A bottom-up, component-resolved framework combining DSC/TGA, evolved gas analysis, and in situ XRD reveals how decomposition pathways control energy release in partial and micro-cell configurations. Separator-free assemblies are dominated by cathode-O2${rm O}_2$/anode-Li reactions, while the separator restricts oxygen transport, reshapes the reaction network, lowers net energy release, and provides a transferable foundation for safety assessment and thermodynamic modeling.
ABSTRACT
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 O2${rm O}_2$ and anode-leached Li dominates the net heat release (1139 J g−1${rm g}^{-1}$). In contrast, in the micro-cell configuration, the separator hinders O2${rm O}_2$ transport and alters the timing and pathways of other reactions, and reduces the net energy release to 618 J g−1${rm g}^{-1}$. 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.