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

Though massive efforts have been devoted to exploring Br-based batteries, the highly soluble Br₂ /Br₃ ^- 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 Br₂ and Br₃ ^- , 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 Br⁰ is fixed by iodine (I), thoroughly eliminating cross-diffusing Br₂ /Br₃ ^- 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 I₂ , MEMBr₃ , and TPABr₃ cathodes. Our work provides new approaches to achieve active solid interhalogen chemistry for high-energy electrochemical energy storage devices.