Energetics of Phase Transformation Mechanisms in Li-CFx Batteries

Li-CFx batteries have the potential to successfully electrify segments of aviation due to their high specific energy of over 800 Wh/kg. However, the rechargeability of this chemistry is hindered due to the formation of LiF. Previously, we showed that a lithium-intercalated CFx is most likely to form during discharge due to favorable kinetics. In this work, we propose three mechanisms by which the lithium-intercalated CFx could transform to yield LiF and graphite, the thermodynamically stable products. We use density functional theory calculations to compute the energetics of the mechanisms and estimate the regimes in which the mechanisms could occur feasibly. This work could lead to targeted synthesis strategies to suppress the decomposition mechanisms, paving the way for a high specific energy rechargeable Li-CFx battery. The mechanisms described herein may be more broadly applied to investigate phase transformations in two-dimensional heterostructures and other layered materials.