Tungsten diselenide (WSe 2 ) as a high capacity, low overpotential conversion electrode for sodium ion batteries

Tungsten diselenide (WSe 2 ) is demonstrated as an efficient electrode for sodium ion batteries for the first time. A high reversible capacity above 200 mA h g −1 is observed at 20 mA g −1 rate, with over 250 mA h g −1 capacity measured in the first sodium extraction. Assessment of electrolyte and binder materials on performance was examined and an EC/DEC electrolyte with CMC binder emerges to yield the highest capacity and cycling retention. Comparison between WS 2 and WSe 2 distinguishes WSe 2 to exhibit superior performance due to more efficient energetics bearing a small overpotential