Two Different Type Defects in Nano-Structured High Voltage LixNi(0.5)Mn1.5O(4)(x equals to 0.96, 0.98, 1.0, 1.02 and 1.04) with an Fd-3m Space Group

LixNi0.5Mn1.5O4 microspheres (x = 0.96, 0.98, 1.0, 1.02, and 1.04), which consist of nanometer-sized primary particles with different lithium contents, were synthesized by an ammonia-mediated carbonate precipitation method. The effects of lithium content on the structure, morphology, and electrochemical characteristics of the prepared microspheres were investigated in detail. Two types of defects in LixNi0.5Mn1.5O4, which is in the Fd-3m space group, were identified: Li vacancies (x = 0.96 and 0.98) and Li on Ni sites (x = 1.02 and 1.04). X-ray diffraction with Rietveld refinement revealed that approximately 35% of the total manganese in LixNi0.5Mn1.5O4 is Mn3+. We suggest that most of the Mn3+ did not participate in the reaction during charging and discharging, and the 4.0 V platform of this material cannot be used to accurately estimate the Mn3+ content. Li1.0Ni0.5Mn1.5O4, which had no defects, exhibited the best electrochemical performance, retaining a capacity of 146.5 mAh g-1 after 10 cycles at