High‐Performance Lithium‐Iodine Flow Battery

A cathode‐flow lithium‐iodine (Li–I) battery is proposed operating by the triiodide/iodide (I 3 − /I − ) redox couple in aqueous solution. The aqueous Li–I battery has noticeably high energy density (≈0.28 kWh kg −1 cell ) because of the considerable solubility of LiI in aqueous solution (≈8.2 m ) and reasonably high power density (≈130 mW cm −2 at a current rate of 60 mA cm −2 , 328 K). In the operation of cathode‐flow mode, the Li–I battery attains high storage capacity (≈90% of the theoretical capacity), Coulombic efficiency (100% ± 1% in 2–20 cycles) and cyclic performance (>99% capacity retention for 20 cycles) up to total capacity of 100 mAh.