Silicon-carbon negative electrode material and preparation method thereof

Abstract

The application discloses a silicon-carbon negative electrode material and a preparation method thereof in the technical field of negative electrode materials, and comprises the following components in parts by weight: modified nano-silicon dioxide 35-46 parts, nano-carbon tube 12-15 parts, polyvinyl fluoride 5-9 parts and 1-methyl-2-pyrrolidone 3-5 parts. The application realizes uniform wrapping of the organic coating agent by modifying the nano-silicon dioxide, and realizes the technical effect of double-shell layer coating by using the nano-carbon tube and the polyvinyl fluoride for secondary coating and preparing a second shell layer by pyrolysis, so that the volume expansion of silicon is reduced, and the high-temperature performance and cycle life of the electrode material are improved.

Description

Technical Field

[0001] This invention belongs to the field of anode material technology, specifically referring to a silicon-carbon anode material and its preparation method. Background Technology

[0002] Silicon-carbon anode materials, through the composite of nano-silicon and carbon matrix, combine the ultra-high specific capacity of silicon with the conductivity buffering advantages of carbon, significantly improving the energy density and fast-charging performance of lithium-ion batteries. They are key materials for overcoming existing technological bottlenecks. Silicon-carbon composite materials, due to their low expansion rate and long cycle life, have become the mainstream of current research. The development of the electric vehicle industry inevitably relies on high-performance lithium-ion batteries, thus posing greater challenges to electrode materials with high energy density and power density. Silicon, as the anode material with the greatest commercial application potential, bears the heavy responsibility of improving the overall performance of lithium-ion batteries. However, the industrial application of silicon anode materials is still limited by many factors, the biggest of which is the volume expansion of silicon. The severe volume expansion of silicon leads to insufficient cycle life, which needs to be addressed through nano-sizing, porous carbon coating, and pre-lithiation processes. Coated silicon-carbon anode materials often involve carbon coating silicon materials with different nanostructures. These materials use silicon as the main body to provide reversible capacity, while the carbon layer mainly acts as a buffer layer to reduce the volume effect and enhance conductivity. The carbon coating is usually amorphous carbon, and the preparation methods include thermal decomposition, vapor deposition, ball milling, sol-gel method and other methods.

[0003] The existing technology currently suffers from the following problems: the volume expansion of silicon leads to poor high-temperature performance of electrode materials and insufficient cycle life. Summary of the Invention

[0004] In response to the above situation and to overcome the shortcomings of the prior art, this invention provides a silicon-carbon anode material and its preparation method. To solve the problem of poor high-temperature performance and insufficient cycle life of electrode materials caused by the volume expansion of silicon, this invention proposes to achieve uniform encapsulation of organic coating agents by modifying silicon dioxide, and to perform secondary encapsulation with carbon nanotubes and polyvinyl fluoride, and to prepare a second shell layer by pyrolysis, thereby achieving the technical effect of double-shell encapsulation, reducing the volume expansion of silicon, and thus improving the high-temperature performance and cycle life of the electrode material.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention proposes a silicon-carbon anode material, which comprises the following components in parts by weight: 35-46 parts of modified nano-silica, 12-15 parts of carbon nanotubes, 5-9 parts of polyvinyl fluoride, and 3-5 parts of 1-methyl-2-pyrrolidone.

[0006] Preferably, the modified nano-silica is prepared with the following weight components: 40-60 parts of ethyl silicate, 100-150 parts of γ-methacryloyloxypropyltrimethoxysilane, 2-3 parts of ammonium persulfate, 10-15 parts of n-butyl methacrylate and 8-12 parts of methyl methacrylate.

[0007] Preferably, the preparation method of the modified nano-silica specifically includes the following steps:

[0008] (1) Dissolve 4-6g of ethyl silicate in 25mL of anhydrous ethanol, add concentrated ammonia and deionized water, mix well and heat in a water bath at 55℃ for 6h to obtain silica sol solution, add 10-15g of γ-methacryloxypropyltrimethoxysilane and 25mL of anhydrous ethanol mixture, heat in a water bath at 40℃ for 5h, adjust pH to 7 with 2mol / L hydrochloric acid solution, centrifuge, wash and dry to obtain double bond nano silica;

[0009] (2) Disperse the double-bonded nano silica obtained in step (1) in 100 mL of deionized water, add 0.2-0.3 g of ammonium persulfate, 1-1.5 g of n-butyl methacrylate and 0.8-1.2 g of methyl methacrylate under nitrogen protection, heat in a water bath at 55 °C for 2 h, centrifuge, wash and dry to obtain modified nano silica.

[0010] This invention also provides a method for preparing a silicon-carbon anode material, specifically including the following steps:

[0011] S1. Mix 50wt% ethanol solution with poloxamer 127 and poloxamer 123 evenly, add modified nano silica at an addition amount of 10-12 mg / mL, add dopamine hydrochloride at an addition amount of 13-16 mg / mL, and disperse by ultrasonication to obtain a mixture.

[0012] S2. The mixture obtained in S1 is mixed with 3,3',5,5'-tetramethylbenzidine and ammonia, magnetically stirred for 30 min, centrifuged, washed three times with anhydrous ethanol, and vacuum dried to obtain organic-coated nanoparticles.

[0013] S3. The organic-coated nanoparticles obtained in S2 are added to a tube furnace. Under argon protection, the temperature is increased once at an initial temperature of 30℃ and a rate of 2℃ / min. After holding at this temperature for 40-60 min, the temperature is increased a second time at a rate of 5℃ / min. The mixture is then cooled to room temperature to obtain the SiO2 / void / C composite material.

[0014] S4. The SiO2 / void / C composite material obtained in S3, carbon nanotubes and polyvinyl fluoride are mixed evenly, and pyrolyzed at 500℃ for 2 hours under argon protection. 1-methyl-2-pyrrolidone is added and ground into a slurry, which is then coated onto a carbon cloth current collector and vacuum dried at room temperature for 10 hours to obtain SiO2 / void / C / void / C, i.e., silicon-carbon anode material.

[0015] Preferably, in S1, the volume ratio of the 50wt% ethanol solution to poloxamer 127 and poloxamer 123 is 1-1.2:0.08:0.03.

[0016] Preferably, in S2, the volume ratio of the mixture obtained in S1 to 3,3',5,5'-tetramethylbenzidine and ammonia is 1-1.2:0.08:0.1.

[0017] Preferably, in S3, the first heating temperature is 350-400℃; the second heating temperature is 650-700℃.

[0018] Preferably, in S4, the amount of slurry applied to the carbon cloth current collector is 10-12 mg / cm³. 2 .

[0019] The beneficial effects of this invention are as follows: This invention prepares nano-silica using ethyl silicate, and modifies the nano-silica with γ-methacryloxypropyltrimethoxysilane to obtain nano-silica with double bonds on the surface. n-Butyl methacrylate and methyl methacrylate are used as template agents to coat the nano-silica with double bonds. Surface double bond modification ensures that the template agent is uniformly coated on the surface of the nano-silica, resulting in modified nano-silica. Poloxamer 127 and poloxamer 123 are used as secondary templates, and dopamine hydrochloride is used as a precursor for organic coating. A first pyrolysis is performed under argon protection to form a SiO2 / void / C composite material with a large cavity, consisting of a silica core and a nitrogen-doped porous carbon shell. Finally, a second coating is performed with carbon nanotubes and fluoropolyethylene. Pyrolysis is then performed on the surface of the composite material to prepare a second shell layer, further controlling volume expansion and improving the high-temperature performance and cycle life of the electrode material. Attached Figure Description

[0020] Figure 1 The graphs show the cycle performance test results of Examples 1-3 and Comparative Examples 1-2 of the present invention.

[0021] Figure 2 The figures show the high-temperature performance test results of Examples 1-3 and Comparative Examples 1-2 of the present invention;

[0022] Figure 3 The graphs show the performance test results of Examples 1-3 and Comparative Examples 1-2 of this invention at various rate ranges.

[0023] Figure 4 This is an electron microscope image of the modified nano-silica prepared in Example 1 of the present invention.

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0027] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0028] Example 1

[0029] A silicon-carbon anode material comprises the following components in parts by weight: 35 parts modified nano-silica, 12 parts carbon nanotubes, 5 parts polyvinyl fluoride, and 3 parts 1-methyl-2-pyrrolidone.

[0030] Modified nano-silica was prepared with the following weight components: 40 parts of ethyl silicate, 100 parts of γ-methacryloyloxypropyltrimethoxysilane, 2 parts of ammonium persulfate, 10 parts of n-butyl methacrylate and 8 parts of methyl methacrylate.

[0031] The preparation method of modified nano-silica specifically includes the following steps:

[0032] (1) Dissolve 4g of ethyl silicate in 25mL of anhydrous ethanol, add concentrated ammonia and deionized water, mix well and heat in a water bath at 55℃ for 6h to obtain silica sol solution, add 10g of γ-methacryloxypropyltrimethoxysilane and 25mL of anhydrous ethanol mixture, heat in a water bath at 40℃ for 5h, adjust the pH to 7 with 2mol / L hydrochloric acid solution, centrifuge, wash and dry to obtain double bond nano silica;

[0033] (2) Disperse the double-bonded nano silica obtained in step (1) in 100 mL of deionized water, add 0.2 g of ammonium persulfate, 1 g of n-butyl methacrylate and 0.8 g of methyl methacrylate under nitrogen protection, heat in a water bath at 55 °C for 2 h, centrifuge, wash and dry to obtain modified nano silica.

[0034] This invention also provides a method for preparing a silicon-carbon anode material, specifically including the following steps:

[0035] S1. Mix 50wt% ethanol solution with poloxamer 127 and poloxamer 123 at a volume ratio of 1:0.08:0.03 until homogeneous. Add modified nano-silica at an addition amount of 10mg / mL and dopamine hydrochloride at an addition amount of 13mg / mL. Disperse by ultrasonication to obtain a mixture.

[0036] S2. The mixture obtained in S1 is mixed with 3,3',5,5'-tetramethylbenzidine and ammonia water at a volume ratio of 1:0.08:0.1, magnetically stirred for 30 min, centrifuged, washed three times with anhydrous ethanol, and vacuum dried to obtain organic-coated nanoparticles.

[0037] S3. The organic-coated nanoparticles obtained in S2 are added to a tube furnace. Under argon protection, the temperature is increased to 350°C at an initial temperature of 30°C and a rate of 2°C / min. After holding at this temperature for 40 min, the temperature is increased to 650°C at a rate of 5°C / min. The mixture is then cooled to room temperature to obtain the SiO2 / void / C composite material.

[0038] S4. The SiO2 / void / C composite material obtained in S3, carbon nanotubes, and polyvinyl fluoride are mixed evenly and pyrolyzed at 500℃ for 2 hours under argon protection. 1-Methyl-2-pyrrolidone is then added and ground into a slurry at 10 mg / cm³. 2 The coating was applied to a carbon cloth current collector and dried under vacuum at room temperature for 10 hours to obtain SiO2 / void / C / void / C, which is the silicon-carbon anode material.

[0039] Example 2

[0040] A silicon-carbon anode material comprises the following components in parts by weight: 46 parts modified nano-silica, 15 parts carbon nanotubes, 9 parts polyvinyl fluoride, and 5 parts 1-methyl-2-pyrrolidone.

[0041] Modified nano-silica was prepared with the following weight components: 60 parts of ethyl silicate, 150 parts of γ-methacryloyloxypropyltrimethoxysilane, 3 parts of ammonium persulfate, 15 parts of n-butyl methacrylate and 12 parts of methyl methacrylate.

[0042] The preparation method of modified nano-silica specifically includes the following steps:

[0043] (1) Dissolve 4-6g of ethyl silicate in 25mL of anhydrous ethanol, add concentrated ammonia and deionized water, mix well and heat in a water bath at 55℃ for 6h to obtain silica sol solution, add 10-15g of γ-methacryloxypropyltrimethoxysilane and 25mL of anhydrous ethanol mixture, heat in a water bath at 40℃ for 5h, adjust pH to 7 with 2mol / L hydrochloric acid solution, centrifuge, wash and dry to obtain double bond nano silica;

[0044] (2) Disperse the double-bonded nano silica obtained in step (1) in 100 mL of deionized water, add 0.3 g of ammonium persulfate, 1.5 g of n-butyl methacrylate and 1.2 g of methyl methacrylate under nitrogen protection, heat in a water bath at 55 °C for 2 h, centrifuge, wash and dry to obtain modified nano silica.

[0045] This invention also provides a method for preparing a silicon-carbon anode material, specifically including the following steps:

[0046] S1. Mix 50wt% ethanol solution with poloxamer 127 and poloxamer 123 at a volume ratio of 1.2:0.08:0.03 until homogeneous. Add modified nano-silica at an addition amount of 12mg / mL and dopamine hydrochloride at an addition amount of 16mg / mL. Disperse by ultrasonication to obtain a mixture.

[0047] S2. The mixture obtained in S1 is mixed with 3,3',5,5'-tetramethylbenzidine and ammonia water at a volume ratio of 1.2:0.08:0.1, magnetically stirred for 30 min, centrifuged, washed three times with anhydrous ethanol, and vacuum dried to obtain organic-coated nanoparticles.

[0048] S3. The organic-coated nanoparticles obtained in S2 are added to a tube furnace. Under argon protection, the temperature is increased to 400°C at an initial temperature of 30°C and a rate of 2°C / min. After holding at this temperature for 60 min, the temperature is increased to 700°C at a rate of 5°C / min. The mixture is then cooled to room temperature to obtain the SiO2 / void / C composite material.

[0049] S4. The SiO2 / void / C composite material obtained in S3, carbon nanotubes, and polyvinyl fluoride are mixed evenly and pyrolyzed at 500℃ for 2 hours under argon protection. 1-Methyl-2-pyrrolidone is then added and ground into a slurry at 12 mg / cm³. 2 The coating was applied to a carbon cloth current collector and dried under vacuum at room temperature for 10 hours to obtain SiO2 / void / C / void / C, which is the silicon-carbon anode material.

[0050] Example 3

[0051] A silicon-carbon anode material comprises the following components in parts by weight: 40 parts modified nano-silica, 13 parts carbon nanotubes, 7 parts polyvinyl fluoride, and 4 parts 1-methyl-2-pyrrolidone.

[0052] Modified nano-silica was prepared with the following weight components: 50 parts of ethyl silicate, 125 parts of γ-methacryloyloxypropyltrimethoxysilane, 2.5 parts of ammonium persulfate, 12.5 parts of n-butyl methacrylate and 10 parts of methyl methacrylate.

[0053] The preparation method of modified nano-silica specifically includes the following steps:

[0054] (1) Dissolve 5g of ethyl silicate in 25mL of anhydrous ethanol, add concentrated ammonia and deionized water, mix well and heat in a water bath at 55℃ for 6h to obtain silica sol solution, add 12.5g of γ-methacryloxypropyltrimethoxysilane and 25mL of anhydrous ethanol mixture, heat in a water bath at 40℃ for 5h, adjust the pH to 7 with 2mol / L hydrochloric acid solution, centrifuge, wash and dry to obtain double bond nano silica;

[0055] (2) Disperse the double-bonded nano silica obtained in step (1) in 100 mL of deionized water, add 0.25 g of ammonium persulfate, 1.25 g of n-butyl methacrylate and 1 g of methyl methacrylate under nitrogen protection, heat in a water bath at 55 °C for 2 h, centrifuge, wash and dry to obtain modified nano silica.

[0056] This invention also provides a method for preparing a silicon-carbon anode material, specifically including the following steps:

[0057] S1. Mix 50wt% ethanol solution with poloxamer 127 and poloxamer 123 at a volume ratio of 1.1:0.08:0.03 until homogeneous. Add modified nano-silica at an addition amount of 11mg / mL and dopamine hydrochloride at an addition amount of 15mg / mL. Disperse by ultrasonication to obtain a mixture.

[0058] S2. The mixture obtained in S1 is mixed with 3,3',5,5'-tetramethylbenzidine and ammonia water at a volume ratio of 1.1:0.08:0.1, magnetically stirred for 30 min, centrifuged, washed three times with anhydrous ethanol, and vacuum dried to obtain organic-coated nanoparticles.

[0059] S3. The organic-coated nanopowder obtained in S2 is added to a tube furnace. Under argon protection, the temperature is increased to 380°C at an initial temperature of 30°C and a rate of 2°C / min. After holding at this temperature for 50 min, the temperature is increased to 670°C at a rate of 5°C / min. The mixture is then cooled to room temperature to obtain the SiO2 / void / C composite material.

[0060] S4. The SiO2 / void / C composite material obtained in S3, carbon nanotubes, and fluoropolyethylene are mixed evenly and pyrolyzed at 500℃ for 2 hours under argon protection. 1-Methyl-2-pyrrolidone is then added and ground into a slurry at 11.5 mg / cm³. 2 The coating was applied to a carbon cloth current collector and dried under vacuum at room temperature for 10 hours to obtain SiO2 / void / C / void / C, which is the silicon-carbon anode material.

[0061] Comparative Example 1

[0062] This comparative example provides an electrode material that differs from Example 1 only in that the modified nano-silica in the composition is replaced with an equal amount of nano-silica, while the remaining components and their contents are the same as in Example 1.

[0063] Comparative Example 2

[0064] This comparative example provides an electrode material that differs from Example 1 only in that it does not contain dopamine hydrochloride; the other components and their contents are the same as in Example 1.

[0065] Experimental Example

[0066] 1. Cyclic performance testing

[0067] Cyclic performance tests were conducted on Examples 1-3 and Comparative Examples 1-2. Under room temperature conditions, the batteries were charged at a constant current and constant voltage of 1C to 3.65V, allowed to stand for 10 minutes, and then discharged at a constant current of 1C to 2.5V, allowed to stand for 10 minutes. This cycle was repeated until the battery completed 500 cycles. The battery capacity retention rate was calculated using the following formula:

[0068] Capacity retention rate = Battery capacity after 500 cycles / Initial battery capacity × 100%.

[0069] Figure 1 The figures show the cycle performance test results of Examples 1-3 and Comparative Examples 1-2 of the present invention. As shown in the figures, the capacity retention rates of Examples 1-3 were 97.1%, 96.9%, and 96.3%, respectively, while those of Comparative Examples 1-2 were 76.3% and 81.6%, respectively. The capacity retention rates of Examples 1-3 were significantly higher than those of Comparative Examples 1-2, indicating that Examples 1-3 had better cycle performance than Comparative Examples 1-2. The use of modified nano-silica and dopamine hydrochloride improved the capacity retention rate after cycling.

[0070] 2. High-temperature performance test

[0071] High-temperature performance tests were conducted on Examples 1-3 and Comparative Examples 1-2. Cyclic performance tests were performed under a constant temperature of 50°C to obtain the capacity retention rate at 50°C. The capacity retention rate reduction rate was calculated using the following formula:

[0072] Capacity retention rate decrease rate = (room temperature capacity retention rate - 50℃ capacity retention rate) / room temperature capacity retention rate × 100%.

[0073] Figure 2 The figures show the high-temperature performance test results of Examples 1-3 and Comparative Examples 1-2 of the present invention. As shown in the figures, the capacity retention rate decrease rates of Examples 1-3 were 8.1%, 7.3%, and 7.9%, respectively, while those of Comparative Examples 1-2 were 26.2% and 56.3%, respectively. The capacity retention rate decrease rate of Examples 1-3 was significantly lower than that of Comparative Examples 1-2, indicating that Examples 1-3 have better high-temperature resistance than Comparative Examples 1-2. The use of modified nano-silica and dopamine hydrochloride improved the discharge specific capacity retention rate.

[0074] 3. Ratio Performance Test

[0075] Rate performance tests were conducted on Examples 1-3 and Comparative Examples 1-2. At room temperature, the batteries were charged to the termination voltage at 1C, with a cutoff current of 0.05C. After standing for 30 minutes, they were discharged to the termination voltage at 1C and 2C respectively. The discharge specific capacity was recorded, and the 2C-to-1C discharge specific capacity retention rate was calculated using the following formula:

[0076] Discharge specific capacity retention rate = 2C discharge capacity / 1C discharge capacity × 100%.

[0077] Figure 3 The figures show the rate performance test results of Examples 1-3 and Comparative Examples 1-2 of the present invention. As shown in the figures, under room temperature conditions, the discharge specific capacity retention rates of Examples 1-3 were 96.1%, 96.8%, and 95.9%, respectively, while those of Comparative Examples 1-2 were 86.8% and 89.6%, respectively. The discharge specific capacity retention rates of Examples 1-3 were significantly higher than those of Comparative Examples 1-2, indicating that Examples 1-3 have better rate performance than Comparative Examples 1-2. The use of modified nano-silica and dopamine hydrochloride improved the discharge specific capacity retention rate.

[0078] Figure 4 The image shows an electron microscope image of the modified nano-silica prepared in Example 1 of this invention; as shown, the obtained nanomaterials are uniform in size and have good dispersibility.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0080] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A silicon-carbon anode material, characterized in that: The composition includes the following components in parts by weight: 35-46 parts modified nano-silica, 12-15 parts carbon nanotubes, 5-9 parts polyvinyl fluoride, and 3-5 parts 1-methyl-2-pyrrolidone. The modified nano-silica is prepared with the following weight components: 40-60 parts of ethyl silicate, 100-150 parts of γ-methacryloyloxypropyltrimethoxysilane, 2-3 parts of ammonium persulfate, 10-15 parts of n-butyl methacrylate and 8-12 parts of methyl methacrylate. The preparation method of the silicon-carbon anode material specifically includes the following steps: S1. Mix 50wt% ethanol solution with poloxamer 127 and poloxamer 123 evenly, add modified nano silica at an addition amount of 10-12 mg / mL, add dopamine hydrochloride at an addition amount of 13-16 mg / mL, and disperse by ultrasonication to obtain a mixture. S2. The mixture obtained in S1 is mixed with 3,3',5,5'-tetramethylbenzidine and ammonia, magnetically stirred for 30 min, centrifuged, washed three times with anhydrous ethanol, and vacuum dried to obtain organic-coated nanoparticles. S3. The organic-coated nanoparticles obtained in S2 are added to a tube furnace. Under argon protection, the temperature is increased once at an initial temperature of 30℃ and a rate of 2℃ / min. After holding at this temperature for 40-60 min, the temperature is increased a second time at a rate of 5℃ / min. The mixture is then cooled to room temperature to obtain the SiO2 / void / C composite material. S4. The SiO2 / void / C composite material obtained in S3, carbon nanotubes and polyvinyl fluoride are mixed evenly, pyrolyzed at 500℃ for 2h under argon protection, 1-methyl-2-pyrrolidone is added and ground into a slurry, which is then coated on a carbon cloth current collector and vacuum dried at room temperature for 10h to obtain SiO2 / void / C / void / C, i.e. silicon-carbon anode material. The preparation method of the modified nano-silica specifically includes the following steps: (1) Dissolve 4-6g of ethyl silicate in 25mL of anhydrous ethanol, add concentrated ammonia and deionized water, mix well and heat in a water bath at 55℃ for 6h to obtain silica sol solution, add 10-15g of γ-methacryloxypropyltrimethoxysilane and 25mL of anhydrous ethanol mixture, heat in a water bath at 40℃ for 5h, adjust pH to 7 with 2mol / L hydrochloric acid solution, centrifuge, wash and dry to obtain double bond nano silica; (2) Disperse the double-bonded nano silica obtained in step (1) in 100 mL of deionized water, add 0.2-0.3 g of ammonium persulfate, 1-1.5 g of n-butyl methacrylate and 0.8-1.2 g of methyl methacrylate under nitrogen protection, heat in a water bath at 55 °C for 2 h, centrifuge, wash and dry to obtain modified nano silica.

2. The silicon-carbon anode material according to claim 1, characterized in that: In S1, the volume ratio of a 50 wt% ethanol solution to poloxamer 127 and poloxamer 123 is 1-1.2:0.08:0.

03.

3. The silicon-carbon anode material according to claim 2, characterized in that: In S2, the volume ratio of the mixture obtained in S1 to 3,3',5,5'-tetramethylbenzidine and ammonia is 1-1.2:0.08:0.

1.

4. The silicon-carbon anode material according to claim 3, characterized in that: The first heating temperature is 350-400℃; the second heating temperature is 650-700℃.

5. The silicon-carbon anode material according to claim 4, characterized in that: The coating amount of slurry on the carbon cloth current collector is 10-12 mg / cm. 2 .

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