The proliferation of lithium-ion batteries (LIBs) over the past decade has revolutionized the way we power our modern devices, from electric vehicles to smartphones. These batteries offer a combination of long life, high energy and power density, and significant cost reductions. However, this widespread adoption of LIBs has led to a pressing concern – the substantial increase in the production of spent LIBs in the coming years. It is projected that by 2035, there will be between 1.38 to 6.76 million tons of spent batteries. This influx of spent batteries poses serious environmental and health risks due to the presence of hazardous organics and heavy metals. Recovering valuable metals from spent LIBs not only addresses these environmental concerns but also taps into a significant secondary supply of rare metals, as the metal content in spent LIBs surpasses that of naturally occurring minerals and ores. Among the various methods available for metal recovery, hydrometallurgical processes have emerged as a promising alternative to traditional pyrometallurgical methods, which consume substantial energy and produce harmful gas pollutants. The key steps in hydrometallurgy include leaching, separation, and regeneration. Leaching, in particular, is a crucial step in the recovery process. Traditionally, inorganic acids such as hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), and phosphoric acid (H3PO4) have been employed as leaching agents. However, the use of inorganic acids often leads to secondary pollution, including toxic gas emissions and wastewater production. In contrast, organic acids have gained attention as an environmentally friendly and cost-effective alternative for leaching due to their chelating and complexing properties, as well as their ability to be recycled.
In this context, a recent study led by Associate Professor Shun Yang and his team from the School of Chemistry and Materials Science at Jiangsu Normal University introduces a novel approach to recovering valuable metals from spent lithium cobalt oxide (LiCoO2) batteries using polydopamine-coated magnetic nanoparticles (Fe3O4@PDA) in conjunction with citric acid as the leaching agent. The research work is published in Journal of ACS Sustainable Chemistry and Engineering.
The authors begin by extracting spent LiCoO2 powder from discarded batteries, which is then subjected to a pretreatment process involving discharging, dismantling, and stripping. The determined the metal content of the spent LiCoO2 powder. They synthesized and characterized polydopamine (PDA) nanoparticles, demonstrating their redox activity, which is vital for the subsequent leaching process. The redox activity of PDA is found to significantly enhance the leaching efficiency of Li and Co from spent LiCoO2 powder. To improve the reusability and recyclability of PDA, they coated onto magnetic nanoparticles (Fe3O4) via auto-oxidation polymerization, resulting in Fe3O4@PDA. This hybrid material not only serves as a reductant for metal recovery but also possesses magnetic properties, allowing for easy separation and recycling.
The authors explored various factors influencing the leaching efficiency, including pulp density, reaction time, temperature, and the ratio of cathode powder to Fe3O4@PDA. Notable findings including pulp density and found that increasing pulp density enhances leaching efficiencies, but excessively high pulp density leads to reduced efficiency due to uneven distribution. They also reported that higher temperatures promote leaching, but a point of diminishing returns is observed beyond 80°C. Moreover, longer reaction times lead to increased leaching efficiencies, with the optimal time identified as 300 minutes. Furthermore, higher Fe3O4@PDA dosage improved leaching efficiency, with the optimal ratio of cathode powder to Fe3O4@PDA determined as 1:4. The study also highlights the recyclability and renewability of Fe3O4@PDA, showcasing its ability to maintain high leaching efficiency over multiple cycles. The economic benefits of Fe3O4@PDA are underlined through cost comparisons with traditional leaching agents like hydrogen peroxide (H2O2).
The innovative approach presented by Professor Shun Yang and colleagues holds significant promise for the sustainable recovery of valuable metals from spent lithium-ion batteries. By leveraging polydopamine-coated magnetic nanoparticles (Fe3O4@PDA) as a recyclable and reusable reductant in conjunction with citric acid, the research demonstrates highly efficient metal recovery from spent LiCoO2 batteries. This environmentally friendly and economically viable method not only addresses the growing issue of electronic waste but also contributes to the circular economy by recycling valuable metals. The findings of this study pave the way for further research and development in green leaching processes for spent lithium-ion batteries, offering a more sustainable path for the future of energy storage and electronic devices.
Xuhui Zhu, Siyuan Luo, Mengqi Gong, Ran Mo, Yang Li, Shun Yang. Recyclable and Reusable Fe3O4@Polydopamine for Valuable Metal Recovery from Spent Lithium-Ion Batteries. ACS Sustainable Chem. Eng. 2023, 11, 5045−5054