Full‐Dimensional Analysis of Gaseous Products to Unlocking In Depth Thermal Runaway Mechanism of Li‐Ion Batteries

Abstract In this study, state‐of‐the‐art on‐line pyrolysis MS (OP‐MS) equipped with temperature‐controlled cold trap and on‐line pyrolysis GC/MS (OP‐GC/MS) injected through high‐vacuum negative‐pressure gas sampling (HVNPGS) programming are originally designed/constructed to identify/quantify the dynamic change of common permanent gases and micromolecule organics from the anode/cathode–electrolyte reactions during thermal runaway (TR) process, and corresponding TR mechanisms are further perfected/complemented. On LiC x anode side, solid electrolyte interphase (SEI) would undergo continuous decomposition and regeneration, and the R‐H + (e.g., HF, ROH, etc.) species derived from electrolyte decomposition would continue to react with Li/LiC x to generate H 2 . Up to above 200 °C, the O 2 would release from the charged NCM cathode and organic radicals would be consumed/oxidized by evolved O 2 to form CO x , H 2 O, and more corrosive HF. On the contrary, charged LFP cathode does not present obvious O 2 evolution during heating process and the unreacted flammable/toxic organic species would exit in the form of high temperature/high‐pressure (HT/HP) vapors within batteries, indicating higher potential safety risks. Additionally, the in depth understanding of the TR mechanism outlined above provides a clear direction for the design/modification of thermostable electrodes and non‐flammable electrolytes for safer batteries.