A long cycle life, high coulombic efficiency iron molten air battery

Despite the recent advancements in iron molten air batteries, great challenges still remain to realize cycling stability, high energy efficiency and a long-term cycling life. Herein, we demonstrate a new iron molten air battery for large-scale energy storage. We replace the KCl–LiCl–LiOH eutectic electrolyte used in our previous study with a Li0.87Na0.63K0.50CO3 eutectic electrolyte with added NaOH and LiOH. A fin air electrode configuration is designed to improve the coulombic efficiency. Cycling tests for the iron molten air battery showed a stable performance through 450 cycles with nearly 100% coulombic efficiency and an average discharge potential of ∼1.08 V when charged at a constant current of 0.05 A and discharged over a constant 100 Ω load to a 0.7 V cutoff at 500 °C. Moreover, the iron molten air battery had an excellent high-rate response up to 6.4C with a high coulombic efficiency of 95.1%. These results provide critical advances in developing iron molten air batteries with high efficiency and a long-term service life.