Two‐Electron Redox Chemistry Enabled High‐Performance Iodide‐Ion Conversion Battery

Abstract A single‐electron transfer mode coupled with the shuttle behavior of organic iodine batteries results in insufficient capacity, a low redox potential, and poor cycle durability. Sluggish kinetics are well known in conventional lithium–iodine (Li−I) batteries, inferior to other conversion congeners. Herein, we demonstrate new two‐electron redox chemistry of I − /I + with inter‐halogen cooperation based on a developed haloid cathode. The new iodide‐ion conversion battery exhibits a state‐of‐art capacity of 408 mAh gI −1 with fast redox kinetics and superior cycle stability. Equipped with a newly emerged 3.42 V discharge voltage plateau, a recorded high energy density of 1324 Wh kgI −1 is achieved. Such robust redox chemistry is temperature‐insensitive and operates efficiently at −30 °C. With systematic theoretical calculations and experimental characterizations, the formation of Cl−I + species and their functions are clarified.