Manganese Oxide Nanosheets\nwith Mixed Valence States\nas a Separator Coating for Lithium–Sulfur Batteries

Abstract

The shuttling effect of soluble polysulfides and the\ninadequate\nconductivity of sulfur and lithium sulfide impede the practical utilization\nof lithium–sulfur batteries. To address this issue, the polar\nδ-MnO₂ nanosheets with a 2D morphology can provide\nabundant anchor and catalytic sites for polysulfides. However, the\npoor intrinsic conductivity restricts the transformation ability.\nHerein, we introduce mixed Mn⁴⁺/Mn³⁺ valence\nstates in δ-MnO₂ nanosheets by a facile annealing\nmethod to promote the redox kinetics of polysulfides. This treated\nMnO₂ maintains its 2D morphology, providing abundant absorption\nsites for polysulfides, while the introduction of mixed valence states\nenhances charge transfer and facilitates reaction kinetics. As a result,\nthe lithium–sulfur battery achieves high areal capacities of\n7.0 mAh cm^–2 at 0.56 mA cm^–2 and\n4.0 mAh cm^–2 at 1 mA cm^–2 after\n100 cycles with a sulfur loading of 10.91 mg cm^–2 and an E/S ratio of 6.46 μL mg^–1.