Research On Preparation And Doping Modification Of Lithium Titanate As Anode Materials For Lithium Ion Batteries

Spinel lithium titanate(Li4Tis012)has excellent cycle performance and long cycle life as anode materials for lithium ion batteries,because of its zero strain characteristics.And lithium titanate has a higher working voltage platform(1.5-1.6 V vs.Li/Li+),the platform is long and stable.It can adequately avert the formation of SEI film.At the same time,it can also effectively avoid safety problems caused by lithium dendrites.Therefore,it is considered to be very promising to replace carbon materials and become the anode materials of the next generation lithium ion batteries.The low electrical conductivity(10-13 S/cm)of Li4Ti5O12 limits its practical application.This problem can be improved by preparing special morphology,doping or coating methods.Firstly,pure phase Li4Ti5O12 with porous spherical morphology was prepared by sodium hydroxide etching in this paper.And explore the effect of NaOH concentration,hydrothermal temperature and hydrothermal time on the product.The results show that the Li4Ti5O12 with the NaOH concentration of 15 mol/L,hydrothermal temperature of 150? and hydrothermal time of 12 h has the best electrochemical performance.At 0.5 C,the initial discharge capacity of Li4TisO12 electrode was 161.9 mAh/g and still maintained 127.2 mAh/g after 300 cycles,corresponding to a capacity retention rate was up to 78.3%.At 10 C,the initial discharge capacity of Li4Ti5O12 electrode was 125.2 mAh/g and still maintained 95.4 mAh/g after 1000 cycles,corresponding to a capacity retention rate was up to 76.2%.Secondly,using a one-step hydrothermal method to prepare pure phase Li4Ti5O12,and explore the effect of hydrothermal temperature,hydrothermal time and calcination temperature on the product.The results show that Li4Ti5O12 prepared with hydrothermal temperature of 180?,hydrothermal time of 12h and calcination temperature of 700? has the best electrochemical performance.At 0.5 C,the initial discharge capacity of Li4Tis012 electrode was 184.2 mAh/g and still maintained 152.4 mAh/g after 300 cycles.At 20 C,the initial discharge capacity of Li4Ti5O12 electrode was 126.3 mAh/g and still maintained 107.8 mAh/g after 1000 cycles.Thirdly,Li4Ti5-xCoxO12 and Li4Ti5-xNbxO12 samples were prepared by hydrothermal method.Explore the effects of Co doping and Nb doping on Li4Ti5O12.The results show that Co2+and Nb5+doping can improve the electrochemical performance of Li4Ti5012.The initial discharge capacity of Li4Ti4.8Co0.2O12 was 220 mAh/g and remained 169.4 mAh/g after 300 cycles at 0.5C,The specific discharge capacity after 1000 cycles at 20 C is 123.1mAh/g;The initial discharge capacity of Li4Ti4.9Nb0.1O12 was 186.5 mAh/g and remained 163.4 mAh/g after 300 cycles at 0.5C,The specific discharge capacity after 1000 cycles at 20C is 112.1 mAh/g.