Description
- Abstract:
- It is well known that diffusion induced stresses are responsible for capacity fading of electrodes in lithium-ion batteries. Here, we develop an atomistic-based continuum model for atomic diffusion within solid electrodes, accounting for the effect of the interplay between stress field, diffusivity and chemical potential, effect of the solution binding energy, and the maximum attainable stoichiometry. Our model is then validated using molecular dynamics simulations of hydrogen diffusion in nickel. The model is shown to give predictions in excellent agreement with atomistic simulations. It is shown that the stress-diffusivity coupling introduced here could give rise to a surface locking instability under constant charging flux. This instability, which happens only when the product of the electrode’s characteristic size and charging current exceeds a critical value, replaces the typical diffusion process and causes the inserted atoms to accumulate within a boundary layer near the surface without allowing them to get inside the electrode. <br/> We will then particularly focus on the mechanical failure in silicon (Si) thin film electrodes on metallic substrates. It is a common observation that emergence of a variety of mechanical failure modes is responsible for capacity loss in such electrodes after only a few cycles. Recently, it has been proposed that patterning could provide a way to improve the mechanical stability of thin film electrodes. In this study, we present a theoretical study of fracture, interfacial delamination and fatigue in patterned thin film electrodes, with reference to the available experimental observations. It is shown that sliding at the interface between the Si thin film and underlying metallic substrate could explain why fracture spacing in continuous thin films is orders of magnitude larger than the film thickness. Based on the idea of interfacial sliding, it is also explained why interfacial delamination of Si island electrodes manifests a size effect about the size of the fracture spacing in a continuous film. Moreover, it is shown that variations in yield stress and/or interfacial shear resistance during lithium cycling could potentially activate a ratcheting failure mode in Si islands, leading to incremental accumulation of deformation. <br/>
- Notes:
- Thesis (Ph.D. -- Brown University (2013)
Access Conditions
- Rights
- In Copyright
- Restrictions on Use
- Collection is open for research.
Citation
Haft Baradaran, Hamed,
"Modeling Diffusion, Deformation and Fracture in Thin Film Electrodes"
(2013).
Mechanics of Solids Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0QN653T
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Collection:
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Mechanics of Solids Theses and Dissertations
Theses and Dissertations for the Mechanics of Solids department....