Spherical graphite produced from waste semi-coke with enhanced properties as an anode material for Li-ion batteries

"Turning waste into treasure" is of significance for sustainable development nowadays. Semi-coke in fine particles, abandoned as solid waste, has a less commercial value in the metallurgical industry and also causes environmental contamination. In this research, man-made graphite was prepared by the facile graphitization of semi-coke using silicon as the catalyst at 2300 °C. The obtained sample revealed spherical morphology and a high degree of graphitization with a small specific surface area. Furthermore, as the anode material for lithium-ion batteries, the sample displayed excellent lithium storage properties, delivering high delithiation capacity of 347.06 mA h g^-1 at 0.05C, with the capacity even reaching 162.3 mA h g^-1 at 3C. An excellent cycle life was displayed with capacity retention of 97.7% at 0.5C after 700 cycles. Generally, SG obtained can serve as an anode material in consideration of the following predominant advantages: (i) a raw material at a lower cost; (ii) the lower charge/discharge plateau voltage after graphitization at 2300 °C; (iii) an ultra-high rate performance and excellent cycle retention at a higher rate; (iv) retention of the spherical structure without retreatment. Also, the one-step heat treatment was easier to conduct and handle. The important advantages of the samples give us a clear direction towards large-scale production.