Preparation And Electrochemical Properties Of Zinc Oxide And Its Composite Materials For Supercapacitors

As a new type of green energy storage devices, supercapacitors have significant advantages,such as high power density, long cycling life, fast charging-discharging and environmental friendliness, which will become the most potential next-generation energy storage device.According to the types of charge-storage mechanism, they are generally divided into two categories, i.e., electrical double-layer capacitors(EDLCs) and pseudocapacitors. Carbon materials, attributed to EDLCs, mainly store charges electrostatically through reversible ion adsorption reaction at the electrode/electrolyte interface. Transition metal oxides(TMOs) and conducting polymers, attributed to pseudocapacitors, mainly exploit the fast and reversible Faradic redox process at the electrode surface. Currently, for pesudocapacitors, there has extensive interest in developing TMO electrode, As these TMOs are natural abundance, low cost, and environment friendliness,and partically can provide various oxidation states for efficient redox charge trasfer and enable a higher energy density and a high theoretical.As with different microstructures and compositions, they show substantial differences in supercapacitor performance due to difference in electrode/electrolyte interface properties and ion tranfer rates during the charge storage processes. Recently, owning to synergistic effects, multi-component composites made up of several electroactive materials exhibit excellent electrochemical performance. This paper introduces strategies based on design and synthesis of two Zn O-based hybrid electrode materials aiming at improving the overall capacitive performance, and we fully study and discuss the electrochemical performance. The main contents of this paper are summarized as following:(1) We demonstrate the rational design and preparation of Zn O@Co Ni(OH)2 hybrid electrode materials through a facile hydrothermal and chemical bath deposition process. The Zn O@Co Ni(OH)2hybrid electrode exhibits a large areal capacitance of 0.87 F/cm2 and specific capacitance of 1081 F/g at the current density of 2 m A/cm2, which is superior to pristine Co(OH)2electrode(108 F/g) and Ni(OH)2 electrode(578 F/g). Furthermore,this hybrid electrode also displays good rate capability, even at the current density of 30 m A/cm2, it still maintains 64% of the initial capacitance. Simultaneously, the overall capacitance retention for the Zn O@Co Ni(OH)2hybrid electrode is ultrahigh(85.7% after 3000 cycles).(2) The Zn O@V2O5 hybrid nanorod arrays have been synthesized through a hydrothermal and solvothermal process. We investigated the impact of various Triisopropoxyvanadium(V) oxide monomer concentration and deposition temperature on the morphology of hybrid materials,combining with the result of electrochemical test, and then delivered the optimized scheme(100 ul,130℃,10 h). A hybrid electrode made up of the Zn O@V2O5 core-shell nanorod arrays exhibits a specific capacitance of 152 F/g at the current density of 5 m V/cm2, and the capacitance retenion is still at 93.6% after 2000 cycle number.