Tailoring the Fueling Capability of Halide Solid Catholyte through Composition. Correlation with the Underlying Redox Mechanism

Halide-based solid electrolytes have gained renewed interest
for
all-solid-state batteries (ASSBs). In this study, using synchrotron
X-ray and neutron diffraction, MAS 7Li NMR, and operando
(online) mechanical cell pressure and online electrochemical mass
spectrometry gas measurements, we investigate the relationship between xLiCl–ZrCl4 (LZC) catholyte composition,
structure, and the resulting electrochemical performance of LFP-based
electrodes. It is shown that tuning the catholyte composition significantly
improves the performance of these blend electrodes. In addition, we
demonstrate that the sacrificial capacity of LZC can be enhanced by
a factor of 28 across the composition range, offering significant
industrial potential for full cells. Overall experiments reveal that
the oxidative redox mechanism of LZC correlates with self-induced
mechanical cell pressure changes during cycling, which can be further
correlated to the proven Cl2 gas evolution. This research
advances our understanding of halide SEs and provides practical insights
for developing next-generation ASSBs.