Electrochemical graphitization transformation of deposited carbon for Li-ion storage: sustainable energy utilization from coke oven solid waste

Developing new precursors of synthetic graphite from harmful carbon-containing solid waste generated by coking enterprises has been an important topic in graphitization research for the world's green development and creating new energy. In this study, coke oven deposited carbon was used as a precursor to prepare graphite by a molten salt electrolysis method. The structure transformation law of deposited carbon and the changes of the O, N, and S atomic contents on the surface during the electrolysis process were explored. The results showed that deposited carbon is transformed into a graphitic structure with a graphitization degree of 0.74 and the conversion rate of O, N and S exceeds 50% in the molten CaCl₂ salt under 2.6 V at 900 °C for 8 h. The low-temperature graphitization transition process of deposited carbon assisted by an electric field was investigated by molecular simulation calculations. Deposited carbon-derived graphite was demonstrated as a useful negative electrode material for lithium-ion batteries and delivered a high reversible capacity of 325 mA h g⁻¹ and an excellent coulombic efficiency of 99.5% at 1C after 600 cycles, which could provide a reference for value-added utilization of carbon-containing solid waste in coking enterprises.