Property Investing of Hierarchically Layered Double Hydroxide and Derivative as Binder-free Electrode for High Performance Supercapacitors

Abstract

Among various electric energy storage technologies, supercapacitors have attracted a considerable amount of attention due to their high powers density, fast charge/discharge capability and exceptionally long cycle life. However, the practical applications of supercapacitors are largely hindered by the relatively poor performance or finite availability of the electrode materials. In this study, First, constant voltage, Nickel Aluminum-layered double hydroxide nanosheet arrays (NSAs) were successfully grown on Co3O4 nanowires as binder free electrode for a supercapacitor. Layered double hydroxide nanosheets with active surface area evenly sparsed on the surface of Co3O4 to achieve fast electron transport and increase the electrochemical properties of LDH nanosheets. High specific capacitance of 2011 F g−1 was display at a current density of 1 A g−1, and the specific capacitance of the Co3O4@NiAl-LDH as high as 1454 F g−1 at a current density of 40 A g−1 with retention rate of 72%. ASC was manufacture using Co3O4 @ LDH nanosheets as the positive electrode and CNT as the negative electrode. The ASC exhibited a high energy density of 18 Wh kg−1, and the corresponding power density was 374 W kg−1. Second, the non-binder electrodes comprise of hierarchically constructed nickel cobalt sulfide core were manufactured by a hydrothermal method along with electrodeposited nickel cobalt layered double hydroxide core-shell nanotube arrays grown in situ on Ni foam for use in supercapacitors. Compare with the different electrodeposition time as 10s, 20s and 80s, the NiCo2O4 nanotubes coated with nickel cobalt layered double hydroxide by electrodeposition for 40 s display the highest specific capacitance (2105.05 F g−1 at the current density of 2 A g−1) and excellent cycling stability. Moreover, a battery-type device based on NCS@NCOH as the positive electrode and active carbon (denoted as AC) as the negative electrode, delivering a high energy density of 23.73 W h kg-1 at power density of 400 W kg-1, which was fabricated for practical applications. Third, to improve the performance of supercapacitor base on the MXene, we synthesized a MXene “clay” electrode base on nickel foam without any binders, then in-situ electrodeposited NiCo2S4 nano-flakes on the surface of MXene depend on the electrostatic interactions. As a result, the MXene-NiCo2S4 electrode exhibits high specific capacitance of 1147.47 F g-1 at 1 A g-1 and keep excellent rate performance in 6M KOH aqueous electrolyte. Furthermore, an asymmetric solid-state supercapacitor (ASC) was assembled using MXene-NiCo2S4 as positive electrode and active carbon as negative electrode delivers high energy density (27.7 Wh kg-1 at the power density of 0.48 kW kg -1).