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Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries

Citation

Tozier, Dylan Douglas (2018) Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/TG0K-8776. http://resolver.caltech.edu/CaltechTHESIS:06072018-140534228

Abstract

State of the art commercial lithium ion batteries use cathodes such as lithium cobalt oxide which rely on insertion and removal of lithium ions from a host material. However, insertion cathode materials are limited in their capacity, and replacing them with a cathode that employs growth and dissolution of new phases could significantly increase a battery’s energy density. For example, oxygen and sulfur cathodes have been widely researched to this end, with both cases involving the growth of a lithium-rich compound on a current collector/catalyst support.

We begin by describing the effect of using a molten salt electrolyte in a lithium-oxygen battery. In particular, we focus on how the electrochemical performance and discharge product, lithium peroxide, differ from that of a traditional organic electrolyte. In addition, we discuss the enhanced peroxide solubility in a molten salt and its implications for lithium peroxide growth and coulombic efficiency. Finally, we address the cell death of a galvanostatically cycled battery.

We then introduce a similar phase-forming conversion chemistry, whereby a molten nitrate salt serves as both an active material and the electrolyte. Molten nitrate salts were previously studied as an active material in a primary lithium battery where lithium oxide irreversibly forms as nitrate reduces to nitrite. We will describe how the use of a nanoparticle heterogeneous catalyst allows the reversible growth and dissolution of micron-scale lithium oxide crystals in this system.

After introducing these molten salt lithium batteries, we address the effect of cathode geometry on electrochemical performance. In particular, we note that the growth of such large, solid phase species on the surface of the catalyst support imposes new design restrictions when optimizing a cathode for energy density. As a proof of concept, we design and implement an architected electrode with large pore volume and relatively small surface area, comparing it with the more typical geometries of thin films and nanoparticles.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Battery; Lithium-Oxygen; Molten Salt; Structured Electrode
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Greer, Julia R.
Thesis Committee:
  • Fultz, Brent T. (chair)
  • Greer, Julia R.
  • Johnson, William Lewis
  • See, Kimberly
Defense Date:31 May 2018
Record Number:CaltechTHESIS:06072018-140534228
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:06072018-140534228
DOI:10.7907/TG0K-8776
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/jacs.5b11744DOIArticle adapted for Ch. 2
ORCID:
AuthorORCID
Tozier, Dylan Douglas0000-0001-9489-8824
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11037
Collection:CaltechTHESIS
Deposited By: Dylan Tozier
Deposited On:08 Jun 2018 23:59
Last Modified:10 Dec 2018 17:45

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