Challenges for Organic Active Materials for Stationary Electrical Energy Storage

We have developed high performance flow batteries based on the aqueous redox behavior of small organic and metalorganic monomers composed of earth-abundant elements. These redox active materials can be inexpensive and exhibit rapid redox kinetics and high solubilities, potentially enabling rapid scaling of flow batteries at reduced cost. Adequate molecular lifetime has been one of the most challenging requirements to satisfy. We have shown that the amount of lost capacity is determined by the molecular calendar life, which can depend on state of charge, but is independent of the number of charge-discharge cycles imposed. I will discuss problems in measuring extremely small capacity fade rates and how an understanding of molecular decomposition mechanisms has permitted us to design molecules with decadal projected lifetimes and even to reverse capacity fade by recomposing decomposed molecules within the functioning battery electrolyte.