Shuttle-inhibited 3D sandwich MXene/SnO2QDs sulfur host for high-performance lithium-sulfur batteries

Abstract

Herein, sandwich-like Ti3C2Tx MXene/SnO2 quantum dots composites were synthesized as sulfur host, aiming to alleviate the shuttle effect of polysulfides present in lithium-sulfur batteries. SnO2 quantum dots (SnO2QDs) were introduced into the interlayer of MXene through a simple electrostatic self-assembly method, and the mass fraction of SnO2QDs was controlled to construct sandwich MXene/SnO2QDs. While SnO2QDs effectively alleviating the stacking tendency of MXene, Ti and Sn co-chemisorb polysulfides and the interlayer structure physically confines polysulfides. Significantly, the synergistic effect between MXene with SnO2QDs effectively alleviates the shuttle effect of polysulfides and buffers the volume expansion. Meanwhile, with the help of the catalysis of SnO2QDs, the liquid-solid reaction kinetics of lithium polysulfides converting to Li2S2/Li2S is accelerated. Electrochemical test results showed that the MXene/SnO2QDs/S cathode has a high initial discharge specific capacity (1147.6 mAh g−1 at 0.1 C, while MXene/S is only 615.4 mAh g−1), as well as excellent rate performance and cycling stability in Li-S batteries.