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

Abstract

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 ∼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 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.