A microstructural electrochemo-mechanical model of high-nickel composite electrodes towards digital twins to bridge the particle and electrode-level characterizations†

Abstract

Cell-level battery models, most of which rely on the successful porous electrode theories, effectively estimate cell performance. However, pinpointing the contributions of individual components of an electrode remains challenging. In contrast, particle-level models based on real microstructures describe active material characteristics but do not accurately reflect performance under cell-level operating conditions. To bridge this modeling gap, we propose a microelectrode modeling framework that considers each component of a composite electrode. This framework enables us to analyze the complex electrochemo-mechanical relationships within the composite electrode. The realistic 3D microstructure of the LiNi_0.7Mn_0.15Co_0.15O₂ composite electrode is reconstructed from focused ion beam-scanning electron microscopy images. By applying the intrinsic properties of every component, the composite microelectrode model achieves more than 98% accuracy in terms of the voltage profile compared to the measurement on coin cells. This model allows us to identify three important mechanisms that contribute to the discrepancy between cell and particle levels, i.e., reduced reaction area, increased diffusion length, and insufficient amount of electrolyte. Simulations under excessive electrolyte conditions reveal a significant improvement in rate capability with 94% capacity retention at 4C. In addition, the model considers the role of conductive materials and binders as well as the viscoplasticity of the polymeric binder, enabling the study of degradation mechanisms involving the stability of the binder-particle connection.