Investigation of the many oxidation states of vanadium for the purpose of making a rechargeable battery
Pilson, Kathryn L.
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The demand of large energy storage systems continues to increase with the development and improvement of renewable energy sources such as wind turbines and photovoltaic arrays. Electrochemical storage, or battery storage, such as lead-acid, lithium-ion, sodium based, and redox flow batteries (RFB), can be implemented for large scale energy storage. One of the most popular RFB is the all-vanadium redox flow cell (VRFB), which has a longer longevity, greater stability, and lower cost compared to other battery systems. The single metal system employs V2+/V3+ and VO 2+/VO2+ as half cells for the flow battery. But, there are still various phenomena associated with the vanadium redox flow cell that are not fully understood. Also, the limitations of this system need to be reduced in order to fully supply the demand.To better understand the VRFB, the multiple oxidation states of vanadium were investigated using multiple methods. Ultraviolet visible spectroscopy (UV-VIS) and rotated disk electrode cyclic voltammetry (RDE CV) were used to characterize the different oxidation states. Electrochemical Impedance Spectroscopy (EIS) was employed to investigate the redox couples used in the VRFB as well as a constructed VRFB. While exploring the various oxidation states a precipitate was formed. The identity of the precipitate was determined using energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD).