Study of the structural and thermal stability of Li0.3Co 2/3Ni1/6Mn1/6O2

Abstract

Thermal and structural stabilities of the delithiated positive electrode material LixCo2/3Ni1/6Mn1/6O 2were studied by X-ray diffraction, magnetic and thermogravimetric analysis. In the opposite to the classical electrode materials LiNiO2 and LiCoO2, the structural symmetry (S.G. R-3 m) of the starting material LiCo2/3Ni1/6Mn1/6O2 is preserved during the electrochemical cycling with a small variation of the unit cell parameters. Squid measurements evidenced that practically no Ni 2+ ions were present in the lithium slab even after the lithium extraction process. For the thermal stability, the highly oxidized phase Li 0.3Co2/3Ni1/6Mn1/6O2 was tested. This delithiated phase undergoes only 5.16% weight loss after heating up to 600 °C. This weight loss has no effect on the structure symmetry as the starting α-NaFeO2 type structure was preserved during the thermal treatment. The obtained results coupled to the excellent electrochemical features of LiCo2/3Ni1/6Mn1/6O 2clearly showits ability to compete with the commercialized cathode materials.