A Neutral pH Aqueous Organic–Organometallic Redox Flow Battery with Extremely High Capacity Retention

We demonstrate an aqueous organic and organometallic redox flow battery utilizing reactants composed of only earth-abundant elements and operating at neutral pH. The positive electrolyte contains bis((3-trimethylammonio)propyl)ferrocene dichloride, and the negative electrolyte contains bis(3-trimethylammonio)propyl viologen tetrachloride; these are separated by an anion-conducting membrane passing chloride ions. Bis(trimethylammoniopropyl) functionalization leads to ∼2 M solubility for both reactants, suppresses higher-order chemical decomposition pathways, and reduces reactant crossover rates through the membrane. Unprecedented cycling stability was achieved with capacity retention of 99.9943%/cycle and…

• AR
  Advanced Research Projects Agency - Energy

  Awards: DE-AR0000348, DE-AC05-76RL01830
• HS
  Harvard School of Engineering and Applied Sciences