Tungsten Oxide/Zirconia as a Functional Polysulfide Mediator for High-Performance Lithium–Sulfur Batteries

In this study, an effective strategy is proposed to overcome the limitations associated with the use of a Li2S cathode in lithium–sulfur (Li–S) batteries. Herein, tungsten oxide/zirconia (WO3/ZrO2) with a ratio of 3:7 is prepared and incorporated into a 2D compacted Li2S–graphene matrix through pelletization. The proposed composite material shows a great potential as cathode material for Li–S batteries. In the composite cathode, the high electrical conductivity of graphene and presence of a metastable high-pressure Li2S phase allows the direct conversion of Li2S to S8 during the first activation process, and simultaneously the incorporated tungsten oxide/zirconia particles act as a polysulfide mediator to block the outflow of soluble polysulfide into the electrolyte solution. Therefore, the composite cathode shows high interfacial stability and thus substantially extends the lifetime of the Li–S battery over 200 cycles at a high Li2S loading of 10 mg cm–2. The practical Li–S full battery fabricated by combining the composite cathode and graphite anode provides reliable cycling stability over 1500 cycles.