High absorption and fast polysulfides conversion of duel functional separator based on mesoporous-WC/rGO composite for lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) are next-generation energy storage devices owing to their high specific capacities and energy densities; however, critical problems remain unsolved, such as insulating sulfur as an active material and the dissolution of Li polysulfides into the liquid electrolyte during cycling, leading to low sulfur utilization, low rate performance, and rapidly decreasing capacity. Herein, we describe the synthesis of a nanocomposite structure comprising mesoporous tungsten carbide (meso-WC) and reduced graphene oxide (rGO) (meso-WC/rGO) and its application to an functional separator in LSBs. The resulting Li-S cell exhibits improved rate cycling performance: ~950 mAh g-1 at 1 C after 100 cycles. Moreover, even at a high sulfur loading of 3.0 mg cm-2, the Li-S cell with the meso-WC/rGO maintains enhanced performance, with a capacity of ~737 mAh·g-1 and a retention of 83% after 300 cycles. The Li-polysulfide shuttle effect was observed using H-type cells and adsorption tests. The enhanced performance results from suppression of the shuttle effect caused by the excellent adsorption of Li polysulfides, effective reuse of active materials, and promotion of the conversion reaction.