Olivine-FePO4 preparation for lithium extraction from brines via Electrochemical De-intercalation/Intercalation method

Electrochemical De-intercalation/Intercalation system (EDIs) has attached much attention for lithium extraction from brines. However, the preparation of the matched olivine-FePO4 cathodes faced various problems. Herein, a simple and efficient method by using sodium persulfate for the preparation of olivine-FePO4 was proposed, and the optimal operation conditions (30–40 °C, 0.05–0.10 M Na2S2O8, and 1.5–2 h) was obtained. Furthermore, the relationship between the open-circuit voltage and solution redox potential with the de-lithiation rate was determined, and the value of the solution redox potential can be used for the online monitoring of the preparation of FePO4 electrode. Additionally, the prepared FePO4 electrode exhibited good selectively and cycle performance for lithium extraction. Using it as cathode to extract lithium from West Taijinar brine, the Mg/Li ratio decreased from 54.27 in the brine to 1.65 in obtained anolyte, and the recovery rate of Li+ in brine reached 85.30%. Besides, the average current density of the extraction process reaches 15.65 and 13.11 A·m−2 respectively. In summary, this electrode preparation method has been introduced to be of high preparation efficiency and easy to control, which would be more suitable for industrial applications.