Utilization of impurities and carbon defects in natural microcrystalline graphite to prepare silicon-graphite composite anode for high-performance lithium-ion batteries

Impurities and carbon defects generally hinder practical application of microcrystalline graphite as anode material for lithium-ion batteries. However, the impurities and carbon defects of the natural microcrystalline graphite are found to be the active sites to catalyze silicon deposition during the chemical vapor deposition process. In this work, the impurities and carbon defects of prepared anode material are wrapped by double coatings that are combined by the silicon nanowires and the carbon layer. The composite anode material exhibits a high capacity of 640 mA h g(-1) at a current density of 186 mA g(-1) after 250 cycles. The results of the density functional theory calculation reveal that the existence of impurities and carbon defects on graphite surface enhances the absorption energy of graphite to silicon during chemical vapor deposition process at 900 degrees C. By utilizing the impurities and carbon defects, the natural microcrystalline graphite can be employed as a new and low-cost anode material to fabricate the high-performance lithium-ion batteries.