High purity lithium isotopes have significant applications in nuclear industry and other related fields. Many of the ongoing lithium isotope separation processes have environmental issues, and the use of mercury is one of them. As part of the development of a new lithium isotope separation process, the effect of the concentration gradient and electric field were studied using experimental electrochemical cells and a recently built numerical model. Samples from the experimental test were collected and then purified by the ion exchange chromatography for ICP-MS analysis. The concentration and isotopes ratio measured with ICP-MS indicated reasonable time dependence behavior. The data confirmed that the difference in the diffusion and migration rate of the isotopes facilitates Li isotope separations. Furthermore, the potentiostatic scanning tests were conducted, and they revealed the time it takes to achieve separation with diffusion and migration. Finally, the electrochemical model with mass transfer predicted the isotopes ratio distribution for comparison with the experimental results. The mass transfer of Li isotopes confirmed the excellent separation potential using the electrochemical approach.