A novel approach to fabricate Si@carbon/reduced graphene oxides composite (Si@C/RGO) assisted by polyaniline (PANI) is developed. Here, PANI not only serves as "glue" to combine Si nanoparticles with graphene oxides through electrostatic attraction but also can be pyrolyzed as carbon layer coated on Si particles during subsequent annealing treatment. The assembled composite delivers high reversible capacity of 1121 mAh g(-1) at a current density of 0.9 A g(-1) over 230 cycles with improved initial Coulombic efficiency of 81.1%, while the bare Si and Si@carbon only retain specific capacity of 50 and 495 mAh g(-1) at 0.3 A g(-1) after 50 cycles, respectively. The enhanced electrochemical performance of Si@C/RGO can be attributed to the dual protection of carbon layer and graphene sheets, which are synergistically capable of overcoming the drawbacks of inner Si particles such as huge volume change and low conductivity and providing protective and conductive matrix to buffer the volume variation, prevent the Si particles from aggregating, enhance the conductivity, and stabilize the solid-electrolyte interface membrane during cycling. Importantly, this method opens a novel, universal graphene coating strategy, which can be extended to other fascinating anode and cathode materials.
Keywords: Si particles; dual protection; graphene; lithium-ion batteries; polyaniline assistance.