(De)Lithiation of tubular polypyrrole-derived carbon/sulfur composite in lithium-sulfur batteries

Non-graphitizable carbon (NGC) has been obtained by carbonizing tubular polypyrrole (T-PPy) synthesized through a self-degraded template method . K-NGC/S composite has been prepared by mixing S with K-NGC via melt-diffusion method where NGC has been activated by potassium hydroxide (denoted as K-NGC) and is used as a conductive additive. The as-prepared K-NGC/S composite shows good specific discharge capacity and rate capability with an initial specific discharge capacity of 1121.9   mAh   g −   1 and a specific discharge capacity of 729.7   mAh   g −   1 after 50   cycles at a current density of 335   mA   g −   1 , which is better than pure S. This improvement in the specific discharge capacity and the rate capability of the cell with K-NGC/S composite as a cathode material is realized by the existence of K-NGC, which can offers a superb conductive environment for S, effectively encapsulate S, restrain the outward diffusion of polysulfides , buffer volume change upon cycling and reduce the dissolution of lithium polysulfides into the electrolyte. The good electrochemical performance of K-NGC/S composite would make it become a promising cathode material for lithium-sulfur batteries.