Kinetically Enhanced Reaction Pathway to Form Highly Crystalline Layered LiCoO 2 at Low Temperatures Below 300 °C.

Layered LiCoO 2 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 LiCoO 2 at a low temperature of 300 °C within 30 min. Molten mixed hydroxide-containing water molecules significantly accelerated the formation of LiCoO 2 , which showed a highly reversible capacity of 120 mAh g -1 without postannealing. The reaction mechanism study showed fast growth of LiCoO 2 crystals, suggesting that the excess molten hydroxides containing water dissolve the cobalt species of HCoO 2 - . Consequently, the accelerated LiCoO 2 formation suppresses the competing reaction of Co 3 O 4 formation, leading to spinel LiCoO 2 formation at low temperatures. Excess water in the starting materials further accelerated the crystal growth of LiCoO 2 , forming large particles (>1 μm). Moreover, the layered LiCoO 2 began to form at 150 °C. This study is the first experimental demonstration that proves the thermodynamic stability of layered LiCoO 2 at low temperatures (150-300 °C) under ambient pressure. This novel process offers significant energy savings in the production process of LiCoO 2 and other ceramics materials.