The complex solid electrolyte interface (SEI) in rechargeable Li ion batteries, which forms as a result of electrolytic reactions, acts as a passivating layer to protect the electrode and greatly impacts battery performance. Atomistic level simulations can provide critical understanding of the mechanism of Li+ ion transport through the SEI. While ideally one would prefer to use ab initio MD simulations, the long time and length scales associated with this system make this computationally intractable.  The force-matching method, as a form of coarse-graining, allows one to bridge the gap between computationally expensive ab initio methods and simple force-fields. The algorithm involves parameterizing a simple force field to match reference forces from ab initio MD simulations, thereby generating ab initio quality data using a computationally inexpensive model. Here I show how to implement the method to develop a simple yet accurate force-field for electrolytes and ions in electrolytes, for example LiPF6 in ethylene carbonate. Structural and dynamical properties of the Li+ ion have also been determined from MD simulations of both the bulk electrolyte as well as in an electrochemical cell. Other candidates for rechargeable batteries like salts of Mg2+ in acetonitrile solvent are also being explored.

Systematic development of simple but accurate force-fields for energy storage  material electrolytes

244th National Meeting (2012)

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