Engineering a high-entropy oxide with high-density grain boundaries and strong d–p orbital coupling for advanced lithium–sulfur batteries

Abstract

Catalytic conversion of lithium polysulfides (LiPSs) has been proven to be an effective strategy to facilitate the sulfur conversion kinetics and prevent the shuttle effect in lithium–sulfur (Li–S) batteries. However, the search for highly active sulfur electrocatalysts remains a great challenge. In this work, we report the rational design and synthesis of a novel flower-like high-entropy oxide (HEO) electrocatalyst composed of Bi, Sb, W, V and Mo cations for Li–S batteries. In particular, the high-density grain boundaries alongside the crystalline–amorphous heterophase structure provide abundant catalytic active centers for sulfur redox reactions. In addition, the strong d–p orbital coupling effect between 3d/4d/5d metals and p-block metals modulates the electronic interaction, strengthens the chemical absorption and enhances the catalytic activity toward LiPSs. Benefiting from these unique features, the HEO BiSbWVMoO electrocatalyst not only efficiently facilitates the conversion of LiPSs but also greatly accelerates the Li₂S decomposition, thereby achieving the bidirectional sulfur conversion. As a result, Li–S batteries paired with the HEO BiSbWVMoO-modified separators exhibit extraordinary performance, including a high discharge capacity of 1440.4 mA h g⁻¹ at 0.1C, a remarkable rate capability of 607.9 mA h g⁻¹ at 5C and a prolonged lifespan of over 1000 cycles at 1C with a low capacity decay of 0.053% per cycle. More significantly, the HEO BiSbWVMoO battery delivers a high initial areal capacity of 5.1 mA h cm⁻² at 0.2C under a high sulfur loading of 4.9 mg cm⁻². Overall, the present work offers a new perspective for the rational design of high-entropy electrocatalysts for advanced Li–S batteries.