Method for testing carbon-coating completeness of silicon-carbon-coated negative electrode material

Abstract

The application provides a kind of silicon-carbon coated negative material carbon coating completeness test method, the test method is through chemical method test silicon-carbon negative material in silicon element carbon coating completeness, this chemical method does not need to use expensive instrument equipment, through ordinary laboratory can satisfy experimental condition;And the data obtained by the above-mentioned chemical method is substituted into formula, the carbon coating completeness data of silicon element in silicon-carbon negative material can be obtained, the method is simple and easy to understand, easy to operate, the same material is verified by the results of multiple experiments of the application, and the coating completeness test is carried out by using the method of the application at different times or different reaction solvents, and the difference between the test conclusions is not more than 0.5%, which can better characterize the coating completeness of the material, and the method provided by the application has good stability.

Description

Technical Field

[0001] This invention relates to the technical field of characterization and testing methods, and in particular to a method for testing the integrity of carbon coating on silicon-carbon coated anode materials. Background Technology

[0002] In the powder industry, surface coating modification is a crucial method for improving product performance, and coating integrity is a key parameter in powder modification. Similarly, in the manufacturing process of silicon-carbon anode materials, carbon coating modification of the silicon anode material surface can improve silicon cycle efficiency, inhibit silicon expansion during cycling, and prevent direct contact between silicon and electrolyte, thus improving cycle performance. However, currently, the integrity of the silicon surface carbon coating is mainly characterized by indirect examination and detection methods, the main methods of which are as follows:

[0003] First, scanning electron microscopy combined with energy dispersive spectroscopy is used, but since the types and contents of surface elements of particles in the coated and uncoated parts are different, this method can only observe particles in a small area, and the results are relatively one-sided.

[0004] Second, transmission electron microscopy combined with energy dispersive spectroscopy was used, but because the types and contents of elements on the surface of the particles in the coated and uncoated parts are different, as are the lattice fringes on the particle surface, only particles in a small area can be observed, and the results are relatively one-sided.

[0005] Third, XPS is used. XPS is another method for analyzing material surfaces. The signal source thickness is <10nm. It can have a very sensitive response to the material surface and can display the elemental information of the material surface. Semi-quantitative analysis can be performed based on the corresponding peak area on the obtained spectrum. However, when applied to the calculation of powder coating rate, the signal source is shallow, the error is large, and the test efficiency is low.

[0006] Furthermore, the above methods all require specialized and expensive instruments and equipment, and cannot be performed in ordinary laboratories using simple chemical instruments.

[0007] In view of this, the inventors have specifically designed a method for testing the integrity of carbon coating in silicon-carbon coated anode materials, which leads to this invention. Summary of the Invention

[0008] To solve the above problems, the technical solution of the present invention is as follows:

[0009] A method for testing the carbon coating integrity of silicon-carbon coated anode materials includes the following steps:

[0010] Step 1: Dry the initial sample 1 and the crucible; then weigh the crucible and record the weight M1; add the initial sample 1 into the crucible and weigh and record the weight M2; sinter the crucible containing the initial sample 1, cool it, weigh the crucible and the initial sample 1 and record the total weight M3.

[0011] Step 2: Calculate the silicon content P1 in the initial sample 1;

[0012] Step 3: Take the initial sample 2 and record its weight as M4. Then place the initial sample 2 in a beaker and add the reaction solution to completely react the silicon and its oxide in the initial sample 2. After the reaction is complete, let the beaker stand.

[0013] Step 4: Take a dry filter paper and measure and record its weight M5; filter the mixture in the beaker after standing in step 3 through the dry filter paper to obtain the filtrate, wash it several times, dry the filtrate together with the dry filter paper and weigh and record M6.

[0014] Step 5: Calculate the mass of the filtered material obtained after the reaction, M7 = M6 - M5, and calculate the yield, P2 = M7 / M4;

[0015] Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh the sample and the crucible (M8). Sinter the crucible containing the filter material, and after cooling, weigh the crucible and the filter material and record the weight (M9).

[0016] Step 7: Calculate the silicon content P3 of the filtered material after etching with hydrogen fluoride in step 6;

[0017] Step 8: Calculate the proportion of coated silicon elements = P3*P2 / P1.

[0018] Furthermore, the drying method in step 1 is as follows: place the crucible containing the initial sample 1 in a vacuum drying oven, and set the drying temperature to 60℃-200℃ and the time to 2-24h.

[0019] Furthermore, the sintering method in step 1 is as follows: place the crucible containing the dried sample into the heating furnace, open the inlet and outlet valves, introduce air or oxygen, turn on the gas flow meter and adjust it to 50-1000 ml / min, sinter to 800-1500℃, and hold for 2-24 hours.

[0020] Furthermore, the formula for calculating P1 in step 2 is as follows: P1 = (M3 - M1) / 60.084 * 28.0855 / (M2 - M1), where 60.084 is the relative atomic mass of silicon dioxide and 28.0855 is the relative atomic mass of silicon.

[0021] Furthermore, the cleaning method in step 4 involves rinsing three times with 0.2-10L of deionized water, and the drying method in step 4 is vacuum drying at a temperature of 60-200℃.

[0022] Furthermore, the sintering method in step 6 is as follows: place the crucible containing some filter material into the heating furnace, open the inlet and outlet valves to allow air or oxygen to pass through, turn on the gas flow meter to adjust to 50-2000 ml / min, sinter to 800-1500℃, and hold for 2-24 hours.

[0023] Furthermore, in step 4, the solution that can react with silicon and its oxides is a 1%-40% hydrogen fluoride solution or a 0.5-5 mol / L sodium hydroxide solution.

[0024] Furthermore, in step 7, the formula for calculating P3 is P3 = (M9 - M1) / 60.084 * 28.0855 / (M8 - M1).

[0025] Furthermore, the heating furnace in steps 1 and 6 is a muffle furnace.

[0026] This invention provides a method for testing the carbon coating integrity of silicon-carbon coated anode materials, which has the following beneficial effects:

[0027] 1. This invention uses a chemical method to test the integrity of the carbon coating of silicon elements in silicon-carbon anode materials. This chemical method does not require expensive instruments and equipment, and the experimental conditions can be met by ordinary laboratories.

[0028] 2. By substituting the data obtained through the above chemical method into the formula, the carbon coating integrity data of silicon element in silicon-carbon anode material can be obtained. This method is simple and easy to understand. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects of this invention clearer and more understandable, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] This application provides a method for testing the carbon coating integrity of silicon-carbon coated anode materials. To better understand the above technical solution, specific implementation methods will be used to describe it in detail below.

[0031] Example 1:

[0032] In this Example 1, the test material was GRS3000 silicon-carbon coated material from Xiamen High-Capacity Mi New Materials Technology Co., Ltd., and the following steps were taken:

[0033] Step 1: Weigh 10g of GRS3000 and place it together with the crucible in a vacuum drying oven for drying. Set the drying temperature to 80℃ and the drying time to 5h. Then weigh the dried crucible and record the weight as M1 = 8.43973g. Fill the crucible with initial sample 1 to 2 / 3 and weigh the total weight as M2 = 8.98862g. Place the crucible containing initial sample 1 into a tube furnace, open the inlet and outlet valves, and purge with air or oxygen. Turn on the gas flow meter and adjust it to 50ml / min. Sinter at 800℃ for 24h. After cooling, weigh the crucible and initial sample 1 and record the total weight as M3 = 9.44091g.

[0034] Step 2: Calculate the silicon content P1 in the initial sample 1 according to the formula: P1 = (M3-M1) / 60.084*28.0855 / (M2-M1) = (9.44091-8.43973) / 60.084*28.0855 / (8.98862-8.43973)*100% = 85.27%;

[0035] Step 3: Take the initial sample 2 with a weight of M4 = 1.00874g and place it in a beaker. Add 50ml of 40% hydrogen fluoride solution and stir for 8h. Finally, add 10ml of 40% hydrogen fluoride solution. After confirming that the mixture in the beaker no longer reacts, let it stand for 2h.

[0036] Step 4: Take a dry filter paper and measure and record its weight M5 = 1.59267g; filter the mixture in the beaker after standing in Step 3 through the dry filter paper to obtain the filter material, and wash it three times with 5L of deionized water. Vacuum dry the washed filter material together with the filter paper at a temperature of 80℃. After vacuum drying, weigh it M6 = 2.2529g.

[0037] Step 5: Calculate the mass of the filtrate obtained after the reaction: M7 = M6 - M5 = 2.2529 - 1.59267 = 0.66023 g; Calculate the yield: P2 = M7 / M4 = 0.66023 / 1.00874 = 65.45%;

[0038] Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh it M8 = 9.0308g. Place the crucible containing the filter material into the tube furnace, open the inlet and outlet valves, and introduce air or oxygen. Turn on the gas flow meter and adjust it to 50ml / min. Sinter to a temperature of 800℃ and hold for 24h. After cooling, weigh the crucible and part of the filter material and record the weight M9 = 9.21773g.

[0039] Step 7: Calculate the silicon content P3 of the filtered material after hydrogen fluoride etching in Step 6: P3 = (M9-M1) / 60.084*28.0855 / (M8-M1) = (9.21773-8.43973) / 60.084*28.0855 / (9.0308-8.43973) = 61.53%;

[0040] Step 8: Calculate the carbon coating integrity of silicon as P3*P2 / P1 = 61.53%*65.45% / 85.27% = 47.23%.

[0041] Example 2:

[0042] In Example 2, the test material was GRS2000 silicon-carbon coated material from Xiamen High-Capacity Mi New Materials Technology Co., Ltd., and the following steps were taken:

[0043] Step 1: Weigh 10g of GRS2000 and place it together with the crucible in a vacuum drying oven for drying. Set the drying temperature to 100℃ and the drying time to 5h. Then weigh the dried crucible and record the weight as M1 = 8.33523g. Fill the crucible with initial sample 1 to 2 / 3 and weigh the total weight as M2 = 8.97653g. Place the crucible containing initial sample 1 into a tube furnace, open the inlet and outlet valves, and purge with air or oxygen. Turn on the gas flow meter and adjust it to 100ml / min. Sinter to a temperature of 1000℃ and hold for 8h. After cooling, weigh the crucible and initial sample 1 and record the total weight as M3 = 9.24066g.

[0044] Step 2: Calculate the silicon content P1 in the initial sample 1 according to the formula: P1 = (M3-M1) / 60.084*28.0855 / (M2-M1) = (9.24066-8.33523) / 60.09*28.09 / (8.97653-8.33523)*100% = 66.00%;

[0045] Step 3: Take the initial sample 2 with a weight of M4 = 1.00688g and place it in a beaker. Add 300ml of 1% hydrogen fluoride solution and stir for 8h. Finally, add 50ml of 1% hydrogen fluoride solution. After confirming that the mixture in the beaker no longer reacts, let it stand for 2h.

[0046] Step 4: Take a dry filter paper and measure and record its weight M5 = 1.56300g. Filter the mixture in the beaker that was left to stand in Step 3 through the dry filter paper to obtain the filtrate. Wash it three times with 1L of deionized water. Vacuum dry the cleaned filtrate together with the filter paper at a temperature of 100℃. After vacuum drying, weigh it M6 = 2.30845g.

[0047] Step 5: Calculate the mass of the filtrate obtained after the reaction: M7 = M6 - M5 = 2.30845 - 1.56300 = 0.74545 g; Calculate the yield: P2 = M7 / M4 = 0.74545 / 1.00688 = 74.04%;

[0048] Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh it M8 = 8.9049g. Place the crucible containing the filter material into the tube furnace, open the inlet and outlet valves, and introduce air or oxygen. Turn on the gas flow meter and adjust it to 100ml / min. Sinter to a temperature of 1000℃ and hold for 8 hours. After cooling, weigh the crucible and part of the filter material and record the weight M9 = 8.93580g.

[0049] Step 7: Calculate the silicon content P3 of the filtered material after etching with sodium hydroxide in Step 6: P3 = (M9-M1) / 60.09*28.09 / (M8-M1) = (8.93580-8.33523) / 60.084*28.0855 / (8.9049-8.33523) = 49.28%;

[0050] Step 8: Calculate the carbon coating integrity of silicon as P3*P2 / P1 = 49.28%*74.04% / 66.00% = 55.28%.

[0051] Example 3:

[0052] In this Example 3, the test material was GR650 silicon-carbon coated material from Xiamen High-Capacity New Materials Technology Co., Ltd., and the following steps were taken:

[0053] Step 1: Weigh 50g of GRS650 and place it together with the crucible in a vacuum drying oven for drying. Set the drying temperature to 110℃ and the drying time to 5h. Then weigh the dried crucible and record the weight as M1 = 31.5g. Fill the crucible with initial sample 1 to 2 / 3 full and weigh the total weight as M2 = 55.5g. Place the crucible containing initial sample 1 into a muffle furnace, open the inlet and outlet valves, and purge with air or oxygen. Turn on the gas flow meter and adjust it to 2000ml / min. Sinter at 1000℃ for 8h. After cooling, weigh the crucible and initial sample 1 and record the total weight as M3 = 38.9g.

[0054] Step 2: Calculate the silicon content P1 in the initial sample 1 according to the formula: P1 = (M3-M1) / 60.084*28.0855 / (M2-M1) = (38.9-31.5) / 60.084*28.0855 / (55.5-31.5)*100% = 14.41%;

[0055] Step 3: Take the initial sample 2 with a weight of M4 = 10g and place it in a beaker. Then add 500ml of 0.5mol / L sodium hydroxide solution and stir for 8h. Finally, add 100ml of 0.5mol / L sodium hydroxide solution. After confirming that the mixture in the beaker no longer reacts, let it stand for 24h.

[0056] Step 4: Take a dry filter paper and measure and record its weight M5 = 1.6543g; filter the mixture in the beaker after standing in Step 3 through the dry filter paper to obtain the filter material, and wash it three times with 5L of deionized water. Vacuum dry the washed filter material together with the filter paper at a temperature of 110℃. After vacuum drying, weigh it M6 = 11.3567g.

[0057] Step 5: Calculate the mass of the filtrate obtained after the reaction: M7 = M6 - M5 = 11.3567 - 1.6543 = 9.7024 g; Calculate the yield: P2 = M7 / M4 = 9.7024 / 10 = 97.02%;

[0058] Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh it M8 = 36.4g. Place the crucible containing the filter material into the muffle furnace, open the inlet and outlet valves, and introduce air or oxygen. Turn on the gas flow meter and adjust it to 2000ml / min. Sinter at 1000℃ for 8 hours. After cooling, weigh the crucible and part of the filter material and record the weight M9 = 32.676g.

[0059] Step 7: Calculate the silicon content P3 of the filtered material after etching with sodium hydroxide in Step 6: P3 = (M9-M1) / 60.09*28.09 / (M8-M1) = (32.676-31.5) / 60.084*28.0855 / (36.4-31.5) = 11.22%;

[0060] Step 8: Calculate the carbon coating integrity of silicon as P3*P2 / P1 = 11.22%*97.02% / 14.41% = 75.54%.

[0061] Example 4:

[0062] In Example 4, the test material was GR1500 silicon-carbon coated material from Xiamen High-Capacity Mi New Materials Technology Co., Ltd., and the following steps were taken:

[0063] Step 1: Weigh 10g of GR1500 and place it together with the crucible in a vacuum drying oven for drying. Set the drying temperature to 60℃ and the drying time to 24h. Then weigh the dried crucible and record the weight as M1 = 7.86829g. Next, fill the crucible with initial sample 1 to 2 / 3 and weigh the total mass, recording it as M2 = 8.95527g. Place the crucible containing initial sample 1 into a tube furnace, open the inlet and outlet valves, and purge with air or oxygen. Turn on the gas flow meter and adjust it to 100ml / min. Sinter at 1200℃ for 5h. After cooling, weigh the crucible and initial sample 1 and record the total weight as M3 = 8.91645g.

[0064] Step 2: Calculate the silicon content P1 in the initial sample 1 according to the formula: P1 = (M3-M1) / 60.084*28.0855 / (M2-M1) = (8.91645-7.86829) / 60.084*28.0855 / (8.95527-7.86829)*100% = 45.08%;

[0065] Step 3: Take the initial sample 2 with a weight of M4 = 1.08775g and place it in a beaker. Then add 200ml of 5mol / L sodium hydroxide solution and stir for 8h. Finally, add 50ml of 1mol / L sodium hydroxide solution. After confirming that the mixture in the beaker no longer reacts, let it stand for another 8h.

[0066] Step 4: Take a dry filter paper and measure and record its weight M5 = 1.57374g; filter the mixture in the beaker after standing in Step 3 through the dry filter paper to obtain the filtrate, and wash it three times with 1L of deionized water. Vacuum dry the cleaned filtrate together with the filter paper at a temperature of 60℃. After vacuum drying, weigh it M6 = 2.52248g.

[0067] Step 5: Calculate the mass of the filtrate obtained after the reaction: M7 = M6 - M5 = 2.52248 - 1.57374 = 0.94874 g; Calculate the yield: P2 = M7 / M4 = 0.94874 / 1.08775 = 87.22%;

[0068] Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh it M8 = 8.61667g. Place the crucible containing the filter material into the tube furnace, open the inlet and outlet valves, and introduce air or oxygen. Turn on the gas flow meter and adjust it to 100ml / min. Sinter at 1200℃ for 5 hours. After cooling, weigh the crucible and part of the filter material and record the weight M9 = 8.45487g.

[0069] Step 7: Calculate the silicon content P3 of the filtered material after etching with sodium hydroxide in Step 6: P3 = (M9-M1) / 60.09*28.09 / (M8-M1) = (8.45487-7.86829) / 60.084*28.0855 / (8.61667-7.86829) = 36.64%;

[0070] Step 8: Calculate the carbon coating integrity of silicon as P3*P2 / P1 = 36.64%*87.22% / 45.08% = 70.89%.

[0071] Example 5:

[0072] In Example 5, the test material was GR3000 silicon-carbon coated material from Xiamen High-Capacity New Materials Technology Co., Ltd., and the following steps were taken:

[0073] Step 1: Weigh 10g of GR1500 and place it together with the crucible in a vacuum drying oven for drying. Set the drying temperature to 200℃ and the drying time to 2h. Then weigh the dried crucible and record the weight as M1 = 8.33788g. Fill the crucible with initial sample 1 to 2 / 3 and weigh the total mass as M2 = 8.8034g. Place the crucible containing initial sample 1 into a box furnace, open the inlet and outlet valves, and purge with air or oxygen. Turn on the gas flow meter and adjust it to 300ml / min. Sinter at 1500℃ for 2h. After cooling, weigh the crucible and initial sample 1 and record the total weight as M3 = 9.18675g.

[0074] Step 2: Calculate the silicon content P1 in the initial sample 1 according to the formula: P1 = (M3-M1) / 60.084*28.0855 / (M2-M1) = (9.18675-8.33788) / 60.084*28.0855 / (8.8034-8.33788)*100% = 85.27%;

[0075] Step 3: Take the initial sample 2 with a weight of M4 = 1.00874g and place it in a beaker. Add 200ml of 5mol / L sodium hydroxide solution and stir for 8h. Then add 50ml of 5mol / L sodium hydroxide solution. After confirming that the mixture in the beaker no longer reacts, let it stand for 2h.

[0076] Step 4: Take a dry filter paper and measure and record its weight M5 = 1.57494g; filter the mixture in the beaker after standing in Step 3 through the dry filter paper to obtain the filter material, and wash it three times with 3L of deionized water. Vacuum dry the washed filter material together with the filter paper at a temperature of 80℃. After vacuum drying, weigh it M6 = 2.23517g.

[0077] Step 5: Calculate the mass of the filtrate obtained after the reaction: M7 = M6 - M5 = 2.23517 - 1.57494 = 0.66023 g; Calculate the yield: P2 = M7 / M4 = 0.66023 / 1.00874 = 65.45%;

[0078] Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh it M8 = 8.98838g. Place the crucible containing the filter material into the box furnace, open the inlet and outlet valves, and introduce air or oxygen. Turn on the gas flow meter and adjust it to 300ml / min. Sinter at 1500℃ for 2 hours. After cooling, weigh the crucible and part of the filter material and record the weight M9 = 9.19271g.

[0079] Step 7: Calculate the silicon content of the sample after etching with sodium hydroxide in Step 6: P3 = (M9-M1) / 60.09*28.09 / (M8-M1) = (9.19271-8.33788) / 60.084*28.0855 / (8.98838-8.33788) = 61.17%;

[0080] Step 8: Calculate the carbon coating integrity of silicon as P3*P2 / P1 = 61.17%*65.45% / 85.27% = 46.95%.

[0081] Based on the above embodiments 1-5, the following parameter table can be obtained:

[0082]

[0083]

[0084] In summary, this invention provides a chemical method for testing the carbon coating integrity of silicon in silicon-carbon anode materials. This chemical method does not require expensive equipment and can be performed in a standard laboratory. By substituting the data obtained through this chemical method into the formula, the carbon coating integrity data of silicon in the silicon-carbon anode material can be obtained. This method is simple, easy to understand, and easy to operate. Multiple experimental results have verified that when the same material is tested for coating integrity at different times or with different reaction solvents using the method of this invention, the difference in test results does not exceed 0.5%, which can effectively characterize the coating integrity of the material. Furthermore, the method provided by this invention has good stability.

[0085] The present invention has been described above by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for testing the integrity of carbon coating in silicon-carbon coated anode materials, characterized in that, Includes the following steps: Step 1: Dry the initial sample 1 and the crucible; then weigh the crucible and record the weight M1; add the initial sample 1 into the crucible and weigh and record the weight M2; sinter the crucible containing the initial sample 1, cool it, weigh the crucible and the initial sample 1 and record the total weight M3. Step 2: Calculate the silicon content P1 in the initial sample 1. The formula for calculating P1 is as follows: P1 = (M3 - M1) / 60.084 * 28.0855 / (M2 - M1); Step 3: Take the initial sample 2 and record its weight as M4. Then place the initial sample 2 in a beaker and add the reaction solution to completely react the silicon and its oxide in the initial sample 2. After the reaction is complete, let the beaker stand. Step 4: Take a dry filter paper and measure and record its weight M5; filter the mixture in the beaker after standing in step 3 through the dry filter paper to obtain the filtrate, wash it several times, dry the filtrate together with the dry filter paper and weigh and record M6. Step 5: Calculate the mass of the filtered material obtained after the reaction, M7 = M6 - M5, and calculate the yield, P2 = M7 / M4; Step 6: Add a portion of the filter material obtained in Step 4 to the crucible and weigh the sample and the crucible (M8). Sinter the crucible containing the filter material, and after cooling, weigh the crucible and the filter material and record the weight (M9). Step 7: Calculate the silicon content P3 of the filter material in Step 6 after etching with hydrogen fluoride. The formula for calculating P3 is P3=(M9-M1) / 60.084*28.0855 / (M8-M1); Step 8: Calculate the proportion of coated silicon elements = P3 * P2 / P1.

2. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 1, characterized in that, The drying method in step 1 is as follows: place the crucible containing the initial sample 1 in a vacuum drying oven, and set the drying temperature to 60℃-200℃ and the time to 2-24h.

3. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 2, characterized in that, The sintering method in step 1 is as follows: place the crucible containing the dried sample into the heating furnace, open the inlet and outlet valves, introduce air or oxygen, turn on the gas flow meter and adjust it to 50-1000 ml / min, sinter to 800-1500℃, and hold for 2-24 hours.

4. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 1, characterized in that, The cleaning method in step 4 is to wash three times with 0.2-10L of deionized water. The drying method in step 4 is vacuum drying, and the drying temperature is 60-200℃.

5. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 1, characterized in that, The sintering method in step 6 is as follows: place the crucible containing some filter material into the heating furnace, open the inlet and outlet valves, introduce air or oxygen, turn on the gas flow meter and adjust it to 50-2000 ml / min, sinter to 800-1500℃, and hold for 2-24 hours.

6. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 3, characterized in that, In step 4, the solution that can react with silicon and its oxides is a 1%-40% hydrogen fluoride solution or a 0.5-5 mol / L sodium hydroxide solution.

7. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 3, characterized in that, The heating furnace in step 1 is a muffle furnace.

8. The method for testing the carbon coating integrity of silicon-carbon coated anode materials according to claim 5, characterized in that, The heating furnace in step 6 is a muffle furnace.

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