Combined pyro-hydrometallurgical technology for recovering valuable metal elements from spent lithium-ion batteries: a review of recent developments

Lithium-ion batteries (LIBs) are widely used in the mobile electronics, power, energy storage and other fields due to their excellent electrochemical performance, but their limited service life has resulted in a large number of spent LIBs being discarded. Due to the advantages of high recovery efficiency and mild reaction conditions, the combined pyro-hydrometallurgical process for recovering valuable metal elements from spent LIBs is emerging in line with the principles of green chemistry and has potential for large-scale industrial applications. Here we review current developments in the combined recovery process, aiming to figure out the challenges and future directions for the combined process. In detail, thermal pretreatment methods for collecting the cathode material from spent LIBs, the combined recovery process for treating the cathode material, and the subsequent separation and extraction process are summarized. Furthermore, the practical application of combined recycling schemes is demonstrated. Finally, the development and challenges of the combined process in recycling spent LIBs are revealed. Achieving pollution-free emissions and high-value utilization of spent LIB resources with low-cost treatment are future directions for the combined process.