STRUCTURAL ASPECTS OF TRANSITION METAL OXIDE CATHODE MATERIALS FOR LITHIUM BATTERIES. Christina Lampe-Onnerud, Massachusetts Institute of Technology, Cambridge MA 02139, S. Greenbaum, P.E. Stallworth, S. Kostov, and M. DenBoer, The City University of New York, Hunter College, New York NY 10021, Denis Fauteux and Arthur Massucco, Arthur D. Little Inc., Battery Technology Center, Cambridge MA 02140

First-row transition metal oxides have over the years received much interest as cathode materials for lithium intercalation in rechargeable cells. Strong candidates for a future thin-film battery include Li_xV₆O₁₃, LiCoO₂, and spinel Li_xMn₂O₄ systems, exhibiting high capacity in an attractive voltage range for application devices. The crystallinity and atomic arrangement will be addressed in the light of X-ray and neutron diffraction in combination with spectroscopic evaluation by NEXAFS, EPR and NMR.

Neutron diffraction shows that as lithium is intercalated into V₆0₁₃, the (O,O,O)-position starts to fill. However, upon further intercalation, powder diffraction identifies an increasing amorphous component. ⁵¹V and ⁷Li NMR line shape and spin-lattice relaxation time measurements for Li_XV₆0₁₃ (O<x<6) shows some changes in conduction pathways or mechanisms as a function of x, although the NMR results are dominated by the presence of paramagnetic V⁴⁺. Our previous findings identifying four phases (Li_xV₆O₁₃; x=0.5, 1.5, 3, and 6) were confirmed by the spectroscopic measurements.

X-ray Rietveld refinements on LiCoO₂ and spinel Li_xMn₂O₄ show that a dynamic and flexible synthesis process leads to well-defined phase-pure and highly crystalline materials. Results from cathode materials containing chromium and iron substitution for manganese using diffraction and EXAFS are also reported. Questions regarding the possible clustering of Mn- or Cr-rich domains will be addressed.