Construction of MnO2/3-dimensional porous crack Ni for high-performance supercapacitors

MnO2/3-dimensional porous crack nickel (MnO2/3-DPCNi) electrode has been fabricated via an alloying/dealloying process and an electrochemical oxidation process. The construction of the 3-DPCNi was achieved by means of electrodeposition of Zn-Ni alloy on Ni foam substrate, followed by chemically dealloying process under free corrosion conditions. Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and structure of the 3-DPCNi. The electrochemical properties of the MnO2/3-DPCNi electrode were investigated using cyclic voltammetry (CV), galvanostatic charge/discharge (GC/D) and electrochemical impedance spectroscopy (EIS) technique. It is shown that a layer Ni with a cracked network was well coated on the Ni foam substrate. Such porous crack structures of 3-DPCNi not only provided a conductive network to enhance the charge transport and mass transfer in the electrochemical process but also achieved a large MnO2 mass loading capacity of 14.4 mg cm−2, which resulted in a high areal capacitance of 3.18 F cm−2 at a current rate of 0.25 A g−1. A specific capacitance of 682.8 F g−1 was obtained based on the MnO2 mass loading density of 2.5 mg cm−2 at a current rate of 0.25 A g−1. Moreover, the MnO2/3-DPCNi electrode also exhibited a low ions diffusion resistance and a good cycling performance along with 93.3% specific capacitance retained after 1000 cycles. These results demonstrated that the 3-DPCNi was a promising supporting material for energy conversion and storage devices.