Assessing capacity loss remediation methods for asymmetric redox flow battery chemistries using levelized cost of storage

Redox flow batteries, a promising grid-scale energy storage solution, have an open architecture that can host a broad range of redox electrolytes. Vanadium is the most mature chemistry, which is largely due to its symmetry, where all active species are based on a single parent compound, that allows for inexpensive crossover remediation via rebalancing. However, the industry has increasingly sought chemistries with lower-cost and higher-abundance redox couples. Most chemistries cannot be configured symmetrically, though, necessitating research into capacity-recovery methods for asymmetric chemistries. In this work, we adapt our previously developed levelized cost of storage model, which tracks capacity fade and recovery and evaluates the costs across the battery's lifetime, to analyze two classes of asymmetric chemistries, those with active species of finite or infinite lifetimes, and their respective remediation options. For finite-lifetime chemistries, we explore active-species replacement to counter decay. For infinite-lifetime chemistries, we consider two methods for addressing crossover: imposition of pseudo-symmetry via the spectator strategy (i.e., mixed electrolytes) and elimination of crossover via membranes with perfect selectivity. We anticipate this framework will help guide the evaluation and design of new redox chemistries, balancing the desire for low capital costs with the need to remediate capacity repeatedly and inexpensively.