Selective lithium extraction from natural brine with high Na/Li and Mg/Li ratios using a polyporous LiMn0.5Fe0.5PO4/C electrode

The electrochemical method exhibits exceptional potential for lithium extraction due to its environmental friendliness and superior efficiency. However, the questionable suitability of existing electrodes critically restricted the development of this technology. Herein, a highly selective LiMn0.5Fe0.5PO4/C (LMFP/C) polyporous electrode was developed for precisely extracting lithium from natural brine with High Na/Li and Mg/Li Ratios. Through a rocking-chair electrochemical process, the adsorption capacity of the electrode reached 24.1 mg g−1 and retained 97.3 % capacity after 40 cycles for artificial brine with 0.2 g L−1 Li+ ions. For the natural old brine (containing 66.3 g L−1 Mg2+ with 100.5 Mg/Li mass ratio), the Li[sbnd]Mg separation coefficients reached 805.2, respectively, accompanied by 9.36 mg g−1 and 11.8 mg g−1 average adsorption capacity. The electrode exhibited strong selectivity and a robust adsorption rate for Li+ ions, primarily due to its remarkable diffusion-control characteristic and abundant nanoporous channels. The density functional theory (DFT) calculations revealed that the LMFP crystal exhibited the strongest binding energy with Li+ ions, which further validated the selectivity mechanism of the LMFP/C electrode. Whereafter, an electrically-driven “extraction-multistage purification” device was developed to simultaneously achieve the separation and enrichment of Li+ ions. The Li+ concentration was enriched from 0.20 g L−1 to 1.07 g L−1, with a surprising Li[sbnd]Mg separation coefficient of 3030.3. The polyporous LMFP/C electrode featured outstanding performance and offered unique superiority in lithium extraction from salt lakes. © 2025 Elsevier B.V.