Controlled assembly of NiCo-LDH nanosheets into diverse superstructures via concentration-dependent solvothermal method for advanced supercapacitors

Abstract

The tunable layer structure, composition, and diverse morphologies of layered double hydroxides (LDHs) make them a favorable choice as pseudocapacitive electrode materials for supercapacitors. However, the severe agglomeration and low conductivity of nanosheets are detrimental to obtaining excellent electrochemical performance. In this work, a controllable assembly of nanosheets was achieved by adjusting the concentrations of Ni and Co salt solutions, resulting in a series of 3D-shaped NiCo-LDHs superstructures with diverse morphologies. The prepared structures were found to significantly reduce aggregation and electron transport distance. The results approved that the diameter, thickness and interlayer space of NiCo-LDHs nanosheets and the morphologies of their self-assembled superstructures were subtly controlled, and significantly impacted their electrochemical performance. A stretch trumpet shaped flower-like superstructure in NiCo-LDH-2 was constructed by the large and ultrathin nanosheets with much more accessible active sites and larger interlayer space, which can rapidly promote electron transfer and show the highest specific capacitance of 2265 F g−1 at 1 A g−1 and retention of 86.5% at 20 A g−1. The NiCo-LDHs//AC ASC based on NiCo-LDH-2 and active carbon (AC) reveals a high specific capacitance of 298 F g−1 at 1 A g−1 and an excellent energy density of 105.0 Wh kg−1 at the power density of 820.1 W kg−1. The current work presents a simple way for controlling the nanostructure of NiCo-LDHs in the development of high-performance supercapacitors.