SCHEDULED MAINTENANCE
Anti-perovskite cathodes for lithium batteries†
*ab
Abstract
It was recently discovered that Li2FeChO (Ch = S, Se, Te) anti-perovskites exhibit an outstanding rate capability and a good discharge capacity as Li-ion battery cathodes. In this work, we use density functional theory calculations to study the origin of the electrochemical characteristics of anti-perovskite cathodes using Li2FeSO as a model material. We evaluate the phase stability, ion-transport, and structural stability of this material and, interestingly, found that Li2FeSO is meta-stable at 0 K. The experimentally observed anti-perovskite phase likely originates from either entropy stabilization or sluggish decomposition kinetics. When delithiated, the stability of the material worsens. Additionally, over-delithiation may lead to irreversible structural change. The good rate capability of Li2FeSO is attributed to the high Li conductivity, where the low Li ion diffusion barrier (∼0.32 eV) rivals those of state-of-art superionic Li conductors. In the search for materials with a voltage higher than that of Li2FeSO, we screen Co, Cr, Cu, Mn, Mo, Ni, and V substitutions into the Fe site of Li2FeSO. While Cu and Ni substitutions may offer higher average voltages, the corresponding materials are less stable than Li2FeSO.
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