Preparation And Electrochemical Characterization Of Ions Doped Li₄Ti₅O₁₂ Anode Material

Li₄Ti₅O₁₂2 has become a research hotspot for the following reasons:the structure is no change during the process of charging and discharging,it is called“zero strain”materials,so it has super long life;what's more,the voltage of Li₄Ti₅O₁₂2 is 1.55 V,no lithium dendrite,so it has high safety.However,Li₄Ti₅O₁₂2 has low specific capacity,theoretical specific capacity is only 175 mAh/g and poor conductivity(10^-99 S cm^-1),which seriously limits the commercial use of Li₄Ti₅O_12.Solid state method is used to product Li₄Ti₅O₁₂2 in industry for its simple operation.However,Li₄Ti₅O₁₂2 particles produced by this method are coarse and uneven.The preparation of nanoparticles by liquid phase method is complicated and contaminated.Therefore,this paper is devoted to two aspects:on the one hand,it is devoted to the study of a suitable method—solid state method with ions doped to prepare nano-Li₄Ti₅O₁₂particles;on the other hand,it is devoted to improve the specific capacity of Li₄Ti₅O₁₂anode materials and the poor conductivity.The following are the main contents of this paper:1.Li₄Ti₅O₁₂2 nanoparticles were prepared by solid state method with ions doped technique.The dosage of Mg and Zr,calcination temperature and holding time as four factors were selected and three levels were set respectively.A L₉?3⁴?orthogonal experimental was designed.Li₄Ti₅O₁₂2 with particle size about 100 nm was prepared by orthogonal experiment and the optimum preparation process was determined as follows:Mg content was 0.1 mol,Zr content was 0.05 mol,calcination temperature was 750?and holding time was 10 h.In addition,the order of factors affecting the evaluation index was determined by orthogonal experiment:calcination temperature>Mg content>holding time>Zr content.2.The co-doped Li₄Ti₅O₁₂2 prepared under the optimum conditions was compared with pure Li₄Ti₅O₁₂.It was found that co-doped ions had an important influence on the performance of Li₄Ti₅O₁₂.After 100 cycles,the specific capacity of co-doped Li₄Ti₅O₁₂2 at10 C was still 90.8 mAh/g compared to the pure Li₄Ti₅O₁₂2 with specific capacity of 39.3mAh/g,which improved 1.3 times.3.Next the influence of different ion doping ratio on the properties of Li₄Ti₅O₁₂2 was explored.It was found that different R?Mg/Zr?have obvious effects on Li₄Ti₅O₁₂.When R=2,LTO-R2 exhibits the best electrochemical performance.At 0.57 C,the initial discharge capacity was 186.6 mAh/g.In addition,Mg and Zr ions have a symmetrical and complementary influence in morphology and have a co-operate effect on electrochemical performance.4.Finally,acetylene black and LTO-R2 were physically combined by mechanical grinding.It was found that the charging capacity of C-15%was 106.2 mAh/g,which was lower than 155.5 mAh/g of LTO-R2.The addition of acetylene black will reduce the specific capacity as its intensified the gather of particles.