Wu, Xin, Zhong, Jie, Liu, Houji, Ren, Yuxi, Zhang, Haiquan, Liu, Zijing, and Wang, Ning
• Multi-electrode device for Li metal extraction from seawater is designed firstly. • Threshold voltage is decreased from 3.9 V to 2.3 V for Li 4 Ti 5 O 12 -based device. • New perfluorinated electrolyte exhibits high chemical stability to LTO and Li. • Extraction rate of the multi-electrode device reaches 175 μg cm−2 h−1 in seawater. Based on the large extraction efficiency of 10–200 μg cm−2 h−1, the electrolysis-based technology is one of the most promising methods for large-scale extraction of lithium resources from natural seawater. The high potential safety hazard is the inherent defect of the conventional two-electrode electrolytic cell because of the threshold voltage of 3.9 V, which is very close to the decomposition voltage of carbonate electrolytes (4.5–5.0 V). Herein, we designed a novel triple-electrode device, using spinel Li 4 Ti 5 O 12 and 1 M LiPF 6 /FEC + FEMC + HFE respectively as a temporary carrier for storing Li-ions and perfluorinated electrolyte. The threshold voltage of the multi-electrode device is lowered to 2.3 V, which expands the electrochemical window for lithium resource extraction from 1.1 V to 2.7 V. LTO electrode carrier is impossible to electrocatalyze the as-prepared fluoride electrolyte; the compound electrolyte is chemically stable to Li metal as well, avoiding the formation of lithium dendrites. Therefore, the Li 4 Ti 5 O 12 /Li battery exhibits outstanding cycle performances of 99.3% Coulombic efficiency and 95% capacity retention during 250 cycles. Multi-electrode electrochemical devices have shown high safety, stability and extraction efficiency in the practice of extracting Li metal from natural seawater, which is very beneficial to the development of marine mineral resources. [ABSTRACT FROM AUTHOR]