Free-Standing Titanium Nitride Films as Carbon-Free Sulfur Hosts for Flexible Lithium–Sulfur Batteries

Abstract

To achieve the commercialization of lithium–sulfur (Li–S) batteries, there is a big challenge to improve the sulfur content and sulfur loading of sulfur cathodes. Although carbonaceous materials can improve the sulfur content and sulfur loading, the addition of binders and conductive agents limits the increase in energy density to a great extent. Here, carbon-free titanium nitride nanobelt (TiN-NB) thin films with flexible, conductive, hierarchically porous, and free-standing structures have been successfully developed to construct high-sulfur-loading and high-energy-density sulfur electrodes. In addition, macroscopically intertwined 3D nanobelt networks can provide an effective transport path for lithium ions and electrons, and a microscopically high specific surface area and porosity provide a necessary guarantee for the adsorption and catalytic transformation of polysulfides. At a sulfur loading of 1.0 mg cm–2, the TiN-900@S electrode delivers an initial capacity of 1436.7 mAh g–1. After 150 cycles, the reversible capacity still remains at 1032.6 mAh g–1 at 0.5C. Precisely, at a high sulfur loading of 7.1 mg cm–2, the discharge capacity of the TiN-900@S electrode is maintained at 403.1 mAh g–1 after 50 cycles at 0.1C.