Unraveling li-ion percolation and interfacial resistance in sulfide-based all-solid-state batteries: A quantitative diagnostic tool for cathode composite analysis

초록

The performance of sulfide-based all-solid-state batteries is critically limited by percolation-related transport bottlenecks in the cathode composite and interfacial resistance at the solid-state electrolyte-cathode active material (CAM) interface. Here, we establish an impedance-derived electrochemical descriptor, percolation resistance (Rper), to quantitatively evaluate percolation-related Li-ion transport limitations within complex cathode architectures. Using electrochemical impedance spectroscopy (EIS) combined with distribution of relaxation times (DRT) analysis, we distinguish cathode composite transport limitations from the onset and growth of interfacial resistance under operating conditions. A transport-limited cathode composite regime is identified, in which Rpe(r) sharply increases beyond a critical CAM loading, indicating reduced continuity of effective ionic pathways. Notably, the cathode with 85 wt% CAM exhibits reduced Rper, reaching 52.2 Omega at 60 degrees C. Elevated temperature alleviates transport limitations, whereas prolonged exposure accelerates interfacial degradation, revealing a fundamental competition between kinetic activation and interfacial instability. Voltagedependent impedance further pinpoints the onset of interfacial resistance growth. Cross-pairing analyses further clarify the relative roles of CAM and catholyte in the evolution of interfacial resistance under the present conditions. Overall, this work establishes an experimentally accessible electrochemical diagnostic protocol for diagnosing transport-related limitations and interfacial degradation in cathode composites, providing practical guidance for high-CAM-loading cathode composites in all-solid-state batteries.

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