Sample dependent performance of aqueous copper hexacyanoferrate/zinc batteries

In this work, we investigate factors affecting the capacity retention of aqueous copper hexacyanoferrate/Zn batteries. We compare the performance of four different copper hexacyanoferrate (CuHCF) samples as cathode in CuHCF/Zn cells with Na2SO4 and ZnSO4 based electrolytes at different pH. In Na2SO4 electrolyte, the capacity retention is improved at lower pH, whereas cells with ZnSO4 electrolyte perform similarly at pH 2 and 4. Finally, we show that the performance of CuHCF/Zn cells is highly dependent on the CuHCF sample, underlining the necessity for detailed synthesis description and thorough structural characterization of electrode materials.