Mechanically robust halide electrolytes for high-performance all-solid-state batteries.

All-solid-state batteries frequently encounter mechanical instability due to the inherent brittleness and low elasticity of inorganic ceramic electrolytes, such as sulfides, oxides, and halides. These electrolytes struggle to accommodate the volumetric fluctuations of positive electrode materials during cycling, potentially leading to performance degradation and premature failure. To address this challenge, we propose a defect-based toughening approach for resilient halide solid electrolytes. By meticulously controlling the cooling rate during synthesis, we successfully increase the defect density within the electrolyte, enhancing its mechanical properties and mitigating the risk of mechanical failure. Mechanical property testing, high-resolution transmission electron microscopy characterization, and synchrotron radiation diffraction analysis reveal that the quenched material exhibit not only a higher Young's modulus, rendering it less susceptible to deformation under stress and a higher capacity for energy absorption before plastic deformation or fracture due to its increased dispersed defect density. Consequently, it demonstrates better adaptability to the volumetric changes associated with the positive electrode material during battery cycling, effectively mitigating strain-induced material behavior. Here we show the effectiveness of defect-enhanced toughening strategies in optimizing the mechanical properties and microstructure of electrolyte materials, thereby enhancing the overall integrity of solid-state batteries without requiring modifications to their chemical composition.