| The supercapacitor is a new type of energy storage device with performance of fast charging/discharging speed,high power density,long-term cycling stability and wide operation temperature.It is widely studied and applied in new energy vehicles,solar energy systems,wearable devices and other fields.For supercapacitors,the electrode is the key element that greatly matter the overall performance.As an extrinsic pseudocapacitive material,?-Co(OH)2 has been widely studied for its high theoretical specific capacitance,good conductivity,hydrotalcite-like layered structure and abundant resources.However,the poor cycle stability and low actual capacitance of?-Co(OH)2 have greatly hindered their large-scale commercial application.To solve these key problems,it is necessary to explore electrode materials with electrode with excellent electrochemical performance.In that case,the rational design and synthesis of morphology and structure for cobalt hydroxide and composites,and systematically study the underlying rules of between electrochemical properties and morphology,structure and composition.We prepared different morphologies of?-Co(OH)2,heterojunction CoSx/?-Co(OH)2 nanomaterials with different compositions,and studied their electrochemical properties.The specific work are as follows:(1)we present a facile solvothermal approach to rationally design and fabricate chiffon-like and hydrotalcite-like?-Co(OH)2 nanoflakes for extrinsic pseudocapacitive electrode,which exhibits linear galvanostatic discharge behavior and superior charge-storage performance,including high capacitance of 475F/g at 1A/g,excellent rate capability and superb cycling stability with capacitance retention of 93.9% after 10000 cycles at 10A/g.The superior performance is mostly attributed to the good electrical conductivity and stable microstructure of the hydrotalcite-like?-Co(OH)2nanoflakes and the abundant redox active sites on the chiffon-like nanoflakes with short and facile electron transport.In addition,other?-Co(OH)2 samples with different morphologies and size as contrast are prepared and discussed,indicating that the morphology/size design and optimization of the?-Co(OH)2 could greatly improve the electrochemical energy-storage performance.The findings demonstrate that the chiffon-like and hydrotalcite-like?-Co(OH)2 nanoflakes have a great practical application potential in long-life and high-performance supercapacitors.This study also presents a facile way to design and prepare nanoflake-like materials with adjustable lateral size and thickness from spherical morphology consisting of nanoflakes.(2)Based on the chiffon-like and hydrotalcite-like?-Co(OH)2 nanoflakes,therefore,the construction of heterostructural CoSx/?-Co(OH)2 nanosheets with enhanced pseudocapacitive performance by ion-exchange reaction method.The?-Co(OH)2 nanosheets serve as the conductive backbone because of both its intrinsic superior conductivity and the built-in electric field at the CoSx/?-Co(OH)2heterostructure interface as well as the main contribution to power density,and the CoSx growing on the?-Co(OH)2 nanosheets through an ion-exchange method is primarily conductive to capacitance and energy density.Additionally,the built-in electric field could also facilitate the electron transfer and then redox reaction of the CoSx.The electrode(CoSx/?-Co(OH)2-3h)exhibits ultrahigh specific capacitance(2411F/g at 1A/g)and good rate capability.Furthermore,an asymmetric supercapacitor is fabricated with the as-prepared heterostructural CoSx/?-Co(OH)2nanosheets as the positive electrode and activated carbon as the negative electrode,obtaining delivers a maximum energy density of 28.1Wh/kg and the maximum power density of 2876W/kg in the potential window of 1.6V. |
PDF Full Text Request