To go beyond the state-of-the-art, CompBat has developed a comprehensive set of modelling tools to allow evaluating the performance of a prospective molecule in a flow battery, from basic physicochemical parameters to battery and stack performance all the way to the system cost. Furthermore, machine learning was used to develop a tool to allow prediction of redox potentials of any organic molecule. This tool will be beneficial to all researchers working on flow batteries, and also in other fields where estimation of redox potentials is of crucial interest. The tools developed in CompBat will allow accelerated computation aided design of new molecules to further improve the flow battery performance.
One of the challenges of aqueous organic flow batteries is to identify inexpensive candidates for flow battery applications. Cost evaluations can be performed using common evaluation techniques developed for design of chemical plants, but this approach is time consuming and requires detailed knowledge of the synthesis route and the different unit operations etc. CompBat proposed two approaches to address this challenge: focus on bio-inspired molecules and solid boosters. We proposed to use safe and inexpensive natural products, such as vitamins and amino acids as building blocks for aqueous flow battery materials operating close to neutral pH. The advantages of natural product-derived materials include: 1) scalable production in tanks by fermentation with reasonable cost, 2) inherent safety and expected biodegradability due to their biological origin and natural roles even in the human body, 3) solubility in water, and 4) high degree of functionalization, minimizing the need for synthetic steps to modify them. This could enable significant cost reduction for sustainable electrochemical energy storage. The solid boosters, on the other hand, can be manufactured from inexpensive and abundant raw materials. As the material is introduced into the flow battery solution tanks as beads composed only of the active material, conductive additive and binder, the extra cost will simply be the cost of the raw materials. The modelling tools developed in for the solid boosted systems will provide critical design parameters that are needed to be taken into account when choosing suitable boosters and organic materials. The techno-economic modelling has highlighted that sufficient cell performance is required to achieve low cost. Especially cell voltage and solubility of the materials are crucial, as otherwise system costs for power becomes prohibitive even when employing low cost solid boosters.
The project has provided new molecules and structures for energy storage, as well as tools to develop next generation materials. This will generate significant interest in research of both aqueous and non-aqueous flow battery systems employing bioinspired molecules. More importantly, the project offers prediction tools to understand in detail which candidate molecules are the most promising for further study as redox mediators. The proposed approach for utilization of bioinspired molecules for renewable energy storage will be highly valuable for the scientific community, generating more research and pushing to improve the energy storage utilizing abundant materials. So far, the field of organic redox flow batteries has been driven by flow battery researchers, and especially the design of aqueous systems has received only little attention from the organic chemistry community. This project will help to change this. Furthermore, the synthetic chemistry required to access the flow battery materials will have to be low-cost, sustainable, and allow access to end products that are highly water soluble. These requirements will, out of necessity, promote renewal in the field.
The project will help in green transition in electricity generation, by accelerating the development of the stationary energy storage systems.
