Structural characteristics of lithium nickel phosphate studied using analytical electron microscopy and raman spectroscopy

The structural characteristics of lithium nickel phosphate (LiNiPO ₄) 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 LiNiPO ₄ 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 LiNiPO ₄ in terms of homogeneity and uniform elemental distribution characteristics. The local structure and chemical bonding between NiO ₆ octahedral and (PO ₄) ^3- tetrahedral groups probed by Raman spectroscopy also indicate the high-quality of LiNiPO ₄. Structural analysis of the delithiated Li _0.09NiPO ₄ phase indicates lattice contraction and distortion upon lithium extraction. A detailed analysis and comparison of the pristine and delithiated phases is also reported.