Extraction of Capacitive and Noncapacitive Contributions of Partially Oxidized Graphene for Supercapacitor

This work presents a facile, acid-free chemical-sonication method to synthesize defect-controlled, partially oxidized graphene (POG) with specific oxygen functionalities for binder-free thin film electrodes in supercapacitors. Eliminating insulating binders preserves the material’s intrinsic conductivity and porosity, enhancing charge transport and ion accessibility. Dunn’s method was used to extract capacitive and noncapacitive components in the POG electrode. The high capacitive contribution in POG compared to reduced graphene oxide (rGO) is attributed to its lower defect density and enhanced ion adsorption/desorption kinetics. The POG electrode exhibits a high specific capacitance of 22.04 mF/cm2 at 0.1 mA/cm2, enabled by its favorable structural and chemical features, including high conductivity (∼9.22 S/cm), a C/O ratio of 3.67, and low defect density (ID/IG = 0.79 ± 0.04). An asymmetric supercapacitor device using POG as the cathode and rGO as the anode delivers an energy density of 1.56 μWh/cm2 and a power density of 80.23 μW/cm2, with 82% capacitance retention over 10,000 cycles. This work demonstrates the promise of binder-free POG electrodes for high-performance and miniaturized energy storage devices.