The experimental charge and discharge profiles of a LiCoO2 electrode show that the overpotential of the electrode does not change much during galvanostatic charge, but changes significantly during galvanostatic discharge. Semi-empirical porous electrode models are presented to simulate the charge and discharge profiles of the LiCoO2 electrode. The symmetry factor is empirically assumed to decrease with the state of discharge of the electrode to enable the model predictions to agree well with the experimental discharge profiles.