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 L iNi1-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 differe nt preparation methods. A preparation method (method B) which uses spherica l 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(O H)(2) and Co(OH)(2). Method A produced compounds with relatively high degre es of cation mixing which reduces electrochemical utilization (discharge ca pacity), increases irreversible capacity, and reduces stability on cycling of the cathode material. Method B, in contrast, produced cathode material w ith a much reduced degree of cation-mixing, thus improving the electrochemi cal 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 c ontent of Co (value of x) is increased. (C) 1999 The Electrochemical Societ y. S0013-4651(99)02-056-X. All rights reserved.