Single crystalline polyhedral LiNixMn2-xO4 as high-performance cathodes for ultralong cycling lithium-ion batteries

Abstract

A series of single crystalline spinel LiNixMn2-xO4 (0 ≤ x ≤ 0.10) cathode materials were synthesized in virtue of a facile solution-combustion approach. The morphology and the structure of all as-prepared samples were synthetically investigated with the X-ray diffraction (XRD), the scanning electron microscopy (SEM), the high-resolution transmission electron microscopy (HRTEM), and the X-ray photoelectron spectrometer (XPS). According to these investigation results, Ni-doping content has a significant impact on the control of morphology and crystalline structure, hence the as-prepared LiNixMn2-xO4 samples exhibit polyhedral morphology with high crystallinity and average size of 100–200 nm. This unique polyhedral crystal structure has numerous surfaces fitting the (111) crystalline orientation which exhibit the smallest Mn dissolution in electrolytes, whilst stabilizing the spinel framework. Owing to the merits of both single crystalline polyhedral structure and appropriate Ni-doping, the as-obtained LiNixMn2-xO4 cathodes reveal enhanced rate capability coupled with long cycling performance. In especial, the LiNi0.08Mn1.92O4 presents a initial discharge capacity of 101.3 mAh/g and ultralong cycle stability up to 2000 cycles at 1C, whilst showing enhanced cycle performance when temperature increases to 55 °C. Excellent capacity retention of 72% and 63% is also obtained after 1000 cycles even at high current rate of 5C and 10C. This study may contribute to an effective candidate approach for the obvious improvement on lithium ion batteries in term of electrochemical activity.