学术报告：Molten salts: Predicting physical and electrochemical properties from first-principles等
报告题目：1. Molten salts: Predicting physical and electrochemical properties from first-principles;
2. Understanding the charging mechanism of supercapacitors from molecular dynamics simulations.
报 告 人：Mathieu Salanne（Pierre and Marie Curie university，PECSA Laboratory）
报告时间：2013年3月27（星期三）日上午9：30
报告地点：嘉定园区学术活动中心一楼多功能厅
报告简介：
1. The framework of our study is the potential use of molten salts in the nuclear industry of the future. Interaction potentials were developed for molten salts including cations with a wide-range of valences. A prerequisite of our work was to develop compatible potentials, so that it is possible to perform simulations in which all these elements are present. The procedure was validated on the experimentally well-characterized LiF-BeF2 mixtures by comparing our calculations results to spectroscopic (X-ray diffraction, Raman and infra-red spectroscopy) and transport (electrical conductivities and viscosities) properties. The next step consists in adopting a predictive strategy of physico-chemical quantities that hitherto remain unknown despite of their importance in establishing industrial processes involving molten salts. We focus on the transports of both matter and heat in these media, which appear to be strongly correlated with the structural properties of the ions, on both short and intermediate length scales. Recently we also demonstrated the ability to determine activity coefficients ratios of heavy cations in molten salt solvents, by estimating this quantity for a series of trivalent ions in molten LiCl-KCl eutectic. The central issue consists in predicting differences between free energies of solvation of the different cations and activity coefficients were shown to vary systematically with cation size for this set of trivalent cations.
2. A major challenge in moving towards sustainable and renewable energy sources is to develop lightweight and low-cost storage systems with the capability of leveling the cyclic nature of these sources to satisfy energy demands. Electrochemical double layer capacitors (supercapacitors) store energy at the electrolyte/electrode interface through reversible ion adsorption leading to higher charge/discharge rates and better cyclability but lower energy density compared to batteries. Nevertheless, the recent demonstration that ions from the electrolyte could enter sub-nanometer pores increasing greatly the capacitance opened the way for valuable improvements of the supercapacitors performances.
Despite the recent experimental and fundamental studies on that subject, the molecular mechanism at the origin of this capacitance enhancement is still not quite clear. We report here molecular dynamics simulations including two key features: the use of realistic electrode structures comparable with carbide-derived carbons and the polarization of the electrode atoms by the electrolyte. This original design of an electrochemical cell allows us to recover capacitance values in quantitative agreement with experiment and to gain knowledge about the local structure of the ionic liquid inside the pores (local ionic densities, local coordination numbers). Then, from the comparison between planar (graphite) and porous electrodes, we propose a new mechanism explaining the capacitance enhancement in nanoporous carbons.
报告人简介：
Mathieu Salanne博士在法国Marie Curie and Pierre university任教，曾经在MIT和法国Chimie Paristech接受过核工程方面训练。他于2006年获得博士学位，主要从事高温熔融盐的分子模拟；2007年在法国Institut de Physique Nucléaire做博士后，题目是: Electrochemical study of the grouped extraction of lanthanides in the molten salt LiF-ThF4。Mathieu Salanne发表了43篇学术文章和作了13次国际会议报告，期刊包括Nature Materials, J. Phys. Chem. B & C, Phys. Rev. Lett., J. Chem. Phys.等。2007年，Mathieu Salanne获得了法国La Recherche杂志颁发的奖项，以表彰他为未来核工业做出了优秀的分子模拟研究工作。2012年，Mathieu Salanne在Marie Curie and Pierre university获得了Habilitation degree。
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