The Preparation And Electrochemical Performance Of Lithium Titanate/CNTs Anode Materials

As a commercial anode material,lithium titanate has both advantages and drawbacks.It’s advantages are its extraordinary stable structure and excellent cycle performance due to its insignificant volume change during charge and discharge processes.However,when used as an anode material,its low electrical conductivity limits its applications in high-power density requiring areas.In the present investigation,Ti-ethylene glycol polymer is synthesized aroun d the carbon nanotubes（CNTs）and the Ti-ethylene glycol is then decomposed in LiOH/H₂O to yield the Li₄Ti₅O₁₂（LTO）encapsulated CNTs anode material（LTO-CNTs）.The resulted LTO-CNTs not only retains the original excellent performance of lithium titanate materials,but also has high electric conductivity and high lithium ion diffusion rate.The LTO-CNTs has enven better rate performance as well as higher specific capacity.In this investigation,a new m ethod was designed for the synthesis of LTO-CNTs.Isopropyl titanate and glycol are polymerized in the presence of CNTs.The resulting polymer was hydrolyzed in Li OH/H ₂O solution and then thermally decomposed to obtain the anode materials.（1）The material is calcined at different temperature.It is found that when the material is calcined at 700℃,the resulted LTO-CNTs has both high electric conductivity and high lithium ion diffusion rate.This material has a stable deep discharge capacity（as low as 0.01 V）,high specific capacity（237 m Ah/g at 0.3 A/g）and long cycle life-time（254 m Ah/g at 0.1 A/g,discharge more than 500 Sub-cycles）.High specific capacities of 258,224,211,200,193,163 and 158 m Ah/g were obtained at current densities of 0.1,0.3,0.5,0.7,1.0,2.0,and 3.0 A/g,respectively.The deep discharge capability of the material can provide an average volta ge less than 1.0 V,which is lower than the average voltage of Li ₄Ti₅O₁₂（1.55 V）.（2）When different glycols are used as reactants,spinel-type Li₄Ti₅O₁₂ can be obtained.When ethylene glycol is used as the reactant,the optimal LTO-CNTs is obtained,which shows the best electrochemistry performance.（3）When dispersing CNTs in different dispersants,it is found that the dispersants not only affect the dispersion effect,but also affect the properties of LTO/CNTs.When ethanol is used as the dispersant,no t only an ideal spinel-type lithium titanate is produced,but also it’s electrochemical performance is better than using other dispersant.