Preparation And Performance Study Of V₂O₅ Microspheres By Spray Pyrolysis

Vanadium oxide?V₂O₅?microspheres are widely used in supercapacitors,lithium-ion batteries,catalysts and gas sensors due to their unique properties such as high specific energy,special layered structure,high stability,electrochemical activity and excellent thermoelectric properties.Spray pyrolysis technique is a relatively simple process,one-step molding,the good control of stoichiometry and scalable approach for producing high purity metal oxide powder,and it has inestimable industrial value in the synthesis of metal oxide powder materials.The hollow V₂O₅ microspheres were prepared on a large scale by spray pyrolysis using a mixture of ammonium metavanadate and dilute ammonia as precursor solutions.Simultaneously,the effects of the thermal decomposition temperature,precursor solution concentration,liquid feed rate,and heat treatment process conditions on the morphology,crystallinity,particle size and distribution of the product were investigated in detail.The results indicated that high thermal decomposition temperature,low precursor solution concentration and suitable feed rate were favorable for the preparation of better V₂O₅ microspheres,and massive V₂O₅ microspheres with smooth surface,hollow cavity and uniform particle sizes?0.4-1.5?m?were synthesized by a facile spray pyrolysis process with the temperature of 800°C,the precursor solution of 0.017 mol L^-1 and 10 ml min^-11 fluid intake rate.In order to obtain V₂O₅ hollow microspheres with complete crystal structure,high crystallinity,regular powder particle morphology and high specific surface area,the V₂O₅ microspheres prepared under optimal conditions were calcined at 300°C,500°C and 600°C for 3 h under nitrogen?N₂?atmosphere,respectively.The particles treated at 300°C and 500°C maintained the spherical shape and micron size of as-prepared particles,but the surface morphology became rough.Post-treatment at predefined temperatures?500°C?effectively turned the microsphere shell into stacked nanorods with widths of 100 nm and lengths of 500 nm,with enhanced crystallinity.The micro-morphology and structure of the V₂O₅ microspheres had been destroyed when post-treated at600°C.Therefore,post-treatment temperature of 500°C is the optimum temperature for post-treating V₂O₅ hollow microspheres prepared by sprays pyrolysis.When applied as cathode materials for supercapacitors,for different electrolyte solutions,V₂O₅ microspheres showed good capacitive behavior under the LiNO₃ electrolyte solution;for different post-treatment temperatures,the post-treated V₂O₅ microspheres at 500°C exhibited improved specific capacitance and longer discharge time;regarding the effect of electrolyte concentration,it was observed that 5M of LiNO₃ could give the best performance within the tested electrolyte concentration range from 1 to 5M.This is an effective method to manufacture massive V₂O₅ microspheres with tailored structure and potential applications in high performance energy storage materials.