Zero-strain insertion mechanism of Li[Li1/3Ti5/3]O4 ( F d 3 ¯ m , a = 8.35 7 _ Å) 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]O4 to 0.257 for Li2[Li1/3Ti5/3]O4 while the cubic lattice dimension remains virtually constant. This indicates that bond length of TiO elongates from 1.96 to 2.03Å due to the change in oxygen parameter, when Li[Li1/3Ti5/3]O4 is reduced to Li2[Li1/3Ti5/3]O4. Relationship among the cubic crystallographic unit cell dimension, mean bond length of TiO, and oxygen parameter is given for space group symmetry of F d 3 ¯ m in order to understand the zero-strain insertion scheme, and an origin of the zero-strain insertion scheme is discussed from the analytical results.