Confining acetonitrile–I2 complexes via Fe single-atom sites for rapid and reversible iodine redox kinetics at −40 °C

Abstract

To achieve rapid and reversible iodine redox kinetics under low-temperature conditions, we developed atomically dispersed Fe sites anchored on porous carbon (Fe–PC) that actively engage the confinement of the acetonitrile–I₂ charge-transfer complex, guiding it into an efficient liquid–liquid conversion pathway on the PC surface with a lowered reaction barrier. Consequently, at −40 °C, the Fe–PC/I₂ cathode exhibits an exceptional capacity of 215.9 mAh g⁻¹ at 1C and impressively retains 133.0 mAh g⁻¹ at 20C. This work provides a viable route and fundamental insight for designing high-rate iodine batteries operating under subzero environments.