Arman Afshar
(Advisor: Prof.  Claudio Di Leo]

will defend  a doctoral thesis entitled,

Aspects of Continuum Chemo-Mechanics Phenomena in Solids: Applications to Energy Storage Materials.

on  Tuesday, May 4 at 12:00 p.m.

Bluejeans Link: https://bluejeans.com/5626917401
 

Abstract
It has been proven that mechanics plays a non-negligible role in the multiphysics design and analysis of energy storage devices. Capturing this coupling through theoretical and computational modeling is thus critical for improved design of next generation batteries. In this thesis we present novel chemo-mechanically coupled models for future energy storage devices. The work is divided in two parts, starting with a computational effort for simulation of novel nano-architected Li-ion batteries where 3D lattice based electrode structure are shown to be chemo-mechanically superior to conventional electrodes. A fully coupled computational model is developed to solve the diffusion-deformation problem, accounting for finite inelastic deformation and interaction between buckling and plasticity. Second, we turn our attention to the problem of reaction-diffusion-deformation which has applications in solid state electrolytes and conversion type electrodes. Towards modeling the reaction-diffusion-deformation process in solids, we present a thermodynamically consistent finite strain theory for a class of problems in solids mechanics that involve transport of species into a host material, followed by structural phase changes associated with reaction of the species with the host, deformation and stress. The theory distinguishes between diffusion-limited and reaction-limited chemistry, resolving the issue of how a sharp reaction front can be developed in either case. Equally significant in the theory are mechanical and deformation aspects resulting from the diffusion-reaction phenomenon, and how mechanics affects these processes. While the thermodynamically consistent framework is quite general, we apply it to conversion type electrodes as these novel electrochemically active materials are demonstrated to have much higher capacity compared to typical diffusion-based intercalation cathodes. We implement our formulation in a three-dimensional large deformation finite element model, and show how stress affects reaction kinetics in the problem. The numerical simulations also provide an understanding for a rather counter intuitive finding in the chemo-mechanics literature where reaction of conversion type electrodes with larger ions proved to be less detrimental from mechanical perspective. Finally, we extend application of the theory to modeling electrodeposition at interfaces between solid state electrolytes and lithium metal anodes, shedding light on the phenomenon of dendrite propagation in all-solid-state energy storage devices.

Committee

• Prof. Claudio Di Leo – School of Aerospace Engineering (Advisor)
• Prof. Graeme Kennedy – School of Aerospace Engineering
• Prof. Matthew McDowell – School of Mechanical Engineering
• Prof. Julian Rimoli – School of Aerospace Engineering
• Prof. Ting Zhu– School of Mechanical Engineering