Intercalation/deintercalation characteristics of electrodeposited and anodized nickel thin film on ITO electrode in aqueous and nonaqueous electrolytes

The intercalation/deintercalation characteristics of electrochemically formed Ni(OH)2/Ni/ITO electrodes in aqueous KOH and nonaqueous LiPF6+EC:DEC (1:1) electrolyte solutions were studied. The Ni(OH)2 film was grown by Ni electrodeposition and a subsequent anodizing process. The metallic Ni nano-layer between Ni(OH)2 and ITO was identified by X-ray photoelectron spectroscopy (XPS). To understand the characteristics of the Ni(OH)2 film, the intercalation and deintercalation of OH− ion in KOH and Li+ in LiPF6+EC:DEC (1:1) electrolyte were investigated using cyclic voltammetry and charge calculations and further confirmed with the structure, oxide states and interfacial properties of the Ni(OH)2 layer using X-ray diffraction, atomic force microscopy, scanning electron microscopy, XPS, ac impedance spectroscopy, and in situ transmittance spectroscopy. The Ni(OH)2/Ni/ITO electrode showed improved interfacial properties due to the metallic Ni nano-layer when it was compared with directly electrodeposited Ni(OH)2/ITO.