To counteract this imbalance, we briefly exposed the reduced negolyte to air, which brought the cell back into balance. Negolyte exposure to air is a simple and general strategy to restore out-ofbalance ARFBs when a parasitic reduction of the posolyte limits the Coulombic-efficiency. We also tested a capacity-balanced cell with the same negolyte and posolyte composition. By exposing negolyte to air intermittently to oxidize it back to balanced charge, we were able to run this capacity-balanced cell with similar slow fading and stable voltage output (Fig. ).