Effect of A-Site Substitution on LaMnO3 Perovskite via Sr Ions for Energy Applications

The inherently reduced electrical conductivity of transition metal oxides as electrodes in supercapacitors is of major concern to attain enhanced electrochemical performance. In this connection, efforts have been made to synthesize the perovskite oxide LaMnO3 by doping of Sr at the La site, i.e., La1-xSrxMnO3 (LSM) via the conventional sol-gel method. Powder x-ray diffraction pattern confirms the absolute phase formation of LSM nanoparticles with hexagonal structure. The micro-structural properties observed via scanning electron microscopy (SEM) show large specific surface area for charge storage. Among all samples, the La0.85Sr0.15MnO3 (LSM15) sample shows a higher value of current (0.054 A at 2 V and 0.145 A at 3 V) and higher conductivity. The cyclic voltammetry (CV) results displayed pseudo-capacitive behavior. The highest obtained specific capacitance for the symmetric LSM15 electrode is 40.5 F g(-1) at a scanning rate of 20 mV s(-1) in 0.5 M H2SO4. With the increase in scan rate, there is a decreasing trend seen in specific capacitance which shows low electrochemical performance at higher scan rates. The electrochemical impedance spectroscopy measurements confirmed that LSM is a dynamic supercapacitor candidate due to subsequent decrease in resistance with Sr doping in LaMnO3 which shows enhanced conductivity.