Rationally designing S/Ti3C2Tx as a cathode material with an interlayer for high-rate and long-cycle lithium–sulfur batteries

Abstract

Lithium–sulfur batteries suffer from poor cycling stability and inferior rate capability, mainly caused by low conductivity and lithium polysulfide dissolution. To tackle these problems, this work demonstrates that Ti₃C₂T_x “clay”, synthesized by selectively extracting the Al layers from the Ti₃AlC₂ phases with a mixture of HCl and LiF, is an effective host material for sulfur cathodes. To further enhance the rate performance and cycling stability of S/Ti₃C₂T_x composites, a single-walled carbon nanotube thin film was prepared by a simple vacuum filtration method and inserted between the cathode and the separator as an interlayer for Li–S batteries. The S/Ti₃C₂T_x composite with an interlayer could deliver a high initial discharge capacity of 1458 mA h g⁻¹ at a current density of 0.1 A g⁻¹ and an ultralow capacity decay of 0.04% per cycle at 0.8 A g⁻¹ for over 1500 cycles was achieved. More importantly, a reversible capacity of 608 mA h g⁻¹ was obtained at a high current density of 8.2 A g⁻¹ (≈5C), demonstrating superior rate capability. These results suggest that the S/Ti₃C₂T_x composite is a promising sulfur cathode material and the introduction of the interlayer will pave the way for the future development and design of high-rate with long-cycle Li–S batteries.