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 (Cs) 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 ∼74 nm and ∼215 nm, respectively, formed films with the thicknesses of ∼5.8 and 2.7 μm, respectively. The mesoporous NiO nanobelts delivered a higher Cs 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.