Effect of preparation methods of LiNi1-xCoxO2 cathode materials on their chemical structure and electrode performance

We have studied effects of different starting materials on preparation of LiNi1-xCOxO2 cathode material for a Li-ion cell where x = 0.1, 0.2, and 0.3, and the electrochemical properties of resulting compounds from two different preparation methods. A preparation method (method B) which uses spherical powder of Ni1-xCox(OH)(2) as one of the starting material produced a much superior cathode material than the other method (method A) which uses Ni(OH)(2) and Co(OH)(2). Method A produced compounds with relatively high degrees of cation mixing which reduces electrochemical utilization (discharge capacity), increases irreversible capacity, and reduces stability on cycling of the cathode material. Method B, in contrast, produced cathode material with a much reduced degree of cation-mixing, thus improving the electrochemical properties. The spherical particle of material prepared by method B has the additional advantage of improved packing density of the electrode with improved volumetric energy density. The ratio of c/a was increased and the electrochemical stability on cycling of the material was improved as the content of Co (value of x) is increased. (C) 1999 The Electrochemical Society. S0013-4651(99)02-056-X. All rights reserved.