The present work investigates the effects of cation mixing on electrochemical lithium intercalation involving absorption reaction and diffusion of lithium ion in porous Li1-deltaNi1-yCoyO2 electrodes (0 less than or equal to delta; y less than or equal to 1) by using electrochemical impedance spectroscopy (EIS). The measured electrode potential, instantaneous IR drop, lithium absorption resistance and lithium diffusivity have been discussed as functions of lithium content (1 - delta) and cobalt content y with respect to cation mixing between the Ni3+ and Li+ ions in porous Li1-deltaNi1-yCoyO2 electrodes.