Precise preparation of high performance spherical hierarchical LiNi0.5Mn1.5O4 for 5 V lithium ion secondary batteries

This work developed a novel ammonium oxalate-carbonate composite co-precipitation method to prepare spinel LiNi0.5Mn1.5O4. By this method combined with a facile hydrothermal treatment and particular cooling process, an ideal spinel with precise stoichiometric Ni/Mn and classic Fd3m structure is obtained, and furthermore, the Mn3+ content can be strictly limited. Additionally, the prepared LiNi0.5Mn1.5O4 has a spherical hierarchical morphology, composed of nano or submicron primary particles. This LiNi0.5Mn1.5O4 shows superlative electrochemical performance. It delivers a discharge capacity of 141.2 mA h g(-1), and importantly 98.2% of which discharges at 4.7 V. After 200 cycles at 0.3 C, 1 C and 3 C, the capacity retentions are 96.3%, 94.4% and 91.1%, respectively. Chemical and electrochemical measurements indicate that the elimination of the majority of Mn3+ in the obtained LiNi0.5Mn1.5O4 results in the high capacity proportion at 4.7 V. Additionally, the retained Fd3m structure and spherical hierarchical morphology also effectively favour the cycling and rate performances.