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

This work reports an all-active solid interhalogen compound IBr as a cathode, in which the active I fixes the oxidized Br⁰ without generating crossing-diffusing Br₂/Br₃ ⁻ species during the whole charge and discharge process. The Zn||IBr battery delivers improved energy density compared with those of I₂, MEMBr₃, and TPABr₃ cathodes.

Abstract

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.

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