Application of purified kish flake graphite as a potential cathode material for high-performance aluminum ion batteries

The separation and purification of kish graphite is an important prerequisite for its high value and comprehensive utilization. The comprehensive separation process including water washing dust removal, magnetic separation and acid leaching purification can effectively enrich and purify kish flake graphite (KFG) from low-cost industrial by-product kish graphite. When the magnetic strength is 2000 Gauss, the purified KFG has suitable recovery (57.34%), high fixed carbon content (99.38%) and low ash content (0.62%). Compared with natural flake graphite, KFG has a highly ordered graphite microcrystalline layer structure with higher graphitization degree (99.77%) and well-developed micro/nanopore with larger specific surface area (4.12 m2·g−1). Such distinctive microstructure features ensure KFG to be applied as a cathode material for aluminum ion batteries (AIBs) to exhibit superior electrochemical behaviors. KFG exhibits a high reversible specific capacity (110.7 mAh/g at 50 mA/g), outstanding rate capability (56.9 and 26.6 mAh/g at high current densities of 1000 and 2000 mA/g) and superior long-term cycling stability (101.8 mAh/g with a Coulombic efficiency of 99.5% at 1000 mA/g after 2000 cycles). This study demonstrates a promising feasibility for mass production of KFG from industrial by-product kish graphite for high performance AIBs.