DOI: https://doi.org/10.55373/mjchem.v28i2.128

Keywords: Au-LiFePO₄, cathode materials, lithium-ion battery, first principles study, mechanical and electronic properties

Abstract

Improving the performance of LiFePO₄ cathode materials is critical for developing safer batteries and achieving high efficiency. Although their performance is hindered by low electronic conductivity, doping with transition metals can be used to enhance the structural, mechanical and electronic properties of LiFePO₄. In this work, the properties of gold-doped LiFePO₄ were investigated using first-principles calculations based on density functional theory (DFT), with the exchange–correlation effects treated by applying the Generalized Gradient Approximation (GGA) and the GGA+U method. Gold (Au) was selected as a dopant because of its unique electronic configuration, large atomic radius, chemical inertness and suitability for theoretical benchmarking. An iron (Fe) atom of LiFePO₄ was replaced with Au. Upon doping, the volume change between the delithiated and lithiated phases of Au-LiFePO₄ was reduced from 5.8 % to 1.7 % compared to LiFePO₄. The crystal system of Au-LFP exhibited mechanical stability and good ductility; however, its strength and stiffness were slightly lower than those of the undoped crystal. The band gap reduction from 3.8 eV to 2.19 eV indicated improved electrical conductivity. The open circuit voltage (OCV) increased from 3.7 V to 4.7 V. Further, the migration energy of lithium ions decreased from 0.783 eV to 0.378 eV, demonstrating enhanced ionic conductivity. All these desirable properties are expected to improve the overall performance of LiFePO₄.