Ion conduction by the picosecond : optical probes and correlations
Abstract/Contents
- Abstract
- Ionic conductivity is key to electrochemical energy storage in rechargeable batteries, and remains a vital enabler of clean energy. Macroscopically, ion conduction is a random temperature-activated process consisting of rare and incoherent discrete events called hops. In every such event, a mobile ion physically jumps, i.e. undergoes translation, between distinct crystallographic sites in a host lattice. The centrality of fast ion conductors to pressing societal needs demands a mechanistic understanding of ion conduction starting at the timescales of single hops, and including contributions of phonon structure, anharmonicity, and collective phenomena. I have used picosecond-timescale terahertz pump-probe experiments and large-scale molecular dynamics simulations to characterize ionic hopping in a model homologous family of historic fast solid-state ionic conductors, the beta-aluminas, M_1.2 Al_11 O_17.1, with mobile ions M = Na+, K+, Ag+. I have quantified spatio-temporal correlations between hopping events in beta-aluminas using a statistical social-network approach. In all beta-aluminas, each hop of an ion acts as a perturbation to its neighboring mobile ions, and furthermore influences follow-on hops. These correlations extend beyond nearest-neighbor interactions and appear mediated by specific vibrational couplings. Using single-cycle terahertz optical pulses, I have resonantly pumped the hopping attempt frequencies of mobile ions in beta-aluminas. The transient birefringence of the materials following a terahertz pump elucidates the picosecond-timescale dynamics of mobile ions. The statistics of hopping events derived from molecular dynamics explain the unusual liquid-like relaxation in beta-aluminas in addition to the expected vibrational responses. I furthermore experimentally observe signatures of correlated hopping events. In contrast to periodic-perturbation experiments, or to non-resonant pumping, it is the transition state, i.e. an ion caught mid-hop, that is the most sensitive to strong-field terahertz pulses and gives rise to the liquid-like response. To the best of my knowledge, these are the first pump-probe studies of ionic transport in electronically insulating materials, drawing parallels to studies of electronic conduction in photovoltaics. Based on my experimental and computational methods, I discuss the role of local vibrational dynamics and correlated transport in mediating fast ionic conduction and determining the overall activation energy
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Poletayev, Andrey D |
|---|---|
| Degree supervisor | Chueh, William |
| Thesis advisor | Chueh, William |
| Thesis advisor | Devereaux, Thomas Peter, 1964- |
| Thesis advisor | Lindenberg, Aaron Michael |
| Degree committee member | Devereaux, Thomas Peter, 1964- |
| Degree committee member | Lindenberg, Aaron Michael |
| Associated with | Stanford University, Department of Materials Science and Engineering. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Andrey D. Poletayev |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering |
| Thesis | Thesis Ph.D. Stanford University 2020 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Andrey D Poletayev
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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