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.