The effect of LaMnO3 with high electronic conductivity on the high rate charge-discharge performance of LiMn2O4

Abstract

The effect of LaMnO3 with high electronic conductivity on the fast charge-discharge rate performance of LiMn2O4 is studied. X-ray diffraction patterns confirm the existence of LaMnO3 and also indicate LaMnO3 has no influence on the crystal structure of pristine LiMn2O4. The transmission electron microscopy (TEM) images indicate that LaMnO3 coating layer, about 15nm thickness, covers the surface of LiMn2O4 well. The electrochemical performances are evaluated by galvanostatic charge/discharge tests and electrochemical impedance spectroscopy (EIS). At 0.5C/0.5C, LaMnO3 coated LiMn2O4 delivers an initial capacity of about 114mAhg−1 along with the coulombic efficiency of 95.0%, which are higher than those of uncoated LiMn2O4 (106mAhg−1 and 89.1%). Furthermore, LaMnO3 coated LiMn2O4 can exhibit higher capacities at high charge-discharge rates than uncoated LiMn2O4. It can deliver about 90.6mAhg−1 at 10C/10C and 68.0mAhg−1 at 20C/20C, but there are only 53.6mAhg−1 and 43.3mAhg−1 for bare LiMn2O4. Electrochemical impedance spectroscopy (EIS) demonstrates that LaMnO3 coating layer can effectively reduce the electrodes' resistances and improve the kinetics of electrodes. The improved high rate properties of LaMnO3 coated LiMn2O4 are ultimately ascribed to the easier phase conversion from λ-MnO2 to Li0·5Mn2O4 which is related to LaMnO3 coating layer with high electronic conductivity.