Preparation of spherical hierarchical LiNi0.5Mn1.5O4 with high electrochemical performances by a novel composite co-precipitation method for 5 V lithium ion secondary batteries

A novel composite co-precipitation method is developed to prepare high performance LiNi0.5Mn1.5O4. Combined with a facile hydrothermal treatment, a precise stoichiometric LiNi0.5Mn1.5O4 is obtained. The product has classic Fd3m structure, and meanwhile the content of Mn3+ is strictly limited. Additionally, the as-prepared LiNi0.5Mn1.5O4 has a spherical hierarchical morphology, composed of nano or submicron primary particles. Compared to traditional methods, the obtained LiNi0.5Mn1.5O4 shows superlative electrochemical performances. It delivers a high capacity of 144.9 mAhg(-1) and a high initial columbic efficiency of 98.1%, importantly 98.2% of the capacity discharges at 4.7V plateau. After 200 cycles under 0.3 C, 1 C and 3 C, the material retains 96.3%, 94.4% and 91.1% of the original capacities, respectively. Chemical and electrochemical measurements indicate that it is the elimination of Mn3+ in the spinel that leads to the high capacity of LiNi0.5Mn1.5O4 discharging at 4.7V high voltage. The spherical hierarchical morphology as well as the retained Fd3m structure effectively favors the rates performance. In addition, this hierarchical morphology also plays a significant role in improving the tap density of the cathode material. (C) 2013 Elsevier Ltd. All rights reserved.