Electrochemical properties and kinetics of Li–Cu co-doping LiMn2O4 cathode materials

Abstract

Li1.05Cu0.05Mn1.90O4 cathode materials were synthesized by liquid phase combustion method at different temperatures from 400 to 700 °C. All samples show good crystallinity and conform to the Fd3m space group of spinel LiMn2O4. The Li1.05Cu0.05Mn1.90O4 sample prepared at 600 °C has a sharp diffraction peak compared to the pristine LiMn2O4, while no impurities are detected. Both the Li–Cu co-doping and calcination temperature have effects on the morphology and particle size distribution. The electrochemical properties reveal that initial discharge capacity of the Li1.05Cu0.05Mn1.90O4 is 102.4 mAh g−1 and pristine LiMn2O4 electrode is 105.3 mAh g−1. After 1000 cycles, the capacity retention rate of the pristine LiMn2O4 (63.0%) has less than 74.3% of the Li1.05Cu0.05Mn1.90O4 sample. The lithium-ion diffusion coefficient indicates that the as-prepared Li1.05Cu0.05Mn1.90O4 electrode (1.58 × 10−10 cm2 s−1) at 600 °C displays better Li+ diffusion ability when compared with the pristine LiMn2O4 (8.06 × 10−11 cm2 s−1). Simultaneously, the apparent activation energy further demonstrates that the Li1.05Cu0.05Mn1.90O4 (22.84 kJ/mol) electrode has lower polarization when compared with the LiMn2O4 (34.95 kJ/mol) electrode. These results show that synergistic effect of the Li+ and Cu2+ enhances the cycle reversibility and kinetics properties in cycle of the electrode.