High Entropy Oxide (CrMnFeNiMg)3O4 with Large Compositional Space Shows Long‐Term Stability as Cathode in Lithium‐Sulfur Batteries

Abstract The repeated formation and irreversible diffusion of liquid‐state lithium polysulfides (LiPSs) are the primary challenges in the development of high‐energy‐density lithium‐sulfur battery (LSB). An effective strategy to alleviate the resulting polysulfide loss is critical for the stability of LSBs. In this regard, high entropy oxides (HEOs) appear as a promising additive for the adsorption and conversion of LiPSs owing to the diverse active sites, offering unparalleled synergistic effects. Herein, we have developed a (CrMnFeNiMg) 3 O 4 HEO as a functional polysulfide trapper in LSB cathode. The adsorption of LiPSs by the metal species (i. e., Cr, Mn, Fe, Ni, and Mg) in the HEO takes place through two different paths and leads to enhanced electrochemical stability. We demonstrate that the optimal sulfur cathode with the (CrMnFeNiMg) 3 O 4 HEO attains a high peak and reversible discharge capacities of 857 mAh g −1 and 552 mAh g −1 , respectively, at a cycling rate of C/10, a long cycle life of 300 cycles, and a high rate performance at the cycling rates from C/10 to C/2.