Synthesis And Modification Research Of Ti-based Composite As Anode Materials For Lithium Ion Batteries

Ti-based anode materials have been attracted much attention due to high safety,long cycle life and environmental friendliness.However,the low conductivity limits its further application.Sol-gel method has the merits of lower reaction temperature/short reaction time and the preparation of material with smaller particle size,evenly distribution and good electrochemical properties due to the raw materials mixed at atomic level.We synthesized Li₂ZnTi₃O₈?Li₄Ti₅O₁₂ and Li₂Na₂Ti₆O₁₄ via sol-gel method.The crystal structure,morphology,particle size,distribution and electrochemical properties of resultant anode materials were investigated.The optimal synthesis conditions are investigated.Besides,modification means such as doping and coating are also used to improve their electrochemical properties.The sol-gel method is used to prepare Li₂ZnTi₃O₈ material.After investigations of the different synthesis factors,the optimal conditions are obtained and the synthesis parameters are shown in the following: the optimal molar ratio of chelating agent to transition metal ions is 1.5,the preheating time and temperature are 4 h and 350 oC,the calcination time and temperature are 9 h and 750 oC.The effects of glucose pyrolytic carbon coating and Cu2+ doping on the on the structure,morphology,particle size,distribution and electrochemical properties of resultant anode materials were investigated.The Li₂ZnTi₃O₈-3 wt.%C deliver the best electrochemical performances.The initial charge capacity is 228mAh·g-1 under the current density of500mAg-1.Besides,Cu2+ doping can enhance its specific capacity and cycle performance due to increasing lattice constant and decreasing the particel size.Li₂Zn_0.6Cu_0.4Ti₃O₈ can deliver the initial charge capacity of 261.7mAhg-1.The sol-gel method is used to prepare Li₄Ti₅O₁₂ material.After investigations of the different synthesis factors,the optimal conditions are obtained and the synthesis parameters are shown in the following: the optimal calcination temperature and time are 800 o C and 10 h.The initial charge capacity is 172.2 mAh·g-1,and 165.3 mAh·g-1are kept after 50 cycles.The effects of TiO₂ coating and Ni2+ doping on the structure,morphology,particle size,distribution and electrochemical properties of resultant anode materials were investigated.The Li₄Ti₅O₁₂-3 wt.% TiO₂ deliver the best electrochemical performances and it can has initial charge capacity of 208mAhg-1.Besides,Li₄Ti_4.95Ni_0.05O₁₂ can deliver the initial charge capacity of 206.3 mAhg-1.After 50 cycle,the capacity can retain 203.2 mAh g-1,which keeps the capacityretention of 96.7 %.The improved electrochemical performances are attributed to the stable the crystal structure due to partly substitution doping Ti – O by Ni – O.The sol-gel method is used to prepare i2Na2Ti6O14 material.The performance and improvement means are also investigated.The optimal calcination temperature and time are 800 oC and 8 h.The initial charge capacity is 120.1 mAh·g-1,and 109.3mAh·g-1 are kept after 50 cycles.The effects of content between Li+ and Na+ on the the structure,morphology,particle size,distribution and electrochemical properties of Li₂Na₂Ti₆O₁₄ were investigated.The Li_2.15Na_1.85Ti₆O₁ deliver the best electrochemical performances and it can has initial charge capacity of 122.6 mAhg-1.After 50 cycle,the capacity can retain 124.7 mAh g-1.