Dielectric and electrochemical performance of rhombohedral lanthanum manganite perovskite nanostructures

Abstract

Among the wide range of nanomaterials, lanthanum-based perovskite oxide nanostructures have recently gained a lot of attention as efficient electrode materials for supercapacitors. However, the poor cycling stability of these perovskite oxides is one of the main issues that affect the performance of these energy devices. In the present work, we report a facile sol–gel assisted method to synthesize rhombohedral LaMnO₃ nanostructures, which are highly stable compared to the phases usually obtained in other methods. Upon studying the effect of annealing temperature in the formation of these nanostructures from 600 °C to 1000 °C, it was concluded that high-purity samples are only formed at temperatures equal to or above 700 °C. The structure, crystallinity, morphology and porosity of these nanostructures were studied using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and Brunauer–Emmett–Teller analysis. It has been seen that the sample prepared at 700 °C (L7) has the smallest crystallite size and better porosity among the prepared samples, which are desirable for supercapacitor electrodes. The L7 electrode on carbon cloth exhibits an areal capacitance of 133.24 mF cm⁻² at a current density of 1 mA cm⁻² and retains 71.4% of the initial capacitance even after 5000 charge–discharge cycles at a high current density of 10 mA cm⁻². Moreover, it displays the lowest dielectric loss and highest dielectric constant. The smaller crystallite size, better porosity, dielectric characteristics, high electrochemical performance and better cycling stability of L7 make it a perfect candidate for supercapacitor applications.