Ethanol Based Electrolyte for Ultra-stable Zn/NiHCF Batteries

Abstract

Prussian blue analogs (PBAs) have attracted widespread attention as cathode materials for aqueous zinc ion batteries (AZIBs) in view of their open frameworks, adjustable redox sites, and high operating voltages. However, the poor cycling stability limits its practical application severely. Herein, the cubic K2NiFe(CN)6 (NiHCF) is prepared as the active cathode material for AZIBs. The cycling stability of the Zn/NiHCF battery is improved greatly just by simply replacing the H2O with ethanol (EA) as electrolyte solvent. Ex-situ XRD and SEM characterizations reveal the stable morphology of NiHCF during charging/discharge process in the 0.5 M Zn(OTf)2-EA electrolyte and violent phase transformation from NiHCF to Zn2Fe(CN)6 in 3 M Zn(OTf)2-H2O electrolyte, indicating that 0.5 M Zn(OTf)2-EA electrolyte can inhibit the negative phase transformation aging process of NiHCF and improve the electrochemical performance effectively. Impressively, the Zn/NiHCF battery with 0.5 M Zn(OTf)2-EA as electrolyte exhibits a really high capacity retention rate of 94.2 % after 500 cycles at 150 mA g−1.