(327b) Electrode-Decoupled Redox Flow Batteries Enable Demand-Conformal Energy Storage
The increasing penetration of intermittent, renewable energy sources on the national grid and the planned transition to a majority renewable or all-renewable grid necessitates the deployment of technologies that turn solar and wind into dispatchable resources. This requires the development of long duration energy storage technologies that move beyond charge-discharge cycling with a few hours of energy stored to a charge-store-discharge, demand-conformal paradigm enabling energy storage at the days to weeks scale. 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 redox flow battery chemistry based on elemental actives that is estimated to cost $64/KWh (~1/3 of the cost of an all-V system) with a levelized cost of storage (LCOS) of < $0.05/ KWh-cycle while offering comparable power densities to the all-V RFB. The abundance of the elemental actives will allow for the deployment of enough batteries to store ~200x the current global electricity production. 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 cationic species and allows us to demonstrate essentially capacity fade free cycling over long timescales. This 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, this system can be stored at a fully charged state for multiple days and enables demand-conformal, extended-duration energy storage
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