Facet-Engineered Tungsten Disulfide for Promoting Polysulfide Electrocatalysis in Lithium-Sulfur Batteries.

Distinct facets of an electrocatalyst can promote polysulfide (Li2Sn (n = 4, 6, 8) and Li2Sm (m = 1, 2)) redox kinetics in lithium-sulfur (Li-S) battery chemistry. Herein, we report that the (100) facet of tungsten disulfide (e-WS2) generated in situ by electrochemical pulverization exhibits onset potentials of 2.52 and 2.32 V vs Li/Li+, respectively, for the reduction of polysulfides Li2Sn and Li2Sm, which is unprecedented till date. In a comparable study, bulk WS2 was synthesized ex situ. The transmission electron microscopy (TEM) analysis reveals that the (100) facet was dominant in e-WS2, while the (002) facet was pronounced in bulk WS2. The density functional theory (DFT) analysis indicates that the (100) facet displays metallic-like behavior, which is highly desired for enhanced polysulfide redox kinetics. We believe that the e-WS2 produced can potentially be an excellent electrocatalyst for other applications such as hydrogen evolution reaction (HER), photocatalysis, and CO2 reduction.