Synthesis, Structure, and Electrochemistry of Sm-Modified LiMn_2O_4 Cathode Materials for Lithium-Ion Batteries

摘要

Spinel lithium manganese oxide and a series of Sm/LiMn_2O_4 spinels with different Sm additive contents (x = 0.02%, 0.05%) were prepared for the first time via a coprecipitation method for rechargeable lithium-ion batteries. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive analysis of x-rays (EDAX), infrared (IR), and electron spin resonance spectral studies as well as various electrochemical measurements were used to examine the structural and electrochemical characteristics of LiMn_(2-x)Sm_xO_4 (x = 0.00%, 0.02%, 0.05%). XRD and SEM studies confirmed the nano materials size for all prepared spinels. From cyclic voltammetry studies, in terms of peak splitting, electrochemical active surface area, and intensity of the peaks, the LiMn_(1.98)Sm_(0.02)O_4 sample possesses better electrochemical performance compared with the LiMn_(1.95)Sm_(0.05)O_4 sample. Hence, limited addition of a rare-earth dopant is preferable to obtain better efficiency. Direct-current (DC) electrical conductivity measurements indicated that these samples are semiconducting and their activation energies decrease with increasing rare-earth Sm~(3+) content.