Application of 5V spinel material LiNi0.5Mn1.5O4 in Li-ion batteries: single crystalline or polycrystalline?

Abstract

The 5V spinel LiNi_0.5Mn_1.5O₄ cathode materials with different morphology were prepared by a solid state calcination method and characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), field emission scanning electron microscope (FE-SEM). Electrochemical properties of cathode material were investigated by electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT) and electrochemical performance tests. Compared with polycrystalline morphology (PLNMO), LiNi_0.5Mn_1.5O₄ material with single crystalline morphology (SLNMO) proved smaller electrochemical polarization or voltage difference, lower internal resistance, faster lithium-ion diffusivity, arising from higher Mn³⁺ content. Differential scanning calorimetry (DSC) showed that SLNMO was more stable than PLNMO at full charged state with organic electrolyte, which exhibited initial discharge capacity of 140.2 mA h g⁻¹ at 0.1C, coulombic efficiency of 96.1%, and specific capacity retention of 89.2% after 200 cycles at 2.5C, a little inferior to that of 91.7% for PLNMO.