An experimental study on cell-impedance-controlled lithium transport through Li1-delta CoO2 film electrode with fractal surface by analyses of potentiostatic current transient and linear sweep voltammogram

Abstract

The effect of the surface roughness on the cell-impedance-controlled lithium transport through the Li1-deltaCoO2 film electrode was experimentally investigated in a 1 M LiClO4-PC Solution by the analyses of the potentiostatic current transient (PCT) and the linear sweep voltammogram (LSV). The flat and fractal Li1-deltaCoO2 film electrodes were prepared on the Pt/polished Al2O3 substrate and the surface-modified Pt/unpolished Al2O3 substrate, respectively. From the ac-impedance spectra obtained from the flat and fractal electrodes, it is found that the apparent self-similar fractal dimension reduces the charge-transfer resistance. All the PCTs did not exhibit the generalised Cottrell behaviour until the characteristic time t(ch) and all the power dependence of the peak cur-rent on the potential scan rate positively deviated from the generalised Randles-Sevcik behaviour above the characteristic scan rate v(ch) in the LSVs. From the analyses of the PCTs and the LSVs in terms of t(ch) and v(ch), furthermore, it is experimentally confirmed that the surface roughness plays a significant role in the kinetic facilitation of the interfacial charge-transfer reaction during the whole lithium intercalation and deintercalation processes. (C) 2005 Elsevier Ltd. All rights reserved.