Lithium recovery from brine by PEG-modified porous LiFePO4/FePO4 electrode system

•The degree of intercalation reaction within the electrode was explored.•The PEG-modified electrode shows a 28.4% increase in intercalation capacity.•The PEG-modified electrode shows a 38.8% increase in current efficiency.•The PEG-modified electrode has superior multiplication performance. Lithium recovery from high Mg/Li brine through the electrochemical intercalation /de-intercalation technology has attracted great attention due to its good selectivity. To obtain higher equipment capacity, the LiFePO4/FePO4 electrodes with higher coating density are applied for lithium extraction. Unfortunately, it also brings a problem of slow diffusion of Li+ within the electrode, which limits the intercalation rate of lithium. To solve the problem of Li+ diffusion, a PEG-modified porous LiFePO4 electrode was prepared for lithium recovery. After modification, a “microcracks-microporosity” composite structure appears on the electrode, and the agglomeration of electrode materials reduces due to the dispersing effect of PEG. Therefore, the diffusion resistance of Li+ within the electrode decreases, and the electrode polarization reduces. Using the PEG-modified porous LiFePO4/FePO4 system to recover lithium, the Li+ intercalation rate reaches 4.45 g(Li)·m−2·h−1, while that of unmodified electrode is only 2.10 g(Li)·m−2·h−1. Besides, the intercalation of Na+ was significantly reduced from 0.28 to 0.07 of Na/Fe ratio in FePO4 cathode, which means better selectivity and circularity. Therefore, the application of PEG-modified porous electrode systems can efficiently recover lithium from brines.