Study On Synthesis And Electrochemical Properties Of Copper Vanadate

The application of clean energy makes a higher request for the next-generation storage system.Lithium-ion battery(LIB)shows its advantages and becomes one of the preferred device for large-scale energy storage systems.The lower capacity of LIB is considered to be the key factor for restricting its development.With their lamellar structure and multistep reduction properties,copper vanadates show an excellent properties in many fileds and present a broad prospect.But it is an pilot study to the electrochemical performance of copper vanadates.In this paper,different phases of copper vanadates were prepared by controlling the process parameters.The effects of preparation process on the composition,structure and electrochemical properties of materials are explored by X-ray diffraction,scanning electron microscopy,the charging and discharging equipment,cyclic voltammograms and impedance spectroscopy.The different phases of copper vanadates were synthesized by solid-state method.Influences of the calcination temperature,calcination time and molar ratio on the phase,morphology and performance of products were investigated.The crystalline and size of the products were improved with the increasing calcination temperature.The morphology were changed from particles to coral,and then to bulk.Moreover,the phase of Cu2V2O7 would change from a to β.The a-Cu2V2O7 was prepared by setting the molar radio of Cu and V as 1:1 with calcination at 600℃ for 2 h.It was coralliform and has a capacity of 370 mAh g-1 at 50 mA g-1.The reaction temperature and time would be decreased substantially by the use of Cu2O instead of CuO.Three-dimensional Cu3V2O7(OH)2·2H2O flowers were prepared by water bath method via using Cu2O as hard-template and copper source.The morphology and composition would be controlled by adjusting the reaction temperature and pH value.Compared with the pure phase,the mixture material of Cu3V2O7(OH)2-2H2O/Cu2O exhibit the better electrochemical performance.The sample synthesized at 70℃ for 5 h with pH=7.41 exhibits excellent cycling stability.It showed an initial discharge capacity of 941.3 mAh-g-1 at the current density of 100 mA-g-1,and kept the capacity of 414.7 mAh g-1 after 100 cycles.The mesoporous Cu2V2O7/reduced Graphene Oxide(Cu2V2O7/rGO)microspheres composite were prepared by low temperature hydrothermal method combined heat treatment.The influence of reaction tempreture,reaction time and rGO addition amount on structures and properties of producture were investigated.The sample synthesized at 60℃ for 20 h and the addition 0.6%rGO,with thermal treatment at 300℃ for 0.5 h,which shows an excellent cycling stability.At the current density of 100 mA-g’1,it showed the initial discharge capacity of 1245 mAh g-1,and kept the capacity of 900 mAh-g-1 after 100 cycles.They also exhibited superior rate capabilities with reversible capacities of 890,817,690,524,328 and 170 mAh g-1 at the current density of 100,200,500,1000,2000 and 5000 mA-g-1,respectively.The performance was much better the pure Cu2V2O7.These excellent electrochemical properties may be attributed to the unique structures and the synergistic energy storage effect of rGO and Cu2V2O7.