Preparation, Structure, and Thermal Stability of New NixCo₁₋₂xMnx(OH)₂ (0 ≤ x ≤ ¹/₂) Phases

The preparation, characterization, and thermal stability of Ni x Co 1 - 2 x Mn x (OH) 2 (0 ≤ x ≤ 1 / 2 ) is reported. These hydroxides are prepared by coprecipitation as the first step in the preparation of the corresponding Li[Ni x Co (1 - 2 x ) Mn x ]O 2 (0 ≤ x ≤ 1 / 2 ) oxides. Precipitates dried at room temperature adopt the hexagonal CdI 2 structure. Thermal studies show that the hexagonal CdI 2 type (RT) structure transforms to a cubic spinel-type solid solution (Ni x Co (1 - 2 x ) Mn x ] 3 O 4 (0 ≤ x ≤ 3 / 8 ) above about 150 °C that becomes well-crystallized at 600 °C. An intermediate turbostratic structure phase occurs between room temperature and 150 °C. This phase is present in small amounts in room-temperature-dried Ni x Co 1 - 2 x Mn x (OH) 2 materials with x ≥ 3 / 8 . The results show that the drying method of the precipitate induces different phases with different bulk and tap density. This could have a major influence on the morphology, composition, density, and cell performance of Li[Ni x Co (1 - 2 x ) Mn x ]O 2 (0 ≤ x ≤ 1 / 2 ) oxides obtained from these dried precipitates.