Preparation Of Mo-based Composite Electrode Material And Research On Its Capacitance Characteristics

In recent years,due to the need to protect natural resources and regulate global energy consumption,the demand for the development of clean energy is crucial.Therefore,energy storage devices that are environmentally friendly and have high energy storage efficiency are particularly important.Thus,the supercapacitors(SCs)probably become the newborn generation of vital energy storage systems,owing to its high specific power,superior cycle life and fast charge discharge rate.As we all know,the key to the excellent-performance SCs is the structure and composition of the electrode material.Hence,the development of electrode materials with fast electron/ion transfer characteristics and high specific capacitance to improve the overall performance of SCs is still an urgent need for researchers.The metal molybdenum-based electrode material has the advantages of high conductivity,high theoretical specific capacitance and environmental friendliness,a wide range of raw materials,and a variety of oxidation states and abundant active sites.However,the important factors that limit the development of practical applications of molybdenum-based electrode materials are low rate performance and poor cycle stability.Therefore,this article mainly explores several methods that can enhance the electrochemical performance of supercapacitor electrode materials.Through nanocomposite of carbon materials,conductive polymers and molybdenum-based compounds,and in-situ growth of molybdenum-based binary metal compounds,which make various types of materials have synergistic effect,complementary advantages to prepare composite electrode materials with excellent performance in all aspects.The main research contents are as follows:(1)Using ammonium molybdate,pyrrole and graphene oxide as raw materials,three dimensional(3D)interconnected molybdenum trioxide(Mo O₃)/polypyrrole(PPy)/reduced graphene(r GO)composites were obtained by a simple three-step method.Use various characterization technologies such as FTIR,SEM,XPS,etc.to characterize and analyze the structure of the material,and conduct electrochemical tests.Due to the synergy of the three materials,the prepared new electrode material has reduced internal resistance and increased conductivity.It shows a higher specific capacity(412.3 F g^-1)at a current density of 0.5 A g^-1,which is higher than that of any single component material,and has good cycle stability:under the condition of 2 A g^-1,85.1%is still maintained after 6000 cycles.Moreover,symmetrical supercapacitors based on Mo O₃/PPy/r GO electrodes perform outstanding energy density:19.8 Wh Kg^-1 at a power density of 301 W Kg^-1.(2)Using ammonium molybdate and cobalt chloride as raw materials and carbon cloth(CC)as supporting materials,a simple and effective method was developed to prepare Co Mo O₄@CC material with the microstructure of petal clusters,and used as a binder-free SCs electrode.Various characterization methods are used to characterize and analyze the structure of the material.Due to the increase of active sites for the electrochemical redox reaction of the Mo-Co alloy and there is no need to add any polymer binders,the specific capacitance and stability of the electrode material has been greatly improved.Electrochemical tests show that Co Mo O₄@CC material exhibits eminent specific capacitance(664 Fg^-1 at a current density of 1 Ag^-1)and satisfactory working stability(capacitance remains at 84%after 1000 times of continuous work).The constructed Co Mo O₄@CC||Co Mo O₄@CC two-electrode device has a high energy density of 27 Wh kg^-1(power density of 600 W kg^-1),and under high power density(6022 W kg^-1),it still has a good energy density(18.4 Wh kg^-1).(3)Using ammonium molybdate and stannous chloride as raw materials and carbon cloth(CC)as the base,uniform and orderly molybdenum tin alloy nanoparticles are grown on the surface of the carbon cloth through a simple hydrothermal and annealing process.Carbon cloth can be used as an electronic conductor to connect tin-molybdenum oxide nanoparticles to form a good conductive contact point inside the electrode.Similarly,Sn(Mo O₄)₂ bimetallic oxide nanoparticles formed by Sn-Mo can also provide more active sites for the redox reaction during charge and discharge.Structural characterization and electrochemical test results illustrate that the Sn(Mo O₄)₂ electrode material represents the largest specific capacitance(433 Fg^-1 at a current density of 1 Ag^-1),excellent rate capability and excellent working stability(the capacitance remains at 83%after 6000continuous work).The energy density of two-electrode device after assembly can achieve an energy density of 17.5 Wh kg^-1 in the circumstances of lower power density(600 W kg^-1),and under high power density(5985 W kg^-1),it still has a good energy density(13.3Wh kg^-1).