Quantitative and Non‐Destructive Analysis of Failure Process of Pouch Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) are emerging as a promising next‐generation energy storage technology. Understanding failure mechanisms under operational conditions and quantifying the real‐time evolution of lithium metal anodes (LMAs) are critical for enhancing the performance and safety of pouch‐type LMBs. In this study, liquid nuclear magnetic resonance–titration mass spectrometry (NMR‐TMS) is employed to quantitatively characterize the dynamic evolution of inactive and active Li under various conditions. By combining scanning electron microscopy (SEM) with phase‐field simulations, the underlying failure mechanisms are elucidated. Importantly, fiber Bragg grating (FBG) sensing technology is implemented to achieve real‐time, non‐destructive monitoring of internal stress evolution in pouch‐type LMBs under varying current densities. This study provides direct experimental validation of the three‐stage failure mechanism under fast charging conditions. Through optimized charge/discharge protocols, LMAs failure behavior is significantly mitigated, leading to a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) || Li pouch cell in lean electrolyte conditions (that is, 2.1 g Ah −1 ), with 90.5% capacity retention for 300 cycles at 0.2C/1C (charge/discharge) condition. The mechanistic insights not only establish systematic methods for failure detection but also offer strategic guidance for performance optimization and failure mitigation in next‐generation LMBs of high‐safety.