High performance room temperature Na-S batteries based on FCNT modified Co3C-Co nanocubes

Abstract

High-temperature Sodium-sulfur (Na-S) batteries have been commercial owing to their high energy density. However, their extra safety and cost issues caused by high-temperature inhibits their wide application. Recently, room-temperature Na-S batteries have attracted widespread attention due to the low cost and excellent energy density. Nevertheless, they still suffer from the poor conductivity, sluggish redox kinetics and shuttle effect. Herein, the incorporated polar Co3C-Co with open fluorinated carbon nanotubes arrays encapsulated in porous three-dimensional (3D) framework (FCNT@Co3C-Co) was designed and applied as the sulfur host for Na-S battery. Theoretical and experimental results indicate that the polar and porous FCNT@Co3C-Co possesses the strong interactions with Na+ and S intermediate species (NaPSs), which increases the sulfide utilization and suppresses the shuttle effect by the efficient physisorption/chemisorption and rapid electrocatalytic conversion. Moreover, the synergy of the porous cube-like framework and superior interface property in FCNT@Co3C-Co mitigates the huge volume variations and reduces the energy barrier for Na-S battery. Hence, the FCNT@Co3C-Co based Na-S batteries deliver a high discharge capacity of 1364 mAh g−1 at 0.1 C even with a lean E/S of 5 mL g−1 under a high S loading of 3.2 mg cm−2 and show Coulombic efficiency above 75% after 500 loops under 2 C at room-temperature.