Influence of calcium doping on performance of LaMnO3 supercapacitors

Capacitive energy storage is distinguished from other types of electrochemical energy storage by short charging times, long life cycles, and ability to deliver significantly more power densities than batteries. In this study, Ca-doped perovskite lanthanum manganites (La(1-x)Ca(x)Mno(3), LCMs) were prepared by sol-gel method and used as electrode materials of supercapacitors. Microstructures, morphologies and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD) cycling. Among prepared materials, (La1-xCaxMnO3, with x = 0.50) showed low intrinsic resistance of 2.13 Omega cm(2) and large specific surface area of 23.0 m(2) g(-1). The maximum specific capacitance obtained with this sample reached 170 F g(-1) at current density of 1 A g(-1) in 1 M KOH aqueous electrolyte solutions. However, LCMs encountered serious elements leaching, limiting their applications as electrode materials of super capacitors due to their poor cycling stabilities. To clarify this phenomenon, charge storage mechanism of LCMs and leaching elements in alkali solutions were investigated, and oxygen anion charge storage mechanism was studied by charge-discharge processes. Data revealed that charge storage of oxygen intercalation improved by doping with elements of low valence in perovskite manganites. Improvements in electrochemical performances of manganite electrodes require new effective methods prohibiting cations leaching in Ca-doped LaMnO3.