RuO2-Based High-Entropy Oxide and Its Asymmetric Catalysis on Polysulfide Conversion in Lithium–Sulfur Batteries

Abstract

High-entropy oxides with five or more metal components in a single oxide phase, hold attractive potential to enhance the lithium polysulfides adsorption–catalysis ability in Li-S batteries due to the noteworthy synergistic effect of the multiple metal sites. Herein, we have synthesized an RuO₂-based high-entropy oxide, that is, (RuIrFeCoNi)O₂ via a simple molten salt method for Li-S batteries. Our results prove that the introduction of multiple metal components endows high-entropy oxide with moderate adsorption of lithium polysulfides and promising bidirectional catalysis on the liquid–solid conversion between soluble lithium polysulfides and insoluble Li₂S. Particularly, compared with the quaternary (RuFeCoNi)O₂ catalyst, the inferior kinetics enhancement of the lithium polysulfides generation, but the superior promotion of Li₂S deposition for high-entropy oxide greatly favors the inhibition of shuttle effect. Such an asymmetric catalysis behavior induces remarkable electrochemical performance of Li-S batteries assembled with high-entropy oxide-modified separator. High specific capacities of 1641.1 mAh g⁻¹ at 0.1 C and 812.5 mAh g⁻¹ at 2 C are achieved. Remarkably, superior cycle stability is realized with a low capacity decay rate of only 0.060% per cycle within 1000 cycles at 1 C rate. This study unveils the catalytic mechanism of high-entropy oxide in promoting polysulfide conversion and offers a robust foundation for designing efficient catalysts for Li-S batteries.