Redox flow batteries (RFBs) are promising solutions to large scale energy storage, in particular to leverage power generated by intermittent renewable resources such as wind and solar. Vanadium RFBS (VFRBs) work by storing energy in the form of vanadium ions in solution via the following reactions:

VO²⁺ + H₂O → VO₂⁺ + 2H⁺ + e^- (1)

V³⁺ + e^- → V²⁺ (2)

In the case of the VRFB, crossover of vanadium species from one side of the battery to the other causes significant issues including self-discharge, electrolyte imbalance and transport problems. Understanding the fundamental transport properties is essential to mitigating these issues and bringing the technology closer to market.

This study involves fundamental measurements of VOSO₄ solutions in sulfuric acid electrolyte. The effect of sulfuric acid concentration has been studied by electron paramagnetic resonance spectroscopy, electrochemical methods (cyclic voltammetery, chronoamperometry, Levich type treatment of linear sweep voltammetry and electrochemical impedance spectroscopy) as well as other physiochemical characterization techniques including viscosity. Results will include interpretation of the EPR spectra and electrochemical techniques and related values obtained for the hydrodynamic radius of the vanadium species under investigation. Cyclic voltammograms have been analyzed for k⁰ by both fitting analysis and the treatment of Kingler et al.¹ and are in good agreement. In addition, values of diffusion coefficient have been determined by several electrochemical techniques and EPR and are in good agreement.

1. R. J. Klingler and J. K. Kochi, J. Phys. Chem., 85, 1731–1741 (1981) http://pubs.acs.org/doi/abs/10.1021/j150612a028.