Multi-Scale Investigation of Thermodiffusion With Implications To Electrochemical Systems

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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.