Brownian dynamics simulations of colloidal suspensions containing polymers as precursors of composite electrodes for lithium batteries

Effects of the mixing sequence on the graphite dispersion and resistance of lithium-ion battery anodes

The performance of lithium-ion battery electrodes is influenced by particle dispersion in the slurry used for their production. In this study, we elucidate the effects and mechanism of the binder mixing sequence on the characteristics of the slurry used in the production of negative electrodes. Therefore, we optimize the preparation of the negative electrode slurry by evaluating the electrode characteristics resulting from changing the binder mixing sequence. During the preparation of the electrode slurry, the state of the adsorption of the binder to the particle changes when the sequence of binder addition is changed. The change in the adsorption state of the binder influences the particle dispersion in the slurry, rheological properties of the slurry, and packing characteristics of the particles. Under the influence of the aforementioned changes, electrodes possessing identical compositions exhibited different performances. The slurry in which the particles were dispersed produced an electrode possessing a low volume-resistivity, whereas the slurry in which the particles were agglomerated produced an electrode with a high volume-resistivity. Evidently, controlling the adsorption state of the binder by altering the binder mixing sequence is essential for fabricating electrodes possessing a low volume-resistivity.

Boosting Rechargeable Batteries R&D by Multiscale Modeling: Myth or Reality?

This review addresses concepts, approaches, tools, and outcomes of multiscale modeling used to design and optimize the current and next generation rechargeable battery cells. Different kinds of multiscale models are discussed and demystified with a particular emphasis on methodological aspects. The outcome is compared both to results of other modeling strategies as well as to the vast pool of experimental data available. Finally, the main challenges remaining and future developments are discussed.

Computer simulations of heteroaggregation with large size asymmetric colloids

HYPOTHESIS

Hetero-aggregation of inorganic colloids is influenced by numerous parameters, which dictate the suspension properties. When particles are different in size, the suspension can be either stable or unstable according to concentration of components, ionic strength, and pH. Experimentally, understanding the role of each parameter is sometimes difficult because parameters cannot easily be modified independently. Numerical simulations are thus very useful to discriminate between different effects.

SIMULATIONS

Brownian dynamics simulations are used here to study the heteroaggregation of dilute suspensions composed of two populations of colloids with large size asymmetry. Special attention is paid to the effect of small-particle concentration, surface potentials, and ionic strength.

FINDINGS

The simulation results show that hetero-aggregation can be tuned by modifying these different parameters, and that the resulting aggregate structures depend more on the surface properties of small particles than on those of large particles. The simulations shed light on a further parameter crucially influencing hetero-aggregation, i.e. the mobility of small particles when adsorbed on large ones. The present results rationalize numerous experimental observations reported in the literature and can be used as reference to explain future experimental observations.

Self-Organization of Electroactive Suspensions in Discharging Slurry Batteries: A Mesoscale Modeling Investigation

We report a comprehensive modeling-based study of electroactive suspensions in slurry redox flow batteries undergoing discharge. A three-dimensional kinetic Monte Carlo model based on the variable step size method is used to describe the electrochemical discharge of a silicon/carbon slurry electrode in static mode (i.e., no fluid flow conditions). The model accounts for Brownian motion of particles, volume expansion of silicon upon lithium insertion, and formation and destruction of conducting carbon networks. Coupled to an electrochemical model, this study explores the impact of carbon fraction in the slurry and applied c-rate on the specific capacity. The trends obtained are analyzed by following the behavior of parameters such as number of contacts between electroactive particles and the percentage of electroactive silicon particles. Furthermore, instead of studying the bulk behavior of the slurry, here the focus is given to the slurry/current collector interface in order to illustrate its importance. Hereby, it is demonstrated how this modeling tool can lead to deeper understanding and optimization of electroactive particle suspensions in redox flow batteries.

A Review of Multiscale Computational Methods in Polymeric Materials

Polymeric materials display distinguished characteristics which stem from the interplay of phenomena at various length and time scales. Further development of polymer systems critically relies on a comprehensive understanding of the fundamentals of their hierarchical structure and behaviors. As such, the inherent multiscale nature of polymer systems is only reflected by a multiscale analysis which accounts for all important mechanisms. Since multiscale modelling is a rapidly growing multidisciplinary field, the emerging possibilities and challenges can be of a truly diverse nature. The present review attempts to provide a rather comprehensive overview of the recent developments in the field of multiscale modelling and simulation of polymeric materials. In order to understand the characteristics of the building blocks of multiscale methods, first a brief review of some significant computational methods at individual length and time scales is provided. These methods cover quantum mechanical scale, atomistic domain (Monte Carlo and molecular dynamics), mesoscopic scale (Brownian dynamics, dissipative particle dynamics, and lattice Boltzmann method), and finally macroscopic realm (finite element and volume methods). Afterwards, different prescriptions to envelope these methods in a multiscale strategy are discussed in details. Sequential, concurrent, and adaptive resolution schemes are presented along with the latest updates and ongoing challenges in research. In sequential methods, various systematic coarse-graining and backmapping approaches are addressed. For the concurrent strategy, we aimed to introduce the fundamentals and significant methods including the handshaking concept, energy-based, and force-based coupling approaches. Although such methods are very popular in metals and carbon nanomaterials, their use in polymeric materials is still limited. We have illustrated their applications in polymer science by several examples hoping for raising attention towards the existing possibilities. The relatively new adaptive resolution schemes are then covered including their advantages and shortcomings. Finally, some novel ideas in order to extend the reaches of atomistic techniques are reviewed. We conclude the review by outlining the existing challenges and possibilities for future research.