Optimization of the Synthesis Conditions of Nanostructure 3DOM Li4Ti5O12 spinel with High Rate Capability
A variety of preparation methods, including sol-gel, hydrothermal and template synthesis, have been developed in order to obtain structures with large surface area and open pores as the three dimensionally ordered macroporous (3DOM) spinels. The synthesis of pure phases of 3DOM-LTO structures presents difficulties; some samples results in different amounts of Li2TiO3, rutile, and anatase as side products and the high temperatures destruct the porous structure. As calcination time increases, grains of lithium titanate grow larger and, consequently, the 3DOM structure breaks down. 3DOM architecture, however, comes at the expense of phase purity. In spite of the interest for this material, to the best of our knowledge reports on its preparation as 3DOM material are scarce. Since we found the result critically depended on the salt used and the thermal treatment, particular emphasis was given to the understanding of the formation process.
This study aims to achieve the best synthesis conditions to prepare nanostructured 3DOM-LTO. Samples have been synthesized by a colloidal templating process with and without hydrothermal conditions. It is also studied the effect of a pre-forming step and subsequent incorporation of lithium or directly addressing the chemical processes in one step. We have found that a well-defined sequence of steps during synthesis is necessary for the successful formation of the inverse opal. 3DOM-LTO synthetize samples have been studied by means of thermal analysis, x-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR). Morphological and microstructural characterizations are carried out by scanning and transmission electron microscopy (FE-SEM, TEM) and by gas adsorption. The remarkable improvement of the electrochemical performances, specially a high current, is shown by comparing with LTO-commercial samples.
E.M. Sorensen, S.J. Barry, H-K. Jung, J.R. Rondinelli, J.T. Vaughey, K.R. Poeppelmeier. Chem. Mater. 18 (2006) 482
J. Lu, C. Nan, Q. Peng, Y. Li. Journal of Power Sources 202(2012) 246
G-N. Zhu, Y-G. Wang, Y-Y. Xia, Energy Environ. Sci. 5 (2012) 6652
This research has been supported by the projects MAT2011-22969, MAT2013-46452-C4-2-R and MATERYENER3CM S2013/MIT-2753.