Exfoliated 2D Lepidocrocite Titanium Oxide Nanosheets for High Sulfur Content Cathodes with Highly Stable Li-S Battery Performance

Despite the high energy densities, lithium-sulfur (Li-S) batteries suffer from insufficient cycle life originating from the shuttling process involving lithium polysulfides (LiPSs). Various approaches have been introduced to resolve the shuttling problem, but they are not usually effective for electrodes with high sulfur contents. Here, we report an exfoliated 2D lepidocrocite titanium oxide nanosheet as a component for sulfur cathodes to suppress polysulfide dissolution markedly. In particular, the Lewis acidity originating from undercoordinated Ti species as well as the large surface area associated with the 2D structure endow 2D lepidocrocite titanium oxide with an efficient interaction with LiPSs. As a result, even with a sulfur content of 80 wt %, the Li-S cell exhibits 1023.5 mAh g^-1 at 50 mA g^-1 and a capacity retention of 82.3% after 300 cycles measured at 1000 mA g^-1. The considerably improved cycling performance provides useful insight for designing sulfur cathodes, that is, the incorporation of acidic 2D metal oxide nanosheets.