Abstract
This study investigates the role of CaF2 in controlling phase separation during aluminothermic self propagating high temperature synthesis (SHS) of cathode material recovered from spent lithium ion batteries. The novelty of this work lies in evaluating the effect of CaF2 content on the formation and separation of metallic and slag phases and in identifying the optimal flux concentration for processing multicomponent cathode materials. The feedstock contained Ni, Co, Mn, and Li compounds. Aluminum was used as a reducing agent, while CaF2 was added as a flux at concentrations of 5, 10, 15, and 20 wt.%. After SHS, the products were separated into metallic and slag fractions and characterized by X ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). The addition of CaF2 promoted metallic phase formation and separation and contributed to the formation of an aluminate slag matrix. The metallic phase yield increased from 22.36% at 5 wt.% CaF2 to 30.10% and 30.26% at 10 and 15 wt.%, respectively. A further increase to 20 wt.% CaF2 reduced the metallic phase yield to 27.39%. XRD showed that LiAlO2 was the dominant phase in the slag, while SEM/EDS confirmed the formation of a metallic phase rich in Ni with smaller amounts of Co and Al. Overall, 10 to 15 wt.% CaF2 provided the most favorable conditions for phase separation under the studied SHS conditions.