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

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 alpha-Fe2O3 nanoparticles. The loading percentages of Ni(OH)(2) in the Ni(OH)(2)-alpha-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)-alpha-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)-alpha-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.