60–90 °C, the chain initiator decomposed to generate free radicals, forming a stable fluorinated modified coating layer on the micron-sized silica material B. After washing with an ethanol-water solution and drying at 60 °C, micron-sized silica material C was obtained. S4: Micron-sized silicon material C is blended with commercial artificial graphite (Dv50=10.2μm, specific capacity: 350 mAh / g), wherein the mass blending ratio of graphite to micron-sized silicon material C is 9:1. After blending and sieving, it is used as a lithium-ion anode material.
[0031] Example 3: S1: Removal of impurities from photovoltaic micron-sized silicon waste Photovoltaic micronized silicon waste was washed and filtered in a 0.5M hydrochloric acid solution, rinsed with water and dried. The acid-washed micronized silicon waste was then powdered and classified using an air jet mill. The air jet mill classification and frequency were adjusted to obtain micronized silicon powder with a particle size Dv50 = 10.8 μm. The obtained micronized silicon powder was then added to a 1M sodium hydroxide aqueous solution, and ultrasonic cleaning was performed at a controlled temperature of 50-100℃ for 0.1-1 h. After centrifugation and drying, the residue was passed through a 325-mesh standard sieve to obtain recycled silicon material A. S2: Surface modification of micron-sized silicon The silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) was added to a mixture of ethanol and water, wherein the volume ratio of ethanol to water was 0.2~1. After stirring and dispersing, glacial acetic acid was added to control the pH of the mixture to 3~4. After the vinyl silane coupling agent was evenly dispersed, recycled silicon material A was added to the mixture. After the reaction was completed, the mixture was washed with water and dried to obtain micron-sized silicon material B. S3: Structural modification of micron-sized silicon Micron-sized silica material B was dispersed in DMF solvent, and nitrogen gas was continuously introduced into the solvent. Then, a fluorinated polymeric monomer (fluorinated substituents on the ester side chain), trifluoroethyl acrylate (CF3-CH2-CH2-O-CO-CH=CH2, TFEA), and a chain initiator azobisisobutyronitrile (AIBN) were added sequentially. Under heating conditions of 60–90 °C, the chain initiator decomposed to generate free radicals, forming a stable fluorinated modified coating layer on the micron-sized silica material B. After washing with an ethanol-water solution and drying at 60 °C, micron-sized silica material C was obtained. S4: Micron-sized silicon material C is blended with commercial artificial graphite (Dv50=10.2μm, specific capacity: 350 mAh / g), wherein the mass blending ratio of graphite to micron-sized silicon material C is 9:1. After blending and sieving, it is used as a lithium-ion anode material.
[0032] Example 4: S1: Removal of impurities from photovoltaic micron-sized silicon waste Photovoltaic micronized silicon waste was washed and filtered in a 0.5M hydrochloric acid solution, rinsed with water and dried. The acid-washed micronized silicon waste was then powdered and classified using an air jet mill. The air jet mill classification and frequency were adjusted to obtain micronized silicon powder with a particle size Dv50 = 10.8 μm. The obtained micronized silicon powder was then added to a 1M sodium hydroxide aqueous solution, and ultrasonic cleaning was performed at a controlled temperature of 50-100℃ for 0.1-1 h. After centrifugation and drying, the residue was passed through a 325-mesh standard sieve to obtain recycled silicon material A. S2: Surface modification of micron-sized silicon The silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) was added to a mixture of ethanol and water, wherein the volume ratio of ethanol to water was 0.2~1. After stirring and dispersing, glacial acetic acid was added to control the pH of the mixture to 3~4. After the vinyl silane coupling agent was evenly dispersed, recycled silicon material A was added to the mixture. After the reaction was completed, the mixture was washed with water and dried to obtain micron-sized silicon material B. S3: Structural modification of micron-sized silicon Micron-sized silica material B was dispersed in DMF solvent, and nitrogen gas was continuously introduced into the solvent. Then, a fluorinated polymerizable monomer (fluorinated substituent at the α-position) hexafluoroisopropyl methacrylate ((CF3)3C-O-CO-C(CH2)=CH2, HFIPMA) and a chain initiator azobisisobutyronitrile (AIBN) were added sequentially. Under heating conditions of 60–90 °C, the chain initiator decomposed to generate free radicals, forming a stable fluorinated modified coating layer on the micron-sized silica material B. After washing with an ethanol-water solution and drying at 60 °C, micron-sized silica material C was obtained. S4: Micron-sized silicon material C is blended with commercial artificial graphite (Dv50=10.2μm, specific capacity: 350 mAh / g), wherein the mass blending ratio of graphite to micron-sized silicon material C is 9:1. After blending and sieving, it is used as a lithium-ion anode material.
[0033] Example 5: S1: Removal of impurities from photovoltaic micron-sized silicon waste Photovoltaic micronized silicon waste was washed and filtered in a 0.5M hydrochloric acid solution, rinsed with water and dried. The acid-washed micronized silicon waste was then powdered and classified using an air jet mill. The air jet mill classification and frequency were adjusted to obtain micronized silicon powder with a particle size Dv50 = 10.8 μm. The obtained micronized silicon powder was then added to a 1M sodium hydroxide aqueous solution, and ultrasonic cleaning was performed at a controlled temperature of 50-100℃ for 0.1-1 h. After centrifugation and drying, the residue was passed through a 325-mesh standard sieve to obtain recycled silicon material A. S2: Surface modification of micron-sized silicon The silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) was added to a mixture of ethanol and water, wherein the volume ratio of ethanol to water was 0.2~1. After stirring and dispersing, glacial acetic acid was added to control the pH of the mixture to 3~4. After the vinyl silane coupling agent was evenly dispersed, recycled silicon material A was added to the mixture. After the reaction was completed, the mixture was washed with water and dried to obtain micron-sized silicon material B. S3: Structural modification of micron-sized silicon Micron-sized silica material B was dispersed in DMF solvent, and nitrogen gas was continuously introduced into the solvent. Then, fluorinated polymeric monomers (fluorinated substituents at the α-position), α-fluoroacrylate (F-CH2-CO-O-CH=CH2), and chain initiator azobisisobutyronitrile (AIBN) were added sequentially. Under heating conditions of 60–90 °C, the chain initiator decomposed to generate free radicals, forming a stable fluorinated modified coating layer on micron-sized silica material B. After washing with an ethanol-water solution and drying at 60 °C, micron-sized silica material C was obtained. S4: Micron-sized silicon material C is blended with commercial artificial graphite (Dv50=10.2μm, specific capacity: 350 mAh / g), wherein the mass blending ratio of graphite to micron-sized silicon material C is 9:1. After blending and sieving, it is used as a lithium-ion anode material.
[0034] Comparative Example 1: The difference between this comparative example and Example 1 is that steps S2 and S3 are omitted, and the recycled silicon material A is directly mixed with the graphite material in step S4 as micron-sized silicon material. The remaining steps and parameters are consistent with those of the example.
[0035] Comparative Example 2: The difference between this comparative example and Example 1 is that step S2 is omitted, and the fluoropolymer modification in S3 is carried out directly on the recycled silicon material A. The remaining steps and parameters are consistent with those of the example.
[0036] Comparative Example 3: The difference between this comparative example and Example 1 is that no chain initiator was added in step S3, while the remaining steps and parameters are consistent with those of the example.
[0037] Comparative Example 4: The difference between this comparative example and Example 1 is that in step S3, the fluorinated polymerizable monomer has fluorine substituents in the main chain type, and is a perfluoromethyl vinyl ether (CF3-O-CF=CF2). The remaining steps and parameters are consistent with those of the example.
[0038] Comparative Example 5: The difference between this comparative example and Example 1 is that the fluorinated polymerizing monomer in step S3 is a polyfluorinated or perfluorinated monomer, perfluorooctyl ethyl methacrylate (CF3(CF2)7-CH2-CH2-O-CO-C(CH3)=CH2). The remaining steps and parameters are consistent with those of the example.
[0039] Please combine them together Figure 1 and Figure 2The negative electrode materials from Examples 1-6 and Comparative Examples 1-5 were used as negative electrode active materials. They were mixed with a conductive agent, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) at a mass ratio of 95:1:2.5:1.5 and then coated onto copper foil. The electrode was then vacuum-dried at 105°C for 24 hours. Button cells were assembled in a glove box. The electrolyte was LiPF6 at a concentration of 1 M, and the solvent consisted of dimethyl carbonate, ethylene carbonate, and ethyl methyl carbonate in a volume ratio of 1:1:1. The counter electrode was a lithium sheet. Initial coulombic efficiency, rate performance, and cycle performance tests were conducted under the following conditions, and the results are shown in Table 1.
[0040] The following describes the testing methods for various performance parameters of the recycled graphite anode material in this invention.
[0041] X-ray photoelectron spectroscopy (XPS) test: Take an appropriate amount of sample, compress it into a pellet, place it on a sample tray, and put the sample into the sample chamber of the VGScienta R3000 instrument. The sample is then analyzed at 1×10⁻⁶. -10 Under ultra-high vacuum conditions of mbar, tests were conducted using a monochromatic Al(Kα) X-ray source with an energy of 1486.6 eV. XPS data were processed using Avantage software to perform compositional analysis on the surface of the anode material. The percentage of CF species in the F 1s spectrum was denoted as M, representing the percentage of carbon component area attributable to CF bonds in the XPS spectrum relative to the total carbon spectrum area (e.g., the peak area ratio of -CF2 (~293 eV) and -CF2- (~291 eV) in the C 1s spectrum). This value reflects the coverage of the fluorinated polymer layer. The Si 2p spectrum of the sample was then analyzed. 0 The percentage content of Si-O and Si-OC species is denoted as N, which is the value of Si in the Si 2p spectrum. 0 The M / N ratio is the percentage of the total silicon spectral area represented by the sum of the peak areas of elemental silicon (~99 eV), Si-O (silicon oxide, ~103 eV), and Si-OC (covalent bond between silane coupling agent and silicon, ~102 eV). This value reflects the degree of silicon substrate exposure. When the fluorine content of the polymer monomers is similar, the M / N value is used to characterize the integrity of the fluorinated layer coverage. A higher M / N indicates a more continuous and dense fluorinated layer, and a more significant shielding of the silicon substrate signal. Initial coulombic efficiency test: The graphite was first discharged at a current of 0.2 mA to 0.01 V, allowed to stand for 10 min, and then charged at a rate of 0.1 C to 2.00 V to test the initial coulombic efficiency.
[0042] Rate performance test: After the material completes the first charge and discharge test, it is discharged at constant current and constant voltage (1C / 0.1C) to 0.01V, left to stand for 10 min, and then charged at constant current (1C / 0.1C) to 2V. The capacity at different rates is calculated.
[0043] Cyclic performance test: After the material completes the first charge and discharge test, it is discharged under constant current and constant voltage (1 C) to 0.2 V, charged under constant current (1 C) to 1.5 V, and cycled for 500 cycles. The capacity retention rate at the 500th cycle is calculated.
[0044] Table 1 Battery performance data for each sample As can be seen from the performance data in Table 1, the overall performance of the graphite anode materials prepared by the present invention in Examples 1-5 is better than that of the graphite anode materials prepared in Comparative Examples 1-5. The specific analysis is as follows.
[0045] Examples 1-5 demonstrate that bridging with vinyl silane coupling agents to modify the surface fluorinated layer of photovoltaic micron-sized silicon can achieve excellent rate performance and good cycle stability in micron-sized silicon anode materials. The fluorine substituents in the surface fluorinated layer effectively adsorb electrolyte, promoting LiF formation and providing a stable SEI, thereby reducing the consumption of active lithium in the first cycle and improving the first coulombic efficiency. The fluorinated modified layer acts as a physical barrier, isolating the silicon surface from the electrolyte and reducing LiPF6 hydrolysis. Furthermore, the elasticity of the cross-linked polymer network can accommodate silicon expansion, preventing particle breakage and repeated SEI rupture. This ensures the stability of the cycling process. Simultaneously, the induced LiF, a fast ion conductor, effectively reduces the migration resistance of lithium ions in the SEI bulk phase, improving the rate performance of the micron-sized silicon-based anode.
[0046] As shown in Example 1 and Comparative Example 2, the vinylsilane coupling agent in S2 forms a stable covalent bond with the silicon surface through a hydrolysis-condensation reaction, providing an anchoring point for the subsequent polymer layer. In Comparative Example 2, the lack of a stable intermediate layer bridge for the subsequent fluorinated monomer results in poor cycle stability and rate performance.
[0047] As can be seen from Examples 1 and 3, the polymerization reaction of fluorinated monomers depends on the active free radicals generated by the initiator, which attack the carbon-carbon double bonds at the ends of the fluorinated monomers and silane coupling agents to initiate a chain polymerization reaction and promote the formation of the fluorinated coating layer.
[0048] Examples 1 and Comparative Examples 4 and 5 show that fluorine substituents at the ester side chain and fluorine substituents at the α-position have better modification effects than fluorine substituents at the main chain type and perfluorinated monomer type. These monomers typically exhibit high polarity due to the strong electronegativity of fluorine atoms, but steric hindrance or electronic effects may affect the controllability of polymerization. Furthermore, excessive fluorine atoms in perfluorinated / polyfluorinated monomers may reduce polymer elasticity and affect their ability to buffer volume expansion. A balance must be struck between fluorine content and structural flexibility when selecting monomers.
[0049] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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. Such 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, and should all be included within the protection scope of the present invention.
Claims
1. A method for preparing a micron-sized silicon-based lithium-ion battery anode material, characterized in that, Including the following steps: S1: Recycling micron-sized silicon waste: Recycling photovoltaic micron-sized silicon waste to obtain recycled silicon material A; S2: Surface modification: Recycled silicon material A is added to a bridging compound solution, and the surface of recycled silicon material A is modified and grafted through chemical bonding. After the reaction is completed, it is dried to obtain micron-sized silicon material B. S3: Structural modification: Micron-sized silicon material B is dispersed in a polar solvent, and fluorinated polymerizable monomers and chain initiators are added sequentially. The reaction is carried out under heating conditions to form a stable fluorinated modified coating layer in micron-sized silicon material B. After drying the reactants, micron-sized silicon material C is obtained. S4: Preparation of negative electrode material: Micron-sized silicon material C and graphite negative electrode material are mixed in a ratio of 1:8-10 to obtain micron-sized silicon-based lithium-ion battery negative electrode material.
2. The method for preparing the micron-sized silicon-based lithium-ion battery anode material according to claim 1, characterized in that, In step S1, the photovoltaic micron silicon waste is subjected to acid washing, water washing, powdering and grading, alkali washing and water washing and drying, and then passed through a 325-mesh standard sieve to obtain recycled silicon material A.
3. The method for preparing the micron-sized silicon-based lithium-ion battery anode material according to claim 1, characterized in that, In step S2, the bridging compound is added to a mixture of ethanol and water, stirred and dispersed, and the pH of the solution is controlled at 3-4. After the bridging compound is evenly dispersed, a bridging compound solution is obtained. The recycled silicon material A is added to the bridging compound solution, and the surface of the recycled silicon material A is modified and grafted through chemical bonding. After the reaction is completed, the silicon material B is dried to obtain micron-sized silicon material B.
4. The method for preparing the micron-sized silicon-based lithium-ion battery anode material according to claim 3, characterized in that, In step S3, micron-sized silicon material B is dispersed in a polar solvent, and nitrogen gas is continuously introduced into the solvent. Then, fluorinated polymeric monomers and chain initiators are added sequentially. Under heating conditions, the chain initiator decomposes to generate free radicals, which initiate the copolymerization reaction of the fluorinated polymeric monomers to form a cross-linked polymer network. A stable fluorinated modified coating layer is formed on the micron-sized silicon material B. After the reactants are washed and dried with an ethanol aqueous solution, micron-sized silicon material C is obtained.
5. The method for preparing the micron-sized silicon-based lithium-ion battery anode material according to claim 2, characterized in that, In step S1, the acid used in the pickling step is one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, and the molar concentration of the acid is 0.05~2 M; the processing equipment for powdering and grading is a ball mill, vibratory mill, sand mill, roller mill, or air jet mill; the particle size of the micronized silicon powder in powdering and grading is Dv50=2.0~50.0μm, more preferably Dv50=2.0~20.0μm; the alkali used in the alkaline washing step is potassium hydroxide or sodium hydroxide, and the molar concentration of the alkali is 0.05~2 M. The alkali washing is performed with ultrasonic assistance at 50-100℃ for 0.1-1h, and the volume-to-mass ratio of the alkali washing aqueous solution to the micronized silicon waste is 1~50 mL / g.
6. The method for preparing the micron-sized silicon-based lithium-ion battery anode material according to claim 3, characterized in that, In step S2, the bridging compound is one or more of the following: silane coupling agent, titanate coupling agent, aluminate coupling agent, metal composite coupling agent, phosphate coupling agent, and borate coupling agent; the volume ratio of ethanol to water is 0.2 to 1, and the pH value of the mixture is adjusted by glacial acetic acid.
7. The method for preparing the micron-sized silicon-based lithium-ion battery anode material according to claim 4, characterized in that, In step S3, the polar solvent is one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, tetrahydrofuran, and dimethylacetamide; the chain initiator is one or more of dicumyl peroxide, benzoyl peroxide, hydrocumyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile; the fluorinated polymeric monomer is a polyfluorinated or perfluorinated monomer with fluorinated substituents on the ester side chain, α-position, β-position, or main chain; the mass ratio of micron-sized silica material B to the fluorinated polymeric monomer is 1-5; the mass ratio of the fluorinated polymeric monomer to the initiator is 33-100; the polymerization temperature is 40-120℃, and the polymerization reaction time is 8-24h; the percentage content of CF species M and Si in the fluorinated modified coating layer on the surface of micron-sized silica material C is... 0 The ratio of the percentage of N in Si-O and Si-OC species is M / N = 5~15.
8. A micron-sized silicon-based lithium-ion battery anode material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7.
9. A negative electrode, characterized in that, Prepared using the micron-sized silicon-based lithium-ion battery anode material as described in claim 8.
10. The application of a micron-sized silicon-based lithium-ion battery anode material prepared by any one of claims 1-7 as a battery anode material.