Functional surface modifications of a high capacity layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode

Abstract

With an aim to enhance the electrochemical performances of the high capacity layered oxide solid solution Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode, its surface has been modified with 2 wt.% Al2O3, 2 wt.% RuO2, and 1 wt.% Al2O3 + 1 wt.% RuO2. The bare samples and the surface-modified samples have been characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (TEM), charge–discharge measurements in lithium cells, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The surface-modified samples exhibit much improved electrochemical performances, particularly the 1 wt.% Al2O3 + 1 wt.% RuO2 coated sample exhibiting the highest discharge capacity and rate capability. Specifically, the Al2O3 + RuO2 coated sample delivers ∼280 mAh g−1 at C/20 rate with a capacity retention of 94.3% in 30 cycles and ∼ 160 mAh g−1 at 5 C rate. The superior electrochemical performances of the Al2O3 + RuO2 coated sample are attributed to the suppression of SEI layer formation and the facilitation of fast electron transfer and lithium ion diffusion channels as evident from the EIS and XPS data.