Continuous production of LiCoO₂ fine crystals for lithium batteries by hydrothermal synthesis under supercritical condition

Abstract

Specific features of supercritical hydrothermal crystallization synthesis (SHCS) by a rapid heating flow type method are reviewed. The attractive features of the method are (i) quantitative production of ultrafine particles, and (u) control of particle morphology or crystal structure by varying the pressure, temperature or reaction atmosphere (reducing or oxidizing).

In this study, we use this method to continuously produce LiCoO_z fine crystals that are used as for the cathode materials of rechargeable lithium ion batteries. LiOH and Co(NO& were chosen as starting materials. For oxidizing Co(II) to Co(III), O₂ was introduced into the reactor after decomposing HzOz aqueous solution in a preheating tubing. LiCoO₂ particles were formed in a single phase at supercritical conditions. scanning electron micrographs showed that the particle size was in the range of 500 to 1,000 nm in diameter. Electrochemical characterization was performed by a constant current discharge and charge test. Little decrease in the discharge capacity suggests high stability of the LiCoO_z crystals prepared by this method.

Key Words:

• Supercritical water
• Hydrothermal synthesis
• Li ion secondly battery
• LiCoO_z