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 t hin film electrode was investigated by analysis of cyclic voltammogram (CV) . Anodic and cathodic peaks on CV were highly asymmetric to each other in s hape, and anodic peak current was larger than cathodic peak current in valu e. In addition, the anodic peak current I-anod, varied linearly with scan r ate 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 contr olled' lithium transport across the electrode \ electrolyte interface. Espe cially 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 el ectrochemical impedance spectroscopy (EIS). The effect of (D) over tilde (L i+) on peak current and peak potential during the 'cell-impedance controlle d' lithium transport was also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.