Superlattice formation in the lithiated vanadium oxide phases Li0.67V6O13 and LiV6O13

Two new lithiated phases of V6O13 were formed by carefully tuning the tempe rature of electrochemical lithiation in a 'coffee-bag' type Li-ion battery at 2.78 V versus Li/Li+. These were studied by single-crystal X-ray diffrac tion. A phase with the composition Li-2/3 V6O13 was obtained at 308 K with a unit cell three times the volume of the original V6O13 cell. A single cry stal discharged at ambient temperature was shown to be LiV6O13 and twice th e unit-cell volume of the original V6O13 cell. On lithiation, the structure s retain their basic V6O13 structure of alternating single and double layer s of VO6 octahedra. The lithium ions occupy chemically equivalent sites, wh ere they coordinate fivefold to O atoms, and associate with the single laye rs of VO6 octahedra. The insertion of lithium causes a significant elongati on of one of the V-O bonds in each structure, which expands from 1.65 to 1. 89 Angstrom; this is due to the charge reduction of a specific V atom.