Three-Dimensionally Reinforced Freestanding Cathode for High-Energy Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) battery cathodes suffer from poor conductivity, rapid dissolution of intermediate products, and potentially destructive volume change during cycling. The optimal way to minimize these problems could be a construction of a nanocomposite cathode scaffold combining different components selected for their particular functions. Here, we have combined the excellent electronic conductivity of reduced graphene oxide, polysulfide adsorption ability of the ultrafine manganese oxide nanocrystals, rapid ion/electron dissemination efficiency of nanosized sulfur, and outstanding mechanical stiffness and good electrical conductivity of Na alginate/polyaniline hybrid binder in a single electrode heterostructure. At 0.2 A g-1, an RT Na-S battery containing the freestanding cathode delivers an initial specific cap acity of 631 mA h g-1. By delivering a nominal discharge voltage of 1.81 V, our Na-S batteries bestow a high specific energy of 737 W h kg-1 at the 2nd cycle and 660 W h kg-1 was retained after 50 cycles. The effect of the amount of electrolyte additive is also well demonstrated in this study. The electrode fabrication process provides a new approach to tailor the design and preparation of effective cathodes for the room-temperature sodium-sulfur batteries.