Key Takeaways & Executive Findings
- •• Achieved 95% selective lithium dissolution with minimal co-leaching of Ni, Co, and Mn (<1%) using a novel acid-free sulphation roasting process. • The process operates at a moderate temperature of 600°C with sodium bisulfate as a roasting reagent, offering a more sustainable alternative to traditional acid leaching. • Mechanistic insights reveal that roasting collapses the NCM layered structure, converting lithium to LiNaSO4 and transition metals to Ni6MnO8 and MnCo2O4, enabling selective extraction. • The method simplifies downstream purification, allowing direct production of Li2CO3 from the lithium-rich leach solution, potentially improving overall lithium recovery rates.
Abstract
With the dramatic accumulation of the end-of-life lithium-ion batteries, their recycling is attracting extensive attention worldwide. To address the problem of low lithium recovery in the current typical hydrometallurgy recovery process, this research uses sodium bisulfate as an auxiliary roasting reagent to extract lithium from spent lithium-ion batteries through sulphation roasting, which can enhance the lithium recovery rate significantly. A systematic study of the sulphation roasting process and the mechanisms was carried out with experiments, thermodynamic calculations, and characterization of the roasted sample phases. The results showed that at a roasting temperature of 600 °C, NaHSO4·H2O/spent LiNixCoyMnzO2 cathode powders (S-NCM) mass ratio of 1.2, and roasting time of 60 min, 95% selective dissolution of lithium was acquired, while the leaching rates of Ni, Co, and Mn were confined under 1%. During roasting, the NCM layered structure collapses and the lithium is transformed into the LiNaSO4 phase, while the transition metals transform into Ni6MnO8 and MnCo2O4 phases. The removal of impurity ions from the lithium-rich leaching solution and the generation of Li2CO3 were achieved by a combination of thermodynamic calculations and experiments.
1. Introduction
Over the past decade, the rapid development of portable electronic products and electric vehicles has ballooned the amounts of lithium-ion batteries (LIBs: LiMnO4, LiCoO2, LiNixCoyMn1−x−yO2, and LiFePO4) in use [1]. There has been a dramatic increase in the number of spent LIBs because of the limited life span of LIBs [2, 3]. LIBs comprise metals (5%−20% Co, 5%−10% Ni, and 5% of Li), 15% electrolyte, and 7% plastic, with compositions varying for different manufacturers [4, 5]. Inappropriate spent LIBs management poses a significant biological and environmental risk, while spent LIBs make up a valuable waste resource, with potentials for significant economic benefit by recovering the major components.
So far, there are many methods for recycling valuable metals from spent LIBs. Pyrometallurgical and hydrometallurgical processes are two main major categories based on the essential characteristics of these methods [6]. A typical pyrometallurgical process involves spent LIBs crushing, roasting, reduction of oxides, and refining and separating metals [7]. However, the pyrometallurgical process has many shortcomings, such as high energy consumption, low metal recovery rate, and difficulty in lithium recovery [8]. The hydrometallurgical process with higher metal recovery rates and lower energy consumption has been regarded as a promising spent LIBs recycling technology, in which the leaching process is one of the key steps [9, 10]. The inorganic acid leaching [11−14], organic acid leaching (e.g., citric, oxalic, or lactic acid, etc.) [15, 16], ammonia leaching [17], and bioleaching [18] are the key technologies to extract valuable metals from spent LIBs.
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ZHANG Kun, YANG Jian, JIANG Liang-xing, LAI Yan-qing, XU Kai-hua (2026). An acid-free process for the selective recovery of lithium from spent ternary lithium-ion batteries. Journal of Central South University. https://doi.org/10.1007/s11771-026-6187-4
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Frequently Asked Questions
What is the main advantage of the acid-free process for lithium recovery?
The acid-free process uses sodium bisulfate as a roasting reagent, achieving 95% selective lithium dissolution while limiting co-leaching of Ni, Co, and Mn to under 1%, thus simplifying downstream purification and improving overall lithium recovery.
What are the optimal conditions for the sulphation roasting process?
The optimal conditions are a roasting temperature of 600°C, a NaHSO4·H2O to spent cathode powder mass ratio of 1.2, and a roasting time of 60 minutes.
How does the process selectively extract lithium?
During roasting, the NCM layered structure collapses, converting lithium into a LiNaSO4 phase while transition metals form Ni6MnO8 and MnCo2O4 phases. This phase transformation allows selective dissolution of lithium in water, leaving transition metals in the solid residue.
What is the significance of this method compared to traditional hydrometallurgy?
Traditional hydrometallurgy often suffers from low lithium recovery (70-80%) due to complex separation steps. This acid-free method achieves higher selectivity and recovery, reduces acid consumption, and simplifies the process, making it more environmentally friendly and economically viable.
Can this process be scaled up for industrial application?
The process uses relatively mild conditions and common reagents, and the authors suggest it has potential for industrial application, though further scale-up studies are needed to assess economic and technical feasibility.
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