SYNTHESIS OF LICOO2 BY DECOMPOSITION AND INTERCALATION OF HYDROXIDES

A low-temperature, solid-state process for the synthesis of high-quali ty intercalation oxides has been developed. Finely divided cobalt hydr oxide-lithium hydroxide mixtures, prepared by precipitation and freeze -drying, transform directly to highly ordered LiCoO2 of the alpha-NaFe O2 structure type (high-temperature LiCoO2) upon firing in air at temp eratures of 200-300 degrees C. The mechanism of transformation has bee n determined using transmission electron microscopy and X-ray diffract ion. Crystallites of Co(OH)(2) decompose and intercalate with Li to fo rm LiCoO2 without changing particle shape, orientation, or crystallini ty. The absence of a CoOOH intermediate phase indicates that the inter calation step is rapid compared to the Co(OH)(2) --> CoOOH decompositi on. Although the product obtained at temperatures as low as 100 degree s C is electrochemically active, firing at higher temperatures further improves capacity and cyclability.