Li-ion diffusional insights and temperature dependent electrical & dielectric properties of LiNi1/3Mn1/3Co1/3PO4 electrodes

Abstract

Enhancing the electrical conductivity of the cathode is crucial for improving the overall performance of modern lithium-ion (Li-ion) batteries. In this study, a facile sol-gel thermolysis technique was employed to synthesize LiNi_1/3Mn_1/3Co_1/3PO₄, using ethylene-di-amine-tetra-acetic acid (EDTA) as the chelating agent. This method ensures a uniform distribution of metal ions, which is vital for achieving consistent and reliable material properties. This study employed solid-state impedance to investigate the electrical conductivity and Bond Valence Site Energy (BVSE) analysis to find the Li-ion trajectory within the proposed LiNi_1/3Mn_1/3Co_1/3PO₄ compound. Especially, the conductivity analysis revealed the small polaron hopping mechanism, a process in which charge carriers move through the crystal lattice by hopping from one localized site to another. The conductance spectra revealed that at 473 K, the compound exhibited a high DC conductivity of 6.88 x 10⁻⁶ S cm⁻¹, which indicates that the material maintains a reasonable electrical conductivity at elevated temperatures for high-performance battery applications. The activation energy for conduction, determined from the Arrhenius plot, was found to be 0.14 eV, suggesting that the compound has a relatively low energy barrier for charge carrier movement. The half-cell of LiNi_1/3Mn_1/3Co_1/3PO₄ as cathode demonstrates an initial discharge capacity of 94 mAh g⁻¹ at 0.1 C in the potential window from 2 to 4.8 V vs. Li/Li⁺. The bond valence site energy (BVSE) modeling provided critical insights into the Li-ion migration within the cathode material. The analysis revealed a one-dimensional (1D) Li⁺ migration barrier of 0.919 eV and a hopping distance of 1.86 Å. These findings infer the potential of LiNi_1/3Mn_1/3Co_1/3PO₄ as a promising candidate for Li-ion energy storage applications.