Defectizing high-entropy oxide with the introduction of Se to facilitate the kinetics for highly cycle-stable lithium–sulfur batteries

Abstract

As a novel material, high-entropy compounds have attracted extensive attention in the field of lithium–sulfur battery host materials due to their diverse elemental composition with a wide range of properties. The ability to effectively mitigate the shuttle effect of lithium polysulfides and catalyze the bidirectional conversion of Li₂S₂/Li₂S is crucial to enhance the overall performance of the battery. In this study, a unique sulfur host nanosized high-entropy material comprising selenium-doped HEO (AlCrFeCoNi)₃O_4-x-Se_x is fabricated using an in situ thermal reduction and selenylation method. In the high-entropy compounds, the introduction of Se causes that the generation of oxygen vacancies during the lattice distortion serves as ion transfer pathway and the formation of M-Se bonds provides a high adsorption capability for LiPSs. Moreover, the polymetallic cooperative high-entropy nanoparticles also provide numerous active sites favoring redox kinetics of the sulfur electrode. The resulting selenium-doped HEO (AlCrFeCoNi)₃O_4-x-Se_x not only enhances discharge capacity but also maintains excellent capacity cycling stability. As a result, the HEO-Se/S composite exhibits a specific capacity of 1233.9 mAh g⁻¹ at 0.1C and experiences minimal capacity fading at a rate of 0.038% per cycle over 500 cycles at 0.2C, while host materials with sulfur loading of 4.33 mg cm⁻² and E/S ratio of 5.88 μL mg⁻¹ exhibit excellent capacity retention after 100 cycles at 0.2C. This work offers new insights into synthesizing high-entropy nanomaterials for improving the electrochemical performance of Li–S batteries.

Graphical abstract