The vanadium redox flow battery (VFB) is an attractive storage technology for large-scale storage applications because of its decoupled power and energy rating. As for almost all rechargeable batteries, VFB encounter the problem of capacity loss after a certain duration of charge–discharge operation.
This demonstrates the advantage that the flow batteries employing vanadium chemistry have a very long cycle life. Furthermore, electrochemical impedance spectroscopy analysis was conducted on two of the battery stacks. Some degradation was observed in one of the stacks reflected by the increased charge transfer resistance.
The all-vanadium flow battery (VFB) employs V 2 + / V 3 + and V O 2 + / V O 2 + redox couples in dilute sulphuric acid for the negative and positive half-cells respectively. It was first proposed and demonstrated by Skyllas-Kazacos and co-workers from the University of New South Wales (UNSW) in the early 1980s , .
It is worth noting that no leakages have been observed since commissioned. The system shows stable performance and very little capacity loss over the past 12 years, which proves the stability of the vanadium electrolyte and that the vanadium flow battery can have a very long cycle life.
A high-performance all-iron non-aqueous redox flow battery comparative study of Nafion series membranes for vanadium redox flow batteries J. Membr. Sci., 510 ( 2016), pp. 18 - 26 Enhanced cycle life of vanadium redox flow battery via a capacity and energy efficiency recovery method
In order to store electrical energy, vanadium species undergo chemical reactions to various oxidation states via reversible redox reactions (Eqs. (1) – (4)). The main constituent in the working medium of this battery is vanadium which is dissolved in a concentration range of 1–3 M in a 1–2 M H 2 SO 4 solution .