Nitrogen and sulfur co-doped hierarchical porous carbon as functional sulfur host for lithium-sulfur batteries

Abstract

Nitrogen and sulfur co-doped hierarchical porous carbon (N,S-HPC) is synthesized by using polyaniline and poly(3,4-ethylenedioxythiophene) as doping sources and polytetrafluoroethylene as the silica template removal agent for lithium-sulfur batteries. N,S-HPC shows the interconnected hierarchical porous network, which enables sulfur to be uniformly dispersed in the carbon matrix thus accelerating the transport of electrons and lithium ions. The S@N,S-HPC composite cathode exhibits a high capacity utilization of 1106 mA h/g at 0.2 C, together with excellent rate capacity of 600 mA h/g at 2 C, and also superior cycle life over 500 cycles with a capacity decay of 0.08 % per cycle at 1 C. The outstanding electrochemical performances for S@N,S-HPC cathode are mainly ascribed to the hierarchical porous structure of carbon and N/S co-doping, which offers sufficient interface for the deposition of solid discharge products and impedes the diffusion of polysulfides due to both physical confinement and chemical interaction by porous carbon matrix and N/S atoms.