High-Energy-Density, Long-Life Lithium-Sulfur Batteries with Practically Necessary Parameters Enabled by Low-Cost Fe-Ni Nanoalloy Catalysts.

Lithium-sulfur (Li-S) batteries possess high theoretical specific energy but suffer from lithium polysulfide (LiPS) shuttling and sluggish reaction kinetics. Catalysts in Li-S batteries are deemed as a cornerstone for improving the sluggish kinetics and simultaneously mitigating the LiPS shuttling. Herein, a cost-effective hexagonal close-packed (hcp)-phase Fe-Ni alloy is shown to serve as an efficient electrocatalyst to promote the LiPS conversion reaction in Li-S batteries. Importantly, the electrocatalysis mechanisms of Fe-Ni toward LiPS conversion is thoroughly revealed by coupling electrochemical results and post mortem transmission electron microscopy, X-ray photoelectron spectroscopy, and in situ X-ray diffraction characterization. Benefiting from the good catalytic property, the Fe-Ni alloy enables a long lifespan (over 800 cycles) and high areal capacity (6.1 mA h cm-2) Li-S batteries under lean electrolyte conditions with a high sulfur loading of 6.4 mg cm-2. Impressively, pouch cells fabricated with the Fe-Ni/S cathodes achieve stable cycling performance under practically necessary conditions with a low electrolyte/sulfur (E/S) ratio of 4.5 μL mg-1. This work is expected to design highly efficient, cost-effective electrocatalysts for high-performance Li-S batteries.