Theoretical approach to cell-impedance-controlled lithium transport through Li1−δCoO2 film electrode with fractal surface: numerical analysis of generalised diffusion equation

In the present work, lithium transport through the Li1−δCoO2 film electrode with a fractal surface was investigated under the cell-impedance-controlled constraint at the electrode/electrolyte interface along with the impermeable constraint at the electrode/current collector interface by using the numerical analysis of the generalised diffusion equation (GDE). Under the cell-impedance-controlled constraint, all the potentiostatic current transients (PCTs) calculated from the flat and fractal electrodes did not exhibit the generalised Cottrell behaviour until the characteristic time tch and they were significantly affected in shape by the electrode thickness. In the case of the linear sweep voltammograms (LSVs) determined from the flat and fractal electrodes, all the power dependence of the peak current on the potential scan rate above the characteristic scan rate νch negatively deviated from the generalised Randles–Sevcik behaviour. From the analyses of the PCTs and the LSVs, furthermore, it is recognised that the cell-impedance-controlled lithium transport through the fractal Li1−δCoO2 film electrode is enhanced by the surface roughness, but it is impeded by the internal cell resistance.