Redox-flow batteries (RFB) represent a promising battery technology. Unlike many other battery systems, with RFB the performance (i.e. how quickly the battery can be charged) and capacity (i.e. how much energy the battery can store) can be changed independently of each other. RFB are particularly interesting as storage for renewable energies. Commercially available RFB typically use inorganic vanadium salts dissolved in concentrated sulfuric acid. As part of HIPOLE Jena, organic electrolytes based on polymers, i.e. plastics, are being investigated, making the use of critical metals/metal ions in the electrolytes unnecessary. However, there are still several challenges to be overcome before polymer-based RFB can play a larger role. The materials used in these batteries are often not as stable and may store less energy compared to the inorganic materials. In order to better understand the properties of materials and electrochemistry, close collaboration among researchers from different disciplines and the use of advanced investigation methods are required.
HIPOLE Jena aims to find new and advanced ways to develop the next generation of grid-scale energy storage by bringing together FSU Jena’s years of experience in polymer design and synthesis as well as state-of-the-art molecular level investigation capabilities through the HZB.
The molecular design of these polymer-based materials allows electrons to be accepted, stored, and released. In addition to this “functionality”, solubility, molar mass, and molecular structure are of crucial importance. In addition to the arsenal of modern synthetic methods for the design of these materials, previously unknown structure-property relationships will be quantitatively investigated in solution. This investigation will be made possible in particular by unique molecular hydrodynamic methods such as (molecular) viscometry and analytical ultracentrifugation. These methods allow an absolute determination of the molar mass, the diffusion coefficients, and hydrodynamic volumes. Together with densimetry, this allows a quantitative investigation of polymer structures at the molecular level but also the investigation of global electrolyte properties, which are important for technological implementation. The influence of the molecular composition, conformation, and architecture of the materials in both charged and discharged states, considering their stability, enables the targeted design of new materials through well-understood relationships. The use of synchrotron-based scattering methods is intended to provide complementary insight into the molecular structure of the materials. A direct correlation with the final battery performance should establish the RFB as a realistic energy storage device for the future.