Synthesis of LixNi0.85Co0.15O2 by the PVA-precursor method and charge–discharge characteristics of a lithium ion battery using this material as cathode

Polycrystalline powder of LixNi0.85Co0.15O2 was synthesized from poly(vinyl alcohol) gel (a PVA-precursor). The crystalline phase of LixNi0.85Co0.15O2 was developed without any minor phase above 600°C. The crystallization proceeded without any prominent heat event, which indicated homogeneous distribution of constituents and insignificant amount of diffusion barrier. The crystalline powder prepared from the PVA-precursor had relatively smaller particle size, larger surface area, and higher carbon content than the one prepared by the conventional solid state reaction. Charge–discharge property was studied by using a coin-type cell containing LixNi0.85Co0.15O2 as cathode material, and Li metal as the anode, in a potential range of 2.8–4.3 V. Initial discharge capacity (at a rate of C/10) of the cell was 170 mA h/g. At high rate of 1C, the cycling reversibility for the cell with LixNi0.85Co0.15O2 prepared from the PVA-precursor was observed to be much better than that with the one prepared by the solid state reaction. After 90 continuous cycles at constant rate of 1C, the decrease of discharge capacity was less than 20 mA h/g in the case of the PVA-precursor method, whereas it was about 80 mA h/g for the solid state reaction.