Recycling and direct regeneration of valuable cathode materials from spent Li-ion batteries: a comprehensive review

The rapid growth and widespread use of lithium-ion batteries (LIBs) in electric vehicles (EVs), energy storage systems, and portable devices have raised significant concerns regarding the availability of valuable metals and environmental pollution. Currently, the lifespan of most LIBs is about 5-8 years. Recycling spent LIBs will not only address the shortages of limited natural resources but also alleviate environmental problems. Conventional hydrometallurgical and pyrometallurgical recycling methods, as well as direct regeneration strategies, have been extensively studied for spent LIBs, particularly for the cathode materials. Direct regeneration of spent cathode materials is considered an ideal recycling strategy due to its low energy consumption and environmental friendliness. This review systematically analyzes the advantages/disadvantages, application scenarios, and degradation mechanisms of several dominant cathode materials. It also examines the pros and cons of different recycling and regeneration methods, including pyrometallurgical, hydrometallurgical, and direct regeneration techniques. Furthermore, it evaluates the time, efficiency, economic, and environmental aspects of these recycling and regeneration strategies. Finally, the review identifies the existing challenges of current direct recycling methods and proposes potential solutions for large-scale industrialization.