Efficient lithium extraction from salt lakes brine via regulating the electric double-layer interface of high-loading film electrodes with CMCLi

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 (CMCLi) 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.