Selenium-doped high-entropy MXene@CNTs with abundant vacancies as bifunctional electrocatalysts for boosting redox kinetics in lithium–sulfur batteries

Se-doped high-entropy MXene@CNT with abundant oxygen vacancies is fabricated as bifunctional electrocatalyst. • The composite accelerates polysulfide redox and suppresses Li dendrites via optimized electronic and 3D conductive structure. • Cells achieve ultra-stable long cycling, high sulfur loading performance and a 2.0 Ah pouch cell. Lithium–sulfur batteries (LSBs) hold exceptional promise for high-energy-density energy storage, yet their practical deployment is severely hindered by sluggish sulfur redox kinetics, polysulfide shuttling, and uncontrolled lithium dendrite growth. High-entropy MXene exhibits unique compositional diversity and synergistic electronic effects, but their catalytic activity remain insufficient for robust polysulfide regulation. Herein, we develop a selenium-doped high-entropy MXene@CNT (Se-HE-MX@C) bifunctional electrocatalyst with Se-induced vacancy defects to synergistically regulate cathode and anode redox reactions. Se-doping generates abundant cation vacancies and optimizes the electronic structure, strengthening polysulfide chemisorption and lowering the energy barrier for polysulfide conversion. The CNT interwoven network constructs a continuous 3D conductive pathway, accelerating electron/ion diffusion and mitigating structural degradation. Electrochemical and in-situ characterizations reveal that Se-HE-MX@C significantly promotes Li 2 S nucleation/decomposition, enhances Li + diffusion kinetics, and induces uniform lithium deposition. As a result, the LSB with Se-HE-MX@C-modified separator exhibits excellent rate performance and ultralong cycling stability (a low-capacity decay rates of merely 0.047% per cycle after 700 cycles at 1.0C). Moreover, The Se-HE-MX@C-based pouch cell delivers an ultra-high capacity of ∼2.0 Ah. This work elucidates the structure–activity relationship between defect engineering, high-entropy regulation, and bifunctional electrocatalysis, offering a rational design principle for advanced electrocatalysts in high-performance LSBs. Download: Download high-res image (273KB) Download: Download full-size image