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CN-121990568-A - S-doped g-C3N4 coated modified graphite material, preparation method thereof and lithium ion battery cathode

CN121990568ACN 121990568 ACN121990568 ACN 121990568ACN-121990568-A

Abstract

The invention relates to an S-doped g-C3N4 coated modified graphite material, a preparation method thereof and a lithium ion battery cathode. The method comprises the steps of mixing a g-C3N4 precursor with a sulfur source, then carrying out heat treatment under the condition of protective gas to obtain sulfur-doped graphite-phase carbon nitride S-g-C3N4, carrying out plasma modification treatment on the surface of a graphite material by adopting plasma reaction gas to obtain modified graphite, mixing the S-g-C3N4 with the modified graphite to obtain a mixed material, and calcining the mixed material under the condition of protective gas to obtain the S-doped g-C3N4 coated modified graphite material. The invention also provides the graphite material prepared by the method and a lithium ion battery anode prepared by the graphite material. The graphite material has higher conductivity, interface compatibility and structural stability.

Inventors

  • WANG JIONGHUI
  • JIA WENLI

Assignees

  • 五矿勘查开发有限公司

Dates

Publication Date
20260508
Application Date
20251212

Claims (19)

  1. 1. A preparation method of an S-doped g-C3N4 coated modified graphite material is characterized by comprising the following steps: S1, mixing a g-C3N4 precursor with a sulfur source according to the molar ratio of (1-20): 1, and then performing heat treatment at 400-800 ℃ under the condition of a protective gas to obtain sulfur-doped graphite-phase carbon nitride S-g-C3N4, wherein the sulfur doping amount is 5-30wt% based on 100% of the sum of the mass of sulfur and the mass of g-C3N 4; S2, carrying out plasma modification treatment on the surface of the graphite material by adopting a plasma reaction gas to obtain modified graphite, wherein the power of the plasma modification treatment is 50-300W, and the time is 5-30min; s3, mixing the S-g-C3N4 prepared in the step S1 with the modified graphite obtained in the step S2 according to the mass ratio of 1 (1-50) to obtain a mixed material, and calcining the mixed material at 500-1200 ℃ in a protective gas environment to obtain the S-doped g-C3N4 coated modified graphite material.
  2. 2. The method of claim 1, wherein the molar ratio of g-C3N4 precursor to sulfur source is (1-10): 1.
  3. 3. The method of claim 1, wherein the g-C3N4 precursor comprises one or a combination of two or more of melamine, urea, and cyanamide.
  4. 4. The method of claim 1, wherein the sulfur source comprises one or a combination of two or more of thiourea, cyanuric acid, elemental sulfur.
  5. 5. The method according to claim 1, wherein the heat treatment period in step S1 is 1 to 10 hours.
  6. 6. The method according to claim 5, wherein the heat treatment temperature in step S1 is 400-600 ℃ and the heat treatment time period is 3-8 hours.
  7. 7. The method of claim 1, wherein the sulfur doping level of step S1 is 5% -20%.
  8. 8. The method of claim 1, wherein the graphite material is natural spheroidal graphite, and the purity of the graphite material is >99%.
  9. 9. The method of claim 1, wherein the plasma reactant gas comprises one or a combination of two or more of O 2 、Ar、H 2 、N 2 、Ar/H 2 、Ar/O 2 .
  10. 10. The method according to claim 1, wherein the mixing process of S3 is performed by ball milling at a rotational speed of 100-200 r/min for a time of 5-30min.
  11. 11. The method according to claim 1, wherein the mass ratio of S-g-C3N4 to modified graphite is 1 (1-25).
  12. 12. The method according to claim 1, wherein the calcination time in step S3 is 1-15h.
  13. 13. The method according to claim 12, wherein the calcination temperature in step S3 is 600-1000 ℃ for 3-10 hours.
  14. 14. An S-doped g-C3N4 coated modified graphite anode material, characterized in that the anode material is prepared by the method of any one of claims 1-13.
  15. 15. The S-doped g-C3N4 coated modified graphite negative electrode material of claim 14, wherein the S-doped g-C3N4 coating layer has a thickness of 5-20nm.
  16. 16. The S-doped g-C3N4 coated modified graphite negative electrode material of claim 15, wherein the S-doped g-C3N4 coating layer has a thickness of 8-15nm.
  17. 17. The S-doped g-C3N4 coated modified graphite negative electrode material of claim 1, wherein the S-doped g-C3N4 coated modified graphite material has an S-doped content of 0.1% -10%.
  18. 18. The S-doped g-C3N4 coated modified graphite negative electrode material of claim 17, wherein the S-doped g-C3N4 coated modified graphite material has an S-doped content of 0.1% -5%.
  19. 19. A lithium ion battery negative electrode, which is characterized in that the lithium ion battery negative electrode is prepared from the S-doped g-C3N4 coated modified graphite negative electrode material according to any one of claims 14-18.

Description

S-doped g-C3N4 coated modified graphite material, preparation method thereof and lithium ion battery cathode Technical Field The invention belongs to the technical field of battery preparation, and particularly relates to an S-doped g-C3N4 coated modified graphite material, a preparation method thereof and a lithium ion battery cathode. Background At present, graphite materials are dominant in the field of negative electrodes of lithium ion batteries, and natural graphite is widely paid attention to due to wide sources and low cost. However, the natural graphite cathode still faces significant challenges in practical application, namely, the anisotropic property of the layered structure of the natural graphite cathode leads to uneven volume expansion and shrinkage in the lithium ion intercalation/deintercalation process, particle pulverization, electrode structure damage and contact failure between active substances and a current collector, and meanwhile, the natural graphite has limited intrinsic conductivity and lithium ion diffusion rate, so that the charge transfer impedance of the electrode is higher. The above problems severely limit the use of natural graphite in high performance batteries. The coating method is regarded as one of the most common and effective strategies for improving the performance of natural graphite, and aims to buffer volume change, reduce active surface exposure to inhibit electrolyte side reaction and improve interface characteristics by constructing a protective coating layer on the surface of graphite particles, however, the prior coating technology has the core defects that the intrinsic conductivity of the coating layer such as amorphous carbon or polymer is insufficient, the electronic/ionic conductivity is lower, the overall charge transfer impedance can be aggravated instead of being improved, the physical adhesion or weak interaction between the coating layer and a graphite substrate is mostly poor, strong chemical bonding is lacked, interfacial stripping or contact failure easily occurs under long-term charge and discharge stress, the protective effect is lost, the mechanical strength and flexibility of the traditional coating layer are insufficient, the anisotropic expansion of the graphite particles is difficult to effectively restrict, the traditional coating layer can be broken or pulverized in circulation, the structural integrity of an electrode cannot be permanently maintained, and the traditional coating material is lack of polar functional groups capable of remarkably improving the interfacial compatibility of the electrode/electrolyte and has limited improvement on lithium ion interface transmission dynamics, so that the traditional coating strategy is difficult to improve the conductivity, the interfacial bonding force and the stability are improved, and the performance space is limited. Therefore, developing an innovative modification technology capable of simultaneously and remarkably reducing charge transfer impedance of the graphite negative electrode, effectively inhibiting volume expansion and particle agglomeration in the circulation process, and ensuring strong interface combination between a coating layer and a substrate is important for improving comprehensive performance of the natural graphite negative electrode. Disclosure of Invention In order to solve the technical problems, the invention aims to provide an S-doped g-C3N4 coated modified graphite material and a preparation method thereof. Through the synergistic effect of S-doped g-C3N4 cladding and plasma modified graphite, the conductivity, interface compatibility and structural stability of the graphite can be obviously improved, and the electrochemical performance of the graphite is further improved. The invention also aims to provide a lithium ion battery anode which is prepared from the material. In order to achieve the above purpose, the invention provides a preparation method of an S-doped g-C3N4 coated modified graphite material, wherein the method comprises the following steps: S1, mixing a g-C3N4 (graphite phase carbon nitride) precursor with a sulfur source according to a molar ratio of (1-20): 1, and then performing heat treatment at 400-800 ℃ under the condition of protective gas to obtain S-g-C3N4 with specific sulfur doping content; s2, carrying out plasma modification treatment on the surface of the graphite material by adopting a plasma reaction gas to obtain modified graphite; s3, mixing the S-g-C3N4 prepared in the step S1 with the modified graphite obtained in the step S2 according to the mass ratio of 1 (1-50) to obtain a mixed material, and calcining the mixed material at 500-1200 ℃ in a protective gas environment to obtain the S-doped g-C3N4 coated modified graphite material. According to a specific embodiment of the present invention, preferably, the preparation method of the S-doped g-C3N4 coated modified graphite material provided by the present invention includes t