Cobalt-Tungsten Bimetallic Carbide Nanoparticles as Efficient Catalytic Material for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation energy storage devices owing to their advantages such as high theoretical specific capacity and energy density. However, the shuttle effect of polysulfide intermediates and the slow electrochemical kinetics have a severe passive effect on the cycling stability and rate performance. A Co3 W3 C@C composite was prepared through a simple one-pot pyrolysis method and used as a modifying layer on a commercial separator. The obtained modified separator not only prevented the shuttle effect through both strong chemical interaction and a physical barrier toward polysulfides, but also acted as a catalytic membrane to catalyze the electrochemical redox of active sulfur species. By employing the coated separator, the cathode with 60 wt % sulfur delivered a high initial capacity of 1345 mAh g-1 at 0.1 A g-1 , excellent rate performance with a high capacity of 670 mAh g-1 even at 7 A g-1 , and outstanding cycle performance with a low decay rate of 0.06 % per cycle and an average Coulombic efficiency of 99.3 % within 500 cycles at 1 A g-1 . Even at a sulfur loading of 3 mg cm-1 , a high initial capacity of 869 mAh g-1 and 632 mAh g-1 after 200 cycles at 1 A g-1 were obtained. The results demonstrate the advantages of Co-W bimetallic carbide in preventing the shuttle effect and promoting the redox kinetics for high performance Li-S batteries.