Five vanadium phosphate (V2O5–P2O5) glasses, containing between 58 and 88 mol% V2O5, have been prepared using the melt-quenching technique. IR spectroscopy, in conjunction with powder X-ray diffraction (XRD) of the devitrified materials, has been used to show that the glasses containing 70 mol% V2O5 have a microstructure which is similar to that of β-VPO5 whereas the remainder show both orthorhombic-V2O5 and β-VPO5 structural features. Molar-volume data suggest that there is a fairly abrupt change in microstructure atca. 75 mol% V2O5. The glasses have been employed as the active component of the cathode in lithium polymer-electrolyte cells operating at 120 °C and the cycling performance has been investigated as a function of glass composition. After an initial capacity decline the cells showed good reversibility, although this was not achieved at capacities as high as that of V6O13 in a similar cell. Glasses containing less than 78 mol% V2O5 cycled at considerably lower capacities than those with higher vanadium content and this has been related to the above change in microstructure from a layered V2O5-type to a network β-VPO5 type.