Single crystals of Li4 + xTi5O12 were prepared by means of electrochemical Li-ion intercalation technique using parent Li4Ti5O12 single crystals. The obtained Li4 + xTi5O12 (x = 1.35) crystallizes in the cubic spinel-related type structure, space group Fd3m, and lattice parameters of a = 8.346(2) angstrom and V = 581.3(5) angstrom(3) and Z = 8. The Li-ion intercalated sites were successfully determined to be both the 8a and 16c sites by using the difference Fourier synthesis map. The structure was determined by single-crystal X-ray structure analysis and refined to the conventional Value of R = 3.7% for 132 independent observed reflections. The chemical composition has been determined to be Li5,35Ti5O12 from the result of site-population refinements. In addition. theoretical electron density distributions and total energy were calculated for three postulated compounds of "Li4.5Ti4.5O12" and "Li4.5 + xTi4.5O12" with x = 1.5 and 3.0. (C) 2008 Elsevier B.V. All rights reserved.