Prussian blue: a new framework of electrode materials for sodium batteries

Prussian blue and its analogues consisting of different transition-metal ions (Fe, Mn, Ni, Cu, Co and Zn) have been synthesized at room temperature. Insertion of Na into KFe2(CN)6 in a carbonate electrolyte exhibited a reversible capacity near 100 mA h g−1 with no capacity fade in 30 cycles. The data indicate that a Na-ion battery with a Prussian blue framework as a cathode will be feasible.