Featured: Hydrogen-Based Redox FLOW Batteries

Demand for large-scale energy storage is increasing, especially as renewable energy resources, such as solar and wind, become more prevalent. These variable energy generators require that large-scale energy storage is used to arbitrage and minimize fluctuations into the grid. As a promising candidate for energy storage and load leveling, redox flow batteries (RFBs) have been considered. However, due to the challenging issues such as low cell performance, durability, and high electrolyte cost, their wide-spread adoption has not occurred.

An electrochemical RFB system capable of meeting these demands is the hydrogen-bromine system. It has highly reversible and kinetically favored electrochemical reactions, soluble chemical species, high current-density operation, and a relatively inexpensive electrolyte. We have shown that the optimization and understanding of the primary losses can result in power densities of 1.5 W/cm² and limiting current densities over 4 A/cm² for discharge at ambient conditions. However, a key attribute of any RFB system is robust and durable performance, especially upon cycling. In this talk, we will report on the cyclic performance of the RFB, and especially the effect of operating conditions such as electrolyte concentration, cut-off potential, and current on the cycling performance.

In addition, other hydrogen chemistries will be examined including inexpensive (H₂-Fe-ion) and high-voltage (H₂-Ce) systems. The various performances and tradeoffs of these systems will be detailed. Finally, the various results will be put into context using experiments and simulations to elucidate the most critical issues in the field and outline areas of needed research.