oa South African Journal of Chemical Engineering - Structural and electrochemical characterizations of nanostructured olivine LiNi1-xCoxPO4 (x¼0 and 0.5) cathode materials for lithium-ion batteries - research
Abstract
Olivine structured lithium transition metal phosphates are interesting cathode materials for lithium-ion
batteries due to their excellent thermal and structural stability. This paper describes the synthesis of
nanostructured olivine LiNi
1-x CoxPO4 (x ¼ 0 and 0.5) cathode materials were prepared by solid state
reaction method. The synthesized materials are characterized by X-ray diffraction analysis (XRD),
scanning electron microscopy (SEM) and Fourier infrared transform spectra (FTIR) studies. All the X-ray
diffraction peaks of both the compounds are indexed and it is found that the samples are well crystallized
in orthorhombic olivine structure belonging to the space group Pnma. The crystallite size is calculated
from the Scherer's formula and it is found to be 6.918 and 4.818 nm for pure and doped samples
respectively. The surface morphology and grain sizes of the materials are investigated through scanning
electron microscope. Presence of preferred local cation environment is understood from Fourier transform
infrared spectroscopy (FTIR) studies. The assembled lithium cells were electrochemically characterized
by charge/discharge and cyclic voltammetry. It is found that the specific capacities of samples
with LiNi 1-x CoxPO4 (x ¼ 0, 0.5) are about 172.4 mAhg_1 and 173.2 mAhg_1 respectively. The efficiency is
slightly improved after cobalt substitution. Based on the above results, the cobalt substituted LiNiPO4
cathode material has been tried as effective substituent.

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