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<inf>2</inf>/Br<inf>3</inf>⁻ 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<inf>2</inf> and Br<inf>3</inf>⁻, 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 Br<inf>2</inf>/Br<inf>3</inf>⁻ 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<inf>2</inf>, MEMBr<inf>3</inf>, and TPABr<inf>3</inf> cathodes. Our work provides new approaches to achieve active solid interhalogen chemistry for high-energy electrochemical energy storage devices.