New electrolyte involving iron salts to be used in an all-iron hybrid redox flow battery

New electrolyte involving iron salts to be used as anolyte and/or catholyte in an all-iron hybrid redox flow battery. It comprises various additives that provide key properties such as stability, balanced pH, and ionic conductivity, and inhibit H2 evolution/generation, enabling good quality iron platting.

Market need: Electrochemical energy storage devices are considered key systems due to the massive implementation of energy generation systems from renewables, which in turn need those devices to optimize their efficiency. The most advanced electrolytes in this technology are based on vanadium salts, but their scarcity and high cost limit the expansion that these storage technologies need, so the use of materials with lower cost and more abundant can help to a great penetration of this technology in the market.

Proposed solution: A new electrolyte based on iron salts has been developed, that includes the necessary additives to make the battery work efficiently, stably and with a high voltage. The additives solve the main problems of these batteries, which are the irreversible generation of hydrogen at the negative electrode and the precipitation of iron salts at the positive electrode. These various additives include substances capable of regulating the pH and the ionic conductivity of the solution and other substances capable of maintaining a reducing medium that inhibits the oxidation of iron (II) to iron (III), and the evolution of hydrogen, without inhibiting or hindering the battery's own reactions, such as the different oxidation and reduction reactions of the iron species present in the medium.

Competitive advantages

The additives favor the interaction with the electrode’s surface, enhance membrane performance, and maintain electrolyte stability at the operation conditions.
The only active species involved in the charge/discharge of the battery are the iron cations that can be prepared at different concentrations and can participate in different redox reactions.