Perforated mesoporous NiO nanostructures for an enhanced pseudocapacitive performance with ultra-high rate capability and high energy density

We reported a morphology-controlled approach to improve the specific capacitance (C-s) and energy/power density of supercapacitors. The irregular morphologies of NiO transformed into perforated mesoporous nanobelts and further altered into nanoflakes. The nanobelts and nanoflakes of NiO with the average widths of similar to 74 nm and similar to 215 nm, respectively, formed films with the thicknesses of similar to 5.8 and 2.7 mu m, respectively. The mesoporous NiO nanobelts delivered a higher C-s value (i.e., 794 F g(-1)) than the nanoflakes (146 F g(-1)) and irregular morphologies (742 F g(-1)). Moreover, the nanobelts showed 88.6% retention after 2500 continuous charging-discharging cycles. The NiO nanobelts exhibited a power density of 2963 W kg(-1) and energy density of 57 W h kg(-1), which were significantly higher than those of pristine NiO nanoflakes, nanorods, 2D thin films, porosity-tuned nanowalls, nanofibers, and the heterostructures with the NiCo2O4 and Ni3S2 nanosheets. The perforated mesoporous NiO nanobelts with clearly visible textural boundaries exhibited a relatively larger surface area and excellent interconnecting network than the irregular morphologies and nanoflakes, which provided easy access to the OH- ions for diffusion.