Sustainable recovery and resynthesis of electroactive materials from spent Li-ion batteries to ensure material sustainability

Lithium-ion batteries (LIBs) are widely used as power storage systems for electronic devices and electric vehicles (EVs). The widespread usage and short lifespan of some Li-ion applications has led to a high rate of production of spent LIBs. Electrodes from spent LIBs can be recycled and resynthesised via different recycling techniques that are more cost-effective and environmentally sustainable than the production of electrodes from virgin materials. Various pyro and hydrometallurgical techniques are generally used to resynthesise electrode materials, and each has benefits and drawbacks. The concept of 'microrecycling' using selective thermal transformation can be used to recycle and resynthesise the electrodes of spent LIBs. Other than spent LIBs, Li-ion battery (LIB) electrodes can also be synthesised from materials recovered and from other waste sources, such as spent nickel-metal hydride (Ni-MH) and Zn-alkaline batteries, rubber tyres and biomass. This review article summarises recent work on recycling and resynthesis of electroactive materials from spent LIBs, as well as possible alternative waste streams which could be sources of valuable materials. The importance and environmental impact of spent LIBs recycling is also discussed briefly. Finally, the review addresses the economic viability of using microrecycling techniques to ensure the sustainable recycling of spent LIBs on a small scale. This review highlights the state-of-the-art recycling technologies of spent LIBs, providing invaluable thought to researchers for designing new and efficient recycling strategies which will lead to sustainable development of Li-ion batteries.