Redox flow batteries (RFBs) have received significant attentions as useful secondary battery due to their long cycle life, flexible design, and technical advances as other traditional batteries. RFBs are one of the highly safe storage batteries because non-flammable aqueous solutions are used as electrolyte, but the market of the RFBs remains limited because of its low energy density and its cost. All vanadium RFBs have been the standard in nowadays because the same element is used in the positive and negative electrolytes and the issue of the crossover of active species is reduced. In recent years, instead of expensive vanadium ion, organic RFBs are strongly expected by the increasing in needs for low-cost, safe, and trusted energy storage applications. 

  Here, we present our research results on RFBs synthesized with a regular dendritic structure consisting of viologen molecular assemblies¹. The electrochemical properties and viscosity of the integrated molecules were investigated and their potential as flow batteries was examined. We have also been simultaneously searching for polyelectrolyte membranes suitable for organic RFBs, and we report on the performance evaluation of RFBs, using sulfonated polyetheretherketone (SPEEK).

References

[1]  A. Ohira, T. Funaki, E. Ishida, J.-D. Kim, Y. Sato, Redox-Flow Battery Operating in Neutral and Acidic Environments with Multielectron-Transfer-Type Viologen Molecular Assembly, ACS Appl. Energy Mater. 3 (2020) 4377–4383. doi:10.1021/acsaem.0c00067.