Bifunctional Separator with Ultra-Lightweight MnO 2 Coating for Highly Stable Lithium-Sulfur Batteries.

The severe shuttling behavior in the discharging-charging process largely hampers the commercialization of lithium-sulfur (Li-S) batteries. Herein, we design a bifunctional separator with an ultra-lightweight MnO 2 coating to establish strong chemical adsorption barriers for shuttling effect alleviation. The double-sided polar MnO 2 layers not only trap the lithium polysulfides through extraordinary chemical bonding but also ensure the uniform Li + flux on the lithium anode and inhibit the side reaction, resulting in homogeneous plating and stripping to avoid corrosion of the Li anode. Consequently, the assembled Li-S battery with the MnO 2 -modified separator retains a capacity of 665 mA h g -1 at 1 C after 1000 cycles at the areal sulfur loading of 2.5 mg cm -2 , corresponding to only 0.028% capacity decay per cycle. Notably, the areal loading of ultra-lightweight MnO 2 coating is as low as 0.007 mg cm -2 , facilitating the achievement of a high energy density of Li-S batteries. This work reveals that the polar metal oxide-modified separator can effectively inhibit the shuttle effect and protect the Li anode for high-performance Li-S batteries.