The kinetics of lithium transport through vanadium pentoxide composite and film electrodes by current transient analysis

Abstract

The kinetics of lithium transport through vanadium pentoxide composite and film electrodes have been investigated in a 1 M solution of LiClO 4 in propylene carbonate using current transient technique. In the case of the vanadium pentoxide composite electrode, all the cathodic and anodic current transients experimentally measured hardly followed the Cottrell behaviour and the relation between initial current level in current transient and applied potential step held Ohmic law. Lithium transport through the composite electrode was theoretically analysed by means of the numerical simulation of the current transient under the assumption of the ‘cell-impedance controlled’ lithium transport. The current transients theoretically calculated shared quantitatively well those experimentally measured. In contrast, all the cathodic and anodic current transients experimentally obtained from the film electrode, exhibited clearly a linear relationship between logarithmic current and logarithmic time, followed by an exponential decay. From the results, it is suggested that lithium transport through the film electrode proceeds under the ‘diffusion controlled’ lithium transport towards rough (fractal) interface. The difference in the mechanism of lithium transport between through vanadium pentoxide composite electrode and through film electrode was discussed in terms of the chemical diffusivity of lithium ion and ‘cell-impedance’ of the two electrodes.