A review of cathode and electrolyte recovery from spent lithium-ion batteries: Recent technologies, processes and policies

Recently, lithium-ion batteries (LIBs), due to their superior performance, have been vastly applied in electronic, auto, and other industries, resulting in the generation of an increasing amount of spent LIBs. What's worse, LIBs contained potentially toxic substances, including heavy metals, toxic and flammable electrolyte containing LiBF4, LiClO4, and LiPF6. Conventional disposal of spent LIBs via landfill or incineration exerts tremendous pressure on the environment. It was necessary to adopt efficient, low-cost, and environmentally friendly approaches to valorizing spent LIBs, which could not only alleviate the shortage of rare resources by recycling valuable elements such as Cu, Li, Mn, Ni, Co, and Al, but also eliminate the pollution of harmful components in batteries and realize the recycling and sustainable industry related to consumer electronics and electric vehicles (EVs). Given this, this paper summarized the recycling technologies of spent LIBs, including pyrometallurgy (melting reduction and roasting methods) and hydrometallurgy (leaching, precipitation, extraction, ion-exchange, electrochemical, sol-gel methods), and electrolyte recycling (organic solvent extraction and supercritical extraction methods). Pyrometallurgy technologies had relatively decent metal recovery rates but were associated with high energy consumption and atmospheric emission issues. Hydrometallurgical technologies were more environmentally friendly and efficient in recovering spent LIBs, although disposing of the wastewater generated from the process remained a challenge. In addition, the different industrial processes and various countries' related policies of recycling spent LIBs were investigated. In the end, the outlooks and future directions of recycling spent LIBs were proposed.