Single-Atom Coated Separator for Robust Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are strong contenders among lithium batteries due to superior capacity and energy density, but the polysulfide shuttling effect limits cycle life, and reduces energy efficiency due to a voltage gap between charge and discharge. Here, we demonstrate that graphene foam impregnated with single atom catalysts (SACs) can be coated on commercial PP separator to catalyze polysulfide conversion, leading to a reduced voltage gap and much improved cycle life. Also, among Fe/Co/Ni SACs, Fe SACs may be a better option to be used in Li-S systems. By deploying SACs in battery separator, cycle stability improves hugely especially considering relatively high sulfur loading and ultra-low SACs contents. Even at a metal loading of ~ 2 μg in the whole cell, Fe SAC-modified separator delivers superior Li-S battery performance even at high sulfur loading (891.6 mAh g-1, 83.7% retention after 750 cycles at 0.5 C). Our work further enrich and expand the application of SACs catalyzing polysulfide blocking and conversion and improving round trip efficiencies in batteries, without side effects such as electrolyte and electrode decomposition.