Facile synthesis of porous LiMn2O4 spheres as positive electrode for high-power lithium ion batteries

A LiMn2O4 cathode material with novel porous spherical morphology exhibiting excellent electrochemical performance has been successfully prepared by using Delta *a-MnO2 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 LiMn2O4 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 LiMn2O4 cathode a promising candidate for high-power lithium ion batteries which may be used in demanding application such as electric vehicles.