Mixed-valence induced during the intercalation of lithium ions into uranium fluorides

Abstract

The mixed-valence in uranium fluorides LiU 4F 16 and UF 4 can be induced (or eliminated) by the intercalation (deintercalation) of lithium ions into these compounds. These processes can be electrochemically performed both with LiU 4F 16 (or LiTh 4F 16) and with monoclinic UF 4 as starting materials using a liquid electrolyte composed of propylene carbonate as solvent and LiClO 4 as salt. In the cases of UF 4 and LiU 4F 16, the electrochemical intercalation of Li + into the host matrix is reversible and a maximum of three Li + ions per U 4F 16 unit can be reversibly intercalated. Additional experimental evidences of the mixed-valence in these fluorides are presented such as the Electron Paramagnetic Resonance characterization of the starting materials and of those electrochemically modified.