Method for detecting carbon coating integrity of silicon negative electrode powder

Abstract

The invention relates to a method for detecting carbon coating integrity of silicon negative electrode powder. The silicon negative electrode powder comprises a silicon substrate and a carbon coating layer. The detection method comprises the following steps: contacting an alkaline solution with each group of silicon negative electrode powder in a sealed container; monitoring the pressure change in the container, and recording the gas pressure change rate from the reaction start to the first time range; calculating the gas production rate of the silicon negative electrode powder per unit mass according to the gas pressure change rate; and according to the gas production rate, the difference of the carbon coating completeness of the multiple groups of silicon negative electrode powder is judged. The reaction rates of the silicon negative electrode powder with different coating completeness and the alkaline solution are different, and the gas generation rates are also different, so that the real-time air pressure changes in the sealed container are also different. By monitoring the pressure change in the container in real time, real-time data recording and curve drawing can be realized, the material reaction condition can be calculated, the gas production rate and the gas production rate can be dynamically evaluated, and the coating characteristic difference identification of the silicon negative electrode powder can be realized in a quantitative manner.

Description

TECHNICAL FIELD

[0001] The application relates to a method for detecting carbon coating integrity of silicon negative electrode powder. BACKGROUND

[0002] In recent years, with the development of lithium ion battery technology, lithium ion batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Due to the great development of lithium ion batteries, the demand for high specific energy batteries in the power and energy storage markets is increasingly urgent, and advanced active materials represented by silicon have received widespread attention. Silicon materials are usually coated, and the current characterization of the differences in coating integrity of different silicon materials cannot meet the requirements of practical applications. SUMMARY

[0003] The purpose of the application is to provide a method for detecting carbon coating integrity of silicon negative electrode powder.

[0004] The embodiments of the application are implemented as follows:

[0005] The embodiments of the application provide a method for detecting carbon coating integrity of silicon negative electrode powder,

[0006] The silicon negative electrode powder comprises a silicon matrix and a carbon coating layer.

[0007] The silicon matrix comprises at least one of silicon monoxide and silicon-carbon material; and the carbon coating layer is coated on the surface of the silicon matrix.

[0008] The detection method comprises:

[0009] The alkaline solution is contacted with each group of silicon negative electrode powder in a sealed container.

[0010] The pressure change in the container is monitored, and the gas pressure change rate from the start of the reaction to the first time range is recorded.

[0011] The gas production rate of the silicon negative electrode powder per unit mass is calculated according to the gas pressure change rate.

[0012] According to the gas production rate, the differences in carbon coating integrity of the plurality of groups of silicon negative electrode powder are determined.

[0013] In the above technical solution, silicon anode powder is brought into contact with an alkaline solution in a sealed container. When the silicon substrate surface is not completely coated, the alkaline solution reacts chemically with the silicon substrate, generating gas and causing changes in the gas pressure inside the sealed container. Silicon anode powders with different coating integrity react with the alkaline solution at different rates, resulting in different gas generation rates and thus different real-time pressure changes within the sealed container. This technical solution, by monitoring pressure changes within the container, enables real-time data recording and curve plotting, calculating the material reaction status, dynamically assessing the gas generation rate and amount, and quantitatively identifying differences in the coating characteristics of silicon anode powder. The above detection method is simple to operate and has good repeatability and reproducibility. Compared to image methods, this method can directly characterize the coating condition of silicon anode powder and distinguish the coating integrity of different silicon anode powders, accurately assessing the differences in coating integrity among different silicon anode powders.

[0014] In some alternative implementations, the rate of change of gas pressure from the start of the reaction to a first time interval is recorded, including:

[0015] Record the rate of change of gas pressure from the start of the reaction to 2h to 24h.

[0016] In the above technical solution, by recording the rate of change of gas pressure within the range of 2h to 24h, the pressure change inside the container can be monitored accurately and quickly, thereby accurately assessing the coating integrity of the silicon anode powder.

[0017] In some alternative implementations, the rate of change of gas pressure from the start of the reaction to a first time interval is recorded, including:

[0018] From the start of the reaction, a rate of change in gas pressure was recorded every 2 to 12 hours.

[0019] In the above technical solution, by recording a gas pressure change rate every 2h to 12h, the pressure change inside the container can be monitored accurately and quickly, thereby accurately assessing the coating integrity of the silicon anode powder.

[0020] In some alternative implementations, the rate of change of gas pressure from the start of the reaction to a first time interval is recorded, including:

[0021] Record at least seven data points on the rate of change of gas pressure from the start of the reaction to the first time interval.

[0022] In the above technical solution, at least seven data points are recorded on the rate of change of gas pressure from the start of the reaction to the first time range, which is beneficial for accurately calculating the gas production of silicon anode powder in the container; thus, the coating integrity of silicon anode powder can be accurately assessed.

[0023] In some alternative implementations, the gas generation rate per unit mass of silicon anode powder is calculated based on the rate of change of gas pressure, including:

[0024] The gas production rate is calculated based on the rate of change of gas pressure and the ideal gas law.

[0025] In the above technical solution, the gas generation rate is calculated based on the gas pressure change rate and the ideal gas law, which can accurately calculate the gas generation rate of silicon anode powder in the container; thus, the coating integrity of silicon anode powder can be accurately evaluated.

[0026] In some alternative implementations, the differences in carbon coating integrity among multiple groups of silicon anode powders are determined based on the gas generation rate, including:

[0027] Based on the gas generation rate, determine the amount of exposed silicon substrate in multiple groups of silicon anode powders; based on the amount of exposed silicon substrate, determine the differences in carbon coating integrity among multiple groups of silicon anode powders.

[0028] In the above technical solution, when the exposed silicon substrate comes into contact with the alkaline solution in the sealed container, it will react with the residual water to generate gas. When more silicon substrate is exposed, more gas is generated, and the carbon coating integrity of the silicon anode powder is worse. Conversely, the carbon coating integrity of the silicon anode powder is better when less silicon substrate is exposed.

[0029] In some alternative implementations, monitoring pressure changes within the container includes:

[0030] The pressure change inside the container is tested every 1 minute.

[0031] In the above technical solution, by using a pressure sensor to test the pressure change inside the container every 1 minute, it is possible to accurately and in real time monitor the pressure change inside the container, thereby accurately assessing the coating integrity of the silicon anode powder.

[0032] In some alternative implementations, the silicon anode powder is sealed in a container, including:

[0033] Each group of silicon anode powder is sealed in a container and stirred; then the alkaline solution is injected to bring the two into contact. In the above technical solution, by sealing the silicon anode powder in a container and stirring it, the silicon anode powder and the alkaline solution can be fully contacted, which is beneficial for accurately calculating the gas production of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately assessed.

[0034] In some alternative implementations, the stirring rate is 150 r / min to 250 r / min.

[0035] In the above technical solution, by setting the stirring rate of silicon anode powder and alkaline solution to 150 r / min to 250 r / min, the silicon anode powder and alkaline solution can be effectively brought into full contact within this range, which is beneficial for accurately calculating the gas production of silicon anode powder in the container and thus accurately assessing the coating integrity of silicon anode powder.

[0036] In some alternative implementations, real-time monitoring of pressure changes within the container is initiated after stirring the silicon anode powder but before the alkaline solution is injected.

[0037] In the above technical solution, by starting real-time monitoring after stirring the silicon anode powder and before injecting the alkaline solution, the change in gas pressure in the container can be accurately monitored, which is beneficial for accurately calculating the gas production of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately assessed.

[0038] In some alternative embodiments, the alkaline solution includes:

[0039] Strong alkaline solution.

[0040] In the above technical solution, a strong alkaline solution is injected into the container. When the silicon substrate surface is not completely coated, the strong alkaline solution can quickly and sensitively react chemically with the silicon substrate to generate gas, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0041] In some alternative embodiments, the strong alkaline solution includes at least one of sodium hydroxide solution or potassium hydroxide solution.

[0042] In the above technical solution, sodium hydroxide solution or potassium hydroxide solution, as a strong alkaline solution, can rapidly and sensitively react chemically with the incompletely coated, exposed silicon substrate, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0043] In some alternative embodiments, the concentration of the strong base solution is 0.01 mol / L to 0.2 mol / L.

[0044] In the above technical solution, the concentration of the strong alkaline solution is 0.01 mol / L to 0.2 mol / L. Within this range, the strong alkaline solution can rapidly and sensitively react with the incompletely coated, exposed silicon substrate to generate gas, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0045] In some optional embodiments, the ratio of strong alkaline solution to silicon anode powder is (150mL~250mL): (20g~30g).

[0046] In the above technical solution, the ratio of strong alkaline solution to silicon anode powder is (150mL~250mL): (20g~30g). Within this ratio range, the strong alkaline solution and the exposed silicon substrate of the silicon anode powder can undergo a rapid and sensitive chemical reaction, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0047] In some alternative implementations, the container is kept at a constant temperature of 25°C to 30°C.

[0048] In the above technical solution, by setting the container to a constant temperature state of 25℃~30℃, it is beneficial to accurately calculate the gas generation rate of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately evaluated.

[0049] In some alternative implementations, the container is kept at a constant temperature by external liquid bath heating.

[0050] In the above technical solution, by using external liquid bath heating to achieve a constant temperature state for the container, the container can be kept at a constant temperature, which is beneficial for accurately calculating the gas generation rate of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately evaluated. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the structure of the device for detecting the integrity of carbon coating on silicon anode powder according to this application.

[0053] Icons: 100 - Detection device for the integrity of carbon coating of silicon anode powder; 110 - Container; 111 - Bottom; 120 - Liquid injection assembly; 130 - Pressure detection assembly; 121 - Pipeline; 122 - Valve; 140 - Stirring assembly; 141 - Stirring section; 142 - Drive section. Detailed Implementation

[0054] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0056] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0057] In the description of the embodiments of this application, the technical terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0058] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0059] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0060] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0061] The demand for high-energy-density batteries in the power and energy storage markets is becoming increasingly urgent, and advanced active materials, such as silicon, can be used to produce these batteries. However, silicon materials suffer from expansion issues, and coating modification is an effective measure to improve the actual performance of silicon anodes, significantly impacting the production, processing, and electrochemical performance of silicon materials. Currently, researchers lack effective methods for characterizing the integrity of the coating, and can only perform local characterization using methods such as image processing, which fails to meet the required representativeness and accuracy.

[0062] Based on this, the first aspect of this application provides a method for detecting the integrity of the carbon coating on silicon anode powder.

[0063] Silicon anode powder consists of a silicon matrix and a carbon coating layer;

[0064] The silicon substrate includes at least one of silicon suboxide and silicon-carbon materials; a carbon coating layer is coated on the surface of the silicon substrate;

[0065] The detection methods include:

[0066] The alkaline solution is brought into contact with each group of silicon anode powder in a sealed container;

[0067] Monitor the pressure changes inside the container and record the rate of gas pressure change from the start of the reaction to the first time interval;

[0068] The gas generation rate per unit mass of silicon anode powder is calculated based on the rate of change of gas pressure.

[0069] The differences in carbon coating integrity among multiple groups of silicon anode powders were determined based on the gas generation rate.

[0070] In the above technical solution, silicon anode powder is brought into contact with an alkaline solution in a sealed container. When the silicon substrate surface is not completely coated, the alkaline solution reacts chemically with the silicon substrate, generating gas and causing changes in the gas pressure inside the sealed container. Silicon anode powders with different coating integrity react with the alkaline solution at different rates, resulting in different gas generation rates and thus different real-time pressure changes within the sealed container. This technical solution, by monitoring the pressure changes inside the container in real time, enables real-time data recording and curve plotting, calculation of the material reaction, and dynamic evaluation of gas generation rate and quantity, quantitatively identifying differences in the coating characteristics of silicon anode powder. The above detection method is simple to operate and has good repeatability and reproducibility. Compared to image methods, this method can directly characterize the coating condition of silicon anode powder and distinguish the coating integrity of different silicon anode powders, accurately assessing the differences in coating integrity among different silicon anode powders.

[0071] In the above technical solutions, "silicon-carbon material" has a well-known meaning in the art and is generally understood as a composite material of silicon and carbon. Exemplarily, it may include porous carbon materials and silicon materials. Further exemplaryly, in some embodiments of this application, silicon-carbon materials can be formed by depositing amorphous silicon inside or on the surface of porous carbon. Further optionally, the particle size of the above-mentioned "silicon-carbon material" is usually in the nanometer range, so silicon-carbon nanomaterials can be selected in some embodiments of this application.

[0072] In some embodiments of this application, the rate of change of gas pressure from the start of the reaction to a first time interval is recorded, including:

[0073] Record the rate of change of gas pressure from the start of the reaction to 2h to 24h.

[0074] In the above technical solution, by recording the rate of change of gas pressure from the start of the reaction to 2h to 24h, the pressure change inside the container can be monitored accurately and quickly, thereby accurately assessing the coating integrity of the silicon anode powder.

[0075] Exemplary, in some embodiments of this application, the above-mentioned recording of the rate of change of gas pressure from the start of the reaction to a first time range includes:

[0076] Record the rate of change of gas pressure within the range of 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, or 24h.

[0077] Furthermore, in some embodiments of this application, recording the rate of change of gas pressure from the start of the reaction to a first time interval includes:

[0078] From the start of the reaction, a rate of change in gas pressure was recorded every 2 to 12 hours.

[0079] In the above technical solution, by recording a gas pressure change rate every 2h to 12h from the start of the reaction, the pressure change inside the container can be monitored accurately and quickly, thereby accurately assessing the coating integrity of the silicon anode powder.

[0080] For example, recording the rate of change of gas pressure from the start of the reaction to a first time interval includes:

[0081] Record a rate of change of gas pressure every 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h.

[0082] Furthermore, in some embodiments of this application, recording the rate of change of gas pressure from the start of the reaction to a first time interval includes:

[0083] Record at least seven data points on the rate of change of gas pressure from the start of the reaction to the first time interval.

[0084] In the above technical solution, at least seven data points are recorded on the rate of change of gas pressure from the start of the reaction to the first time range, which is beneficial for accurately calculating the gas generation rate of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately evaluated.

[0085] Exemplarily, in some embodiments of this application, recording the rate of change of gas pressure from the start of the reaction to a first time interval includes:

[0086] The data for the rate of change of gas pressure within the first time range are recorded as 7, 8, 9, 10, 11, or 12.

[0087] Furthermore, in some embodiments of this application, the gas generation rate per unit mass of silicon anode powder is calculated based on the rate of change of gas pressure, including:

[0088] The gas production rate is calculated based on the rate of change of gas pressure and the ideal gas law.

[0089] In the above technical solution, the gas generation rate is calculated based on the gas pressure change rate and the ideal gas law, which can accurately calculate the gas generation rate of silicon anode powder in the container; thus, the coating integrity of silicon anode powder can be accurately evaluated.

[0090] Exemplary examples are found in some embodiments of this application:

[0091] When the carbon coating integrity of silicon anode powder is low or surface defects are present, the exposed silicon substrate will react with residual water vapor generated by steam (Si + 2OH-). - +H₂O→SiO₃ 2- +2H2↑), based on the ideal gas law pV=nRT (p-pressure, V-volume, n-amount of substance, R-gas constant, T-temperature); when the temperature and volume are constant, the ratio of gas pressure is the same as the ratio of the amount of substance contained. The amount of gas produced can be calculated by the change of pressure in the sealed container, thereby identifying the difference in the integrity of the carbon coating of silicon anode.

[0092] Furthermore, in some embodiments of this application, the difference in carbon coating integrity among multiple groups of silicon anode powders is determined based on the gas generation rate, including:

[0093] Based on the gas generation rate, determine the amount of exposed silicon substrate in multiple groups of silicon anode powders; based on the amount of exposed silicon substrate, determine the differences in carbon coating integrity among multiple groups of silicon anode powders.

[0094] In the above technical solution, when the exposed silicon substrate comes into contact with the alkaline solution in the sealed container, it will react with the residual water to generate gas (as shown in the aforementioned reaction equation); when more silicon substrate is exposed, more gas is generated, and the carbon coating integrity of the silicon anode powder is worse; conversely, the carbon coating integrity of the silicon anode powder is better.

[0095] In some embodiments of this application, monitoring pressure changes within the container includes:

[0096] The pressure change inside the container is tested every 1 minute.

[0097] In the above technical solution, by using a pressure sensor to test the pressure change inside the container every 1 minute, it is possible to accurately and in real time monitor the pressure change inside the container, thereby accurately assessing the coating integrity of the silicon anode powder.

[0098] Optionally, in some embodiments of this application, a pressure sensor can be used to test the pressure change inside the container every 1 minute, which provides higher accuracy.

[0099] Furthermore, in some embodiments of this application, contacting the alkaline solution with each group of the silicon anode powder in a sealed container includes:

[0100] Each group of silicon anode powder is sealed in a container and stirred; then an alkaline solution is injected to bring the two into contact. In the above technical solution, by sealing the silicon anode powder in a container and stirring it, the silicon anode powder and the alkaline solution can be fully contacted, which is beneficial for accurately calculating the gas generation rate of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately evaluated.

[0101] Furthermore, in some embodiments of this application, the stirring rate is 150 r / min to 250 r / min.

[0102] In the above technical solution, by setting the stirring rate of silicon anode powder and alkaline solution to 150 r / min to 250 r / min, the silicon anode powder and alkaline solution can be effectively brought into full contact within this range, which is beneficial for accurately calculating the gas production of silicon anode powder in the container and thus accurately assessing the coating integrity of silicon anode powder.

[0103] For example, in some embodiments of this application, the stirring rate is 150 r / min, 152 r / min, 155 r / min, 158 r / min, 160 r / min, 165 r / min, 168 r / min, 170 r / min, 175 r / min, 180 r / min, 185 r / min, 190 r / min, 195 r / min, 200 r / min, 210 r / min, 220 r / min, 225 r / min, 230 r / min, 235 r / min, 240 r / min, 245 r / min, 250 r / min, or a range between any two of the aforementioned values.

[0104] Furthermore, in some embodiments of this application, real-time monitoring of pressure changes inside the container is initiated after stirring the silicon anode powder but before the alkaline solution is injected.

[0105] In the above technical solution, by starting real-time monitoring after stirring the silicon anode powder and before injecting the alkaline solution, the change in gas pressure in the container can be accurately monitored, which is beneficial for accurately calculating the gas production of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately assessed.

[0106] Furthermore, in some embodiments of this application, injecting the alkaline solution into the container includes:

[0107] Inject the strong alkaline solution into the container.

[0108] In the above technical solution, a strong alkaline solution is injected into the container. When the silicon substrate surface is not completely coated, the strong alkaline solution can quickly and sensitively react chemically with the silicon substrate to generate gas, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0109] Furthermore, in some embodiments of this application, the strong alkaline solution includes at least one of sodium hydroxide solution or potassium hydroxide solution.

[0110] In the above technical solution, sodium hydroxide solution or potassium hydroxide solution, as a strong alkaline solution, can rapidly and sensitively react chemically with the incompletely coated, exposed silicon substrate, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0111] For example, in some embodiments of this application, the strong alkaline solution is either a sodium hydroxide solution or a potassium hydroxide solution; or in some embodiments of this application, the strong alkaline solution is a mixture of sodium hydroxide solution and potassium hydroxide solution; optionally, in some embodiments of this application, the sodium hydroxide solution and potassium hydroxide solution can be mixed in any proportion.

[0112] Furthermore, in some embodiments of this application, the concentration of the strong alkali solution is 0.01 mol / L to 0.2 mol / L.

[0113] In the above technical solution, the concentration of the strong alkaline solution is 0.01 mol / L to 0.2 mol / L. Within this range, the strong alkaline solution can rapidly and sensitively react with the incompletely coated, exposed silicon substrate to generate gas, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation rate of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0114] For example, in some embodiments of this application, the concentration of the strong alkali solution is 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, or a range between any two of the aforementioned values.

[0115] Furthermore, in some embodiments of this application, the ratio of strong alkaline solution to silicon anode powder is (150mL~250mL): (20g~30g).

[0116] In the above technical solution, the ratio of strong alkaline solution to silicon anode powder is (150mL~250mL):(20g~30g). Within this ratio range, the strong alkaline solution and the exposed silicon substrate of the silicon anode powder can undergo a rapid and sensitive chemical reaction, causing a change in the gas pressure inside the sealed container. This facilitates the accurate calculation of the gas generation of the silicon anode powder in the container, thereby enabling precise assessment of the coating integrity of the silicon anode powder.

[0117] For example, in some embodiments of this application, the ratio of strong alkaline solution to silicon anode powder is 150mL:20g, 160mL:21g, 170mL:22g, 180mL:23g, 190mL:24g, 200mL:25g, 210mL:26g, 220mL:27g, 230mL:28g, 245mL:29g, 250mL:30g, or any range between two of the aforementioned values.

[0118] Furthermore, in some embodiments of this application, the container is in a constant temperature state; the temperature is 25°C to 30°C.

[0119] In the above technical solution, by setting the container to a constant temperature state of 25℃~30℃, it is beneficial to accurately calculate the gas generation rate of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately evaluated.

[0120] For example, in some embodiments of this application, the container is in a constant temperature state; the temperature is a temperature value of 25°C, 26°C, 27°C, 28°C, 29°C, 30°C or any two of the aforementioned values.

[0121] Furthermore, in some embodiments of this application, the container is kept at a constant temperature by external liquid bath heating.

[0122] In the above technical solution, by using external liquid bath heating to achieve a constant temperature state for the container, the container can be kept at a constant temperature, which is beneficial for accurately calculating the gas production of silicon anode powder in the container; thus, the coating integrity of silicon anode powder can be accurately assessed.

[0123] For example, in some embodiments of this application, the container is kept at a constant temperature by external water bath heating or oil bath heating.

[0124] Reference Figure 1 In some embodiments of this application, a detection device 100 for detecting the integrity of carbon coating of silicon anode powder can be used to perform the aforementioned method for detecting the integrity of carbon coating of silicon anode powder.

[0125] In some embodiments of this application, a device 100 for detecting the integrity of carbon coating on silicon anode powder includes:

[0126] Container 110 is used to seal silicon anode powder;

[0127] Liquid injection assembly 120; liquid injection assembly 120 is connected to container 110 and is used to inject an alkaline solution into container 110; and

[0128] Pressure detection component 130; used for real-time monitoring of pressure changes inside container 110.

[0129] In the above technical solution, container 110 is used to seal silicon anode powder; liquid injection component 120 is connected to container 110 and used to inject alkaline solution into container 110; when liquid injection component 120 injects alkaline solution into container 110, the silicon anode powder in the sealed container comes into contact with the alkaline solution. When the silicon substrate surface is not completely coated, the alkaline solution will react chemically with the silicon substrate to generate gas, causing the gas pressure inside the sealed container to change. Gas pressure detection component 130 can monitor the pressure change inside container 110 in real time. Since the reaction rate of silicon anode powder with different coating integrity is different with alkaline solution, the gas generation rate is also different, and thus the real-time gas pressure change in the sealed container is also different. The above technical solution, by monitoring the pressure change inside the container in real time, can realize real-time data recording and curve plotting, calculate the material reaction situation, dynamically evaluate the gas generation rate and gas generation amount, and quantitatively identify the differences in coating characteristics of silicon anode powder. The above-mentioned detection method is simple to operate and has good repeatability and reproducibility. Compared with the image method, this method can directly characterize the coating of silicon anode powder and distinguish the coating integrity of different silicon anode powders. It can quantitatively evaluate the quality of coating integrity of different silicon anode powders.

[0130] Furthermore, in some embodiments of this application, the air pressure detection component 130 is an air pressure sensor.

[0131] In the above technical solution, by setting the gas pressure detection component 130 as a gas pressure sensor, the gas pressure change inside the sealed container can be monitored with the help of a high-precision gas pressure sensor. This enables real-time data recording and curve plotting, calculation of material reaction, dynamic evaluation of gas production rate and amount, and quantitative identification of differences in silicon material coating characteristics. The operation is simple, and the repeatability and reproducibility are good.

[0132] Furthermore, in some embodiments of this application, the liquid injection assembly 120 is connected to the container 110 via a pipe 121, and a valve 122 is provided on the pipe 121.

[0133] In the above technical solution, the liquid injection component 120 is connected to the container 110 through the pipe 121. The pipe 121 is equipped with a valve 122. By opening or closing the valve 122, the injection or cessation of alkaline solution into the sealed container 110 can be achieved, so as to ensure that the container 110 remains sealed throughout the reaction process. Thus, the gas production rate can be accurately calculated based on the ideal gas state equation according to the gas pressure change rate, which is beneficial for accurately calculating the gas production rate of silicon anode powder in the container. This allows for accurate assessment of the coating integrity of the silicon anode powder.

[0134] Furthermore, in some embodiments of this application, the detection device 100 for the integrity of carbon coating of silicon anode powder includes: a stirring assembly 140; the stirring assembly 140 includes a stirring section 141; the stirring section 141 extends into the interior of the container 110 and is close to the bottom 111 of the container 110.

[0135] In the above technical solution, by setting the stirring component 140, the silicon anode powder in the container 110 can be stirred, thereby allowing the exposed silicon substrate of the silicon anode powder to fully contact the alkaline solution in the container 110, thereby improving the sufficiency of the reaction, improving the accuracy of gas pressure change monitoring, and further facilitating the accurate calculation of the gas production of the silicon anode powder in the container; thus, the coating integrity of the silicon anode powder can be accurately assessed.

[0136] Furthermore, in the above technical solution, since the silicon anode powder is placed at the bottom of the container 110, by setting the stirring part 141 to extend into the interior of the container 110 and close to the bottom 111 of the container 110, it is further beneficial to improve the stirring effect, thereby improving the reaction sufficiency and improving the accuracy of the coating integrity detection of the silicon anode powder.

[0137] Further optionally, in some embodiments of this application, the stirring assembly 140 described above further includes a drive unit 142. The drive unit 142 is tractively connected to the stirring unit 141 and is used to drive the stirring unit 141 to rotate. By rotating, the stirring unit 141 stirs the silicon anode powder inside the container 110.

[0138] Further optionally, in some embodiments of this application, the stirring section 141 described above rotates relative to an axis perpendicular to the bottom of the container 110. For example, the figure shows the axis L of the stirring section 141, which rotates relative to the axis L to stir the silicon anode powder inside the container 110.

[0139] Further alternatively, in some embodiments of this application, the aforementioned driving unit 142 may be a driving component such as a motor. When the motor rotates, it can drive the stirring unit 141 to rotate, thereby achieving stirring of the silicon anode powder inside the container 110.

[0140] For example, in some embodiments of this application, when the aforementioned detection device 100 for the integrity of carbon coating of silicon anode powder is applied to the detection method for the integrity of carbon coating of silicon anode powder, it can be operated according to the following steps:

[0141] Weigh a certain mass of the silicon anode powder to be tested and transfer it to container 110;

[0142] Prepare an alkaline solution of a certain concentration and transfer it to the automatic liquid injection assembly 120, then seal the entire detection device 100 for the integrity of carbon coating of silicon anode powder.

[0143] Start the stirring assembly 140 and the air pressure detection assembly 130 to record the pressure value inside the sealed container 110 in real time;

[0144] Open valve 122 to completely inject the alkaline solution into container 110, then close valve 122 and record the pressure change inside the bottle in real time; and record the rate of change of gas pressure within the first time range.

[0145] The gas production per unit mass of silicon anode powder is calculated based on the rate of change of gas pressure.

[0146] The integrity of the carbon coating of silicon anode powder is determined based on the gas production rate.

[0147] The following specific embodiments are provided to better illustrate this application.

[0148] Example 1

[0149] A method is provided for testing the integrity of carbon coating on silicon anode powder:

[0150] Three silicon anode powders, A1, A2, and A3, were used as test samples. The silicon substrates of A1, A2, and A3 are all silicon suboxide. The same coating process was used to coat carbon onto the surface of the silicon suboxide. The difference lies in the carbon content of the three. The carbon contents of A1, A2, and A3 are 4.6%, 2.5%, and 0.8%, respectively. A1 is a standard sample, while A2 and A3 are special samples with medium and low carbon contents.

[0151] use Figure 1 The device shown is used to detect the carbon coating integrity of silicon anode powder and to determine the differences in carbon coating integrity among A1, A2, and A3.

[0152] Follow these steps to test:

[0153] First, weigh 25g of powder from each of the three samples A1, A2, and A3 and place them in a 250ml container. Then, weigh 200mL of the prepared 0.1M potassium hydroxide solution and add it to the injection assembly. Seal the entire device. Start the stirring assembly and the pressure sensor, open the valve of the injection assembly, and inject all the alkaline solution into the container. Then close the valve. Using the pressure sensor, test the pressure change in the container every 1 minute and detect the rate of gas pressure change over 24 hours. For the first 12 hours, detect the rate of gas pressure change every 2 hours; for the next 12 hours, detect the rate of gas pressure change every 12 hours. The amount of gas pressure change over 24 hours is shown in Table 1. The gas production per unit mass of material is shown in Table 3. Record the seven data points of the pressure change rate over 24 hours, as shown in Table 2. The gas production rate is shown in Table 4.

[0154] Table 1

[0155]

[0156] Table 2

[0157]

[0158] Table 3

[0159]

[0160] Table 4

[0161]

[0162] It can be seen from the above table that:

[0163] There are obvious differences in the gas generation rates of the three silicon anode powder materials A1, A2, and A3; the greater the gas generation amount per unit mass of the silicon anode powder material, the greater the gas generation rate, indicating that the more the silicon matrix of the silicon anode powder material is exposed, and the poorer the carbon coating integrity of the silicon anode powder material. It can be seen from the above data that the gas generation rate A1 < A2 < A3; therefore, the coating integrity of the samples A1 > A2 > A3.

[0164] Example 2

[0165] Provide a method for testing the carbon coating integrity of silicon anode powder materials:

[0166] Take three silicon anode powder materials B1, B2, and B3 as test samples; the silicon matrices of B1, B2, and B3 are all silicon-carbon nanomaterials; the carbon coating is on the surface of the silicon-carbon nanomaterials. The total carbon contents of the three are close, being 54.2%, 54.5%, and 54.0% respectively, and the difference is that the coating processes used for the three are different. The coating processes of B1, B2, and B3 are single, double, and triple vapor depositions in sequence.

[0167] Adopt Figure 1 The detection device shown for the carbon coating integrity of silicon anode powder materials to conduct detection and judge the differences in the carbon coating integrity of B1, B2, and B3.

[0168] Detect according to the following steps:

[0169] First, weigh 25g of powder from each of the three samples B1, B2, and B3 and place them in a 250ml container. Then, weigh 200mL of the prepared 0.1M sodium hydroxide solution and add it to the injection assembly. Seal the entire device. Start the stirring assembly and the pressure sensor, open the valve of the injection assembly, and inject all the alkaline solution into the container. Then close the valve. Using the pressure sensor, test the pressure change in the container every 1 minute and detect the rate of gas pressure change over 24 hours. For the first 12 hours, detect the rate of gas pressure change every 2 hours; for the next 12 hours, detect the rate of gas pressure change every 12 hours. The amount of gas pressure change over 24 hours is shown in Table 5. The gas production per unit mass of material is shown in Table 7. Record the seven data points of the pressure change rate over 24 hours, as shown in Table 6. The gas production rate is shown in Table 8.

[0170] Table 5

[0171]

[0172] Table 6

[0173]

[0174] Table 7

[0175]

[0176] Table 8

[0177]

[0178] As can be seen from the table above:

[0179] The gas generation rates of the three silicon anode powders, B1, B2, and B3, show significant differences. A higher gas generation rate per unit mass of silicon anode powder indicates a greater exposure of the silicon matrix and poorer carbon coating integrity. The data shows that the gas generation rate is B1 > B2 > B3; therefore, the carbon coating integrity of sample B1 is higher. <B2<B3。

[0180] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for detecting the integrity of carbon coating on silicon anode powder, characterized in that, The silicon anode powder comprises a silicon matrix and a carbon coating layer; The silicon substrate includes at least one of silicon suboxide and silicon-carbon materials; the carbon coating layer covers the surface of the silicon substrate. The detection method includes: The alkaline solution is brought into contact with each group of silicon anode powder in a sealed container; Monitor the pressure changes inside the container and record the rate of gas pressure change from the start of the reaction to the first time interval; The gas generation rate per unit mass of the silicon anode powder is calculated based on the gas pressure change rate. Based on the gas generation rate, the differences in carbon coating integrity among multiple groups of silicon anode powders are determined.

2. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 1, characterized in that, The recording of the rate of change of gas pressure from the start of the reaction to the first time range includes: Record the rate of change of gas pressure from the start of the reaction to 2h to 24h.

3. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-2, characterized in that, The recording of the rate of change of gas pressure from the start of the reaction to the first time range includes: From the start of the reaction, a rate of change in gas pressure was recorded every 2 to 12 hours.

4. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-3, characterized in that, The recording of the rate of change of gas pressure from the start of the reaction to the first time range includes: Record at least seven data points on the rate of change of gas pressure from the start of the reaction to the first time interval.

5. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-4, characterized in that, The calculation of the gas generation rate per unit mass of the silicon anode powder based on the gas pressure change rate includes: The gas production rate is calculated based on the gas pressure change rate and the ideal gas law.

6. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-5, characterized in that, The step of determining the differences in carbon coating integrity among multiple groups of silicon anode powders based on the gas generation rate includes: Based on the gas generation rate, determine the amount of exposed silicon substrate in multiple groups of silicon anode powders; based on the amount of exposed silicon substrate, determine the difference in carbon coating integrity in multiple groups of silicon anode powders.

7. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 1, characterized in that, The monitoring of pressure changes within the container includes: The pressure change inside the container is tested every 1 minute.

8. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-7, characterized in that, The step of contacting the alkaline solution with each group of silicon anode powders in a sealed container includes: Each group of silicon anode powder is sealed in a container and stirred; then the alkaline solution is injected to bring the two into contact.

9. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 8, characterized in that, The stirring rate is 150 r / min to 250 r / min.

10. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 8, characterized in that, The real-time monitoring of pressure changes inside the container is initiated after the silicon anode powder is stirred but before the alkaline solution is injected.

11. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-10, characterized in that, The alkaline solution comprises: Strong alkaline solution.

12. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 11, characterized in that, The strong alkaline solution includes at least one of sodium hydroxide solution or potassium hydroxide solution.

13. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 11, characterized in that, The concentration of the strong alkali solution is 0.01 mol / L to 0.2 mol / L.

14. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 11, characterized in that, The ratio of the strong alkaline solution to the silicon anode powder is (150mL~250mL): (20g~30g).

15. The method for detecting the integrity of carbon coating on silicon anode powder according to any one of claims 1-14, characterized in that, The container is kept at a constant temperature; the temperature is 25℃~30℃.

16. The method for detecting the integrity of carbon coating on silicon anode powder according to claim 15, characterized in that, The container is kept at a constant temperature by using an external liquid bath for heating.

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