Cobalt coordination with pyridines in sulfurized polyacrylonitrile cathodes to form conductive pathways and catalytic M-N4S sites for accelerated Li-S kinetics

Sulfurized polyacrylonitrile (SPAN) represents a unique class of cathode material for lithium sulfur (Li-S) batteries as it eradicates the polysulfides shuttling issue in carbonate-based electrolyte. However, due to the essential chemical S-linking and organic nature of SPAN, the active mass percentage and rate capability are two bottleneck issues preventing its ultimate deployment outside of laboratories. In the current work, aiming to endow both the charge conductivity and catalytic activity to SPAN for maximizing the redox kinetics of S conversion, a freestanding nanofibrous SPAN cathode embedding conductive CNTs and atomically dispersed Co centers is fabricated via multivariate electrospinning. While the CNTs enable dramatically enhancing the fiber conductivity and generating mesoscopic porosity for facilitating charge and mass transportation, the cross-linking of SPAN by Co-N4S motifs creates extra charge conduction pathways and further serves as the catalytic active sites for expediting redox S conversion. As a result, an extraordinary Li-SPAN performance is achieved with a high specific capacity up to 1856 mAh g(-1)@0.2 C, a superb rate capability up to 10 C, and an ultra-long battery life up to 1500 cycles@1 C. Consequently, our study here provides insights into the adoption of coordination chemistry to maximize the sulfur utilization by ensuring a more complete redox conversion from SPAN to Li2S, and vice versa. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.