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

• Graphene/PANI/MnO 2 composites are fabricated by facile two-step electrodeposition. • Graphene hydrogel films act as working electrodes for sequential electrodeposition. • The ternary composite electrode exhibits excellent capacitive performance. • The symmetric device performs well in rate capacity, stability and energy density. 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)/MnO 2 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 MnO 2 granules are electrodeposited on the RGO/PANI conductive substrates to obtain the free-standing composite films. The resulting RGO/PANI/MnO 2 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 MnO 2 can compensate each other to surmount the disadvantages of inferior conductivity or stability. [Display omitted] [ABSTRACT FROM AUTHOR]