Homogeneously dispersed silicon/graphite composite toward enhanced lithium-ion batteries

Abstract

At present, silicon/graphite composite is the most promising anode material for high energy density lithium-ion batteries. However, during the preparation, nanoscale silicon will inevitably undergo agglomeration, which will cause serious volume changes and breakage during the charging/discharging process. How to achieve uniform dispersion of nanoscale silicon onto the surface of graphite becomes a great challenge. Here, by grafting functional groups on the surface of silicon, both the repulsive force between silicon particles and the binding force between silicon/graphite have been improved, thereby highly uniform dispersed silicon is achieved. After being coated with asphalt and etching off the functional groups, the conductivity and ion migration ability of the composite are further improved. Resultantly, the modified composite provides a high discharging capacity of 598.4 mAh·g−1 at 0.2C and can still maintain a high-capacity retention of 90.7 % and a small volume expansion rate of 30.8 % after 500 cycles.