Self-vanadium liquid flow energy storage system

Vanadium redox flow batteries (VRFBs) hold great promise as a scalable and efficient energy storage solutions for renewable energy systems as compared to its several counterparts.

However, as the grid becomes increasingly dominated by renewables, more and more flow batteries will be needed to provide long-duration storage. Demand for vanadium will grow, and that will be a problem. “Vanadium is found around the world but in dilute amounts, and extracting it is difficult,” says Rodby.

Among the various types of RFBs, vanadium redox flow battery (VRFB) stands out for its ability to eliminate cross-contamination between electrolytes, a common issue in other flow battery chemistries which induces self-discharge of the device.

To address this challenge, a novel aqueous ionic-liquid based electrolyte comprising 1-butyl-3-methylimidazolium chloride (BmimCl) and vanadium chloride (VCl 3) was synthesized to enhance the solubility of the vanadium salt and aid in improving the efficiency.

Vanadium prices and corresponding electrolyte prices from 1980 through 2021. The left-hand Y axis measures the market price of vanadium pentoxide, a common source of vanadium sold on the global market. The right-hand Y axis translates those prices into prices for vanadium-based electrolytes for flow batteries.

During discharge, vanadium ions at the electrodes undergo electrochemical reactions, where the carbon felt or graphite electrodes facilitate electron transfer to the external circuit, and protons move across a cation-exchange membrane (e.g., Nafion) to balance charge in the system.