Highly selective and efficient lithium extraction from brines by constructing a novel multiple-crack-porous LiFePO4/FePO4 electrode

Abstract

The rapid development of new energy vehicles stimulates the demand for lithium, and lithium extraction from brine has attracted much attention. Unfortunately, brines have high impurity content, high viscosity, and high mineralization, while conventional electrodes are highly hydrophobic, which makes brine mass transfer difficult. Herein, a novel electrochemical deintercalation/intercalation system (EDIs) with high hydrophilicity and permeability is constructed. The new system first introduces hydroxyl-rich PEG into PVDF by blending to modify the electrode hydrophilicity. Moreover, NaCl and carbon fibers are used as porogenic and structural reinforcing agents to increase channels for brine mass transfer and strengthen the electrode, respectively. The formed multiple-crack-porous microstructures electrode exhibits excellent hydrophilicity, the contact angle of the electrode decreases from 124° to 82.3°. Compared with the unmodified electrode, the lithium extraction speed increases nearly three times, and the current efficiency increases from 62 % to 92 %. Moreover, an industrial-scale EDIs is designed, and the capacity of the LiFePO4 is maintained at about 27 mg (Li) g−1 (LiFePO4) with the coulombic efficiency of 98.5 % over 1000 cycles at a high current density of 30 A m−2. The proposed pseudo-3D structured electrode with hydrophilic properties has broad application potential for lithium extraction from salt laker brine.