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

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 Ti3C2Tx foam, as a novel sulfur host, was synthesized via direct stacking of Ti3C2Tx flakes into film followed by hydrazine-induced foaming. This Ti3C2Tx 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 Ti3C2Tx 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 Ti3C2Tx foam/S cathode opens new delightful opportunities for constructing practical high-energy-density Li-S batteries.