Molybdenum Carbide Nanostructures for Electrocatalytic Polysulfide Conversion in Lithium-Polysulfide Batteries
Introduction of proper cathode electrocatalysts in lithium-sulfur or lithium-polysulfide batteries can accelerate the polysulfide interconversion and suppress the shuttle effect. However, improvements are often limited especially under high sulfur loading. Herein, we prepare molybdenum carbide nanostructures and investigate their potential as the cathode electrocatalyst for lithium-polysulfide batteries. The product is prepared from the self-polymerization of dopamine in the presence of Mo7O246- ions, followed by high-temperature carburization. It features ultrasmall α-MoC1-x nanoparticles uniformly dispersed on the hierarchical carbonaceous support. Polysulfide adsorption experiments and electrochemical measurements show that this material has strong surface affinity toward polysulfides, and can greatly enhance their conversion rate, in particular the conversion of Li2S4‹–›Li2S2/Li2S. When assessed as the cathode electrocatalyst, it enables lithium-polysulfide batteries with large specific capacity (up to 1400 mAh g-1), impressive rate capability (800 mAh g-1 at 3200 mA g-1) and excellent cycling stability even at high sulfur loading.