Preparation And Electrochemical Properties Of Bismuth-Based Supercapacitor Electrode Materials

The rapid development of industrial production has made energy in short supply,accelerating the exploitation of fossil energy,which not only causing a sharp decline in the reserves of fossil energy,but also bringing environmental pollution,these has effectively promoted the development of new energy sources such as wind,water and electricity.However,the application of new energy is limited by the influence of time and space on the storage and transportation.Therefore,the development of high-performance energy storage devices has become a hot research topic in order to ensure efficient storage and stable output of the energy.As a new type of energy storage device,supercapacitor has great application prospects in the fields of renewable energy,transportation,and wearable portable devices due to its high power density,fast charge and discharge rates and stable cycle performance,which has attracted the attention of many researchers.Electrode materials as one of the key factors affecting the performance of supercapacitors and which are the research focus of the research community.The electrode materials currently studied include:carbon materials,conductive polymer materials,metal compounds,compared with carbon materials and conductive polymers,metal compounds have become an important research object of supercapacitor electrode materials due to their high specific capacitance.Bi-based compounds are favored by researchers because of their relatively abundant content in the earth's crust,wide sources and high theoretical specific capacitance.This article revolves around the Bi-based compounds,Bi₂O₃,Bi₂O₃/rGO and Bi₂MoO₆ were prepared,the phase structure and morphology of the material were characterized by means of XRD,EDS,SEM,Raman and other methods.The electrochemical properties of the materials were tested in a 6 mol·L^-11 KOH electrolyte with a three-electrode system and the effects of various factors on the electrochemical properties of the materials were investigated.The main work is as follows:?1?Using Bi?NO₃?₃·5H₂O as a bismuth source and Na₂CO₃ solution as a precipitant,the?BiO?₂CO₃ precursor was prepared in an aqueous solution at 60°C.The results of XRD and Raman show that the tetragonal?-Bi₂O₃ was obtained by calcination of?BiO?₂CO₃ at 400°C for 10 h.The monoclinic?-Bi₂O₃ was obtained by calcination at 500°C for 10 h.Cyclic voltammetry,galvanostatic charge and discharge,electrochemical impedance spectroscopy and cycle stability electrochemical tests show that crystal form is one of the factors affecting the electrochemical performance of materials and?-Bi₂O₃ has better electrical properties.?-Bi₂O₃ has a specific capacitance of 1266.3 F?g^-11 at a current density of 1 A?g^-1,and the specific capacitance of 1042.3 F?g^-11 when the current density is increased to 10 A?g^-1,the capacitance retention is 82.3%;After 500 cycles of charge and discharge at a current density of 5 A?g^-1,the specific capacitance can still maintain 76.0%.?2?Bi/rGO precursor was prepared by solvothermal method using dimethylformamide?DMF?as solvent,Bi?NO₃?₃·5H₂O and graphite oxide?GO?as raw materials.Bi/rGO was calcined in air to obtain Bi₂O₃/rGO composite.XRD and SEM results show that when the mass ratio of GO to Bi₂O₃ is 4:4,the reaction temperature is 180°C,and the calcination temperature is 350°C,Bi₂O₃ was uniformly distributed on the surface of rGO sheets.Electrochemical performance test results show that Bi₂O₃/rGO has a specific capacitance of753.1 F?g^-11 at a current density of 1 A?g^-1,and the specific capacitance is 654.5 F?g^-11 when the current density is increased to 10 A?g^-1,which indicates that Bi₂O₃/rGO composite has good rate performance.At 5 A?g^-11 current density,after 500 charge and discharge cycles the specific capacitance retention rate is 53.2%,after 1000 charge and discharge cycles,the specific capacitance retention rate is 39.0%,indicating that the cycle stability of the Bi₂O₃/rGO composite decays faster in the initial stage and then stabilizes.?3?Bi₂MoO₆ was prepared by hydrothermal method with Bi?NO₃?₃·5H₂O as the bismuth source and?NH₄?₆Mo₇O₂₄·4H₂O as the molybdenum source.XRD and SEM tests show that the sheet-like structure Bi₂MoO₆ was obtained at a hydrothermal reaction temperature of160°C and a hydrothermal reaction time of 18 h.The electrode prepared by using the sample as an active material was at 1 A·g^-11 current density,the specific capacitance is 956.0 F?g^-1,and the specific capacitance is 823.1 F?g^-11 when the current density added to 10 A?g^-1.Moreover,at 5 A·g^-11 current density,the specific capacitance retention rate is 75.4%after 500charge and discharge cycles.