Solid-state synthesis of 70 nm Li4Ti5O12 particles by mechanically activating intermediates with amino acids

A novel synthetic method of fine particles of highly pure Li4Ti5O12 with the smallest possible particle size was proposed. A stoichiometric mixture of CH3COOLi.2H(2)O and anatase fine particles of ca. 50 nm was calcined at 773 K to obtain an intermediate, comprising Li2TiO3 and unreacted titania. The intermediate was then intensively milled by a planetary ball mill for 1 h. After adding an amino acid, glycine, alanine (ALA), or L-phenylalanine (PHE), the mixture was further milled under a milder condition for another 3 h and subjected to a second calcination at 973 K for 1 h to obtain Li4Ti5O12 with a phase purity above 97%. When we used ALA or PHE as an additive, the microscopically determined average particle size of Li4Ti5O12 was 70 +/- 10 nm. The mechanisms and significance of the present two-step calcination with mechanical activation and addition of an amino acid to the intermediate were discussed in terms of the topotactic nature of transformation between the two layer-structured species: Li2TiO3 and Li4Ti5O12.