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Abstract

Electrochemical methods using intercalation chemistry to extract Li from seawater using the TiO2-coated FePO4 electrode. The difference in the thermodynamic intercalation potentials, as well as the diffusion barriers between Li and Na, could provide near 100% selectivity towards Li interaction when Li/Na molar ratio is higher than 10-3. For lower Li/Na ratio as in the authentic seawater case, pulsed-rest and pulse-rest-reverse pulse-rest electrochemical methods were developed to lower the intercalation overpotential and it was proven to successfully boost the Li selectivity. Moreover, the pulse-rest-reverse pulse-rest method can also promote electrode crystal structure stability during the co-intercalation of Li and Na and prolong the lifetime of the electrode. Finally, 10 cycles of successful and stable Li extraction with 1:1 of Li to Na recovery from authentic seawater were demonstrated, which is equivalent to the selectivity of ˜1.8×104. Also, with lake water of higher initial Li/Na ratio of 1.6×10-3, Li extraction with more than 50:1 of Li to Na recovery was achieved.

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