Binder-free copper hexacyanoferrate electrode prepared by pulse galvanostatic electrochemical deposition for aqueous-based Al-ion batteries

Copper hexacyanoferrate (CuHCF) nanoparticles with tunnel-like Prussian blue structure were deposited on graphite substrate via pulse galvanostatic electrochemical deposition at 25 mA cm-2 with both on-time and off-time periods of 0.1 s, which presented the ability to intercalation/de-intercalation of Al ions reversibly in aqueous solution. The crystal structure of the as-prepared CuHCF film was characterized by X-ray diffraction (XRD) analysis. The surface morphology of the film was examined by a field-emission scanning electron microscope (FESEM). Moreover, the electrochemical energy storage performance of the prepared binder-free electrode was examined by cyclic voltammetry and galvanostatic charge-discharge measurements at various rates in aqueous aluminum sulfate electrolyte. CuHCF was verified to be a promising cathode material for aqueous Al-ion batteries. The prepared CuHCF electrode exhibited a high specific capacity of 77.7 mAh g-1 at a current density of 50 mA g-1 and a good rate capability with 67.1% capacitance retention rate at a high current density of 400 mA g-1.