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CN-121994769-A - Evaluation method for uniformity of coating layer on surface of coated graphite

CN121994769ACN 121994769 ACN121994769 ACN 121994769ACN-121994769-A

Abstract

The application relates to the technical field of graphite cathode materials of lithium ion batteries and discloses an evaluation method of uniformity of a coating layer on the surface of coated graphite, which comprises the following steps that S1, raman surface scanning detection is carried out on a graphite substrate and coated graphite by a laser Raman spectrometer respectively to obtain I D /I G values of a plurality of points in a scanning range; S2, carrying out descending arrangement on the I D /I G values of the graphite base material, eliminating the first 10% -20% of points to obtain optimized data I, selecting the largest I D /I G value in the optimized data I as a critical point M, S3, carrying out descending arrangement on the I D /I G values of the coated graphite, eliminating the first 10% -20% of points and the last 10% -20% of points to obtain optimized data II, and S4, calculating the coating rate K of the coated graphite, wherein K=A/B. The application has high accuracy of calculating the coating rate.

Inventors

  • YI RONGQI
  • WANG SHUAIGANG
  • LIU YIQUN
  • ZHANG JIE

Assignees

  • 万华化学集团电池科技有限公司
  • 万华化学(烟台)电池产业有限公司
  • 万华化学(烟台)电池材料科技有限公司

Dates

Publication Date
20260508
Application Date
20241029

Claims (10)

  1. 1. The method for evaluating the uniformity of the coating layer on the surface of the coated graphite is characterized by comprising the following steps of: S1, carrying out Raman surface scanning detection on a graphite substrate and coated graphite by a laser Raman spectrometer respectively to obtain I D /I G values of a plurality of points in a scanning range; The coated graphite is a product obtained by coating and modifying a graphite substrate; S2, carrying out descending arrangement on I D /I G values of the graphite base material, and eliminating the points of 10% -20% of the previous points to obtain optimized data I, wherein the largest I D /I G value in the optimized data I is selected as a critical point M; s3, carrying out descending arrangement on I D /I G values of the coated graphite, and eliminating the points of 10% -20% before and 10% -20% after to obtain optimized data II; S4, calculating a coating rate K of the coated graphite: K=A/B Wherein A is the number of points with I D /I G value > M in the optimized data II, and B is the total number of points in the optimized data II.
  2. 2. The method for evaluating uniformity of a graphite surface coating according to claim 1, wherein in S1, 300 or more values of I D /I G , optionally 400 or more values of I D /I G are obtained.
  3. 3. The method for evaluating uniformity of a graphite surface coating according to claim 1, wherein in S3, the top 15% of the points are eliminated.
  4. 4. The method for evaluating uniformity of a graphite surface coating according to claim 1, wherein in S4, the first 15% of the dots and/or the second 15% of the dots are removed.
  5. 5. The method for evaluating uniformity of a graphite surface coating according to claim 1, wherein in S1, a scanning range of a Raman scanning test is 200 μm or less and X≤200 μm or less, Y≤200 μm or less, and scanning dot intervals in X and Y directions are respectively and independently 1-10 μm.
  6. 6. The method for evaluating the uniformity of a graphite surface coating according to claim 5, wherein-55 μm≤X≤55. Mu.m, optionally-50 μm≤X≤50. Mu.m.
  7. 7. The method for evaluating the uniformity of a graphite surface coating according to claim 5, wherein-55 μm≤Y≤55 μm, optionally-50 μm≤Y≤50 μm.
  8. 8. The method for evaluating uniformity of a graphite surface coating according to any one of claims 1 to 7, wherein the scanning dot interval X and Y are each independently 4 to 6 μm.
  9. 9. The method for evaluating the uniformity of a coating on a graphite surface according to any one of claims 1 to 7, wherein the graphite substrate is a single particle or a secondary particle of graphite or a mixture of both; Optionally, the particle size Dv50 of the graphite substrate is 5-25 μm.
  10. 10. The method for evaluating the uniformity of a graphite surface coating according to any one of claims 1 to 7, wherein the coating is amorphous carbon; And/or the thickness of the coating layer is 10-50 nm.

Description

Evaluation method for uniformity of coating layer on surface of coated graphite Technical Field The application relates to the technical field of graphite cathode materials of lithium ion batteries, in particular to an evaluation method for uniformity of a coating layer on a surface of coated graphite. Background The lithium ion battery has the advantages of high energy density, high working voltage, long cycle life, environmental friendliness and the like, and is widely applied to the fields of 3C consumer products, power batteries and energy storage batteries. The common negative electrode materials in the lithium ion battery are graphite and silicon-based materials, wherein the artificial graphite becomes the most common negative electrode material of the current commercial lithium ion battery due to the advantages of high energy density, low voltage, good conductivity, abundant resources, low price and the like. However, due to slow lithium intercalation dynamics and low working potential of graphite, the stability and safety of the artificial graphite material under high-rate charge and discharge can not meet the application requirements of the quick-charging battery. The graphite negative electrode is coated by a solid-phase, liquid-phase or gas-phase carbonization deposition method, a layer of amorphous carbon is modified on the surface of the artificial graphite to construct a core-shell structure, so that the core of the modified negative electrode material retains the advantages of high capacity and low potential of the graphite material, the shell has good electrolyte compatibility, the first charge efficiency, the circulation stability and the rate capability of the graphite negative electrode can be effectively improved, and whether the coating layer on the surface of the graphite is comprehensive and uniform has obvious influence on the performance quality of products. Therefore, how to establish an effective evaluation method for the coating state is a current urgent problem to be solved. Disclosure of Invention The application provides a method for evaluating uniformity of a coating layer on the surface of coated graphite, wherein the coating uniformity is evaluated by Raman scanning results before and after coating a graphite substrate, and the evaluation result is more accurate. The application provides a method for evaluating uniformity of a coating layer on a surface of coated graphite, which comprises the following steps: S1, carrying out Raman surface scanning detection on a graphite substrate and coated graphite by a laser Raman spectrometer respectively to obtain I D/IG values of a plurality of points in a scanning range; The coated graphite is a product obtained by coating and modifying a graphite substrate; S2, carrying out descending arrangement on I D/IG values of the graphite base material, and eliminating the points of 10% -20% of the previous points to obtain optimized data I, wherein the largest I D/IG value in the optimized data I is selected as a critical point M; s3, carrying out descending arrangement on I D/IG values of the coated graphite, and eliminating the points of 10% -20% before and 10% -20% after to obtain optimized data II; S4, calculating a coating rate K of the coated graphite: K=A/B Wherein A is the number of points with I D/IG value > M in the optimized data II, and B is the total number of points in the optimized data II. In an alternative embodiment, in S1, 300 or more I D/IG values are obtained, alternatively 400 or more I D/IG values are obtained. In an alternative embodiment, in S3, the top 15% of the dots are culled. In an alternative embodiment, in S4, the first 15% of the points and/or the last 15% of the points are culled. In an alternative implementation mode, in S1, the scanning range of the Raman scanning detection is 200 μm or less and X≤200 μm or less, Y≤200 μm or less, and the scanning point interval in the X and Y directions is 1-10 μm respectively and independently. In an alternative embodiment of the present invention, X is less than or equal to 55 mu m and less than or equal to 55 mu m, X is more than or equal to-50 μm and less than or equal to 50 μm. In an alternative embodiment of the present invention, Y is less than or equal to 55 mu m and less than or equal to 55 mu m, Y is more than or equal to-50 μm and less than or equal to 50 μm. In an alternative implementation mode, the X-direction and the Y-direction of the scanning dot taking interval are respectively and independently 4-6 mu m. In an alternative embodiment, the graphite substrate is a single particle or a secondary particle of graphite or a mixture of both; Optionally, the particle size Dv50 of the graphite substrate is 5-25 μm. In an alternative embodiment, the coating is amorphous carbon; And/or the thickness of the coating layer is 10-50 nm. The technical scheme of the application has the following advantages: 1. The evaluation method for the uniformity of the coating laye