Synthesis and lithium storage properties of Sn quantum dots/graphene composite

The Sn-based materials have been a focus as promising high-capacity electrode materials of lithium-ion battery. However, its poor cycling performance has severely restricted the large-scale practical applications. The Sn quantum dot/graphene (SnQds/rGO) composite electrode material was synthesized by chemical reduction method, using graphene oxide as the carrier. The Sn quantum dots with <10 nm were uniformly loaded on the surface of graphene. The experimental results show that the SnQds/rGO composite with Sn mass fraction of 90wt% has good comprehensive electrochemical performance. The first discharge capacity and Coulomb efficiency of the SnQds/rGO composite are 939 mAh/g and 66.6%, respectively. It’s discapacity can reach 621 mAh/g after 200 cycles and the capacity retention rate is 66.1%. The structure stability of SnQds/rGO composite is improve, meanwhile its impedance reduce, owing to the commposite of small size Sn quantum dots and graphenethe. As a result, the cycle performance and rate performance of the SnQds/rGO composite have been significantly improved. However, the initial Coulomb efficiency of SnQds/rGO composite decreases.