Dependence of concentration polarization on discharge profile in electrochemical lithium extraction

Electrochemical lithium extraction is an emerging and rising technology that can extract lithium from sea water and salt lake. In this work, we investigate the performance of lithium extraction under different discharge profiles during the extraction process. Our experiment results show that, the output purity, production rate and energy consumption depend sensitively on the extraction current and frequency, and have optimized values at the frequency of 0.5 Hz and current density of 0.5 mA cm−2 in raw solution with Li+/Na+/Mg2+ ion ratio of 1:1:1. More importantly, with the same average current, current profile with a decrease trend leads to higher lithium production, purity and lower energy consumption. Through simulation on dynamic ion diffusion, we demonstrate the current with decreasing trend reduces the concentration polarization of Li+ near the electrode and induce better performance. At last, we prove the concentration polarization also exist and can be relieved by current manipulation in Li+ extraction from real sea water. These results offer guidance for current operation in practical applications of electrochemical lithium extraction.