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

The lithium-sulfur batteries practical exploitation is hindered by a multitude of obstacles, mainly including the sluggish redox kinetics and soluble lithium polysulfide (LiPS) shuttling through the long-cycles. Here, we construct a continuous three-dimensional conductive carbon nanofiber supported TiO2-MXene heterojunction framework (TM-CNFs) in a one-step electrospinning-carbonization strategy, with the MXene as the “energy band bridge” between carbon substrates and TiO2 to reduce the barrier of the electron transfer. Theoretical simulation and experimental tests proclaim that the TiO2-MXene heterojunction can accelerate the mass transfer process of LiPS at the interface. Meanwhile, the redistribution of electrons in the heterojunction interfaces realizes accelerated the surface electron reversible exchange. Based on the enhanced conductivity, strong chemisorption to LiPS, and remarkable catalysis to sulfur species conversion simultaneously, the Li-S cells with flexible TM-CNFs host demonstrate excellent rate performance and cycle stability (807.3 mAh g-1 at 0.5 C after 200 cycles, and 723.3 mAh g-1 at 1 C after 500 cycles), high areal capacity and energy density (10.85 mAh cm-2 and 1909.86 Wh Kg-1 at high sulfur area loading of 10.5 mg cm-2) and high gravimetric full-cell energy density over 300 Wh Kg-1. The present work affords a new perspective on the electrocatalyst design for the LiPS redox and a feasible strategy to improve the electrochemical performance of practically working lithium-sulfur batteries.