Owing to their high theoretical capacity, metal fluorides have attracted significant interest as materials for fabricating the cathode of lithium secondary batteries. In the present study, a nanocomposite of LiF and FeF2 is prepared by a fluorolytic sol-gel method in an ethanol solution, for use as the cathode material of a lithium secondary battery. The produced LiF/FeF2 composite is characterized by broad X-ray diffraction peaks attributed to the nanosized (similar to 10 nm) LiF and FeF2 crystals, a large Brunauer-Emmett-Teller surface area of 119 m(2) g(-1), and adsorption-desorption hysteresis, attributed to the presence of mesopores. The results of charge-discharge tests indicates an initial discharge capacity of 225 mAh (g-LiF/FeF2)(-1) through reversal conversion at a current rate of 10 mA (g-LiF/FeF2)(-1). Based on a combination of galvanostatic intermittent titration, X-ray absorption, and X-ray diffraction investigations, a new reaction mechanism is developed, namely, the conversion of the local environment of an Fe atom from a rutile-type FeF2 structure to a rhenium trioxide-type FeF3 structure during charging, with the subsequent discharge resulting in the insertion of Li+ into the rhenium trioxide-type FeF3 structure, followed by the conversion reaction to LiF and FeF2.