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

Aluminum-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 AIBs battery performance, traditional redox strategies have the drawback of introducing defects and functional groups. In this work, graphite nanosheets exfoliated by supercritical carbon dioxide for high-performance aluminum-ion battery cathodes exfoliated by supercritical carbon dioxide (GNS-20) was firstly explored for AIB cathodes. Electrochemical tests show that the specific capacity of GNS-20 for AIB cathode was 152 mAh g−1 at a current density of 4 A g−1 during 1000 cycles, which was 1.9 times higher than that of natural graphite (NG) and 1.47 times higher than that of defect-rich reduced graphene oxide (rGO). 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 69.7% at 10 MPa, corresponding to capacities of 117 and 99 mAh g−1 (4 A g−1), respectively. This approach simplifies the process and aligns with environmental principles, offering significant potential for various graphite nanosheets applications.