Study Of Preparation And Electrochemical Performance Of Spherical Lithium Titanate As Anode Materials For Li-ion Batteries

Spinel Li₄Ti₅O₁₂?LTO?has been proved to be one of the most promising alternative anode materials for high-rate lithium-ion batteries,because of its zero-strain characteristic allowing excellent structure stability and long cyclic life during charge-discharge process.Moreover,LTO shows a very flat charge-discharge plateau around 1.55 V?vs.Li/Li+?,which avoids the security problems caused by the formation of dendritic lithium.However,poor electronic and ionic conductivity of LTO seriously limit its high-rate performance.Therefore,the study of lithium titanate to improve its rates performance is very necessary.In this paper,monodisperse LTO microspheres were synthesized by cetyltrimethylammonium bromide?CTAB?-assisted hydrothermal method with butyl titanate and lithium hydroxide as raw materials and following calcination.Thus,the effect of the preparation conditions on the microstructure of LTO microspheres was investigated,and also the further study about the relationship of LTO microspheres structure and electrochemical performance.First,the LTO microspheres with different structure was prepared under the calcination temperature of 500,600 and 700 °C respectively,and the electrochemical properties of the samples were studied.It was shown that the three samples were all LTO microspheres about 4 ?m,the primary crystallite sizes were 50,50,and 200 nm respectively.XRD refinement result shows that LTO500 and LTO600 contains trace amounts of TiO2 were almost pure LTO,but LTO700 containing 12.5% of Li2TiO3.specific surface area were 71.8,38.6,and 10.3 m2·g-1.XPS analysis shows that LTO600 has the minimum relative content of Ti3+.The specific capacities at 0.1C are all close to the theoretical capacity of LTO for the three samples.Higher specific capacity is obtained with LTO600 at high C-rate,indicating beneficial effect of smaller primary crystallite size and larger surface area.Notably,LTO600 exhibits superior rate performance and excellent cyclic stability.The charge specific capacities at 5C,10 C,20C and 50 C are up to 158,154,153 and 148 mAh·g-1,respectively.More importantly,the capacity retention after 380 cycles at 5C is as high as 150 mAh·g-1.So the key factors of the electrochemical performance of LTO microspheres were the primary crystallite sizes and the specific surface areas.Second,LTO microspheres with different pore structure was prepared by calcination under 500 °C for 5,8 and 10 h,and electrochemical properties were studied.It was shown that as the calcining time prolonged,the specific surface area and specific capacity of LTO were gradually increased as CTAB gradually resolved.When the calcining time was 8 h,LTO shows a primary crystallite size about 50 nm,surface area of 82 m2·g-1 and total pore volume of 0.598 cm3·g-1.Its reversible capacity remains 169 mAh·g-1 after 500 cycles at 5C.More importantly,its reversible capacity is up to 158 mAh·g-1 at 50 C,exhibits superior rate performance and excellent cyclic stability.Finally,the influence of CTAB on LTO morphology was studied by changing the amount of CTAB,and the results show that when the addition of CTAB quantity increased from 0.5 g to 2.5 g,the particle size of LTO microspheres decreases.When the addition of CTAB quantity increased to 3.0 g,the LTO was amorphous,suggesting that the amount of CTAB played a key role in LTO microsphere preparation.