Ether-based electrolyte enabled Na/FeS2 rechargeable batteries.

We demonstrate for the first time that by simply substituting ether-based electrolyte (1.0 M NaCF 3 SO 3 in diglyme) for the commonly used carbonate-based electrolyte, the cyclability of FeS 2 towards sodium storage can be significantly improved. A sodiation capacity over 600 mAh/g and a discharge energy density higher than 750 Wh/kg are obtained for FeS 2 at 20 mA/g. When tested at 60 mA/g, FeS 2 presents a sodiation capacity of 530 mAh/g and retains 450 mAh/g after 100 cycles, much better than the cycling performance of Na/FeS 2 tested in carbonate-based electrolyte. [ABSTRACT FROM AUTHOR]