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Electrochemical De-intercalation/Intercalation system (EDIs) has attached much attention for lithium extraction from brines. However, the preparation of the matched olivine-FePO 4 cathodes faced various problems. Herein, a simple and efficient method by using sodium persulfate for the preparation of olivine-FePO 4 was proposed, and the optimal operation conditions (30–40 °C, 0.05–0.10 M Na 2 S 2 O 8 , 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 FePO 4 electrode. Additionally, the prepared FePO 4 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. • Olivine-FePO 4 electrodes with excellent lithium extraction performance are prepared. • Solution redox potential can be used for online monitoring of the olivine-FePO 4 electrode preparation process. • The prepared olivine-FePO 4 electrode exhibits excellent cycling performance and ion selectivity. [ABSTRACT FROM AUTHOR]

Electrochemical De-intercalation/Intercalation system (EDIs) has attached much attention for lithium extraction from brines. However, the preparation of the matched olivine-FePO 4 cathodes faced various problems. Herein, a simple and efficient method by using sodium persulfate for the preparation of olivine-FePO 4 was proposed, and the optimal operation conditions (30–40 °C, 0.05–0.10 M Na 2 S 2 O 8 , 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 FePO 4 electrode. Additionally, the prepared FePO 4 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. • Olivine-FePO 4 electrodes with excellent lithium extraction performance are prepared. • Solution redox potential can be used for online monitoring of the olivine-FePO 4 electrode preparation process. • The prepared olivine-FePO 4 electrode exhibits excellent cycling performance and ion selectivity. [ABSTRACT FROM AUTHOR]

• A novel process is adopted to recovery of Li 2 CO 3 and FePO 4 /C from spent LiFePO 4. • Li in the spent LiFePO 4 can be extracted without any chemical reagent. • The recovered Li 2 CO 3 and FePO 4 /C can be used for resynthesized LiFePO 4. • The resynthesized LiFePO 4 meets the basic requirements for reuse. A simple, green and effective method, which combined lithium iron phosphate battery charging mechanism and slurry electrolysis process, is proposed for recycling spent lithium iron phosphate. Li and FePO 4 can be separation in anionic membrane slurry electrolysis without the addition of chemical reagent. The leaching efficiency of Li can reach to 98% and over 96% of Fe are recycled as FePO 4 /C. Kinetics analysis indicates that the surface chemical reaction is the control step during the slurry electrolysis. Additionally, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Electrochemical Impedance Spectroscopy (EIS) characterization and thermodynamic analysis are employed to investigate the leaching mechanism. It is found that the spent LiFePO 4 is delithiated and oxidized to FePO 4 by the function of e −, which is similar as the LiFePO 4 battery charging process. EIS analysis also verify the kinetics results, the charge transfer resistance controlled the leaching process. Finally, a novel process for recovery of spent LiFePO 4 is proposed. The recovered Li 2 CO 3 and FePO 4 /C can be used for resynthesize LiFePO 4 , and the resynthesized LiFePO 4 exhibits reversible capacities of 143.6 mAh g−1 at 1C and high current efficiency, stable cycle performances at 0.1 and 0.5C which meets the basic requirements for reuse. [ABSTRACT FROM AUTHOR]

[Display omitted] • LiMn 2 O 4 materials can selectively recover lithium from brine. • Porous electrode significantly reduces the lithium extraction time. • An anolyte with low Mg/Li ratio can be obtained. • The energy consumption of the system is only 8.74 Wh/mol. • Porous electrode has good cycling stability. Lithium extraction from brines with high Mg/Li mass ratio is a key technical issue to ensure sufficient lithium supply. In this work, porous LiMn 2 O 4 electrode was prepared to improve the lithium recovery rate and the electrode process kinetics of the LiMn 2 O 4 /Li 1-x Mn 2 O 4 (LMO) electrochemical system. Using the porous LiMn 2 O 4 electrode, the time required for lithium recovery was significantly reduced, and a solution with a low Mg/Li mass ratio was obtained. In addition, the energy consumption of the LMO electrochemical system was only 8.74 Wh⋅mol−1, and the electrode intercalation capacity remained essentially unchanged after 80 cycles at 17.20 mg⋅g(LiMn 2 O 4)−1. The application of porous electrodes in LMO electrochemical systems can efficiently and economically recover lithium from brines with high Mg/Li ratios. [ABSTRACT FROM AUTHOR]