Accelerating dual-directional sulfur conversion through optimal p-band centers and interfacial charge redistribution for high-efficiency Li-S batteries

Abstract

Despite extensive investigation into various electrocatalysts to enhance the progressive redox transformations of sulfur species in Li-S batteries (LSBs), their catalytic abilities are often hindered by suboptimal adsorption-desorption dynamics and slow charge transfer. Herein, a representative Co_0.1Mo_0.9P/MXene heterostructure electrocatalyst with optimal p-band centers and interfacial charge redistribution is engineered as a model to expedite bidirectional redox kinetics of sulfur via appropriate Co doping and built-in electric field (BIEF) effect. Theoretical and experimental results corroborate that the optimal Co-doping level and BIEF heterostructure adjusts the p-band center of active phosphorus sites in Co_0.1Mo_0.9P/MXene to optimize the adsorption properties and catalytic performance of sulfur species, the BIEF between Co_0.1Mo_0.9P and MXene significantly decreases the activation energy as well as Gibbs free energy of rate-determining step, accelerates interfacial electron/Li⁺ transfer rate during cycling, thereby accelerating dual-directional sulfur catalytic conversion rate in LSBs. Consequently, the S/Co_0.1Mo_0.9P/MXene cathode attains a large initial capacity of 1357 mAh g⁻¹ at 0.2 ​C and a 500-cycle long stability (0.071% decay rate per cycle) at 0.5 ​C. Impressively, the high-loading S/Co_0.1Mo_0.9P/MXene cathode (sulfur loading: 5.2 ​mg ​cm⁻²) also presents a remarkable initial areal capacity (6.5 mAh cm⁻²) with superior cycling stability under lean electrolyte (4.8 ​μL mg_sulfur⁻¹) conditions, and its Li-S pouch cell delivers a high capacity of 1029.4 mAh g⁻¹. This study enhances the comprehension of catalyst effect in Li-S chemistry and provides important guidelines for designing effective dual-directional Li-S catalysts.