While the bulk phase properties of metal-ion electrolytes continue to attract interest, much less is known about the behavior of solvents and salts at the electrode surface.  Molecular modeling provides a unique means of addressing the challenge of obtaining atomic information during battery operation.  Previous work has shown the impact of electrode surface films on the ion solvation and dynamics for a typical electrolyte comprised of LiPF<sub>6</sub> dissolved in ethylene carbonate (EC).  Both the salt association and solvent residence times were altered by proximity to the ionic thin film.  However, the role of the bare electrode in potentially modifying solvation structure has not been extensively explored.  Information is particularly lacking for electrolytes consisting of mixtures of carbonate species.  At the same time, the population of the metal-ion solvation shell has been linked to the surface chemistry observed in energy storage devices.  Mixtures of EC and closely related propylene carbonate (PC) are of particular interest since they represent two extremes: on the one hand EC produces stable surface films while on the other hand PC destroys graphite electrode surfaces.  Upon mixing these carbonates, it is assumed that the chemistry can be tuned by varying the ratio of EC to PC.  However, the bulk composition may be not map directly to the solvation shell of the metal-ion.  Hence, understanding co-solvent preference for metal solvation is critical to assessing the performance of mixed carbonate electrolytes.  We present here results from classical molecular dynamics simulation that probe carbonates at a simple graphite surface and consider changes to co-solvent preference as a result of proximity to the electrode.  These observations are extended to consider the role of bias voltage, EC:PC ratio, and the treatment of electrolyte polarization by charge scaling. <br/>

Role of the electrode surface in Co-solvent preference:  Lithium solvation in EC/PC mixtures

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.