Puzzles with Ionic Liquids and Concentrated Electrolytes

Highly concentrated electrolytes are important in nature and in technology; most recently their importance has been highlighted in the design of next-generation electrolytes for energy storage devices. An extreme case of concentrated electrolyte is pure ionic liquid: solvent-free salt in the liquid state under ambient conditions. Recent focus on the physical properties of ionic liquids and concentrated electrolytes has illuminated several important gaps in our understanding, together presenting fascinating puzzles for those interested in the nature of the (ionic) liquid state.  In my laboratory we perform high-resolution force measurements between uniform charged surfaces across liquid using a Surface Force Balance (SFB). I will present some examples of recent experiments with highly concentrated electrolytes, demonstrating an anomalously long electrostatic screening length which, curiously, increases with increasing volume fraction of ions [1,2].  
 
1. A. Smith, A. Lee, and S. Perkin, J. Phys. Chem. Lett. 7, 2157 (2016).
2. A. Smith, A. Lee, and S. Perkin. Phys. Rev. Lett. 118, 096002 (2017).
3. Lee, A., Perez-Martinez, C., Smith, A., Perkin, S. Phys. Rev. Lett. 119, 026002 (2017).

Bio: Susan Perkin is Associate Professor of Physical Chemistry and Fellow of Trinity College, University of Oxford. She received her DPhil in 2006 studying with Jacob Klein. She was Junior Research Fellow at Merton College, Oxford from 2005-2008. She moved to UCL in London (2007-2012, as RCUK Fellow then Lecturer) where she set up a laboratory and research group to work on ionic liquids and liquid interfaces. In 2012 she was appointed to the Faculty of Chemistry at Oxford. Current interests include electrostatics in concentrated electrolytes and ionic liquids, molecular mechanisms of friction and lubrication, field effects on confined liquids, graphene surface forces, and controlling surface properties through the design of switchable thin films. In the past few years Susan has been awarded a Starting Grant from the ERC, the Harrison-Meldola Memorial Prize from the Royal Society of Chemistry, and a Philip Leverhulme Prize from The Leverhulme Trust.