One-step heat treatment to process semi-coke powders as an anode material with superior rate performance for Li-ion batteries

Abstract

“Turning waste into wealth” and sustainable development are bright themes of modern society. Semi-coke is mainly made up of coal but contains around 15 wt% impurities. Nevertheless, semi-coke powders with sizes smaller than 3 mm generally cannot be used in metallurgical industries and are abandoned as solid waste, resulting in environmental contamination. Herein, boron doping followed by facile one-step heat treatment in the range of 2100 to 2700 °C has been carried out to process semi-coke powder waste. Thereby, the semi-coke powders can be graphitized to give sample carbon content values of over 95%. The best product so-prepared delivered reversible capacities of 351.5 mA h g⁻¹ at 0.1C, and 322 mA h g⁻¹ at 1C. Surprisingly, the capacity was maintained at 314.3 mA h g⁻¹ after 300 cycles at 1C, giving a decline rate of only 2.4% and presenting superior rate performance.