The Study On Synthesis Of Li₄Ti₅O₁₂ As Anode Electrode For Lithium Ion Battery

Lithium ion battery is a new generation green non-pollution battery when itwas used in the 1990s. It is widely used in portable electron apparatus and cars dueto its highlights, such as high voltage, low discharge rate by itself, little volume,light weight and nonmemeory effect, but the anode materials for lithium ionbatteries are the key to constrain its whole performance. The lithium ion batterieswhich used early almost select carbon/graphite as the anode material. But whendischarge for the first time, there are passivation membrane on the surface ofcarbon, which will cause capacity lose. Moreover, the potential of carbon is veryclose to that of lithium, when overcharge, the metal lithium will separate out on thesurface of carbon, which is the intrinsic safety we must concern. While, forLi₄Ti₅O₁2, when used as negative material for Li-ion battery, there is no suchconcerns, and there are almost no structure change during discharge, that is whythere are so small irreversible capacity lose. The potential of Li₄Ti₅O₁2 is 1.55V(vs.Li/Li+), when combined with 4-V positive electrode materials such as LiCoO2,LiNiO2, or LiMn2O4, a 2.5-V cell can be constructed. So it attracts manyresearchers' interests. The condition of synthesis of Li₄Ti₅O₁2, which is spinel with theoreticalcapacity of 175 mAh g-1, is rigor. At present, the main reported methods are asfollow: calcinated the admixture of solid TiO₂ and Li2CO3 at 1000 for 24h in air, 3or calcinated at 800 for 20h under O2/N2 stream. Contrapose such highcondition and TiO₂ raw material, firstly, we synthesized the anatase TiO₂, whichhas high activity, and then infused with acetate lithium for a period of time, afterdrying the admixture, Li₄Ti₅O₁2 is synthesized by calcalcinated the precursor. Theprecursor was analysed by TG-DTA and measured by IR, at the same time, wediscussed the synthesis condition by XRD et al. The result manifest that withhalf-solid method, the single-phase Li₄Ti₅O₁2 can be synthesized by calcinating theprecusor at 850 for 12+12h, and the first discharge capacity is 165mAh g-1,which is 94% of theoretical capacity. The sol-gel method is a new method of wet moist chemical method toprepare materials. Nowadays, the sol-gel method has widely been used to preparecathode electrode for Li-ion battery, but few reported to prepare anode electrode.So we synthesized Li₄Ti₅O₁2 by sol-gel method, discussed the reaction mechanism,had a study on the condition of the reaction. The result show that the single–phaseLi₄Ti₅O₁2will be synthesized at 800 for 20h with tetrabutyl titanate and lithium acetate asraw materials by sol-gel method. The ethanol solution of tetrabutyl titanate will hydrolyzeslowly with acetic acid as depressor. The ratio of tetrabutyl titanate, ethanol, acetic acid andwater have an effect to the gelation time, through the experiment, we find that the ratio of 110 1.8 5 is the best to the gelation time. The results of SEM showe that the single-phaseproducts were obtained by calcinating the gel precursors at 800 in air for 20h, thesinter-temperature is lower than that of solid-state method, the particle size range from 0.3μmto 0.5μm, narrowly distributed, well crystallized. And the first discharge capacity is166mAh g-1, which is 95% of theoretical capacity. We use chromotropic acid spectrophotometer to determine the content of Ti inthe products. The result manifest that under the wavelength of 475nm, we candetermine the concentration of Ti4+ in the solution, and the result is close to theresult measured by ICP. From the result we can conclude that thecalcine-temperature has an effect to the products, with the raising of temperature,there is an increase of titanium percentage in the products. The reason is that the 4lost of lithium under higher temperature, and the result is w...