HEXAGONAL TUNGSTEN TRIOXIDE OBTAINED FROM PEROXO-POLYTUNGSTATE AND REVERSIBLE LITHIUM ELECTRO-INTERCALATION INTO ITS FRAMEWORK

A hexagonal form of WO3 (a = 7.3244(6), c = 7.6628(5), Å, z = 6) was synthesized by the low temperature sintering of an ammonium peroxo-polytungstate precursor. This compound, the N/W ratio of which is 0.015 at most, is not identical to reported hexagonal WO3 from WO3 ·1/3H2O because its c-axis is significantly shorter than that of the latter (7.798 Å). Powder, XRD profile refinements were performed in the space group P63/mcm. We found two kinds of structural models that showed reasonably good profile agreement (R0.07). Both models are built up of remarkably distorted WO6 octahedra, in which part of the O-O distances are very short (2.32 ≈ 2.42, Å). Electrochemical intercalation of lithium into the present WO3 framework was investigated using a Li|LiPF6|WO3 cell. It was found that Li was intercalated reversibly up to the composition Li1.0WO3. © 1992 Academic Press, Inc.