posted on 2023-12-11, 19:20authored byKern-Ho Park, Se Young Kim, Mina Jung, Su-Bin Lee, Min-Jeong Kim, In-Jun Yang, Ji-Hoon Hwang, Woosuk Cho, Guoying Chen, KyungSu Kim, Jisang Yu
Halide solid electrolytes (SEs) have been highlighted
for their
high-voltage stability. Among the halide SEs, the ionic conductivity
has been improved by aliovalent metal substitutions or choosing a
ccp-like anion-arranged monoclinic structure (C2/m) over hcp- or bcc-like anion-arranged structures. Here,
we present a new approach, hard-base substitution, and its underlying
mechanism to increase the ionic conductivity of halide SEs. The oxygen
substitution to Li2ZrCl6 (trigonal, hcp) increased
the ionic conductivity from 0.33 to 1.3 mS cm–1 at
Li3.1ZrCl4.9O1.1 (monoclinic, ccp),
while the sulfur and fluorine substitutions were not effective. A
systematic comparison study revealed that the energetic stabilization
of interstitial sites for Li migration plays a key role in improving
the ionic conductivity, and the ccp-like anion sublattice is not sufficient
to achieve high ionic conductivity. We further examined the feasibility
of the oxyhalide SE for practical and all-solid-state battery applications.