Ti₃C₂ QDs@CNTs with Active Titanium Species as Bidirectional Catalytic Cathode for Facilitating Lithium Polysulfide Conversion in Li–S Batteries

Abstract The slow redox kinetics and severe shuttle effect caused by the diffusion of lithium polysulfides (LiPSs) severely hinder the practical application of lithium–sulfur (Li–S) batteries. The construction and utilization of catalytic electrode materials are promising strategies to effectively suppress shuttle effect and accelerate redox kinetics of sulfur species. This work reports a simple hydrothermal‐ultrasonic combined method to construct conductive titanium carbide quantum dots (Ti₃C₂ QDs) supported on carbon nanotubes (CNTs) (Ti₃C₂ QDs@CNTs composites) as efficient electrocatalysts for Li–S batteries. Based on the analysis of dynamic evolutions of Ti₃C₂ QDs catalysts and sulfur species, Ti³⁺ and Ti⁴⁺ species can be identified as active species that accelerate Li₂S nucleation and dissociation. Due to the abundant catalytic active sites from Ti₃C₂ QDs, Ti₃C₂ QDs@CNTs effectively catalyze the conversion of LiPSs. Moreover, the conductive CNTs matrix and Ti₃C₂ QDs significantly enhance charge transport, allowing for rapid Li⁺/electron transfer. As a result, Ti₃C₂ QDs@CNTs/S electrode exhibits high initial capacity, good rate capability, and improved long‐term cyclability. This work provides a promising strategy to introduce QDs into the cathode of Li–S battery to achieve better electrochemical performance.