There is an urgent need to minimize the dependence on fossil fuels consumption. The use of renewable energy sources, such as wind and solar generation, requires its integration to large-scale storage systems to balance the production and consumption. The challenge arises from the development of a scalable, inexpensive and efficient storage solution. In this sense, flow batteries appear as a promising technology. Nowadays, the state-of-art is based on the use of vanadium as the redox active material, although other chemistries have been extensively developed. In this work, we focus our study on the use of organic molecules as active materials, as well as we developed a monitoring system to get an insight of the flow battery operation.

We believe that the use of organic materials obtained from natural sources can provide a sustainable, inexpensive and scalable solution. Furthermore, the new compounds need to be highly soluble and possess a suitable redox potential to produce competitive batteries with high energy and power densities. In this work, we tested new synthetized organic molecules to overcome these challenges. First, we studied pyridoxal derivatives obtained from Vitamin B6, providing an example of materials synthetized from natural sources. We next studied bisphosphonate as a new substituent for the widespread viologen core with an improved redox potential. Finally, we successfully introduced azoniafluorenone as a new organic family for energy storage. Its high solubility coupled with the ability to store two electrons at neutral pH resulted in large storage capacity.

Both the improvement of the existing systems as well as the development of new ones require methods capable to monitor the battery during operation in a reliable way. In this thesis, we present a measurement system that allows getting an insight of the battery operation by recording the half-cell state of charges and overpotentials of each side of the cell independently. We used this system to study the performance of both the vanadium and an organic flow battery during operation. Furthermore, we extended its use to analyze the improvement on the battery operation when utilizing a novel chemical treatment to activate the battery electrodes.