Understanding Multiscale Lithium Transport Dynamics in Composite Si‐C Electrodes: An Asymptotic Framework for GITT Experiments

ABSTRACT This work presents an asymptotic analysis of lithium transport phenomena during a galvanostatic intermittent titration technique (GITT) pulse‐relaxation cycle in electrodes combining composite silicon‐carbon (Si‐C) aggregates and graphite particles. The study demonstrates that asymptotic techniques offer both physical insight into the complex interplay of transport mechanisms—namely, lithium exchange between silicon and graphite, diffusion within active particles, and exchange between graphite and composite particles—and contribute to efficient parameter identification. A key challenge in characterising composite Si‐C electrodes via GITT lies in the presence of very disparate time scales associated with the relevant transport phenomena. This fact results in a cell behaviour during the GITT test completely different with respect to homogeneous electrodes. The asymptotic framework developed here explains how the interplay among these transport phenomena affects the observed cell voltage during the experiments and why GITT tests must be adapted for reliable identification of blended electrode parameters, providing guidance for the design of such adapted experiments. Although applied here to a single pulse‐relaxation cycle, the methodology is general and can be extended to other operating conditions or composite electrode systems.