Preparation of spherical hierarchical LiNi0.5Mn1.5O4 with high electrochemical performances by a novel composite co-precipitation method for 5Â 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 mAh g−1 and a high initial columbic efficiency of 98.1%, importantly 98.2% of the capacity discharges at 4.7 V 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 4.7 V 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.