Improving Natural Microcrystalline Graphite Performances by a Dual Modification Strategy toward Practical Application of Lithium Ion Batteries

Microcrystalline graphite (MG), as a kind of natural graphite (NG), holds great potential for use as an anode material for lithium-ion batteries (LIBs) due to low raw material cost, good electrolyte compatibility, and relatively long cycle life. Nevertheless, the relatively low reversible capacity and poor initial Coulombic efficiency (ICE) of the MG anode largely limit its practical application in LIBs. In order to improve the lithium storage capacity of MG, three kinds of oxidant intercalators are applied to treat the original MG, and the as-obtained MG is further modified by a thin carbon layer. The results indicate that using H2SO4–C2H2O4 as oxidant intercalators and subsequent carbon coating layer modification are the optimum techniques, and they can increase the interlayer distance, introduce defects to decrease the volume expansion, and generate channels for fast Li+ diffusion. Meanwhile, the carbon coating layer can reduce the specific surface area of graphite and greatly improve the ICE and cycling performance. Especially, the OEMGC-2 anodes prepared by the dual modification strategies represent a high reversible capacity of 349.4 mA h g–1 at 0.2C with a satisfactory ICE of 90.2%, indicating that the MG can also be considered as a high performance and low-cost anode material of LIBs.