An experimental study on cell-impedance-controlled lithium transport through Li1−δCoO2 film electrode with fractal surface by analyses of potentiostatic current transient and linear sweep voltammogram

The effect of the surface roughness on the cell-impedance-controlled lithium transport through the Li1−δCoO2 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−δCoO2 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 tch 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 νch in the LSVs. From the analyses of the PCTs and the LSVs in terms of tch and νch, 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.