In Operando Visualization of the Electrochemical Formation of Liquid Polybromide Microdroplets

Yutong Wu, Po Wei Huang, Joshua D. Howe, Yu Yan, Jose Martinez, Anna Marianchuk, Yamin Zhang, Hang Chen, Nian Liu

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Zinc–bromine flow batteries are promising for stationary energy storage, and bromine-complexing agents have been used to form phase-separated liquid polybromide products. However, an understanding of the dynamics of polybromide nucleation is limited due to the beam sensitivity and complexity of polybromides. Here we report an in operando platform composed of dark-field light microscopy and a transparent electrochemical cell to reveal the dynamics of polybromide formation in their native environment. Using our platform, we confirm and reveal the liquid nature, chemical composition, pinning effect (strong interaction with Pt), residual effect (residual charge products on the surface), self-discharging, and over-oxidation of the polybromide products. The results provide insights into the role of complexing agents and guide the future design of zinc–bromine flow batteries. Furthermore, our in operando platform can potentially be used to study sensitive species and phases in other electrochemical reactions.

Original languageEnglish
Pages (from-to)15228-15234
Number of pages7
JournalAngewandte Chemie - International Edition
Issue number43
StatePublished - Oct 21 2019


  • Zn–Br flow batteries
  • in operando visualization
  • ionic liquids
  • optical microscopy


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