Nanoparticle-Mediated Physical Exfoliation of Aqueous-Phase Graphene for Fabrication of Three-Dimensionally Structured Hybrid Electrodes

Monodispersed polypyrrole (PPy) nanospheres were physically incorporated as guest species into stacked graphene layers without significant property degradation, thereby facilitating the formation of unique three-dimensional hybrid nanoarchitecture. The electrochemical properties of the graphene/particulate PPy (GPPy) nanohybrids were dependent on the sizes and contents of the PPy nanospheres. The nanohybrids exhibited optimum electrochemical performance in terms of redox activity, charge-transfer resistance, and specific capacitance at an 8:1 PPy/graphite (graphene precursor) weight ratio. The packing density of the alternately stacked nanohybrid structure varied with the nanosphere content, indicating the potential for high volumetric capacitance. The nanohybrids also exhibited good long-term cycling stability because of a structural synergy effect. Finally, fabricated nanohybrid-based flexible all-solid state capacitor cells exhibited good electrochemical performance in an acidic electrolyte with a maximum energy density of 8.4 Wh kg^-1 or 1.9 Wh L^-1 at a maximum power density of 3.2 kW kg^-1 or 0.7 kW L^-1; these performances were based on the mass or packing density of the electrode materials.