Electrodialysis (ED) has emerged as a promising technique; however, the influence of solution composition remains under investigation, mostly the presence of contaminants. This work explores the separation of Li+ from a solution containing Fe2+ and Al3+ ions using a monovalent cation exchange membrane. The performance of ED reactors (two and five compartments) was evaluated at different current densities (25–75 mA/cm2) over time. Results showed that the five-compartment ED configuration achieved the highest Li separation efficiency (19.3%) at 75 mA/cm2, with a current efficiency of 7% and energy consumption of 10 kWh/mol. Lower current density (25 mA/cm2) showed the highest current efficiency (13.6%) and lowest energy consumption (1.6 kWh/mol), with 12.6% Li separation efficiency. Separation efficiency of Li reached 64% and a purity of 81% after 66h in a five-compartment ED configuration at 25 mA/cm2. The interaction between Li+ and multivalent cations/anions was found to enhance Li+ separation by reducing free activity of multivalent ions through the formation of complex species and favoring the selective transport of Li+.