Preparation And Electrochemical Performance Of Molybdate-based Composite Materials

As global energy consumption and environmental problems increase,the development of a low-cost,high-efficiency,and environment-friendly electrochemical energy storage device has become an urgent need for social progress.It is under this background that more and more researchers are studying many supercapacitors with good performance.It has been widely used in home office and other aspects.However,the performance of traditional carbon-based supercapacitors can not meet a large number of needs,therefore,the research on the development of high-performance supercapacitors has become the focus.Lately,molybdate has attracted widespread attention due to its electrochemical activity,multivalent state changes,low cost and natural abundance.Therefore,this article mainly focuses on the research of molybdate composite materials,and prepares electrochemical energy storage materials with excellent performance by constructing core-shell nanostructures.The contents and research conclusions of this paper are as follows:（1）Synthesis and electrochemical performance of CuO/CuO@Ni-CoMoO₄·0.75H₂O nanobelt arrays:we designed and synthesized Cu O/Cu O@Ni-Co Mo O₄?0.75H₂O NBs on Cu foam substrates with Cu O NBs as cores or extra freeway and Ni-Co Mo O₄?0.75H₂O nanobelt as shell by an easily synthetic method.Cu O NBs inside Ni-Co Mo O₄·0.75H₂O nanosheets and the parts of Cu O NBs without wrapped Ni-Co Mo O₄·0.75H₂O nanosheet directly grown on Cu foam will provide electron“superhighways”and extra outside freeway for charge storage and delivery.Besides,the Ni doped Co Mo O₄·0.75H₂O NBs are conducive to the electrical conductivity and open space among these nanosheets can act as an“ion reservoir”,the increment of active sites and the contribution of capacitive effects.Finally,the Cu O/Cu O@Ni-Co Mo O₄?0.75H₂O NBs directly grown on Cu foam could avoid the“dead”volume caused by the tedious process of mixing active materialswithpolymerbinders/conductiveadditives.Therefore,Cu O/Cu O@Ni-Co Mo O₄?0.75H₂O NBs exhibit a high area capacitance of 5.40 F cm^-2at 5 m A cm^-2and the excellent electrochemical stability（After 4000 cycles,the capacity retention rate of Cu O/Cu O@Ni-Co Mo O₄·0.75H₂O nanobelt arrays is 98.7%）.（2）Synthesis and electrochemical performance of NiMoO₄@CoWO₄core-shell array structure:we successfully synthesized Ni Mo O₄@Co WO₄core-shell nanostructures through hydrothermal process and annealing treatment.The synergistic effect of Ni Mo O₄and Co WO₄,Ni Mo O₄nanorods and Co WO₄can provide high porosity and good electrical conductivity,and have excellent electrochemical performance.In addition,the open space between these nanorods can act as an"ion pool",allowing the electrolyte to easily diffuse into the inner area of the electrode,and slowing down the volume expansion during the cycle.Finally,Ni Mo O₄@Co WO₄directly grown on Ni foam could avoid the“dead”volume caused by the tedious process of mixing active materials with polymer binders/conductive additives,which is conducive to charge transfer.Therefore,Ni Mo O₄@Co WO₄core-shell nanostructures exhibit a high area capacitance of of 5.53 F cm^-2at 5 m A cm^-2and the excellent electrochemical stability（After 4000 cycles,the capacity retention rate of Ni Mo O₄@Co WO₄core-shell nanostructures is 88.5%）.