Tailoring\nthe Fueling Capability of Halide Solid Catholyte\nthrough Composition. Correlation with the Underlying Redox Mechanism

Halide-based solid electrolytes have gained renewed interest\nfor\nall-solid-state batteries (ASSBs). In this study, using synchrotron\nX-ray and neutron diffraction, MAS <sup>7</sup>Li NMR, and operando\n(online) mechanical cell pressure and online electrochemical mass\nspectrometry gas measurements, we investigate the relationship between <i>x</i>LiCl–ZrCl<sub>4</sub> (LZC) catholyte composition,\nstructure, and the resulting electrochemical performance of LFP-based\nelectrodes. It is shown that tuning the catholyte composition significantly\nimproves the performance of these blend electrodes. In addition, we\ndemonstrate that the sacrificial capacity of LZC can be enhanced by\na factor of 28 across the composition range, offering significant\nindustrial potential for full cells. Overall experiments reveal that\nthe oxidative redox mechanism of LZC correlates with self-induced\nmechanical cell pressure changes during cycling, which can be further\ncorrelated to the proven Cl<sub>2</sub> gas evolution. This research\nadvances our understanding of halide SEs and provides practical insights\nfor developing next-generation ASSBs.