An Aqueous Zinc-Ion Battery Based on Copper Hexacyanoferrate

A new zinc-ion battery based on copper hexacyanoferrate and zinc foil in a 20mM solution of zinc sulfate, which is a nontoxic and noncorrosive electrolyte, at pH6 is reported. The voltage of this novel battery system is as high as 1.73V. The system shows cyclability, rate capability, and specific energy values near to those of lithium-ion organic batteries based on Li4Ti5O12 and LiFePO4 at 10C. The effects of Zn2+ intercalation and H-2 evolution on the performance of the battery are discussed in detail. In particular, it has been observed that hydrogen evolution can cause a shift in pH near the surface of the zinc electrode, and favor the stabilization of zinc oxide, which decreases the performance of the battery. This mechanism is hindered when the surface of zinc becomes rougher.