| Spinel Li4Ti5O12 as lithium ion batteries anode materials have many advantages such as exeellent cycle performance, high safety and“zero-strain” effect. However, the disadvantages of lithium titanate, such as the low electronic conductivity and low ion conductivity, restrict its wholesale commercial applications. Therefore, modification of lithium titanate to improve its rates performance is very important.In this paper, the meso-macroporous lithium titanate and lithium titanate spheres were respectively synthesized by solid state reaction and hydrothermal method. Then the synthetic conditions were optimized. The samples were investigated by X-ray diffraction(XRD) 、 scanning eleetron microscopy(SEM) and the N2 isorthermal adsorption-desorption analysis(BET). Meanwhile, the samples were analyzed by galvanostatic charge/discharge and the electrochemical impedance tests.The meso-macroporous titanium dioxide was synthesized using sol-gel method. The meso-macroporous lithium titanate with spinel structure was prepared with meso-macroporous Ti O2 and Li2CO3 as raw materials. The effect of Li/Ti ratio and sintering temperature on performance of sample were studied. The effects of binder types and glucose coating on the performance of Li4Ti5O12 sample were also studied. The results show that the specific surface area of Ti O2 was 12.06m2/g, the BJH pore volume and average pore diameter was 0.029cm3/g and 9.85 nm, respectively. The optimum condition for the preparation of meso-macroporous Li4Ti5O12 is that Li/Ti=0.86, the calcination temperature is 600°C for 4h and then 800°C for 6h. The initial discharge capacity of sample is 162 m Ah/g at 0.1C, and the discharge capacity retains 152 m Ah/g after 20 th cycle; the performance of Li4Ti5O12 is better using CMC as binder than that using PVDF as binder; when the glucose loading is 8%, the sample shows excellent performance, the initial discharge capacity of sample is 153 m Ah·g-1, the discharge capacity retains 149 m Ah·g-1 after 20 th cycle. The electrochemical impedance tests indicate that the charge transfer resistance of sample decreases gradually with the increase of glucose, which is because the coating carbon enhances the electronic conductivity of the lithium titanate.The lithium titanate sphere with spinel structure was prepared with tetrabutyl titanate, ethylene glycol, lithium hydroxide and cetyltrimethylammonium bromide(CTAB) as raw materials. The effects of amount of lithium hydroxide, hydrothermal temperature, hydrothermal time and sintering temperature on performance and morphology of sample were investigated. The results indicated that the pure spinel lithium titanate was prepared when 10 mmol tetrabutyl titanate reacted with 9mmol lithium hydroxide; When the hydrothermal temperature was lower than 170℃, the impurity phase of Ti O2 appeared in the sample; when the hydrothermal temperature was 170℃, the pure spinel phase was prepared. The hydrothermal reaction time has a great influence on the morphology of the as-synthesized products. When the hydrothermal temperature was 170℃ and the hydrothermal time was 36 h, the sample was perfectly spherical, whose average diameter was between 1 mm and 2 mm. However, the spherical morphology of sample was destroyed with prolonged hydrothermal time. When the hydrothermal temperature was 170℃ and reaction time was 36 h, the sample prepared had excellent performance, the initial discharge capacity was 187 m Ah·g-1 at 0.1C, and the discharge capacity retained 184 m Ah·g-1 after 20 th cycle. When the sintering temperature was 600℃, the initial discharge capacity of sample was 201 m Ah·g-1, and the discharge capacity retained 198 m Ah·g-1 after 20 th cycle. The spinel lithium titanate sphere showed the excellent rate performance and cycling stability. |
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