Oxygen Bridges of CoTe2/Co─O─NC Enhancing Adsorption-Catalysis of Polysulfide for Stable Lithium–Sulfur Batteries

Lithium-sulfur batteries are regarded as candidates for next-generation energy storage systems, but theirslow reaction kinetics and shuttle effect severely hinder their practical applications. One of the key solutions is to design and apply efficient, highly stable and long-life catalysts. Herein, a nanostructured CoTe2/Co-O-NC electrocatalytic material was developed to achieve effective adsorption and bidirectional catalytic conversions of lithium polysulfides (LiPSs). Results showed that oxygen bridges (Co-O-C) formed in the CoTe2/Co-O-NC not only effectively shifted d-band center of the cobalt near its Fermi level to enhance adsorption of LiPSs, but also strengthened the built-in electric fields of CoTe2/Co heterojunctions to reduce energy barrier for sulfur conversion. Deposition and dissociation of Li2S were significantly enhanced during charging/discharging processes. Durability of highly active catalyst was significantly improved, and rapid cross-interfacial charge transfer was also achieved. The synthesized S/CoTe2/Co-O-NC cathode exhibited an initial capacity of 1498 mAh g-1 at 0.1 C, and its decay rate of capacity over 500 cycles at 0.5 C was only 0.046 %. LiS pouch cells using the cathode showed an energy density of 368 Wh kg-1 and areal capacity of 7.7 mAh cm-2 at a sulfur loading of 6.7 mg cm-2, with an electrolyte/sulfur ratio of 4 µL mg-1.