Lithium Intercalation in LiFe[sub 2]F[sub 6] and LiMgFeF[sub 6] Disordered Trirutile-Type Phases

and disordered trirutile-type phases were prepared by high energy ballmilling, and their electrochemical activity toward lithium was investigated. Within the voltage range of 2.0–4.5 V, exhibited reversible reactivity with lithium, while showed little to no reactivity. An in situ X-ray diffraction experiment was carried out to study the behavior of cells. For , a reversible expansion of the -axis occurred, indicating that Li atoms were intercalated in the rutile tunnels. For , there were minimal lattice constant shifts, but a broadening of most Bragg peaks and distinct charge–discharge hysteresis. We interpreted this as extraction of Li from the metal atom chains of the rutile structure. The theoretical specific capacity for in is 224 mAh/g. Our experiments showed only about 126 mAh/g for this process from the stoichiometric . However, up to 155 mAh/g specific capacity was obtained from nonstoichiometric prepared by adding an extra 0.2 mol of LiF per mole of .