A moving-boundary model with activity correction for the diffusion of lithium in LiCoO2 electrodes and the electrochemical reaction on the surface of electrode particles was formulated in a reproduction of the discharge/charge voltage process in batteries that have a LiCoO2 cathode and a mesocarbon-microbead anode. Activity correction for the electrochemical reaction as well as the diffusion of lithium where the LiCoO2 structural phase transition occurs during discharge and charge was considered. An accurate representation of the discharge/charge voltage profiles was obtained by using the moving-boundary model with the activity correction. The activity correction incorporated into the moving-boundary model can improve the discontinuous gaps in the discharge voltage profiles at the surface of conjugate LiCoO2 electrode particles.