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@ARTICLE{Newnham:1042708,
author = {Newnham, Jon A. and Kondek, Jędrzej and Hartel, Johannes
and Rosenbach, Carolin and Li, Cheng and Faka, Vasiliki and
Gronych, Lara and Glikman, Dana and Schreiner, Florian and
Wind, Domenik D. and Braunschweig, Björn and Hansen,
Michael Ryan and Zeier, Wolfgang G.},
title = {{C}orrelation between the {C}oherence {L}ength and {I}onic
{C}onductivity in ${L}i{N}b{OC}l_4$ via the {A}nion
{S}toichiometry},
journal = {Chemistry of materials},
volume = {37},
number = {11},
issn = {0897-4756},
address = {Washington, DC},
publisher = {American Chemical Society},
reportid = {FZJ-2025-02654},
pages = {4130-4144},
year = {2025},
note = {Bundesministerium für Bildung und Forschung (BMBF) funding
under the FESTBATT cluster of competence (project
03XP0430F)},
abstract = {$LiNbOCl_4$ is a recently reported material with high
$Li^+$ conductivities of ∼10 $mS·cm^{–1}$ at room
temperature. Here, we explore how changing the anion ratio
and the $Li^+$ content in the
$Li_{1–x}NbO_{1–x}Cl_{4+x}$ series (−0.4 ≤ x ≤
0.2) affects the ionic conductivity of the material. In
doing so, we find that the maximum coherence length and
ionic conductivity of $LiNbOCl_4$ are highly dependent on
the $O^{2–}$/$Cl^–$ anion ratio in the material.
Specifically, we show that, while an amorphous phase
fraction of $LiNbOCl_4$ remains constant throughout the
substitution series, any excess of $O^{2–}$ results in a
rapid decrease in the maximum coherence length of the
crystaline fraction in each sample. Through a combination of
diffraction and spectroscopic techniques, we show that this
occurs because the $O^{2–}$ anions cannot exist on the
terminal sites of the $[NbOCl_4]_∞^{–}$ chains in the
material, even when it is made with an excess of $O^{2–}$
resulting in a shortening of those chains. In contrast, it
was observed that $Cl^–$ can occupy the bridging sites
resulting in a dependence of the coherence length to the
anion ratio. As such, the ionic conductivity of $LiNbOCl_4$
can be maximized by controlling the maximum coherence length
in the material through the anion ratio. Notably, we
achieved high ionic conductivities for $LiNbOCl_4$
consistent with literature reports only when the material
was slightly $Li^+$ and $O^{2–}$ deficient, suggesting
that the literature samples may also have been
off-stoichiometry. In addition, we highlight the features
missing from the current structural models of $LiNbOCl_4$
including the presence of mixed $Cl^–$/$O^{2–}$ sites,
even in the stoichiometric material, which were previously
thought to not exist. Finally, we show that slightly
reducing the $Li^+$ and $O^{2–}$ contents in $LiNbOCl_4$
also translates to higher capacities when it is used as a
catholyte in solid-state batteries. These findings show the
importance of careful control of the stoichiometry in
$LiNbOCl_4$ to optimize its properties and highlights the
potential of $LiNbOCl_4$ for use as a catholyte in
solid-state batteries.},
cin = {IMD-4},
ddc = {540},
cid = {I:(DE-Juel1)IMD-4-20141217},
pnm = {1221 - Fundamentals and Materials (POF4-122)},
pid = {G:(DE-HGF)POF4-1221},
typ = {PUB:(DE-HGF)16},
UT = {WOS:001492363800001},
doi = {10.1021/acs.chemmater.5c00627},
url = {https://juser.fz-juelich.de/record/1042708},
}