Efficient and sustainable recycling of spent Lithium-ion batteries using green solvents: A review

An enormous rise in the demand for lithium-ion batteries (LIBs) in the electronics and electric mobility sector has raised a global concern for the handling of millions of tons of spent LIBs. These batteries cannot be dumped to landfills due to environmental concerns nor can be burnt in air due to safety measures. Also, maintaining a regular supply of raw materials from limited resources is a big challenge for developing new LIBs. To bring sustainable development, there is a strong global need to recycle spent LIBs. While current recycling strategies are broadly classified as pyrometallurgical and hydrometallurgical routes, the fundamental role of solvents across different recycling stages remains largely overlooked. Solvents not only govern metal leaching but are equally important for electrolyte recovery, electrode delamination, binder removal, impurity separation, and material purification. This review presents a solvent-focused view on LIB recycling. By connecting solvent properties to recycling steps, this work offers a unified approach for sustainable, scalable LIB recycling technologies. Based on a multi-criteria sustainability assessment, DES based recycling emerge as a most balanced option achieving >95% metal leaching efficiency along with a reduced chemical use and wastewater generation. Supercritical/subcritical fluids and ionic liquids offer high efficiency but are limited by energy demand and cost, respectively, while emerging solvents (amphiphilic and supercooled systems) require further research and validation. Finally, emerging strategies for industrial implementation are discussed to outline future directions for solvent-driven battery recycling, with special emphasis on recent research and development efforts in India towards sustainable LIB recycling.