Nowadays, the recycling of spent lithium-ion batteries is a key concern in the energy fi eld. Among them, for the purifi cation

of Li-containing mother liquor, the targeted multi-means coupling impurity removal methods are mostly employed, which

however, inevitably lead to a Li loss of 3–5% and high costs. In this study, a multi-stage hydrolysis method, combining the

residual P and Al, Mg, Cu, Zn, Ni, Fe, forming hydroxide-phosphate co-precipitation for the synergistic impurity separation,

was adopted. Thermodynamic calculations show that Li + and Mg 2+ are insensitive to pH when pH < 10, and Al, Cu, Zn,

Ni, Fe behave similarly in nature. The impurities should be precipitated as: Fe 3+ > Al 3+ > Cu 2+ > Ni 2+ > Zn 2+ > Mg 2+ , with

phosphate precipitating fi rst, followed by converting into hydroxide as pH rising. Actual results showed that the order was

P > Fe & Al & Cu & Ni & Zn > Mg, and the process was divided into three steps, with separation points at pH = 2.37, 8.66,

and 11.00, respectively. All the impurity removal effi ciencies were close to 100%, the loss of Li was 1.74%. The optimal

conditions for Li 2 CO 3 precipitation were determined: an Na 2 CO 3 addition of 1.5 times the theoretical amount, a temperature

of 90 °C, a reaction time of 4 h, and a one-time addition of dosing method. Li precipitation effi ciency reaches 90.10%, with

a 99.95% purity. The results eff ectively reduced Li losses and provided a practically feasible basis for the industrial purifi cation

of Li-containing mother liquor.