Root-like porous carbon nanofibers with high sulfur loading enabling superior areal capacity of lithium sulfur batteries

Abstract

A hierarchically porous carbon nanofiber (HPCNF) material was prepared by a facile electrospinning method, with polyvinylpyrrolidone (PVP) as the carbon source and silica formed in-situ as the template. The carbon nanofibers showed a well-designed pore structure: centered macropores are surrounded by a denser cycle consisting of micro-/mesopores near the surface. Sulfur was encapsulated into the pores by solution penetration, followed by a melt diffusion method to generate a flexible sulfur/HPCNF (S/HPCNF) cloth as the binder-free cathode in lithium sulfur (Li-S) batteries. The HPCNF carbon with multi-scaled pores acts as an efficient host for large amounts of sulfur, and accommodates the associated volume expansion during electrochemical cycling. Moreover, the hierarchical architecture significantly reduces the escape of polysulfides during the cycling. The unique material allowed sulfur loading of 2.2 -12.1 mg cm(-2), and exhibited a high sulfur utilization of more than 80% with high areal capacity of 11.3 mAh cm(-2), demonstrating that S/HPCNF is a promising cathode material for Li-S batteries of high energy density. (C) 2017 Elsevier Ltd. All rights reserved.