A Multielectron Macromolecular Ruthenium–Bipyridine Electrolyte for Redox Flow Batteries

Renewable power sources offer a compelling path to decarbonized electricity generation, but their inherent intermittency often mismatches real-world demand. Efficient, scalable energy storage is therefore essential to capture surplus generation and deliver power on demand. Redox flow batteries (RFBs) are particularly attractive for grid applications, yet their practical energy density is frequently limited by the narrow electrochemical stability window of aqueous electrolytes and by predominantly one-electron redox chemistries. Here we report the synthesis and electrochemical characterization of a macromolecular ruthenium complex soluble in organic solvents that undergoes a reversible three-electron redox process. Cyclic voltammetry and galvanostatic charge–discharge measurements confirm multielectron accessibility and stable cycling behavior. Notably, the complex retains electrochemical performance over 100 charge–discharge cycles, highlighting the promise of multielectron, macromolecular redox couples in organic electrolytes as a strategy to increase RFB energy density.