Complete and selective recovery of lithium from EV lithium-ion batteries: Modeling and optimization using oxalic acid as a leaching agent

The necessity of a feasible process for the recycling of lithium-ion batteries is nowadays evident due to the significant demand for raw materials for battery production, but also due to legislative requirements to achieve certain recycling efficiency with sufficient quality of the products. Special conditions to achieve high lithium recovery and its use in new batteries represent a challenge for a commercial hydrometallurgical approach. In this work, an early selective recovery of lithium using oxalic acid as a leaching agent is investigated. The different solubility of transition metals oxalates in comparison to lithium oxalate was the main driving force to achieve selective separation in the leaching step. Nickel, cobalt, and manganese oxalates are insoluble and remained in the solid residue, while lithium oxalate was dissolved in the solution. Using a design of experiments to optimize the operation, optimal parameters were identified as 60 °C, 60 min, 0.6 M oxalic acid, resulting in 98.8% leaching yield for lithium, while less than 0.5 % of cobalt and nickel, and 1.5% of manganese were leached. This can significantly improve the lithium recovery in the current recycling processes. Moreover, aluminum was completely dissolved, which is a phenomenon not reported previously. It would constitute an advantage to the subsequent recycling operations.