Biochar-driven multi-stage pyrolysis-roasting-relithiation strategy enables energy-saving and green regeneration of spent LiCoO2 batteries

The rapid expansion of the lithium-ion battery (LIB) industry has resulted in the exponential growth of spent LIBs, underscoring the urgent requirement for the efficient recycling and utilization of spent LIBs. Traditional recycling methods of spent LIBs suffer from high energy and chemical reagent consumption, high pollutant emission, and limited economic viability. Herein, this work proposes a novel biochar-driven multi-stage pyrolysis–roasting–relithiation strategy to achieve energy-saving and green regeneration of spent LiCoO2 (LCO) cathodes. The results show that the introduction of pine sawdust char (PSC) into spent LCO greatly promotes the complete decomposition and reduction of spent LiCoO2 under relatively mild conditions. The subsequent roasting process is able to easily remove the impurities (such as residual PSC) in the pyrolysis products, achieving rather satisfactory recovery rates of Li (95.8%) and Co (99.5%) at optimal conditions during the whole multi-stage process. The sufficient removal of the impurities is beneficial for the final relithiation process, obtaining high-quality regenerated LCO with a well-ordered layered structure, uniform morphology, and freedom from agglomeration, which contributes to its electrochemical performance (170.79 mA h g−1 at 0.1 C) comparable to commercial LCO. Moreover, life cycle and techno-economic assessments indicate that the proposed strategy is an energy-efficient (10.75 MJ kg−1 regenerated LCO) and economical (9.78 $kg−1 regenerated LCO) regeneration route with minimal impact on the environment. This work paves the way for the economical and sustainable recovery technologies of spent LIBs.