Using innovative FeF3 cathode materials in Li batteries working under spacecraft applications

Abstract

The discovery of new cathode materials for lithium batteries is a slow process yet crucial task to develop advanced LIBs, and almost all known commercial cathode materials are still based on those identified in the 1990s. Thus, searching for new cathode materials is crucial for increasing the performance of Lithium batteries especially in the spacecraft industry as storage devices used in this domain need to be as small and light as possible to ease their integration in the spacecraft as well as minimizing the energy required for take-off. Conversion materials such as iron trifluoride (FeF3) are of particular interest as they exhibit high specific capacity (237 mAh.g−1 in intercalation for anhydrous FeF3 versus 200 mAh.g−1 for typical NCA or NMC) and high voltage. This study focuses on using innovative gaseous fluorination with F2 gas to prepare anhydrous FeF3 while favoring the formation of a porous structure to maximize electrochemical performances. We were able to tune the crystalline structure, composition, and morphology of the fluorination product obtained by selecting the precursor as well as tailoring the fluorination treatment. After a complete electrochemical characterization of all fluorination products obtained, FeSi2 appeared as the best precursor to maximize the performances of FeF3 in lithium batteries. Electrochemical tests were performed on our homemade FeF3 and the results were compared to a commercial product, namely NCA. Both cells were cycled at a current density of C/10, and a DoD of 80%. Those conditions were chosen because they are close to those found in geostationary satellites batteries. Electrochemical tests demonstrated that anhydrous FeF3 synthesized by gaseous fluorination exhibits an increased performance compared to NCA when these 2 materials are used as a cathode material in lithium batteries on a short-term cycling analysis.