Preparation and characterization of high-density spherical LiCoO2 cathode material for lithium ion batteries

The high-density spherical LiCoO2 is expected as an important direction for LiCoO2 cathode material. Spherical Co(OH)(2) powders were prepared via a "controlled crystallization" method using Co(NO3)(2), NaOH and NH3. To mix Co(OH)(2) and lithium sources in a molar ratio of Li:Co = 1.05:1.00, the Li2CO3 was uniformly coated on the surface of the spherical Co(OH)(2) precursor using LiOH.H2O and NH4HCO3. The mixed powders were sintered at 700-800 degreesC for 12-16h to obtain spherical LiCoO2 powders. The structures of Co(OH)(2), Li2CO3 coated Co(OH)(2) and LiCoO2 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical test of charge-discharge proved the spherical LiCoO2 cathode material had excellent electrochemical performance. At the current of 0.2 and 1.0 C, the cathode material showed initial discharge capacity of 148.4 and 141.7 mAh g(-1), and retention of 97.6 and 91.7% after 40 cycles, respectively. The lax pile-density and tap-density of the powders are as high as 1.9 and 2.8 g cm(-3), respectively, which are remarkably higher than the non-spherical LiCoO2 powders available as commercial cathode materials. The high-density spherical LiCoO2 cathode material can be used in the lithium ion batteries to greatly increase the batteries' energy density. (C) 2003 Published by Elsevier B.V.