Controlled Synthesis And Electrochemical Properties Of Niobium-based Oxides

In recent years,with the rise of electric vehicles such as Tesla and NIO,and the growing popularity of super-fast charging technology for portable electronics,the fast-growing market places higher demands on the lithium-ion battery:high power density,high capacity,as well as better safety and excellent cyclicity.At present,the negative electrode material has become a shortboard to enhance energy density.The specific capacity of the commonly used graphite material has reached 360 m Ah g^-1,close to its theoretical capacity(372 m Ah g^-1).It is difficult to make any further breakthrough,therefore,the development of new negative electrode materials with high energy density has been put on the agenda.Compared with the traditional graphite anode,the hot silicon-carbon materials in recent years will have the formation of lithium dendrite because of the lower intercalation potential.In contrast,lithium titanate has high operating voltage,excellent rate performance and zero volumetric strain during cycling,but its low theoretical capacity limits its practical application.The niobium-based material can avoid the hidden trouble caused by SEI film and Li Dendrite at the working voltage of about 1.5 V.similar to lithium titanate,niobium-based material has excellent fast charging performance,the theoretical and practical capacity of Nb₂O₅ is much higher than that of lithium titanate.Niobium-based materials based on Li₄Ti₅O₁₂ are also considered as“The next tuyere of electrode materials”.At present,niobium-based materials are based on Nb₂O₅ element doping,carbon coating,micro-morphology control and oxygen vacancy modification.In this paper,a new type of niobium phosphate material P₄Nb₂O₁₅was prepared by a simple solvothermal method.The specific morphology is micron and sub-micron irregular blocks.Compared with the more researched PNb₉O₂₅,this new type of niobium phosphate material P₄Nb₂O₁₅ has a capacity There has been a substantial improvement.In order to improve the conductivity of the material P₄Nb₂O₁₅,we added a small amount of carbon nanotubes in the synthesis of the precursor,which showed extremely excellent electrochemical performance,including a high actual capacity of 563 m Ah g^-1(under 0.1C),Excellent rate performance(at 50 C)and excellent cycle performance(in 500 cycles at10 C,only 0.0178%of the capacity is lost per cycle)Significant intercalation pseudo-capacitive contribution(88.5%at 1.0 m V s^-1))All these advantages show that P₄Nb₂O₁₅@CNTs has broad prospects as a negative electrode material for lithium-ion batteries.In this paper,the material Mo₃Nb₂O₁₄-L was prepared by in-situ coated carbon,compared with Mo₃Nb₂O₁₄-B directly synthesized after ball milling and annealing.The electrochemical performance of the material Mo₃Nb₂O₁₄-L has been greatly improved.The specific capacity at 0.1 C is 461 m Ah g^-1,which is 65 m Ah g^-1 higher than Mo₃Nb₂O₁₄-B.After cycling for 100 cycles at a high current density of 10 C,the capacity retention rate of the material Mo₃Nb₂O₁₄-L reached an astonishing 99.07%,while the retention rate of Mo₃Nb₂O₁₄-B was only 73.5%.Under the same magnification,the capacity retention rate under 1 C For long cycles,the capacity retention rate of the material Mo₃Nb₂O₁₄-L is also above 90%.It shows that the modification of in-situ carbon coating significantly improves the performance.