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.