Upcycling of spent LiCoO2/Graphite/Cu mixtures: Cu-doping with contrary gradient distribution towards high-rate and prolonged-cyclability

Abstract

Attracted by remarkable environmental/economic advantages, the direct regeneration of spent LiCoO₂ (LCO) has been regarded as potential recycling method. However, limited by small-size and various designing-models, spent batteries are always industrially dismantled to obtain complex mixture, containing LCO, graphite, Cu-impurities, etc. Thus, exploring the synergetic effect of graphite removing and Cu-doping behaviors/threshold is crucial for the practical commercial production about spent mixture. Herein, spent mixtures are utilized to regenerate high-voltage LCO. Assisted by graphite self-heating and Li-vacancies, the doping-temperature and diffusion energy-barrier are lowering, facilitating Cu-atoms doping into bulk-phase. After optimizing Cu-content (0.7 wt.%), bulk-oriented doping at Li/Co sites is achieved with contrary gradient Cu-atoms distribution. Unique doping behaviors induce the evolution of morphology/lattice stability and the expanding of interlayer spacing. The as-optimized sample delivers a high capacity of 177.59 mAh g^-1 at 0.2 C. Even at 5.0 C after 500 cycles, its capacity could reach up to 154.8 mAh g^-1 with ∼82.4% retention. Supporting by electronic structure analysis, unique doping behaviors served as important roles in enhancing electronic conductivity and lowering O 2p band center. Given this, the work is expected to offer significant guidance of direct commercial regeneration, and shed light on the clear Cu-doping behaviors with threshold-value.