Molecular Dynamics of Lithium Ion Transport in a Model Solid Electrolyte Interphase

Abstract

Li+ transport within a solid electrolyte interphase (SEI) in lithium ion batteries has challenged molecular dynamics (MD) studies due to limited compositional control of that layer. In recent years, experiments and ab initio simulations have identified dilithium ethylene dicarbonate (Li2EDC) as the dominant component of SEI layers. Here, we adopt a parameterized, non-polarizable MD force field for Li2EDC to study transport characteristics of Li+ in this model SEI layer at moderate temperatures over long times. The observed correlations are consistent with recent MD results using a polarizable force field, suggesting that this non-polarizable model is effective for our purposes of investigating Li+ dynamics. Mean-squared displacements distinguish three distinct Li+ transport regimes in EDC — ballistic, trapping, and diffusive. Compared to liquid ethylene carbonate (EC), the nanosecond trapping times in EDC are significantly longer and naturally decrease at higher temperatures. New materials developed for fast-charging Li-ion batteries should have a smaller trapping region. The analyses implemented in this paper can be used for testing transport of Li+ ion in novel battery materials. Non-Gaussian features of van Hove self -correlation functions for Li+ in EDC, along with the mean-squared displacements, are consistent in describing EDC as a glassy material compared with liquid EC. Vibrational modes of Li+ ion, identified by MD, characterize the trapping and are further validated by electronic structure calculations. Some of this work appeared in an extended abstract and has been reproduced with permission from ECS Transactions, 77, 1155–1162 (2017). Copyright 2017, Electrochemical Society, INC.

Towards Understanding the Different Influences of Grain Boundaries on Ion Transport in Sulfide and Oxide Solid Electrolytes

“…The MD simulations are based on established techniques and have been widely used to determine the ion transport properties in a wide variety of Liand Na-ion battery materials. 16,62,[64][65][66][67][68] A new potential model was developed for cubic Na3PS4 (Table S1) using the empirical derivation procedure of the General Utility Lattice Program (GULP). 69 For Na3PO4, we used the proven potential model of Tilocca et al 70 (Table S2) that was developed for MD calculations of phosphosilicate glasses, augmented here with a Na-Na interatomic potential from Harding.…”

Towards autonomous high-throughput multiscale modelling of battery interfaces

“…As discussed in the previous sections, Ab initio molecular dynamics (AIMD) and reactive force-field molecular dynamics are two of the most used alternatives to study the composition and decomposition reactions related to the SEI. 101,[136][137][138][139] Over larger spatial scales, classical molecular dynamics is often the preferred method to characterize the mechanical properties along with the transport of ions in the SEI layer.…”

Range, Endurance, and Optimal Speed Estimates for Multicopters

“…A TTC model only shows improved precision in cases where the battery dynamics need to be accurately captured at very short timescales [32]. Much more elaborate battery models based on molecular dynamics simulations exist [33], [34] but are unsuited for the task at hand because of being highly specific to exactly one battery type.…”