Understanding the role of graphene intercalation layers on both sides of sandwich structured graphene@MoS2@porous graphene anode in promoting sodium storage performance and stability

Abstract

Developing of sodium-ion batteries (SIBs) as potential energy storage technology owns tremendous significance. However, to realize the large-scale development of SIBs, the development of high performance, high safety, low cost anode materials bears the brunt. Molybdenum disulfide (MoS2) with graphene-like layered structure is considered as one of the most promising anode materials for SIBs because of its high theoretical capacity. But MoS2 unfortunately suffers from its drastic volume variation and poor electric conductivity during the sodiation/desodiation cyclic process, which result in unsatisfied battery capacity, rate capability and cycle stability. So, exploring rational MoS2-based materials as ideal anodes is still a huge challenge. Herein, a special structure of MoS2/porous graphene composite material with high electric conductivity and high structural stability is designed. Firstly, MoS2 is grown on the surface of porous graphene, and then graphene is coated on the other side of MoS2 to obtain sandwich-like structured graphene@MoS2@porous graphene (GR@MoS2@PG) composite material. Among them, the graphene intercalation layers on both sides of MoS2 play important roles in obtaining high reversible capacity and excellent stability, because they not only can enable reversible conversion of MoS2 and provide fast electron transfer and rapid diffusion of sodium ions, but also effectively buffer the volume contraction and expansion of MoS2 during repeated sodiation/desodiation cyclic process. The GR@MoS2@PG electrode displays a high reversible capacity (260 mAh g−1 at 1 A g−1), excellent rate capability (186 mAh g−1 at 10 A g−1) and long-term cycling life (above 200 mAh g−1 at 1.0 A g−1 after 1000 cycles).