Synthesis Of Three-Dimensional Self-Supported Metal Oxides/Sulfides Based Core-Shell Architecture Composite Electrodes And Their Applications In Supercapacitors

Supercapacitor,as a novel type of energy storage and conversion device,can be applied in consumer electronics and new-energy vehicles due to its superior advantages of quick charging/discharging at large currents,higher power density than lithium batteries and long-term cycling life.However,the unsatisfactory energy density has limited its large-scale commercialization.Therefore,exploring supercapacitor with high energy density and high rate capability is a research hotspot.Electrode is the core component of supercapacitor and its electrochemical performance is the determining factor for supercapacitor performance.Transition metal?Co,Ni,Mn,etc.?oxides/sulfides are widely studied as electrode materials due to their abundant resources,low cost and high theoretical specific capacitance.However,pure transition metal oxides/sulfides can not serve as electrodes with high electrochemical performance because of their poor conductivity and stability.Studies have shown that modification of nanostructure for materials is one of the effective methods to enhance electrochemical activity.Self-supporting core-shell structure materials possess following merits:?i?having larger specific surface area and more electroactive sites;?ii?stable structure which can not be easily destroyed during redox process;?iii?the samples can be directly used as electrodes without any conductive agent or adhesive added which owns small impedance and excellent conductivity.In view of the discussion above,this work is dedicated to the construction of a novel three-dimensional self-supporting metal oxide/sulfide core-shell hierarchical structure composite for electrode material.The main contents are summarized as follows:?1?Glucose intercalated LDH@Co₃O₄ nanowire array core-shell hierarchical structure composite was successfully grown vertically and directionally on three-dimensional porous nickel foam via hydrothermal-calcining method.The structure and morphology of the composite was analyzed by various characterization methods and the electrochemical properties of the composite was further measured.The electrochemical test result shows that when the current density is 1 A g^-1 and 10 A g^-1,the specific capacitance is 1644 F g^-1 and 697 F g^-1.Meanwhile,after charging/discharging for 5000 cycles at the current density of 10 A g^-1,the specific capacitance still retains 94.2%,which can demonstrate its excellent cycling stability.the energy density can reach up to 38.4 W h kg^-1 when it serves as positive electrode for assembled supercapacitor device,indicating its superior practical application value.?2?The three-dimensional Co₃O₄/NiS core-shell nanowire arrays were in-situ grown on nickel foam via a hydrothermal-calcining method.SEM,TEM,XRD,XPS and other characterization methods were employed to analyze the composition and morphology of the material.It can be directly used in three-electrode system without adding any conductive agent and adhesive.The result shows that when the current density is 1 A g^-1,the specific capacitance is 1395.3 F g^-1.As the current density increasing to 10 A g^-1,the specific capacitance still maintains for 711 F g^-1,demonstrating its great specific capacitive.When used as positive electrode for supercapacitor device,the energy density is as high as 61.34 W h kg^-1,proving its potential practical application.A two-supercapacitor tandem device could light up the commerical LED lights.?3?The three-dimensional self-supported MnCo₂S₄/NiMoO₄ core-shell nanowire arrays electrode material based on carbon cloth was prepared through a hydrothermal-calcining method.The composition,morphology and electrochemical properties of the composite electrode were investigated.The three electrode system measurement result shows that when the current density is 1 A g^-1,the specific capacitance is 1832.9 F g^-1.When used as the positive electrode of asymmetric supercapacitor,the energy density can reach 75.73 W h kg^-1.A two-assembled supercapacitor tandem device could serve as an electric generator to support a fan to run.After 2000 charging and discharging cycles at the current density of 5 A g^-1,the specific capacitance of the device still remianed 90.4%,indicating its excellent cycling stability.