Optimization of the Selective Dissolution of Li from the Spent Li-ion Batteries using Oxalic Acid by a Response Surface Methodology

In this study, the recovery of lithium from the cathode of the spent Li-ion batteries of the LiNixMnyCozO2 type was investigated. After complete discharging and dismantling, the cathodic section was cut and its aluminum content was selectively dissolved in 2.5 M NaOH solution at room temperature for 2 hr. In the next step, selective dissolution of lithium by oxalic acid from the de-aluminized cathode material was investigated and optimized using the response surface methodology of the central composite design. The effect of three parameters of time (35-100 min), temperature (40-70 °C), and oxalic acid concentration (0.5-1.2 M) on the lithium recovery percentage and manganese concentration was studied as the response variables. According to the statistical analysis of the results and the developed models, an optimum condition (T = 70 °C, t = 122 min and oxalic acid concentration of 1.1 M) was suggested and verified experimentally, resulting in the lithium recovery of about 95% and Mn2+ concentration of about 110 mg/L.