Effect of Li addition on structural, electrical and electrochemical properties on lanthanum manganite

摘要

The addition of aliovalent element plays an important role on the structural, electrical and electrochemical properties of LaMnO_3. In this study, 10 percent of Li was incorporated into the A-site of the LaMnO_3 perovskite. The addition of more than 10 percent Li resulted in the formation of the LiMn_2O_4 spinel as a second phase. The conductivity of LaMnO_3 was also effectively enhanced by the addition of Li. The undoped LaMnO_3 exhibits a conductivity of 0.25 OMEGA~(-1) cm~(-1) at 27 deg C. In the LaMnO_3 sample doped with 10 percent Li, the conductivity increased to 2.25 OMEGA~(-1) cm~(-1) at 27 deg C. For 30 percent Li-doped LaMnO_3, the lower conductivity of 1.31 OMEGA~(-1) cm~(-1) at 27 deg C was observed due to the formation of poor-conducting LiMn_2O_4. In all the samples doped with Li, the activation energy (17.20-18.17 kJ/mol) for electrical conduction was much lower than that of undoped LaMnO_3 (26.71 kJ/mol). The reduction in activation energy can be rationalized by the creation of electron holes due to the addition of Li. In the sample with the composition of La_(0.9)Li_(0.1)MnO_3, the cyclic voltammetry and charge/discharge tests indicated that the sample was not electrochemically active.