Graphite nanosheets exfoliated by supercritical carbon dioxide for high-performance aluminum-ion battery cathodes

Aluminium-ion batteries (AIBs), using commercial graphite as cathodes, stand out as promising secondary energy-storage devices for industrial application. While exfoliating graphite to graphite nanosheets holds substantial theoretical potential for significantly enhancing AIB performance, traditional redox strategies have the drawback of introducing defects and functional groups. In this work, graphite nanosheets exfoliated by supercritical carbon dioxide (GNS-20) were explored for high-performance AIB cathodes. Electrochemical tests showed that the specific capacity of GNS-20 for an AIB cathode was 152 mAh/g at a current density of 4 A/g during 1000 cycles, which was 1.9 times higher than that of natural graphite and 1.47 times higher than that of defect-rich reduced graphene oxide. Further, the regulation of the interlayer pore structure of GNS-20 proved instrumental in enhancing its AIB performance. Modulating the porosity of graphite nanosheets by adjusting the exfoliation pressure had a significant impact. The porosity of graphite nanosheets at an exfoliation pressure of 20 MPa was 86.7%, while the porosity at 15 MPa was 71.5% and that at 10 MPa was 69.7%, the latter two corresponding to capacities of 117 and 99 mAh/g (4 A/g), respectively. This approach simplifies the process and aligns with environmental principles, offering significant potential for various graphite nanosheet applications.