High Capacity Microporous Molybdenum-Vanadium Oxide Electrodes for Rechargeable Lithium Batteries

Microporous Mo2.5+yVO9+delta with channels defined by seven-membered rings of corner-sharing MO6 (M = Mo5+/6+ or V4+/5+) octahedra belongs to the family of isostructural MoVNbTeO compounds, which are very active and selective oxidation catalysts for light alkanes. The large open channels which can accommodate small ions, together with the redox properties of Mo2.5+yVO9+delta, make this material of potential interest as a rechargeable intercalation electrode. Microcrystalline Mo2.5+yVO9+delta was synthesized by hydrothermal reaction of (NH4)(6)Mo7O24 center dot 4H(2)O and VOSO4 center dot nH(2)O and exists in the composition range -0.13 <= y <= 0.05. The electrochemical properties of Mo2.5+yVO9+delta were investigated in Li/1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC)/Mo2.5+yVO9+delta cells. When the cells are discharged between 3.9 and 1.5 V vs Li/Li+, up to 6 Li+ ions per formula unit are electrochemically inserted into the framework. Upon recharge, all of the Li+ ions can be extracted with minimal structural rearrangement Unit cell dimensions for LixMo2.5+yVO9+delta (0 < x <= 6) phases prepared by chemical lithiation with n-BuLi have been determined by powder X-ray analysis and are closely related to those of the parent Mo2.5+yVO9+delta phase with orthorhombic Pba2 symmetry. Lithium cells of Mo2.5+yVO9+delta are rechargeable and exhibit a reversible capacity exceeding 300 mAh/g making Mo2.5+yVO9+delta a potential electrode material for secondary lithium batteries.