Self-supporting Ti3C2Tx foam/S cathodes with high sulfur loading for high-energy-density lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries, with high theoretical energy density, cost-effective preparation and environmental benignancy, have been deemed as new encouraging energy storage solutions. However, their development and applications are limited by their low practical energy density and rapid capacity fading. Herein, self-supporting Ti₃C₂T_x foam, as a novel sulfur host, was synthesized via direct stacking of Ti₃C₂T_x flakes into film followed by hydrazine-induced foaming. This Ti₃C₂T_x foam exhibits a well-defined porous structure, increased surface area, enlarged pore volume, and enhanced exposure of Lewis acidic sites, thus effectively strengthening the capability of physical and chemical co-adsorption for polysulfides under a high sulfur loading of 5.1 mg cm⁻². Combined with a favorable electrolyte wettability and extraordinary structural stability, the resultant self-supporting Ti₃C₂T_x foam/S cathodes demonstrated excellent performances: a high initial discharge capacity (1226.4 mA h g⁻¹ at 0.2C), exceptional rate performance (711.0 mA h g⁻¹ at 5C), and extraordinary long-term cycling stability (689.7 mA h g⁻¹ at 1C after 1000 cycles with ultralow capacity decay of ≈0.025% per cycle). Remarkably, the self-supporting structure confers a significantly elevated gravimetric energy density (1297.8 W h kg⁻¹). Therefore, this elaborately designed Ti₃C₂T_x foam/S cathode opens new delightful opportunities for constructing practical high-energy-density Li–S batteries.