Crystal and electronic structures of inverse spinel-type LiNiVO4

Nearly monophasic LiNiVO4 has been successfully prepared by the sol-gel method. The crystal structure has been determined by powder X-ray diffraction with Rietveld refinement. The material is found to be of the inverse spinel-type structure (ie. V in tetrahedral site and (Ni,Li) in octahedral site) with lattice parameter a of 8.2233(1) Å. Moreover, mutual chemical substitution between V and Ni has been found. X-ray absorption near edge structure (XANES) of the LiNiVO4 has been examined. Vanadium has a tetrahedral symmetry as found by XANES of V K-edge absorption. Based on the energy shifts of the absorption peaks in the XANES spectra correlated with the effective charge, the valences of V and Ni in LiMn2O4 are determined to be ∼ 5+ and 2+ respectively.