Comparison of structural changes in fully delithiated Li-x[Ni1/3Co1/3Mn1/3]O-2 and Li-x[Ni0.33Co0.33Mn0.30Mg0.04]O1.96F0.04 cathodes (x=0) upon thermal annealing

Abstract

This study compared the structural changes in Lix [Ni13 Co13 Mn13] O2 and Lix [Ni0.33 Co0.33 Mn0.3 Mg0.04] O1.96 F0.04 cathodes (x=0) occurring after full delithiation and subsequent heat-treatment at 200, 300, and 400°C using X-ray diffraction (XRD), transmission electron microscopy, and X-ray absorption spectra (XAS). In both cathodes, XRD patterns at x=0 showed a layered O3 -type structure (CdCl2), but subsequent thermal annealing led to a similar structure decomposition to a Co3 O4 -type spinel and possible new O3- Ni13 Mn13 O2+δ -type layered phases. However, the XAS spectra clearly showed that the Lix [Ni0.33 Co0.33 Mn0.3 Mg0.04] O1.96 F0.04 exhibited much improved structural stability, showing a suppression of the phase decomposition to spinel Co3 O4, as evidenced by a decrease in the FT peak intensity of corner-shared CoO6 octahedra at ∼3.2 Å.