Manganese-Incorporated Single-Phase High-Entropy Oxide Modified Separator Enabled High Performance of Lithium-Sulfur Batteries at High Sulfur Loading

High-entropy oxides (HEOs) have sparked scientific interest recently as a potential material technology for lithium-sulfur (Li–S) batteries. This interest stems from their simultaneous roles as sulfur hosts and electrocatalysts, which provide enhancements to the performance of sulfur cathode composites. Nonetheless, their incorporation into the active material blend results in compromised energy density, particularly when their gravimetric proportion is substantial (≥10 wt.%, in the sulfur-based cathode). In this study, a manganese (Mn)-containing HEO (S_config ≥ 1.5R) was synthesized and subsequently coated onto a commercial Celgard separator at a low areal loading (~0.23 mg cm⁻²) with the aim of decreasing HEO content in the cathode composite material while still boosting lithium polysulfide (LPS) conversion kinetics. Li–S batteries incorporating this modified separator-high entropy oxide (MS-HEO) demonstrate exceptional electrochemical performance, achieving a high initial discharge capacity of ~1642 mAh g⁻¹ at 0.1 C and a remarkably low-capacity fade rate of 0.055% per cycle over 450 cycles at 1 C. Remarkably, the MS-HEO batteries exhibited commendable electrochemical performance at high sulfur loading (~7 mg cm⁻²), delivering an initial discharge capacity of ~819 mAh g⁻¹ during the first discharge and maintaining stable cycling up to 30 cycles at 0.1 C thereafter. Collectively, this work underscores the significance of precise adjustment of HEO compositions through low-temperature MOF calcination strategies and demonstrates their potential to enhance the electrochemical performance of Li–S batteries under the high-sulfur loading conditions necessary for future commercial applications.