Nb₂O₅ Carbon Composites Synthesis And Research On Lithium Electrical Properties

Lithium ion battery is an efficient and green renewable energy with the advantages of high energy density and good cycle life,which gradually becomes an effective substitute for traditional energ y.At present,lithium ion battery has been rapidly into all areas of life,but with the rapid development of portable electron ic devices and electric vehicles,these products put forward higher requirements for lithium ion battery about the safety,cycle life performance and charge and discharge speed.As a traditional anode material for lithium ion battery,graphite has not been able to meet the requirements of many electronic products and transportation equipment due to its low theoretical capacity and potential safety problem s.The development of electrode materials with high power density and high stable performance is the key to solve the present problems.In recent years,in the research of anode materials for lithium ion batteries,the transition metal oxide materials have attracted great attention from researchers.Many transition metal oxide materials have excellent lithium storage properties,and preparation process is simple,no pollution and low price,but low electronic conductivity restricts their high-speed charging and discharging performance.Therefore,the research idea of this paper is that composite transition metal oxides with carbon material to improve overall specific capacity and electrical conductivity,so as to improve the energy density and power density of the material.We regard Nb₂O₅ transition metal oxide as the main research object,through high temperature processing or hydrothermal preparation of Nb ₂O₅ and carbon composite materials,and the composite materials were served as negative electrode for lithium to explore their electrochemical performance.The main contents are as follows:（1）The development process of lithium ion battery,the working principle and construction are reviewed in detail,then the positive and negative materials of lithium ion battery are summarized,next the Nb₂O₅ structure and its application in lithium ion battery is introduced,lastly,the research ideas of this thesis are presented.（2）A simple grinding and annealing method was used to synthesize Nb ₂O₅@C composites and study the lithium electrical properties.The test results:at 50m A g^-1current density,compared with pure Nb₂O₅,Nb₂O₅@C composite material has good cycle stability with about 380m Ah g^-1 specific capacities after 100 cycles,and high rate performance.（3）Nb₂O₅ and Nb₂O₅@C flocculent nanosheet were prepared by hydrothermal method combined with high temperature annealing,and the active materials were used as a anode electrode of lithium ion battery to explore its electrochemical performance,The test shows that the lithium electrical properties of Nb ₂O₅ improved by regulating the laminar structure and carbon coating by PVP.In 100m A g^-1 current density,the attenuation of Nb₂O₅ is relatively severe,After 100 cycles,specific capacity attenuated to about 100m Ah g^-1.Nb₂O₅@C-1,Nb₂O₅@C-2 and Nb₂O₅@C-3composites flocculent nanosheets shows better lithium storage properties,especially,Nb₂O₅@C-3 shows the best performance of the cycle stability and charge and discharge rate,under the same current density,capacity retains in 160m Ah g^-1 after100 cycles.