Untersuchungen an elektronenleitenden Oxidsystemen. XXIII. Struktur und Eigenschaften stabiler Spinelle in den Reihen M_zNiMn_2−ZO₄ (M=Li, Fe)

Abstract

Es wird über die Darstellung und Eigenschaften der Spinellverbindungen LiZNiMn2−ZO4 (0 ⩽ Z ⩽ 2/3) und FeZNiMn2−ZO4 (0 ⩽ Z ⩽ 1) berichtet und die Reihe ZnZNiMn2−ZO4 (0 ⩽ Z ⩽ 1) einbezogen. Im Unterschied zur Ausgangsverbindung NiMn2O4 (Z=0) erweisen sich die Spinelle Z ≥ 1/6 beim Tempern (400−500°C) an Luft als thermodynamisch stabil. In den Reihen mit M=Li oder Zn erfährt die obere thermodynamische Stabilitätsgrenze eine Herabsetzung, nicht dagegen in der Reihe mit M=Fe. Die Veränderungen werden strukturchemisch interpretiert und die elektrischen Eigenschaften im Zusammenhang mit der Kationenverteilung im Rahmen des Polaronenmodells diskutiert.

Coating versus Doping: Understanding the Enhanced Performance of High‐Voltage Batteries by the Coating of Spinel LiNi0.5Mn1.5O4 with Li0.35La0.55TiO3

“…[33]), a lattice parameter of, e.g., 816.4 pm [34] to 817.0 pm [35] are expected. As already discussed in detail for very similar materials back in 1993 by Feltz et al, [36] advocated by Cabana in the recent LNMO debate, [34,37,38] and concluded from our preceding work, [39] the higher Mn(III) content most likely is a side effect of the formation of the Ni-rich secondary phase, coming along with a Ni-depletion of the LNMO phase:…”

“…[33]), a lattice parameter of, e.g., 816.4 pm [ 34 ] to 817.0 pm [ 35 ] are expected. As already discussed in detail for very similar materials back in 1993 by Feltz et al., [ 36 ] advocated by Cabana in the recent LNMO debate, [ 34,37,38 ] and concluded from our preceding work, [ 39 ] the higher Mn(III) content most likely is a side effect of the formation of the Ni‐rich secondary phase, coming along with a Ni‐depletion of the LNMO phase: $$\[ \begin{array}{*{20}{c}}{{\rm{LiNi}}_{0.5}^{{\rm{II}}}{\rm{Mn}}_{1.5}^{{\rm{IV}}}{{\rm{O}}_4} \rightleftharpoons {\rm{LiNi}}_{0.5 - y}^{{\rm{II}}}{\rm{Mn}}_{1.5 - y}^{{\rm{IV}}}{\rm{Mn}}_{2y}^{{\rm{III}}}{{\rm{O}}_4} + {\rm{L}}{{\rm{i}}_x}{\rm{N}}{{\rm{i}}_{1 - x}}{\rm{O}} + {{\rm{O}}_2}}\end{array} \]$$According to Equation (), chemical equilibrium shifts to the right side when calcination is carried out above the decomposition temperature (often referred to as the oxygen release temperature) and to the left for lower calcination temperatures. However, the back reaction may be limited by excessive phase segregation and kinetic restraint.…”

Unveiling the Reaction Mechanism during Li Uptake and Release of Nanosized “NiFeMnO4”: Operando X-ray Absorption, X-ray Diffraction, and Pair Distribution Function Investigations

“…A distribution of Mn 3+ /Fe 3+ over the two sites was reported for cubic NiMnFeO 4 synthesized at elevated temperatures. 36,49,50 Although the occupation pattern of the sites seems to be obvious, the ratio of Mn 3+ and Fe 3+ on the tetrahedral site cannot be determined using the present experimental data. In all three spectra (Figure 6), an intense signal is observed that is due to the spin-allowed 1s → 4p transition.…”

“…We note that NiMnFeO 4 adopts cubic symmetry if the sample was prepared at higher temperatures. 36,49,50 Remarkably, a Rietveld refinement of the XRD pattern using the tetragonal model yielded no improvement of the refinement (better R value). This emphasizes that the tetragonal distortion is a local phenomenon and is averaged out into a strained yet still cubic symmetry on a global scale.…”

“…On a tetrahedral site, the degeneracy of the d 4 electronic configuration is removed, leading to a flattening of the MnO 4 tetrahedron whereas for Mn 3+ on an octahedral site, an elongation of MnO 6 octahedra is expected. We note that NiMnFeO 4 adopts cubic symmetry if the sample was prepared at higher temperatures. ,, Remarkably, a Rietveld refinement of the XRD pattern using the tetragonal model yielded no improvement of the refinement (better R value). This emphasizes that the tetragonal distortion is a local phenomenon and is averaged out into a strained yet still cubic symmetry on a global scale.…”