This project focuses on the intricate, often overlooked, and unavoidable imperfections within composite electrodes used in all-solid-state batteries. Understanding this “microstructure” is crucial for advancing battery technology with improved safety and energy density. By examining how these features behave during synthesis and electrochemical cycling, the research aims to uncover their impact on lithium diffusion and structural integrity. This study is significant because it fills a critical knowledge gap and advances solid-state battery technology. Beyond the scientific advancements, the project has broad societal impacts by fostering sustainable energy technologies and promoting diversity and inclusivity in STEM fields. By leveraging the diverse demographics of Cornell University and Arizona State University, the project will engage underrepresented communities in materials science through outreach initiatives targeting K-12 students and inter-institutional collaborations. These efforts aim to inspire a passion for STEM, cultivate a diverse future workforce, and enhance the interdisciplinary and inclusive nature of scientific research, ultimately contributing to national health, prosperity, and welfare.<br/> <br/>The project investigates the microstructure, including grain boundaries, secondary phases, and defects, within composite electrodes composed of solid-state electrolytes and cathode active materials. The research aims to quantify defect formation mechanisms and monitor operando microstructural evolution, and to elucidate to what extent these changes impact the mechanical and electrochemical properties of the electrodes. By combining tailored synthesis, advanced electrochemical characterization, real-time operando x-ray techniques, including single-particle diffraction and coherent imaging, and rigorous modeling, this study promises to unravel the profound influence of microstructural defects on ionic transport, mechanical resilience, and fracture toughness, paving the way for the development of high-performance solid-state batteries.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.