Preparation And Electrochemical Properties Of Cobalt-based Vanadate Compounds As Electrode Materials

Energy crisis and greenhouse gases have seriously constrained the overall sustainable development of entire community.It is seen as one of the most effective ways to solve the above problems by storing renewable energy in the form of electric energy through energy storage devices?such as supercapacitors and lithium-ion batteries,and so on?.The research and development of electrode materials to a certain extent determine the commercial value and practical application of supercapacitors and lithium-ion batteries,so the most fundamental problem is to find or modify the materials with high electrochemical activity.In recent years,ternary transition metal oxides have become a research hotspot because of their high theoretical specific capacity,good conductivity,and the synergistic effect between different metals.These materials have shown great potential in the field of energy storage.Cobalt-based vanadate compounds do not appear to be as popular as other ternary transition metal oxide materials,because there are lack of suitable synthetic methods due to the variable valence of vanadium,the electrochemical mechanisms of them are unclear,and cycle stability still need to be improved,and so on.The vanadium and cobalt resources of China are very rich,but the comprehensive development and utilization is insufficient.Thus,translating the rich vanadium and cobalt resources into functional materials is a meaningful work.Based on the above analysis,the main contents of this paper are as follows:?1?The quasi-cuboidal CoV₂O₆ are synthesized by a microwave-assisted method followed by annealing.The Co?NO3?2·6H₂O and NH4VO3 act as raw materials,and deionized water acts as solvent.When the quasi-cuboidal CoV₂O₆ is used as positive electrode for supercapacitor,the as-prepared samples manifest a specific capacitance of 223 F g-1?1 A g-1?,well rate capability,and superior cycle stability retaining the total capacitance as the number of cycles reaches to 15,000?5 A g-1?.This work broadens the variety of supercapacitor materials and also promotes the development of cobaltbased vanadate compounds materials in the field of supercapacitors.?2?Cobalt-based vanadate compounds have attracted attention for their perfect electrochemical performance as electrode material of lithium-ion batteries,yet their synthetic method is often beset with severe challenges.In this chapter,we report a new strategy to synthesize hierarchical Co₃V₂O₈ mesoporous microspheres comprised of stacked nanoparticles via calcining the precursor obtained by a controllable coprecipitation of microspheres at room temperature.When evaluated as an anode material for lithium-ion batteries,the as-prepared samples manifest a high initial discharge capacity of 1099.0 mA h g-1 at 500 mA g-1,outstanding cycling retention rate of 100% after 200 cycles,and excellent rate capability with an average discharge capacity of 545.5 mA h g-1 at 2000 mA g-1.The reported synthetic procedure in this work is more energy-saving,facile,and straightforward than the synthesis approach reported by previous references.In addition,the structure of Co₃V₂O₈ can be controlled effectively in this procedure.?3?The three-dimensional flower-like Co₂V₂O₇·nH₂O is prepared by liquid synthesis method through controlling the parameters of the chemical reaction process.When the three-dimensional flower-like Co₂V₂O₇·nH₂O is used as positive electrode for supercapacitor,the as-prepared samples manifest a specific capacitance of 326.9 F g-1 at a current density of 1 A g-1.The rate capability of the three-dimensional flowerlike Co₂V₂O₇·nH₂O is also better,and the cycle stability retains 100% when the number of cycles reaches to 15,000?5 A g-1?.