Supercapacitors are known for their fast-charging capabilities and high-power density, though their energy density is lower compared to common batteries. Modifying the interface of manganese oxide (MnOx) electrodes by incorporating copper (Cu) is a promising method to enhance the energy density of supercapacitors, though it is not yet fully implemented due to the high electrical resistance inherent to MnOx. This work addresses this challenge by incorporating copper oxide into MnOx. A custom-designed atmospheric-pressure plasma device is used to induce super-hydrophilicity in the carbon cloth substrate, thereby improving MnOx electrodeposition. The copper sulfate precursor solution is also treated with direct plasma discharge to increase the copper doping rate in MnOx. The resulting Cu-MnOx supercapacitor electrodes, with copper oxide incorporated into the material, exhibit significantly lower charge transfer resistance and impedance, indicating an improved electrolyte/electrode interface. The assembled asymmetric supercapacitor, featuring Cu-MnOx as the cathode and activated carbon as the anode, demonstrates a specific capacitance of 92.3 F/g at 1 A g-1, a power density of 700 W/kg, and an energy density of 25.13 Wh/kg. This approach is promising for developing next-generation plasma processing technologies and energy storage materials and devices, as well as easy-to-implement surface modifications for improved wettability.