Synthesis of LiCoO2 cathodes by an oxidation reaction in solution and their electrochemical properties

Layered LiCoO2 was synthesized by an oxidation of Co2+ ions in aqueous solutions by lithium peroxide in the presence of excess lithium hydroxide, followed by firing at 400–900°C. The samples were characterized by X-ray diffraction (XRD) and wet-chemical analysis. Although single phase Li1+xCo1−xO2 samples with a Li/Co ratio > 1 could be obtained at lower firing temperatures, they were metastable and transformed to the stoichiometric LiCoO2 with a Li/Co ratio of 1.0 at higher firing temperatures (T ≈ 900°C). The samples fired at low temperatures (T ≤ 700°C) exhibited lower capacity and poor electrochemical cyclability in the lithium cells, due to a disordering of the Li+ and Co3+ ions, and poor crystallinity. On the other hand, the samples fired at 900°C exhibited a capacity as high as 150 mAh/g in the voltage range 4.3–3.3 V, with excellent cyclability due to good cation ordering and crystallinity.