K.J. Takeuchi, A.C. Marschilok, E.S. Takeuchi
Stony Brook University,
Keywords: battery, zinc, aqueous, manganese oxide
Summary:Rechargeable aqueous zinc/ manganese oxide (Zn/alpha-MnO2) batteries are a possible alternative to lithium ion batteries for scalable stationary energy storage applications due to their low cost, safety and environmentally benign components. However, aqueous zinc systems can display low capacity retention under use conditions. This highlights the critical need for full understanding of the electrochemical reaction mechanisms, to continue to advance the system. In this presentation, operando, spatiotemporally resolved synchrotron X-ray fluorescence mapping measurements on a custom aqueous Zn/alpah-MnO2 cell provided direct evidence of an Mn dissolution-deposition faradaic mechanism that governs the electrochemistry. Simultaneous visualization and quantification of the Mn distribution in the electrolyte revealed the formation of aqueous Mn species during discharge and depletion on charge. The findings are supported by ex situ transmission electron microscopy (TEM), X-ray diffraction, Mn K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. These findings provide a foundation for advancing the battery systems based on dissolution deposition chemistries suitable for scalable stationary energy storage.