Synthesis of LiCoO2 by decomposition and intercalation of hydroxides

A low-temperature, solid-state process for the synthesis of high-quality intercalation oxides has been developed. Finely divided cobalt hydroxide-lithium hydroxide mixtures, prepared by precipitation and freeze-drying, transform directly to highly ordered LiCoO2 of the alpha-NaFeO2 structure type (high-temperature LiCoO2) upon firing in air at temperatures of 200-300 degrees C. The mechanism of transformation has been determined using transmission electron microscopy and X-ray diffraction. Crystallites of Co(OH)(2) decompose and intercalate with Li to form LiCoO2 without changing particle shape, orientation, or crystallinity. The absence of a CoOOH intermediate phase indicates that the intercalation step is rapid compared to the Co(OH)(2) --> CoOOH decomposition. Although the product obtained at temperatures as low as 100 degrees C is electrochemically active, firing at higher temperatures further improves capacity and cyclability.