Particle size effect of Li[Ni0.5Mn0.5]O2 prepared by co-precipitation

Spherical (Ni0.5Mn0.5)(OH)(2) with different secondary particle size (3 mu m, 10 mu m in diameter) was synthesized by co-precipitation method. Mixture of the prepared hydroxide and lithium hydroxide was calcined at 950 degrees C for 20 h in air. X-ray diffraction patterns revealed that the prepared material had a typical layered structure with R (3) over barm space group. Spherical morphologies with mono-dispersed powders were observed by scanning electron microscopy. It was found that the layered Li[Ni0.5Mn0.5]O-2 delivered an initial discharge capacity of 148 mAh g(-1) (3.0-4.3 V)though the particle sizes were different. Li[Ni0.5Mn0.5]O-2 having smaller particle size (3 mu m) showed improved area specific impedance due to the reduced Li+ diffusion path, compared with that of Li[Ni0.5Mn0.5]O-2 possessing larger particle size (10 mu m). Although the Li[Ni0.5Mn0.5]O-2 (3 mu m) was electrochemically delithiated to Li-0.39[Ni0.5Mn0.5]O-2, the resulting exother. mic onset temperature was around 295 degrees C, of which the value is significantly higher than that of highly delithiated Li1-delta CoO2 (similar to 180 degrees C). (C) 2008 Published by Elsevier Ltd.