Graphitization Mechanisms and Electrochemical Performance of Needle Coke Anode for Li-ion Battery

Effects of heat-treatment temperature on the microstructure and electrochemical properties of coal based nee- dle coke were investigated by TG-DTG, XRD, SEM, XPS analysis and the charge/discharge, cyclic voltammetry curves. The graphitization mechanism of needle coke is suggested as well as the Li + extraction-insertion behaviors. With the heat-treatment temperature increasing, the graphite-like crystal grows continuously attended with a complicated process, including the arrangement of crystal along radial/axial direction, dislocation dispersion among graphite layers, hexagonal carbon formation, crystal edge dispersion and folded graphite layer turning to plane. Meanwhile, the driving-forces are far different for different process. When needle coke is graphitized at 2800℃, it exhibits a lower charge/discharge potential and stable charge/discharge platform, and the insertion capacitance of Li + can maintain at 305mAh/g even after charge/discharged for 40 cycles.