THE USING OF GAS CHROMATOGRAPHY FOR INVESTIGATION OF HYDROCARBON PYROLYTIC DEPOSITION ON MODIFIED NATURAL GRAPHITE

One of the most popular technologies for electrical energy storage currently remains lithium-ion batteries (LIB), in which various carbon materials can act as the active anode material, in particular natural graphite, characterized by stable electrochemical characteristics during repeated cycling of charging/discharging processes. The paper discusses the use of gas chromatography to optimize the conditions for the pyrolytic deposition of hydrocarbons onto modified (spheroidized) natural graphite, which is carried out to significantly improve the Coulomb efficiency of these carbon materials when used in LIBs. It was shown that the analysis of gases released from the pyrolysis reactor by gas chromatography makes it possible to choose carbon-containing precursors and the conditions of their pyrolytic heterophase decomposition for the formation of a uniform film of pyrolytic carbon on the surface of modified (spherolized) natural graphite. The using of gas chromatography in the analysis of released gases also makes it possible to minimize the processes of homophase pyrolytic decomposition of a carbon-containing precursor, leading to the formation of separate carbon phases, which can be characterized by extremely low values of reversible capacity for lithium. Analysis of the ratios of product concentrations during pyrolysis allows us to conclude that the pyrolysis mechanism remains unchanged throughout the entire duration of the process. It was shown that the profile of changes in the hydrogen content in the gas mixture coming from the reactor of the pyrolytic decomposition of carbon-containing precursors correlates with the trend of changes in the specific surface area of spheroidized graphite samples. The results obtained suggest that in the case of the unchanged mechanism of pyrolytic decomposition of a carbon-containing precursor, its unchanging concentration and the heterophasic nature of pyrodecomposition, analysis of the profile of changes in the hydrogen content emanating from the reactor can be used to select optimal conditions for pyrodeposition. For example, it can be used to select the pyrolysis duration necessary to saturate structural defects in the graphite matrix, the presence of which can lead to high irreversible capacity during the first cycles of lithium interclaring and deintercalation. For citation: Khaskov M.A., Naumova V.A., Karaeva A.R., Mordkovich V.Z. The using of gas chromatography for investigation of hydrocarbon pyrolytic deposition on modified natural graphite. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 65-72. DOI: 10.6060/ivkkt.20246710.13y.