Method for evaluating coating rate of coated graphite based on frequency distribution histogram
By calculating the coating rate using Raman surface scanning and frequency distribution histograms, the problem of evaluating the coating rate of coated graphite was solved, the kinetic properties and fast charging capability of coated graphite were improved, and an accurate method for evaluating the coating rate was provided.
Patent Information
- Application Number
- CN202511700961.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-19
- Publication Date
- 2026-02-13
AI Technical Summary
Existing technologies lack effective methods to evaluate the coating efficiency of coated graphite, which affects the kinetic properties and fast-charging capability of coated graphite.
Raman surface scanning was performed on the graphite substrate and the coated graphite to establish a frequency distribution histogram. The coating rate K=A/B was calculated, where A is the sum of the number of sites where the frequency of each interval increased compared to the frequency distribution histogram I, and B is the total number of sites. This method eliminates the interference of substrate defects and improves the accuracy of coating rate evaluation.
It provides a concise and easy-to-implement method for evaluating coating rate, with accurate and reliable results, guiding the research and development and product debugging of coated graphite, and improving the kinetic performance and fast charging capability of coated graphite.
Smart Images
Figure CN121521836A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of graphite anode materials for lithium-ion batteries, and specifically to a method for evaluating the coating rate of coated graphite based on a frequency distribution histogram. Background Technology
[0002] Lithium-ion batteries are currently an important energy storage device for human society. Due to their low cost, high energy density, and good cycle stability, artificial graphite has become the most widely used anode material in lithium-ion batteries.
[0003] Graphite is a layered structure in which carbon atoms within a layer are separated by sp. 2 Hybridization occurs through covalent bonds, and layers are connected by van der Waals forces via molecular bonds. Lithium-ion insertion and extraction sites are located at the end faces between layers. Due to the relatively complete crystal structure of ideal graphite, the number of lithium-ion insertion and extraction sites is relatively limited, resulting in relatively poor kinetic performance. To improve the kinetic performance of graphite and thus its fast-charging capability, coating is a common method. Common coating agents are primarily pitch; through coating and carbonization, a layer of soft carbon can be formed on the graphite surface, thereby increasing the number of lithium insertion sites and improving the kinetics and fast-charging performance of graphite. The two most important factors affecting the coating effect are the residual carbon content and the coating uniformity. With the same residual carbon content, the more uniform the coating, the higher the coating rate of the coated graphite, the more lithium-ion insertion sites are provided, and the better the corresponding kinetics and fast-charging performance of the coated graphite. However, currently, there is a lack of effective methods for evaluating the coating rate of coated graphite.
[0004] Therefore, how to establish a method for evaluating the surface coating rate of coated graphite is an urgent problem to be solved. Summary of the Invention
[0005] This application provides a method for evaluating the coating rate of coated graphite based on a frequency distribution histogram. By establishing a frequency distribution histogram from the Raman scanning results of the graphite substrate before and after coating, the coating rate of the coating layer on the surface of the coated graphite is calculated according to the corresponding calculation formula. The trend of the coating rate is consistent with the trend of the capacity retention rate, which has important guiding significance and value for guiding the research and development and product debugging of coated graphite.
[0006] This application provides a method for evaluating the coating rate of coated graphite based on a frequency distribution histogram, comprising the following steps: S1. Raman surface scanning detection was performed on the graphite substrate and the coated graphite using a laser Raman spectrometer to obtain I values at multiple sites within the scanning range. D / I G value; Coated graphite is a product obtained by coating and modifying a graphite substrate; S2, I of the graphite substrateD / I G A frequency distribution histogram I was constructed with group intervals of 0.02-0.2. I coated with graphite D / I G A frequency distribution histogram II was constructed with group intervals of 0.02-0.2; The class intervals of frequency distribution histogram I and frequency distribution histogram II are the same; S3. Calculate the coating ratio K of the coated graphite: K=A / B In the formula, A is the sum of the sites whose frequency increases in each interval of the frequency distribution histogram II compared to the frequency distribution histogram I, and B is the total number of sites detected by Raman surface scanning on graphite substrate or coated graphite.
[0007] In one possible implementation, in S1, more than 100 I's are obtained. D / I G Value, optionally, obtain more than 400 I values. D / I G The value is preferably more than 1000.
[0008] In one possible implementation, in S2, the class interval of the frequency distribution histogram I is 0.02-0.04, which can be selected as 0.02 or 0.04.
[0009] In one possible implementation, in S1, the scanning range of the Raman surface scan detection is -200μm≤X≤200μm; -200μm≤Y≤200μm, and the scanning point interval in the X and Y directions is independently 1~10μm.
[0010] In one possible implementation, -55μm≤X≤55μm can be selected as -50μm≤X≤50μm.
[0011] In one possible implementation, -55μm≤Y≤55μm can be selected as -50μm≤Y≤50μm.
[0012] In one possible implementation, the scanning point intervals in the X and Y directions are independently 4~6μm.
[0013] In one possible implementation, the graphite substrate is a single graphite particle, a secondary graphite particle, or a mixture of both.
[0014] In one possible implementation, the graphite substrate has a particle size Dv50 of 5~25μm.
[0015] In one possible implementation, the coating layer is amorphous carbon; In one possible implementation, the thickness of the coating layer is 10~200 nm.
[0016] The technical solution of this application has the following advantages: 1. The coating rate evaluation method for coated graphite based on frequency distribution histogram provided in this application includes the following steps: S1. Raman surface scanning detection is performed on the graphite substrate and the coated graphite using a laser Raman spectrometer to obtain I values at multiple sites within the scanning range. D / I G Value; Coated graphite is the product obtained by coating and modifying a graphite substrate; S2, I of the graphite substrate D / I G A frequency distribution histogram I was constructed with group intervals of 0.02-0.2; the graphite-coated I... D / I G A frequency distribution histogram II is established with a group interval of 0.02-0.2; the group intervals of frequency distribution histogram I and frequency distribution histogram II are the same; S3, calculate the coating rate K of the coated graphite: K=A / B, where A is the sum of the sites whose frequency increases in each interval of frequency distribution histogram II compared to frequency distribution histogram I, and B is the total number of sites detected by Raman surface scanning of graphite substrate or coated graphite.
[0017] This application establishes a frequency distribution histogram based on Raman scanning results before and after coating of graphite substrate, and calculates the coating rate of the coating layer on the surface of the coated graphite according to the corresponding calculation formula. The trend of the coating rate is consistent with the trend of the capacity retention rate, which has important guiding significance and value for guiding the research and development and product debugging of coated graphite.
[0018] Furthermore, this application can eliminate the interference of defects in the graphite substrate itself and extreme test errors, thereby obtaining a more accurate coating rate. The calculation formula of this method is concise, easy to program and execute, and the data results are intuitive, reliable, and highly accurate, making it an effective method for evaluating the surface coating rate of coated graphite. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0020] Figure 1 The images show the Raman imaging spectra of the graphite substrate (a) and the graphite-coated substrate (b) in Example 1.
[0021] Figure 2The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 1.
[0022] Figure 3 The images show the Raman imaging spectra of the graphite substrate (a) and the graphite-coated substrate (b) in Example 2.
[0023] Figure 4 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 2.
[0024] Figure 5 The images show the Raman imaging spectra of the graphite substrate (a) and the graphite-coated substrate (b) in Example 3.
[0025] Figure 6 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 3.
[0026] Figure 7 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 4.
[0027] Figure 8 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 5.
[0028] Figure 9 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 6.
[0029] Figure 10 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 7.
[0030] Figure 11 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 8.
[0031] Figure 12 The data distribution is shown in frequency distribution histogram I and frequency distribution histogram II in Example 9.
[0032] Figure 13 This is a schematic diagram of the evaluation method used in this application. Detailed Implementation
[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0034] 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 of this application are intended to cover non-exclusive inclusion. 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. The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
[0035] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.
[0036] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two).
[0037] The coverage of the graphite coating layer has a significant impact on the performance of the product. Therefore, establishing an effective evaluation method for the coating coverage rate is an urgent problem to be solved.
[0038] To address the problems existing in the aforementioned related technologies, this application provides a method for evaluating the surface coating rate of coated graphite, such as... Figure 13 As shown, it includes: S1. Raman surface scanning detection was performed on the graphite substrate and the coated graphite using a laser Raman spectrometer to obtain I values at multiple sites within the scanning range. D / I G value; Coated graphite is a product obtained by coating and modifying a graphite substrate; S2, I of the graphite substrate D / I G A frequency distribution histogram I was constructed with group intervals of 0.02-0.2. I coated with graphite D / I G A frequency distribution histogram II was constructed with group intervals of 0.02-0.2; The class intervals of frequency distribution histogram I and frequency distribution histogram II are the same; S3. Calculate the coating ratio K of the coated graphite: K=A / B In the formula, A is the sum of the number of sites whose frequency increases in each interval of frequency distribution histogram II compared to frequency distribution histogram I (i.e., the sum of the number of sites in the effective coverage interval), and B is the total number of sites detected by Raman surface scanning on graphite substrate or coated graphite.
[0039] I D This indicates that the shift was at 1300 cm⁻¹ during Raman spectroscopy testing. -1 Up to 1400cm -1 The intensity of the peak within the range, I G This indicates that the shift was at 1520 cm⁻¹ during Raman spectroscopy testing. -1 Up to 1620cm -1 The intensity of peaks within the specified range. This application processes the data obtained after Raman surface scanning of coated graphite into a frequency distribution histogram and compares it with the graphite substrate. This eliminates the interference of defects in the graphite substrate itself and extreme test errors, thus obtaining a more accurate coating rate. The calculation formula of this method is concise, easy to program and execute, and the data results are intuitive, reliable, and highly accurate. It is a method for evaluating the surface coating rate of coated graphite.
[0040] In one possible implementation, the method for coating modification of a graphite substrate includes: mixing the graphite substrate with a coating agent and then performing a carbonization treatment.
[0041] Optionally, the coating agent may be one or a mixture of two or more of the following: asphalt, resin, biomass, or sugars.
[0042] In one possible implementation, in S1, more than 100 I's are obtained. D / I G Value, optionally, obtain more than 400 I values. D / I G Values. For example, they could be 400, 600, 1000, or 3000.
[0043] In one possible implementation, in S2, the group intervals of frequency distribution histogram I and frequency distribution histogram II are 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 or 0.2.
[0044] In one possible implementation, in S1, the scanning range of the Raman surface scan detection is -200μm≤X≤200μm; -200μm≤Y≤200μm.
[0045] In one possible implementation, -55μm≤X≤55μm can be selected as -50μm≤X≤50μm.
[0046] In one possible implementation, -55μm≤Y≤55μm can be selected as -50μm≤Y≤50μm.
[0047] In one possible implementation, the scanning point interval (step size) in the X and Y directions is 1~10μm independently, and can be selected as 4~6μm.
[0048] In one possible implementation, the graphite substrate is a single graphite particle, a secondary graphite particle, or a mixture of both. A single particle refers to a non-agglomerated, primary particle.
[0049] In one possible implementation, the graphite substrate has a particle size Dv50 of 5~25μm.
[0050] In one possible implementation, the coating layer is amorphous carbon; In one possible implementation, the thickness of the coating layer is 10~200 nm.
[0051] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.
[0052] Example 1 A graphite substrate (secondary particle artificial graphite with a Dv50 of 14.2 μm) was mixed with petroleum asphalt powder (Dv50 of 5 μm) with a softening point of 205℃, and then carbonized in a box furnace. The mass ratio of graphite substrate to petroleum asphalt was 100:3, the carbonization temperature was 1200℃, and the carbonization time was 5h. An amorphous carbon layer was formed on the outer surface of the graphite substrate, resulting in amorphous carbon-coated graphite.
[0053] 1g each of graphite substrate and coated graphite were prepared and analyzed using a Renishaw Raman spectrometer with a scanning step of 5μm and a scanning area of -50μm≤X≤50μm and -50μm≤Y≤50μm. A total of 1323 points were scanned across the area, and Raman imaging spectra were obtained within a 100×100μm*μm range (see [reference]). Figure 1 ) and scan data (I at each point) D / I G value).
[0054] I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.02; the histogram I was then scanned from the surface of the graphite coating. D / I G A frequency distribution histogram II was constructed with a group interval of 0.02. Frequency distribution histogram I and frequency distribution histogram II are shown below. Figure 2 .
[0055] Example 2 This embodiment is basically the same as Embodiment 1, except that: The mass ratio of graphite substrate to petroleum asphalt powder was 100:4.5. Raman imaging spectra were obtained after Raman surface scanning, see [link to image]. Figure 3 Frequency distribution histogram I and frequency distribution histogram II are shown in [reference]. Figure 4 .
[0056] Example 3 This embodiment is basically the same as Embodiment 1, except that: The mass ratio of graphite substrate to petroleum asphalt powder was 100:6. Raman imaging spectra were obtained after Raman surface scanning, see [link to image]. Figure 5 Frequency distribution histogram I and frequency distribution histogram II are shown in [reference]. Figure 6 .
[0057] Example 4 This embodiment is basically the same as Embodiment 1, except that: I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.04; the histogram I was then scanned from the surface of the graphite coating. D / I GA frequency distribution histogram II was constructed with a group interval of 0.04. The distributions of frequency distribution histograms I and II are shown in [reference needed]. Figure 7 .
[0058] Example 5 This embodiment is basically the same as embodiment 2, except that: I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.04; the histogram I was then scanned from the surface of the graphite coating. D / I G A frequency distribution histogram II was constructed with a group interval of 0.04. The distributions of frequency distribution histograms I and II are shown in [reference needed]. Figure 8 .
[0059] Example 6 This embodiment is basically the same as embodiment 3, except that: I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.04; the histogram I was then scanned from the surface of the graphite coating. D / I G A frequency distribution histogram II was constructed with a group interval of 0.04. The distributions of frequency distribution histograms I and II are shown in [reference needed]. Figure 9 .
[0060] Example 7 This embodiment is basically the same as Embodiment 1, except that: I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.1; the histogram I was then scanned from the surface of the graphite coating. D / I G A frequency distribution histogram II was constructed with a group interval of 0.1. The distributions of frequency distribution histograms I and II are shown in [reference needed]. Figure 10 .
[0061] Example 8 This embodiment is basically the same as embodiment 2, except that: I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.1; the histogram I was then scanned from the surface of the graphite coating. D / I G A frequency distribution histogram II was constructed with a group interval of 0.1. The distributions of frequency distribution histograms I and II are shown in [reference needed]. Figure 11 .
[0062] Example 9 This embodiment is basically the same as embodiment 3, except that: I after scanning the graphite substrate surface D / I G A frequency distribution histogram I was constructed with a group interval of 0.1; the histogram I was then scanned from the surface of the graphite coating. D / I G A frequency distribution histogram II was constructed with a group interval of 0.1. The distributions of frequency distribution histograms I and II are shown in [reference needed]. Figure 12 .
[0063] Performance testing The following tests were performed on the uncoated graphite substrate and the coated graphite used in each embodiment: 1. Testing of particle sizes Dv50 and Dn10 According to national standard GB / T 24533 Appendix A of 2019 requires that the particle size be tested using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.
[0064] Dv50 refers to the particle size at which the cumulative volume distribution percentage reaches 50%, meaning that the volume content of particles smaller than or equal to this size accounts for 50% of the total particle volume; Dn10 refers to the number of particles smaller than or equal to this value in the measured particle sample, which accounts for 10% of the total number of particles.
[0065] 2. Capacity retention test According to GB / T24533 The following steps are required for fabricating button cells according to Appendix G of 2019: 5 hours of rest; constant current discharge at 0.1 C to 0.01 V; constant voltage discharge at 0.01 V with a cutoff current of 0.01 C; 10 minutes of rest; constant current charging at 0.1 C to 1.5 V; 10 minutes of rest; constant current discharge at 0.1 C to 0.01 V; constant voltage discharge at 0.01 V with a cutoff current of 0.01 C; constant current charging at 0.2 C to 1.5 V; 10 minutes of rest; constant current discharge at 0.2 C to 0.01 V; constant voltage discharge at 0.01 V with a cutoff current of 0.01 C; 10 minutes of rest; constant current charging at 0.2 C to 1.5 V; constant current discharge at 3.0 ... Charge to 1.5V using C-type charging; let stand for 10 minutes.
[0066] Capacity retention rate at 3.0C / 0.2C = Q3.0C / Q0.2C × 100% In the formula, Q0.2 C is the specific capacity of constant current 0.2 C discharge, and the unit is milliampere-hours per gram (mAh / g). Q3.0 C is the specific capacity of constant current 3.0 C discharge, expressed in milliampere-hours per gram (mAh / g).
[0067] The test results are shown in Table 1.
[0068] Relative increase = (Capacity retention rate of coated graphite - Capacity retention rate of graphite substrate) / Capacity retention rate of graphite substrate * 100% Table 1
[0069] As can be seen from the test data in Table 1, the Dv50 of coated graphite increased compared to the graphite substrate. With the addition of asphalt increasing from 3 wt% to 6 wt%, Dv50 increased from 14.6 μm to 15.8 μm, and Dn10 increased from 1.85 μm to 1.88 μm. Specifically, the coating rates in Examples 1, 2, and 3 were 57.3%, 60.9%, and 68.0%, respectively, indicating that the coating rate increased accordingly with the increase in the amount of coating agent added. The trend of the coating rate change is consistent with the trend of the capacity retention rate change. Examples 4-6 and 7-9 are based on Examples 1-3, with adjustments to the method parameters for calculating the coating rate. The corresponding coating rate calculation results are consistent with the trend of the capacity retention rate change, indicating that the surface coating rate evaluation method for coated graphite provided by this method is relatively accurate, highly feasible, and strongly correlated with electrical properties. It has important guiding significance and value for guiding the research and development and product debugging of coated graphite.
[0070] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.
Claims
1. A method for evaluating the coating rate of coated graphite based on frequency distribution histograms, characterized in that, Includes the following steps: S1. Raman surface scanning detection was performed on the graphite substrate and the coated graphite using a laser Raman spectrometer to obtain I values at multiple sites within the scanning range. D / I G value; Coated graphite is a product obtained by coating and modifying a graphite substrate; S2, I of the graphite substrate D / I G A frequency distribution histogram I was constructed with group intervals of 0.02-0.
2. I coated with graphite D / I G A frequency distribution histogram II was constructed with group intervals of 0.02-0.2; The class intervals of frequency distribution histogram I and frequency distribution histogram II are the same; S3. Calculate the coating ratio K of the coated graphite: K=A / B In the formula, A is the sum of the sites whose frequency increases in each interval of the frequency distribution histogram II compared to the frequency distribution histogram I, and B is the total number of sites detected by Raman surface scanning on graphite substrate or coated graphite.
2. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to claim 1, characterized in that, In S1, obtain more than 100 I D / I G Value, optionally, obtaining more than 400 I values. D / I G The value is preferably more than 1000.
3. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to claim 1, characterized in that, In S2, the class interval of the frequency distribution histogram I is 0.02-0.1, which can be selected as 0.02-0.
04.
4. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to claim 1, characterized in that, In S1, the scanning range of Raman surface scanning detection is -200μm≤X≤200μm; -200μm≤Y≤200μm, and the scanning point intervals in the X and Y directions are 1~10μm respectively.
5. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to claim 4, characterized in that, -55μm≤X≤55μm, can be selected as -50μm≤X≤50μm.
6. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to claim 4, characterized in that, -55μm≤Y≤55μm, can be selected as -50μm≤Y≤50μm.
7. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to any one of claims 1-6, characterized in that, The scanning sampling intervals in the X and Y directions are 4~6μm, respectively.
8. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to any one of claims 1-6, characterized in that, The graphite substrate is a single graphite particle, a secondary graphite particle, or a mixture of both.
9. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to any one of claims 1-6, characterized in that, The particle size Dv50 of the graphite substrate is 5~25μm.
10. The method for evaluating the coating rate of coated graphite based on frequency distribution histograms according to any one of claims 1-6, characterized in that, The coating layer of the graphite is amorphous carbon; And / or the thickness of the coating layer of the graphite is 10~200nm.