Highly Efficient Lithium Extraction from Brine with a High Sodium Content by Adsorption-Coupled Electrochemical Technology

The demand for lithium resources continues to increase due to the rapid development of electronic vehicles, energy storage equipment, and other electronic products. Extracting lithium from salt lake brines is of great significance because of the predominance of brine lithium resources. Because both sodium and lithium ions are monovalent cations and have similar chemical properties, it is difficult to extract lithium from high-sodium brine. Herein, an adsorption-coupled electrochemical (ACEC) technology was utilized for lithium extraction. Manganese oxide coated with an ultrathin (1–2 nm) carbon layer (core@shell MnOx@C), obtained by a precursor method, is utilized as a membrane electrode in a membrane capacitive device. The crystal structure and carbon layer thickness of MnOx@C are effectively controlled by adjusting the preparation conditions. When the core is mainly a MnO phase, the lithium extraction capability of the membrane electrode is significantly improved. The lithium adsorption capacity reaches as high as 51.8 mg/g, and the adsorption time is 550 s from high-sodium brine (Na/Li ratio = 48.6). The desorption rate of lithium ions is 91.3% during a reverse process. Compared with either membrane capacitance or adsorption methods, the adsorption capacity reached with this technology is in the lead. The synergy of adsorption and Faradaic redox reactions leads to remarkably enhanced lithium extraction capability. This ACEC technology provides an alternative pathway to extract lithium from brines with high efficiency and facile operation.