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

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_0.8Mn_0.1Co_0.1O₂ (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.