Carbonization method and carbonization process for producing lithium battery negative electrode material

Abstract

The application relates to the technical field of carbonization method optimization, in particular to a carbonization method and a carbonization process for producing a lithium battery negative electrode material, which comprises the following steps: collecting and preprocessing related data in a carbonization process; evaluating the influence of a graphite preliminary raw material on a carbonization effect; evaluating the adjustment range of a target graphite preliminary raw material in a first temperature stage; analyzing whether a nitrogen filling rate in a current stage is appropriate; and adjusting the nitrogen filling rate in different temperature stages. The application aims to accurately adjust the nitrogen flow in different temperature stages of the graphite preliminary raw material in a high-temperature carbonization process, and improve the carbonization effect of the graphite negative electrode material.

Description

Technical Field

[0001] This application relates to the field of carbonization method optimization technology, specifically to a carbonization method and process for the production of lithium battery anode materials. Background Technology

[0002] Lithium-ion batteries are widely used due to their long lifespan, high power handling capacity, and strong low-temperature adaptability. Graphite anode materials, as a core component of lithium-ion batteries, are also widely used in commercial lithium-ion batteries. However, the high-temperature carbonization process significantly affects the preparation of graphite anode materials. Therefore, developing a carbonization process for anode material preparation to improve the performance of lithium-ion battery anode materials is of great significance.

[0003] Current technologies typically involve sintering and carbonizing graphite anode materials in a rotary kiln. However, during the carbonization process, these technologies usually employ a fixed gas filling rate, failing to adequately consider the differences in composition and particle size that arise after multiple preliminary processes such as raw material pretreatment, granulation, and pre-carbonization. Furthermore, the volatile components in the material dynamically change over time. Using a fixed gas filling rate for graphite anode material carbonization cannot adapt to the actual carbonization requirements of different batches of material, thus affecting the preparation effect and resulting in poor carbonization. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a carbonization method and process for producing lithium battery anode materials, the specific technical solution of which is as follows:

[0005] In a first aspect, one embodiment of this application provides a carbonization method for producing lithium battery anode materials, the method comprising the following steps:

[0006] Artificial graphite is subjected to raw material crushing, ball milling and screening, granulation, coating and pre-carbonization to obtain graphite pre-raw material, which is then subjected to high-temperature carbonization treatment; during the high-temperature carbonization process, the oxygen and material temperature in the kiln at each temperature stage of the carbonization process of the target graphite pre-raw material are collected and pretreated.

[0007] Clustering was performed based on the differences in graphitization degree of multiple anode materials before and after carbonization in historical production processes; the cluster with the largest internal element mean was denoted as a good cluster.

[0008] The dispersion and average degree of graphitization of the negative electrode material corresponding to all elements in the good cluster before carbonization and the difference between it and other clusters are analyzed to determine the material influence index of the good cluster.

[0009] And combined with the difference in graphitization degree between the target graphite raw material and the graphite raw material corresponding to the good cluster element, the flow rate adjustment range of the target graphite raw material in the first temperature stage is constructed.

[0010] The nitrogen gas filling imbalance degree of the target graphite raw material in the first temperature stage is constructed by using the oxygen dispersion degree of the target graphite raw material in the first temperature stage and the temperature mean difference between the target graphite raw material and the negative material corresponding to the good cluster element before carbonization.

[0011] The nitrogen gas filling rate of the target graphite raw material under different temperature stages is adjusted by combining the flow rate adjustment range and the nitrogen gas filling imbalance degree.

[0012] Preferably, in the coating operation, the graphite negative material is coated with coating pitch, the particle size of the coating pitch is 5um, and the addition amount of the coating pitch is 5%.

[0013] Preferably, the temperature in the pre-carbonization operation is 300 degrees, the holding time is 2 hours, and the heating rate is .

[0014] Preferably, in the high-temperature carbonization process, first, heat to 900 degrees and hold for 2h, then heat to 1000 degrees and hold for 4h, then heat to 1100 degrees and hold for 8h, and finally heat to 1200 degrees, then naturally cool to room temperature, complete carbonization, and obtain carbonized material; that is, the temperature stage in the high-temperature carbonization process includes the heating-holding-heating-holding-heating-holding-heating and cooling stages.

[0015] Preferably, the clustering of the difference in graphitization degree of the negative material before and after carbonization in the historical production process includes:

[0016] For the u-th negative material in the historical production process, the first product of the u-th negative material is calculated ; wherein, is the graphitization degree of the u-th negative material after carbonization; is the absolute difference between the graphitization degrees of the material before and after carbonization of the u-th negative material; and the first products calculated for all negative materials in the historical production process are clustered.

[0017] Preferably, the method for determining the material influence index of the good cluster is:

[0018] The mean and dispersion of the graphitization degree of the negative material corresponding to all elements in the good cluster before carbonization are calculated respectively, and are denoted as the initial mean and initial dispersion of the good cluster respectively.

[0019] In the same way, the initial mean value of each cluster is calculated, the absolute difference between the initial mean value of the good cluster and the initial mean value of each cluster is calculated, and the cumulative sum of all absolute differences is recorded as the first sum value of the good cluster;

[0020] Material impact index of the good cluster ; in the formula, C is the initial dispersion value of the good cluster; B is the first sum value of the good cluster; is a preset parameter adjustment coefficient, in order to avoid the denominator being 0.

[0021] Preferably, the construction method of the flow rate adjustment range of the target graphite preparation raw material in the first temperature stage is:

[0022] The difference between the graphitization degree of the target graphite preparation raw material and the graphitization degree of the negative electrode material corresponding to each element in the good cluster before carbonization is calculated respectively, and the difference closest to 0 among all the differences is recorded as the first difference value of the target graphite preparation raw material in the first temperature stage;

[0023] The flow rate adjustment range is positively correlated with the first difference value and the material impact index respectively.

[0024] Preferably, the construction method of the nitrogen filling imbalance degree of the target graphite preparation raw material in the first temperature stage is:

[0025] The dispersion degree of all oxygen data collected by the i th graphite preparation raw material in the first temperature stage is calculated and recorded as the first dispersion value of the oxygen data;

[0026] In the first temperature stage, the mean value of all material temperatures collected by the target graphite preparation raw material is calculated, and the mean value of all material temperatures collected by the negative electrode material corresponding to each element in the good cluster during the carbonization process is calculated;

[0027] The sum of the difference between the mean value of the material temperature of the target graphite preparation raw material and the mean value of the material temperature of the negative electrode material corresponding to each element in the good cluster during the carbonization process is recorded as the second sum value of the target graphite preparation raw material in the first temperature stage;

[0028] The first dispersion value and the second sum value are summed to obtain the nitrogen filling imbalance of the target graphite preparation raw material in the first temperature stage.

[0029] Preferably, the method for adjusting the nitrogen filling rate of the target graphite preparation raw material under different temperature stages is:

[0030]

[0031] In the formula, ​is the nitrogen filling rate of the i th graphite raw material at the j th temperature stage after adjustment; , are respectively the preset initial nitrogen filling rates of the i th graphite raw material at the j th and j-1 th temperature stages; is a preset adjustment parameter; , are respectively the flow rate adjustment range and the nitrogen filling imbalance degree of the i th graphite raw material at the j th and j-1 th temperature stages; is a normalization function.

[0032] In a second aspect, another embodiment of the present application further provides a carbonization process for producing a lithium battery negative electrode material, which comprises the following steps: crushing raw materials, ball milling, screening, granulating, coating and pre-carbonization of artificial graphite, and then high-temperature carbonization treatment; and in the process of high-temperature carbonization treatment, the nitrogen filling rate at different temperature stages is adjusted by using the above-mentioned carbonization method.

[0033] The present application has at least the following beneficial effects:

[0034] The present application takes the difference in graphitization degree before and after carbonization as a clustering feature, which can objectively divide historical batches into different quality levels; the cluster with the largest average difference is defined as a "good cluster", which can directly lock the optimal process window, providing a precise benchmark for subsequent evaluation of raw material differences, and avoiding the deviation caused by artificial setting standards. The present application uses the dispersion degree of the initial graphitization degree of the good cluster and the difference between clusters to construct a "material influence index", which can quantify the potential influence of different raw material compositions on the final carbonization effect; the larger the index, the more sensitive the raw material difference, prompting the need for more substantial parameter adjustment, thereby achieving numerical evaluation of the influence of raw material differences. The present application directly maps the gap between the target raw material and the graphitization degree of the good cluster to the flow rate adjustment amplitude in the first stage, which can complete the "pre-compensation" at the initial stage of heating, preventing low-graphitization-degree raw materials from being oxidized due to excessive volatile matter, and avoiding high-graphitization-degree raw materials from being damaged due to excessive nitrogen flushing, thereby compressing the process deviation to a minimum in the first temperature stage. The present application reflects the atmosphere stability by the dispersion degree of oxygen fluctuation, and reflects the heat field balance by the temperature mean difference, and the "nitrogen filling imbalance degree" composed of the two can diagnose whether the current nitrogen rate is excessive or insufficient; the positive and negative signs directly indicate the adjustment direction, and the absolute value size indicates the adjustment strength, thereby achieving dual inhibition of oxidation risk and energy waste. The present application couples the "flow rate adjustment amplitude" and the "nitrogen filling imbalance degree" according to the temperature stage, forming a closed-loop adaptive algorithm, which can continuously correct the nitrogen flow rate throughout the heating-temperature holding-heating chain; it eliminates the quality fluctuations caused by batch-to-batch differences in raw materials, and avoids the oxidation or energy redundancy problems caused by traditional fixed flow rate, ultimately significantly improving the carbonization qualification rate, product graphitization degree consistency and unit energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, and the advantages thereof, below will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0036] Figure 1 A flow chart of a carbonization method for producing lithium battery negative material provided by an embodiment of the present application. DETAILED DESCRIPTION

[0037] Embodiment 1

[0038] A carbonization method for producing lithium battery negative material provided by an embodiment of the present application, for specific reference Figure 1 , the method comprises the following steps:

[0039] Step 1: Collect and preprocess the relevant data during the carbonization process.

[0040] The initial raw material for the selected lithium battery negative electrode material in this application is artificial graphite. After crushing, ball milling, screening, granulating, coating, and pre-carbonization of the raw material, high-temperature carbonization treatment is performed. During the high-temperature carbonization process, the oxygen and material temperatures in the kiln at each temperature stage during the carbonization process of the graphite preliminary raw material are collected and preprocessed. Specifically:

[0041] The heating rate during the carbonization process of artificial graphite is , and according to the temperature change and the temperature preset threshold, the entire carbonization process is divided into multiple temperature stages, namely the heating-temperature holding-heating-temperature holding-heating-temperature holding-heating and cooling stages. The pre-carbonization and carbonization processes are carried out in a nitrogen atmosphere, and the nitrogen filling rate of each temperature stage is set to .

[0042] Taking the production process of a certain historical graphite negative electrode material as an example, the oxygen data in the kiln during the carbonization process are collected in real time through the control system of the rotary kiln, and the temperature data of the material are collected in real time through an infrared temperature instrument. The data collection interval is 1s, and the collection is performed in each temperature stage during the carbonization process, with a collection duration of the duration of each temperature stage. According to the time sequence of data collection, the oxygen sequence and the material temperature sequence corresponding to each temperature stage are constructed, respectively.

[0043] Next, the graphitization degree of the graphite preliminary raw material before carbonization and the carbonized product after carbonization in this production process are collected by an X-ray diffractometer. According to the above data collection method in the negative electrode material production process, T (100 in this embodiment) production process data are collected.

[0044] Taking the i-th graphite preliminary raw material of the latest production process as an example, it is taken as the target graphite preliminary raw material, the graphitization degree of the i-th graphite preliminary raw material before carbonization is obtained, and the oxygen data and material temperature data of the i-th graphite preliminary raw material in the first temperature stage during the carbonization process are collected, and the oxygen sequence and the material temperature sequence are formed according to the collection time sequence, respectively.

[0045] In order to eliminate the dimensional influence between the data, all the data are normalized. The normalization methods include Z-score, maximum value normalization, and maximum and minimum value normalization, etc. In this embodiment, the maximum and minimum value normalization is adopted.

[0046] Step 2: Evaluate the influence of the graphite preliminary raw material on the carbonization effect.

[0047] In the high-temperature environment of the carbonization process, the graphite negative electrode material will react with oxygen, thereby affecting the carbonization effect; at the same time, the oxidation reaction will also cause the material to have a "run-off" phenomenon, thereby affecting the material yield. Therefore, in the carbonization process, a gas that is not easy to chemically react with the product needs to be filled, thereby preventing the oxidation of the material.

[0048] Because after going through a plurality of preparation processes, the components inside different raw materials are different, the volatilization degree of different raw materials at high temperature will also be inconsistent. If a fixed nitrogen filling rate is used, the nitrogen concentration and the volatilized components will not match. If the nitrogen filling rate is small, oxidation is likely to occur; if the nitrogen filling rate is large, because the temperature of the filled nitrogen is very low relative to the temperature in the furnace, a large amount of nitrogen entering the kiln will cause a large heat loss, thereby affecting the heating effect of the negative electrode material. Therefore, the most appropriate filling rate needs to be set according to different materials to improve the carbonization effect of the negative electrode material.

[0049] First, it is necessary to evaluate whether the carbonization effect difference of different graphitization degrees of graphite preliminary raw materials under the same carbonization parameters is large, and by analyzing the difference between the ith graphite preliminary raw material and the graphite preliminary raw material corresponding to the good carbonization effect, it is necessary to evaluate whether a large adjustment of the carbonization parameters is needed in the first temperature stage.

[0050] Taking the u-th negative electrode material collected in the historical production process as an example, the first product of the u-th negative electrode material is calculated . Among them, is the graphitization degree of the u-th negative electrode material after carbonization, The larger the value is, the better the carbonization effect after carbonization is; is the absolute difference between the material graphitization degree before and after carbonization of the u-th negative electrode material, The larger the value is, the higher the graphitization degree improved by the carbonization process is.

[0051] The first product of T negative electrode materials is calculated in the same way, and then all the first products are input into the clustering algorithm for clustering. The clustering algorithm is not limited to the k-means algorithm and the DPC algorithm. In this embodiment, the k-means algorithm is used, and the elbow rule is used to obtain the optimal number of clustering clusters.

[0052] The mean value of the elements in each clustering cluster is calculated, and the clustering cluster with the largest internal element mean value is recorded as the good cluster. Through the clustering cluster algorithm, the negative electrode material production carbonization process with good carbonization effect can be obtained.

[0053] The mean value and the dispersion degree of the graphitization degree of the graphite preliminary raw material before carbonization of the negative material corresponding to all elements in the good cluster are calculated respectively, and are denoted as the initial mean value and the initial dispersion value of the good cluster respectively. The initial dispersion value can reflect the influence degree of the difference of the initial raw material graphitization degree on the final carbonization effect; the smaller the value is, the more consistent the graphitization degree of the graphite preliminary raw material in the good cluster is, and then the greater the influence of the composition difference of the graphite preliminary raw material on the carbonization effect is. The calculation of the dispersion degree is not limited to variance, mean square deviation, and coefficient of variation.

[0054] The initial mean value of each clustering cluster is calculated in the same way, and then the absolute difference value between the initial mean value of the good cluster and the initial mean value of each clustering cluster is calculated, and the cumulative sum of all absolute difference values is denoted as the first sum value of the good cluster. The first sum value can reflect the overall difference degree of the good cluster and all other clusters in the initial raw material graphitization degree; the greater the value is, the greater the difference in the graphitization degree of the graphite preliminary raw material between the good cluster and the non-good cluster is.

[0055] Constructing the material influence index of the good cluster .

[0056]

[0057] In the formula, C is the initial dispersion value of the good cluster; B is the first sum value of the good cluster; A is the preset adjustment coefficient; and D is the preset adjustment coefficient. is a preset adjustment coefficient, in order to avoid the denominator being 0, the value is taken from the range (0.005, 0.01), the value has little effect on the calculation and can be ignored, and 0.008 is taken in this embodiment.

[0058] The material influence index can reflect the influence degree of the component difference of the graphite preliminary raw material on the carbonization effect, and the greater the value is, the greater the influence degree is; therefore, if the graphite preliminary raw material has a difference, it is more necessary to adjust the control parameter to a greater extent, so as to improve the carbonization effect.

[0059] Step 3: evaluating the adjustment range of the target graphite preliminary raw material in the first temperature stage.

[0060] Further, the carbonization process is a process of removing non-carbon components in the graphite material by high temperature, and then improving the carbon purity of the material. Since the non-carbon components in the negative material will gradually decrease over time in the high temperature environment, the concentration of the non-carbon components volatilized at different temperature stages will also change.

[0061] Since the non-carbon components have not been volatilized in the first temperature stage, the volatilization degree of the non-carbon components in the first temperature stage is greatly affected by the initial composition of the graphite preparation raw material, and thus it is necessary to analyze the difference between the graphitization degree of the i-th graphite preparation raw material and the graphitization degree of the graphite preparation raw material corresponding to the element in the good cluster to evaluate whether the i-th graphite preparation raw material needs to be greatly adjusted in the nitrogen filling rate in the first temperature stage.

[0062] Specifically, the difference between the graphitization degree of the i-th graphite preparation raw material and the graphitization degree of the negative electrode material before carbonization of the graphite preparation raw material corresponding to each element in the good cluster is calculated respectively, and the difference closest to 0 among all the differences is recorded as the first difference of the i-th graphite preparation raw material in the first temperature stage.

[0063] The first difference is negative and the smaller it is, the more non-carbon components are in the i-th graphite preparation raw material, and the more volatile components are precipitated, and thus a larger amount of nitrogen filling is needed to prevent oxidation. The first difference is positive and the larger it is, the higher the graphitization degree of the i-th graphite preparation raw material, and thus the nitrogen filling rate can be reduced to prevent affecting the heating effect of the material. Therefore, the larger or the smaller the first difference is, the greater the adjustment of the nitrogen filling rate in the first temperature stage is needed.

[0064] The flow rate adjustment range of the i-th graphite preparation raw material in the first temperature stage is constructed using the material influence index of the good cluster and the first difference of the i-th graphite preparation raw material in the first temperature stage, wherein the flow rate adjustment range is positively correlated with the first difference and the material influence index, respectively.

[0065] It can be understood that the positive correlation means that the dependent variable increases with the increase of the independent variable, and decreases with the decrease of the independent variable, which is determined by actual application and is not specially limited in the present application.

[0066] Specifically, the flow rate adjustment range of the i-th graphite preparation raw material in the first temperature stage is constructed as .

[0067]

[0068] wherein, is the material influence index of the good cluster; is the first difference of the i-th graphite preparation raw material in the first temperature stage.

[0069] The flow rate adjustment range reflects the magnitude of the nitrogen filling rate adjustment required for the i-th graphite pre-raw material in the first temperature stage of the carbonization process. A negative value indicates that the filling amount needs to be increased, while a positive value indicates that the filling amount needs to be decreased. The larger the absolute value of the flow rate adjustment range, the greater the adjustment range required to adapt to the current raw material characteristics.

[0070] Step 4: Analyze whether the nitrogen filling rate at the current stage is appropriate.

[0071] Furthermore, since the non-carbon components inside the negative electrode material gradually decrease over time, if the temperature is still adjusted by the graphitization degree of the graphite preparatory raw material in the subsequent temperature stages of the carbonization process, errors will occur. At this time, it is necessary to analyze the extent of nitrogen filling rate adjustment in the next temperature stage based on the carbonization degree of the material in the previous temperature stage, thereby improving the carbonization effect of the negative electrode material.

[0072] When materials are carbonized in a kiln, if the nitrogen filling rate is appropriate and the material is not oxidized due to the release of volatile components, the oxygen content in the kiln will be low and stable. However, if the filling rate is too low and the volatile components generated during the heating process cannot be diluted and discharged in time, the volatile components will disrupt the protective atmosphere around the material, leading to significant fluctuations in oxygen concentration.

[0073] Therefore, the dispersion of all elements in the oxygen sequence of the i-th graphite preparatory material at the first temperature stage is calculated and denoted as the first discrete value of the oxygen data. The first discrete value can reflect whether the oxygen fluctuation of the i-th graphite preparatory material at the first temperature stage is drastic. The larger the value, the more drastic the oxygen change, indicating that the possibility of oxidation is greater, and the more nitrogen filling is needed.

[0074] Furthermore, if the amount of nitrogen is too high, oxygen will be more stable. However, excessive nitrogen injection will affect the preparation cost and the heating effect of the negative electrode material, resulting in a slow temperature rise of the material. Therefore, it is necessary to further analyze whether the amount of nitrogen is too high.

[0075] In the first temperature stage, the mean value of all elements within the material temperature sequence of the i-th graphite preparatory raw material is calculated. And the average value of all elements in the material temperature sequence collected during the carbonization process of the corresponding negative electrode material in the good cluster. The average temperature of the i-th graphite raw material. Subtract the average material temperature of the anode material corresponding to each element in the good cluster during the carbonization process. The sum of the differences is denoted as the second sum of the i-th graphite preparatory material in the first temperature stage.

[0076] The second sum value is positive and the larger, the higher the material temperature of the i-th graphite raw material in the first temperature stage, which reflects that the nitrogen filling amount is less. The second sum value is negative and the smaller, the lower the material temperature of the i-th graphite raw material in the first temperature stage, which reflects that the possibility of heat loss and excessive nitrogen injection amount is greater. It should be noted that when the nitrogen filling amount is high, oxidation reaction does not occur, so the first dispersion value is very small at this time.

[0077] Constructing the nitrogen filling imbalance degree of the i-th graphite raw material in the first temperature stage .

[0078]

[0079] In the formula, is the first dispersion value of the oxygen data of the i-th graphite raw material; is the second sum value of the i-th graphite raw material in the first temperature stage.

[0080] The nitrogen filling imbalance degree can reflect whether the nitrogen filling rate of the i-th graphite raw material in the first temperature stage is appropriate; the value is positive and the larger, the less the nitrogen filling amount, and the greater the possibility of oxidation reaction; the value is negative and the smaller, the more the nitrogen filling amount, and the greater the possibility of affecting the material heating effect. Therefore The greater the absolute value of the nitrogen filling imbalance degree, the greater the degree of adjustment of the filling rate is needed, so as to adaptively adjust the atmosphere of the negative electrode material, and ensure that the subsequent carbonization process has good carbonization effect.

[0081] Step 5: Adjusting the nitrogen filling rate under different temperature stages.

[0082] Further, after obtaining the flow rate adjustment range and the nitrogen filling imbalance degree, the nitrogen filling rate of the i-th graphite raw material in each temperature stage of the carbonization process is adjusted, which is specifically as follows:

[0083]

[0084] In the formula, is the adjusted nitrogen filling rate of the i-th graphite raw material in the j-th temperature stage; 、 are respectively the preset initial nitrogen filling rate of the i-th graphite raw material in the j-th and j-1-th temperature stages, which is 80 in this embodiment; is a preset adjustment parameter, in order to avoid that the adjustment degree is too large and thus affects the carbonization effect, which is 10 in this embodiment; 、 respectively, the flow rate adjustment range of the i th graphite raw material in the j th and the j-1 th temperature stage, nitrogen filling imbalance degree; is a normalization function, and in this embodiment, a tanh normalization function is used.

[0085] When is less than 0, it indicates that the graphitization degree of the i th graphite raw material is low, at this time, the non-carbon component is high, and the filling rate needs to be increased; when is greater than 0, it indicates that the non-carbon component is low, and the filling rate is reduced to avoid affecting the material heating effect.

[0086] When is less than 0, it indicates that the nitrogen filling in the last temperature stage is too much, which affects the heating effect of the material, so the filling amount should be appropriately reduced in the next temperature stage to improve the material temperature; when is greater than 0, it indicates that the nitrogen filling in the last temperature stage is too little, and oxidation occurs, so the filling amount needs to be increased in the next stage to avoid the occurrence of oxidation again.

[0087] By analyzing the data characteristics of the i th graphite raw material before carbonization and in each temperature stage in the carbonization process, the nitrogen filling rate in the subsequent temperature stages is adjusted and optimized, thereby realizing self-adaptive adjustment of the nitrogen filling rate, accurately adapting to the differences in different raw material characteristics, avoiding unnecessary nitrogen consumption and heat loss while avoiding material oxidation, and improving the carbonization effect.

[0088] Thus, the invention of a carbonization method and carbonization process for producing lithium battery negative materials is completed.

[0089] Embodiment 2

[0090] Based on the same inventive concept as the above-mentioned carbonization method for producing lithium battery negative materials, another embodiment of the present application proposes a carbonization process for producing lithium battery negative materials, which comprises:

[0091] The raw material is crushed, ball milled, sieved, granulated, coated, and pre-carbonized. The particle size of the crushed graphite is 1.62um; the graphite negative material is coated with coating pitch, the particle size of the coating pitch is 5um, and the addition amount of the coating pitch is 5%; the pre-carbonization temperature is 300 degrees, the holding time is 2 hours, and the heating rate is Thus, the graphite raw material before the carbonization process can be obtained.

[0092] After that, the graphite raw material is high-temperature carbonized: first, heated to 900 degrees and kept for 2h, then heated to 1000 degrees and kept for 4h, then heated to 1100 degrees and kept for 8h, and finally heated to 1200 degrees, then naturally cooled to room temperature, carbonized, and carbonized.

[0093] wherein, in the high temperature carbonization process, the nitrogen gas filling rate at different temperature stages is adjusted using the carbonization method described above.

[0094] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the application cover any and all variations of the application that come within the scope of the general concept of the application. It is intended that the application not be limited to the specific examples disclosed, but will include all implementations that are within its spirit and scope.

[0095] It is to be understood that the application is not limited to the precise details of construction and the arrangement of components described above and illustrated in the drawings. Various modifications and changes can be made without departing from the scope of the application.

Claims

1. A carbonization method for producing a lithium battery negative electrode material, characterized by, The method includes the following steps: Artificial graphite is subjected to raw material crushing, ball milling and screening, granulation, coating and pre-carbonization to obtain graphite pre-raw material, which is then subjected to high-temperature carbonization treatment; during the high-temperature carbonization process, the oxygen and material temperature in the kiln at each temperature stage of the carbonization process of the target graphite pre-raw material are collected and pretreated. Clustering was performed based on the differences in graphitization degree of multiple anode materials before and after carbonization in historical production processes; the cluster with the largest internal element mean was denoted as a good cluster. The dispersion and average degree of graphitization of the negative electrode material corresponding to all elements in the good cluster before carbonization and the difference between it and other clusters are analyzed to determine the material influence index of the good cluster. Furthermore, by combining the graphitization degree difference between the target graphite pre-raw material and the graphite pre-raw material corresponding to the elements in the good cluster, the flow rate adjustment range of the target graphite pre-raw material in the first temperature stage is constructed. By utilizing the oxygen dispersion of the target graphite pre-raw material in the first temperature stage, and the temperature mean difference between the target graphite pre-raw material and the corresponding anode material of good cluster elements before carbonization, the nitrogen filling imbalance of the target graphite pre-raw material in the first temperature stage is constructed. By combining the flow rate adjustment range and the nitrogen filling imbalance, the nitrogen filling rate of the target graphite preparatory raw material is adjusted at different temperature stages.

2. The carbonization method for producing a lithium battery negative material according to claim 1, characterized by, In the coating operation, the graphite anode material is coated with coating asphalt with a particle size of 5 μm and an addition amount of 5%.

3. The carbonization method for producing a lithium battery anode material according to claim 1, characterized by, The temperature in the pre-carbonization operation is 300 degrees, the holding time is 2 hours, and the heating rate is .

4. The carbonization method for producing a lithium battery anode material according to claim 1, characterized by, In the high-temperature carbonization process, the temperature is first raised to 900 degrees and held for 2 hours, then raised to 1000 degrees and held for 4 hours, then raised to 1100 degrees and held for 8 hours, and finally raised to 1200 degrees and then naturally cooled to room temperature to complete the carbonization and obtain carbides. That is, the temperature stages in the high-temperature carbonization process include the stages of heating-holding-heating-holding-heating-holding-heating and cooling.

5. The carbonization method for producing a lithium battery anode material according to claim 1, characterized by, The method of clustering multiple negative electrode materials based on differences in graphitization before and after carbonization in historical production processes includes: For the u-th negative electrode material in the historical production process, a first product of the u-th negative electrode material is calculated ; wherein, is a graphitization degree of the u-th negative electrode material after carbonization; is an absolute difference between the graphitization degree of the material before carbonization and the graphitization degree of the material after carbonization of the u-th negative electrode material; and the first products calculated for all negative electrode materials in the historical production process are clustered.

6. The carbonization method for producing a lithium battery anode material according to claim 5, characterized by, The method for determining the material influence index of the good cluster is as follows: Calculate the mean and dispersion of the graphitization degree of the negative electrode material corresponding to all elements in the good cluster before carbonization, and record them as the initial mean and initial dispersion values ​​of the good cluster respectively. Calculate the initial mean of each cluster in the same way, calculate the absolute difference between the initial mean of the good cluster and the initial mean of each cluster, and record the sum of all absolute differences as the first sum of the good cluster. Material influence index for building good clusters : ; where C is the initial dispersion value of good clusters; B is the first sum value of good clusters; is a preset tuning coefficient to avoid denominator 0.

7. The carbonization method for producing a lithium battery anode material according to claim 6, characterized by, The method for constructing the flow rate adjustment range of the target graphite preparatory material in the first temperature stage is as follows: Calculate the graphitization degree of the target graphite preparatory material and subtract the difference between the graphitization degree of the negative electrode material corresponding to each element in the good cluster before carbonization. Then, record the difference closest to 0 among all the differences as the first difference of the target graphite preparatory material in the first temperature stage. The flow rate adjustment range is positively correlated with the first difference and the material influence index.

8. The carbonization method for producing a lithium battery anode material according to claim 1, characterized by, The method for constructing the nitrogen filling imbalance degree of the target graphite preliminary raw material in the first temperature stage is: Calculate the dispersion degree of all oxygen data collected by the i th graphite preliminary raw material in the first temperature stage, and mark it as the first dispersion value of the oxygen data; In the first temperature stage, calculate the mean value of all material temperatures collected by the target graphite preliminary raw material, and the mean value of all material temperatures collected by the corresponding negative electrode material in the carbonization process of each element in the good cluster, respectively; Subtract the sum of the differences between the mean value of the material temperature of the target graphite preliminary raw material and the mean value of the material temperature of the corresponding negative electrode material in the carbonization process of each element in the good cluster, and mark it as the second sum value of the target graphite preliminary raw material in the first temperature stage; Sum the first dispersion value and the second sum value to obtain the nitrogen filling imbalance of the target graphite preliminary raw material in the first temperature stage.

9. The carbonization method for producing a lithium battery anode material according to claim 8, characterized by, The method for adjusting the nitrogen filling rate of the target graphite preliminary raw material in different temperature stages is: In the formula, is the nitrogen filling rate of the i th graphite raw material at the j th temperature stage after adjustment; , are the preset initial nitrogen filling rates of the i th graphite raw material at the j th and j-1 th temperature stages, respectively; is the preset adjustment parameter; , are the flow rate adjustment range and the nitrogen filling imbalance degree of the i th graphite raw material at the j th and j-1 th temperature stages, respectively; is a normalization function.

10. A carbonization process for producing a lithium battery negative material, comprising raw material crushing, ball milling and screening, granulation, coating and pre-carbonization operations on artificial graphite, and then high-temperature carbonization treatment; characterized in that, In the process of high-temperature carbonization treatment, the nitrogen filling rate in different temperature stages is adjusted by the carbonization method described in any one of claims 1-9.

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