Citation
Stradley, Steven Hartzel (2025) Materials and Interfaces to Enable Reversible Mg Electrochemistry for Energy Storage Applications. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/vs2j-ep54. https://resolver.caltech.edu/CaltechTHESIS:05152025-202058082
Abstract
Climate change drives the need for a dramatically increased deployment of electric vehicles and intermittent renewable energy sources. Each of these depends intimately on batteries for range and reliability. Although Li-ion batteries are the current industry standard for electrochemical energy storage, they are based on scarce and unevenly distributed resources. It is thus crucial to develop rechargeable battery chemistries based on more energy dense and resource equitable materials. Orders of magnitude more abundant and energy dense than Li, Mg is an attractive alternative to Li for energy storage. Despite its many attractive properties, deployment of Mg-based chemistries is hindered by a lack of cathode, anode, and electrolyte materials which support Mg electrochemistry and are mutually compatible. This thesis endeavors to deploy new materials to sustain reversible Mg electrochemistry and to understand how certain material properties impact electrochemical performance. First, we investigate new cathode materials based on Earth-abundant transition metal chlorides. These cathodes cycle somewhat reversibly but are prone to rapid capacity fade due to active material dissolution and shuttle. We identify electrolyte modification as a means to combat this fade. Next, we characterize halide-free Mg electrolytes based on weakly coordinating Si-centered anions. These electrolytes display impressively high oxidative stabilities but also relatively high reductive overpotentials and a fatal vulnerability to passivation by H₂O. We then consider a class of electrolytes based on B-centered anions with aryl ligands. These systems show exceptionally low reductive overpotentials among halide-free Mg electrolytes. We increase the bulk of the anion and correspondingly observe a slight increase in the reductive overpotential and an enhancement in rate performance. Though this class of compounds shows a low oxidative stability, the structure-property relationships gleaned from it may prove useful in future electrolyte studies. Finally, we deploy Al as an Earth-abundant, high capacity alloying anode for Mg-based batteries. Though the native kinetics for Mg-Al alloying prove too sluggish for practical systems, we use Bi to enhance the alloying kinetics of Al by two orders of magnitude. Though alloying capacity is limited by a large particle size, we present a viable method for enhancing Al alloying kinetics to relevant rates, thereby unlocking a highly desirable material for future studies. Taken together, this work expands the scope of cathode, electrolyte, and anode materials which support reversible Mg electrochemistry. Though imperfect, the lessons we learn from them may inform future design decisions to enable reversible Mg-based batteries.
| Item Type: | Thesis (Dissertation (Ph.D.)) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Subject Keywords: | Battery, magnesium electrolyte, magnesium anode, alloy anode | ||||||||
| Degree Grantor: | California Institute of Technology | ||||||||
| Division: | Chemistry and Chemical Engineering | ||||||||
| Major Option: | Chemical Engineering | ||||||||
| Thesis Availability: | Not set | ||||||||
| Research Advisor(s): |
| ||||||||
| Thesis Committee: |
| ||||||||
| Defense Date: | 23 January 2025 | ||||||||
| Funders: |
| ||||||||
| Record Number: | CaltechTHESIS:05152025-202058082 | ||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechTHESIS:05152025-202058082 | ||||||||
| DOI: | 10.7907/vs2j-ep54 | ||||||||
| Related URLs: |
| ||||||||
| ORCID: |
| ||||||||
| Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||
| ID Code: | 17233 | ||||||||
| Collection: | CaltechTHESIS | ||||||||
| Deposited By: | Steven Stradley | ||||||||
| Deposited On: | 23 May 2025 19:55 | ||||||||
| Last Modified: | 23 May 2025 19:55 |
Full text not available from this repository.
Repository Staff Only: item control page
