Approach to Tuning the Dispersion Stability of TEMPO-substituted Polymer Nanoparticles for Aqueous Organic Redox Flow Batteries.

Hydrophilic redox polymer nanoparticles with zwitterionic moieties were synthesized to improve material utilization for semi-solid redox flow batteries. TEMPO was 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 showed 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 semi-solid redox flow batteries. Among the compositions studied, the introduction of 10 mol% zwitterionic moiety resulted 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 semi-solid redox flow batteries.