Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries

<p>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...

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Main Author: Tozier, Dylan Douglas
Format: Others
Published: 2018
Online Access:https://thesis.library.caltech.edu/11037/15/Dylan%20Tozier%20Thesis%2020180607.pdf
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. https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228 <https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228>
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spelling ndltd-CALTECH-oai-thesis.library.caltech.edu-110372019-10-05T03:05:25Z Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries Tozier, Dylan Douglas <p>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.</p> <p>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.</p> <p>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.</p> <p>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.</p> 2018 Thesis NonPeerReviewed application/pdf https://thesis.library.caltech.edu/11037/15/Dylan%20Tozier%20Thesis%2020180607.pdf https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228 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. https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228 <https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228> https://thesis.library.caltech.edu/11037/
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description <p>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.</p> <p>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.</p> <p>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.</p> <p>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.</p>
author Tozier, Dylan Douglas
spellingShingle Tozier, Dylan Douglas
Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries
author_facet Tozier, Dylan Douglas
author_sort Tozier, Dylan Douglas
title Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries
title_short Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries
title_full Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries
title_fullStr Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries
title_full_unstemmed Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries
title_sort cathode design for high energy molten salt lithium-oxygen batteries
publishDate 2018
url https://thesis.library.caltech.edu/11037/15/Dylan%20Tozier%20Thesis%2020180607.pdf
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. https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228 <https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228>
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