Covalently bridged bond assembly of MoS2 lamellae onto a graphene sheet: an outstanding electrode for high rate and long-life lithium/sodium-ion batteries

Abstract

The practical application of Molybdenum sulphide (MoS2) electrodes has been hindered by its structural instability, and poor electrical conductivity. To enhance the cycle stability and rate performance of MoS2 in lithium/sodium-ion batteries (LIBs/SIBs), we synthesized a graphene-supported MoS2 composite (MoS2@rGO) with affluent covalent bridged bonds through a facile and scalable hydrothermal and annealing process. The covalent bridged bonds of Mo–S–C, Mo–O–C and C–O–S provide an effective charge transfer path between MoS2 and graphene, facilitating fast charge hopping and improving rate performance. As anode materials for LIBs, the MoS2@rGO exhibited exceptional long-term cycle life (906 mAh g−1 at 1.0 A g−1 after 400 cycles) and outstanding rate capability (1267.7/314.7 mAh g−1 at 0.1/6.5 A g−1). Additionally, the MoS2@rGO electrode demonstrated a stable reversible capacity of 521.7 mAh g−1 at 1.0 A g−1 after 700 cycles and excellent rate capabilities of 665.1 and 326.3 mAh g−1 at 0.1 and 10.0 A g−1 in SIBs. The edge Mo of MoS2 is directly coupled with the oxygen of the functional group on rGO, achieved by adjusting the pH value of the solution to tune the surface charge feature, can effectively enhance the structural stability of electrode even under higher current density.