Propelling polysulfide redox conversion by d-band modulation for high sulfur loading and low temperature lithium-sulfur batteries

The sluggish redox conversion of sulfur species, especially under high sulfur loading, low-temperature, and low electrolyte/sulfur (E/S) ratio conditions, aggravates the shuttle effect that severely deteriorates the electrochemical performance of Li-S batteries. Herein, alloying metallic Ni with Fe increases the Ni-Ni(Fe) bond length and reduces the coordination number of Ni, realizing the upshift of the d-band center towards the Fermi level, and thus regulates sulfur species adsorbability to a rational level to accelerate their catalytic conversion. As a consequence, the Li-S batteries with Ni 3 Fe-modified separators exhibit superior rate performances (800 and 645 mA h g −1 at 10 and 15C, respectively) and excellent cycling stability (capacity decay of 0.05% per cycle over 800 cycles at 2.0C). Meanwhile, the stable operation of high areal capacity Li-S batteries under a high sulfur loading of 30 mg cm −2 and a low electrolyte/sulfur ratio of ∼7 µL mg −1 is realized. Besides, benefitting from the enhanced kinetics, the battery can work well at −10 °C, which is rarely achieved by conventional Li-S batteries. Our work provides a promising strategy for designing high-activity electrocatalysts for high-performance and low-temperature Li-S batteries. Alloying metallic Ni with Fe realizes the upshift of d-band center towards Fermi level, and thus regulates polysulfide adsorbability to accelerate their catalytic conversion.