Kinetically Enhanced Reaction Pathway to Form Highly Crystalline Layered LiCoO₂ at Low Temperatures Below 300 °C

Layered LiCoO₂ is usually synthesized after a prolonged sintering process at high temperatures (≥800 °C) for 10-20 h. This study developed a "hydroflux process" to obtain highly crystalline and layered LiCoO₂ at a low temperature of 300 °C within 30 min. Molten mixed hydroxide-containing water molecules significantly accelerated the formation of LiCoO₂, which showed a highly reversible capacity of 120 mAh g^-1 without postannealing. The reaction mechanism study showed fast growth of LiCoO₂ crystals, suggesting that the excess molten hydroxides containing water dissolve the cobalt species of HCoO₂^-. Consequently, the accelerated LiCoO₂ formation suppresses the competing reaction of Co₃O₄ formation, leading to spinel LiCoO₂ formation at low temperatures. Excess water in the starting materials further accelerated the crystal growth of LiCoO₂, forming large particles (>1 μm). Moreover, the layered LiCoO₂ began to form at 150 °C. This study is the first experimental demonstration that proves the thermodynamic stability of layered LiCoO₂ at low temperatures (150-300 °C) under ambient pressure. This novel process offers significant energy savings in the production process of LiCoO₂ and other ceramics materials.