Synthesis And Modification Of Li₄Ti₅O₁₂ Anode Powder And Film For Lithium Ion Batteries

In recent years,with rapid growth of portable electronic products and electric vehicle industry,the energy storage has received more attention,thus lithium ion batteries play an increasingly important role in daily life and manufacture,and the people demand more requirements for the performance of lithium ion batteries.Spinel lithium titanate(Li₄Ti₅O₁₂)material shows the advantages of safety,cycle stability and long life.As the anode material of lithium ion battery,it can greatly improve the safety,charge and discharge efficiency,life-time,and alleviate the problem of volume expansion,hence it exhibits great potential.In this study,Li₄Ti₅O₁₂powders were prepared by high-temperature solid-state method（two-step calcination）using lithium carbonate and titanium dioxide as raw materials.The results show that pure spinel Li₄Ti₅O₁₂powder with uniform particle size of 200～400 nm can be obtained by calcining at 800℃for 6 h under the condition of excess amount（10%）of lithium source.The sample exhibit an initial specific capacity of 157.7 m A·h/g at 0.5 C charge and discharge,the coulombic efficiency reaches96.1%,and the capacity retention rate is 98.6%after 100 cycles.Compared with samples derived at other temperatures,the samples prepared demonstrate lower charge transfer impedance and higher and sharper redox peaks.Alternatively,Li₄Ti₅O₁₂powders were also prepared by sol-gel method using lithium acetate and tetrabutyl titanate as raw materials and citric acid as complexing agent.these resulting powders show diameters ranging from 100nm to 200nm,and the resulting samples calcinated at 750℃show the initial discharge capacity of 167.6m A·h/g at 0.5 C,,its capacity retention rate was 98.1%after 100 cycles,and its specific capacity retained 67.1m A·h/g at the current density of 20 C.It exhibits better electrochemical performance than other samples derived at different temperatures.Based on the above synthetic procedure,Li₄Ti₅O₁₂was doped with Cr element.The results show that Cr element replaces the position of Ti and is uniformly incorporated into Li₄Ti₅O₁₂;the doped Li₄Ti_4.9Cr_0.1O₁₂samples still persist the cubic spinel structure,but show smaller and more uniform particles;the 0.5C discharge specific capacity of the sample can reach 170.4m A·h/g,and the reversible specific capacity of 169.7m A·h/g can be maintained after 100 cycles,the capacity retention rate was 99.4%.Compared with pure Li₄Ti₅O₁₂,it shows higher electrochemical performance.Li₄Ti₅O₁₂thin film material was prepared on Si substrate by solution deposition and amorphous multilayer coating.The appropriate conditions for the preparation of thin films were investigated.The Li₄Ti₅O₁₂thin films were prepared by annealing at700℃for 30 min in the precursor solution with lithium-titanium ratio of 5.5:5.Under this condition,Li₄Ti₅O₁₂thin films doped with different amount of silver were prepared by adding silver nitrate into the precursor.The results show that the added silver is dispersed evenly in the thin film,and the original structure is not changed.The introduction of dispersed silver particles apparently increases electronic conductivity of thin film,which alleviates the shortcomings of Li₄Ti₅O₁₂.