Hybrid electrochemical supercapacitor based on birnessite-type MnO2/carbon composite as the positive electrode and carbonized iron-polyaniline/nickel graphene foam as a negative electrode

In this work, a birnessite-type MnO2/carbon composite with hierarchical nanostructures was synthesized using KMnO4 solution and spent printing carbon grains. A hybrid electrochemical supercapacitor device was fabricated based on the birnessite-type MnO2-carbon composite electrode and carbonized iron-polyaniline/nickel graphene foam as positive and negative electrodes, respectively. At the lowest specific current of 1.0 A g(-1) and cell potential of 2.2 V in 2.5M KNO3 electrolyte, the device displayed a high energy and power density of 34.6 W h kg(-1) and 1100.0 W kg(-1), respectively. The device further displayed long-term cycling stability with a capacitance retention of 98% over 10 000 galvanostatic charge-discharge cycles at 10 A g(-1). This device displays the overall excellent electrochemical performance.