Construction of MnO2 nanowires@Ni1−xCoxOy nanoflake core-shell heterostructure for high performance supercapacitor

Abstract The hierarchical MnO 2 @Ni 1−x Co x O y composites with ultrathin Ni 1−x Co x O y nanoflakes uniformly grown on MnO 2 nanowire are prepared by a hydrothermal reaction-chemical bath deposition-calcination method, and further investigated on the performance as the electrodes for supercapacitor. The delicately designed core-shell heterostructure takes advantage of the high effective surface area, facile electrolyte diffusion and fast electron transfer. When tested as an electrode material for supercapacitor, the resulting MnO 2 nanowires@Ni 0.75 Co 0.25 O y nanoflake composite exhibits the highest specific capacitance of 476.8 F/g at 0.5 A/g, high rate capability with 83.1% retention at 2 A/g and excellent cycling stability with 94.3% retention of the initial capacitance after 1000 cycles. The smaller charge transfer and electrolyte diffusion resistance are mainly demonstrated to be responsible. The analyses open a new door to develop the optimal nanostructure of electrode materials for high performance supercapacitor.