Influence of Li content on the structure and electrochemical performance of Li1+xNi0.25Mn0.75O2.25+x/2 cathode for Li-ion battery

The cathode materials of Li1+xNi0.25Mn0.75O2.25+x/2 (X = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) with different content of lithium have been synthesized in this paper. The materials with different lithium content show distinct differences in structure and charge/discharge characteristics. The layered-spinel composite structure has been detected in the Li1+xNi0.25Mn0.75O2.25+x/2 electrodes, when the lithium content is lower than 1.5. The coulomb efficiency of Li1+xNi0.25Mn0.75O2.25+x/2 electrode is increased with the content of lithium decreasing. The cyclic and rate performances of layered-spinet composite electrodes Li1+xNi0.25Mn0.75O2.25+x/2 (0 <= X <= 0.4) are better than that of layered Li1.5Ni0.25Mn0.75O2.24. Among the < < layered-spinel composite electrodes, Li1.5Ni0.25Mn0.75O2.25 electrode shows the best capacity retention (98.2% for 40 cycles) and rate capacity (102 mAh g(-1) at 10 degrees C), while that of Li1+xNi0.25Mn0.75O2.25+x/2 are 94.5% for 40 cycles and 11 mAh g(-1) at 10 degrees C. Electrochemical impedance spectroscopy (EIS) results show that the charge transfer resistance (R-ct) of Li1.5Ni0.25Mn0.75O2.24 electrode is lower than that of Li1.5Ni0.25Mn0.75O2.25. The enhanced cyclic and rate performances of Li1.5Ni0.25Mn0.75O2.25 cathode are attributed to the lower Rct, three-dimensional interstitial space of LiNi0.5Mn1.5O4 phase and the lower content of Li2MnO3 in Li1+xNi0.25Mn0.75O2.25+x/2 cathode material. (C) 2013 Elsevier B.V. All rights reserved.