Tungsten Carbide as a Highly Efficient Catalyst for Polysulfide Fragmentations in Li-S Batteries

Abstract

The sluggish disproportionation of short-chain lithium polysulfides, Li2Sx is known to be one of the major causes to limit the rate capability of lithium sulfur batteries. Herein, we report that tungsten carbide not only affords strong sulfiphilic surface moieties but also provides an efficient catalysis to enhance the polysulfide fragmentation, leading to a drastic improvement in the electrode kinetics. We show that tungsten carbide acts as a superb anchoring material for the long-chain polysulfide and also promotes the dissociation of short-chain polysulfide during the electroreduction process. This leads to a high-rate performance of the composite cathode loaded with tungsten carbide, delivering a markedly enhanced discharge capacity of 780 mA h g(-1) at a high current rate of 5 C, when it is applied with a combination of a carbon-coated separator for the polysulfide confinement. Hence, this work presents a new strategic approach for a high-power lithium-sulfur battery.