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

Abstract

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 1121.9mAhg−1 and a specific discharge capacity of 729.7mAhg−1 after 50cycles at a current density of 335mAg−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.