RGO@MoS2 as the host-separator modifier with efficient polysulfides trapping and fast Li+ diffusion for lithium-sulfur batteries

Abstract

Lithium sulfur battery is widely regarded as the most promising next generation energy storage systems because of its high specific energy (2600 Wh kg−1). However，its commercial application is still limited by numerous challenges, including the insulation of charging/discharging products sulfur and Li2S2/Li2S, as well as the "shuttle effect" triggered by the soluble polysulfides. Herein, we report that a functional separator modified by a rGO@MOS2 composites comprising ultrathin MoS2 nanosheets in-situ growth on the surface of reduced graphene oxide (rGO). This composite boasts -an abundant mesoporous structure and large specific surface area can effectively adsorb lithium polysulfides (LiPSs). Additionally, the introduction of high conductive rGO and ultrathin MoS2 nanosheets with rich edge active sites can accelerate the catalytic transformation reaction from LiPSs to Li2S2/Li2S, thus inhibiting the "shuttle effect". In comparison to Li-S batteries without rGO@MoS2 composites, batteries equipped with the functional separator exhibit an impressive initial discharge capacity of 1125.4 mAh g−1 at 1 C, and retain at 910.4 mAh g−1 after 200 cycles, with a low capacity decay rate of 0.09 % per cycle, indicating excellent cyclic stability. Moreover, the areal capacity of the electrode with high sulfur loading mass of 4.1 mg cm−2 is 4.1 mAh cm−2, approaching the practical application standard at a current density of 0.1 C.