Facile synthesis of porous LiMn 2O 4 spheres as positive electrode for high-power lithium ion batteries

Abstract

A LiMn 2O 4 cathode material with novel porous spherical morphology exhibiting excellent electrochemical performance has been successfully prepared by using α-MnO 2 urchin-like structure as a self-sacrificial template. These cathode powders are characterized with X-ray powder diffractometry (XRD), field-emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller (BET) method and inductively coupled plasma emission spectrometry (ICP-AES). Furthermore, electrochemical properties have been studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge/discharge cycling at various current rates. The results reveal that the porous LiMn 2O 4 spheres possess outstanding high rate capability and extremely high cycle stability at room temperature as well as elevated temperature. When tested at 10 C and 20 C rates, the first discharge capacities are up to 93.7 and 76.0 mAh g −1. After 1000 cycles, the corresponding retention rates of capacities are more than 71% and 62% at room temperature. When cycled at 60 °C and 10 C rate, the first discharge capacity is 61.1 mAh g −1 between 3 and 4.5 V. After tested for 250 cycles at 60 °C, the retention rate of capacity is over 76%. This makes the porous LiMn 2O 4 cathode a promising candidate for high-power lithium ion batteries which may be used in demanding application such as electric vehicles.