Electrochemical energy storage of nanocrystalline vanadium oxide thin films prepared from various plating solutions for supercapacitors

Nanocrystalline V2O5 is electrochemically deposited onto an indium tin oxide substrate in VOSO4-ebased solution with various acetate additives, i.e., lithium acetate, sodium acetate, and potassium acetate. The deposition conditions including pH value and acetate additive are found to be crucial factors in influencing the deposition rate, crystallinity, and porous structure of V2O5 electrodes. The electrochemical capacitive behavior of the deposited V2O5 electrodes in KCl electrolyte is investigated by cyclic voltammetry at various scan rates, ranged from 5 to 200 mV s(-1). The specific capacitance of V2O5 electrode prepared from the potassium acetate containing plating solution is up to 350 F g(-1), indicating that the level of K+ occupancy reaches as high as 0.71. This suggests that the occupancy of K+ ions is in tetrahedral and eight coordinated sites in V2O5 crystals. The capacitance retention at 200 mV s(-1) compared to that at 5 mV s(-1) reaches to 75% for this electrode. The enhanced performance is mainly attributed to the highly porous structure which significantly increases the active sites, imparts oxide/electrolyte interfaces for energy storage, and subsequently enhances the rate of insertion/extraction of K+ ions. The V2O5 electrode is capable of delivering high energy density up to 48.6 Wh kg(-1), demonstrating a significant potential for thin-film energy storage devices. (C) 2018 Elsevier Ltd. All rights reserved.