Unravelling Patterns and Interactions in Ionic Fluids

Particle and surface interactions in electrolytes underpin the behavior of many systems in soft and biological matter, electrochemical devices, and materials science. Of particular recent interest are electrolytes at very high concentration, and the extreme case of ionic liquids: solvent-free salts in the liquid state under ambient conditions. Recent work has illuminated several important gaps in our understanding of interactions in concentrated electrolytes, together presenting fascinating puzzles for those interested in the nature of the (ionic) liquid state.

In my laboratory we perform high-resolution measurements of the optical and mechanical properties of thin liquid films using a Surface Force Balance (SFB). In this seminar I will present some examples of recent experiments with highly concentrated electrolytes and ionic liquids. Measurements of structure at the liquid-solid interface indicates intricate alternating cation/anion patterns. We measure the effect of electrostatic screening of the surface charge, and find an anomalously long lengthscale for screening in the highly concentrated electrolytes. Most recently, dynamic measurements with applied electric fields allow us to explore in detail the charging process at electrode-electrolyte interfaces giving new insights into the time- and length-scales under various conditions.