Ni-doped CoTe with optimized p-band center for boosting polysulfide conversion kinetics in lithium-sulfur batteries

Developing an effective electrocatalyst to regulate the kinetics of the sulfur redox reaction is essential for inhibiting polysulfide shuttling in Li-S batteries. Here, the electronic structure of CoTe, modulated by cation doping, is systematically investigated to elucidate how orbital hybridization optimizes sulfur redox electrocatalysis. Among the cation-doped CoTe compounds, the introduction of Ni dopants results in the most significant shift of the p-band center of CoTe (Ni-CoTe) towards the Fermi energy level, which facilitates the formation of numerous Te vacancies on the CoTe surface. This structural configuration endows CoTe with a multitude of active sites that bind polysulfide intermediates, lowering the activation energy (Ea) of the sulfur reduction reaction, specifically reducing the Ea for the conversion of lithium polysulfides to Li2S from 0.73 eV to 0.65 eV. As a result, the Li-S battery with Ni-CoTe catalyst delivers exceptional cyclability, with a low-capacity decay of 0.049% per cycle over 1,000 cycles at 2.0 C. Moreover, an initial areal capacity of 13.5 mAh cm-2 at 0.02 C is achieved with a high sulfur loading (10.0 mg cm-2) and a low electrolyte-to-sulfur ratio (5.0 µL mg-1). These findings will provide fundamental insights into orbital-level catalyst design principles for advanced sulfur electrochemistry.