The Study On Process And Performance Of Porous Li₄Ti₅O₁₂ Mirospheres With High Tap Density

Li4Ti5O12, as anode materials for lithium ion batteries, exhibiting “zero strain”, high safety performance, has received more and more attention. However, electronic conductivity and tap density of Li4Ti5O12 are very low. The aspect of improving the conductivity of Li4Ti5O12 has been a lot of researches, mainly using nanotechnology, surface coating and doping metal elements. However, researches are less in improving tap density of Li4Ti5O12.This thesis adopted the spray drying technique with a twice sintering process to prepare porous Li4Ti5O12 anode material with high tap density and good cycle performance for lithium ion batteries, raw materials are lithium carbonate and anatase titanium dioxide. Purpose of the twice sintering process is to remove gas generated in the reaction to form a precursor product by calcining raw mixtures before spray drying, and to form a loose spherical precursor composed of primary particles after spray drying, spherical precursors contract and melt crystal growth at high temperature, forming Li4Ti5O12 with integral connection between the primary particles and mesoporous barrier after a second calcination.Tap density of lithium titanate is up to 1.20 g cm-1 using this synthetic method and is 1.4 times as high as the prepared sample through once sintering process. Moreover, Li4Ti5O12 prepared by the method has excellent cycle performance, owing to existence of many pores within interior of spheres to promote the permeability of electrolyte, and because primary particles are connected to each other to reduce contact resistance. The Li4Ti5O12 sample has 98.35 % retention rate of capacity after 400 cycles at 1 C.We also study on the parameters of the spray drying, sintering temperature and time. We found porous Li4Ti5O12 microsphere(LTO-850) with high tap density that has optimal comprehensive performance was obtained in the feed concentration of 0.28 g m L-1 by calcining 8 h at 850 ℃ after spray drying.Finally, we did some modifications on the basis of LTO-850 microsphere. Include the following aspects: the TiO2-Li4Ti5O12 composites were prepared by adjusting mole ratio of Li and Ti; LTO-850 microsphere did not add conductive agent in the process of assembling battery; spherical precursor was calcined in different atmospheres(air, H2-Ar mixed gas) to get samples. We also tested performance of Li4Ti5O12 microsphere in high and low temperature.