Efficient lithium extraction from salt lakes brine via regulating the electric double-layer interface of high-loading film electrodes with CMC[sbnd]Li

Abstract

In response to the problems of large interfacial diffusion resistance and low lithium extraction efficiency in traditional high-loading film electrodes during lithium extraction from salt lakes by the electrochemical de-intercalation method, this paper presents an interfacial engineering strategy based on the carboxymethyl cellulose lithium (CMC[sbnd]Li) binder. By modulating the structure of the inner Helmholtz plane (IHP) of the electrical double layer and enlarging the effective specific surface area, the migration rate of Li⁺ and the lithium extraction efficiency are remarkably enhanced. In this study, a CMC-Li composite electrode sheet was prepared using Spent LiFePO₄ as the raw material. It was demonstrated that the carboxyl (-COOH) and hydroxyl (-OH) functional groups of CMC-Li can be directionally adsorbed on the electrode surface. This adsorption event reconstructs the IHP-layer structure, reduces the solvation energy barrier of Li⁺, and increases the effective specific surface area of the film electrode. As a result, the contact angle decreased from 130.01° to 55.17°. Furthermore, in the CMC-Li system, the lithium extraction rate in simulated brine increased from 0.33 mg·g⁻¹·min⁻¹ to 0.69 mg·g⁻¹·min⁻¹, while the energy consumption decreased by a factor of 3. In the West Taijinar brine, the lithium extraction capacity reached 23.01 mg·g⁻¹ with a concurrent dramatic reduction in the Mg/Li ratio from 141 to 0.42. These results indicate that the CMC-Li system exhibits excellent lithium extraction performance and high selectivity. Overall, this study proposes a groundbreaking interfacial design concept that achieves both high efficiency and sustainability for lithium extraction from salt lake brines.