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

Abstract

Olivine-structured pure LiNiPO 4 and yttriumdoped LiNiPO 4 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 LiNiPO 4 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 LiNiPO 4. It has been found that the ionic conductivity of LiNiPO 4 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.

Structural and Optical Properties of Li<sup>+</sup>: PVP & Ag<sup>+</sup>: PVP Polymer Films

“…Figures 7(a), (b) and (c) show the dielectric constant of the host PVP, Li increase in frequency. This can be understood on the basis that the mechanism of polarization [26]. Figures 8(a), (b) & (c) show the dielectric loss tangent PVP polymer films at different temperatures as a function of frequencies by an Impedance Analyzer.…”

Role of structural defects in olivine cathodes

“…Sung-yoon chung, et al [38] doped series of metal cations ranging from valence 1+ to 5+ in low concentration (~ 1%) and showed the stability in olivine structure while achieving an improvement in capacity. The supervalent (3 + to 5 + ) dopants like Cr, Y, Ti, Zr M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 9 and Nb have been successfully doped in the olivine structure in low concentration without affecting the structural stability [38][39][40][41][42][43]. These dopant decreases the grain size due to cation vacancies created during charge compensation and also the presence of the dopant increases the size of channel for Li + diffusion.…”

“…These dopant decreases the grain size due to cation vacancies created during charge compensation and also the presence of the dopant increases the size of channel for Li + diffusion. This feature has resulted in improving the electrical and ionic conductivity of the olivine cathode [38][39][40][41][42][43].…”

Effect of magnesium substitution on structural and dielectric properties of LiNiPO4

“…So, the conduction in cathode materials takes place through charge migration of ions between coordinated sites of the polymer along with the segmental relaxation of polymer. An enhanced ionic conduction is a natural consequence of a type of cathode material [41,42].…”