Hierarchical self-assembly of ultrathin nickel hydroxide nanoflakes for high-performance supercapacitors

Abstract

Uniform Ni(OH)₂ hierarchical nanostructures, assembled from ultrathin nanoflakes with thickness of only 7.4 nm, are designed and investigated as electrochemical pseudo-capacitor materials for potential energy storage applications. The ultrathin nanostructures exhibit a highest specific capacitance of 1715 F g⁻¹ at a scan rate of 5 mV s⁻¹ within the potential range of 0.6 V with high rate capability and good cycling stability. The high specific capacitance and remarkable rate capability are promising for supercapacitor applications. To understand the effect of the microstructure on the properties, we also synthesized uniformly stacked Ni(OH)₂ nanoplatelets (thickness of 22 nm) and randomly arranged hexagonal nanosheets (thickness of 140 nm). Both of the latter configurations exhibited good performance despite showing inferior properties compared to the uniform ultrathin Ni(OH)₂ nanostructures. These results suggest the importance of rational design and synthesis of ultrathin nanomaterials for high-performance energy applications.