Evaluation method for uniformity of surface coating layer of coated graphite
By performing Raman surface scanning on graphite substrate and coated graphite using a laser Raman spectrometer, eliminating some extreme points, and calculating the coating rate K, the problem of difficulty in evaluating the uniformity of the graphite surface coating layer is solved, achieving a highly accurate and representative evaluation and improving the performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WANHUA CHEM GRP BATTERY TECH CO LTD
- Filing Date
- 2024-10-29
- Publication Date
- 2026-05-08
AI Technical Summary
Existing technologies are insufficient to effectively evaluate the uniformity of graphite surface coatings, which affects the performance of lithium-ion batteries.
The graphite substrate and coated graphite were scanned using a laser Raman spectrometer. Some extreme points were removed, and the coating rate K was calculated as (the ratio of the number of points with ID/IG values > M in optimized data II to the total number of points) to evaluate the coating condition of the coated graphite surface.
This improves the accuracy and representativeness of evaluating the uniformity of the coating layer on the graphite surface, enabling rapid and accurate assessment of the uniformity of the graphite surface coating layer and enhancing the performance of lithium-ion batteries.
Smart Images
Figure CN121994769A_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 uniformity of the coating layer on the surface of coated graphite. Background Technology
[0002] Lithium-ion batteries possess advantages such as high energy density, high operating voltage, long cycle life, and environmental friendliness, and are widely used in 3C consumer products, power batteries, and energy storage batteries. Commonly used negative electrode materials in lithium-ion batteries include graphite and silicon-based materials. Among these, artificial graphite has become the most commonly used negative electrode material in commercially available lithium-ion batteries due to its high energy density, low voltage, good conductivity, abundant resources, and low price.
[0003] However, due to the slow lithium intercalation kinetics and low operating potential of graphite, the stability and safety of artificial graphite materials under high-rate charge and discharge cannot meet the application requirements of fast-charging batteries. By coating graphite-based anodes with a layer of amorphous carbon on the surface of artificial graphite through solid-phase, liquid-phase, or gas-phase carbonization deposition methods, a core-shell structure is constructed. This allows the modified anode material's "core" to retain the advantages of high capacity and low potential of graphite materials, while its "shell" has good electrolyte compatibility. This effectively improves the initial charge efficiency, cycle stability, and rate performance of graphite anodes. The completeness and uniformity of the coating layer on the graphite surface have a significant impact on the performance of the product.
[0004] Therefore, how to establish an effective evaluation method for the coverage state has become an urgent problem to be solved. Summary of the Invention
[0005] This application provides a method for evaluating the uniformity of the coating layer on the surface of coated graphite. The uniformity of the coating is evaluated by Raman scanning results before and after coating the graphite substrate, and the evaluation results are more accurate.
[0006] This application provides a method for evaluating the uniformity of the coating layer on the surface of coated graphite, including:
[0007] 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 points within the scanning range. D / I G value;
[0008] Coated graphite is a product obtained by coating and modifying a graphite substrate;
[0009] S2, I for graphite substrate D / I G The values are sorted in descending order, and the top 10% to 20% of the data points are removed to obtain optimized data I; the largest value I in optimized data I is selected. D / I GThe value is used as the critical point M;
[0010] S3, I for coated graphite D / I G The values are sorted in descending order, and the first 10% to 20% of the points and the last 10% to 20% of the points are removed to obtain optimized data II;
[0011] S4. Calculate the coating ratio K of the coated graphite:
[0012] K = A / B
[0013] In the formula, A represents the optimized data in II. D / I G The number of points with values greater than M, where B is the total number of points in optimized data II.
[0014] In one alternative implementation, in S1, more than 300 I's are obtained. D / I G Value, optionally, obtaining more than 400 I values. D / I G value.
[0015] In one alternative implementation, in S3, the top 15% of points are removed.
[0016] In an alternative implementation, in S4, the first 15% of the points and / or the last 15% of the points are removed.
[0017] In an optional embodiment, 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.
[0018] In one alternative implementation, -55μm≤X≤55μm can be optionally -50μm≤X≤50μm.
[0019] In one alternative implementation, -55μm≤Y≤55μm can be optionally -50μm≤Y≤50μm.
[0020] In one alternative implementation, the scanning point intervals in the X and Y directions are independently 4–6 μm.
[0021] In one alternative embodiment, the graphite substrate is a single graphite particle, a secondary graphite particle, or a mixture of both.
[0022] Optionally, the particle size Dv50 of the graphite substrate is 5 to 25 μm.
[0023] In one alternative embodiment, the coating layer is amorphous carbon;
[0024] And / or the thickness of the coating layer is 10–50 nm.
[0025] The technical solution of this application has the following advantages:
[0026] 1. The method for evaluating the uniformity of the coating layer on the surface of coated graphite provided in this application includes: S1. Performing Raman surface scanning detection on the graphite substrate and the coated graphite using a laser Raman spectrometer to obtain the I values at multiple points 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 The values are sorted in descending order, and the top 10% to 20% of the data points are removed to obtain optimized data I; the largest value I in optimized data I is selected. D / I G The value is used as the critical point M; S3, for the I of coated graphite D / I G The values are sorted in descending order, and the top 10%–20% and bottom 10%–20% of the data points are removed to obtain optimized data II; S4, calculate the coating rate K of the coated graphite: K = A / B, where A is the coating rate of the graphite in optimized data II. D / I G The number of points with values greater than M, where B is the total number of points in optimized data II.
[0027] This application considers the defect rate of the graphite substrate material before coating and eliminates some extreme points. It achieves this by analyzing the I-values of the graphite substrate and the coated graphite. D / I G The coating condition of graphite surfaces can be determined with simple data processing, and the accuracy of coating rate calculation is high, showing a significant advantage in assessing the uniformity of graphite surface coating. Furthermore, the coating is obtained through Raman imaging spectra. D and I G The ratio is used to distinguish between graphite substrate and coating layer. The selected sample covers a wide area, is representative, and provides intuitive and accurate characterization results. Attached Figure Description
[0028] 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.
[0029] Figure 1 The images show the Raman imaging spectra of the graphite substrate (a) and the graphite-coated substrate (b) in Example 1.
[0030] Figure 2 This is the data distribution for optimized data I and optimized data II in Example 1.
[0031] Figure 3 The images show the Raman imaging spectra of the graphite substrate (a) and the graphite-coated substrate (b) in Example 2.
[0032] Figure 4 This is the data distribution for optimized data I and optimized data II in Example 2.
[0033] Figure 5 The images show the Raman imaging spectra of the graphite substrate (a) and the graphite-coated substrate (b) in Example 3.
[0034] Figure 6 This is the data distribution for optimized data I and optimized data II in Example 3.
[0035] Figure 7 This is the data distribution for optimized data I and optimized data II in Example 4.
[0036] Figure 8 This is the data distribution for optimized data I and optimized data II in Example 5.
[0037] Figure 9 This is the data distribution for optimized data I and optimized data II in Example 6.
[0038] Figure 10 This is the data distribution for optimized data I and optimized data II in Example 7.
[0039] Figure 11 This is the data distribution for optimized data I and optimized data II in Example 8.
[0040] Figure 12 This is the data distribution for optimized data I and optimized data II in Example 9. Detailed Implementation
[0041] 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.
[0042] 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 and claims of this application are intended to cover non-exclusive inclusion.
[0043] In the description of the embodiments of this application, technical terms such as "I" and "II" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "several" means one or more.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" 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 are not intended to 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.
[0048] Whether the coating layer on the graphite surface is complete and uniform has a significant impact on the performance of the product. Therefore, how to establish an effective evaluation method for coating status has become an urgent problem to be solved.
[0049] To address the problems existing in the aforementioned related technologies, this application provides a method for evaluating the uniformity of the coating layer on the surface of coated graphite, comprising:
[0050] 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 points within the scanning range. D / I G value;
[0051] Coated graphite is a product obtained by coating and modifying a graphite substrate;
[0052] S2, I for graphite substrate D / I G The values are sorted in descending order, and the top 10% to 20% of the data points are removed to obtain optimized data I; the largest value I in optimized data I is selected. D / I G The value is used as the critical point M;
[0053] S3, I for coated graphite D / I G The values are sorted in descending order, and the top 10% to 20% and the bottom 10% to 20% of the data points are removed to obtain optimized data II.
[0054] S4. Calculate the coating ratio K of the coated graphite:
[0055] K = A / B
[0056] In the formula, A represents the optimized data in II. D / I G The number of points with values greater than M, where B is the total number of points in optimized data II.
[0057] Coated Graphite I D / I G Points with values greater than the critical point are covered points, and the rest are uncovered points.
[0058] 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 considers the defect degree of the graphite substrate before coating and eliminates some extreme points, by analyzing the I... D / I G The coating condition of graphite surfaces can be determined with simple data processing, and the accuracy of coating rate calculation is high, showing a significant advantage in assessing the uniformity of graphite surface coating. Furthermore, the coating is obtained through Raman imaging spectra. D and I G The ratio is used to distinguish between graphite substrate and coating layer. The selected sample covers a wide area, is representative, and provides intuitive and accurate characterization results.
[0059] 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.
[0060] Optionally, the coating agent is one or a mixture of two or more of the following: phenolic resin, epoxy resin, furan resin, glucose, starch, and asphalt.
[0061] In one possible implementation, in S1, more than 300 I's are obtained. D / I G Value, optionally, obtaining more than 400 I values. D / I G Values. For example, they can be 300, 350, 400, 450, 500, 550, or 600.
[0062] In one possible implementation, in S3, the top 15% of points are removed.
[0063] In one possible implementation, in S4, the first 15% of the points and / or the last 15% of the points are removed.
[0064] In one possible implementation, in S1, the scanning range of the Raman surface scan detection is 200μm≤X≤200μm; 200μm≤Y≤200μm.
[0065] In one possible implementation, -55μm≤X≤55μm can be selected as -50μm≤X≤50μm.
[0066] In one possible implementation, -55μm≤Y≤55μm can be selected as -50μm≤Y≤50μm.
[0067] In one possible implementation, the scanning point interval (step size) in the X and Y directions is 1 to 10 μm independently, and can be selected as 4 to 6 μm.
[0068] In one possible implementation, the graphite substrate is a single graphite particle, a secondary graphite particle, or a mixture of both.
[0069] A single particle refers to a non-agglomerated, primary particle.
[0070] In one possible implementation, the graphite substrate has a particle size Dv50 of 5–25 μm.
[0071] In one possible implementation, the coating layer is amorphous carbon;
[0072] In one possible implementation, the thickness of the coating layer is 10–50 nm.
[0073] 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.
[0074] Example 1
[0075] A graphite substrate (single-particle artificial graphite with a Dv50 of 12 μm) was mixed with petroleum asphalt powder (Dv50 of 3 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 1100℃, and the carbonization time was 6 hours. An amorphous carbon layer was formed on the outer surface of the graphite substrate, resulting in amorphous carbon-coated graphite.
[0076] 1g each of graphite substrate and coated graphite were prepared and analyzed using a Renishaw Raman spectrometer with a scanning step of 5μm. The area scan range was 50μm≤X≤50μm and 50μm≤Y≤50μm, with 441 points scanned. Raman imaging spectra were obtained within a range of 100×100μm*μm (see...). Figure 1 ) and scan data (I at each point) D / I G value).
[0077] I for graphite substrate D / I G The values are sorted in descending order, and the top 15% of the points are removed to obtain optimized data I; the largest value I in optimized data I is selected. D / I G The value is used as the critical point M between coated and uncoated graphite; for coated graphite, I... D / I G The values are sorted in descending order, and the top 15% and bottom 15% of the data are removed to obtain optimized data II.
[0078] The distributions of optimized data I and optimized data II are shown in the figure. Figure 2 .
[0079] Example 2
[0080] This embodiment is basically the same as Embodiment 1, except that the graphite substrate is artificial graphite with secondary particles (Dv50 is 14.5μm).
[0081] Raman imaging spectra were obtained after Raman surface scanning, see [link / reference]. Figure 3 The distributions of optimized data I and optimized data II are shown in [reference]. Figure 4 .
[0082] Example 3
[0083] This embodiment is basically the same as Embodiment 1, except that the graphite substrate is a mixture of single-particle and secondary-particle artificial graphite with a mass ratio of 10:7 (Dv50 is 13.5μm). The average particle size of the coated graphite is 14μm.
[0084] Raman imaging spectra were obtained after Raman surface scanning, see [link / reference]. Figure 5 The distributions of optimized data I and optimized data II are shown in [reference]. Figure 6 .
[0085] Example 4
[0086] This embodiment is basically the same as Embodiment 1, except that:
[0087] Optimized data I is the data obtained after removing the top 10% of points.
[0088] Optimized Data II is the data obtained after removing the top 10% and bottom 10% of the data points.
[0089] The distributions of optimized data I and optimized data II are shown in the figure. Figure 7 .
[0090] Example 5
[0091] This embodiment is basically the same as embodiment 2, except that:
[0092] Optimized data I is the data obtained after removing the top 10% of points.
[0093] Optimized Data II is the data obtained after removing the top 10% and bottom 10% of the data points.
[0094] The distributions of optimized data I and optimized data II are shown in the figure. Figure 8 .
[0095] Example 6
[0096] This embodiment is basically the same as embodiment 3, except that:
[0097] Optimized data I is the data obtained after removing the top 10% of points.
[0098] Optimized Data II is the data obtained after removing the top 10% and bottom 10% of the data points.
[0099] The distributions of optimized data I and optimized data II are shown in the figure. Figure 9 .
[0100] Example 7
[0101] This embodiment is basically the same as Embodiment 1, except that:
[0102] Optimized data I is the data obtained after removing the top 20% of points.
[0103] Optimized Data II is the data obtained after removing the top 20% and bottom 20% of the data points.
[0104] The distributions of optimized data I and optimized data II are shown in the figure. Figure 10 .
[0105] Example 8
[0106] This embodiment is basically the same as embodiment 2, except that:
[0107] Optimized data I is the data obtained after removing the top 20% of points.
[0108] Optimized Data II is the data obtained after removing the top 20% and bottom 20% of the data points.
[0109] The distributions of optimized data I and optimized data II are shown in the figure. Figure 11 .
[0110] Example 9
[0111] This embodiment is basically the same as embodiment 3, except that:
[0112] Optimized data I is the data obtained after removing the top 20% of points.
[0113] Optimized Data III is the data obtained after removing the top 20% and bottom 20% of the data points.
[0114] The distributions of optimized data I and optimized data II are shown in the figure. Figure 12 .
[0115] Performance testing
[0116] The following tests were performed on the uncoated graphite substrate and the coated graphite used in each embodiment:
[0117] 1. Testing of particle size Dv50
[0118] The particle size was tested according to the requirements of Appendix A of the national standard GB / T 24533-2019, using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.
[0119] 2. Capacity retention test
[0120] The button cell was manufactured according to Appendix G of GB / T24533-2019. The specific testing steps are as follows: 2 min rest; constant current 0.1C discharge to 0.01V; constant voltage 0.01V discharge with a cutoff current of 0.01C; 1 min rest; constant current 0.1C charging to 1.5V; 1 min rest; constant current 0.2C discharge to 0.01V; constant voltage 0.01V discharge with a cutoff current of 0.01C; 1 min rest; constant current 0.2C charging to 1.5V; 1 min rest; constant current 3.0C discharge to 0.01V; constant voltage 0.01V discharge with a cutoff current of 0.01C; 1 min rest; constant current 0.2C charging to 1.5V; 1 min rest.
[0121] Capacity retention rate at 3.0C / 0.2C = Q3.0C / Q0.2C × 100%
[0122] In the formula, Q0.2C is the specific capacity of constant current 0.2C discharge, and the unit is milliampere-hours per gram (mAh / g);
[0123] Q3.0C is the specific capacity of constant current 3.0C discharge, expressed in milliampere-hours per gram (mAh / g).
[0124] The test results are shown in Table 1.
[0125] K90 = (Dv90Dv10) / Dv50
[0126] Relative increase = (Capacity retention rate of coated graphite - Capacity retention rate of graphite substrate) / Capacity retention rate of graphite substrate * 100%
[0127] Table 1
[0128]
[0129]
[0130] As can be seen from the test data in Table 1, the Dv50 of the coated graphite in each embodiment increased by about 0.4 μm, and the particle size distribution K90 was less than 1.300, indicating a relatively uniform particle size distribution. Specifically, the coating rate in Example 1 was 65.55%, in Example 2 it was 71.20%, and in Example 3 it was 68.39%. The calculated coating rate results are consistent with the relative increase in capacity retention rate for each embodiment. The calculated coating rate results for Examples 4-6 and 7-9 are also consistent with the relative increase in capacity retention rate for each embodiment. This indicates that the evaluation method provided in this application has high accuracy in calculating the coating rate, and the evaluation results have high reference value. It can quickly and accurately evaluate the coating uniformity of coated graphite, showing significant advantages in assessing the uniformity of graphite surface coating.
[0131] 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 uniformity of the coating layer on the surface of coated graphite, characterized in that, include: 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 points within the scanning range. D / I G value; Coated graphite is a product obtained by coating and modifying a graphite substrate; S2, I for graphite substrate D / I G The values are sorted in descending order, and the top 10% to 20% of the points are removed to obtain optimized data I; Select the largest I in the optimized data I D / I G The value is used as the critical point M; S3, I for coated graphite D / I G The values are sorted in descending order, and the first 10% to 20% of the points and the last 10% to 20% of the points are removed to obtain optimized data II; S4. Calculate the coating ratio K of the coated graphite: K = A / B In the formula, A represents the optimized data in II. D / I G The number of points with values greater than M, where B is the total number of points in optimized data II.
2. The method for evaluating the uniformity of graphite surface coating according to claim 1, characterized in that, In S1, obtain more than 300 I D / I G Value, optionally, obtain more than 400 I values. D / I G value.
3. The method for evaluating the uniformity of graphite surface coating according to claim 1, characterized in that, In S3, the top 15% of points are removed.
4. The method for evaluating the uniformity of graphite surface coating according to claim 1, characterized in that, In S4, the top 15% of points and / or the bottom 15% of points are removed.
5. The method for evaluating the uniformity of graphite surface coating 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 independently 1~10μm.
6. The method for evaluating the uniformity of graphite surface coating according to claim 5, characterized in that, -55μm≤X≤55μm, can be selected as -50μm≤X≤50μm.
7. The method for evaluating the uniformity of graphite surface coating according to claim 5, characterized in that, -55μm≤Y≤55μm, can be selected as -50μm≤Y≤50μm.
8. The method for evaluating the uniformity of graphite surface coating according to any one of claims 1-7, characterized in that, The scanning sampling intervals in the X and Y directions are 4–6 μm, respectively.
9. The method for evaluating the uniformity of graphite surface coating according to any one of claims 1-7, characterized in that, The graphite substrate is a single graphite particle, a secondary graphite particle, or a mixture of both. Optionally, the particle size Dv50 of the graphite substrate is 5 to 25 μm.
10. The method for evaluating the uniformity of graphite surface coating according to any one of claims 1-7, characterized in that, The coating layer is amorphous carbon; And / or the thickness of the coating layer is 10–50 nm.