Design And Preparation Of Molybdenum-Coblt Based Electrode Material And Supercapacitor Performance Study

Molybdenum-cobalt-based compounds have attracted great interest in lithium-ion batteries and supercapacitors due to their fast reversible redox reactions and high redox potentials.However,the preparation process of electrode materials is susceptible to agglomeration effect,resulting in bad structural stability,low specific surface area,low porosity and other results,making the actual capacity of the materials much lower than the theoretical capacity,limiting further applications in the field of energy storage.Therefore,the rational design and optimization of molybdenum-cobalt-based electrode materials to achieve efficient energy storage is particularly important.In this work,the electrode materials prepared by using metal-organic framework materials（MOFs）as sacrificial templates have high specific surface area,electrochemical activity and structural stability,and the energy storage behavior of molybdenum-cobalt-based electrode materials is significantly improved.The main studies are as follows:（1）The CoMoO₄@Co₃O₄ composite was designed using ZIF-67 as a template.the CoMoO₄@Co₃O₄ electrode exhibited a high specific capacity of 2003 F g^-1 at a current density of 1 A g^-1,and the specific capacity could reach 68%of the initial capacity after 5000charge-discharge cycles.Using ZIF-67 as a template not only improves the specific surface area of the material but also provides part of the reactive material,and the CoMoO₄@Co₃O₄composite inherits the morphological framework of ZIF-67,which is conducive to the improvement of the cycling stability of the material.The asymmetric supercapacitor CoMoO₄@Co₃O₄//AC can provide an energy density of 56 Wh kg^-1 at a power density of 750W kg^-1 and has 80%capacity retention and 100%Coulomb efficiency after 15,000 charges and discharges at a current density of 10 A g^-1.（2）A new composite of crystalline and amorphous,oxides and sulfides was designed.CoMoS₄@Co_xZn_1-xMoO₄ composites were prepared by simple hydrothermal and calcination treatments using bimetallic MOFs as self-supporting templates.The oxide can provide a high theoretical capacity,and the introduction of sulfide will reduce the energy gap width of the material and improve the electrical conductivity;the amorphous state can increase the reactive sites of the material and improve the charge/discharge rate,and the crystalline state can improve the stability of the material and inhibit the amorphous material from breaking in the redox process.This new combination can overcome the shortcomings of single component and better realize the synergistic effect between different components,to realize the efficient energy storage of supercapacitor.This heterogeneous structure exhibits 2369.7 F g^-1 specific capacity at a current density of 1 A g^-1.The assembled CMS-2:1//AC asymmetric supercapacitor has an energy density of 69.44 Wh kg^-1 at a power density of 781.2 W kg^-1.