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

Abstract

Lithium–sulfur batteries are regarded as candidates for next-generation energy storage systems, but their slow 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 is developed to achieve effective adsorption and bidirectional catalytic conversions of lithium polysulfides (LiPSs). Results show that oxygen bridges (Co─O─C) formed in the CoTe₂/Co─O─NC not only effectively shift d-band center of the cobalt near its Fermi level to enhance adsorption of LiPSs but also strengthen the built-in electric fields of CoTe₂/Co heterojunctions to reduce energy barrier for sulfur conversion. Deposition and dissociation of Li₂S are significantly enhanced during charging/discharging processes. Durability of highly active catalyst is significantly improved, and rapid cross-interfacial charge transfer is also achieved. The synthesized S/CoTe₂/Co─O─NC cathode exhibits 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 is only 0.046%. Li─S pouch cells using the cathode show 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.