Practical electrolytes require the simultaneous optimization of diverse properties. Unfortunately, the link between ion structure, molecular-level interactions (solution structure) and measureable properties remains poorly understood for ionic liquid-based electrolytes. To address this challenge, a wide range of ionic liquids with the bis(trifluoromethanesulfonyl)imide anion and variable cations have been scrutinized as model systems. Variables include the cation head group (i.e., N-alkyl-N-methylpyrrolidinium, -piperidinium, etc.), cation alkyl chain length, inclusion of an ether oxygen in the cation ring (i.e., N-alkyl-N-methylmorpholinium) and/or alkyl chain, etc. The properties (density, viscosity, conductivity) of the neat ionic liquids and their mixtures with LiTFSI have been correlated with what is known from solid-state structures and a spectroscopic analysis of the interactions. Such a deconvolution provides practical guidelines for tailoring the selection of ions in an ionic liquid-based electrolyte for specific applications.

Linking ion structure with ionic liquid-based electrolyte transport properties

243rd National Meeting (2012)

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