High-Entropy Spinel Oxide Nanofibers as Catalytic Sulfur Hosts Promise the High Gravimetric and Volumetric Capacities for Lithium-Sulfur Batteries

The exploration of new catalytic hosts is highly important to tackle the sluggish electrochemical kinetics of sulfur redox for achieving high energy density of lithium-sulfur batteries. Herein, for the first time, we present high-entropy oxide (HEO, (Mg0.2Mn0.2Ni0.2Co0.2Zn0.2)Fe2O4) nanofibers as catalytic host of sulfur. The HEO nanofibers show a synergistic effect among multiple metal cations in spinel structure that enables strong chemical confinement of soluble polysulfides and fast kinetics for polysulfide conversion. Consequently, the S/HEO composite displays the high gravimetric capacity of 1368.7 mAh g(-1) at 0.1 C rate, excellent rate capability with the discharge capacity of 632.1 mAh g(-1) at 5 C rate, and desirable cycle stability. Furthermore, the S/HEO composite shows desirable sulfur utilization and good cycle stability under a harsh operating condition of high sulfur loading (4.6 mg cm(-2)) or low electrolyte/sulfur ratio (5 mu L mg(-1)). More impressively, the high volumetric capacity of 2627.9 mAh cm(-3) is achieved simultaneously for the S/HEO composite due to the high tap density of 1.92 g cm(-3), nearly 2.5 times of the conventional sulfur/carbon composite. Therefore, based on high-entropy oxide materials, this work affords a fresh concept of elevating the gravimetric/volumetric capacities of sulfur cathodes for lithium-sulfur batteries.

Automated summary

The use of high-entropy oxide nanofibers as a catalytic host for sulfur in lithium-sulfur batteries leads to high gravimetric capacities, excellent rate capability, and desirable cycle stability. The composite also demonstrates ideal sulfur utilization and good cycle stability under harsh operating conditions, achieving a high volumetric capacity due to its high tap density.