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

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 0.1 Mo 0.9 P/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 0.1 Mo 0.9 P/MXene to optimize the adsorption properties and catalytic performance of sulfur species, the BIEF between Co 0.1 Mo 0.9 P 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 0.1 Mo 0.9 P/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 0.1 Mo 0.9 P/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. Rational regulation of p -band centers and interfacial charge redistribution in phosphide-based heterostructures is proposed via the combination of optimal Co-doping levels and built-in electric field, the as-designed S/Co 0.1 Mo 0.9 P/MXene cathode demonstrates moderate adsorption for polysulfides, rapid electron/Li + transfer rate, and excellent bidirectional sulfur conversion kinetics. Consequently, it achieves a large initial capacity, a stable long-term lifespan with 500 cycles and a high areal capacity under high sulfur loading and low electrolyte conditions. • Co 0.1 Mo 0.9 P/MXene heterostructure catalysts with optimal p -band center and built-in electric field (BIEF) were devised. • The intrinsic synergistic mechanism of Co-doping and BIEF to regulate the p -band center of active-P sites and interfacial charge redistribution of heterostructure were uncovered. • S/Co 0.1 Mo 0.9 P/MXene cathode exhibits excellent 500-cycle long stability, high initial areal capacity under high S loading and lean electrolyte conditions.