Structural Characteristics of Lithium Nickel Phosphate Studied Using Analytical Electron Microscopy and Raman Spectroscopy

Abstract

The structural characteristics of lithium nickel phosphate (LiNiPO4) prepared by solid-state chemical reaction have been studied in detail using the analytical electron microscopy and Raman spectroscopy measurements. The high-resolution transmission electron microscopy and selected area electron diffraction measurements indicate that the grown LiNiPO4 is well-crystallized in olivine structure without any indication of crystallographic defects such as dislocations or misfits. The energy-dispersive X-ray spectrometry coupled with the elemental compositional mapping using high-angle angular dark field scanning electron microscopy confirms the chemical quality of the grown LiNiPO4 in terms of homogeneity and uniform elemental distribution characteristics. The local structure and chemical bonding between NiO6 octahedral and (PO4)3- tetrahedral groups probed by Raman spectroscopy also indicate the high-quality of LiNiPO4. Structural analysis of the delithiated Li0.09NiPO4 phase indicates lattice contraction and distortion upon lithium extraction. A detailed analysis and comparison of the pristine and delithiated phases is also reported.