Linking DSC/TGA to Cell Levels: Energetics, Evolved Gases, and Thermal Safety of NMC811‐Graphite Micro‐Cell
Ayrton M. Yanyachi, Lingmin Lin, Siddhartha Nanda, Wenlong Li, Yijin Liu, Steven Swinnea, Hadi Khani, Donal Finegan, Ofodike A. EzekoyeABSTRACT
Thermochemical characterization of battery materials links intrinsic material properties to decomposition pathways, heat generation, and gas evolution that govern performance and safety. Despite extensive work on NMC811‐Graphite, variability across partial configurations and the limited adoption of micro‐cell architectures (cathode+anode+electrolyte+separator) hinder robust cell‐scale interpretation. Accordingly, this work establishes a bottom‐up, component‐resolved methodology integrating DSC/TGA, evolved gas analysis (EGA), and in situ XRD to link decomposition pathways and energy release across partial and micro‐cell configurations, providing a transferable assessment of safety and stability in emerging chemistries. In separator‐free configurations, the gas–solid reaction between cathode‐evolved and anode‐leached Li dominates the net heat release (1139 J ). In contrast, in the micro‐cell configuration, the separator hinders transport and alters the timing and pathways of other reactions, and reduces the net energy release to 618 J . Energy release was organized into defined temperature windows that provide a framework for a thermodynamic model combining quantified gas evolution with selected decomposition pathways and effective reaction enthalpies to estimate net specific energy release, with agreement between DSC and cell‐level tests. Ex situ XPS of heat‐treated samples extends post‐mortem analysis to thermal‐abuse regimes, supporting key pathway elements.