Covalent binding of Si nanoparticles to graphene sheets and its influence on lithium storage properties of Si negative electrode

Abstract

Improving the lithium storage properties of a Si negative electrode is of great significance for lithium 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, Si nanoparticles are covalently bound to the surface of graphene sheets via aromatic linkers through diazonium chemistry. The resulting Si–Ph–G nanocomposite delivers a delithiation capacity of 1079 and 828 mAh g−1 in the initial and 50th cycle at a current density of 300 mA g−1, respectively, with a capacity fading rate of 4.5 mAh g−1 per cycle. The composite still exhibits a reversible capacity of 350 mAh g−1 in the 40th cycle even at a rate of 4.0 A g−1. TEM images show that Si nanoparticles are homogeneously distributed on the graphene sheets in the process of lithiation and delithiation. The excellent electrochemical performance of the Si–Ph–G composite is ascribed to the covalent linkages between the Si nanoparticles and graphene sheets, which prevent severe stacking of the graphene sheets and aggregation of Si nanoparticles. The finding of this study offers an alternative approach to improve the lithium storage properties of a Si negative electrode by chemically anchoring electroactive materials to a conducting matrix.