Spontaneously grown Ni(OH)2 on iron oxide nanoparticles with enhanced energy storage performance for electrodes of asymmetric supercapacitors

Abstract

Iron oxide nanoparticles intercalated in Ni(OH)₂ nanosheets were prepared in a spontaneous way for the cathode materials of asymmetric supercapacitors. The soluble precursor of Ni(OH)₂, Ni(NH₃)₆(OH)₂, was used for growth on α-Fe₂O₃ nanoparticles. The loading percentages of Ni(OH)₂ in the Ni(OH)₂–α-Fe₂O₃ nanocomposites had a great influence on the morphology and size of Ni(OH)₂. The composites were characterized by TEM, SEM, ICP-OES, XRD and XPS. The specific capacitance of Ni(OH)₂ in the composite can reach 1107 F g⁻¹ at a scan rate of 20 mV s⁻¹, and the specific capacitance of the Ni(OH)₂–α-Fe₂O₃ composite can be up to 376 F g⁻¹ at a scan rate of 5 mV s⁻¹. More importantly, the fabricated Ni(OH)₂–α-Fe₂O₃//AC (activated carbon) asymmetric supercapacitor exhibited energy density and power density of 31.6 W h Kg⁻¹ and 474 W Kg⁻¹, respectively. The cycling performance of the asymmetric supercapacitor was also excellent, and the capacitance retention reached 89.6% after 5000 charge–discharge cycles. Red, blue and yellow LED lights can be lit up with two series of asymmetric supercapacitors, revealing their potential application in energy storage.