Numerical modeling of energy storage materials
Abstract/Contents
- Abstract
- Lithium-ion batteries (LIBs) are important energy storage devices with applications ranging from portable electronics to electric vehicles. Their widespread applications persistently drive the advancement of LIB technologies. To improve energy density of LIBs, one approach is to use novel electrode materials, such as Silicon (Si), Germanium (Ge), Tin (Sn), or Sulfur (S), which have been investigated both experimentally and numerically. This work mainly focuses on the numerical modeling of Si anodes to understand the important role of mechanics in electrochemical systems. Si is considered to be a promising anode material for LIBs, characterized by a theoretical specific capacity as high as 4200 mAh/g, in comparison to 372 mAh/g for graphite, which currently is the most common commercial anode material. The charging/discharging process of Si anodes is highly complex, involving mass diffusion, electrochemical reaction, phase transformation, and large mechanical deformation (~300% volume change). The large volume change can cause fracture of both Si anodes and the solid electrolyte interphase (SEI) layer, which is a thin layer formed on the anode to prevent unwanted side reactions between the anode and the electrolyte, resulting in poor cyclic performance of Si-based LIBs. To better understand the diffusion and mechanical behavior of Si anodes, sophisticated computational models are needed to describe diffusion-induced elastoplastic deformation and fracture of Si anodes. In this work, a variational based electro-chemo-mechanical coupled computational framework is formulated to study diffusion-induced mechanical deformation of Si anodes, where a diffusive phase field fracture model is used to describe the crack formation and propagation. To account for the underlying phase transformation of Si anodes (crystalline Si to amorphous LixSi and amorphous Si to amorphous LixSi) during the initial charging process, a physically motivated reaction-controlled diffusion (RCD) model is proposed. The RCD model is incorporated into the newly proposed coupled variational framework to model diffusion-induced anisotropic deformation for crystalline Si. With this fully coupled computational framework, we investigate the stress state, Lithium (Li) concentration distribution, and phase boundary evolution during the lithiation process of Si anodes. We further investigate how electrode geometry and geometrical constraints affect the fracture behavior of Si anodes. This work can be extended to study the formation and fracture of the SEI layer on Si anodes and provides necessary computational tools for optimizing and designing high energy density Si anodes for LIBs with outstanding cyclic performance in the future.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Zhang, Xiaoxuan |
|---|---|
| Associated with | Stanford University, Civil & Environmental Engineering Department. |
| Primary advisor | Linder, Christian, 1949- |
| Thesis advisor | Linder, Christian, 1949- |
| Thesis advisor | Borja, Ronaldo Israel |
| Thesis advisor | Cai, Wei, 1977- |
| Advisor | Borja, Ronaldo Israel |
| Advisor | Cai, Wei, 1977- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Xiaoxuan Zhang. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by Xiaoxuan Zhang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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