The Preparation And Electrochemical Performance Of The Chromium Oxide-based Anode Material With Multi-level Structure

In this thesis,by using a simple and green synthesis method,three kinds of hierarchically structured nanomaterials were successfully prepared,including conductive carbon evenly coated Cr₂O₃/C spherical composites,porous hierarchical Cr₂O₃/C composites constructed by interwoven micro-fibers and conductive polymer polyaniline coated hierarchical Cr2O3/PANI materials.The morphology,microstructure,stability and lithium storage performance of the above materials were studied in detail.The main results are as follows:1)Using acetylacetone chromium as chromium source and glucose as carbon source,Cr₂O₃/C microspheres composites were prepared through single-step solvothermal method with ethanol as the solvent combined with calcination in nitrogen.Microspheres are constructed by nanoparticles with an average size around 50 nm,the conductive carbon not only uniformly coats on the surface of nanoparticles,but also fills among particles to form the uniform conductive network.Compared with pure phase Cr₂O₃ microspheres,the Cr₂O₃/C composites exhibit a certain improvement in the cycle performance and rate performance:under the current density of 100 mA g^-1,after50 cycles,the reversible specific capacity is kept 826 mA h g^-1,under the current density of 1000 mA g^-1,after 20 cycles,the reversible specific capacity is kept 403 mA h g^-1,which is much higher than the capacity of pure phase of Cr₂O₃ spheres under the same conditions.2)Porous hierarchical Cr₂O₃/N-doped carbon composites constructed by interwoven micro-fibers were synthesized using eggshell membrane as the template and the carbon source,Cr（NO₃）₃·9H₂O as chromium source,through a simple impregnation reaction combined with heat treatment process in nitrogen.The diameter of the fiber is between 0.3¹.0μm,the Cr₂O₃ nanoparticles,with average diameter about 20 nm,are attached on the fiber surface.The hierarchical Cr₂O₃/C composites show excellent electrochemical performance:under the current density of 100 mA g^-1,after 100 cycles,the discharge capacity remains steady at 640 mA h g^-1,even under the current density of1000 mA g^-1,after more cycles the discharge specific capacity is still as high as 368 mA h g^-1.3)The conductive polymer polyaniline coated hierarchical Cr₂O₃/PANI materials were obtained by using pure phase porous microspheres Cr₂O₃ and aniline as raw materials.The composites exhibit excellent properties of lithium storage.Under the current density of 500 and 1000 mA g^-1,after 50 cycles,the discharge specific capacities are 504 and 388 mA h g^-11 respectively,which is much higher than that of the pure Cr₂O₃ microspheres.It indicates excellent rate performance of such hierarchical Cr₂O₃/PANI composites.