Single-crystal studies of electrochemically delithiated LiMn2O4

Single-crystals of LiMn2O4 spinel have been synthesized and investigated by X-ray diffraction (XRD). On the basis of the systematic absences, the cubi c space-group Fd (3) over barm was chosen with a = 8.245(4) Angstrom. The c rystals were then delithiated electrochemically to three different voltages : 4.25, 4.11 and 4.10 V vs Li/Li+. The lithium-depleted single-crystals obt ained at 4.25 and 4.11 V exhibited a 7 x 7 x 7 superlattice cell with a ' = 56.49(2) and 57.13(3) Angstrom, respectively. At 4.10 V, the crystals show a 3 x 3 x 3 superlattice with a " = 24.41(1) Angstrom. These superlattices can be ascribed to ordering of manganese ions with different oxidation-sta tes. (C) 2001 Published by Elsevier Science B.V.