High capacitance and good rate performance supercapacitors are needed to power sensors and miniaturized electrical devices. Thick electrodes are promising to increase the mass loading of active materials in supercapacitors, but the 3D geometries and microstructures in thick electrodes still hinder the development with high electron and ion exchange rate and accessible active sites. The scaffold 3D electrodes of reduced graphene oxide:manganese oxide/carbon nanotube (rGO:MnOx/CNT) are manufactured by material extrusion 3D printing (ME3DP), where the mass ratio of rGO to MnOx/CNT composites, thickness, and mass loading per unit area are controllable. The increasing amount of MnOx/CNT composites boosts the areal capacitance. Although the rate capability decays fast with the increasing of MnOx/CNT, it remains stable at different thicknesses (1.2, 1.6, and 2 mm). 2 mm thick rGO:MnOx/CNT (weight ratio 5:3) electrode exhibits an area capacitance of 302.13 mF cm−2 at a current density of 0.5 mA cm−2, due to the highly ordered rGO networks. Compared to the casted electrodes, the microstructures in the 3D printed electrode contribute to lower resistances for the charge and ion transportation. [ABSTRACT FROM AUTHOR]