This study presents zwitterion-functionalized redox-active polymer nanoparticles that enable stable dispersion and enhanced electrochemical performance in aqueous redox flow batteries (RFBs). 10 mol% zwitterionic content significantly improves material utilization and reversibility. The strategy maximizes redox efficiency in semisolid systems and highlights a promising route for high-density, aqueous organic RFBs.

Hydrophilic redox polymer nanoparticles with zwitterionic moieties are synthesized to improve material utilization for semisolid redox flow batteries (RFBs). TEMPO is chosen as the charge storage moiety, taking advantage of its high redox-activity in pH-neutral aqueous electrolytes. Redox-active polymer nanoparticles copolymerized with the zwitterionic moiety show significant changes in surface properties, indicating promising dispersion stability and electrochemical performance even at more than 1 mol% zwitterionic moiety in the copolymer in prototype semisolid RFBs. Among the compositions studied, the introduction of 10 mol% zwitterionic moiety results in the best combination of material utilization and cycle stability. This approach is an effective molecular design strategy to achieve high performance and high volumetric density semisolid RFBs.