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Superionic Conduction of Next-Generation Mobile Ions in Solids Enabled by Coordinating Ligands


Iton, Zachery William Benjamin (2024) Superionic Conduction of Next-Generation Mobile Ions in Solids Enabled by Coordinating Ligands. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/fwyd-2w86.


Advancements in battery technologies are a critical step towards meeting the growing demand for sustainable energy storage solutions. The development of next-generation battery technologies using "beyond-Li" ions, like Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, and Al³⁺, could potentially offer improved performance, safety, and cost-effectiveness over traditional lithium-ion systems. However, the realization of next-generation battery technology based on "beyond-Li" mobile ions is limited, in part, due to a lack of understanding of solid state conduction of next-generation ions, which governs ion transport in electrodes, interphases, and solid electrolytes. “Beyond-Li” ions tend to have relatively low mobility in solids due to: (1) the larger ionic radii (Na⁺, K⁺, Ca²⁺), which limit the accessible migration pathways, or (2) higher charge densities (Mg²⁺, Zn²⁺ Al³⁺), which results in strong electrostatic interactions within the solid.

This work discusses several structure-property relationships and structural modifications that are hypothesized to lead to facile conduction of next-generation working ions. A notable discovery is the superionic conductivity of ZnPS3 after exposure to humid environments. Water is introduced into the grain boundaries, thereby enabling Zn²⁺ ions from the material to migrate and conduct freely in the network of adsorbed water. The introduction of water leads to potential H⁺, therefore a methodology for decoupling the contributions of Zn²⁺ and H⁺ in mixed ionic conducting solids using ion-selective EIS, transference number measurements, and deposition experiments is established.

Further extending this approach, superionic conductivity of other next-generation ions in electronically-insulating inorganic solids is achieved by leveraging the established ion exchange/intercalation mechanism of MPS3 (M = Cd, Mn) materials. The mobile cations that are introduced are coordinated with H2O ligands which simultaneously increase the size of the bottlenecks within the migration pathway and screen the charge-dense ions resulting in high mobilities. Potential applications can be extended to water-incompatible systems by replacing the water ligands with aprotic molecules.

These insights contribute significantly to the understanding and development of next-generation battery technologies, representing an important step toward the development of more sustainable and efficient energy storage solutions.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:solid state ionic conduction; multivalent ions; solid state electrolytes; water-assisted ionic conduction; ligand-assisted ionic conduction; Modular frameworks; superionic; zinc batteries; next-generation batteries
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • See, Kimberly A.
Thesis Committee:
  • Faber, Katherine T. (chair)
  • Atwater, Harry Albert
  • Greer, Julia R.
  • See, Kimberly
Defense Date:8 May 2024
Funding AgencyGrant Number
Beckman Young Investigator AwardUNSPECIFIED
Packard FoundationUNSPECIFIED
Alfred P. Sloan FoundationFellowship
Camille and Henry Dreyfus FoundationUNSPECIFIED
Record Number:CaltechTHESIS:05302024-015407649
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for chapter 2 adapted for chapter 4 paper adapted for chapter 5
Iton, Zachery William Benjamin
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16440
Deposited By: Zachery Iton
Deposited On:31 May 2024 23:29
Last Modified:12 Jun 2024 21:50

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