Micro-/mesoporous Co-NC embedded three-dimensional ordered macroporous metal framework as Li-S battery cathode towards effective polysulfide catalysis and retention

Abstract The practical utilization of lithium-sulfur (Li-S) batteries is obstructed by the shuttle effect and sluggish conversion kinetics of the lithium polysulfides (LiPS). Herein, cobalt nanoparticles embedded N-doped carbon composite (Co-NC) decorated metallic tin with three-dimensionally ordered macroporous (3DOM) structure is designed to deal with these issues. The ordered interconnected macropores of the unique hierarchical structure can provide smooth Li ion transport, and the micro-/mesopores of Co-NC derived from ZIF-67 can trap polysulfides. Additionally, the highly conductive metal Sn as 3DOM skeleton accelerates charge transfer and strengthens the LiPS adsorption. Meanwhile, the embedded Co-NC further facilitates the polar adsorption of LiPS as well as its conversion kinetics. Benefiting from these features, the Co-NC@Sn (NH3) composite shows a relatively low capacity fading rate of 0.045 % per cycle over 500 cycles at 1 C. Even with raised sulfur loading of 5.2 mg cm−2, a high areal capacity of 4.65 mAh cm−2 can be obtained. Pouch cell fabricated with Co-NC@Sn (NH3) delivers a high discharge capacity of 701 mAh g−1 under high sulfur loading of 4.50 mg cm−2, implying the superiority of the S/Co-NC@Sn (NH3) cathode. This work provides a new strategy in efficient sulfur immobilizer design for advanced Li-S batteries development.