Chu, Po‐JuiPo‐JuiChuHuang, Jheng‐YiJheng‐YiHuangLiu, Yu‐ShuoYu‐ShuoLiuChang, Yun‐PingYun‐PingChangHung, Yuan‐TingYuan‐TingHungChiang, Ching‐YuChing‐YuChiangShao, Yu‐ChengYu‐ChengShaoHsieh, Wan‐ZhenWan‐ZhenHsiehIshii, HirofumiHirofumiIshiiLiu, Ru‐ShiRu‐ShiLiu2026-02-102026-02-102026-01-20https://scholars.lib.ntu.edu.tw/handle/123456789/735903Li+ diffusion has mostly been studied in cathode active materials (CAMs) in liquid batteries, whereas it remains rarely explored in solid-state electrolytes (SSEs) and all-solid-state batteries. Herein, diffraction was established as an effective method for all-solid-state lithium batteries (ASSLBs) by focusing on SSE in composite cathodes. Operando synchrotron x-ray diffraction presented diffraction angle shifts of certain Li3InCl6 Bragg planes during the first ASSLB cycle due to lithiation/delithiation into its lattice, whose preferred Li+ migration pathways were suggested by the partiality of these shifts, and the three-phase evolution indicated the fundamental Li+ diffusion kinetics factors. X-ray nanodiffraction (XND) mapped nanoscale inhomogeneous Li+ distributions and diffusion within individual Li3InCl6 particles, revealing facilitated Li+ conduction in high-crystallinity regions and their role as pathways across SSE/CAM interfaces, and the most negatively strained regions were shown to be less susceptible to Li+ insertion. XND from various electrochemical techniques inferred high transient charging rates to be the culprit of irreversible Li+ diffusion instead of the overall charging depth. This study proved diffraction to be a potent tool to probe intricate Li+ dynamics in ASSLBs and provide microscopic insights for optimal battery designs.enAll-Solid-State batteryComposite cathodeLi-ion diffusionOperando diffractionjournal article10.1002/anie.202520281