Manganese Oxide Nanosheets with Mixed Valence States as a Separator Coating for Lithium–Sulfur Batteries

Abstract

The shuttling effect of soluble polysulfides and the inadequate conductivity of sulfur and lithium sulfide impede the practical utilization of lithium–sulfur batteries. To address this issue, the polar δ-MnO2 nanosheets with a 2D morphology can provide abundant anchor and catalytic sites for polysulfides. However, the poor intrinsic conductivity restricts the transformation ability. Herein, we introduce mixed Mn4+/Mn3+ valence states in δ-MnO2 nanosheets by a facile annealing method to promote the redox kinetics of polysulfides. This treated MnO2 maintains its 2D morphology, providing abundant absorption sites for polysulfides, while the introduction of mixed valence states enhances charge transfer and facilitates reaction kinetics. As a result, the lithium–sulfur battery achieves high areal capacities of 7.0 mAh cm–2 at 0.56 mA cm–2 and 4.0 mAh cm–2 at 1 mA cm–2 after 100 cycles with a sulfur loading of 10.91 mg cm–2 and an E/S ratio of 6.46 μL mg–1.