Optical and electrical conduction mechanisms of the ceramic LiMnO₂ as cathode active materials for lithium-ion batteries

Next-generation batteries expected to utilize solid-state lithium-ion technology due to their excellent energy density, safety, and stability characteristics. Novel materials for solid electrolytes exhibiting high ion conductivity have been extensively studied lately. This study reports the effective use of the traditional solid-state approach to manufacture a new solid electrolyte, LiMnO₂. They were examined using X-ray powder diffraction, infrared and Raman spectroscopies, scanning electron microscope analysis, and optical and impedance spectroscopy. The sample was represented by a single monoclinic crystal structure with C₂/m space groups, according to the X-ray diffraction pattern. Fourier transform infrared and Raman spectroscopies showed the vibrational modes of the LiMnO₂ compound and proved the presence of the octahedral environment MO₆ (M = Mn, Li), which is in good agreement with the structural study. The compound’s semiconductor characteristics were verified by the optical measurement, indicating a band gap of approximately 3.31 eV. Additionally, the material’s electrical properties were examined using impedance spectroscopy within the temperature range of 303 to 423 K and the frequency range of 10⁻¹ to 10⁶ Hz. The frequency behavior of the AC conductivity was analyzed using the universal Jonscher’s law. The outcomes of the investigation into charge transportation in LiMnO₂ indicated that this compound had both a non-overlapping small polaron tunneling (NSPT) model for T < 353 K and a correlated barrier hopping (CBH) model for T > 353 K. A correlation between the ionic conductivity and the crystal structure was established and discussed.