Multi-Scale Investigation of Thermodiffusion With Implications To Electrochemical Systems

与麦克马斯特大学和NSERC促进知识发现和应用的使命一致，这项研究的目的是在基础和应用层面上调查‘热扩散’这一主题。热扩散或Soret效应是一种耦合的传质和传热现象，当包含混合物的区域受到热梯度影响时，混合物的组分倾向于偏析到优先的热区。它是许多科学应用和自然过程的基本原理，这些自然过程是现场流动分馏装置、同位素分离、生物和生物分子过程、地下储油层中原油组分的分层和食品的冷冻过程。除此之外，其他研究人员最近的研究也表明，电化学系统中的索雷特效应可以在电池的整体性能中发挥作用。然而，目前对此知之甚少，这是因为(I)在电化学系统中缺乏适当的Soret效应的公式，以及(Ii)我们对电池老化过程的不完全理解。虽然热扩散的广泛应用/相关性已经激发了大量的研究活动，但对这一现象的全面和令人满意的理论解释仍然缺乏，适用于每种类型的流体混合物。这是因为流体混合物中各组分对温度梯度的反应涉及分子水平上的许多现象，这些现象还没有完全被理解。考虑到这些缺点，我们建议用结合了分子动力学原理的多尺度形式来研究热扩散。这将使我们能够考虑分子机制对宏观输运过程的影响，从而有助于开发准确和全面的热扩散模型。这个多尺度模型随后将被应用于研究热扩散对锂离子(Li-ion)电池性能的影响，其中对纳米尺度上发生的机制对表征电池性能和退化的整体大尺度参数的影响知之甚少。虽然本研究将开发的综合热扩散模型将使我们能够改进目前核工业和生物工业中的分离技术，但应用该模型来研究电池中的降解机理将使我们能够设计出性能更好的电池。这种高性能电池将在未来的汽车、储能、军事、移动站和空间应用中发挥重要作用。

Consistent with McMaster University's and NSERC's missions to foster the discovery and application of knowledge, the aim of this research is to investigate the subject of ‘Thermodiffusion’ at the fundamental as well as applied level. Thermodiffusion, or the Soret-effect, is a coupled mass and heat transfer phenomenon in which the components of a mixture tend to segregate into preferred thermal zones when the domain containing the mixture is subjected to a thermal gradient. It is the underlying principle in many scientific applications and natural processes, namely, field flow fractionation devices, isotope separation, biological and biomolecular processes, stratification of crude oil components in underground reservoirs and freezing processes of foods. Apart from these, recent studies by other researchers also suggest that the Soret-effect in electrochemical systems can play a role in the overall performance of a battery. However, at present there is very little known about this because of (i) the lack of appropriate formulations for the Soret-effect in electrochemical systems as well as (ii) our incomplete understanding of the ageing process of a battery. While the wide spectrum of applications/relevance of thermodiffusion has spurred significant research activity, a comprehensive and satisfactory theoretical explanation of this phenomenon, applicable for every type of fluid mixture is still lacking. This is due to the fact that the response of the constituents in a fluid mixture to a temperature gradient involves a multitude of phenomena at the molecular level that is not completely understood. Keeping these shortcomings in mind, we propose to study thermodiffusion in a multi-scale formalism incorporating the principles of molecular dynamics. This will enable us to account for the effects of the molecular mechanisms on the macroscale transport process, thereby aiding in developing an accurate and comprehensive thermodiffusion model. This multi-scale model will subsequently be applied to study the effects of thermodiffusion on the performance of a Lithium-ion (Li-ion) battery, where much less is known about the impact of mechanisms occurring at the nanoscale on the overall large scale parameters characterizing the battery performance and degradation. While the comprehensive thermodiffusion model to be developed in this research will enable us to improve the current separation technologies in the nuclear and biological industry, the application of the model to study the degradation mechanisms in a battery will enable us to design superior performing batteries. Such high performance batteries will play a vital role in future automobiles, power storage, military, mobile-station, and space applications.