Master of Science, The Ohio State University, 2022, Mechanical Engineering

The development of next generation electrode materials provides the opportunity to significantly increase the energy density of lithium-ion batteries. These materials form alloy compounds with lithium and have specific capacities that are much higher than of graphite. Of these materials, silicon, which has a theoretical capacity of ~4200 mAh/g, is the closest to commercialization. However, silicon experiences large volume changes during the lithiation and delithiation processes. This ultimately leads to stress generation within the particle causing fracture, loss of active material, and rapid loss of cell capacity. The differences in behavior for silicon-based anodes compared to traditional graphite anodes highlights the need for the development of physics-based models to capture the effects of volume change and stress generation on the solid-state diffusion process. One such model proposed by Christensen and Newman describes the effects of diffusion, volume change, and stress generation in a spherical electrode particle. This mathematical model takes the form of an index-2 set of differential and algebraic equations which require implicit numerical methods to obtain a solution. Due to the mathematical complexity and high computational time and memory requirements, this model is not suited for controls or estimation-based applications. This thesis presents a mathematical reformulation of the Christensen-Newman equations using index-reduction to obtain a semi-explicit index-1 version of the model. Index reduction allows for the differential and algebraic equations to be decoupled enabling the use of explicit time marching methods. This reformulation will enable the integration of this model into larger cell level frameworks as well as estimation and controls-based applications. The reduced index model is verified against a fully implicit benchmark solution for a graphite anode. A local sensitivity analysis is performed to ascertain the effects of the mechanical (open full item for complete abstract)

Committee: Marcello Canova (Advisor); Jung Hyun Kim (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2020, Mechanical Engineering

Silicon (Si) and Silicon Monoxide (SiO) have been considered promising candidates for the active material of the negative electrodes for the next-generation Li-ion batteries (LiBs), primarily due to their high specific capacities (Si:3579 mAh/g, SiO:1710 mAh/g) compared with state of the art graphite-based anodes (372 mAh/g). However, poor cycle-life and rate capability resulting from the large volume expansion (Si:280%, SiO:118%) during lithium uptake in Si or SiO particles are currently preventing this anode materials from being a viable commercial solution for electrified vehicle applications. These issues warrant careful and thorough studies to first characterize many important electrochemical properties of Si-based anode materials. In addition, simulation tools that can advance performance prediction and system-level studies, such as the first-principle, electrochemical models already developed for state of the art lithium ion battery technologies, need to be developed for silicon-based anodes due to the fundamental physical difference in their behavior when compared to graphite-based anodes. The lack of such models is due to not only the lack of information that are necessary for model parameterization but also the difficulties in developing mathematical representations of electrochemical phenomena induced by large volume changes. This dissertation aims at providing valuable experimental information and simulation tools that will remarkably accelerate the development of Si-based anode materials for high energy density LiBs. First, important electrochemical properties of Si-based anodes such as Open Circuit Potential (OCP), sold-state diffusion coefficient, and volume change were characterized and documented through a set of experiments. The rate capability of Si and SiO anodes were tested and compared up to 20C which demonstrated superior high C-rate performance of SiO. The diffusion of Li in SiO was found faster than in Si particles. More importantly, th (open full item for complete abstract)

Committee: Marcello Canova (Advisor); Jung-Hyun Kim (Committee Member); Hanna Cho (Committee Member); Anne Co (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2014, Geography

Ongoing and future climate change forces dramatic alteration to physical, biological and social systems worldwide. Climate change has an especially significant impact on the extent and distribution of ice mass in mountainous regions near populated areas, where decreased ice mass transforms runoff characteristics of alpine watersheds, increases water scarcity, and human vulnerability, and changes both ecosystems and tourism. This dissertation research project focuses on calculating changes in volume and surface areas of glaciers in the Cordillera Blanca, Peruvian Andes. I incorporate three discrete but interrelated studies: (1) A comparative assessment of 2008 Light Detection and Range (LiDAR) Digital Elevation Models (DEMs) and 1962 aerial photo DEMs based on non-glacierized terrain. I present the first LiDAR data acquired over tropical glaciers, and compute volume change of six glaciers by DEM differencing, along with a quantitative characterization of the uncertainty from processing different DEM data. Sources of limitations are found in the historical aerial photos, different viewing geometries through highly rugged terrain relief and uncertainties in the processing stage. The DEM surface offsets for all slopes and aspects differ for each study such that the mean difference became larger when the slope angle gets steeper and for aspects of west (W) to north (N). The calculation of the mean surface elevation change over the 46 years indicates a glacier thinning ranging from a minimum of 9.5 m and up to 64 m after performing a simple adjustment by adding mean elevation offsets of each site as a method for removing the offsets between DEMs. (2) The change in volume and surface area of six glaciers in the study area between 1962 and 2008. The loss of glacier surface areas ranges from 30.79% to 72.62%, which corresponds to the changes in glacier volume of 0.019 km3 to 0.150 km3 depending on the specific glacier under investigation. Based on the 13 different epochs (open full item for complete abstract)

Committee: Bryan Mark (Advisor) Subjects: Geography

Master of Science, Miami University, 2010, Physics

Reduced nicotinamide adenine dinucleotide (NADH) plays a central role in cellular metabolism via a redox reaction. Its conformation is physiologically significant as NADH takes a folded conformation when free and an unfolded conformation when protein bound. This study uses fluorescent emission spectroscopy and solvent denaturation to examine pressure's role in the equilibrium conformation of NADH in solution (10 and 20 μM in MOPS buffer, pH 7.4). Quartz capillary-based high-pressure chambers house samples up to 51 MPa which are excited with a 337 nm nitrogen laser. Using a two-state model, the free energy of unfolding is determined and the volume change of unfolding is measured to be 24.9 ml/mol assuming an Arrhenius relationship. The validities of the two-state model and the selected concentration range are assessed. Results are significant to understanding pressure effects on cellular metabolism and for future studies probing the fluorescent signals of cells under pressure.

Committee: Paul Urayama PhD (Advisor); Burçin Bayram PhD (Committee Member); Jaeger Herbert PhD (Committee Member) Subjects: Biophysics; Physics