Abstract
LiNi0.5Mn1.5O4 (LNMO), an extended compound of spinel LiMn2O4, possesses the advantages of safety and long cycle life. In recent years, LiNi0.5Mn1.5O4 has been extensively studied due to its high operation voltage around 4.7V (versus Li/Li+), which is higher that of the commonly used cathode material LiCoO2. Bare LNMO suffered severe capacity fading during charge/discharge at elevated temperature. In this study, the cyclability of LNMO cells at 55oC can be significantly improved by adding 3 wt% nano-Al2O3 powders into LNMO electrodes. In comparing nano-Al2O3 contained with bare-LNMO cells, the former exhibite better electrochemical performance. After 100 cycles at 55oC, nano-Al2O3 contained LNMO cells preserve 83% of initial capacity whereas the capacity retention of bare LNMO cells is 66%. The main reason for better electrochemical performance of nano-Al2O3 contained LNMO cells is owing to the alleviation of increasing in cell impedance during 55oC cycling. It can be reasonably correlated to the suppression of formation of high resistive LiF on the surface of active masses, which is identified by FE-EPMA and XPS analysis. Furthermore, to increase the power capability and to meet the requirement of new generation LIBs for EV/HEV, LiNi0.5Mn1.5O4 is expected to be capable of fast charge/discharge. In this study, high current rate capability and single phase LiNi0.5Mn1.5O4 powders were successfully produced via a novel synthesis procedure combining sol-gel route with combustion method. Through this approach, well-crystallized LiNi0.5Mn1.5O4 powders with nano-structure were obtained at a low temperature of 600oC. Nano-structured LiNi0.5Mn1.5O4 half-cells have exhibited superior electrochemical performances. At a slower discharge rate, a capacity of 133mAh/g could be delivered. Moreover, the nano-structured LiNi0.5Mn1.5O4 delivered a capacity of 122mAh/g at a discharge rate as high as 10C. Thus, a superior power capability was achieved.