Zero-strain insertion mechanism of Li[Li1/3Ti5/3]O-4 (Fd(3) over barm, a = 8.357 angstrom) was examined by ex situ XRD. Change in oxygen positional parameter at 32(e) sites was observed to be from 0.266 for Li[Li1/3Ti5/3]O-4 to 0.257 for Li-2[Li1/3Ti5/3]O-4 while the cubic lattice dimension remains virtually constant. This indicates that bond length of Ti-O elongates from 1.96 to 2.03 angstrom due to the change in oxygen parameter, when Li[Li1/3Ti5/3]O-4 is reduced to Li-2[Li1/3Ti5/3]O-4. Relationship among the cubic crystallographic unit cell dimension, mean bond length of Ti-O, and oxygen parameter is given for space group symmetry of Fd(3) over barm in order to understand the zero-strain insertion scheme, and an origin of the zero-strain insertion scheme is discussed from the analytical results. (C) 2005 Elsevier Ltd. All rights reserved.