Beyond Transition Metal Oxide Cathodes for Electric Aviation: The Case of Rechargeable CF_x

Abstract

Current and next-generation transition metal oxide-based rechargeable battery chemistries are likely to fall short of the specific energy needed to electrify aircraft. One approach to enabling electric aviation is making high specific energy primary battery chemistries such as the Li-CF x chemistry rechargeable. Though Li-CF x possesses nearly triple the specific energy of current Li-ion cells, numerous fundamental issues related to the overall reaction mechanism exist. In this work, we use density functional theory calculations to build a fundamental understanding of possible reaction mechanisms. The direct formation of LiF and graphite seems unlikely because of the sluggish kinetics of F diffusion in CF x . The discharge occurs likely via lithium ion diffusion into the CF x host to form an LiCF ternary compound. Reasonable agreement between the open-circuit voltage (OCV) determined experimentally (∼4.05 V) and from DFT (4.27 ± 0.14 V) for the formation of ternary LiCF is obtained. Suppressing LiF formation by stabilizing the intermediate ternary LiCF could thus enable rechargeability of the Li-CF x chemistry.

Edge-Propagation Discharge Mechanism in CFx Batteries—A First-Principles and Experimental Study

“…A significant amount of DFT modeling work on CF x have been reported. 8,35,[45][46][47][48][49][50][51][52][53][54]…”

Interfaces in Solid Electrolyte Interphase: Implications for Lithium-Ion Batteries

“…Lithium-ion (Li-ion) batteries have revolutionized consumer electronics and road transportation , and offer a promising route to achieve electric aviation. − The interface between the electrode and the electrolyte in a battery, and the related interphases formed, strongly influence the Coulombic efficiency, cycling performance, and power capability of the battery. , The properties of a surface or an interface can be vastly different from those of the bulk material. For example, lithium iodide doped with alumina has Li-ion conductivity orders of magnitude higher than any of the individual components due to the space charge effect.…”

Interfacial Effects on Solid Electrolyte Interphase in Lithium-ion Batteries

“…Lithium-ion (Li-ion) batteries have revolutionized consumer electronics and road transportation 1,2 and offer a promising route to achieve electric aviation. [3][4][5] The interface between electrode and the electrolyte in a battery and the related interphases formed are major factors controlling the Coulombic efficiency, cycling performance and power performance of the battery. 6,7 The properties of a surface or an interface can be vastly different from those of the bulk material.…”