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.

Since lithium sulfur (Li-S) energy storage devices are anticipated to power portable gadgets and electric vehicles owing to their high energy density (2600 Wh·kg^–1); nevertheless, their usefulness is constrained by sluggish sulfur reaction kinetics and soluble lithium polysulfide (LPS) shuttling effects. High electrically conductive bifunctional electrocatalysts are urgently needed for Li-S batteries, and high-entropy oxide (HEO) is one of the most promising electrocatalysts. In this work, we synthesize titanium-containing high entropy oxide (Ti-HEO) (TiFeNiCoMg)O with enhanced electrical conductivity through calcining metal-organic frameworks (MOF) templates at modest temperatures. The resulting single-phase Ti-HEO with high conductivity could facilitate chemical immobilization and rapid bidirectional conversion of LPS. As a result, the Ti-HEO/S/KB cathode (with 70 wt.% of sulfur) achieves an initial discharge capacity as high as ~1375 mAh·g^–1 at 0.1 C, and a low-capacity fade rate of 0.056% per cycle over 1000 cycles at 0.5 C. With increased sulfur loading (~5.0 mg·cm^–2), the typical Li-S cell delivered a high initial discharge capacity of ~607 mAh·g^–1 at 0.2 C and showcased good cycling stability. This work provides better insight into the synthesis of catalytic Ti-containing HEOs with enhanced electrical conductivity, which are effective in simultaneously enhancing the LPS-conversion kinetics and reducing the LPS shuttling effect.