Correlation between structural and electrochemical properties of Li metal vanadates

LiCoyNi1−yVO4 compounds (y=0, 0.2, 0.5, 0.8, 1) have been prepared for lithium-ion cell cathode applications by different chemical routes. The polycrystalline materials were characterized by X-ray powder diffraction (XRPD) and by solid state 7Li and 51V nuclear magnetic resonance (NMR) analysis. The results show an increase of the lattice parameter with increasing Co content and a varying distribution of Co, Ni, and V in the crystallographic sites. Moreover, both XRPD and NMR data reveal different degrees of crystallinity depending on the preparation method. The first electrochemical tests show that the distribution of ions in the various crystallographic sites and the crystallinity degree are correlated to the electrochemical performances.