Bubbles to batteries: A review of froth flotation for sustainably recycling spent lithium-ion batteries

Lithium-ion batteries (LiBs) have been consumed exponentially due to the rapid growth of electric vehicles and electronics. Efficient recycling of spent LiBs is crucial for sustainability; however, major current technologies have disregarded froth flotation which has been recently introduced as an effective separation method and drawn extensive attention in the literature. The present review summarizes recent fundamental and applied progress on recycling spent LiBs using pretreatment methods followed by froth flotation. Flotation can potentially separate anode and cathode materials based on their surface wettability differences. However, the presence of organic binders reduces this wettability contrast. Thus, pretreatment methods like thermal processes, grinding, and chemical modification were critically reviewed from different perspectives to remove organic binders and enhance flotation efficiency. The article further discusses flotation reagents, physical and chemical pretreatment options, and environmental considerations for the LiBs recycling. Challenges regarding efficiency, scalability, and sustainability are highlighted. It was revealed that future research works should mainly focus on cleaner pretreatment methods, flotation optimization, and minimization of environmental impacts to advance battery recycling.