Materials Science and Engineering Location: North Oval Room-Rotunda
Add to Calendar 2022-08-15T09:00:00 2022-08-15T09:00:00 America/New_York Doctoral Dissertation Proposal: Ian Brummel Investigating the Origin of Grain Boundary Ionic Resistance in Perovskite-Type Lithium Ion Conductors   Committee: Dr. Elizabeth Opila (Chair) Dr. Jon Ihlefeld Dr. Robert Kelly Dr. Gary Koenig Dr. Erik Spoerke   Abstract North Oval Room-Rotunda

Investigating the Origin of Grain Boundary Ionic Resistance in Perovskite-Type Lithium Ion Conductors

 

Committee:

Dr. Elizabeth Opila (Chair)

Dr. Jon Ihlefeld

Dr. Robert Kelly

Dr. Gary Koenig

Dr. Erik Spoerke

 

Abstract

High performance batteries are of great interest due to the increased need for storage and delivery of renewable energy to the grid as well as the increasing level of electrification of the transport sector. The current state-of-the-art technology for energy storage in these applications is the lithium ion battery. Lithium ion batteries are widely deployed due to their high energy and power density as well as stability of capacity over many charging cycles. The majority of lithium ion batteries make use of a polymer separator to prevent short circuiting between the anode and cathode. This separator is impregnated with an organic, liquid electrolyte that facilitates the lithium transfer in the battery. While this combination of separator and electrolyte provides a good combination of low expense, ease of manufacture, and performance, it suffers in several key areas including safety of the battery and limited electrochemical window. The organic liquids use in current lithium ion battery construction tend to react violently to catastrophic damage to the battery cell including mechanical damage and large current overdraws. Both of these situations can lead to fires that have taken lives as well as damaged property. Further, liquid electrolytes have a limited electrochemical window that prevents their integration with higher energy electrode materials, including lithium metal. Solid state electrolytes offer a solution to the safety issue because they are not reactive in air and show good thermal stability.

 

Multiple solid state electrolyte candidate materials have been identified by the research community that display high values of bulk ion conductivity, however the effective ion conductivity of these materials in polycrystalline form is commonly reduced by several orders of magnitude due to the high impedance of grain boundaries. Traditional study of these materials has identified that the grain boundary conductivity is significantly lower than that of the bulk due to several mechanisms, but is only capable of measuring an ensemble average of the grain boundary responses in a material. It can be expected that the highly varied structural, electronic, and compositional environments that are generated by different grain misorientations would lead to differing ion conductivity responses across different grain boundaries. This dissertation proposal seeks to identify the specific mechanisms leading to increased grain boundary impedance at the different grain boundaries, using Li3xLa1/3-xTaO3 (LLTaO) as a model lithium ion conductor. Measurements of single grain boundaries will be made possible by employing the epitaxial growth of LLTaO on bicrystalline and polycrystalline SrTiO3 substrates. Preliminary work on the processing of polycrystalline LLTaO and measurements of single grain boundaries will be presented.

 

 

All interested persons are invited to attend.