Vanadium niobium carbide (VNbCT) bimetallic MXene derived VS-NbO@MXene heterostructures for efficiently boosting the adsorption and catalytic performance of lithium polysulfide.

To alleviate the shuttle effect in lithium-sulfur (Li-S) batteries, the electrocatalytic conversion of polysulfides serves as a vital strategy. However, achieving a synergy that combines robust adsorption with high catalytic activity continues to pose significant challenges. Herein, a simple solid-state sintering method is employed to transform vanadium-niobium carbide MXene (VNbCT) into a heterogeneous structure of VS-NbO@VNbCT MXene (denoted as VS-NbO@MX). The NbO component immobilizes lithium polysulfides (LiPSs) at the electrode through its strong chemical affinity, while the VS fraction serves as an outstanding electrochemical catalyst, enhancing the reaction kinetics of sulfur precipitation. Furthermore, the VNbCT MXene precursor scaffold is preserved through the conversion and uniformly distributed throughout the composite, exhibiting excellent electrical conductivity. Thanks to the synergistic "capture-adsorption-catalysis" action on LiPSs, the VS-NbO@MX composite effectively restrains the shuttle effect. The as-prepared Li-S battery demonstrates a significant increase in specific capacity, reaching 1508 mA h g at 0.1C and maintaining a capacity decay of approximately 0.027% per cycle after 500 cycles at 1C and 766.1 mA h g at 5C. Even under a high sulfur loading of 5.75 mg cm, the battery can maintain a specific capacity of 596.6 mA h g and exhibit significant cycling stability after 100 cycles. DFT calculations indicate that the VS-NbO@MX heterostructure exhibits a higher binding energy of 5.34 eV and a lower decomposition barrier energy of 0.68 eV, presenting potential advantages in accelerating the conversion reactions of LiPSs. Our research offers a straightforward approach for designing metal oxide-sulfide heterostructured catalysts that deliver superior performance and enhance the electrocatalytic conversion of LiPSs, clearing the path for high performance Li-S batteries.