Static theoretical investigations of organic redox active materials for redox flow batteries

Abstract New efficient redox flow batteries (RFBs) are currently of great interest for large-scale renewable energy storage. Further development requires improvement of the redox active materials. Quantum chemical methods allow to screen large numbers of redox active molecules for required molecular properties. Especially the redox potentials are calculated in high-throughput studies. In addition, calculations of other properties such as solubility or stability and in-depth analysis of the electronic structure are performed on smaller number of molecules. This review provides an overview of various known classes of active material molecules and their results in quantum chemical calculations. We will focus on electronic structure methods such as density functional theory and wave function-based methods. Significant theoretical results are presented and discussed for each considered class of redox-active molecules. In addition, the various quantum chemical approaches are also examined, specifically with regard to their advantages and limitations. Another focus of this review is on comparing theoretically predicted results with experimental studies, which are discussed using various examples. Finally, further challenges and trends in the theoretical development of active materials are highlighted.