A Model for Investigating Sources of Li-Ion Battery Electrode Heterogeneity: Part II. Active Material Size, Shape, Orientation, and Stiffness

Abstract

This work is the extension of our previous paper [Nikpour et al., J. Electrochem. Soc. 168 060547, 2021] which introduced the multi-phase smoothed particle (MPSP) model. This model was used to simulate the evolution of the microstructure during the drying and calendering manufacturing processes of four different electrodes. The MPSP model uses particle properties to predict overall film properties such as conductivities and elastic moduli and is validated by multiple experiments. In this work the model is used to investigate the effects of active material particle size, shape, orientation, and stiffness on graphitic anodes. The model predicts that smaller active particles produce higher calendered film density, electronic conductivity, MacMullin number, and Young’s modulus, as compared to larger active particles. Rod-shaped active materials have greater ionic transport and lower electronic transport compared to the disk and sphere shapes, which have similar transport properties. During calendering, disk-shaped particles tend to be oriented horizontally, which decreases through-plane ionic transport. Increasing the stiffness of the active material increases film porosity and composite Young’s modulus, while lowering electronic transport and increasing ionic transport.

Li-Ion Battery Electrode Contact Resistance Estimation by Mechanical Peel Test

“…This may be caused by the change in the active material ratio including a significant decrease in graphite and a change in particle size. 41 These changes could lead to an improved slurry distribution or changes to the mobility during drying. This may be indicative of non-linear effects when varying active material ratios.…”

Insights into Influencing Electrode Calendering on the Battery Performance

“…They found in previous manufacturing models that DEM can have unstable interfaces while trying to maintain liquid‐ and solid‐type behavior, a disadvantage that can be compensated for by employing the SPH model in a DEM‐style environment. They used a similar model in another study [ 60 ] to investigate the effects of AM particle shape, size, orientation, and stiffness on the resulting microstructure after calendering. Ngandjong et al [ 61 ] also employed a DEM type model to investigate multiple processing steps, including slurry preparation, drying, calendering, and eventually, the electrochemical processes in the electrode, as demonstrated in Figure 5 a.…”

Carbon-Binder Weight Loading Optimization for Improved Lithium-Ion Battery Rate Capability

“…5,20 Another approach consists in modeling the manufacturing steps, from slurry equilibration to calendering. Different numerical methods have been investigated in the literature, coarsegrained molecular dynamics (CGMD) and discrete element method (DEM) for A. Franco's group, 41,42 multi-phase smoothed particle (MSMP) for D. Wheeler's group 43,44 and DEM for S. Roberts' group. 45 The drying mechanisms, partly responsible for binder migration, 35,36 are however not fully understood yet 44 which may result in some uncertainty in the actual CBD spatial distribution.…”