Oxygen-Deficient Ferric Oxide as an Electrochemical Cathode Catalyst for High-Energy Lithium-Sulfur Batteries

Lithium-sulfur batteries, as one of promising next-generation energy storage devices, hold great potential to meet the demands of electric vehicles and grids due to their high specific energy. However, the sluggish kinetics and the inevitable "shuttle effect" severely limit the practical application of this technology. Recently, design of composite cathode with effective catalysts has been reported as an essential way to overcome these issues. In this work, oxygen-deficient ferric oxide (Fe₂ O_{3- x} ), prepared by lithiothermic reduction, is used as a low-cost and effective cathodic catalyst. By introducing a small amount of Fe₂ O_{3- x} into the cathode, the battery can deliver a high capacity of 512 mAh g^-1 over 500 cycles at 4 C, with a capacity fade rate of 0.049% per cycle. In addition, a self-supporting porous S@KB/Fe₂ O_{3- x} cathode with a high sulfur loading of 12.73 mg cm^-2 is prepared by freeze-drying, which can achieve a high areal capacity of 12.24 mAh cm^-2 at 0.05 C. Both the calculative and experimental results demonstrate that the Fe₂ O_{3- x} has a strong adsorption toward soluble polysulfides and can accelerate their subsequent conversion to insoluble products. As a result, this work provides a low-cost and effective catalyst candidate for the practical application of lithium-sulfur batteries.