Unraveling Sudden Death of High-Specific-Energy Lithium-Ion Batteries

High-specific-energy NCM811/Si@C lithium-ion cells (LIBs, ≥300 Wh kg -1 ) show great potential for military applications like unmanned aerial vehicles and portable soldier power systems. However, their susceptibility to sudden death during cycling threatens long-term operational stability, limiting large-scale deployment. To date, the underlying mechanism of this sudden death remains controversial and incompletely understood. Herein, using elaborately designed experiments and appropriate characterization techniques, we provide evidence for a positive feedback mechanism associated with the sudden death observed in the cells. First, the growth of the electrode-electrolyte interfacial (EEI) film continuously depletes the electrolyte, causing gradual increases in interfacial and liquid-phase polarization. Once exceeding a certain threshold, lithium plating occurs on the anode even under normal charging. Subsequently, the plated lithium reacts with the electrolyte, accelerating growth of the solid electrolyte interphase (SEI) film and generating trace amounts of gases (e.g., , and ), which further boosts polarization. The rapid increase in polarization may further promote lithium plating and gas evolution, forming a positive feedback loop that ultimately triggers sudden death. Furthermore, it is demonstrated that the polarization increase is primarily attributable to anode degradation, rather than cathode degradation. Our findings establish a clear physical picture of sudden death of high-specific-energy NCM811/Si@C LIBs, implying that future research should prioritize anode performance enhancement, particularly via interfacial engineering, to extend lifespan and mitigate sudden death risks. While these findings are derived from a limited sample set, future studies will seek to validate their broader applicability across diverse high-energy cell formats and material systems by extending this work to larger sample sets and alternative high-specific-energy cell chemistries.