(545k) Selective Lithium Recovery from Brine Using Li1-XNi0.5Mn1.5O4 /Ag Battery System

Lithium shortage is inevitable given the massive growth on its demand for use in electric vehicles (EVs) and various technologies. Consequently, recovery of lithium (Li) from other sources such as seawater, brine, and Li containing wastewater has been recently gaining attention in energy related fields. Discussions are directed towards exploitation of these aqueous sources to potentially alleviate the impending Li supply shortage. Yet, the most promising aqueous source for economical Li extraction are brine-like solutions. However, the challenge is to find an environmentally benign and more energy-efficient processes with fast Li⁺production rate for sustainable Li⁺ supply. Electrochemical Li recovery from aqueous solutions is an attractive method as it provides fast recovery rate. However, several studies on this process are challenged with the stability of the materials in aqueous environment and large amount of energy needed entailing high production cost. Until recently, electrochemical related Li extraction has yet to realize its feasibility for industrial-scale application. The success of electrochemical method relies on utilizing highly effective electrodes that can selectively capture Li⁺ at a fast rate and at a competitive uptake capacity with minimal energy requirement.

In this study, LiNi_0.5Mn_1.5O₄ (LNMO) was investigated for its feasibility as a selective Li⁺ capturing electrode for electrochemical Li recovery in brine solution. The LNMO is paired with Ag as a chloride capturing counter electrode. LNMO was first oxidized (delithiated) to facilitate its Li preference during capture phase. By applying a negative current, the delithiated Li_1-xNi_0.5Mn_1.5O₄ or (NMO) paired with Ag (NMO/Ag) was able to capture Li⁺ (i.e. discharge mode). The electrochemical system was proved to be stable in aqueous environment. The captured ions were then released by reversal of the polarity of the current (charging) in a separate cell containing a recovery electrolyte solution. The operating conditions were optimized through response surface methodology utilizing the central composite design. The determined optimum conditions were used for the repetitive Li capture-release process. Cycling (discharge-charge) experiments and cyclic voltammetry showed high selectivity and stability of the electrode in the presence of other competing cations (Na⁺, K⁺, Ca²⁺, Mg²⁺). Overall, the results demonstrate the feasibility of the electrochemical system (NMO/Ag) for high-throughput selective Li⁺ mining process with low energy requirement.

This research was supported by the National Research Foundation of Korea (NRF) under the Ministry of Science and ICT (No. 2017R1A2B2002109) and the Ministry of Education (No. 22A20130012051(BK21Plus).