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

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.