Flotation separation in lithium-ion battery recycling: Challenges and recent advances
Qing Sun, Kai Zeng, Jingsi Chen, Hongjian Zhang, Hongbo Zeng
Abstract
The rapid growth of electric vehicles, portable electronic devices, and stationary energy storage systems, coupled with the limited lifespan of lithium-ion batteries (LIBs), has led to a substantial increase in spent LIBs. In response to the urgent demand for resource recovery and environmental protection, the recycling of spent LIBs, particularly the separation of anode and cathode materials, which are the two most significant components, has become a critical area of research. Froth flotation offers a promising method by selectively separating particles based on differences in surface hydrophobicity, without altering the structure or chemical composition of the materials involved. The intrinsic hydrophobicity differences between anode and cathode materials (e.g., graphite and lithium metal oxides) make flotation an attractive technique for the recycling of spent LIBs. Hence, this review first outlines the fundamental principles of froth flotation, with particular emphasis on the roles of flotation agents-collectors, frothers, and dispersants-in modifying the surface hydrophobicity of various electrode materials. The interplay between flotation agents and the separation efficiency of anode and cathode components is examined in depth. However, several factors, such as the presence of organic binders and additives, residual lithium in the discharged anode, and surface degradation of electrode materials, may impede effective separation. Accordingly, this review further explores a range of pretreatment strategies designed to restore electrode surface properties and enhance flotation performance. This paper provides a comprehensive perspective of flotation-based separation in spent LIBs recycling, offering valuable insights and practical implications for advancing large-scale, efficient, and sustainable recovery technologies.