Lithium-Ion Transfer Reaction at the Interface between Partially Fluorinated Insertion Electrodes and Electrolyte Solutions

Lithium-ion transfer reactions at the interface between insertion electrodes and electrolyte solutions were investigated by using partially fluorinated lithium manganese spinel oxides as model electrodes. LiMn1.8Li0.1Ni0.1O4−ηFη (η = 0, 0.018, 0.036, 0.055, 0.073) were synthesized as model compounds. Electrochemical impedance spectroscopy was carried out to evaluate the influence of surface fluorine on the interfacial lithium-ion transfer process. Taking an adion model into account, it is considered that an adion formation process takes place with partial desolvation, and then a process with surface diffusion of the adion occurs followed by the electrode incorporation of the adion with the loss of the remaining solvent. The adion model was also used to compare the interfacial resistances for the lithium-ion transfer process. It was suggested that the fluorine substitution influences the latter process. The importance of structural characterization at the electrode surface on the lithium-ion transfer behav...