Molecular Engineering Strategies for Flow Batteries

Abstract

Redox-flow batteries (RFBs) show bright prospects as candidates for large-scale energy storage involving grid-scale electricity construction with flexible intermittent electricity and simplified manufacturing processes. The RFBs are propounded as worthy for industrial requests owing to their flexible serviceability, modular design, and good scalability. The redox-active species has the most vital task in the RFBs and can control the system capacity and energy density via solubility and the redox potential. The energy density is controlled by the solubility of the electroactive materials, cell voltage, and the number of electrons transferred. Molecular engineering has a crucial influence on the solubility of organic redox in electrolytes and justifies the redox potential of organic compounds through the attachment of polar/nonpolar moieties and electron-withdrawing/donating groups adjacent to the redox center. The cost issue and tunable structure of organic redox-active materials have a critical impact on the development of organic and aqueous RFBs. Herein, we focus on molecular engineering strategies related to the enhancement of the solubility and stability of organic redoxmers as posolytes and negolytes in both organic and aqueous RFBs. This chapter is focused on famous categories of active materials, including viologen, quinone, anthraquinone, quinoxaline, and phenazine in aqueous and nonaqueous configuration flow batteries. © 2026 selection and editorial matter, Ram K. Gupta; individual chapters, the contributors.