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 as an effective strategy to facilitate the sulfur conversion kinetics and prevent the shuttle effect for lithium-sulfur (Li-S) batteries. However, searching for highly active sulfur electrocatalysts still remains a grand 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. Specially, the high-density grain boundaries alongside 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 is conductive to modulating the electronic interaction, strengthen the chemical absorption and enhance the catalytic activity toward LiPSs. Benefiting from these unique features, the HEO BiSbWVMoO electrocatalyst not only efficiently facilitate the conversion of LiPSs but also greatly accelerate the Li2S decomposition, thereby achieving the bidirectional sulfur conversion. As a consequent, Li-S batteries paired with the HEO BiSbWVMoO modified separators exhibit extraordinary performance including high discharge capacity (1440.4 mAh g−1 at 0.1 C), remarkable rate capabiility (607.9 mAh g−1 at 5 C) and a prolonged lifespan of over 1000 cycles at 1 C 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 mAh cm−2 at 0.2 C 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.