A method for preparing tin-carbon anode material for lithium batteries

Abstract

This invention relates to the field of battery materials technology and discloses a method for preparing a tin-carbon anode material for lithium batteries, comprising the following steps: S1: selecting high-purity tin powder and carbon source material; S2: mixing the tin source and carbon source in a certain proportion and then using methods such as ball milling and ultrasonic vibration; S3: subjecting the mixture to high-temperature heat treatment to convert the carbon source into graphite or other carbon forms and promote the bonding of tin and carbon; S4: further processing the carbonized material; S5: pulverizing and screening the heat-treated composite material, and then mixing it with binders, conductive additives, etc., as needed to prepare an electrode slurry; S6: coating the electrode slurry onto copper foil or aluminum foil, and forming the electrode using processes such as coating, scraping, and calendering, followed by drying and compaction to obtain the final electrode. This invention uses ball milling to break tin-carbon particles to the micron level and then uses ultrasonic vibration to disperse them to the 100-500 nm nanometer level, completely eliminating agglomeration.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically a method for preparing a tin-carbon anode material for lithium batteries. Background Technology

[0002] The tin-carbon anode material for lithium-ion batteries is a composite material made of tin (Sn) and carbon materials (such as graphite, carbon nanotubes, graphene, etc.). Tin is a material with a high theoretical capacity and high specific capacity, but it is prone to expansion and contraction during charging and discharging, resulting in poor cycle stability. To solve this problem, researchers have combined tin with carbon materials, which can improve the conductivity of tin and alleviate the expansion problem of tin, thereby improving the performance of the battery.

[0003] Chinese patent discloses a method for preparing carbon-coated tin oxide anode material for lithium batteries (authorization announcement number CN108899491A). The tin oxide used in this patented technology is in the form of nanofibers, with uniform through-holes distributed on each fiber, which effectively suppresses the volume expansion and contraction of tin oxide. Under the same conditions, more lithium ions can be inserted, thus improving the energy density of the battery. This invention improves the conductivity of the active material through carbon-nitrogen composite. In addition, the cavity between the nitrogen-doped carbon layer and the tin oxide provides effective space for the volume expansion of the active material during lithium insertion / extraction, preventing the pulverization and agglomeration of tin oxide.

[0004] However, existing tin powders are prone to agglomeration during preparation due to oxidation, high-temperature melting, or mechanical forces, leading to a reduction in active sites and decreased conductivity. Furthermore, the dramatic volume expansion of tin during charging and discharging can cause electrode cracking, active material shedding, and a significant shortening of cycle life. Therefore, those skilled in the art have provided a method for preparing tin-carbon anode materials for lithium batteries to address the problems mentioned in the background. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a tin-carbon anode material for lithium batteries, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a tin-carbon anode material for lithium batteries includes the following steps: S1: Select high-purity tin powder and carbon source materials, and process the raw materials; S2: Mix the tin source and carbon source in a certain proportion, and promote the uniform dispersion of the two by methods such as ball milling and ultrasonic vibration. S3: The mixture is subjected to high-temperature heat treatment to convert the carbon source into graphite or other carbon forms and to promote the combination of tin and carbon. S4: Further process the carbonized material; S5: The heat-treated composite material is crushed and screened to obtain the required particle size. Then, it is mixed with binders, conductive additives, etc. as needed to prepare an electrode slurry. S6: The electrode paste is coated onto copper or aluminum foil, and the electrode is formed by processes such as coating, scraping, and rolling. Then, it is dried and compacted to obtain the final electrode. S7: Assemble the prepared negative electrode material together with other battery components (such as positive electrode, separator, electrolyte) into a complete lithium battery.

[0007] As a further aspect of the present invention: the carbon source material in S1 is graphite, carbon black, carbon nanotubes, graphene, etc., and the raw material processing involves two steps: washing and drying. The cleaning process involves using organic solvents such as ethanol and acetone to ultrasonically clean the tin powder. After cleaning, the tin powder is rinsed with deionized water to remove any residual organic solvents. The drying temperature of the tin powder can be controlled at 80-120℃, and the drying time is 2-4 hours.

[0008] As a further embodiment of the present invention: a conductive agent is added to S2, wherein the conductive agent is carbon nanotubes or graphene, and the mass ratio of tin to carbon in the tin source and carbon source is 1:1 to 1:5.

[0009] As a further embodiment of the present invention: in S2, the ball milling adopts a planetary ball mill or a stirred ball mill, wherein the grinding balls are selected with a diameter of 5-10 mm when the initial particle size is large, and 1-3 mm grinding balls are selected in the finer stage. The ball-to-material ratio is 5:1-15:1. The rotation speed of the planetary ball mill is generally 200-400 rpm, and the rotation speed of the stirred ball mill is 500-1000 rpm. The ball milling time is usually 2-8 hours. During the ball milling process, a nitrogen or argon inert atmosphere needs to be introduced to prevent the tin powder from oxidizing upon contact with air and forming tin oxide.

[0010] As a further aspect of the present invention: the ultrasonic vibration in S2 is performed using an ultrasonic cell disruptor equipped with a titanium alloy ultrasonic probe. In S2, the initial particles of the tin source and carbon source are first broken down to the micron level (1-10μm) by ball milling to achieve preliminary mixing. The micron-sized particles are then dispersed to the nanoscale (100-500nm) using ultrasonic vibration, and agglomeration is further eliminated, ultimately obtaining a tin-carbon mixture with uniform particle size and thorough mixing.

[0011] As a further aspect of the present invention: the carbon source in S3 undergoes three high-temperature heating treatments. First high-temperature treatment: Under the protection of inert gas (argon, nitrogen, etc.), the temperature is increased to 250-500℃ at a rate of 3-10℃ / min, stirred and kept at the temperature for 2-8 hours, the tin material melts into liquid and penetrates into the pores of the carbon material, and after cooling, the second mixed material is obtained. Second high-temperature treatment: The second mixed material is mixed with graphite at a mass ratio of (1-10):100, and heated to 400-700℃ at a rate of 3-10℃ / min under inert gas protection, and held at this temperature for 2-7 hours, so that the second mixed material forms a uniform composite layer on the graphite surface, thus obtaining the initial negative electrode material. The third high-temperature treatment: the carbon source material and the initial anode material are mixed at a mass ratio of (3-8):100, and heated to 700-1000℃ at 3-10℃ / min under inert gas protection, and held for 6-10 hours. The carbon source material (such as resin, organic carbon precursor) is converted into amorphous carbon or graphite-like carbon, forming a carbonization layer on the surface of the composite layer, and finally obtaining the tin-carbon anode material. In the S3 process, tin powder is heated to 500-1200°C at a rate of 2-20°C / min in a protective atmosphere (argon, nitrogen, or argon-hydrogen mixture) and held for 0.5-8 hours. Tin-containing compounds are pyrolyzed to generate elemental tin or tin-based compounds, while organic ligands are converted into amorphous carbon. Tin species combine with carbon in situ to form tin-carbon composite materials. After cooling, the sample was washed with deionized water at 20–90°C to remove impurities and obtain a tin-carbon composite intermediate. The three-dimensional network framework (such as porous carbon, carbon nanotubes, and graphene) formed during the carbonization process of the carbon source can "anchor" tin particles through spatial confinement.

[0012] As a further aspect of the present invention, the specific steps in S4 are as follows: S41: Take the tin-carbon composite material after S3 carbonization, add 5% hydrochloric acid solution, stir at 80℃ for 2 hours to remove surface SnO2. S42: Rinse with deionized water until pH=7, then soak in anhydrous ethanol for 1 hour and separate by filtration; S43: Place the material in a vacuum drying oven and dry it at 80°C for 6 hours to obtain a dried tin-carbon intermediate; S44: The intermediate is mixed with a 10% sucrose solution (mass ratio 10:1), ultrasonically dispersed for 30 minutes, and then heat-treated at 400℃ for 2 hours under an Ar atmosphere to form a secondary carbon coating layer.

[0013] S45: Remove after cooling.

[0014] As a further embodiment of the present invention: S5 employs coarse crushing and fine crushing, wherein coarse crushing uses a jaw crusher with the gap adjusted to 1-5mm and a high-speed shear machine with a speed of 1000-3000rpm, and fine crushing uses a planetary ball mill with a speed of 200-400rpm and a crushing time of 2-6 hours. After pulverization, the material is graded and screened using a vibrating screen. A 300 mesh inset screen (to remove coarse particles >53µm) and an 800 mesh main screen (to retain fine powder <18µm) are selected. A small amount of inert gas can be introduced during screening. The electrode slurry employs three stages. First stage: Put the tin-carbon composite material and conductive additive into a double planetary mixer and stir at low speed (50-100 rpm) for 10-20 minutes to make the solid particles initially mixed evenly and form a dry powder mixture. Second stage: Add the adhesive to the solvent and stir with a high-speed disperser (2000-3000 rpm) for 30-60 minutes until the adhesive is completely dissolved and a transparent adhesive solution is formed; Slowly add the dry powder mixture to the adhesive solution (stirring while adding to prevent local agglomeration), and then use a double planetary mixer to alternate between "low-speed stirring + high-speed dispersion": first stir at low speed (100-200 rpm) for 30 minutes, and then disperse at high speed (500-800 rpm) for 1-2 hours. During this period, you can pause 1-2 times and scrape off the material remaining on the container wall with a scraper to ensure thorough mixing. Third stage: After dispersion is completed, the viscosity of the slurry is measured with a rotational viscometer. The target range is usually 5000 to 20000 mPa·s. If the viscosity is too high, add a small amount of solvent (NMP or water); if the viscosity is too low, evaporate a small amount of solvent while stirring at low speed (e.g., by heating at 60-80°C). Finally, filter the slurry with a 120-200 mesh filter to remove undispersed small agglomerates and ensure that the slurry is free of impurities.

[0015] As a further embodiment of the present invention: in step S6, an electrolytic copper foil with a thickness of 8 to 12 μm is first selected, and the aluminum foil is ultrasonically cleaned with anhydrous ethanol or isopropanol to remove surface oil stains. After cleaning, it is vacuum dried at 60 to 80°C for 30 minutes. The coating is applied by using a manual coating machine with a doctor blade (gap 50-200μm) at a speed of 5-15cm / s to form a wet film. The wet film drying process employs a progressive increase of low temperature, medium temperature, and high temperature to achieve the drying effect. The compaction is performed using a roller press with a pressure of 5 to 20 MPa.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention can thoroughly remove oil and residual solvents from the surface of tin powder by organic solvent cleaning + deionized water rinsing + vacuum drying, avoiding impurities from affecting tin-carbon bonding. The increased purity directly reduces side reactions during battery charging and discharging, increasing the first charge-discharge efficiency to over 80% and the capacity retention rate to ≥70% after 50 cycles.

[0017] 2. The ball mill, ultrasonic crusher, tube furnace, coating machine and other equipment in this invention are all conventional equipment in the lithium battery industry. There is no need to customize special devices, which lowers the threshold for industrialization. The parameters of each step are given with clear ranges, which can be easily adjusted according to actual needs.

[0018] 3. The copper foil pretreatment and precise coating method of this invention can improve the adhesion of the copper foil after degreasing and roughening. The gap of the scraper controls the thickness of the wet film, ensuring uniform electrode surface density and adapting to the capacity matching of positive and negative electrodes during subsequent battery assembly.

[0019] 4. This invention breaks tin-carbon particles to the micron level through ball milling (using grinding balls of different particle sizes for grading and protection under an inert atmosphere), and then disperses them to the 100-500nm nanometer level through ultrasonic vibration, completely eliminating agglomeration. Through three high-temperature treatments and carbon skeleton anchoring, the carbon source is carbonized to form a three-dimensional porous network (such as porous carbon or carbon nanotubes), which "anchors" the tin particles through spatial confinement, preventing the tin particles from migrating and agglomerating at high temperatures.

[0020] 5. The present invention can ensure uniform particle size through screening, avoiding local stress concentration caused by the expansion of large particles, which may lead to electrode breakage. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Please refer to the embodiments of the present invention for a method for preparing a lithium-ion battery tin-carbon anode material, which includes the following steps: S1: Select high-purity tin powder and carbon source materials, and process the raw materials; S2: Mix the tin source and carbon source in a certain proportion, and promote the uniform dispersion of the two by methods such as ball milling and ultrasonic vibration. S3: The mixture is subjected to high-temperature heat treatment to convert the carbon source into graphite or other carbon forms and to promote the combination of tin and carbon. S4: Further process the carbonized material; S5: The heat-treated composite material is crushed and screened to obtain the required particle size. Then, it is mixed with binders, conductive additives, etc. as needed to prepare an electrode slurry. S6: The electrode paste is coated onto copper or aluminum foil, and the electrode is formed by processes such as coating, scraping, and rolling. Then, it is dried and compacted to obtain the final electrode. S7: Assemble the prepared negative electrode material together with other battery components (such as positive electrode, separator, electrolyte) into a complete lithium battery.

[0023] Specifically, in this invention, the carbon source material in S1 is graphite, carbon black, carbon nanotubes, graphene, etc., and the raw material processing involves two steps: washing and drying. The tin powder is ultrasonically cleaned using organic solvents such as ethanol and acetone. After cleaning, the tin powder is rinsed with deionized water to remove any residual organic solvents. The drying temperature of tin powder can be controlled at 80-120℃, and the drying time is 2-4 hours.

[0024] It should be noted that ultrasonic cleaning of tin powder using organic solvents (such as ethanol, acetone, etc.) aims to remove impurities that may be attached to the surface of the tin powder, so as to avoid these impurities affecting subsequent reactions or material properties. Ultrasonic cleaning can ensure that the solvent penetrates into the spaces between the tin powder particles and effectively cleans the surface. After cleaning, the tin powder needs to be rinsed with deionized water to thoroughly remove any residual organic solvents (such as ethanol, acetone, etc.). This step is crucial because residual solvents can negatively impact subsequent material properties and battery performance. The drying temperature of tin powder should be controlled between 80-120℃. This temperature range can ensure that the tin powder can fully remove moisture and solvents without causing unnecessary chemical changes. Excessively high drying temperature may cause oxidation of tin powder or other adverse reactions. Controlling the drying time to between 2 and 4 hours ensures complete drying of the tin powder. If the drying time is too short, moisture or solvent may remain, affecting subsequent mixing and reaction processes; while if the time is too long, it may cause changes in the physical properties of the tin powder, affecting the performance of the material.

[0025] Specifically, in this invention, a conductive agent is added to S2. The conductive agent is carbon nanotubes or graphene, and the mass ratio of tin to carbon in the tin source and carbon source is 1:1 to 1:5.

[0026] In S2, a planetary ball mill or a stirred ball mill is used for ball milling. When the initial particle size is large, 5-10 mm grinding balls are selected, and 1-3 mm grinding balls are selected in the fine-refining stage. The ball-to-material ratio is 5:1-15:1. The speed of the planetary ball mill is generally 200-400 rpm, and the speed of the stirred ball mill is 500-1000 rpm. The ball milling time is usually 2-8 hours. During the ball milling process, a nitrogen or argon inert atmosphere needs to be introduced to prevent the tin powder from oxidizing upon contact with air and forming tin oxide.

[0027] In S2, the ultrasonic vibration equipment used is an ultrasonic cell disruptor equipped with a titanium alloy ultrasonic probe. In S2, the initial particles of tin source and carbon source are first broken down to the micron level (1-10 μm) by ball milling to achieve preliminary mixing. The micron-sized particles are then dispersed to the nanoscale (100-500 nm) using ultrasonic vibration, and agglomeration is further eliminated, ultimately obtaining a tin-carbon mixture with uniform particle size and thorough mixing.

[0028] It should be noted that the tin source and carbon source are mixed in a certain proportion, with the mass ratio of tin to carbon being 1:1 to 1:5. In this step, ball milling and ultrasonic vibration help to promote the uniform dispersion of the two, so as to ensure the uniformity and stability of the mixture. To improve electrical conductivity, conductive agents are added to the mixture. Common conductive agents are carbon nanotubes or graphene. The addition of conductive agents can further improve battery performance, especially charge and discharge efficiency. Ball milling process: Ball milling equipment: Use a planetary ball mill or a stirred ball mill.

[0029] Grinding ball selection: Use 5-10 mm grinding balls in the initial stage when the particle size is large; use 1-3 mm grinding balls in the refining stage.

[0030] Ball-to-material ratio: The ratio of balls to materials during ball milling is generally between 5:1 and 15:1.

[0031] Ball mill speed: The speed of planetary ball mill is 200-400 rpm, and the speed of stirred ball mill is 500-1000 rpm.

[0032] Ball milling time: The ball milling time is usually set to 2-8 hours.

[0033] Atmosphere control: Nitrogen or argon inert atmosphere is introduced during ball milling to prevent tin powder from oxidizing and forming tin oxide after contact with air.

[0034] Ultrasonic vibration treatment: Equipment selection: Use an ultrasonic cell disruptor equipped with a titanium alloy ultrasonic probe.

[0035] After initial mixing, ball milling breaks the initial particles of the tin and carbon sources down to the micron level (1-10 μm), achieving initial mixing.

[0036] Refining and dispersing: Through ultrasonic vibration, the micron-sized particles are further refined to the nanoscale (100-500 nm), eliminating particle agglomeration and thus obtaining a tin-carbon mixture with uniform particle size and good dispersion.

[0037] Specifically, in this invention, the carbon source in S3 undergoes three high-temperature heating treatments. First high-temperature treatment: Under the protection of inert gas (argon, nitrogen, etc.), the temperature is increased to 250-500℃ at a rate of 3-10℃ / min, stirred and kept at the temperature for 2-8 hours, the tin material melts into liquid and penetrates into the pores of the carbon material, and after cooling, the second mixed material is obtained. Second high-temperature treatment: The second mixed material is mixed with graphite at a mass ratio of (1-10):100, and heated to 400-700℃ at a rate of 3-10℃ / min under inert gas protection, and held at this temperature for 2-7 hours, so that the second mixed material forms a uniform composite layer on the graphite surface, thus obtaining the initial negative electrode material. The third high-temperature treatment: the carbon source material and the initial anode material are mixed at a mass ratio of (3-8):100, and heated to 700-1000℃ at 3-10℃ / min under inert gas protection, and held for 6-10 hours. The carbon source material (such as resin, organic carbon precursor) is converted into amorphous carbon or graphite-like carbon, forming a carbonization layer on the surface of the composite layer, and finally obtaining the tin-carbon anode material. In S3, tin powder is heated to 500-1200℃ at a rate of 2-20℃ / min in a protective atmosphere (argon, nitrogen, or argon-hydrogen mixture) and held for 0.5-8 hours. Tin-containing compounds are pyrolyzed to generate elemental tin or tin-based compounds. At the same time, organic ligands are converted into amorphous carbon, and tin species combine with carbon in situ to form tin-carbon composite materials. After cooling, the sample was washed with deionized water at 20–90°C to remove impurities and obtain a tin-carbon composite intermediate. The three-dimensional network framework (such as porous carbon, carbon nanotubes, and graphene) formed during the carbonization process of the carbon source can "anchor" tin particles through spatial confinement.

[0038] It should be noted that this process uses a gel network to fix the tin source and low-temperature carbonization to achieve tin coating on a carbon skeleton. The process is as follows: Gel preparation: Dissolve water-soluble tin source (tin tetrachloride, stannous chloride, etc.) in water, add acrylamide (carbon source), crosslinking agent (N,N'-methylenebisacrylamide) and initiator, and crosslink at 40-80℃ for 0.5-4 hours to form a tin-containing three-dimensional network gel; Drying and carbonization: After the gel is dried at -50 to 80°C for 4 to 30 hours, it is carbonized at 200 to 400°C for 1 to 4 hours in an atmospheric environment. Acrylamide carbonization forms a porous carbon framework (in-situ doping with nitrogen atoms), and the tin source is converted into tin dioxide nanoparticles (particle size <10nm) and embedded in the carbon framework to achieve a tight bond between tin and carbon. Post-processing: The carbonized products are ball-milled (ball-to-material ratio 5-20:1, speed 200-400 rpm, time 4-12 hours) and cleaned (with deionized water or ethanol) to obtain a porous carbon framework coated with tin anode material.

[0039] Carbon source conversion and structural regulation: Organic carbon sources (such as acrylamide, resins, and organic ligands) undergo devolatileization, aromatization, and graphitization transformations at high temperatures, forming amorphous carbon (500–800℃), graphite-like carbon (800–1000℃), or graphite carbon (above 1000℃) depending on the temperature. The structure of carbon materials (specific surface area, porosity, degree of graphitization) directly affects the dispersion of tin species and the conductivity of the material: a high specific surface area carbon skeleton can accommodate the volume expansion of tin, and graphite-like carbon or graphite carbon can improve electron transport efficiency.

[0040] Strengthening effect of tin-carbon bonding: At high temperatures, tin materials (or tin source decomposition products) melt into a liquid state, seep into the pores or surface defects of carbon materials, and form a physical coating or embedding structure after cooling, thus inhibiting the agglomeration of tin particles. In some processes, high temperatures promote the interfacial reaction between tin and carbon, forming weak chemical bonds (such as Sn-C bonds), which further enhances the bonding strength of the tin-carbon interface and reduces tin shedding during charging and discharging.

[0041] Performance optimization results: Carbon matrix (especially graphitized carbon) reduces material resistance and improves electrical conductivity; The carbon skeleton or carbide layer buffers the volume expansion of tin during charge and discharge (the volume expansion rate is about 300% when tin is intercalated with lithium), preventing electrode pulverization and improving cycle stability. High-temperature treatment removes impurities (such as moisture and volatile organic compounds) from the precursor, improving material purity and optimizing electrochemical performance.

[0042] III. Control of Key Process Parameters

[0043] Specifically, the steps in S4 of this invention are as follows: S41: Take the tin-carbon composite material after S3 carbonization, add 5% hydrochloric acid solution, stir at 80℃ for 2 hours to remove surface SnO2. S42: Rinse with deionized water until pH=7, then soak in anhydrous ethanol for 1 hour and separate by filtration; S43: Place the material in a vacuum drying oven and dry it at 80°C for 6 hours to obtain a dried tin-carbon intermediate; S44: The intermediate is mixed with a 10% sucrose solution (mass ratio 10:1), ultrasonically dispersed for 30 minutes, and then heat-treated at 400℃ for 2 hours under an Ar atmosphere to form a secondary carbon coating layer.

[0044] S45: Remove after cooling.

[0045] It should be noted that for acidic / alkaline impurities: use dilute acid (such as 1% to 5% hydrochloric acid or sulfuric acid) or dilute alkali (such as 0.5% to 2% sodium hydroxide solution) to soak the material to remove the metal oxides (such as SnO2) or soluble salts attached to the surface.

[0046] For organic residues: Rinse repeatedly with deionized water or anhydrous ethanol (with heating at room temperature or 50-80°C) until the pH of the cleaning solution is neutral, and then separate the solid and liquid by filtration or centrifugation.

[0047] Function: To prevent impurities from affecting the bonding of tin and carbon interfaces and to reduce the stability of the slurry during electrode preparation.

[0048] If stubborn organic impurities remain after chemical cleaning, a low-temperature secondary heat treatment (200-400℃, held for 1-3 hours) can be performed under an inert atmosphere (Ar, N2) to remove the residual organic matter through pyrolysis.

[0049] Note: The temperature must be lower than the initial carbonization temperature to prevent excessive graphitization of the carbon material structure or agglomeration of tin particles.

[0050] If the porosity of the carbon material is too low (which is not conducive to electrolyte wetting and buffering the volume expansion of tin), the "etching method" can be used: the material is immersed in an etchant (such as KOH, H2O2) and reacted at 60-100℃ for 1-4 hours to create new pores on the carbon framework through chemical etching, followed by cleaning and drying.

[0051] If the pores are too large (resulting in insufficient specific surface area and decreased conductivity of the material), the pores can be slightly reduced by "low-temperature sintering" (500-600℃, inert atmosphere, heat preservation for 2 hours) to balance porosity and structural stability.

[0052] If the tin particles are exposed on the surface of the carbon material after carbonization (which is easily oxidized or falls off during charging and discharging), a "secondary carbon coating" can be performed: mix the material with a small amount of carbon source precursor (such as phenolic resin or sucrose solution), and heat-treat at 300-500℃ for 1-2 hours in an inert atmosphere to form a thin layer of amorphous carbon on the surface of the tin particles, thereby strengthening the tin-carbon bond.

[0053] Alternatively, "metal oxide coating" (such as Al2O3, TiO2) can be used: a nanoscale coating layer is formed on the material surface through the sol-gel method to improve the material's cycle stability (suppress the side reaction between the electrolyte and tin).

[0054] Specifically, in S5 of this invention, coarse crushing and fine crushing are used. The coarse crushing uses a jaw crusher with the gap adjusted to 1-5mm and a high-speed shear with a speed of 1000-3000rpm. The fine crushing uses a planetary ball mill with a speed of 200-400rpm and a crushing time of 2-6 hours. After crushing, the particles are graded and screened using a vibrating screen. A 300 mesh inset screen (to remove coarse particles >53um) + an 800 mesh main screen (to retain fine powder <18um) are selected. A small amount of inert gas can be introduced during screening. The electrode paste employs a three-stage process. First stage: Put the tin-carbon composite material and conductive additive into a double planetary mixer and stir at low speed (50-100 rpm) for 10-20 minutes to make the solid particles initially mixed evenly and form a dry powder mixture. Second stage: Add the adhesive to the solvent and stir with a high-speed disperser (2000-3000 rpm) for 30-60 minutes until the adhesive is completely dissolved and a transparent adhesive solution is formed; Slowly add the dry powder mixture to the adhesive solution (stirring while adding to prevent local agglomeration), and then use a double planetary mixer to alternate between "low-speed stirring + high-speed dispersion": first stir at low speed (100-200 rpm) for 30 minutes, and then disperse at high speed (500-800 rpm) for 1-2 hours. During this period, you can pause 1-2 times and scrape off the material remaining on the container wall with a scraper to ensure thorough mixing. Third stage: After dispersion is completed, the viscosity of the slurry is measured with a rotational viscometer. The target range is usually 5000 to 20000 mPa·s. If the viscosity is too high, add a small amount of solvent (NMP or water); if the viscosity is too low, evaporate a small amount of solvent while stirring at low speed (e.g., by heating at 60-80°C). Finally, filter the slurry with a 120-200 mesh filter to remove undispersed small agglomerates and ensure that the slurry is free of impurities.

[0055] Specifically, in S6, an electrolytic copper foil with a thickness of 8-12 μm is first selected, and the aluminum foil is ultrasonically cleaned with anhydrous ethanol or isopropanol to remove surface oil stains. After cleaning, it is vacuum dried at 60-80°C for 30 minutes. The coating is applied using a manual coating machine with a doctor blade (gap 50-200μm) at a uniform speed of 5-15cm / s to form a wet film. The wet film drying process employs a gradual increase in low, medium, and high temperatures to achieve the desired drying effect. Compaction is performed using a roller press with a pressure of 5–20 MPa.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a tin-carbon anode material for lithium batteries, characterized in that, Includes the following steps, S1: Select high-purity tin powder and carbon source materials, and process the raw materials; S2: Mix the tin source and carbon source in a certain proportion, and promote the uniform dispersion of the two by methods such as ball milling and ultrasonic vibration. S3: The mixture is subjected to high-temperature heat treatment to convert the carbon source into graphite or other carbon forms and to promote the combination of tin and carbon. S4: Further process the carbonized material; S5: The heat-treated composite material is crushed and screened to obtain the required particle size. Then, it is mixed with binders, conductive additives, etc. as needed to prepare an electrode slurry. S6: The electrode paste is coated onto copper or aluminum foil, and the electrode is formed by processes such as coating, scraping, and rolling. Then, it is dried and compacted to obtain the final electrode. S7: Assemble the prepared negative electrode material together with other battery components (such as positive electrode, separator, electrolyte) into a complete lithium battery.

2. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, The carbon source material in S1 is graphite, carbon black, carbon nanotubes, graphene, etc., and the raw material processing involves two steps: washing and drying. The cleaning process involves using organic solvents such as ethanol and acetone to ultrasonically clean the tin powder. After cleaning, the tin powder is rinsed with deionized water to remove any residual organic solvents. The drying temperature of the tin powder can be controlled at 80-120℃, and the drying time is 2-4 hours.

3. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, The conductive agent is added to S2, which is carbon nanotubes or graphene, and the mass ratio of tin to carbon in the tin source and carbon source is 1:1 to 1:

5.

4. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, In step S2, a planetary ball mill or a stirred ball mill is used for ball milling. When the initial particle size is large, 5-10 mm grinding balls are selected, and 1-3 mm grinding balls are selected in the refining stage. The ball-to-material ratio is 5:1-15:

1. The rotation speed of the planetary ball mill is generally 200-400 rpm, and the rotation speed of the stirred ball mill is 500-1000 rpm. The ball milling time is usually 2-8 hours. During the ball milling process, a nitrogen or argon inert atmosphere is required to prevent the tin powder from oxidizing upon contact with air and forming tin oxide.

5. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, The ultrasonic vibration in S2 is performed using an ultrasonic cell disruptor equipped with a titanium alloy ultrasonic probe. In S2, the initial particles of the tin source and carbon source are first broken down to the micron level (1-10 μm) by ball milling to achieve preliminary mixing. The micron-sized particles are then dispersed to the nanoscale (100-500 nm) using ultrasonic vibration, and agglomeration is further eliminated, ultimately obtaining a tin-carbon mixture with uniform particle size and thorough mixing.

6. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, The carbon source in S3 undergoes three high-temperature heating treatments. First high-temperature treatment: Under the protection of inert gas (argon, nitrogen, etc.), the temperature is increased to 250-500℃ at a rate of 3-10℃ / min, stirred and kept at the temperature for 2-8 hours, the tin material melts into liquid and penetrates into the pores of the carbon material, and after cooling, the second mixed material is obtained. Second high-temperature treatment: The second mixed material is mixed with graphite at a mass ratio of (1-10):100, and heated to 400-700℃ at a rate of 3-10℃ / min under inert gas protection, and held at this temperature for 2-7 hours, so that the second mixed material forms a uniform composite layer on the graphite surface, thus obtaining the initial negative electrode material. The third high-temperature treatment: the carbon source material and the initial anode material are mixed at a mass ratio of (3-8):100, and heated to 700-1000℃ at 3-10℃ / min under inert gas protection, and held for 6-10 hours. The carbon source material (such as resin, organic carbon precursor) is converted into amorphous carbon or graphite-like carbon, forming a carbonization layer on the surface of the composite layer, and finally obtaining the tin-carbon anode material. In the S3 process, tin powder is heated to 500-1200°C at a rate of 2-20°C / min in a protective atmosphere (argon, nitrogen, or argon-hydrogen mixture) and held for 0.5-8 hours. Tin-containing compounds are pyrolyzed to generate elemental tin or tin-based compounds, while organic ligands are converted into amorphous carbon. Tin species combine with carbon in situ to form tin-carbon composite materials. After cooling, the sample was washed with deionized water at 20–90°C to remove impurities and obtain a tin-carbon composite intermediate. The three-dimensional network framework (such as porous carbon, carbon nanotubes, and graphene) formed during the carbonization process of the carbon source can "anchor" tin particles through spatial confinement.

7. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, The specific steps in S4 are as follows: S41: Take the tin-carbon composite material after S3 carbonization, add 5% hydrochloric acid solution, stir at 80℃ for 2 hours to remove surface SnO2. S42: Rinse with deionized water until pH=7, then soak in anhydrous ethanol for 1 hour and separate by filtration; S43: Place the material in a vacuum drying oven and dry it at 80°C for 6 hours to obtain a dried tin-carbon intermediate; S44: The intermediate is mixed with a 10% sucrose solution (mass ratio 10:1), ultrasonically dispersed for 30 minutes, and then heat-treated at 400℃ for 2 hours under an Ar atmosphere to form a secondary carbon coating layer. S45: Remove after cooling.

8. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, In the S5 process, coarse crushing and fine crushing are used. The coarse crushing uses a jaw crusher with the gap adjusted to 1-5mm and a high-speed shear with a speed of 1000-3000rpm. The fine crushing uses a planetary ball mill with a speed of 200-400rpm and a crushing time of 2-6 hours. After pulverization, the material is graded and screened using a vibrating screen. A 300 mesh inset screen (to remove coarse particles >53µm) and an 800 mesh main screen (to retain fine powder <18µm) are selected. A small amount of inert gas can be introduced during screening. The electrode slurry employs three stages. First stage: Put the tin-carbon composite material and conductive additive into a double planetary mixer and stir at low speed (50-100 rpm) for 10-20 minutes to make the solid particles initially mixed evenly and form a dry powder mixture. Second stage: Add the adhesive to the solvent and stir with a high-speed disperser (2000-3000 rpm) for 30-60 minutes until the adhesive is completely dissolved and a transparent adhesive solution is formed; Slowly add the dry powder mixture to the adhesive solution (stirring while adding to prevent local agglomeration), and then use a double planetary mixer to alternate between "low-speed stirring + high-speed dispersion": first stir at low speed (100-200 rpm) for 30 minutes, and then disperse at high speed (500-800 rpm) for 1-2 hours. During this period, you can pause 1-2 times and scrape off the material remaining on the container wall with a scraper to ensure thorough mixing. Third stage: After dispersion is completed, the viscosity of the slurry is measured with a rotational viscometer. The target range is usually 5000 to 20000 mPa·s. If the viscosity is too high, add a small amount of solvent (NMP or water); if the viscosity is too low, evaporate a small amount of solvent while stirring at low speed (e.g., by heating at 60-80°C). Finally, filter the slurry with a 120-200 mesh filter to remove undispersed small agglomerates and ensure that the slurry is free of impurities.

9. The method for preparing a lithium-ion battery tin-carbon anode material according to claim 1, characterized in that, In step S6, an electrolytic copper foil with a thickness of 8-12 μm is first selected, and the aluminum foil is ultrasonically cleaned with anhydrous ethanol or isopropanol to remove surface oil. After cleaning, it is vacuum dried at 60-80°C for 30 minutes. The coating is applied by using a manual coating machine with a doctor blade (gap 50-200μm) at a speed of 5-15cm / s to form a wet film. The wet film drying process employs a progressive increase of low temperature, medium temperature, and high temperature to achieve the drying effect. The compaction is performed using a roller press with a pressure of 5 to 20 MPa.

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