Structural, dielectric, and conductivity studies of yttrium-doped LiNiPO4 cathode materials

Olivine-structured pure LiNiPO4 and yttrium-doped LiNiPO4 have been synthesized by a Pechini-type polymerizable precursor method. Compound formation temperature is confirmed from thermogravimetry to differential thermal analysis. Powder X-ray diffraction pattern confirmed the formation of phase pure LiNiPO4 compound with an orthorhombic structure with fine crystallite size. Presence of preferred local cation environment is understood from Fourier transform infrared spectroscopy (FTIR) studies. XRD and FTIR studies show that doped yttrium ion entered in the lattice of LiNiPO4. It has been found that the ionic conductivity of LiNiPO4 is enhanced by around two orders of magnitude by doping yttrium. Dielectric spectra show the decrease in dielectric constant with increase in frequency. Dielectric loss spectra reveal that dc conduction contribution predominates in the sample.