Charge-clustering induced fast ion conduction in 2LiX-GaF3: A strategy for electrolyte design | Science Advances
Abstract
2LiX-GaF
3
(X = Cl, Br, I) electrolytes offer favorable features for solid-state batteries: mechanical pliability and high conductivities. However, understanding the origin of fast ion transport in 2LiX-GaF
3
has been challenging. The ionic conductivity order of 2LiCl-GaF
3
(3.20 mS/cm) > 2LiBr-GaF
3
(0.84 mS/cm) > 2LiI-GaF
3
(0.03 mS/cm) contradicts binary LiCl (10
−12
S/cm) < LiBr (10
−10
S/cm) < LiI (10
−7
S/cm). Using multinuclear
7
Li,
71
Ga,
19
F solid-state nuclear magnetic resonance and density functional theory simulations, we found that Ga(F,X)
n
polyanions boost Li
+
-ion transport by weakening Li
+
-X
−
interactions via charge clustering. In 2LiBr-GaF
3
and 2LiI-GaF
3
, Ga-X coordination is reduced with decreased F participation, compared to 2LiCl-GaF
3
. These insights will inform electrolyte design based on charge clustering, applicable to various ion conductors. This strategy could prove effective for producing highly conductive multivalent cation conductors such as Ca
2+
and Mg
2+
, as charge clustering of carboxylates in proteins is found to decrease their binding to Ca
2+
and Mg
2+
.