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

Abstract

This work developed a novel ammonium oxalate–carbonate composite co-precipitation method to prepare spinel LiNi_0.5Mn_1.5O₄. 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 LiNi_0.5Mn_1.5O₄ has a spherical hierarchical morphology, composed of nano or submicron primary particles. This LiNi_0.5Mn_1.5O₄ 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 LiNi_0.5Mn_1.5O₄ 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.