Preparation Of Co-based MOFs-derived Multi-metal Complex Electrode Materials And The Supercapacitor Performance Study

With the rapid development of high-tech products and portable devices,micro energy storage materials have gradually become objects on which human beings depend.Although lithium devices have been developed and studied,in order to meet the increasing surge of human needs.There is a need to expand broader energy storage materials,for example,supercapacitors.In turn,the construction of supercapacitors is closely related to the selection of electrode materials,which have high surface area,multiple active sites,and porous characteristics have attracted extensive attention from researchers,so the development of economical,effective and high energy density energy storage electrodes is a major challenge for the practical application of supercapacitors.By reviewing a large amount of literature,three experimental schemes were designed and conceived in this thesis system to synthesize three superior performance electrode materials,namely,bimetallic selenide,nickel cobaltate-coated bimetallic telluride and ternary metal double hydroxide,and then to analyze and study their morphological structure,chemical elemental composition and corresponding electrochemical properties by means of basic characterization,with the following experimental details:(1)Preparation of(Ni,Co)Se₂/CF heterojunction twist-like nanorod array electrodes and their supercapacitor performance studyIn this experiment,CF@Co-MOF nanorod-like precursors were first successfully prefabricated on carbon fiber cloth by a simple static method.Three morphologies of CF@NiCo-LDH/T-M were generated by etching at different times.The results show that the etching at different times has a great influence on the morphology and properties of CF@NiCo-LDH,compared to CF@NiCo-LDH/2.0 h which has a larger surface area and more gaps,which is favorable for ion passage and redox reaction.Finally,CF/(Ni,Co)Se₂was obtained after the selenization reaction on the basis of CF@NiCo-LDH/2.0 h.This CF/(Ni,Co)Se₂ has excellent capacitive properties in a three-electrode system(1360 F g^-1 at 1.0 A g^-1),and an outstanding cycling stability with a high capacity retention of 90%after 8000 cycles.Finally,an asymmetric supercapacitor device composed of activated carbon(AC)as anode electrode and CF@(Ni,Co)Se₂ as cathode electrode was designed,which reveals a high voltage window of 0-1.6 V and exhibits a great energy density(E)of 36.02 Wh kg^-1 at the power density(P)of 800 W kg^-1.Therefore,the twisted granular heterogeneous structure of CF@(Ni,Co)Se₂ is more advanced for the future construction of conductive capacitors,and the different time etching methods used in this experiment can be extended to other related energy materials to alleviate more energy problems.(2)Preparation of(NF@(NiCo)Te/CoNiO₄)nickel cobaltite core shell electrode and its supercapacitor performanceIn this experiment,NF/NiCo-CH alkali compound precursor was first synthesized on nickel foam substrate by hydrothermal method,then(NF/NiCo)Te complex was synthesized by vapor deposition method,and finally the preparation of nickel-cobalt telluride core-shell structure(NF@(NiCo)Te/Co_1.29Ni_1.71O₄)electrode wrapped by nickel cobaltate and its supercapacitor performance were synthesized by hydrothermal method.The highest specific capacity of the prefabricated electrode was measured to be 2254 F g^-1 at a current density of 1 A g^-1.The AC as the cathode and the(NF@(NiCo)Te/Co_1.29Ni_1.71O₄)as the anode ASC to assemble the component.That is,the(NF@(NiCo)Te/Co_1.29Ni_1.71O₄)//AC working electrode is formed,the device exhibited excellent electrochemical performance with a measured capacitance of179.01 F g^-1 at a current density of 1 A g^-1.In addition,when the power density(P)was800 W kg^-1,the energy density(E)of this assembled ASC device reached an impressive48.7 Wh kg^-1.(3)Preparation of NiCoZn-LDH ternary metal nano sheet coated Zi F-8 composite electrode and its supercapacitor performanceFor this experiment,the ZIF-8 precursor was first synthesized by the static method overnight at room temperature for 12 h.The material structure was ortho-8-sided,and then by the hydrothermal method,the trimetallic hydroxide was synthesized by adding Ni,Co and other metal elements into a layer of nucleoshell-wrapped ortho-8-sided.The synthesized particulate metal NiCoZn-LDH composite electrode exhibits excellent electrochemical performance(2016 F g^-1at 1 A g^-1),Then the ASC system(i.e.,NF/NiCoZn-LDH//AC)is formed using the particulate metal NiCoZn-LDH as the anode and AC as the cathode at the same time.The assembled asymmetric supercapacitor(NF/NiCoZn-LDH//AC)possesses an extremely high specific capacitance of(160 F g^-1at 1 A g^-1).In addition,the system has an energy density of up to 50.2 Wh kg^-1,when the power density(P)is 800 W kg^-1.Finally,its stability is maintained at 92%(10000 turns)after cycle testing.This shows a directional path for the assembled(NF/NiCoZn-LDH//AC)system for future energy storage and provides a new idea for future development of multi-metal electrodes.