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

Microporous Mo 2.5+ y VO 9 +δ with channels defined by seven-membered rings of corner-sharing MO 6 (M = Mo 5+/6+ or V 4+/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 Mo 2.5+ y VO 9 +δ, make this material of potential interest as a rechargeable intercalation electrode. Microcrystalline Mo 2.5+ y VO 9 +δ was synthesized by hydrothermal reaction of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and VOSO 4 · n H 2 O and exists in the composition range −0.13 ≤ y ≤ 0.05. The electrochemical properties of Mo 2.5+ y VO 9 +δ were investigated in Li/1 M LiPF 6 in ethylene carbonate (EC) and dimethyl carbonate (DMC)/Mo 2.5+ y VO 9 +δ 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 Li x Mo 2.5+ y VO 9 +δ (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 Mo 2.5+ y VO 9 +δ phase with orthorhombic Pba 2 symmetry. Lithium cells of Mo 2.5+ y VO 9 +δ are rechargeable and exhibit a reversible capacity exceeding 300 mAh/g making Mo 2.5+ y VO 9 +δ a potential electrode material for secondary lithium batteries.