Investigation of the Effects of Low-Temperature Thermal Treatment Applied to Graphite in Spent Lithium-Ion Anode Recycling

As the use of lithium-ion batteries (LIB) increases rapidly, recovery of graphite, the main component of the anode, from spent batteries has become important from environmental and economic perspectives. In this study, an acid leaching step followed by thermal treatment under partial atmosphere at a relatively low calcination temperature was investigated to recover graphite from spent lithium-ion batteries. The molecular and chemical structures of the recovered graphite in all spent anode samples were investigated using FTIR, ICP-MS, XRD, SEM–EDX and TEM–EDX. It was observed that organic impurities and volatile components were largely removed after acid leaching and thermal treatment at 750 °C. In addition, it was observed that graphite layers were rearranged and the distance between the layers decreased under the effect of thermal treatment. Partial atmosphere calcination at 750 °C can be considered as a feasible method for graphite recovery, offering energy efficiency and scalability. However, in an efficient calcination, it is necessary to maintain controlled oxygen levels to prevent excessive graphite loss and to perform preliminary acid leaching to reduce metal impurities. In order to best recycle graphite in waste lithium-ion anode recovery, a balance must be achieved between temperature, energy efficiency and material recovery. Considering this balance, a calcination temperature of 750 °C appears to be preferable for recycling.