Direct recycling technologies of cathode in spent lithium-ion batteries

Lithium-ion battery (LIB)-based electric vehicles (EVs) are regarded as a critical technology for the decarbonization of transportation. The rising demand for EVs has triggered concerns on the supply risks of lithium and some transition metals such as cobalt and nickel needed for cathode manufacturing. There are also concerns about environmental damage from current recycling and disposal practices, as several spent LIBs are reaching the end of their life in the next few decades. Proper LIB end-of-life management can alleviate supply risks of critical materials while minimizing environmental pollution. Direct recycling, which aims at recovering active materials in the cathode and chemically upgrading said materials for new cathode manufacturing, is promising. Compared with pyrometallurgical and hydrometallurgical recycling, direct recycling has closed the material loop in cathode manufacturing via a shorter pathway and attracted attention over the past few years due to its economic and environmental competitiveness. This paper reviews current direct recycling technologies for the cathode, which is considered as the material with the highest economic value in LIBs. We structure this review in line with the direct recycling process sequence: cathode material collection, separation of cathode active materials from other components, and regeneration of degraded cathode active materials. Methods to harvest cathode active materials are well studied. Efforts are required to minimize fluoride emissions during complete separation of cathode active materials from binders and carbon. Regeneration for homogeneous cathode is achieved via solid-state or hydrothermal re-lithiation. However, the challenge of how to process different cathode chemistries together in direct recycling needs to be solved. Overall, the development of direct recycling provides the possibility to accelerate the sustainable recycling of spent LIBs from electric vehicles.