Solid Interhalogen Compounds with Effective Br0 Fixing for Stable High‐energy Zinc Batteries

Abstract Though massive efforts have been devoted to exploring Br‐based batteries, the highly soluble Br 2 /Br 3 − species causing rigorous “shuttle effect”, leads to severe self‐discharge and low Coulombic efficiency. Conventionally, quaternary ammonium salts such as methyl ethyl morpholinium bromide (MEMBr) and tetrapropylammonium bromide (TPABr) are used to fix Br 2 and Br 3 − , but they occupy the mass and volume of battery without capacity contribution. Here, we report an all‐active solid interhalogen compound, IBr, as a cathode to address the above challenges, in which the oxidized Br 0 is fixed by iodine (I), thoroughly eliminating cross‐diffusing Br 2 /Br 3 − species during the whole charging and discharging process. The Zn||IBr battery delivers remarkably high energy density of 385.8 Wh kg −1 , which is higher than those of I 2 , MEMBr 3 , and TPABr 3 cathodes. Our work provides new approaches to achieve active solid interhalogen chemistry for high‐energy electrochemical energy storage devices.