Pyrometallurgical recycling of spent lithium-ion batteries from conventional roasting to synergistic pyrolysis with organic wastes

The synergistic pyrolysis has been increasingly used for recycling spent lithium-ion batteries (LIBs) and organic wastes (hydrogen and carbon sources), which are in-situ transformed into various reducing agents such as H2, CO, and char via carbothermal and/or gas thermal reduction. Compared with the conventional roasting methods, this “killing two birds with one stone” strategy can not only reduce the cost and energy consumption, but also realize the valorization of organic wastes. This paper concluded the research progress in synergistic pyrolysis recycling of spent LIBs and organic wastes. On the one hand, valued metals such as Li, Co, Ni, and Mn can be recovered through the pyrolysis of the cathode materials with inherent organic materials (e.g., separator, electrolyte) or graphite anode. During the pyrolysis process, the organic materials are decomposed into char and gases (e.g., CO, H2, and CH4) as reducing agents, while the cathode material is decomposed and then converted into Li2CO3 and low-valent transition metals or their oxides via in-situ thermal reduction. The formed Li2CO3 can be easily recovered by the water leaching process, while the formed transition metals or their oxides (e.g., Co, CoO, Ni, MnO, etc.) can be recovered by the reductant-free acid leaching or magnetic separation process. On the other hand, organic wastes (e.g., biomass, plastics, etc.) as abundant hydrogen and carbon sources can be converted into gas (e.g., H2, CO, etc.) and char via pyrolysis. The cathode materials are decomposed and subsequently reduced by the pyrolysis gas and char. In addition, the pyrolysis oil and gas can be upgraded by catalytic reforming with the active metals derived from cathode material. Finally, great challenges are proposed to promote this promising technology in the industrial applications.