One-step selective separation and efficient recovery of valuable metals from mixed spent lithium batteries in the phosphoric acid system

The recovery of valuable elements in spent lithium-ion batteries (LIBs) has attracted more and more attention. Efficient recovery of valuable elements from spent LIBs with lower consumption and shorter process is the target that people have been pursuing. In this study, the valuable metals (Ni, Co, Mn and Li) and FePO4 products are simultaneously recovered from mixed spent LiNixCoyMnzO2 and LiFePO4 in one step under the optimized condition of 0.88 M H3PO4, a mass ratio of LFP/NCM of 2:1, a L/S ratio of 33:1 and 80 celcius for 120 min without additional auxiliary reagents. Over 60 % of acid consumption is reduced and the process of adjusting pH is avoidable. The leaching efficiencies of the valuable elements reach up to 99.1 % for Ni, 98.9 % for Co, 99.6 % for Li and 97.3 % for Mn. Almost all of Fe is precipitated as FePO4Greek ano teleia2H2O. By means of the empirical model, the research on leaching kinetics demonstrates that the leaching reaction is internal diffusion-controlled with the apparent activation energy of valuable metals less than 30 kJ/mol. Furthermore, the redox reaction mechanism between spent LiBs has been explored. And the intrinsic driving force in the phosphoric acid system is found out. This finding may provide an innovative and selective recycling method for valuable elements from mixed spent LIBs with high economic benefit and fewer environmental footprints.

Automated summary

This study presents a one-step process for the simultaneous recovery of valuable metals (Ni, Co, Mn, and Li) and FePO4 from mixed spent LiNixCoyMnzO2 and LiFePO4. The optimized conditions reduce acid consumption and eliminate the need for pH adjustment. The leaching efficiencies of the valuable elements are high, and Fe is precipitated as FePO4Greek ano teleia2H2O. The leaching reaction is found to be internal diffusion-controlled, with a low apparent activation energy for valuable metals.