| With the popularization of electronic equipment and the rapid development of electric vehicle industry,secondary energy storage has received great attention.The anode material is one of the important factors determining the overall performance of batteries.However,the traditional commercial graphite anode cannot be used in the field of electric vehicles due to its poor high rate performance and low safety and stability.As the representative of "zero-strain"materials,Li4Ti5O12 meets the demand of rapid charging and discharging,but its low theoretical capacity and high price limit its application.Therefore,the key to solve the problem is to find cheap anode materials with high specific capacity and high cyclic stability.The theoretical specific capacity and cycling stability of TiO2(one of Ti-based oxides)could meet the requirements of secondary power batteries.But the cost of TiO2 commonly used in the lab is still high.This article uses commercial TiO2(c-TiO2)as the raw material to solve the problem of high cost,but its low electronic conductivity is another obstacle to its application.In order to solve the above problems,this article mainly carried out the following research:(1)c-TiO2 was added into aqueous solution of citric acid,stirred and dried to obtain a precursor.The precursor was then carbonized at 750? to obtain uniform few-layered carbon-coating around c-TiO2 particles.When the mass ratio of citric acid to c-TiO2 is 0.3,the sample shows excellent rate performance and long-cycle stability.At a current density of 1.5 A g-1,the reversible capacity is as high as 133.7 mA h g-1,and the reversible capacity is 160 mA h g-1 after 1000 cycles at 0.5 A g-1.After structural characterization and electrochemical analysis,the high rate performance and cycle stability benefitted from the formation of the uniform thin carbon layers,which effectively improved the electronic conductivity and avoided the reduction of ionic conductivity resulted from redundant carbon,thereby effectively improving the electrochemical performance of c-TiO2.(2)c-TiO2 was added into the aqueous solution of Zn(NO3)2,stirred uniformly,and then calcined at 600? to obtain TiO2/Zn2Ti3O8 composite.Then the composite was put into citric acid solution,stirred uniformly,and carbonized at 750? to prepare carbon-coated TiO2/Zn2Ti3O8.The modified TiO2/Zn2Ti3O8/C anode material showed excellent electrochemical performance.When Zn:Ti(molar ratio)is 0.4 and citric acid:TiO2/Zn22Ti3O8(mass ratio)is 0.3,the reversible capacity is 294.4 mA h g-1.In addition,after 1000 cycles at 0.5 A g-1,the cycling capacity was as high as 226.4 mA h g-1.Through systematic structural characterization and electrochemical analysis,Zn2Ti3O8 with defective spinel structure is conducive to Li+diffusion.Furthermore,a large number of interfaces were introduced to facilitate interfacial lithium storage.The electronic conductivity of the material was effectively improved by the carbon coating,and the electrochemical performance was significantly improved.(3)TiO2/Zn2Ti3O8 dual-phase composite and polyacrylonitrile(PAN)with different weight ratios were mixed uniformly and dried,then carbonized at 780? to obtain N and Zn co-doped carbon-coated TiO2 anode material for exploring sodium storage performance.When PAN:TiO2/Zn2Ti3O8=0.4(mass ratio),the reversible capacity at 20 mA g-1 is up to 234.9 mA h g-1,and the reversible capacity is still up to 177.5 mA h g-1 after 800 cycles at 1 A g-1.Combined with electrochemical performance and structural analysis,the N-doped carbon layers could improve the electronic conductivity of the material.Zn2+was doped into TiO2 lattice with the introduction of oxygen vacancy,increasing surface defects and conducive to ion diffusion and storage. |
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