Dr. Hairus Abdullah received his doctoral degree from the Department of Materials Science and Engineering, National Taiwan University of Science and Technology (NTUST), in 2016. He continued to serve as a postdoctoral fellow in the same department till 2019. Afterward, he became a visiting professor in the Department of Materials Science and Engineering, NTUST. In addition, he also supports academic and research activities at Universitas Prima Indonesia (UNPRI), Medan, Indonesia. His research interests are in photocatalysis (including hydrogen evolution reaction, hydrogenation of toxic species, antibacterial application), electrocatalysis, photoelectrocatalysis, and supercapacitors.

1. Introduction.- 2. Materials and experimental procedures.- 3. Characterization and material testing of Ni foam/Ni-doped V₃O₅ cathode.- 4. Developing VO_x cathode on Ni(OH)₂ nano sheets grown on Ni foam substrate.- 5. Assembly of a full-cell supercapacitor with amorphous Ni-doped VO_x-modified Ni(OH)₂ cathode and active-carbon anode.

This book highlights the use/application of Vanadium Oxide as a Supercapacitor (SC) material using the electrodeposition method. The preparation methods, material characterization, and performance testing of VOx-based SC are thoroughly discussed. Electrolyte solutions from VCl3 and other metal precursors are used to form V3O5 electrodes on nickel foam (NF). The cathode can deliver a specific capacitance value of 5689 F/g. The work is improved by depositing V3O5 film on Ni(OH)2 to form a bilayer coating on NF substrate. Ni(OH)2 with a nano-sheet structure is used for the purpose of increasing the specific surface area of V3O5 layer which can achieve specific capacitance of 7500 F/g, the energy density of 167 Wh/kg, and the power density of 199 W/kg. After 10,000 charge-discharge cycles, the capacitance retention rate is 93%. Finally, a full cell SC is assembled using the bilayer electrode and active carbon. The asymmetric and symmetric full cells performed the specific capacitances of 390 F/g and 846 F/g, the energy densities of 286 Wh/kg and 170 Wh/kg, and the power densities of 1149 W/kg and 602 W/g, respectively. After 10,000 charge-discharge cycles, the capacitance retention rates of asymmetric and symmetric full cells are 97% and 95%, respectively.