Preparation And Electrochemical Performance Of Niobium-based Composite Oxide Anode Materials

With the continuous development of human society and science and technology,human demand for energy is increasing day by day.After long-term development,lithium-ion batteries have shown great advantages in daily production and energy storage.Transition metal oxide cathode materials have attracted much attention because of their high specific energy and stable chemical properties during charge and discharge.Among them,niob-based oxides Nb₂O₅ and VNb₉O₂₅ have a series of advantages such as rapid reaction,good reversibility and high safety performance,and are potential cathode materials for batteries.However,the low electrical conductivity of these materials limits their application in real life.Therefore,based on the hydrothermal method,the doping modification and morphology construction of the materials were studied.W/Nb₂O₅ battery materials,Mo/Nb₂O₅ battery materials and VNb₉O₂₅battery materials were prepared,respectively.Moreover,a series of systematic researches were carried out on the synthesized materials.The main research contents are as follows:W/HNb₃O₈ precursor was synthesized simply by hydrothermal method using commercial NbCl₅ and WCl₆ as niobium and tungsten source,respectively.The results show that the electrochemical properties of W/Nb₂O₅ materials are better than those of pure Nb₂O₅ materials.In the voltage range of 1.0?3.0 V,the first discharge capacity is 256.2 mAh g^-1.When the current density is 0.1,0.2,0.4,1,2 and 5A g^-1,the stable discharge capacity is 224.9,206.3,191.6,169.7,151.3 and 97.4 mAh g^-1,respectively.After charging and discharging 200 times under the current density of 1 A g^-1,the capacity retention rate is 82.1%.The results show that the W/Nb₂O₅ has better multiplier performance and cycle stability.Using commercial NbCl₅ as niobium source and MoCl₅ as molybdenum source,Mo/HNb₃O₈ precursors with different Mo⁶⁺doping amounts were synthesized by the simple hydrothermal method.Mo/Nb₂O₅ materials with different Mo⁶⁺doping amounts were calcined at 700?in air.The results show that when the molar ratio of Mo⁶⁺and Nb⁵⁺is 1:19,the material has better multiplier performance and cycle stability.In the voltage range of 1.0?3.0V,the first discharge capacity is 243.5 mAh g^-1.When the current density is 0.1,0.2,0.4,1,2and 5 A g^-1,the stable discharge capacity is 217.2,197.9,183.9,170.8,158.7 and 106.3 mAh g^-1,respectively.At the current density of 0.2A g^-1,the capacity retention rate was 73.8%after charging and discharging 200 times.Using commercial NbCl₅ as niobium source and C₁₀H₁₄O₅V as vanadium source,V/HNb₃O₈ precursor was synthesized by the simple hydrothermal method.VNb₉O₂₅nanometer sheet material was obtained by acalcining V/HNb₃O₈ precursor at 400?in air.VNb₉O₂₅ nanometer rod material was obtained by acalcining V/HNb₃O₈ precursor at 700?in air.The results show that the electrochemical properties of VNb₉O₂₅ nanometer sheet material are better than that of VNb₉O₂₅ nanometer rod.In the voltage range of 1.0?3.0 V,the first discharge capacity is 337.1 mAh g^-1,and the stable discharge capacity is 261.1,244.3,227.3,205.5,179.5 and 126.8mAh g^-1,respectively,when the current density is 0.1,0.2,0.4,1,2 and 5A g^-1.After charging and discharging 1000 times under the current density of 2 A g^-1,the capacity retention rate is still 86.7%.The results show that the synthesized VNb₉O₂₅nanometer sheet material has excellent multiplier performance and cyclic stability.