STRUCTURAL, MORPHOLOGICAL, DIELECTRIC AND IMPEDANCE STUDY OF LITHIUM IRON PHOSPHATE (LIFEPO4)

Abstract

Lithium-ion batteries are getting more attention as prominent energy storage devices because of its high-power energy density and better cyclability compared to other energy storage devices. With the growing interest in developing rechargeable batteries, For the next generation of Li-ion batteries, lithium iron phosphate (LiFePO4) is one of the potential cathode materials because of its more cyclic stability, environmental friendliness and economic viability. Here in this study, The LiFePO4 cathode material has been synthesized using a solid-state reaction method using two-step heating under different calcination temperatures in a reduced inert atmosphere. Pre-heating results in decomposition and calcination at high temperatures leading to the crystallization of LiFePO4. Primary LiFePO4 was synthesized by preheating at 350 0C and calcinated at 750 0C. The structural, morphology, elemental distribution and Impedance with Dielectric study of synthesized pristine LiFePO4 are carried out by X-ray powder diffraction (XRD), Field emission Scanning electron microscopy (FE-SEM), and electrochemical impedance spectroscopy (EIS), respectively. XRD result shows an orthorhombic olivine structure with a “Pnma” space group of LFP. The crystallite size of 36 nm and the strain in an atom of 8.6*10-4 has been observed as estimated from Scherrer's equation and W-H plot, respectively. The physical characterizations and the particle-size distribution data supported the aggregation and sintering observed by the SEM during the calcination process. The electrical properties and impedance are measured by impedance spectroscopy over the temperature range of 50 to 150 °C. It reveals the diffusion of Li+ ion in pristine LiFePO4. Dielectric analysis shows the charge storage capacity of LiFePO4 concerning the variation of temperature and dielectric loss in pristine LiFePO4 samples.