(335b) Aqueous Electrode-Decoupled Redox Flow Battery System Utilizing Earth Abundant Elemental Actives

The ongoing trend towards de-carbonization of the national energy supply has accelerated recently due to the economic reality of renewable energy sources being cheaper than coal, oil and other traditional power sources. The increasing penetration of solar and wind energy sources into the national grid necessitates the adoption of energy storage technologies that can smooth supply fluctuations and ensure gird resiliency. In this price sensitive market, the US department of energy deems a price of $100/KWh or lower to be competitive.¹Thus, battery systems that are competitive in the consumer electronics or automotive sectors are not price competitive in this space without pricing supports.^2,3 Redox flow batteries (RFB) are a cost competitive alternative. Redox flow batteries offer the inherent advantage of decoupled energy and power because the reactants are stored externally. This also ensures that energy scale-up costs are sub-linear, with only storage units being scaled up while the stack is unchanged. Traditional vanadium based redox flow battery systems suffer from a cost disadvantage due to the vanadium actives employed.^4,5 Herein we report a novel titanium-cerium based redox flow battery chemistry that is estimated to cost $64/KWh (~1/3 of the cost of an all-V system) while offering comparable power densities to the all-V RFB. Ti is more abundant than common metals such as Cu, Zn, and Ni in the Earth’s crust while Ce is very close. The second innovation in this system is the use of a modified polyether ketone based anion exchange membrane that ensures long term separation of the Ti and Ce species and allows us to demonstrate essentially capacity fade free cycling over long time scales. The Ti-Ce system satisfies the essential criteria for a RFB system of low cost, single phase reactions, lack of parasitic side reactions and greater than 1V operating voltage. Further, the voltage sensitivity of Ce species in solution serves as an inherent safety mechanism wherein voltage excursions are terminated due to the formation and precipitation of CeO₂. Thus, the Ti-Ce system is a novel, safe, low cost redox flow battery system.

References:

1. Department of Energy. Funding Opportunity Announcement Advanced Research Projects Agency – Energy ( Arpa-E ) Integration and Optimization of Novel Ion. 2016. https://arpa-e.energy.gov/?q=pdfs/ionics-de-foa-0001478.
2. Darling RM, Gallagher KG, Kowalski JA, Ha S, Brushett FR. Pathways to low-cost electrochemical energy storage: a comparison of aqueous and nonaqueous flow batteries. Energy Environ Sci. 2014;7(11):3459-3477. doi:10.1039/C4EE02158D.
3. Gallagher KG, Goebel S, Greszler T, et al. Quantifying the promise of lithium–air batteries for electric vehicles. Energy Environ Sci. 2014;7(5):1555. doi:10.1039/c3ee43870h.
4. Rychcik M, Skyllas-Kazacos M. Characteristics of a new all-vanadium redox flow battery. J Power Sources. 1988;22(1):59-67. doi:10.1016/0378-7753(88)80005-3.
5. Ulaganathan M, Aravindan V, Yan Q, Madhavi S, Skyllas-Kazacos M, Lim TM. Recent Advancements in All-Vanadium Redox Flow Batteries. Adv Mater Interfaces. 2016;3(1):1-22. doi:10.1002/admi.201500309.