Self-Assembled Close-Packed MnO₂ Nanoparticles Anchored on a Polyethylene Separator for Lithium–Sulfur Batteries

Separator modification has been proved to be an effective approach for overcoming lithium polysulfide (LiPS) shuttling in lithium–sulfur (Li–S) cells. However, the weight and stability of the modified layer also affect the cycling properties and the energy density of Li–S cells. Here, we initially construct an ultrathin and lightweight MnO2 layer (380 nm, 0.014 mg cm–2) on a commercial polyethylene (PE) separator (MnO2@PE) through a chemical self-assembly method. This MnO2 layer is tightly anchored onto the PE substrate because of the presence of oxygen-containing groups that form a relatively strong chemical force between the MnO2 nanoparticles and the PE substrate. In addition, the mechanical strength of the separator is not affected by this modification procedure. Moreover, because of the catalytic effect and compactness of the MnO2 layer, the MnO2@PE separator can greatly suppress LiPS shuttling. As a result, the application of this MnO2@PE separator in Li–S batteries leads to high reversible capacity and superior cycling stability. This strategy provides a novel approach to separator surface modification.