Preparation And Electrochemical Performance Investigation For Niobium Tungstate

In recent years,Nb-based oxides have been considered as promising anode materials for lithium-ion batteries due to their relatively high lithium ion insertion/extraction voltage and special capacity.Among them,titanium-niobium oxides?Ti-Nb-O?have been widely reported to use as anode materials for lithium-ion batteries,TiNb2O7 is the most attractive and the most prominent.Studies show that TiNb₂O₇ has good structural stability and electrochemical reversibility during lithiation/delithiation process.Tungsten-niobium oxides as another Nb-based oxides have similar crystal structure to TiNb₂O₇,but their electrochemical properties and lithium storage mechanism are scarcely reported in the literatures.Therefore,for the first time,the facile electrospinning is developed to prepare one-dimensional WNb₁₂O₃₃,W₉Nb₈O₄₇,and W₃Nb₁₄O₄₄ nanomaterials in this study.In addition,their electrochemical properties and lithium storage mechanism are investigated in detail.Detailed contents are as follows:Firstly,the fabrication and lithium storage mechanism of one-dimensional WNb₁₂O₃₃nanomaterials were investigated.Two different types of collectors?stainless steel net and rounded roller?were used to spinning.Then one-dimensional composites were calcined in a muffle furnace under an air atmosphere to acquire one-dimensional WNb₁₂O₃₃3 nanomaterials.And then they were investigated via XRD,SEM,TEM,and EDX mapping tests.The electrochemical tests showed that compared with WNb₁₂O₃₃ nanorods,WNb₁₂O₃₃ nanowires possessed more outstanding performance.Finally,the mechanism of lithium storage of WNb₁₂O₃₃ nanowires was studied by in-situ XRD technique.Secondly,the fabrication,modification and lithium storage mechanism of one-dimensional W₉Nb₈O₄₇ nanofibers were studied.The electrospinning was used to prepare one-dimensional W₉Nb₈O₄₇ nanofibers.Then the nitridation treatment was conducted and conductive W₉Nb₈N₂₂bumps were introduced on the surface.After that the effect of different nitridation time on its structure,morphology and electrochemical properties was investigated.The results showed that W₉Nb₈O₄₇ nanofibers exhibited the best structural stability and electrochemical properties after treatment for 20 min.In the end,the mechanism of lithium storage was studied by in-situ XRD technique.Thirdly,the fabrication and lithium storage mechanism of one-dimensional W₃Nb₁₄O₄₄nanowires were studied.The electrospinning was used to prepare precursor nanofibers.After calcination,the one-dimensional W₃Nb₁₄O₄₄4 nanowires were obtained.And then a series of chemical characterizations and electrochemical tests were conducted.In addition,in-situ XRD and ex-situ XPS techniques were also used to deeply investigate lithium ion insertion/extraction process in W₃Nb₁₄O₄₄4 structure.A possible lithium storage mechanism for W₃Nb₁₄O₄₄4 nanowires was proposed.