Solid‐State Synthesis of 70 nm Li ₄ Ti ₅ O ₁₂ Particles by Mechanically Activating Intermediates with Amino Acids

Abstract

A novel synthetic method of fine particles of highly pure Li 4 Ti 5 O 12 with the smallest possible particle size was proposed. A stoichiometric mixture of CH 3 COOLi·2H 2 O and anatase fine particles of ca. 50 nm was calcined at 773 K to obtain an intermediate, comprising Li 2 TiO 3 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 Li 4 Ti 5 O 12 with a phase purity above 97%. When we used ALA or PHE as an additive, the microscopically determined average particle size of Li 4 Ti 5 O 12 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: Li 2 TiO 3 and Li 4 Ti 5 O 12 .