Ionic liquid-mediated ball milling synthesis of Fe2O3/IL-graphene nanocomposite for high performance and long cycle stability of supercapacitor

Abstract

A Fe 2 O 3 /ionic liquid-functionalized graphene nanocomposite (Fe 2 O 3 /IL-graphene) was synthesized through a facile one-step ionic liquid-assisted ball milling (ionomilling) approach, enabling simultaneous graphite exfoliation, Fe 2 O 3 formation, and composite assembly under ambient conditions. The ionic liquid served as both an exfoliation medium and surface-functionalization agent, promoting improved dispersion of Fe 2 O 3 within the graphene framework and enhancing interfacial charge transport. Structural characterization by SEM-EDX, XRD, FTIR, XPS, and BET analyses confirmed the successful formation of a mesoporous Fe 2 O 3 /IL-graphene nanocomposite with a high specific surface area of 340 m 2 g −1 and well-preserved hematite phase. The electrochemical performance of the composite was evaluated in 2 M KOH electrolyte using a three-electrode configuration. The Fe 2 O 3 /IL-graphene electrode provided a high specific capacitance of 668 F g −1 at 1 A g −1 and retained 73% of its capacitance at 15 A g −1 , demonstrating excellent rate capability. The Fe 2 O 3 /IL-graphene electrode delivered an energy density of 59.38 Wh kg −1 at a power density of 890.7 W kg −1 and retained 39.82 Wh kg −1 at 13,031.3 W kg −1 , demonstrating excellent energy-power characteristics. Moreover, it exhibited outstanding cycling stability, retaining 94.7% of its initial capacitance after 10,000 charge-discharge cycles. The enhanced electrochemical performance is attributed to the synergistic combination of pseudocapacitive Fe 2 O 3 , the highly conductive graphene network, and ionic liquid-derived surface functionalities, which collectively facilitate rapid electron transport, efficient ion diffusion, and improved interfacial charge-transfer kinetics. These findings demonstrate that ionic liquid-assisted ball milling provides a simple, scalable, and solvent-free route for the preparation of high-performance Fe 2 O 3 /graphene-based electrode materials for advanced energy-storage applications.