Abstract

Although the past twenty years have seen dramatic advancement in lithium-ion batteries (LIBs), these batteries are nearing their theoretical limit. Next generation energy storage technologies must therefore be developed to meet the ever-increasing demands for batteries with higher capacity, longer cycle lifetime, and increased safety. All-solid-state lithium battery (ASSLIB) technology is one of the promising candidates. It is equipped with a solid-state electrolyte (SSE) replacing the flammable organic liquid electrolyte used in current LIBs. The SSE's high modulus is expected to prevent lithium dendrites and enables the use of a lithium metal anode to contribute to its high capacity without creating safety concerns. However, many cases are reported where lithium penetrates the SSE, causing a short circuit that leads to premature failures of the battery. The fundamental mechanism of this process is still under debate. This work seeks to understand the complex electrochemomechanics at the interface between the SSE and lithium metal during the lithium plating and penetration process. To achieve this goal, a unique in situ transmission electron microscopy (TEM) technique was developed to evaluate the mechanical stress imposed at the lithium metal and SSE interface. The method was successfully used to directly observe the penetration of lithium in an SSE from a nano-scale defect at the surface, and it quantified the stress evolution in the process. A reduction in the mechanical strength of the SSE when altering the electrochemical charge/discharge bias condition was revealed. A first principles atomistic simulation was performed to confirm that disorder in the crystal structure of the SSE, both in lithium deficient and excess states, contributes to reduced mechanical properties. The results of this work suggest the importance of minimizing defects at the surface and grain boundaries to improve the stability of the SSE. Interfaces and boundaries can be bottlenecks for lithium diffusion, creating a concentration gradient. This can reduce the mechanical stabilities of the SSE, accelerating lithium penetration and degradation in ASSLIBs. The insights obtained in this study provide useful information towards understanding the dendrite growth mechanism and designing the necessary materials and structures to solve this issue, thus contributing to the advancement of energy storage technologies.

Notes

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Graduation Date

2022

Semester

Spring

Advisor

Kushima, Akihiro

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Materials Science and Engineering

Degree Program

Materials Science and Engineering

Format

application/pdf

Identifier

CFE0008971; DP0026304

URL

https://purls.library.ucf.edu/go/DP0026304

Language

English

Release Date

May 2023

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Campus-only Access)

Restricted to the UCF community until May 2023; it will then be open access.

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