High-entropy perovskite oxide nanofibers as efficient bidirectional electrocatalyst of liquid-solid conversion processes in lithium-sulfur batteries

Transition metal oxides are a class of promising host materials of sulfur for lithium-sulfur (Li-S) batteries due to their robust polysulfide adsorption, and catalytic effect on sulfur redox reaction.  It is proven that the adsorption-catalysis property can benefit a lot  from incorporating multiple metal elements, and high-entropy oxides  (HEOs) show good competitive potential for durable Li-S batteries.  Herein, HEO nanofibers  are designed as bidirectional catalytic host of sulfur to promote both  the reduction of soluble intermediates and the re-oxidation of insoluble  products. Specifically, the high-entropy perovskite oxide La_0.8Sr_0.2(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ (HE-LSMO) nanofibers prepared via an electrospinning-calcination method show a unique porous fibrous structure  for incorporation with sulfur. The introduced multiple metal elements  can effectively modulate the binding strength of soluble polysulfides,  and HE-LSMO nanofibers act as bidirectional electrocatalyst for the liquid-solid conversion processes between soluble polysulfides and insoluble Li₂S, which is enabled by the high entropic contribution. As a result, the S/HE-LSMO cathode with a sulfur loading of 8.4 mg cm⁻² shows a high areal capacity of 6.6 mAh cm⁻² at low electrolyte/sulfur ratio of 5.3 μL mg⁻¹,  as well as good cycle stability. This work provides a foundation  understanding of the bidirectional catalytic role of HEOs toward  practical Li-S batteries.