Microwave-assisted binder-free synthesis of 3D Ni-Co-Mn oxide nanoflakes@Ni foam electrode for supercapacitor applications

The outstanding performance of nickel foam (NF) as a current collector owing to its better dimensional stability, high electrical conductivity, and less contact resistance has made it a promising candidate for binder-free electrode for supercapacitors. In addition to the current collector, highly stable structures are also favored to facilitate rapid ion insertion and prevent structural collapse of the electrode materials. In this work, a binder-free and controlled structure of Ni-Co-Mn oxide on NF was constructed effectively using microwave irradiation. The structure obtained from the optimal conditions (concentration and holding time) involved hierarchical interconnected nanoflakes with void spaces, forming a stable and conductive network of nanoflakes on the NF. The synergistic effects of three metal (Ni-Co-Mn) oxides resulted in a high specific capacitance of 2536 F g(-1) at 5 mA cm(-2) (6.49 A g(-1)) in a mixed KOH/K3Fe (CN)(6) electrolyte. The as-prepared symmetric device also obtained a high capacitance of 298 F a high energy density of 41.4 Wh kg(-1), and a high power density of 5.4 kW kg(-1). The highly architectured Ni-CoMn oxide nanoflakes improved the pseudocapacitive performance significantly, making it a promising electrode material for high-performance binder-free supercapacitors. (C) 2017 Elsevier B.V. All rights reserved.