Activating NiO via Fe doping for ultrafast polysulfide conversion in Li-S batteries

Benefiting from the low cost and natural abundance of sulfur, as well as its excellent theoretical performance metrics - including a capacity of 1675 mAh g −1 and an energy density of 2600 Wh kg −1 - lithium-sulfur (Li-S) batteries have attracted considerable attention for next-generation energy storage. However, their practical deployment is severely hindered by the intrinsic shuttle effect of lithium polysulfides (LiPSs), which leads to the loss of active materials and poor cycling stability. In this work, we report a facile hydrothermal-calcination strategy to synthesize porous nanosheet-structured Fe-doped nickel oxide (Fe-NiO) as a functional separator modifier for Li-S batteries. The polar nature of NiO enables strong chemical interactions with LiPSs, effectively anchoring polysulfides on the cathode side and suppressing the shuttle effect. Furthermore, Fe doping significantly increases the density of surface active sites, thereby enhancing the adsorption and catalytic conversion of LiPSs into insoluble Li 2 S 2 /Li 2 S species, which promotes redox kinetics and mitigates capacity fading. When applied to Li-S cells, the Fe-NiO-modified separator markedly improves the electrochemical performance, delivering a high reversible capacity of 1150 mAh g −1 at 0.2C, an excellent rate capability of 505 mAh g −1 at 5C, and outstanding long-term stability with a minimal capacity decay of 0.091 % per cycle over 500 cycles at 1C. This study presents a simple and scalable strategy for separator engineering, providing a promising pathway toward high-performance Li-S batteries.