Energizing Robust Sulfur/Lithium Electrochemistry via Nanoscale-Asymmetric-Size Synergism

Sluggish redox kinetics and dendrite growth perplex the fulfillment of efficient electrochemistry in lithium-sulfur (Li-S) batteries. The complicated sulfur phase transformation and sulfur/lithium diversity kinetics necessitate an all-inclusive approach in catalyst design. Herein, a compatible mediator with nanoscale-asymmetric-size configuration by integrating Co single atoms and defective CoTe_2-x (Co_SA-CoTe_2-x@NHCF) is elaborately developed for regulating sulfur/lithium electrochemistry synchronously. Substantial electrochemistry and theoretical analyses reveal that CoTe_2-x exhibits higher catalytic activity in long-chain polysulfide transformation and Li₂S decomposition, while monodispersed Co sites are more effective in boosting sulfur reduction kinetics to regulate Li₂S deposition. Such cascade catalysis endows Co_SA-CoTe_2-x@NHCF with the all-around service of "trapping-conversion-recuperation" for sulfur species during the whole redox reaction. Furthermore, it is demonstrated by in situ transmission electron microscopy that initially formed electronic-conductive Co and ionic-conductive Li₂Te provide sufficient lithiophilic sites to regulate homogeneous Li plating and stripping with markedly suppressed dendrite growth. Consequently, by coupling the Co_SA-CoTe_2-x@NHCF interlayer and Li@Co_SA-CoTe_2-x@NHCF anode, the constructed Li-S full batteries deliver superior cycling stability and rate performance, and the flexible pouch cell exhibits stable cycling performance at 0.3 C. The gained insights into the synergistic effect of asymmetric-size structures pave the way for the integrated catalyst design in advanced Li-S systems.