Enabling remarkable cycling performance of high-loading MoS2@Graphene anode for sodium ion batteries with tunable cut-off voltage

Abstract

Layer-structured transition-metal disulfides are considered as promising anode materials for sodium ion batteries (SIBs). However, large volume change over charge-discharge cycles is behind a major problem for mechanical failure, leading to low capacity, poor rate and cycling performance. In this work, we devise a one-step solvothermal method to construct reduced graphene oxide (RGO) aerogel containing nano-roses made of few-layer MoS2 petals, which exhibit significant enlargement in inter-layer spacing. Such MoS2@RGO composites are applied as SIBs anode to facilitate remarkable improvement of rate capacity (513.8 mAh g−1 at 0.1 A g−1 and 171.5 mAh g−1 at high current density 20 A g−1) and cycling stability (>80% capacity retention, 223.2 mAh g−1, after 500 cycles at 0.5 A g−1). Furthermore, theoretical calculations are employed to study the sodiation/de-sodiation mechanisms, which guide realization of high cycling stability beyond 1000 cycles, through applying a positive discharge cut-off voltage above 0.4 V to keep the layered structures from decomposition.