Design rules for anion-doped catalysts revealed by p-p-s orbital coupling in Li-S chemistry

A rational design principle for selecting optimal anion dopants in transition-metal compounds to enhance sulfur redox activity is lacking in Li-S batteries. Herein, we propose an accurate p-p-s orbital electronic coupling descriptor (involving the p-orbitals of anion dopants and anions in transition-metal compounds and the s-orbitals of Li in lithium polysulfides) as a criterion for choosing anion dopants to guide the development of efficient anion-doped Li-S catalysts through machine-learning, theoretical, and experimental validation. We reveal the relationship between the electronic properties of various anion-doped WSe2 and the thermodynamics and kinetics of sulfur redox. Our findings show that moderate p-p-s orbital electronic coupling optimizes polysulfide adsorption, facilitating Li2S nucleation and decomposition, thereby minimizing Gibbs free energy and maximizing catalytic efficiency for sulfur redox. A volcano relationship between the p-p-s coupling strength and catalytic activity is established. The optimal B-WSe2/MXene catalyst achieves a ~ 3 Ah pouch cell with 430 Wh kg−1 specific energy and good cycle life (81.3% capacity retention over 71 cycles). These findings provide a guideline for designing efficient anion-doped Li-S catalysts with moderate p-p-s coupling to enable rapid sulfur catalytic conversion in Li-S batteries. The mechanism of how different anion dopants influence the catalytic performance for sulfur species is currently lacking systematic theoretical studies. Here, an accurate p-p-s electronic coupling descriptor was proposed as a criterion to guide the design of anion-doped Li-S catalysts.