Recovery of battery grade LiOH·H2O from spent LiFePO4 by using Li2SO4 causticizing process

LiFePO 4 battery is one of the three mainstream cathode materials for Lithium-ion batteries, with a market share of approximately 60%. With the rapid development of electric vehicles, plenty of spent LiFePO 4 batteries will inevitably accumulate, causing a waste of resources and environmental problems. Thus, spent LiFePO 4 recycling has become increasingly important. During the recovery process, mixing spent LiFePO 4 black powder and H 2 SO 4 resulted in a leaching solution containing complex compositions, such as Li, Fe, P, Co, Ni, Cu, Mg, Mn, and Al. The P and Fe elements are recovered through the FePO 4 precipitation. After solid-liquid separation, 5-6   g/L of Li and other accompanying impurities are retained in the mother liquor. The Li-bearing solution above is purified using the two-step precipitation method. Then, battery grade LiOH·H 2 O is successfully synthesized by using the Li 2 SO 4 causticizing process. The effects of operating parameters, including reaction temperature, excess coefficient of NaOH, Li concentration, and reaction time are investigated in detail. Under the optimal conditions, 96.18% of the Li in the initial concentrated Li 2 SO 4 solution is converted to LiOH solution by the reaction (Li 2 SO 4 + 2NaOH + 10H 2 O → 2LiOH + Na 2 SO 4 ·10H 2 O). Meanwhile, the Li content in Na 2 SO 4 ·10H 2 O can be controlled at around 0.2%, and the Li recovery rate for the process of Na 2 SO 4 by-product prepared by Na 2 SO 4 ·10H 2 O is as high as 98.30%. This study is expected to provide valuable insights into the high value-added recovery of Li from spent LIBs.