Studies of cycleability of LiMn2O4 and LiLa0.01Mn1.99O4 as cathode materials for Li-ion battery

LiMn2O4 spinel and LiLa(0.01)jMn(1.99)O(4) were synthesized and the structure and morphology were characterized by X-ray diffraction (XRD) and field emission scanning electronic microscopy. Galvanostatic charge-discharge experiment shows that doping only 1% La into the spinel can improve the cycling stability effectively. The mechanism responsible for the improvement of cycling behavior was extensively investigated by electrochemical impedance spectroscopy, XRD and cyclic voltammogram. The results show that the different changes of impedances for LiMn2O4 and LiLa0.01Mn1.99O4 electrodes underlie their electrochemical performances between them. La doping can protect the spinel structure against electrochemical lithiation/delithiation and slows down the increase of electrode impedance, and thus improves the electrochemical properties greatly. LiLa0.01Mn1.99O4 spinel exhibits good cycling performance and shows 90.5% capacity retention after 300 cycles with an average discharge capacity of more than 110 mA h g(-1). (c) 2006 Elsevier B.V. All rights reserved.