Preparation and characterization of nanometric-sized LiCoO_2 cathode materials for lithium batteries by a novel sol-gel method

摘要

Nanometric-sized LiCoO_2 powders were obtained from a novel sol-gel method, in which the gels were synthesized by the polymerization of citric acid and hydroxypropyl cellulose. Molar ratios of citric acid to metal ions were varied, and the resulting effects on the properties of powders were studied using Fourier transfer infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that with a molar ratio of citric acid/metal ions =1, the resin contains a number of bidentate ligand fractions and higher portion of C-C-O structure, which makes it possible to synthesize the low temperature phase of LiCoO_2 at a temperature as low as 300 °C. The powder calcined at 600 °C exhibits a pure high temperature phase of LiCoO_2 (HT-LiCoO_2) with a particle size of about 40-60 nm and a specific surface area of 25.24 m~2/g. The electrode prepared at 600 °C exhibits a better HT-LiCoO_2 structure and demonstrates a higher first run charge/discharge capacities at 186 and 168 mAh/g, respectively.