Functionalized N-doped hollow carbon spheres as sulfur host with enhanced electrochemical performances of lithium-sulfur batteries

Abstract

A novel composite, functionalized N-doped hollow carbon spheres (F-NHCS), is proposed as cathode host for improving the cycle stability and rate capability of a Li-S battery, which involves the functionalization of NHCS with oxygen-containing groups. The high electronic conductivity and abundant oxygen-containing functional groups of F-NHCS can not only be served as the conductive matrix for loading S as the cathode (F-NHCS-S) but also exhibit strong absorption capability to anchor S atoms and thus effectively solve the dissolution issue of intermediates polysulfides during cycling. As a result, the as-obtained F-NHCS-S cathode exhibits excellent performances: delivering an initial specific capacity of 827 mAh g−1 at 0.2 C with about 74 wt% S loading and retaining a specific capacity of 549 mAh g−1 after 100 cycles, compared to the respective 747 mAh g−1 and 182 mAh g−1 of the cathode based on the host without N-doping and functionalization (HCS-S). The fabrications of the hosts and the corresponding cathodes are demonstrated by the physical characterizations from SEM, TEM, XPS, XRD, FT-IR, BET, and TGA.