Morphology-controllable synthesis of 3D CoNiO2 nano-networks as a high-performance positive electrode material for supercapacitors

Here, we report a novel three-dimensional (3D) assembly of CoNiO2 nanowire networks using a facile and scalable hydrothermal method followed by an annealing process for supercapacitor applications. The X-ray diffraction (XRD) results revealed the formation of highly-crystalline CoNiO2 nano-networks. Scanning electron microscope (SEM) analysis showed the formation of a 3D interconnected network of CoNiO2 nanowires during the synthesis. In addition, a formation mechanism for 3D CoNiO2 nano-networks was proposed. Electrochemical analysis showed a typical pseudocapacitive behavior for the CoNiO2 nanowire networks. The as-prepared CoNiO2 electrode exhibited a high specific capacitance of 1462 F g−1 (45.32 F cm−2) at a current density of 1 A g−1 (31 mA cm−2) and an excellent rate capability of 1000 F g−1 (31 F cm−2) at 32 A g−1 (992 mA cm−2). Moreover, a good cycle stability was achieved at 4 A g−1 with no degradation over 800 cycles, indicating the stable 3D structure of CoNiO2 after the redox reactions. The high rate capability and the good cycle stability indicated that the as-prepared 3D CoNiO2 electrode could satisfy the needs of supercapacitors with both high power and energy densities.