Enhancing Bidirectional Sulfur Conversion Through p–d Orbital Hybridization via Vacancy Engineering

ABSTRACT Lithium–sulfur batteries (LSBs) have garnered significant concern as materials with high energy density for energy storage. Nevertheless, their severe shuttle effect and delayed redox kinetics limit their practical application. Herein, a strategy based on the regulation of oxygen vacancy concentration in CoWO 4 has been proposed to accelerate polysulfide kinetics. Experiments and density functional theory calculations reveal that catalytic materials with the appropriate number of oxygen vacancies (CWO‐M) have moderate adsorption energy and optimal catalytic capacity for polysulfides due to strong p–d orbital hybridization. More importantly, CWO‐M not only accelerates the reduction of sulfur during discharge but also significantly accelerates the oxidation of Li 2 S during charging, showing a favorable bidirectional catalytic effect. Benefiting from these unique advantages, the CWO‐M/S‐based battery exhibits an excellent rate performance of 768 mAh g −1 at 2 C and a capacity retention of 91.1% after 100 cycles at 0.2 C. Stable cycling performance with a high capacity of nearly 4 mAh cm −2 was achieved even after 100 cycles at a high sulfur loading of 8.02 mg cm −2 and a low electrolyte/sulfur (E/S) ratio of 8 µL mg S −1 . This work provides significant insights into bidirectional catalysts by modulating the oxygen vacancy concentration for application in LSBs.