Title:
Understanding Chemomechanical Degradation Mechanisms of Solid-State Lithium-Ion Batteries
Understanding Chemomechanical Degradation Mechanisms of Solid-State Lithium-Ion Batteries
Author(s)
Lu, Mu
Advisor(s)
Xia, Shuman
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Abstract
Lithium-ion batteries (LIBs) are being increasingly used in various applications, such as electric vehicles, grid energy storage systems, and portable consumer electronics. However, the growing market needs have imposed an increasing demand for a new generation of energy storage solutions with improved safety, high energy and power density, and environmental sustainability. Currently, commercial lithium-ion batteries utilize liquid electrolytes, which contain flammable organic solvents. During battery punctual or accidental overcharging, they can easily catch on fire and are environmentally hazardous.
To address the above problem, a new class of LIBs, namely solid-state lithium-ion batteries (SS-LIBs), has been under active investigation over the past decades. In a SS-LIB, the conventional liquid electrolyte is replaced by a solid electrolyte (SE), which is safer and more environmentally friendly. The advancement of SS-LIBs is also motivated by the potential ability of SEs to suppress dendrite formation when cycled against metallic lithium, which has the highest energy density among all LIB anode materials. However, a variety of ex situ and in situ experiments have shown that Li dendrites may still grow within SEs and the nature of this process is still unclear. The performance of SS-LIBs is further limited by the poor interfacial stability and mechanical incompatibility between SEs and electrodes. Therefore, understanding these chemomechanical failure mechanisms is crucial for the development of next-generation LIBs.
In this work, we aim to fill in this critical knowledge gap using an in situ characterization testing platform alongside ex situ nanoindentation measurements. To better understand the role of metallic lithium in the dendrite penetration process, a comprehensive study employing environmentally controlled nanoindentation technique is conducted to characterize the fundamental mechanical behavior of metallic lithium. In this study, the size- and temperature-dependence of the elastic, plastic and creep properties of metallic lithium was examined to provide the much needed insights into the fundamental properties of lithium.
To unravel the coupled chemo-mechanical degradation mechanisms of SS-LIBs, we developed a new in situ chemomechanical testing platform integrating optical imaging technique with electrochemical impedance spectroscopy (EIS), stress and electrical measurements. The integrated testing platform was first applied to studying the interfacial failure mechanisms of sulfide SEs when cycled against metallic lithium. The experimental setup was also modified and used to investigate the dynamic interaction between dendrite propagation and crack growth an oxide SE. Optical images of symmetric Li/SE/Li cells were acquired under controlled cycling conditions and were analyzed using digital image correlation (DIC) to obtain the resistance to crack growth caused by Li dendrite penetration.
The insights gained on the chemomechanical degradation mechanisms of SS-LIBs in our work assist in the development of next-generation LIBs. The ex situ and in situ methodologies developed in this thesis provide unprecedented capabilities for chemomechanical characterization of rechargeable battery materials.
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Date Issued
2023-09-20
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Text
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Dissertation