Multi-Scale Investigation of Thermodiffusion With Implications To Electrochemical Systems

与麦克马斯特大学和NSERC的使命，以促进知识的发现和应用相一致，本研究的目的是调查“热扩散”的基础和应用水平的主题。热扩散或索雷特效应是一种耦合的质量和热量传递现象，其中当包含混合物的域经受热梯度时，混合物的组分倾向于分离到优选的热区中。它是许多科学应用和自然过程的基本原理，即场流分馏装置、同位素分离、生物和生物分子过程、地下储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，因为（i）缺乏电化学系统中Soret效应的适当公式以及（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/相关性激发了重要的研究活动，但仍然缺乏对这种现象的全面和令人满意的理论解释，适用于每种类型的流体混合物。这是由于流体混合物中的组分对温度梯度的响应涉及分子水平上的许多现象，这些现象尚未完全理解。考虑到这些缺点，我们建议研究热扩散的多尺度形式主义，将分子动力学的原则。这将使我们能够考虑宏观尺度的传输过程中的分子机制的影响，从而有助于开发一个准确和全面的热扩散模型。这种多尺度模型随后将被应用于研究热扩散对锂离子（Li离子）电池性能的影响，其中关于在纳米级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。虽然在这项研究中开发的综合热扩散模型将使我们能够改善目前的分离技术在核和生物工业中，该模型的应用，以研究电池的降解机制，将使我们能够设计出上级性能电池。这种高性能电池将在未来的汽车，电力存储，军事，移动站和空间应用中发挥至关重要的作用。

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.