ℌFeF3 as a cathode material in lithium ion batteries working in spacecraft conditions”

Abstract

Lithium-ion batteries are widely used in spacecraft for their high volumetric and gravimetric energy densities thus enabling the conception of lightweight and compact devices. To improve this battery technology in terms of energy density, an urgent need for new cathode materials must be satisfied. Indeed, a performance limit was reached with intercalation materials; new electrochemical processes such as conversion type must be developed. In this work, we ran electrochemical tests on iron trifluorides based cathode materials which are engaged both in intercalation process and conversion one. Theoretically, these compounds, through intercalation process, can improve energy density of battery up to 252 Wh/kg and up to 467 Wh/kg through conversion process. Iron trifluorides have different allotropic phases, which can clearly favor good electrochemical processes but fluorides compounds and more particularly anhydrous ones are not easy to prepare. In this study, using various precursors and innovative gaseous fluorination, anhydrous forms of iron trifluorides have been prepared without any thermal post treatment while maintaining a good particle size. We will demonstrate that, by changing the precursors, morphology as well as structure of iron trifluoride can be tuned. Electrochemical tests in geostationary satellite conditions are promising and will be compared with NCA cathode used in the same electrochemical conditions as a commercial reference.