Organizational Unit:

School of Materials Science and Engineering

Permanent Link

https://hdl.handle.net/1853/70762

Parent Organization

Organizational Unit

College of Engineering

ArchiveSpace Name Record

https://finding-aids.library.gatech.edu/agents/corporate_entities/1126

Full item page

Publication Search Results

Now showing 1 - 10 of 24

Understanding the Role Mechanical Properties of Lithium Metal and Reacted Interphases Play in Solid-Solid Interfacial Chemo-Mechanics of Batteries

(Georgia Institute of Technology, 2023-06-02) Marchese, Thomas S.

Batteries are being incorporated into many technologies around us in the age of the ‘smart home’ and wearable technology. This, along with the electrification of vehicles, is creating exponential growth in the demand for high energy density batteries. Commercialization of lithium metal anode solid-state batteries would increase the energy density and safety by replacing the flammable liquid electrolyte with a solid-state electrolyte. Understanding the mechanical properties of lithium metal foil for battery anodes is imperative to forming and maintaining the solid-solid interfaces in these systems. Alkali metals have low yield strength (~1 MPa or lower) and are sensitive to creep; such deformation behavior needs to be understood under realistic multi-contact conditions prior to commercial implementation. Here, we demonstrate a new constant loading indentation mechanical deformation technique that employs indenter arrays of different sizes and spacings dropped into contact by force of gravity. The indenters probe the average material response to an array of contacting points, which is directly applicable to the conditions realized in bench-scale solid-state battery production. Testing across three different stainless steel indenter array sizes and a stainless-steel single pillar indenter of equivalent cumulative contact surface area at a single loading value demonstrated size effects of lithium metal foil. Examining the average total deformation observed over 12 minutes, the single pillar indenter averaged a total displacement of 99.40 ± 36.67 μm and the large indenter array averaged 99.16 ± 17.98 μm. Less deformation was seen by the medium indenter array which averaged 29.93 ± 9.06 μm, and by the small indenter array which averaged 45.00 ± 6.41 μm in total displacement. The smaller indenters are seen to penetrate to a lower depth due to increased frictional resistance by greater total surface area in contact and earlier horizontal interaction of neighboring indenters deformation volumes. This indentation array technique provides important knowledge for analyzing realistic deformation behavior of lithium and will provide insight into the action of creep in “healing” voids at the alkali anode/SSE interface. The importance of conformal component contact cannot be overstated in the creation of stable and reproducible electrochemical performance for lithium metal solid-state batteries.
Characterizing Solid State Battery Degradation Using Optical Microscopy and Operando X-Ray Tomography

(Georgia Institute of Technology, 2022-05) Prakash, Dhruv

The implementation of solid-state electrolytes (SSEs) into lithium-ion batteries shows much promise in enabling the use of higher energy density anodes, such as pure lithium metal. However, the implementation of SSEs and lithium metal anodes in lithium-ion batteries is currently not possible due to degradation mechanisms that lead to premature failure of the battery. These mechanisms, such as the formation of a new phase known as the interphase and the growth of lithium metal dendrites, are initiated at the interface between the anode and electrolyte and are linked to the current density at which the battery is cycled. Reported are two methods of characterizing the interfacial degradation phenomena that occur between lithium metal anodes and the SSE Li10SnP2S12 (LSPS). A novel symmetric battery setup was developed to allow an operando optical microscopy study of the lithium metal and SSE interface as charge was passed through the battery. Though this characterization method presented challenges, interphase formation and dendrite growth were both observed. Further, operando x-ray computed tomography of a novel cell geometry provided detailed three dimensional scans that also showed evidence of interphase growth and dendrite formation. Additionally, interfacial void formation was identified, indicating a loss of contact that increases current density. These results provide insight into the failure of solid-state batteries and show how operando optical microscopy and x-ray tomography can be used to gain a more complete understanding of the degradation of higher energy density lithium-ion batteries.
Compositional analysis of laser welds in a Cu46.5Zr46.5A7 glass forming alloy

(Georgia Institute of Technology, 2021-12) Holberton, Harrison Tyler

Laser additive manufacturing is a promising manufacturing method of bulk metallic glasses. Study and understanding of the heat affected zone and fusion zones are crucial in developing this manufacturing technique. A cast Cu46.5Zr46.5A7 sample was processed at laser powers and scan speeds varying from 75-370W and 100-900 mm/s respectively to determine the effects of processing parameters on weld composition for use in additive manufacturing. Copper content was found to generally decrease through the weld fusion zone, and increase through the heat affected zone. Zinc was unexpectedly present in analysis. Cracking occurred at significantly different linear energy densities and appeared to correlate more strongly with laser power at these parameters, supporting previous research that using energy density alone to predict additive manufacturing processes.
REDUCING INTERFACIAL RESISTANCE OF LI-ION BATTERIES THROUGH ATOMIC LAYER DEPOSITION

(Georgia Institute of Technology, 2021-12) Lee, Hae Won

The attention to solid state batteries are increasing as electrical vehicles start to dominate automobile industry. Solid-state batteries (SSBs) are type of Li-ion batteries that have solid medium. They are regarded as the next-generation energy storage device for electric vehicles because they can potentially solve the problems of conventional Li-ion batteries. In conventional Li-ion batteries, when delivered in high energy densities, they had extremely high possibility for inflammation due to the presence of flammable liquid organic electrolytes. Also, though the use of Li metal anode may significantly increase energy density, likelihood of short circuiting the cell due to the growth of Li dendrites prevents the commercialization of Li-ion batteries with Li anodes. Thus, in order to provide safer and higher energy batteries, SSBs with nonflammable and mechanically robust SSEs which may suppress Li dendrite growth came up as an alternative solution. However, there are new challenges that need to be overcome for SSBs. Not only are they more expensive than conventional Li-ion batteries, but due to solid-characteristic of the electrolyte, SSBs have critical flaw of high resistance at the SSE-electrode interfaces. The performance of SSBs in high temperature environment may be safer, but the thick SSE membrane and low active loading with the electrodes do not show better performance when compared to the liquid electrolyte cells. To enhance the battery performance, the interfacial resistance in SSBs needs to be reduced. Therefore, the focus of our lab is to come up with a novel coating method that has the least interfacial resistance. This new study will utilize the atomic layer deposition (ALD) technique to coat metal oxides on electrodes and enhance the battery performance, as previous research by many scientists has already proven that metal oxide coatings are effective at reducing the interfacial resistance in SSBs.
An Investigation into the Glass Transition Temperature of Vapor Phase Infiltrated Organic-Inorganic Hybrid Materials

(Georgia Institute of Technology, 2021-05) Bamford, James

Glass transition temperature (Tg) is a fundamental property of a polymer that defines its upper service temperature for structural applications and is reflective of its physicochemical features. We are interested in how vapor phase infiltration (VPI), which infuses polymers with inorganic species to create hybrid materials, affects the glass transition temperature of a material. We examine Al2O3 VPI into poly(styrene-co-2-hydroxyethyl methacrylate) (PS-r-PHEMA) using trimethylaluminum (TMA) and water precursors. Our VPI precursors are selected to be unreactive towards the styrene monomer units and highly reactive towards the HEMA monomer units. Experiments were conducted on PS-r-PHEMA thin films (200 nm) spun-cast onto silicon wafers and infiltrated at 100°C with 4 hr. exposure times. Copolymers with varying fractions of HEMA units were investigated, from 0 mole % to 20.2 mole % HEMA. Volumetric swelling of the films after VPI and aluminum oxide film thicknesses after pyrolysis both confirmed higher metal oxide loading with higher fraction HEMA units. Tg was measured using a spectroscopic ellipsometer with a heating unit. We find that the glass transition temperature increases significantly with metal oxide loading. Copolymers with 0.0%, 3.0%, 7.7%, 11.5%, and 20.2% HEMA units experienced 6°C, 8°C, 22°C, 37°C, and 46°C increases in Tg respectively. Changes in Tg at low HEMA composition fit the Fox-Loshaek model for crosslinking phenomena which, along with a dissolution study on these materials, suggests that VPI alumina crosslinks PS-r-PHEMA. We conclude that VPI may be useful as a crosslinking process for designing the thermophysical and thermochemical properties of polymer thin films, fibers, and fabrics.
Extent of UV Curing in Highly Loaded Systems for Direct Ink Writing

(Georgia Institute of Technology, 2021-05) Adams, Zachary Kenneth

This study investigates the solidification of material 3D-printed via direct ink writing. This material, consisting of monomers, a photoinitiator and silicon microspheres was extruded onto a printing bed. The material was then irradiated with ultraviolet light to polymerize the monomers. Curing time and thickness of the material were varied in order to determine their effect on the solidification process. Quantification of the extent of cure was done using Fourier transform infrared spectroscopy. The data collected show that the degree of conversion tends to decrease as curing time decreases, but the data is inconclusive as to the specific relationship between time and degree of cure. However, due to a combination of a long method development process and the coronavirus pandemic, work on this project was halted before this trend could be definitely proven.
Optimizing Pressure in Compressive Textiles and Utilizing Smart Sensors to Monitor Patient Recovery

(Georgia Institute of Technology, 2019-05) Vagott, Jacob N.

This study was designed to examine how to better monitor patients throughout compression therapy. Compressive wraps are used to optimize blood flow in patients in order to encourage proper healing and decrease the likelihood of medical complications. The pressure being applied by the wrap determines its effectiveness, so it would be ideal if this could be monitored real-time. New advancements in smart sensors may allow for this to occur. Until then, it would be useful to have tables of elongation versus pressure, so that doctors and nurses have a reference that can be used to estimate the pressure being applied to the wound. Temperature and moisture sensing were also considered, since they could be used to monitor patient temperature and potentially sense fluid build-up. Skin temperature sensing was found to be possible using the SensorPush Temperature and Humidity Sensor. A table has been fabricated using tensile test data that shows the acceptable range of percent elongations for each tested compressive wrap. It was determined that stress relaxation is prevalent in compressive wraps, and this must be taken into consideration in future testing.
Load Dependent Fatigue Crack Initiation in High Purity Al

(Georgia Institute of Technology, 2018-05) Wang, Xueqiao

Fatigue crack initiation sites and mechanisms in metals and alloys have long been investigated, since metal components are often subjected to cyclic loading, and fatigue cracking is one of the major causes of failure. Therefore, understanding the dominant cracking mechanism under different conditions is essential for tailoring the composition and microstructure of metal components for better fatigue resistance under various loading conditions. Load dependent fatigue response in high purity aluminum (Al) is investigated. In low cycle fatigue, extrusions and intrusions are found to form on grain boundaries (GBs), especially prevalently at triples junctions. However, contrary to theories on extrusion formation from persistent slip bands (PSBs), no slip bands are observed in these specimens. Dislocation cells, on the other hand, are observed to form in higher densities and smaller sizes as stress amplitude increases. As extrusion formation occurs only after a threshold number of cycles, it might be a result of the progression of dislocation cell formation. In high cycle fatigue, no extrusions are observed at GBs, while microcracks form within grains. Therefore, high cycle fatigue life may be controlled by mechanisms other than dislocation cell formation, and involves transgranular, rather than intergranular, fracture.
Atomic Layer Deposition of Sub-Nanometer Inorganic Layers on Natural Cotton to Enhance Oil Sorption Performance in Marine Environments

(Georgia Institute of Technology, 2018-05) Short, Andrew E

Over 1 million tons of oil is inadvertently spilled each year. The economic and environmental costs of these spills are enormous and necessitate further development of environmentally friendly sorbent materials. Here, we demonstrate a vapor phase modification approach to create a new class of oil sorbents composed of cellulosic materials (cotton) coated with a sub-nanometer layer of inorganic oxide. This new cellulosic sorbent remains buoyant in water indefinitely and achieves a selective oil sorption capacity (23 g g-1 or 1.05 g cm-3) that is at least 35x better than untreated cellulose in aqueous environments. This new sorbent particularly excels under “realistic” conditions like continuous agitation (e.g. simulated waves) and pre-soaking in water (e.g., rain or forced immersion). When sorption performance is compared on a per-volume basis—which better captures use conditions than a per-mass basis—this modified natural product becomes comparable to the best sorbents reported in the literature, most of which require further expensive processing.
Applicability of Cytocompatible ALD Barrier Films as Protective Barriers for Biological Implants

(Georgia Institute of Technology, 2018-05) Adstedt, Katarina

The ability of atomic layer deposited (ALD) metal oxide films to serve as protective, encapsulating barriers for biological implants is determined through testing the corrosion resistance and degradation behavior of the films. Using plasma enhanced ALD (PE-ALD), metal-oxides are deposited at 100 oC onto gold electrodes. Through MTT cell proliferation assay, the films are determined to be cytologically compatible and will not cause harm to the implant host. Using electrochemical impedance spectroscopy (EIS), the films establish their relative chemical stabilities within three different biological environments, phosphate buffer solution (PBS), simulated sweat and simulated saliva. The resulting data from the EIS measurements demonstrates the rate of degradation for the four respective films and exhibits which films are best suited as protective barriers for biological implants. ALD Al2O3 is not suitable as an encapsulating layer as it demonstrates no corrosion resistance. Within PBS, ALD TiO2 establishes itself as the most stable film barrier while within simulated sweat and saliva ALD ZrO2 is the most chemically stable. The viability of ALD films in biological solutions and their enhanced corrosion resistances opens up the possibility for a new class of materials that can be used for the protection of bioimplants and wearable devices.