Phase Stability and Transport Mechanisms in Antiperovskite Li3OCl and Li3OBr Superionic Conductors

Emmanouil (Manos) Kioupakis

Associate Professor

kioup@umich.edu

2106 HH Dow

T: (734) 764-3321

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Alexandra Emly, Emmanouil Kioupakis, and Anton Van der Ven (2013)

Chemistry of Materials, 25(23):4663-4670.

We investigate phase stability and ionic transport mechanisms in tworecently discovered superionic conductors, Li3OX (X = Cl, Br), fromfirst principles. These compounds, which have an antiperovskite crystalstructure, have potential applications as solid electrolytes in Li-ionbatteries. We identify a low-barrier three-atom hop mechanism involvingLi interstitial dumbbells. This hop mechanism is facile within the (001)crystallographic planes of the perovskite crystal structure and isevidence for the occurrence of concerted motion, similar to ionictransport in other solid electrolytes. Our first-principles analysis ofphase stability predicts that antiperovskite Li3OCl (Li3OBr) ismetastable relative to Li2O and LiCl (Li Br) at room temperature. Wealso find that although the band gap of Li3OCl exceeds S eV, themetastable antiperovskite becomes susceptible to decomposition intoLi2O2, LiCl and LiClO4 above an applied voltage of 2.5 V, suggestingthat these compounds are most suited for low-voltage Li batteriesprovided the formation of Li2O can be suppressed.

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