Synthesis by sol–gel method and electrochemical properties of LiNiO2 cathode material for lithium secondary battery

The optimum conditions for synthesising LiNiO2 by a sol–gel method and its electrochemical properties are investigated. Single-phase LiNiO2 powder is synthesised by the sol–gel method using citric acid as chelating agent and LiNO3, Ni(NO3)2·6H2O as starting materials. The optimum conditions for the synthesis of LiNiO2 are calcination at 800 °C for 13 h in an oxygen stream after preheating at 600 °C for 5 h in air. The particles of LiNiO2 powder are generally in the form of a smoothly edged polyhedron and their average size is approximately 3–5 μm. The resulting LiNiO2 electrode shows relatively large discharge capacities and good cycle performance. The initial discharge capacity and that at the 20th cycle are 168 and 155 mAh g−1 at a current density of 7.5 mA g−1 in a voltage range 3.0–4.2 V. The decrease in the quantity of the intercalated Li ions during the first discharge as compared with that of the de-intercalated Li ions is considered to result from the destruction of the unstable tetrahedral sites and the diminution of Li atoms contained in excess.