Jakub Pepas

Advisors: Prof. Hailong Chen and Prof. Meilin Liu

will propose a doctoral thesis entitled,

Development and Application of Novel High-Throughput in situ X-ray Diffraction Techniques for Electrochemical Systems

On

Friday, August 15, 2025

11am -1pm 

Love Building 210

or virtually via Zoom: 

Join meeting here

Meeting ID: 925 3214 1399

Committee:

Prof. Hailong Chen - Woodruff School of Mechanical Engineering (advisor)

Prof. Meilin Liu - School of Materials Science and Engineering (co-advisor)

Prof. Guoxiang (Emma) Hu - School of Materials Science and Engineering

Prof. Matthew McDowell - School of Materials Science and Engineering

Prof. Ting Zhu - Woodruff School of Materials Science and Engineering

Abstract

    In situ X-ray diffraction (XRD) has been applied extensively to analyze structural changes in materials undergoing electrochemical processes, for instance battery cycling. However, the local environment during electrochemical processes is highly complex, requiring many trials to fully resolve the effects of material parameters such as concentration, current density, and temperature, etc. High-throughput in situ XRD (HT in situ XRD) techniques are desired to accelerate materialsdesign by evaluating the dynamic effects of many deposition conditions in a single experiment. In this dissertation, I will use HT in situ XRD to investigate the dynamic structural changes of various materials systems during electrodeposition, battery cycling, and corrosion.

    Previously, we developed a testing system for high-throughput, gradient electrodeposition. Byvarying the distance between working and counter electrodes, we are able to observe the effects of applying a wide range of current densities over the course of a single experiment. We developed an analytical model to quantify and predict the current density distribution during the deposition process. Next, I applied this model to a novel system for the fabrication of multi-component alloys through guided sequential electrodeposition and annealing, allowing for the guided synthesis of combinatorial multi-metal samples. In this dissertation, I will be applying this high-throughput technology in three primary directions:

    First, I will apply the sequential electrodeposition and annealing method to perform a high- throughput characterization study of the phase, composition, and mechanical properties of compositionally graded samples of binary NiCo alloy thin films, identifying the critical compositions for phase transition and optimal parameters for high hardness. Second, I will perform a multi-objective optimization of compositionally graded multi-component NiCoFeCr alloy samples fabricated through the sequential electrodeposition method, analyzing their mechanical properties, composition, structure, and corrosion performance with high throughput. Third, I will perform high-throughput studies of the delithiation and charge equilibration mechanisms in lithium-ion battery materials through the in situ study of Li-ion cathodes with induced Li concentration gradients. Through this study, I expect to observe both the local charge inhomogeneity in cathode particles as a function of C-rate and dynamics of charge transfer and equilibration in heterogeneous cathodes.