Given the exhaustion of traditional non-renewable energy sources, the competitiveness of energy storage systems has become especially socio-economically important for the coming years in Europe. Redox flow batteries (RFB) are a highly appealing and promising technology for this as they offer advantages such as modularity, fast response time, energy decoupling and power. Nevertheless, current RFB are restricted by the rarity and costs of redox-active substances.

This project has the goal of overcoming these barriers by developing a prototype second-generation RFB (RFB2), based on the use of nano-structured electrode materials and organic electrolytes composed of natural redox-active p-aromatic molecules. The innovative design of RFB2 uses electrolytes that are "green, ecological and inexhaustible", and which are not subject to geopolitical batteries, with the following advantages:

• i) Easily scaleable using abundant and cheap materials.
• ii) Faster kinetics.
• iii) Higher stability with low trans-membrane ion "intercrossing".
• iv) High energy density.
• v) The solubility and potential of redox-active substances by means of introducing functional groups in the π-aromatic system.

In addition, the aim is to develop in-situ diagnosis and prognosis strategies to monitor interphase evolution and detect fault mechanisms. This will evaluate their ageing and estimate component lifetimes. Lastly, a demonstration phase will validate the prototype RFB2 as an efficient and low cost system for inclusion in a smart grid.