Abstract
Classical molecular dynamics simulations with polarizable force field have been performed for solid electrolytes based on poly(ethylene oxide) or pentaglyme and alkali metal iodides MeI (Me = Li, Na, K, Rb and Cs) in order to study salt precipitation process. Monitoring of structural changes has shown that the tendency for ion aggregation increases with the radius of the cation and with increasing temperature, in qualitative agreement with available experimental data. Analysis of estimated ion diffusivities and conductivities of studied electrolytes has revealed that simulations overestimate correlation between movements of oppositely charged ions compared to experiment. Possible improvements in simulation setup and directions for future more detailed studies have been proposed.
Highlights
Solid polymer electrolytes (SPEs) have been the subject of intense research
Classical molecular dynamics simulations with polarizable force field have been performed for solid electrolytes based on poly(ethylene oxide) or pentaglyme and alkali metal iodides MeI (Me = Li, Na, K, Rb and Cs) in order to study salt precipitation process
Test molecular dynamics (MD) runs for LiI solution in pentaglyme indicated that large polarizability of I– ion (7.25 Å3) causes the “polarizability catastrophe” leading to increasing induced dipole moments and nonphysically short Li-I distances. These results show that polarizability of the anion is one of key parameters of the force field controlling the dynamics of ion aggregation
Summary
Solid polymer electrolytes (SPEs) have been the subject of intense research Interest in these systems is motivated by their properties and prospective applications in batteries, solar cells and electrochemical devices. From methodological point of view, it is important to test theoretical approaches on systems exhibiting less common properties In such a way methodology used in simulations may be validated and information on its performance at extreme conditions provides better insight into the physics of observed processes making possible improvements of simulation protocols or parameterization with prospective benefits for routine modeling of common systems. In this work we want to assess the performance of a polarizable force field for PEO-based electrolytes on model systems of the kind investigated experimentally in [2], in order to check whether classical MD simulations can describe properly ion association process and its dependence on temperature and electrolyte composition. Based on quantum chemical calculations, parameterization of the force field will be adjusted and results of simulations will be analyzed to track the ion aggregation and estimate diffusivity and conductivity of electrolyte
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