Atomic Layer Deposition of ZnO on the 3D Porous Ni(OH)2 Nanostructure for Supercapacitor Applications

Abstract

Atomic Layer Deposition (ALD) is a unique vapor-phase non-line-of-sight deposition process, it can provide excellent control over the wall thickness of nanostructures at the sub-angstrom scale and can be used to create highly conformal coatings of dense inorganic film even on the nano-sized templates with high aspect ratios. Due to these inherent merits, it has become an inevitable process in current semiconductor industries. Following the success of ALD in the semiconductor industries, ALD is recently focused because it can efficiently enhance the performance of energy conversion and storage devices.As a representative example, electrochemical supercapacitors, as one type of novel power device, have attracted universal research interest because of their great potential to be applied in many fields. In particular, pseudocapacitor is recently focused due to its larger capacitance. The electrochemical energy conversion and storage performance of pseudocapacitors depends strongly on the intrinsic properties of the active electrode materials and their surface area. To maximize these performance, various nano-morphologies and transition metal oxides/hydroxides, such as NiO, Co3O4, MnO2, Ni(OH)2 and etc., having a large theoretical capacitance has been extensively investigated. Those psuedocapacitor materials, however, generally showed a high electrical resistivity and it remain unable to achieve high theoretical capacitance in practical applications.To solve these drawbacks, ultrathin conductive ALD coatings can be considered. As a representative example, we design and fabricate a novel hybrid 3D Ni(OH)2@ZnO nanostructured electrode material with a high surface area and high conductivity using a hydrothermal method and ALD. ALD-ZnO thin films were deposited on the surface of a 3D porous Ni(OH)2 nanostructure. The optimization of ALD-ZnO was performed to achieve a high conductivity and electrochemical performance. And, it was exhibited that this hybrid 3D core-shell structure, which benefits from the synergistic effects of both Ni(OH)2 and ZnO, can result in a much improved supercapacitor performance.