Electrochemical Properties and Thermal Stability of Li[sub a]Ni[sub 1−x]CO[sub x]O[sub 2] Cathode Materials

Conductive and electrochemical properties as well as thermal stability of where x = 0–0.3 and a = 1.0–0.4 have been studied using impedance spectroscopy, galvanostatic intermittent titration technique, cyclic voltammetry, electrochemical cycling, and differential scanning calorimetry (DSC). The electronic conductivity of partially charged material (a ≤ 0.8) increases substantially when the cobalt content is increased to x = 0.3 from 0.2. The mobility, chemical diffusion coefficient, and ion diffusion coefficient in the partially charged material are in the neighborhood of , , and , respectively, and are rather insensitive to the values of a and x. Results of electrochemical and DSC studies show that is the best cathode material for a Li cell of all materials studied here in view of the best cycle stability, the smallest irreversible capacity, and the greatest thermal stability with minimal reduction of specific capacity from that of . © 2000 The Electrochemical Society. All rights reserved.