CRYSTAL CHEMISTRY OF LAYERED VANADIUM OXIDE CATHODE MATERIALS. Peter Y. Zavalij, M. Stanley Whittingham. State University of New York at Binghamton, Binghamton, NY 13902-6016, USA

Structural analysis of V₂O₅ layers as well as VO₃ and V₃O₈ polyanions has been done based on known structures with square pyramidal coordination of vanadium and stoichiometry V₂O₅, M_xV₂O₅, M_XVO₃, M_XV₃O₈, M_XV₆O₁₅, etc. including our new compounds (LiV₂O₄.H₂O, TMAV₄O₁₀, TMAV₂O₅ and DTAV₃O₈, where TMA = tetramethyl ammonium, DTA = dodecyl trimethyl ammonium) with novel topography of layers.

The unique layered structures of vanadium oxides and their derivatives are of particular interest because of their capacity to intercalate lithium and other cations between their layers that makes them promising candidates for cathode materials in secondary lithium batteries.

The most common V-polyhedron is a square pyramid VO₅ with double bonded oxygen in its vertex. Those polyhedra when sharing edges form double chain with stoichiometry VO₃ which exist by itself

in KVO₃.H₂O and Co(VO₃)₂.4H₂O. The topography of the double chains can be simply presented by symbolic formula using two symbols (U - up and D - down) which show the orientation of the square pyramid. The symmetry of the formula by using simple rules leads to 10 possible symmetry groups of the double chains. In most cases those double chains form layers by sharing single bonded oxygen atoms of basis. Using different ways of joining chains to the layers the possible symmetry, topography, and dimensions of V₂O₅ layers has been developed. Those conclusions are used to predict the structure of the layers in the novel compounds. The structure of V₂O₅ layers is also discussed from the point of view of their capacity to easily accept additional charges that yields rich intercalation opportunities in contrary to frameworks constructed with VO₄ tetrahedra.