An experimental study on cell-impedance-controlled lithium transport through Li 1− δCoO 2 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 Li 1− δ CoO 2 film electrode was experimentally investigated in a 1 M LiClO 4-PC solution by the analyses of the potentiostatic current transient (PCT) and the linear sweep voltammogram (LSV). The flat and fractal Li 1− δ CoO 2 film electrodes were prepared on the Pt/polished Al 2O 3 substrate and the surface-modified Pt/unpolished Al 2O 3 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 current on the potential scan rate positively deviated from the generalised Randles–Sevcik behaviour above the characteristic scan rate ν ch in the LSVs. From the analyses of the PCTs and the LSVs in terms of t ch and ν 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.