In Situ Polymerization of Nanostructured Conductive Polymer on 3D Sulfur/Carbon Nanofiber Composite Network as Cathode for High‐Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li‐S) batteries have been considered as a promising next‐generation energy storage system. However, practical application of Li‐S batteries is hindered by the nonconductive nature of sulfur (S) and continuous capacity fading during cycling. Here, a simple but effective strategy is proposed to fabricate high‐performance Li‐S batteries by in situ polymerization of polyaniline (PANi)/S/carbon nanofiber (CNF) cathode. Compared to traditional carbon black/S cathodes and other cathode materials with PANi polymer, this effective three‐dimensional (3D) cathode design has several advantages: (i) the interconnected and highly conductive CNF/PANi network structure facilitates the electron transfer between the insulating S and conductive CNF mat; (ii) the CNF/PANi network structure, with abundant oxygen and nitrogen heteroatoms, offers strong adsorption for the polysulfides; (iii) the 3D architecture of CNF/S/PANi helps accommodate the volume change of S during cycling and maintain the structural integrity of the cathode; (iv) the easy and simple fabrication process minimizes the time and energy costs; and (v) the freestanding composite cathode without additional polymer binder contributes to higher energy density of Li‐S batteries. With all the advantages mentioned above, Li‐S cells present a high S utilization with stable cycling performance for over 300 cycles with a low capacity decay rate of 0.08% cycle −1 .