Facile synthesis of novel Si nanoparticles–graphene composites as high-performance anode materials for Li-ion batteries

Abstract

Improving the Li storage properties of a Si negative electrode is of great significance for Li-ion batteries. A major challenge is to fabricate Si-based active materials with good electronic conduction and structural integrity in the process of discharging and charging. In this study, novel Si nanoparticles–graphene composites have been synthesized by hybrid electrostatic assembly between positively charged aminopropyltriethoxysilane modified Si nanoparticles and negatively charged graphene oxide, followed by thermal reduction. Commercially available Si nanoparticles are well embedded and uniformly dispersed into the graphene sheets, and the typically wrinkled graphene sheets form a network and cover the highly dispersed Si nanoparticles well. No any obvious aggregation of the Si nanoparticles can be found and many nanospaces exist around the Si nanoparticles, which provide buffering spaces needed for volume changes of Si nanoparticles during insertion/extraction of Li. High capacity and long cycle life (822 mA h g⁻¹ after 100 cycles at a current density of 0.1 A g⁻¹) have been realized in the novel Si nanoparticles–graphene composites for Li-ion batteries. The excellent electrochemical performance is ascribed to the uniform distribution of Si nanoparticles and graphene, which effectively prevents aggregation and pulverization of Si nanoparticles, keeps the overall electrode highly conductive, and maintains the stability of the structure.