Lithium extraction from high Mg/Li ratio brine is a key technical problem in the world. Based on the principle of rocking‐chair lithium‐ion batteries, cathode material LiFePO 4 is applied to extract lithium from brine, and a novel lithium‐ion battery system of LiFePO 4 | NaCl solution | anion‐exchange membrane | brine | FePO 4 is constructed. In this method, Li + is selectively absorbed from the brine by FePO 4 (Li + + e + FePO 4 = LiFePO 4 ); meanwhile, Li + is desorbed from LiFePO 4 (LiFePO 4 − e = Li + + FePO 4 ) and enriched efficiently. To treat a raw brine solution, the Mg/Li ratio decreases from the initial 134.4 in the brine to 1.2 in the obtained anolyte and 83% lithium is extracted. For the treatment of an old brine solution, the Mg/Li ratio decreases from the initial 48.4 in the brine to 0.5 and the concentration of lithium in the anolyte is accumulated about six times (from the initial 0.51 g L −1 in the brine to 3.2 g L −1 in the anolyte), with the absorption capacity of about 25 mg (Li) g (LiFePO 4 ) −1 . Additionally, it displays a great perspective on the application in light of its high selectively, good cycling performance, effective lithium enrichment, environmental friendliness, low cost, and avoidance of poisonous organic reagents and harmful acid or oxidant.

Recycling of lithium and others metals from lithium-ion battery scraps are significant to prevent resource depletion and environmental protection. In this study, slurry electrolysis was employed for the recovery of lithium and manganese from the scrap LiMn 2 O 4 without addition of the chemical reductant or oxidant. The effect of electric current density, acid concentration, pulp density, and MnSO 4 concentration on Li and Mn leaching efficiency and electrode current efficiency was investigated. More than 99 and 92% of Li and Mn were leached at 363 K, and the current efficiency of the cathode and anode can reach 77 and 62%, respectively. Phase analysis indicated that pure MnO 2 was deposited in 1.0 mol/L H 2 SO 4 , and LiMn 2 O 4 cannot be leached into Mn 2+ directly. The leaching of Mn 2+ from scrap LiMn 2 O 4 involves the steps of Li leaching and MnO 2 leaching. Finally, a closed-loop process was proposed for the recovery of high purity of Li 2 CO 3 (99.59 wt %) and MnO 2 (92.33 wt %) from scrap LiMn 2 O 4 . This process is economically feasible, environmentally friendly, and has great potential for the recovery of other scrap cathode metals.

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The preparation of Li2CO3 from brine with a high mass ratio of Mg/Li is a worldwide technology problem. Membrane separation is considered as a green and efficient method. In this paper, a comprehensive Li2CO3 preparation process, which involves electrochemical intercalation-deintercalation, nanofiltration, reverse osmosis, evaporation, and precipitation, was constructed. Concretely, the electrochemical intercalation-deintercalation method shows excellent separation performance of lithium and magnesium, and the mass ratio of Mg/Li decreased from the initial 58.5 in the brine to 0.93 in the obtained lithium-containing anolyte. Subsequently, the purification and concentration are performed based on nanofiltration and reverse osmosis technologies, which remove mass magnesium and enrich lithium, respectively. After further evaporation and purification, industrial-grade Li2CO3 can be prepared directly. The direct recovery of lithium from the high Mg/Li brine to the production of Li2CO3 can reach 68.7%, considering that most of the solutions are cycled in the system, the total recovery of lithium will be greater than 85%. In general, this new integrated lithium extraction system provides a new perspective for preparing lithium carbonate from high Mg/Li brine.