Interfacial electrochemo-mechanical studies of nano/microstructures in lithium-ion batteries

1. Nickel current collector | Silicon (anode) Silicon has emerged as a promising anode material due to its high lithium storage capacity. While commercial batteries may now include silicon particles, porous three-dimensional (3D) scaffolded silicon electrodes may enable higher silicon loading by providing space to accommodate the silicon volume expansion during alloying with lithium without significant electrode swelling. However, the electrochemo-mechanical response of silicon film on a metal scaffold is not well understood due to the complex morphology of the scaffold. Here we explore the role of scaffold curvature on the cycling behavior of silicon films and show that different curvatures exhibit distinctive silicon failure modes. Negative curvature shows tensile and compressive stress driven-crack opening failure. Positive curvature is correlated with tensile stress driven buckling. Zero curvatures (a flat surface) exhibit fragmentation. The detailed electrode morphology and chemistry for these systems is evaluated via scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDS). COMSOL Multiphysics simulations also show the electrochemo-mechanics of silicon are curvature-dependent. These findings point the way towards design strategies for next-generation 3D architected silicon anodes with improved cycling integrity. 2. Lithium cobalt oxide, LiCoO2 (cathode) | Lithium indium chloride, Li3InCl6 (LIC, solid-electrolyte) All-solid-state batteries (ASSBs) are emerging as a promising energy storage solution due to their enhanced safety, high energy density, and improved performance over conventional lithium-ion batteries (LIBs). The use of solid electrolytes, such as sulfides, oxides, or halides, helps mitigate issues like leakage, flammability, and dendrite formation typically associated with liquid-electrolyte systems. In this thesis, layered LiCoO2 (LCO) cathodes and Li3InCl6 (LIC) solid-electrolytes were selected for their high energy density and oxidation stability. Our study via scanning transmission electron microscopy (STEM) reveals that a spinel structure forms uniformly (~15 nm) on the LCO surface over extended cycling at high temperatures, leading to performance degradation. Through various testing conditions—including voltage holding, resting, and different charge rates—we identified that the spinel phase nucleates under electrochemical influence at high temperatures, during fast charging at room temperature, and at high states of charge. This phenomenon is corroborated by electrochemical impedance spectroscopy (EIS), which shows a growth in interfacial resistance in the presence of the spinel phase. These findings provide valuable insights into the origins of spinel formation and its role in the accelerated degradation of solid-state batteries.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science & Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Jeong, Hyewon

Contributors dc:contributor

• Braun, Paul
• Zuo, Jian-Min
• Krogstad, Jessica Anne
• Wang, Pingfeng

• Electrochemo-mechanics
• Silicon Anodes
• Solid-state Batteries
• Engineering Cei (cathode-electrolyte Interphase)
• Scanning Transmission Electron Microscopy (stem)

Statement dc:rights

• Copyright 2025 Hyewon Jeong

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130178

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130178