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.

Automated summary

Li-CFx batteries have the potential to electrify aviation due to their high specific energy. However, the rechargeability of these batteries is hindered by the formation of LiF. This study proposes three mechanisms to explain the transformation of lithium-intercalated CFx into LiF and graphite. By calculating the energetics, the feasibility of these mechanisms is estimated. This work could lead to targeted synthesis strategies for high specific energy rechargeable Li-CFx batteries and has broad applications in investigating phase transformations in two-dimensional heterostructures and layered materials.