Lightweight Free-Standing 3D Nitrogen-Doped Graphene/TiN Aerogels with Ultrahigh Sulfur Loading for High Energy Density Li–S Batteries

Lithium–sulfur (Li–S) batteries have attracted extensive attention due to their high theoretical specific capacity and high energy density. However, the sulfur loading and sulfur content are low in most of the reported Li–S batteries, resulting in a low practical energy density. Herein, binder- and metal-current-collector-free lightweight electrodes based on a free-standing three dimensional (3D) nitrogen-doped graphene/TiN composite aerogel (3DNG–TiN) are designed and prepared to assemble high energy density Li–S batteries. The 3D network structure in the aerogel provides excellent charge transport channels and large micro- and submicron pores to ensure an ultrahigh sulfur loading. Notably, the polar TiN nanoparticle component in the composite effectively suppresses the shuttling effect and accelerates the reaction kinetics of polysulfides, which significantly enhances the cycling and rate performance of resulting Li–S batteries. Additionally, the lightweight free-standing 3DNG–TiN electrode (3.54 mg/cm2) boosts the absolute sulfur content in the cathode up to 85.0 wt %. Li–S batteries with a high sulfur loading (20.0 mg/cm2) exhibit high initial areal capacities of 18.9 mA h/cm2 and 16.2 mA h/cm2 after 100 cycles at 2.0 mA/cm2. This work provides a new strategy to achieve a high energy density of Li–S batteries.