Highly Conductive and Lightweight Composite Film as Polysulfide Reservoir for High‐Performance Lithium–Sulfur Batteries

Abstract Lithium–sulfur (Li−S) batteries are one of the most promising candidates for the next generation of energy‐storage devices owing to their high theoretical energy and low cost. However, low practical energy density and poor cycling life are obstacles to the practical application of Li−S batteries. A highly conductive and lightweight poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate–carbon nanotube (PEDOT:PSS‐CNT) interlayer for Li−S batteries has been fabricated. The PEDOT:PSS‐CNT interlayer not only acts as a soft buffer to scavenge excess lithium polysulfides in the pores and restricts polysulfides from migrating to the lithium anode by chemical absorption, but also serves as an assisted “current collector” to improve the electronic conductivity for the sulfur cathode. With these synergistic contributions, pure sulfur cathode with the PEDOT:PSS‐CNT interlayer shows a high capacity (921 mA h g −1 at 0.5 C ; 1 C =1675 mA h g −1 ), enhanced cycling performance (a capacity retention of 70.9 % after 200 cycles), and good rate performance. The excellent electrochemical performance of the sulfur cathode plus the easy fabrication of such a functional interlayer bring feasible Li−S batteries for practical applications one step closer.