Electrochemical investigation of the Li insertion-extraction reaction as afunction of lithium deficiency in Li1-xNi1+xO2

The electrochemical characteristics of Li1 - xNi1 + xO2 samples have been e xtensively investigated as a function of the lithium deficiency x in the na rrow composition range 0.008-0.065. In particular, the electrochemical and structural behaviours of the quasi-stoichiometric compound (x = 0.008) have been proved to be strongly different from those exhibited by a sample with x = 0.025. The faster kinetics for Li transport combined with structural c hanges which are minimized in the quasi-ideal compound explain the lack of notable polarization voltage and the good cycle life of the latter cathode material with a stable capacity of 140 A h/kg over 40 cycles at C/10 rate. In addition, interesting and useful correlations (i) between the cathode im pedance and the lithium deficiency and (ii) between the evolution of the ca thode impedance and the cycling performance have been established. (C) 2001 Elsevier Science Ltd. All rights reserved.