Preparation And Modification Investigation For Chromium Niobium Based Compound

In recent years,titanium niobium oxides,as anode material for lithium ion batteries,have attracted extensive attention with excellent performance.However,these compounds are also limited in practical applications due to their low electronic conductivity.In this paper,we successfully synthesized CrNb₄₉O₁₂₄ nanofibers with different morphologies by electrospinning.CrNb₄₉O₁₂₄ has similar advantages to titanium niobium oxides?such as high theoretical specific capacity and similar plateau range?but higher electric conductivity,which shows excellent long cycle life and high rate capacity.In addition,we also studied the effects of different solvents on the morphology of CrNb₄₉O₁₂₄ nanofibers,and further explored the electrochemical properties and lithium storage mechanism of CrNb₄₉O₁₂₄ nanofibers by means of modification.The specific contents are as follows:In the first part,the synthesis and lithium storage mechanism of one-dimensional CrNb₄₉O₁₂₄nanomaterials were investigated.In this chapter,electrospinning technique and solid-state reaction were used.The electrospun precursor obtained by electrospinning and the precursor obtained by ball grinding were calcined in muffle furnace,and one-dimensional CrNb₄₉O₁₂₄ nanotubes and bulk CrNb₄₉O₁₂₄ can be obtained.Next,testing methods such as XRD,SEM,TEM,EDX mapping and XPS measurements were studied.In addition,it shows that CrNb₄₉O₁₂₄ nanotubes exhibited better electrochemical properties than that of the bulk CrNb₄₉O₁₂₄.Finally,in-situ XRD technology is utilized to explore the lithium storage mechanism of CrNb₄₉O₁₂₄ nanotubes.The second part explored the influence of different solvents on the morphology of CrNb₄₉O₁₂₄nanofibers under other same conditions.And then the modification of CrNb₄₉O₁₂₄ nanowires is studied.Ethanol and N,N-dimethylformamide?DMF?,two different solvents,were used in the electrospinning.The nanofibers with different nanometer sizes could be obtained when the electrospun precursors were calcinated in muffle furnace.Then,they were nitrided in a tubular furnace that filled with N2 atmosphere.It showed that when the nitriding time was 25 min,CrNb₄₉O₁₂₄ nanofibers exhibited the best electrochemical properties.Finally,in-situ XRD and ex-situ XPS measurements were employed to further explore the insertion and extraction process of Li⁺in CrNb₄₉O₁₂₄.Therefore,a possible lithium storage mechanism can be obtained.