Synthesis And Electrochemical Research Of Titanate As Anode Materials For Lithium Ion Batteries

Recently. TiO2 and Li4Ti5O12 have drawn extensive attention because of the large-scale commercial application prospect as alternative anodes to conventional carbon anode. However, both of them show poor rate performance due to lower ionic and electronic conductivity, which hinders their commercial applications. In this thesis, we have synthesized titanate with one dimension morphology by a hydrothermal route. TiO2/CNTs and Li4Ti5O12/CNFs were prepared by in-situ route growing one dimension carbon nanometer material on the surface of titanate using the chemical vapor deposition method The former is beneficial to enhance Li+ions diffusion kinetics by improving specific surface area; while the later leads to improved the rate and cycle performance through enhancing electronic conductivity and maintaining microstructure stability.TiO2 nanotubes were prepared at high temperature and pressure by the hydrothermal method using spherical TiO2 as the precursor. The nanotubes have a homogeneous size distribution and good crystallization with a diameter of 15-20 nm and a length of several microns. Its first discharge capacity is 266.6 mAh/g. markedly higher than that of spherical TiO2(183.1 mAh/g) due to the higher specific surface area that improves the Li+ions acceptor vacancy. TiO2 nanorods were prepared by oil-bath method using tetraalkoxyltitanium as the raw material. The effects of reactant concentration, reaction temperature and time, and the cooling methods on the microstructure of the products were investigated. It was found that the product exhibits a uniform distribution and a clean surface when prepared with a reactant concentration of 0.125 mol/L. a heating temperature of 170℃, a heating time of 2 h and oil cooling methodIn this study, the effects of different catalysts and catalyst dosage on the microstructure TiO2/CNTs were studied. Compared to FeCl3·6H2O, Fe(NO3)3·9H2O has better catalytic effect. An optimal CNTs yield in the composite was obtained when the Ti:Fe molar ratio was 99:1. TiO2/CNTs with a uniform network structure was synthesized using TiO2 nanotube as the precursor. Electrochemical study demonstrates that it has outstanding electrochemical performance. The first discharge and charge capacity are 304 and 280 mAh/g, respectively. The rate performance test shows that at a relatively high current density of 500 mA/g. it still has a capacity of 143 mAh/g. Cyclic voltammogram tests show that, minor changes in the CV plots is observed after 5 and 50 times, revealing this material has fast electrode kinetics.LiTi5O12/CNFs composite was synthesized using the chemical vapor deposition method in N2/C2H2 by in situ growing CNFs on the LiTi2O12 surface. CNFs with a diameter of 15-20 nm and a length of several microns, contact intimately with Li4Ti5O12 to form good conductive network for Li4Ti5O12. The in situ grown CNFs can inhibit the growth of Li4Ti5O12 particles. Electrochemical test shows that it has good rate and cycle performance with a first discharge capacity of 140 mAh/g at 10C. Even after 500 cycles, a capacity of 131 mAh/g is still maintained with a capacity retention rate of 90%.