WN nanocubes embedded on carbon mesh towards high-performance Li-S batteries: Balancing physical capture, chemical adsorption and catalysis capability

Lithium-sulfur batteries are deemed as to be one of the promising electrochemical energy storage systems due to the high theoretical energy density and low cost. However, the shuttle effect and the slow redox kinetics of polysulfides cause the low sulfur utilization and fast capacity fading, thus hindering the practical application of lithium-sulfur batteries. Herein, a hybrid composite constructed by porous conductive WN nanocubes embedded on carbon mesh (P-WN@CM) was first time proposed to modify separator for lithium-sulfur batteries, which exhibit a balance characteristic of physical capture, chemisorption and catalysis capability for lithium polysulfides (LiPSs). Specifically, both two dimensional carbon mesh and porous WN nanocubes with porous structure show strong physically capture effect for the soluble LiPSs, inhibiting them diffuse to Li metal anode. In addition, the porous conductive WN nanocubes present moderate chemisorption but high catalytic activity for LiPSs, efficiently promoting the redox process of sulfur-based species. As a result, the batteries assembled by PWN@CM modified separator exhibit a high specific capacity (1344 mAh g(-1) at 0.2C) and outstanding cycle performance (low capacity fading rate of 0.01 % per cycle after 1500 cycles at 5C). More surprisingly, a favorable stability can be achieved under high sulfur loading of 5.3 mg cm(-2). This work may provide a rational strategy for developing multifunctional materials for high-performance lithium-sulfur batteries.