Catalytic graphitization of coke and electrochemical performances of coke-based graphite

Abstract

The effect of minerals on the high-temperature graphitization process of coke was thoroughly investigated using by X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscope (SEM), physical adsorption instrument, etc. The structure-activity relationship between the microstructure of coke-based graphite and lithium storage performances was identified. The findings demonstrate that the microstructure of coke-based graphite is related to the mineral content and the final graphitization temperature affects the Si or Fe catalytic graphitization of coke. The appropriate amount of minerals as the catalyst can reduce the interlayer spacing, improve the graphitization degree and increase the crystallite size of the coke graphitization sample. The catalytic graphitization of coke involves the carbide transition, which is further confirmed by XRD and SEM-EDS analysis. By proper adding the mineral to the coke during the graphitization process, it is clear that the electrochemical performances of the synthetic graphite as anode for lithium-ion batteries can be improved obviously. Coke-based graphite DCG-20Si-2800 and DCG-30Fe-2800 as anode material show good comprehensive electrochemical performances. And the reversible specific capacities of both at 0.1 C are as high as 353.9 mAh/g and 361.9 mAh/g, respectively, which are quite close to the theoretical capacity of graphite (1 C = 372 mAh/g). Thus, the study successfully reveals the law of mineral catalysis in the graphitization process of coke and demonstrates the feasibility of coke-based graphite products as anode material. It can be expected that coke can be useful sources of artificial graphite if the graphitization process is adequately improved.