Selectively peeling of spent LiFePO4 cathode by destruction of crystal structure and binder matrix for efficient recycling of spent battery materials

Abstract

Impurity Fe could severely damage the performance of resynthesized cathode material, and therefore, LiFePO4 cathode should be removed from the mixed spent LIBs for materials recycling. In this research, a non-hydrometallurgy method has been developed to separate LiFePO4 by selectively peeling-off the LiFePO4 cathode material and the peeling-off process was well explained by theoretical modeling. The peeling-off efficiency of LiFePO4 was approximate 100 % and that of LiMn2O4/LiCoO2/Li(Ni, Co, Al)O2/Li(Ni, Mn, Co)O2 was only 0.08 %. That is, the separating selectivity was 1250. Mechanism study revealed that the peeling-off was achieved through selective destruction of the LiFePO4 crystal and the matrix of polyvinylidene fluoride (PVDF) binder. Particularly, the crystal structure of LiFePO4 was firstly destructed by sulfide, thus LiFePO4 particles were detached from the matrix of PVDF binder. Then, the PVDF binder without LiFePO4 particles filling were more susceptible to be brittlely peeled off by the micro-explosion force of hydrogen from the reaction of Al foil with water due to the weakened mechanical strength. The process is suitable for recycling varied types of spent LIBs, having a strong potential for industrial application.