Role of Alumina Coating on Li−Ni−Co−Mn−O Particles as Positive Electrode Material for Lithium-Ion Batteries

Abstract

The interface reaction between Al2O3-coated Li[Li0.05Ni0.4Co0.15Mn0.4]O2 and liquid electrolyte was investigated. The Al2O3-coated Li[Li0.05Ni0.4Co0.15Mn0.4]O2 showed no large difference in the bulk structure, comparing to bare Li[Li0.05Ni0.4Co0.15Mn0.4]O2. The coated Al2O3 was found to have an amorphous structure from X-ray diffraction study. A small amount of Al2O3 coating (0.25 wt % in the final composition) showed that a uniform mesoporous Al2O3-coating layer whose thickness is of about 5 nm covers Li[Li0.05Ni0.4Co0.15Mn0.4]O2 particles, as confirmed by transmission electron microscopy. At higher concentration (2.5 wt % in the final composition), the irregular tens of nanometer-sized Al2O3 powders were observed on the surface of the active material instead of the uniform coating layer. Despite the insulating nature of Al2O3, the thin coating was effective to improve the battery performances, depending on the thickness of the Al2O3-coating layer, and used electrolytic salt. The Al2O3 coating resulted i...