Operando Quantifying Li Plating Processes in Lithium‐Ion Pouch Cells

Lithium‐ion batteries require high reliability and extended lifespan for practical grid storage applications, yet Li plating remains a critical hazard inducing rapid capacity fade and safety risks. The transient and heterogeneous nature of Li plating poses a significant challenge to real‐time quantitative detection. Herein, we define a critical Li‐plating areal capacity (q Li ) derived from dynamic electrochemical impedance spectroscopy (DEIS) and establish an operando strategy to accurately quantify Li plating under diverse charging conditions. Validated by operando solid‐state nuclear magnetic resonance (ssNMR)‐DEIS combined measurements, incremental capacity analysis, and mass spectrometry titration (MST), this method demonstrates high reliability, exceptional accuracy (R 2 > 0.97), and general validity across different temperatures (0°C–45°C) and battery capacities (4 to 110 mAh). A transmission line model (TLM) elucidates the physical origin of q Li : it corresponds to the critical surface coverage (∼10%, model‐derived) of lithium nuclei on graphite, marking the transition from nucleation‐dominated to growth‐controlled deposition. We further demonstrate that regulating temperature can switch the nucleation mode, thereby significantly altering q Li and the resulting plating characteristics. This study establishes a robust operando quantification platform, enabling early battery warning and adaptive fast charging to suppress excessive Li plating and extend service life in practical cells.