Enhanced oxygen reducibility of 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 cathode material with mild acid treatment

Abstract

Solid solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 has been synthesized by a co-precipitation method and a mild acid was adopted to give rise to the H+/Li+ exchange reaction. The inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectroscopy (AAS) data show that the H+/Li+ exchange reaction actually occurs and the chemical composition is H0.06Li1.15Ni0.13Co0.14Mn0.55O2.03 after the material was treated. The X-ray powder diffraction patterns indicates that the structure doesn't change through the H+/Li+ exchange reaction and remains the hexagonal α-NaFeO2 layered structure with space group of R-3m. The field-emission scanning electron microscope (SEM) and transmission electron microscope (TEM) images show that there are traces of erosion on the surface of the H+/Li+ exchanged sample. The initial charge–discharge curve measured at 0.05C (12.5 mA g−1) demonstrates that the H+/Li+ exchanged electrode delivers a capacity of up to 314.0 mAh g−1 and coulombic increased initial efficiency. Cycle voltammetry (CV) measurement confirms this is attributed to the improvement of the reduction catalytic activity of oxygen released during the initial charging. The processed electrode also displays improved rate performance.