Ti3C2 MXene as an energy band bridge to regulate the heterointerface mass transfer and electron reversible exchange process for Li-S batteries

The practical exploitation of lithium-sulfur batteries is hindered by a multitude of obstacles, including sluggish redox kinetics and the shuttling of soluble lithium polysulfide (LiPS) during long-term cycling. Here, we report the construction of a continuous three-dimensional conductive carbon nanofiber supported TiO2-MXene heterojunction framework (TM-CNFs) via a one-step electrospinning-carbonization strategy, with MXene as the energy band bridge between the carbon substrate and TiO2 to reduce the barrier for electron transfer. Theoretical simulations and experimental tests clearly indicate that the TiO2-MXene heterojunction can accelerate the mass transfer process of LiPS at the interface. Meanwhile, the redistribution of electrons at the heterojunction interfaces accelerates the surface electron reversible exchange. Based on the enhanced conductivity, the strong chemisorption for LiPS, and the remarkable catalysis for the simultaneous conversion of the sulfur species, Li-S cells with a flexible TM-CNFs host demonstrate excellent rate performance and cycling stability (807.3 mA h g(-1) at 0.5C after 200 cycles, and 723.3 mA h g(-1) at 1C after 500 cycles), a high areal capacity and energy density (10.85 mA h cm(-2) and 1909.86 W h kg(-1) at a high sulfur area loading of 10.5 mg cm(-2)), and a high gravimetric full-cell energy density over 300 W h kg(-1). The present work provides a novel perspective on the design of electrocatalysts for LiPS redox and a feasible strategy to improve the electrochemical performance of practical lithium-sulfur batteries.