Probing Active Particle Assembly in Lithium-Ion Battery Electrode Processing

Lithium-ion batteries (LIB) are currently considered as the primary choice for electric drive vehicles. The electrode microstructure and composition play an important role in determining the performance of the LIB. To this end, the processing of the multi-phase slurry consisting of active nanoparticles, conductive additives, binder and solvent determines the electrochemical properties and performance of the electrode. Morphology and the size of the active nanoparticles affect the LIB performance due to large active surface area, short diffusion length and fast kinetics.  On the contrary, the aggregation of the active nanoparticles might have a detrimental effect. Therefore, fundamental understanding of the aggregation behavior of the active particles in the slurry is of paramount importance.

In this regard, the evaporation dynamics of the slurry is a key factor which determines the microstructural heterogeneity of the electrode. The morphology of the aggregated particles is governed by a variety of physicochemical factors such as interaction between nanoparticles, diffusion rate of the nanoparticles and evaporation rate of the solvent. In this work, we present a mesoscale modeling approach in order to investigate the influence of evaporation on active particle assembly in LIB electrode processing. Our mesoscale model is based on a coarse-grain formalism combining lattice gas and kinetic Monte Carlo methodologies.  We will present a comprehensive study of the active particle aggregation behavior and resultant influence due to the (1) evaporation rate of the solvent, (2) active particle and binder interaction, and (3) active particle morphology. Figure 1 shows representative aggregation characteristics of different active particle morphology. 

    Reference

1. J. Li, B. L. Armstrong, J. Kiggans, C. Daniel and D. L. Wood, Langmuir, 28, 3783-3790 (2012).
2. J. Li, C. Daniel and D. L. Wood, Journal of Power Sources, 196, 2452-2460 (2011).
3. H. Zheng, R. Yang, G. Liu, X. Song and V. S. Battaglia, Journal of Physical Chemestry C, 116, 4875-4882 (2012).
4. E. Rabani, D. R. Reichman, P. L. Geissler and L.ha E. Brus, Nature, 426, 271-274 (2003).