Room temperature electrochemical cycling of F-ions in CsMnFeF 6 Brent Melot University of Southern California, USA This talk will present our group’s recent work that reports the first example of a reversible battery based on the electrochemical (de)insertion of F-ions at room temperature. 1 We demonstrate that after three cycles, one full equivalent of F-ions can be reversibly cycled in CsMnFeF 6 . Electrochemical impedance spectroscopy and Mössbauer spectroscopy suggests the formation of fluoride vacancies in early cycles generates mixed-valent Fe that enhances the electrical conductivity of the electrode. Furthermore, ex situ powder diffraction reveals a subtle expansion and contraction of the cubic lattice during oxidation (insertion) and reduction (removal) respectively, that eventually leads to the evolution of new reflections corresponding to a closely related orthorhombic polytype in later cycles. This topotactic transformation suggests that structural derivatives of the fluorite structure offer a promising class of materials for creating high-performance F-ion insertion electrodes. References 1. Jessica L. Andrews, Eric T. McClure, Kenneth K. Jew, Molleigh B. Preefer, Ahamed Irshad, Matthew J. Lertola, Daniel D. Robertson, Charlene Z. Salamat, Michael J. Brady, Louis F. J. Piper, Sarah H. Tolbert, Johanna Nelson Weker, Bradley F. Chmelka, Bruce S. Dunn, Sri R. Narayan, William C. West, and Brent C. Melot ACS Energy Letters 2022 7 (7), 2340- 2348DOI: 10.1021/acsenergylett.2c01324
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© The Author(s), 2021
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