Investigation of lithium transport through lithium cobalt dioxide thin film sputter-deposited by analysis of cyclic voltammogram

The transport of lithium through sputter-deposited lithium cobalt dioxide thin film electrode was investigated by analysis of cyclic voltammogram (CV). Anodic and cathodic peaks on CV were highly asymmetric to each other in shape, and anodic peak current was larger than cathodic peak current in value. In addition, the anodic peak current I-anod, varied linearly with scan rate v to the power 0.66-0.69 (i.e. I-anod proportional to nu (0.66) to nu (0.69)), over the scan range of two orders of magnitude, irrespective of the surface roughness of the oxide film. The CVs were simulated as a function of the scan rate at various chemical diffusivities, (D) over tilde (Li+) of lithium in the oxide by numerical analysis, assuming 'cell-impedance controlled' lithium transport across the electrode \ electrolyte interface. Especially the numerically simulated CVs at (D) over tilde (Li+) = 10(-10) cm(2) s(-1) quantitatively shared those experimentally obtained. This (D) over tilde (Li+) value was in good accordance with that value determined from electrochemical impedance spectroscopy (EIS). The effect of (D) over tilde (Li+) on peak current and peak potential during the 'cell-impedance controlled' lithium transport was also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.