Synthesis mechanism of LiNiVO4 by wet chemical method and mixed valence of nickel and vanadium

The single phase LiNiVO4 has been successfully synthesized by adopting a new mild liquid route with oxalic acid as both complexant and precipitant, and this method is named the CPG method. The products were obtained by sintering the dry gel precursor which was prepared by the CPG method at 200-850℃ for 2-10 h in air. The products were tested by XRD, XPS, ESR and TGA-DTA, and the resuits indicate that the single phase LiNiVO4 could be obtained at 450℃ for 2-3 h in air and LiNiVO4 was still steady at 850℃ for 10 h. The valence analyses show that in LiNiVO4 the valence of lithium is +1, both nickel and vanadium have the mixed valence, namely +2, +3 for nickel and +4, +5 for vanadium respectively. The LiNiVO4 can be expressed as LiNi3+xNi2+ 1-x V4+ x V5+ 1-x O4 (0≤x＜1). The pyrolysis mechanism of the dry gel is also discussed.