Facilitating sulfur species capture and bi-directional redox in Li-S batteries with single-atomic Co-O2N2 coordination structure

Lithium-sulfur (Li-S) batteries suffer from the shuttle effect of soluble lithium polysulfides (LiPSs) and slow redox kinetics, significantly limiting their practical application. Although single-atom catalysts (SACs) offer a promising strategy to address these challenges, designing materials with optimal adsorption force and high catalytic activity remains a grand challenge. Here, we present a cobalt (Co)-based SAC with unique Co-O2N2 coordination structures for Li-S batteries. Both experimental and theoretical studies demonstrate that O, N-coordinated Co single atoms anchored on a porous carbon framework (Co/NOC) effectively capture LiPSs and dramatically catalyze bidirectional polysulfide conversion. The expanded carbon layer spacing facilitates lithium ions diffusion and maximizes the exposure of active sites. As a result, Li-S batteries incorporating Co/NOC as separators exhibit outstanding rate performance (906.6 mAh g−1 at 3 C) and exceptional cycling stability, even at −10 °C. Furthermore, with a high sulfur loading of 12.0 mg cm−2, the areal specific capacity reaches up to 12.36 mAh cm−2. This work provides some useful insights for the design of high-performance SACs for Li-S batteries.