Statistical analysis of the effect of the electrochemical treatment and the acid concentration on the leaching of NMC cathodes from spent Li-ion batteries

Electric mobility has sharply increased the demand for batteries, making a European priority their sustainability throughout their entire lifecycle. However, battery recycling still needs to be improved, since it relies on industrial processes that require high amounts of energy, are not selective and require chemical reagents such as concentrated acids and reducing agents. In this work, the effect of acid concentration and electrochemical treatment on the leaching of Li, Ni, Mn, Co from electric vehicle LiNixMnyCozO2 (NMC) batteries was studied at room temperature. A factorial 32 experimental design was considered to deconvolve the effect of the chemical leaching from the electrochemical treatment in NMC batteries. An analysis of the variance was performed to determine which factors have a statistically significant effect on the initial leaching rate and the final leaching yield of each one of the metals. The main advantage and novelty of this work is that the combination of the electrochemical treatment and the acid concentration is proved to be significant for the extraction yield of the metals contained in Li-ion batteries of NMC cathode. All the experiments have been done in galvanostatic mode, with no pre-treatments and at room temperature with no addition of reducing agents. Based on the results obtained from the statistical analysis, a novel environmentally friendly process for recycling the cathodes of spent batteries was proposed. This 3-sequencial-step process would allow to recover separately the Al foil, the Li fraction, the Mn fraction, and the Ni-Co fractions. [Display omitted] •The leaching of spent Li-ion batteries has been statistically analyzed using ANOVA.•The effects of acid concentration and electrochemical treatment have been studied.•Li selective leaching (>90%) is achieved by anodic treatment in neutral electrolyte.•Ni-Mn-Co reductive leaching is achieved by cathodic treatment in mildly acidic media.•A room-temperature green recycling process is proposed.