Investigation of the structural and electrical behavior of LiFePO4 as cathode material for energy storage application

Abstract

The present work reports the structural and electrochemical impedance spectroscopy (EIS) of LiFePO4 cathode material synthesized via hydrothermal technique by using CTAB (Cetrimonium bromide) as a surfactant. XRD analysis reveals that LiFePO4 crystallizes in the orthorhombic phase with Pnma space group. The average crystallite size calculated through Scherrer formula is found to be 21 nm. FESEM analysis divulges that as synthesized sample have disc type morphology and the size distribution was found to be in the range of 150–650 nm. The electrochemical analysis is done using a three-electrode technique with Ag/AgCl as the reference electrode. Cyclic Voltammetry (CV) results confirm the anodic and cathodic current peaks corresponding to the oxidation and reduction reactions respectively. The standard cell potential estimated through the CV plots is found to be, Eʘ = 0.34. The electrolytic resistance and charge transfer resistance estimated through EIS plots in the frequency range of 10–105 Hz with 2 M NaOH solution as the electrolyte is found to be, Rsol = 4.1 Ω, and Rct = 35 Ω, respectively. Simulation for an equivalent circuit model is done using CHI760E software which confirms the partially polarizable nature of the as-prepared LiFePO4 cathode material. The impedance behavior of LiFePO4 cathode material can be analyzed to verify its physicochemical properties, hence, the study concludes that as synthesized LiFePO4 can be utilized as an efficient cathode material for energy storage applications.