Preparation and electrochemical characteristics of microemulsion-derived Li(Ni, Co)O₂ nanopowders

Nanosized LiNi_0.9Co_0.1O₂ powders used in lithium-ion batteries are successfully prepared via a water-in-oil microemulsion process. The average particle sizes of the microemulsion-derived LiNi_0.9Co_0.1O₂ powders are in nanometer scale. The obtained powders are much smaller in size than the specimens prepared via the conventional solid state and sol–gel processes. Oxygen has significant enhancement effects on the cationic ordering of the calcined powders. Highly cation-ordered LiNi_0.9Co_0.1O₂ powders with a layered \( R\bar 3m \) structure are obtained after heat-treatment at 800 °C in O₂. In addition, the high intensity ratio of I ₀₀₃/I ₁₀₄ reveals that lithium ions and transition metal ions are regularly situated at the 3a and 3b sites, respectively, rendering the high cationic ordering. The discharge capacity of the first cycle for the specimen calcined at 800 °C in O₂ is 170.9 mAh/g. After 20 cycles, the capacity retention of LiNi_0.9Co_0.1O₂ powders is 93.2%, indicating that LiNi_0.9Co_0.1O₂ powders with good cycling characteristics are obtained via the microemulsion process.