Advances in the application of an early and selective recovery of lithium from spent lithium-ion batteries via hydrometallurgical methods

Licentiate thesis, 2023

In 2020 alone, the use of electric vehicles (EVs) contributed to more than 50 Mt CO2-eq of savings in GHG emissions globally. Given their performance in terms of energy and power density, Lithium-ion batteries (LiBs) are the technology of choice for the success of rapid EV growth. The demand for elements such as cobalt, nickel, copper, and lithium has increased widely. The concern regarding the availability of lithium is growing, and countries are rushing to establish policies to ensure a stable supply of critical minerals for EV battery supply chains. Lithium was added to a list of critical raw materials in 2020, and new regulations are pushing towards the recycling of more materials. The recovery target for lithium is set at 70% by 2030.
Current recycling systems do not have a high lithium recovery rate. Pyrometallurgy does not allow its recycling, while the current hydrometallurgy processes exhibit lithium losses. Traditional flowcharts are very complex. Usually disregarded, there has not been a major push to develop a recycling process centred around lithium. New recycling strategies are trying to lift its importance by recovering lithium in the first step. Early selective and more efficient recovery of lithium from spent lithium-ion batteries is the main objective of the research. The focus of this study was the investigation of early and complete lithium recovery. Two promising methods are considered: acombination of a thermal treatment followed by water leaching and a full hydrometallurgical route involving the use of oxalic acid as a leaching agent. The experiments were carried out using real LiB waste.
The use of thermal treatment on spent batteries presents many advantages. It allows for safer handling of the battery cell and the reduction of waste volume. Moreover, the metal oxides undergo a reduction forming more leachable species. At the same time, the reaction between lithium dioxide and carbon dioxide form lithium carbonate, a water-soluble species. The highest lithium recovery (62%) is achieved after pyrolysis at 700°C for 1h and water leaching at 25°C for 1h with a solid-to-liquid ratio of 20 g/L. Aluminium is the only co-dissolved element. On the other hand, the use of oxalic acid led to a 98.8% leaching yield for lithium, while less than 0.5 % of cobalt and nickel, and 1.5% of manganese were leached when applying leaching at 60°C, 1h, 0.6 M oxalic acid. Moreover, aluminium is completely leached, which is one of the novel findings in this field. Nickel, cobalt, and manganese oxalates are insoluble and remain in the solid residue, while lithium oxalate is dissolved in the solution.