Ultrafine ZnS quantum dots decorated reduced graphene oxide composites derived from ZIF-8/graphene oxide hybrids as anode for sodium-ion batteries

Abstract

Ultrafine ZnS quantum dots (QD) with sub-10 nm-scale decorated reduced graphene oxide composites is prepared by a very simple and low-energy two-step method. First, we prepare zeolitic imidazolate frameworks (ZIFs) and graphene oxide composites by stirring at room temperature. Then, the ZnS quantum dots and reduced graphene oxide composites (ZnS/GAs) is obtained by refluxing and annealing. Because of the smaller nanosize of ZnS and the addition of reduced graphene oxide, the composites exhibit the excellent specific capacity and the superior cycle performance for ZnS-based anodes. Meanwhile, N-doped carbon and reduced graphene oxide composites (NC/GAs) is also prepared by direct carbonization of zeolitic imidazolate frameworks and graphene composites. The ZnS/GAs is tested for SIBs; The capacity is still stable at 539 mAh/g at 100 mA/g, 512 mAh/g at 200 mA/g and 456 mAh/g at 500 mA/g after 100 cycles. Even when the current density is increased to 1 A/g, the capacity can still reach 362 mAh/g after 300 cycles. The NC/GAs is also tested for SIBs; the capacity is still stable at 283 mAh/g at 100 mA/g after 100 cycles and can still achieve 202 mAh/g at 1 A/g after 1000 cycles.