Synthesis and investigation on the optical and complex impedance analysis in LiCrO2 prepared using solid-state reaction

Abstract

Lithium-ion batteries (LIB) have been employed extensively as energy delivery and storage technologies in electronic devices, electric cars, and utility grids. In this paper, the LiCrO2 compound was successfully synthesized using the solid-state method. The X-ray powder diffraction (XRPD) data confirmed the formation of a single-phase with a rhombohedral structure (R3̅m space group). The surface morphology of the compound was studied by scanning electron microscopy (SEM), to find that the average size is around 3.5 µm. UV-Vis-NIR diffuse reflectance and impedance spectroscopy thoroughly investigated the optical and electrical properties. The optical band gap is approximately 2.2 ± 0.1 eV for direct transition, determined using the absorption spectrum. The latter proves a semiconductor characteristic of the studied sample. The Nyquist plots (-Z" vs. Z′) display the contribution of grains and grain boundaries in the electrical conductivity, confirming the existence of a non-Debye type relaxation. The studied compound displays enhanced capacitance behavior, semiconducting properties that follow the Arrhenius relation, and an increase in conductivity as a function of frequency for different voltage values in the range of 0.5–3 V. The best electrical response in terms of capacitance and conductivity was found for the voltage value of 3 V. This study will expand knowledge by shedding light on the electrical conductivity for this value. The hopping of charge carriers over the potential barrier and the tunneling of polarons created because of lattice deformation at high bias voltages combine to produce the electrical conduction in this ceramic.