Preparation Of Metal Oxides Of Co?Fe And Cu By Dealloying And Research On Their Electrochemical Properties

Supercapacitors are promising energy-storage devices with high power density and long cycling life,and have been applied in various fields,such as aerospace,electric vehicles and defense,modern communications,and so on.As the the commercial supercapacitors showing lower energy density,one great challenge for the supercapacitor technology is to improve the energy density,however,without sacrificing the power density and stability.Hybrid supercapacitor is a new type of energy storage device that bridge the gap between supercapacitors and rechargeable batteries by combining battery-type electrodes and capacitor-type electrodes,which can achieve high energy density at high current density.Aiming to develop hybrid supercapacitor with high energy and power density,this dissertation extensively investigates issuses on controllable preparation of transition metal oxide,rational design of electrode architectures,charge storage mechanism and construction of aqueous symmetric supercapacitor.A series of original research has been carried out on the preparation by designing and practical application of the flexible all-solid asymmetric supercapacitor.1 Study on the design and electrochemical properties of Co₃O₄ nanostructures.The Co₃O₄ electrode material was prepared by the in-situ dealloy assisted oxidation method.By regulating the concentration and temperature of NaOH aqueous solution,the different morphologies of Co₃O₄ were prepared,which were nano-chip,nano-chip array,nano-flower,nanosphere and other structures.The area of the nanosphere is the highest(16.58 F cm^-2),followed by the nano-flower structure(9.27 F cm^-2),but the latter showed better structural stability in the aspect of cyclic stability.2 Design and electrochemical properties of Cu₂O/CoO nanowire array electrodes.The Cu₂O/CoO-NNAs electrode materials of nano-porous Cu/Co alloy were synthesized by the selective in-situ dealloy assisted oxidation method.The electrode materials need no conductive agent and binder,and have good mechanical stability and integrity.With Cu₂O/CoO as electrode and Na₂SO₄ as electrolyte,the symmetrical supercapacitor has excellent electrochemical properties.The specific capacitance of the device is 0.21 mF cm^-2under the current density of 5 mA cm^-2,with little attenuation after 10,000 cycles at high current density 10 mA cm^-2.The maximum volume energy density of the symmetrical supercapacitor is 0.81 W h cm^-3,and the maximum volume power density is 3 W cm^-3.3 Study on the design and electrochemical properties of Co₃O₄//?-Fe₂O₃ solid-state flexible ASC.The Co₃O₄ nanometer tablets and the?-Fe₂O₃ nanoparticles were prepared in a simple and fast manner by the three steps:at first Al₇₁Fe₂₉and Al₆₅Co₃₅alloy belts were prepared by arc melting and sling method;and then,the controlled particle sizes of the precursor powder was obtained via the method of dry ball mill;at last,the positive and negative electrode materials in the micro scale was controlled by optimizing the dealloying parameters.The flexible all-solid ASC can be reversibly charged and discharged between 0 and 1.7 V.The maximum power density of the ASC is 8.5 kW kg^-1,and the maximum energy density is 38.01 kW kg^-1.The capacity can still retain 80.1%at 4 A g^-1current density after 5000 circulations.There is no variration in the CV curves at the twisting test,showing the excellent electrochemical stability of this flexible all-solid ASC.Meanwhile,the series parallel combination of the device can meet the requirement of energy storage for its actual use.4 Research on the design and electrochemical properties of Cu₂O//AC all-solid ASC.Cu₂O nanoparticles were rapidly prepared by dealloy assisted oxidation method.The capacitance at the current density of 0.5 A g^-1is 210.9 F g^-1,and the retention rate after 5000 cycles is up to 93.3%at the current density of 3 A g^-1.Cu₂O//AC flexible all-solid ASC can be charged and discharged between 0 and 1.65 V.The device shows good flexibility,because it maintains good electrochemical stability at different twisting CV tests.The four devices in series could provide power to the LEDs,which proves their potential application value in practice.