Date of Award
8-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Materials Science and Engineering
Committee Chair/Advisor
Dr. Jianhua Tong
Committee Member
Dr. Kyle Brinkman
Committee Member
Dr. Raj Bordia
Committee Member
Dr. Fei Peng
Committee Member
Dr. Hai Xiao
Abstract
As a society, we’ve exhausted an extreme amount of fossil fuels and put an overwhelming strain on Earth’s natural resources. From this, it is critical to think about the successful future of our planet and ourselves by developing energy devices such as all-solid-state lithium-ion batteries (ASSLIBs). These devices offer a greener and more efficient alternative to power our daily lives, such as electric vehicles (EVs), portable electronics, medical devices, grid-scale energy storage, and aerospace/aviation. ASSLIBs are an excellent alternative to liquid-state batteries, which pose dangerous safety concerns (e.g., flammability, electrolyte leakage, etc.). These ASSLIBs are known to have generally high energy densities, making them a viable option for use in almost any application. Each battery contains at least three components, i.e., a cathode, electrolyte, and anode. While cathodes and anodes facilitate the transfer of electrons from one to the other, the electrolyte is probably the most important component, which helps ionic species move from cathode to anode (and vice versa). The ease with which these ions move back and forth is determined primarily by the electrolyte itself. One promising option for solid-state electrolytes (SSEs) is Li7La3Zr2O12 (LLZO), which has been known to achieve high ionic conductivity (~10-3 S⸱cm-1) and high energy densities. And one promising option for a sintering aid and conductivity enhancer is Al3+, which will help to substitute for Li sites of LLZO and reach its full potential. However, to even begin approaching these high performances, the material processing conditions must be optimized and improved to meet the ever-growing needs of society.
Herein, the current work will dive into the effect of sintering conditions of LLZO SSE, namely solid-state reactive sintering (SSRS). Similar to the solid-state sintering (SSS) method, which uses a programmable furnace to heat up ceramic materials and cause densification and coarsening to take place, the SSRS method uses this same method to heat up a material, additionally inducing chemical reactions within said material (combines both sintering and reactions into one step). By altering the SSRS processing conditions (i.e., dwell time and dwell temperature), we can gather a suite of material properties (pure/impure phase transitions, microstructural evolutions, and geometrical changes) to ensure an optimization of reaction and sintering procedures. In the context of LLZO, sintering in a normal air environment is challenging and causes several unwanted phases/impurities, which ultimately damage the ionic conductivity, which is the ultimate material property to achieve for this ASSLIB application. Therefore, an inert atmosphere of Ar gas was passed into the furnace chamber to limit the interaction of LLZO with air during SSRS and improve sintering conditions. Altering these conditions can also inform future experiments that involve material property optimization for any material system.
Alternatively, a potentially more efficient method to SSRS is its laser counterpart, rapid laser reactive sintering (RLRS). Analogous to SSS, rapid laser sintering (RLS) is the process of using a laser (in this work, a CO2 laser) to improve densification and coarsening for already-pure components. The RLRS method has been used for other energy materials, including solid oxide fuel cells (SOFCs) and protonic ceramic fuel cells (PCFCs), and, therefore, shows promise in its capability as a quick, energy-efficient, and effective reactive sintering method. The work in this dissertation explores RLRS’s effect on Al-doped LLZO, like SSRS’s impact on the same material. Instead of changing key parameters such as dwell time and dwell temperature for SSRS, there are several for RLRS, such as power, scan speed, and defocus distance, which creates an even more complex terrain for sintering Al-doped LLZO with a relatively nascent technological method. Here, the discussion will be dominated by a microstructural roadmap with some crystallographic analysis of varying parameters to more accurately define this material’s compatibility with RLRS.
Recommended Citation
Santomauro, Aaron, "Investigation of Solid-State Reactive Sintering and Rapid Laser Reactive Sintering for Al-Doped Li7La3Zr2O12 Solid-State Electrolyte" (2025). All Dissertations. 4042.
https://open.clemson.edu/all_dissertations/4042