Microwave-assisted Synthesis Of Vanadium-based Metal Oxides And The Investigation Of Their Pseudocapacitive Performance

Recent years,scientists have made gratifying achievements in the exploration and discovery of sustainable energy,and the manufacture and development of new energy storage equipments.The research progress of supercapacitors and their electrode materials is also in full swing.Metal and bimetallic oxides with high specific capacitance is a kind of well-known supercapacitor electrode materials,which has a broad prospect.Seeking for efficient and environmentally friendly synthesis methods,and constantly exploring the synthesis of novel metal and bimetallic oxides with different morphologies and types are very important for the research of supercapacitor electrode materials.In this paper,CoV₂O₆?Co₃V₂O₈?Zn₃?OH?₂V₂O₇·2H₂O and Zn₂V₂O₇fourvanadium-basedmetalcompoundswerepreparedby microwave-assisted hydrothermal method,and their pseudocapacitive properties as supercapacitor electrode materials were also explored.?1?Microwave-assisted hydrothermal method was used to prepare CoV₂O₆micro-bulk rapidly.Subsequently,Co₃V₂O₈ nanoparticles were obtained by adjusting the pH=10 at the same reaction temperature and time.After the characterization of XRD,XPS,SEM and TEM,it shown that the effect of temperature on the synthesis of two products wasn't obvious,but the pH of the solution had a significant influence on the types and morphologies of the synthesized products.The electrochemical properties test in three-electrode system showed the specific capacitance of Co₃V₂O₈(319.4 F g^-1,at 1 mA cm^-2)was much higher than that of CoV₂O₆(228.1 F g^-1,at 1mA cm^-2),and the capacitance retention after 1000 cycles of Co₃V₂O₈ nanoparticles?94.67%?was higher,too.In comparison,the synthesized Co₃V₂O₈ showed better pseudocapacitance performance and deserved further study.?2?Under microwave-assisted conditions,through the control of reaction temperature,time and the addition of the surfactant glycine,Zn₃?OH?₂V₂O₇·2H₂O nanowires and tightly connected Zn₂V₂O₇ elliptical nanoparticles were first synthesized and used as electrode materials in the supercapacitors for electrochemical properties test.The test results showed that the addition and selection of surfactant were important for the species and morphologies of the products.The specific capacitance(427.7 F g^-1,at 1 mA cm^-2)and cycling performance(after 1000 cycles retained 83.71%,at 2 mA cm^-2)of the synthesized Zn₂V₂O₇ were excellent.In addition,the Zn₂V₂O₇ electrode materials have also been used in the Zn₂V₂O₇//AC asymmetric supercapacitors for the first time and reached 18.7 W h kg^-1 at a power density of 272.7 W kg^-1,which was a breakthrough in the research field of electrode materials.