High-efficiency recycling of spent lithium-ion batteries: A double closed-loop process

Due to the scarcity of raw materials and negative environmental effects, it is essential to selectively recover lithium and other transition metals from end-of-life lithium-ion batteries (LIBs). Here, we propose a dual closed-loop process for resource utilization of spent LIBs. As an alternative to strong inorganic acids, deep eutectic solvents (DESs) as green solvents are employed for the recycling of spent LIBs. The DES based on oxalic acid (OA) and choline chloride (ChCl) achieves efficient leaching of valued metals within a short time. Through the coordination adjustment of water, it can form high-value battery precursors directly in DES, changing wastes into valuables. Meanwhile, water as a diluent can achieve the selective separation of lithium ions via filtration. More importantly, DES can be perfectly re-generated and recycled many times, indicating that the process is cost-effective and eco-friendly. As experimental proof, the re-generated precursors were used to produce new Li(Ni_0.5Co_0.2Mn_0.3)O₂ (NCM523) button batteries. The constant current charge-discharge test revealed that the initial charge and discharge values of the re-generated cells were 177.1 and 149.5 mAh/g, respectively, corresponding to the performance of commercial NCM523 cells. The whole recycling process is clean, efficient, and environment-friendly, realizing the double closed loop of spent battery regeneration and deep eutectic solvent re-use. This fruitful research demonstrates DES has excellent potential for recycling spent LIBs and provides an efficient and eco-friendly double closed-loop solution for the sustainable re-generation of spent LIBs.