Study On The Preparation Of V₂O₅ Electrode Material By Supercritical Fluid

Supercritical solvent heat has been widely used in the preparation of nanometer particles due to its simple,efficient and rapid reaction process.Compared with conventional hydrothermal/solute thermal,the experimental period of supercritical hydrothermal/solute thermal is short,the reaction parameters such as temperature and pressure are controllable,and the product is formed well with small particle size and uniform particle distribution,which will become one of the mainstream preparation methods of nanomaterials in the future..Among many cathode materials for lithium-ion batteries,vanadium pentoxide has a high theoretical specific capacity.Nanostructured vanadium pentoxide can shorten the charge transfer path,thereby significantly improving its charge transfer efficiency,and the existing synthesis and improvement methods have complicated reaction steps and long reaction time,and use supercritical solvothermal technology to prepare vanadium pentoxide And there are few reports about the construction of crystallization kinetic model.In this paper,supercritical solvothermal combined with subsequent calcination process was used to prepare vanadium pentoxide particles.Using supercritical ethanol as the medium,the effects of reaction temperature,reaction pressure and vanadium pentoxide dosage on the sample particles were systematically studied.The main work is as follows:(1)A supercritical solvothermal synthesis process was established,and spherical vanadium pentoxide and vanadium pentoxide nanosheets assembled from nanosheets were prepared.In order to obtain particles with small particle size,good crystallinity,and uniform size distribution,a single factor was adopted.The experimental system studied the influence of reaction temperature,pressure and vanadium pentoxide dosage on the sample,and obtained the best preparation process of two morphologies of vanadium pentoxide particles.(2)The optimal preparation conditions for spherical vanadium pentoxide are: 0.7 g of vanadium pentoxide,supercritical solvothermal reaction temperature 250 ?,pressure 13 MPa,subsequent calcination temperature 400 ?,calcination time 2 h;The optimal preparation conditions of vanadium oxide nanosheets are: vanadium pentoxide dosage 0.6 g,supercritical solvothermal reaction temperature 250 ?,pressure 13 MPa,subsequent calcination temperature 400 ?,calcination time 2 h.(3)The crystallization kinetic model of supercritical solvothermal preparation of vanadium pentoxide was established,and the effects of different reaction time,reaction pressure and vanadium pentoxide dosage on growth rate G and nucleation rate B were studied,and the growth was obtained.The change of the rate G and the nucleation rate B with different reaction conditions proves that the growth process of vanadium pentoxide crystals in supercritical solvothermal conforms to the law of ?L and shows growth independent of particle size.Under different reaction conditions,the two The crystallization of all kinds of morphological particles is mainly based on the process of crystal nucleation,and the growth rate and nucleation rate are sensitive to the changes of the experimental parameters,and the variation trend is opposite with experimental parameters,The prediction results of the kinetic model are consistent with the experimental test results.