Sequential electrodeposition fabrication of graphene/polyaniline/MnO2 ternary supercapacitor electrodes with high rate capability and cyclic stability

The incorporation of various capacitive materials to fabricate multi-component electrodes has emerged as a feasible methodology toward high-performance supercapacitors. In this paper, a facile two-step electrodeposition method is proposed to construct polyaniline (PANI)/MnO2 hybrid nanostructure on reduced graphene oxide (RGO) matrix for the ternary supercapacitor electrodes. By the sequential potentiostatic methods, PANI is first electropolymerized on RGO hydrogel films before MnO2 granules are electrodeposited on the RGO/PANI conductive substrates to obtain the free-standing composite films. The resulting RGO/PANI/MnO2 ternary composite electrodes present significantly promoted capacitive properties compared with the binary RGO/PANI electrodes. Particularly, the optimized electrode and corresponding all-solid-state device could achieve the high specific capacitances of 942.6 and 205.0 F g-1 at 1 A g-1 with superb capacitance retention of 86.4% and 80.3% at 30 A g-1, respectively. The device delivers a maximum energy density of 41.0 Wh kg-1 and demonstrates outstanding capacitance holdings of 96.1% after 10,000 cycles at 30 A g-1, 87.8% after 5000 cycles at 10 A g-1, and 82.5% after 3000 cycles at 5 A g-1, respectively. The prominent electrochemical performances of the ternary composite can be ascribed to the fact that graphene supplies the conductive matrix to immobilize the active pseudocapacitive constituents, while PANI and MnO2 can compensate each other to surmount the disadvantages of inferior conductivity or stability.