Particle size effect of Li[Ni 0.5Mn 0.5]O 2 prepared by co-precipitation

Abstract

Spherical (Ni 0.5Mn 0.5)(OH) 2 with different secondary particle size (3 μm, 10 μm in diameter) was synthesized by co-precipitation method. Mixture of the prepared hydroxide and lithium hydroxide was calcined at 950 °C for 20 h in air. X-ray diffraction patterns revealed that the prepared material had a typical layered structure with R 3 ¯ m space group. Spherical morphologies with mono-dispersed powders were observed by scanning electron microscopy. It was found that the layered Li[Ni 0.5Mn 0.5]O 2 delivered an initial discharge capacity of 148 mAh g −1 (3.0–4.3 V) though the particle sizes were different. Li[Ni 0.5Mn 0.5]O 2 having smaller particle size (3 μm) showed improved area specific impedance due to the reduced Li + diffusion path, compared with that of Li[Ni 0.5Mn 0.5]O 2 possessing larger particle size (10 μm). Although the Li[Ni 0.5Mn 0.5]O 2 (3 μm) was electrochemically delithiated to Li 0.39[Ni 0.5Mn 0.5]O 2, the resulting exothermic onset temperature was around 295 °C, of which the value is significantly higher than that of highly delithiated Li 1− δ CoO 2 (∼180 °C).