A scalable sulfuration of WS2 to improve cyclability and capability of lithium-ion batteries

Two-dimensional transition-metal dichalcogenides (WS2 and SnS2) have recently joined the family of energy storage materials (for lithium-ion batteries and supercapacitors) as a result of their favorable ion intercalation. So far, challenges in the synthesis of phase-pure WS2, restacking between WS2 nanosheets, low electronic conductivity, and the brittle nature of WS2, severely limit its use Li-ion battery application. Herein, we develop a facile low temperature solution sulfuration process to improve battery performance dramatically. The sulfuration process is demonstrated to be effective in converting WO3 impurities to WS2, and in repairing the sulfur vacancies, to improve cyclability and rate capability. Lithium-ion battery measurements demonstrate that the stable capacity of the WS2 anode could be enhanced by 48.4% via sulfuration reprocessing, i.e., from 381.7 to 566.8 mAh/g at a relatively high current density of 0.8 A/g after 50 cycles. We further show that the sulfuration process can be readily extended to other dichalcogenides, and may provide a class of versatile electrode materials for lithium-ion batteries with improved electrochemical characteristics.