Method for testing carbon content of high-carbon silicon carbon material

Abstract

The invention discloses a method for testing the carbon content of a high-carbon silicon carbon material. The method comprises the following steps: S1, preparing a high-frequency infrared carbon-sulfur instrument, a ceramic crucible, a gas supply system, a standard substance, a fluxing agent and a sample; s2, carrying out carbon content calibration by adopting a standard substance, and carrying out standard sample testing after calibration is completed; s3, putting the weighed fluxing agent and sample into a ceramic crucible, and then putting the ceramic crucible into a high-frequency infrared carbon-sulfur instrument for heating and reaction; and detecting CO generated by the reaction to obtain test data of the carbon content in the sample. The method for testing the carbon content of the high-carbon silicon-carbon material solves the problems of poor stability, insufficient precision and the like when a silicon-carbon material with high carbon content (greater than 40%) is tested in the prior art, is high in detection speed, can realize batch continuous detection, is more accurate in result and small in error, improves the accuracy and reliability of the testing method, and is suitable for popularization and application. And the method is particularly suitable for accurate analysis of the silicon-carbon material with high carbon content (greater than 40%).

Description

Technical Field

[0001] The present invention relates to the technical field of carbon content testing, and in particular to a method for testing the carbon content of high-carbon silicon-carbon materials. Background Art

[0002] With the growing demand for high-energy-density batteries in electric vehicles and energy storage systems, traditional graphite anodes (theoretical capacity of 372 mAh / g) can no longer meet the requirements. Silicon-based anodes have become a research hotspot due to their ultra-high theoretical capacity (4200 mAh / g).

[0003] Chemical vapor deposition (CVD) is widely recognized by battery cell manufacturers as the ultimate silicon anode solution due to its short production process, minimal equipment, and low theoretical cost. Compared to traditional high-capacity anode materials like silicon oxide and ground silicon carbon, CVD-produced silicon carbon significantly improves battery performance in terms of first-cycle efficiency, energy density, cycling performance, and cell expansion, effectively resolving the bottlenecks associated with other silicon-based materials in battery cell applications.

[0004] Carbon content testing is a key step in analyzing the composition of silicon-carbon materials and provides valuable guidance for determining whether material specifications meet standards. Currently, there are many methods for testing carbon content, including combustion, wet chemical, and spectroscopy. High-frequency combustion infrared absorption has become the mainstream technology for carbon content testing in silicon-carbon materials due to its high precision (reaching the ppm level), high degree of automation, rapid and efficient detection, and simultaneous multi-element detection (sulfur). However, this method suffers from poor test stability and insufficient precision when testing samples with high carbon contents (>40%), significantly interfering with the determination of product quality.

[0005] Currently, the industry is addressing the issue of unstable testing of high-carbon materials by optimizing combustion conditions (such as increasing oxygen flow and adjusting flux ratios), improving detection algorithms (such as dynamic baseline correction), and employing multiple detectors (such as infrared and thermal conductivity combined detection) to improve data reliability. However, these efforts remain ineffective in addressing the issue of stable carbon content testing. For ultra-high-carbon materials, more stable pretreatment methods or higher-precision detection technologies are still needed to meet the needs of industrial testing and scientific research.

[0006] Therefore, it is necessary to provide a testing method for the carbon content of high silicon-carbon materials, which can solve the problems of poor repeatability and large errors in carbon content test results while ensuring efficient and rapid testing conditions, and provide a reliable analytical means for the quality control of silicon-carbon materials. Summary of the Invention

[0007] Purpose of the invention: In order to overcome the above shortcomings, the purpose of the present invention is to provide a method for testing the carbon content of high-carbon silicon-carbon materials, which solves the problems of poor stability and insufficient precision when testing silicon-carbon materials with high carbon content (>40%) in the prior art. The method has a fast detection speed and can realize batch continuous detection. The results are more accurate and the error is small, which improves the accuracy and reliability of the test method and is particularly suitable for the precise analysis of silicon-carbon materials with high carbon content (>40%).

[0008] Technical solution: A method for testing the carbon content of a high-carbon silicon-carbon material comprises the following steps: S1 Preparation: Prepare the high-frequency infrared carbon-sulfur analyzer, the ceramic crucible and gas supply system, standard substances, flux and samples (silicon-carbon materials); S2 calibration and standard sample test: Use standard substances to calibrate the carbon content. After the calibration is completed, perform standard sample test. After the standard sample test data is stable for multiple consecutive times, the sample test can be performed. S3 sample test: S31 Heating and Reaction: Place weighed flux and sample in a ceramic crucible, then place the ceramic crucible in a high-frequency infrared carbon-sulfur analyzer. Start the high-frequency infrared carbon-sulfur analyzer and heat the flux and sample until they are completely melted. While heating, start the gas supply system. The carbon element in the sample reacts with the introduced oxygen and is released in the form of CO2. S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The generated CO2 gas enters the infrared detector, which uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the CO2 absorption intensity; S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0009] Furthermore, in the above-mentioned method for testing the carbon content of high-carbon silicon-carbon materials, in S1, the standard substance includes but is not limited to one of GBW-11111, GSB 06-2181-2008-6, and EDTA; the flux includes but is not limited to one or a combination of multiple of iron, tin, tungsten, and copper; and the surface of the ceramic crucible is cleaned and dried before use.

[0010] In order to ensure the stability and reliability of the data during the experiment, the surface of the ceramic crucible must be cleaned before use to remove all kinds of impurities and contaminants attached to the inside and outside of the ceramic crucible, and then placed in an oven to dry.

[0011] Furthermore, in the above-mentioned method for testing the carbon content of high-carbon silicon-carbon materials, in S1, after the preparation work is completed, a leak test is required, and calibration work can be prepared only after the leak test passes.

[0012] Furthermore, the carbon content testing method of the high-carbon silicon-carbon material, S2, specifically comprises the following steps: S21 Carbon Content Calibration: Select a suitable standard substance; input the carbon content of the standard substance into the high-frequency infrared carbon-sulfur analyzer; place the weighed standard substance in a ceramic crucible, then place the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and compare and calibrate the carbon content of the standard substance detected by the high-frequency infrared carbon-sulfur analyzer with the carbon content of the input standard substance; S22 Standard sample test: After the calibration is completed, use the same standard substance to perform the standard sample test again. The test conditions of each standard sample test are consistent. Perform the standard sample test continuously and observe the stability of the standard sample test data. If the fluctuation of the standard sample test data for 5-6 consecutive times is within the allowable error range, it is considered that the calibration is valid and the data is stable, and the sample test can be carried out. Otherwise, it is necessary to recalibrate or check whether there are any problems with the high-frequency infrared carbon and sulfur analyzer and the operation process.

[0013] Selecting appropriate reference materials (such as low-carbon and high-carbon standards) ensures measurement data accuracy and traceability. This selection of reference materials optimizes the mixing ratio, ensures complete combustion, and optimizes analytical methods, reducing testing costs and significantly improving analytical efficiency.

[0014] Preferably, using a standard substance with a carbon content close to that of the sample as a calibration standard can significantly improve detection accuracy.

[0015] In step S2, standard substances for coal physical and chemical composition analysis were used: the first standard substance was numbered GBW11111 (52.45%); the second standard substance was numbered GSB 06-2181-2008-6 (ZBM105 52.69%); and the third standard substance was numbered EDTA (41.1%).

[0016] Furthermore, in the above-mentioned method for testing the carbon content of high-carbon silicon-carbon materials, in S31, the flux includes but is not limited to a combination of at least two of iron, tin, tungsten, and copper; the flux and sample are placed on a ceramic crucible in a stacked manner, and a sandwich stacking order is adopted, i.e. flux-sample-flux.

[0017] In carbon content determination, the melting point of the flux is closely related to the sample heating process. When mixed with the sample, the flux forms a eutectic mixture, which allows the sample to melt at a lower temperature and promotes combustion. Selecting the appropriate flux composition and ratio is key to ensuring accurate and repeatable carbon and sulfur analysis.

[0018] During the test, the stacking order of flux and sample in the ceramic crucible has certain influence on the test results. If the flux covers the sample, it may prevent the oxygen from entering at a speed during the sample combustion process, increasing the combustion time; if the sample covers the flux, it may cause splashing pollution during the combustion process; if the flux is uniformly mixed with the sample, the sample can be fully combusted, reducing the test error.

[0019] Further, the carbon content test method of the high-carbon silicon-carbon material, in the S31, specifically comprises the following steps: S31.1: first weighing the flux 1 in the ceramic crucible, then weighing the sample and stacking the sample on the flux 1, and finally weighing the flux 2 and stacking the flux 2 on the sample; S31.2: placing the ceramic crucible into the high-frequency infrared carbon-sulfur instrument, starting the high-frequency infrared carbon-sulfur instrument for heating, and starting the gas supply system at the same time.

[0020] Further, in the S31.1 of the carbon content test method of the high-carbon silicon-carbon material, the flux 1 is at least one of iron, tin, tungsten, and copper, 0.40-1.20 g of the flux 1 is weighed, the flux 2 is at least one of iron, tin, tungsten, and copper, 0.40-2.00 g of the flux 2 is weighed, and 0.02-0.04 g of the silicon-carbon material is weighed as the sample.

[0021] In the S31 step, the flux 1 (including at least one flux) and the flux 2 (including at least one flux) can be selected from pure iron (adjusting the combustion temperature), tin (low-temperature flux), tungsten particles (providing local ultrahigh temperature (above 2000℃) under high heat, but not melting itself), copper particles (auxiliary heat conduction, which needs to be used in cooperation with high-melting-point flux), and other combustion-supporting agents; generally, high-melting-point flux (providing heat) and low-melting-point flux (promoting melting and reaction uniformity) are used in combination.

[0022] Further, in the S31.1 step, for the silicon-carbon material with high carbon content, the proportion of tungsten particles needs to be increased to increase the heat generation. Adding flux such as pure iron in the high-frequency infrared carbon-sulfur instrument has a very high magnetic and electric conductivity, increases the electromagnetic induction of the sample, generates high-frequency induced current, and thus obtains heat.

[0023] Further, in the S31.2 of the carbon content test method of the high-carbon silicon-carbon material, the high-frequency infrared carbon-sulfur instrument heats the sample to 1600-1800℃, and the combustion time is 10-60 s.

[0024] Preferably, the combustion time is 30 s.

[0025] Furthermore, in the above-mentioned method for testing the carbon content of high-carbon silicon-carbon materials, the gas supply system adopts dual-gas-path coordinated control, specifically: the main gas path is equipped with a high-precision oxygen supplier, the working pressure is strictly controlled within the range of 3.0-3.5 bar, and a constant flow oxygen supply mode is adopted, with an oxygen flow rate of 2-5 L / min to ensure sufficient combustion; the auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stability in gas mixing and transportation.

[0026] Preferably, the flow rate of oxygen is 4.1 L / min.

[0027] The present invention precisely adjusts the gas dynamics characteristics during the high-temperature combustion process of the sample. Under oxygen combustion conditions, the carbon element in the sample reacts with oxygen to generate CO2 gas, and other components will also undergo oxidation reactions to consume oxygen. Since the gas supply system adopts a constant flow oxygen supply mode (2-5L / min, preferably 4.1 L / min), the dynamic oxygen consumption during the sample combustion process will cause the gas flow rate to fluctuate. This flow change will directly affect the gas residence time in the infrared detection cell, thereby causing the measurement signal to drift. More importantly, there are significant differences in the combustion characteristics between different samples, which makes the gas dynamics process of each test unique, which is one of the main factors leading to differences in the repeatability of the measurement results. In order to ensure the accuracy of the analysis, the gas supply system adopts dual gas path coordinated control.

[0028] Furthermore, the carbon content testing method of the above-mentioned high-carbon silicon-carbon material, in said S321, specifically includes the following contents: the gas generated by the reaction in S31 is first carried by the carrier gas through a water / sulfur removal device and a filtering device for treatment to obtain treated CO2 gas, and then the treated CO2 gas enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light, and the carbon content is reflected by detecting its absorption intensity.

[0029] During the high-temperature process, the carbon in the sample (silicon-carbon material) reacts with oxygen to produce CO2, which may also be accompanied by other reaction products (such as SO2 and water vapor). To ensure accurate detection, the resulting gas must be purified. This includes dehydration and desulfurization equipment: Dehydration: Magnesium perchlorate (Mg(ClO4)2) or silica gel can be used to absorb moisture to prevent water vapor from interfering with infrared detection. Desulfurization: Desulfurizers (such as soda lime or MnO2) can be used to remove SO2 to prevent it from affecting CO2 detection. Filters: Remove particulate matter to ensure gas purity. Finally, the pure CO2 enters the infrared detector for quantitative analysis.

[0030] The core of infrared detection is based on non-dispersive infrared spectroscopy (NDIR) technology, specifically: 1. CO2 molecules have a strong infrared absorption peak at 4.26 μm (wave number 2349 cm⁻¹), which is the characteristic absorption peak of CO2.

[0031] 2. Infrared detectors usually include: (1) Infrared light source: emits stable infrared light; (2) Gas detection cell: when CO2 gas passes through the detection cell, it absorbs light of a specific wavelength; (3) Filter: only allows light with a wavelength of 4.26 μm to pass through, eliminating interference from other bands; (4) Infrared detector (such as pyroelectric sensor or thermopile): when infrared light irradiates the infrared detector, the infrared detector absorbs photons and produces temperature changes. Due to the thermoelectric effect, the temperature change is converted into an electrical signal.

[0032] A high-frequency infrared carbon and sulfur analyzer first integrates the electrical signal output by an infrared detector (such as a pyroelectric sensor or thermopile). Then, through the analyzer's conversion process, the integrated electrical signal is converted into the concentration of the measured gas (CO2). Finally, based on chemical reaction principles and relevant formulas, the CO2 concentration is used to calculate the carbon content in the silicon-carbon material. For example, based on the stoichiometric relationship between carbon and CO2, 1 mol of carbon completely burns to produce 1 mol of CO2. By measuring the amount or concentration of CO2, the carbon content in the sample can be calculated.

[0033] Furthermore, in the above-mentioned method for testing the carbon content of high-carbon silicon-carbon materials, in S32, nitrogen is used as a carrier gas to transport the gas generated by the reaction in S31 to a water / sulfur removal device and a filtration device for treatment.

[0034] The beneficial effects of the present invention are: (1) The carbon content testing method of high-carbon silicon-carbon materials described in the present invention can solve the problems of poor repeatability and large errors in carbon content test results while ensuring efficient and rapid testing conditions; (2) The carbon content test method of high-carbon silicon-carbon materials described in the present invention uses a high-frequency infrared carbon-sulfur analyzer. The test time for a single sample can be controlled within 3-5 minutes, which can realize batch continuous detection and significantly improve the test efficiency. At the same time, the detection limit can reach 0.001% (10ppm) and the degree of automation is high, which can reduce human operation errors and significantly improve data accuracy, providing a reliable analytical means for the quality control of silicon-carbon materials. (3) The carbon content test method of high-carbon silicon-carbon materials described in the present invention significantly improves the accuracy and reliability of the test method through multi-dimensional optimization and system verification. First, a composite flux system with a specific ratio is adopted. The effective selection of the flux can lower the melting point of the sample, accelerate the reaction, improve the combustion environment, etc., prevent the sample from splashing, and effectively reduce the interference of gas residues. (4) The carbon content test method of high-carbon silicon-carbon materials described in the present invention is rationally designed, and the flux materials are iron, tin, tungsten, and copper; cross-validation is performed based on different standard substances (such as GBW-11111, GSB06-2181-2008-6, EDTA), and the optimal sample addition sequence is optimized; finally, the excellent stability of the invention is confirmed by repeated tests at different time points (RSD < 1.0%); this series of optimization measures significantly reduces the accuracy of carbon content testing, and is particularly suitable for the precise analysis of silicon-carbon materials with high carbon content (> 40%). DETAILED DESCRIPTION

[0035] The following examples 1 to 7 and comparative example 1 are combined with specific experimental data to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] In the following examples of the present invention, the first standard substance is numbered GBW 11111 (52.45%), which is sourced from the Testing Center of China Coal Science and Technology Research Institute Co., Ltd.; the second standard substance is numbered GSB 06-2181-2008-6 (ZBM10552.69%), which is sourced from Jinan Zhongbiao Technology Co., Ltd.; the third standard substance is numbered EDTA (41.1%), which is sourced from Xi'an Tianmao Baoding Biotechnology Co., Ltd.

[0037] Unless otherwise specified, the materials, methods and equipment used in the embodiments of the present invention are conventional materials, methods and equipment in this technical field.

[0038] The following Examples 1 to 7 provide a method for testing the carbon content of a high-carbon silicon-carbon material.

[0039] Example 1 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 1 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system that matches the high-frequency infrared carbon-sulfur analyzer, standard material GBW-11111 (52.45%), flux copper particles, flux tungsten particles, and samples (silicon-carbon materials); S2 calibration and standard sample test: Use 0.02-0.03g of standard substance GBW-11111 (52.45%) for carbon content calibration. After the calibration is completed, perform standard sample test. After the standard sample test data is stable for 5-6 consecutive times, the sample test can be performed. S3 sample test: S31 Heating and Reaction: First weigh 0.40-0.60g of flux copper particles in a ceramic crucible, then weigh 0.02-0.03g of sample and stack the sample on the flux copper particles, and finally weigh 1.40-1.50g of flux tungsten particles and stack the flux tungsten particles on the sample; then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and the high-frequency infrared carbon-sulfur analyzer heats the sample to 1600℃ with a combustion time of 30s. While heating, start the gas supply system, and the carbon element in the sample reacts with the introduced oxygen and is released in the form of CO2; the gas supply system adopts dual gas path coordinated control, specifically: the main gas path is equipped with a high-precision oxygen supplier, the working pressure is strictly controlled within the range of 3.0-3.5bar, and a constant flow oxygen supply mode is adopted with an oxygen flow rate of 4.1L / min to ensure sufficient combustion; the auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stability in gas mixing and transportation; S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0040] Example 2 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 2 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system for the analyzer, standard material GSB 06-2181-2008-6 (ZBM105 52.69%), flux iron filings, flux tungsten particles, and samples (silicon-carbon material). S2 calibration and standard sample test: Use 0.02-0.03g of standard substance GSB 06-2181-2008-6 (ZBM10552.69%) for carbon content calibration. After calibration, perform standard sample test. After the standard sample test data is stable for 5-6 times in a row, perform sample test. S3 sample test: S31 Heating and Reaction: First weigh 0.02-0.03g of sample in a ceramic crucible, then weigh 1.00-1.20g of flux iron filings and stack the flux iron filings on the sample, and finally weigh 1.00-1.20g of flux tungsten particles and stack the flux tungsten particles on the flux iron filings; then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and the high-frequency infrared carbon-sulfur analyzer heats the sample to 1600℃ with a combustion time of 30s. While heating, start the gas supply system, and the carbon element in the sample reacts with the introduced oxygen and is released in the form of CO2; the gas supply system adopts dual gas path coordinated control, specifically: the main gas path is equipped with a high-precision oxygen supplier, the working pressure is strictly controlled within the range of 3.0-3.5bar, and a constant flow oxygen supply mode is adopted with an oxygen flow rate of 4.1L / min to ensure sufficient combustion; the auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stability in gas mixing and transportation; S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0041] Example 3 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 3 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system for the analyzer, standard material GBW 11111 (52.45%), flux tin, flux iron filings, flux tungsten particles, and samples (silicon-carbon materials). S2 calibration and standard sample test: Use 0.03-0.04g of standard substance GBW 11111 (52.45%) for carbon content calibration. After the calibration is completed, perform standard sample test. After the standard sample test data is stable for 5-6 consecutive times, the sample test can be performed. S3 sample test: S31 Heating and reaction: First weigh 0.30-0.50g of flux tin in a ceramic crucible, then weigh 0.03-0.04g of sample and stack the sample on the flux tin, then weigh 0.40-0.50g of flux iron filings and 1.40-1.50g of flux tungsten particles and stack the flux iron filings and flux tungsten particles on the sample; then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and heat the sample to 1600℃ for a burning time of 100-2000℃. The heating cycle is 30 seconds. Simultaneously with heating, the gas supply system is activated, and the carbon in the sample reacts with the introduced oxygen, releasing it as CO2. The gas supply system utilizes dual-path coordinated control. Specifically, the main gas path is equipped with a high-precision oxygen supplier, with the operating pressure strictly controlled within the range of 3.0-3.5 bar. A constant-flow oxygen supply mode is used, with an oxygen flow rate of 4.1 L / min, ensuring sufficient combustion. The auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stable gas mixing and delivery. S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0042] Example 4 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 4 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system that matches the high-frequency infrared carbon-sulfur analyzer, standard material GSB 06-2181-2008-6 (ZBM105 52.69%), flux copper particles, flux iron filings, and samples (silicon-carbon material); S2 calibration and standard sample test: Use 0.02-0.03g of standard substance GSB 06-2181-2008-6 (ZBM10552.69%) for carbon content calibration. After calibration, perform standard sample test. After the standard sample test data is stable for 5-6 times in a row, perform sample test. S3 sample test: S31 Heating and Reaction: First weigh 0.02-0.03g of sample in a ceramic crucible, then weigh 0.70-0.80g of flux copper particles and stack the flux copper particles on the sample, and finally weigh 0.50-0.60g of flux iron filings and stack the flux iron filings on the flux copper particles; then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and the high-frequency infrared carbon-sulfur analyzer heats the sample to 1600℃ with a combustion time of 30s. While heating, start the gas supply system, and the carbon element in the sample reacts with the introduced oxygen and is released in the form of CO2; wherein, the gas supply system adopts dual gas path coordinated control, specifically: the main gas path is equipped with a high-precision oxygen supplier, the working pressure is strictly controlled within the range of 3.0-3.5bar, and a constant flow oxygen supply mode is adopted with an oxygen flow rate of 4.1L / min to ensure sufficient combustion; the auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stability in gas mixing and transportation; S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0043] Example 5 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 5 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system that matches the high-frequency infrared carbon-sulfur analyzer, standard substance EDTA (41.1%), flux tin, flux iron filings, flux copper particles, and samples (silicon-carbon materials); S2 calibration and standard sample test: Use 0.03-0.04g of the standard substance EDTA (41.1%) for carbon content calibration. After the calibration is completed, perform the standard sample test. After the standard sample test data is stable for 5-6 consecutive times, the sample test can be performed. S3 sample test: S31 Heating and reaction: First weigh 0.40-0.50g of flux tin in a ceramic crucible, then weigh 0.50-0.60g of flux iron filings and 1.60-1.70g of flux copper particles, and stack the flux iron filings and flux copper particles on the flux tin. Finally, weigh 0.03-0.04g of sample, and stack the sample on the flux iron filings and flux copper particles. Then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and the high-frequency infrared carbon-sulfur analyzer heats the sample to 1600℃. The combustion time is 30 seconds. The gas supply system is started while heating. The carbon element in the sample reacts with the oxygen introduced and is released in the form of CO2. The gas supply system adopts dual gas path coordinated control. Specifically, the main gas path is equipped with a high-precision oxygen supplier. The working pressure is strictly controlled within the range of 3.0-3.5 bar. The constant flow oxygen supply mode is adopted, and the oxygen flow rate is 4.1L / min to ensure sufficient combustion. The auxiliary gas path introduces nitrogen as the carrier gas power source to achieve stable gas mixing and transportation. S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0044] Example 6 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 6 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system for the analyzer, standard material GBW 11111 (52.45%), flux copper pellets, flux iron filings, flux tungsten pellets, and samples (silicon-carbon material). S2 calibration and standard sample test: Use 0.02-0.03g of standard substance GBW 11111 (52.45%) for carbon content calibration. After the calibration is completed, perform standard sample test. After the standard sample test data is stable for 5-6 consecutive times, the sample test can be performed. S3 sample test: S31 Heating and reaction: First weigh 0.02-0.03g of sample in a ceramic crucible, then weigh 0.60-0.70g of flux copper particles and stack the flux copper particles on the sample, and finally weigh 0.50-0.60g of flux iron filings and 1.40-1.50g of flux tungsten particles and stack the flux iron filings and flux tungsten particles on the flux copper particles; then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and heat the sample to 1600℃ and burn it. The combustion time is 30 seconds. The gas supply system is activated during heating, and the carbon in the sample reacts with the introduced oxygen, releasing it as CO2. The gas supply system uses dual-path coordinated control. Specifically, the main gas path is equipped with a high-precision oxygen supplier, with the operating pressure strictly controlled within the range of 3.0-3.5 bar. A constant-flow oxygen supply mode is used, with an oxygen flow rate of 4.1 L / min, to ensure sufficient combustion. The auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stable gas mixing and delivery. S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0045] Example 7 The method for testing the carbon content of the high-carbon silicon-carbon material of Example 7 comprises the following steps: S1 Preparation: Prepare a high-frequency infrared carbon-sulfur analyzer, a ceramic crucible and gas supply system for the analyzer, standard material EDTA (41.1%), flux copper particles, flux tin, and samples (silicon-carbon materials); S2 calibration and standard sample test: Use 0.02-0.03g of the standard substance EDTA (41.1%) for carbon content calibration. After the calibration is completed, perform the standard sample test. After the standard sample test data is stable for 5-6 consecutive times, the sample test can be performed; S3 sample test: S31 Heating and Reaction: First weigh 0.70-0.80g of flux copper particles in a ceramic crucible, then weigh 0.40-0.50g of flux tin and stack the flux tin on the flux copper particles, and finally weigh 0.02-0.03g of sample and stack the sample on the flux copper particles; then put the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer, and the high-frequency infrared carbon-sulfur analyzer heats the sample to 1600℃ with a combustion time of 30s. While heating, start the gas supply system, and the carbon element in the sample reacts with the introduced oxygen and is released in the form of CO2; wherein, the gas supply system adopts dual gas path coordinated control, specifically: the main gas path is equipped with a high-precision oxygen supplier, the working pressure is strictly controlled within the range of 3.0-3.5bar, and a constant flow oxygen supply mode is adopted with an oxygen flow rate of 4.1L / min to ensure sufficient combustion; the auxiliary gas path introduces nitrogen as a carrier gas power source to achieve stability in gas mixing and transportation; S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The gas generated by the reaction in S31 is first carried by the carrier gas nitrogen and passed through the water / sulfur removal device and the filtration device for treatment to obtain the treated CO2 gas. The treated CO2 gas then enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light. The carbon content is reflected by detecting its absorption intensity. S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

[0046] The following comparative example 1 is a prior art (Chinese patent CN106940278A, a method for testing the silicon and carbon content in a negative electrode material for a lithium-ion battery).

[0047] Comparative Example 1 The test method of Comparative Example 1 includes the following steps: S101: Weighing silicon-carbon powder with a weight of M and placing it into an empty beaker; using an electronic balance with an accuracy of one ten-thousandth of a gram, weighing silicon-carbon powder with a weight of M and placing the silicon-carbon powder into the empty beaker.

[0048] S102: Add hydrofluoric acid into the beaker; add hydrofluoric acid with a concentration of 40% into the beaker, and the amount of hydrofluoric acid is slightly greater than the silicon content, so as to ensure that the hydrofluoric acid reacts with all the silicon elements in the silicon-carbon powder to generate gaseous silicon tetrafluoride and remove all the silicon elements, in order to make the reaction sufficient, shake the beaker after adding the hydrofluoric acid, and shake the silicon-carbon powder and the hydrofluoric acid evenly.

[0049] S103: Put the beaker into constant-temperature water at 80°C for heating for several hours; put the beaker into constant-temperature water at 80°C for heating for several hours, so that the hydrofluoric acid fully reacts with the silicon elements until all the silicon elements become gaseous and are discharged S104: Take out the beaker and cool it to room temperature, and then filter the mixed solution in the beaker with filter paper to obtain carbon powder; after the silicon elements are removed, filter the excess hydrofluoric acid with filter paper to obtain carbon powder.

[0050] S105: Wash the carbon powder on the filter paper with distilled water until the PH value of the distilled water used for testing the PH test paper is neutral, that is, the hydrofluoric acid is washed clean.

[0051] S106: Pour the carbon powder on the filter paper into an empty beaker with a weight of G1 with distilled water, and then put the beaker containing the mixture of carbon powder and distilled water into an oven and bake until the constant weight G2; This step pours the carbon powder into the beaker with distilled water, and removes the water by drying in the oven to obtain pure carbon powder.

[0052] S107: Calculate the contents of silicon and carbon according to the formula.

[0053] ; Si% = 100% - C%; Wherein, C% represents the percentage content of carbon in the silicon-carbon powder with a weight of M, Si% represents the percentage content of silicon in the silicon-carbon powder with a weight of M, and G2 represents the total weight of the beaker and the carbon powder.

[0054] The contents of silicon and carbon are calculated by the above formula.

[0055] The test method of Comparative Example 1 is as follows: refer to the specification of Comparative Example 1

[0034] -

[0102] paragraphs.

[0056] Effect verification The technical effect of the carbon content test method of the high-carbon silicon-carbon material in Examples 1-7 is verified by comparative experiments, as shown in Tables 1 and 2.

[0057] Table 1 Comparison of C content test results of different examples Table 2 Comparison of C content test results in different examples Next, a sample was selected for repeated measurements at different time points, as shown in Table 3.

[0058] Table 3 Comparison of C content test results in different examples at different test times Day 1 Day 2 Day 3 Day 4 Day 5 Example 1 48.59% 48.64% 48.44% 48.87% 48.23% Example 2 48.17% 49.16% 48.96% 47.98% 47.58% Example 3 48.44% 48.35% 49.29% 48.64% 48.59% Example 4 49.55% 49.57% 48.96% 48.72% 48.44% Example 5 46.78% 45.97% 46.34% 45.74% 46.12% Example 6 48.50% 47.66% 47.99% 48.66% 47.35% Example 7 46.99% 46.72% 47.10% 47.46% 46.84% Combining Tables 1, 2, and 3, we can obtain the following conclusions after system testing and analysis: (1) Selection of calibration materials: Experimental data show that using a material with a carbon content similar to that of the sample as a calibration standard can significantly improve detection accuracy. Taking the test of silicon-carbon anode materials with different carbon content gradients as an example, when using calibration materials with matching carbon content, the relative error of the test results effectively reduces the systematic error caused by standard differences compared to randomly selecting calibration materials.

[0059] (2) Optimization of the sample addition sequence: After comparing various sample addition methods, it was found that adding the sample to the middle of the flux achieved the best test results. Compared with adding the sample first or last, this sample addition sequence reduced the relative standard deviation (RSD) of the test data to below 1%, significantly reducing the data fluctuation range and effectively ensuring the reliability of the test data.

[0060] (3) Stability Verification: Repeated verification was conducted at multiple time intervals over a continuous week. The results showed that Example 1 can effectively overcome the poor stability and low precision issues of traditional detection. Test data showed that the average error of the detection results at different time intervals was controlled within ±1%, fully demonstrating that this solution has good stability and high precision advantages in practical applications and can meet the strict requirements for carbon content detection of silicon-carbon negative electrode materials.

[0061] (4) Efficient test verification: Compared with the test method used in comparative example 1, the present invention adopts a high-frequency infrared carbon-sulfur analyzer, which takes only 3-5 minutes to test a single sample and can support batch continuous testing, significantly improving the test efficiency. In addition, the detection sensitivity is as high as ppm level, the degree of automation is high, which can reduce human operation errors and has high test accuracy, providing a powerful analytical means for the quality control of silicon-carbon materials. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principles of the present invention. These improvements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for testing the carbon content of high-carbon silicon-carbon materials, characterized in that: The steps include: S1 Preparation: Prepare the high-frequency infrared carbon-sulfur analyzer, the ceramic crucible and gas supply system, standard substances, flux and samples; S2 calibration and standard sample test: Use standard substances to calibrate the carbon content. After the calibration is completed, perform standard sample test. After the standard sample test data is stable for multiple consecutive times, the sample test can be performed. S3 sample test: S31 Heating and Reaction: Place weighed flux and sample in a ceramic crucible, then place the ceramic crucible in a high-frequency infrared carbon-sulfur analyzer. Start the high-frequency infrared carbon-sulfur analyzer and heat the flux and sample until they are completely melted. While heating, start the gas supply system. The carbon element in the sample reacts with the oxygen introduced and is released in the form of CO2. S32 detection: Detect the generated CO2 and obtain the test data of the carbon content in the sample, specifically: S321: The generated CO2 gas enters the infrared detector, which uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2; S322: The high-frequency infrared carbon-sulfur analyzer first integrates the electrical signal output by the infrared detector, then converts it to obtain the concentration of CO2, and finally calculates the carbon content test data in the sample based on the concentration of CO2.

2. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 1, characterized in that: In S1, the standard substance includes one of GBW-11111, GSB 06-2181-2008-6, and EDTA; the flux includes one of iron, tin, tungsten, and copper, or a combination of more; the surface of the ceramic crucible is cleaned and dried before use; after the preparatory work is completed, a leak test is required, and calibration can only be prepared after the leak test passes.

3. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 1, wherein: Said S2 specifically comprises the following steps: S21 carbon content calibration: selecting a suitable standard substance; inputting the carbon content of the standard substance into the high-frequency infrared carbon-sulfur analyzer; placing the weighed standard substance in a ceramic crucible, then placing the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, starting the high-frequency infrared carbon-sulfur analyzer, and comparing and calibrating the carbon content of the standard substance detected by the high-frequency infrared carbon-sulfur analyzer with the carbon content of the input standard substance; S22 Standard sample test: After calibration is completed, the same standard substance is used again to perform the standard sample test. The test conditions of each standard sample test are consistent. Conduct standard sample tests continuously and observe the stability of the standard sample test data; If the fluctuation of the standard sample test data for 5-6 consecutive times is within the allowable error range, the calibration is considered valid and the data is stable, and sample testing can be carried out; otherwise, it is necessary to recalibrate or check whether there are any problems with the high-frequency infrared carbon and sulfur analyzer and the operation process.

4. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 1, wherein: In S31, the flux is a combination of at least two of iron, tin, tungsten, and copper; the flux and sample are placed on a ceramic crucible in a stacked manner, and a sandwich stacking order is adopted, i.e., flux-sample-flux.

5. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 1, characterized in that: The S31 specifically includes the following steps: S31.1: First, weigh flux 1 in a ceramic crucible. Then weigh the sample and stack it on top of flux 1. Finally, weigh the flux again and stack flux 2 on top of the sample. S31.2: Place the ceramic crucible into the high-frequency infrared carbon-sulfur analyzer, start the high-frequency infrared carbon-sulfur analyzer for heating, and start the gas supply system while heating.

6. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 5, characterized in that: In said S31.1, flux 1 is at least one of iron, tin, tungsten and copper, and 0.40-1.20 g of flux 1 is weighed; flux 2 is at least one of iron, tin, tungsten and copper, and 0.40-2.00 g of flux 2 is weighed; and 0.02-0.04 g of silicon-carbon material is weighed as a sample.

7. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 5, characterized in that: In the S31.2, the high-frequency infrared carbon-sulfur analyzer heats the sample to 1600-1800°C, and the combustion time is 10-60s.

8. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 1, wherein: The gas supply system adopts dual-gas-circuit coordinated control. Specifically, the main gas circuit is equipped with a high-precision oxygen supplier, the working pressure is strictly controlled within the range of 3.0-3.5 bar, and a constant-flow oxygen supply mode is adopted with an oxygen flow rate of 2-5 L / min to ensure sufficient combustion; the auxiliary gas circuit introduces nitrogen as a carrier gas power source to achieve stable gas mixing and transportation.

9. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 1, characterized in that: The S321 specifically includes the following contents: the gas generated by the reaction in S31 is first carried by the carrier gas through a water / sulfur removal device and a filtering device for treatment to obtain treated CO2 gas, and then the treated CO2 gas enters the infrared detector. The infrared detector uses the absorption characteristics of CO2 to infrared light of a specific wavelength to measure the absorption intensity of CO2. Different concentrations of CO2 have different degrees of absorption of infrared light, and the carbon content is reflected by detecting its absorption intensity.

10. The method for testing the carbon content of high-carbon silicon-carbon materials according to claim 9, characterized in that: In the S32, nitrogen is used as a carrier gas to transport the gas generated by the reaction in S31 to a water / sulfur removal device and a filtering device for treatment.

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