Surface and bulk composition of lithium manganese oxides

Abstract

Lithium manganese oxides, and in particular the spinel-structured LiMn 2 O 4 , have been investigated as potential active cathode materials for lithium ion batteries. Recently both orthorhombic and monoclinic LiMnO 2 have attracted considerable attention. It has been reported that Al doping allows the preparation of monoclinic LiAl x Mn 1−x O 2 under suitable reaction conditions, and furthermore improves the capacity retention of both o-LiAl x Mn 1−x O 2 and m-LiAl x Mn 1−x O 2 . The aim of this study was to elucidate the structural effects of Al doping with particular attention to the surface properties of the material. X-ray diffraction data reveal that Al induces monoclinic stacking faults in orthorhombic LiAl x Mn 1−x O 2 and at Al contents of ~5% the preferred cation ordering becomes that of monoclinic LiAl x Mn 1−x O 2 . X-ray photoelectron spectroscopy measurements show that the Al is homogeneously incorporated throughout the grains up to its solubility limit, and no surface enrichment of Al is observed. The XPS data indicate that Mn in the near-surface region of the material is predominantly present in its Y3 oxidation state, even when annealed to temperatures of up to 250 °C.

Understanding the Origin of Li2MnO3 Activation in Li‐Rich Cathode Materials for Lithium‐Ion Batteries

“…To identify the valence state of Mn and Ni in the pristine Li 1.87 Mn 0.94 Ni 0.19 O 3 composite, X‐ray photoelectron spectrometry (XPS) was performed and the spectra of Mn‐ and Ni‐2p is shown in Figure b,c. The Mn 2p 3/2 binding energy is around 642.2 eV, which is consistent with that of Mn 4+ . Generally, the Ni 2p 3/2 energy in XPS is around 854 eV for Ni 2+ and 856 eV for Ni 3+ .…”

Osteogenic potential of sol–gel bioactive glasses containing manganese

“…species [55], indicating the majority presence of Mn 2+ in the bioactive glass structure. In fact, previous works have shown that oxidation states such as +4 and +7 are unlikely in silicate systems and that this ion is normally present as Mn 2+ in these structures, although Mn 3+ can also be observed, shifting the Mn 2p bands to higher binding energy values [56][57][58]. The spectra also showed similar shape and Mn 2p position, indicating that even after incorporation of different Mn contents on the glass structure, the Mn chemical environment was maintained.…”

Oxidation behaviour of lattice oxygen in Li-rich manganese-based layered oxide studied by hard X-ray photoelectron spectroscopy

“…S2 †). 33,34 The main peak remains almost unchanged on the charging to 4.8 V (Sps. #2-6), indicating that the tetravalent Mn ions have no contributions to charge compensation on the initial charging process.…”