Insertion of Calcium Ion into Prussian Blue Analogue in Nonaqueous Solutions and Its Application to a Rechargeable Battery with Dual Carriers

We observed the first electrochemical insertion of Ca2+ into Prussian blue analogue, MnFe(CN)6, in nonaqueous solutions of Ca(CF3SO3)(2) and various solvents including ionic liquid at 60 degrees C. The kinetics for the Ca2+ insertion reaction were studied by cyclic voltammetry, and were compared to those of Na+ intercalation. By coupling this phenomenon with metallic anodes, two energy storage devices were made. Ca anode produced a primary cell that operated at a voltage of around 2.0 V. When Mg plate was used as an anode, the negative active material associated with CF3SO3-, which we have already reported was newly formed at the surface of Mg plate. By combining the negative active material, we have fabricated a novel rechargeable battery using dual ion transport species of Ca2+ for the cathode and CF3SO3- for the anode, and demonstrated that the battery showed repeated discharge/charge performance.