Won Joon Jeong
Advisor: Dr. Matthew McDowell
will defend a doctoral thesis entitled,
Reaction Mechanisms and Interphase Evolution of High-Capacity Anode Materials in Solid-State Batteries
On
Tuesday, July 14 at 11:00 a.m. (EDT)
MRDC, Room 4211
and
Virtually via MS Teams
https://teams.microsoft.com/meet/258683608785957?p=k8yredsHCsXTmh2iSZ
Meeting ID: 258 683 608 785 957
Passcode: 79ii2sx6
Committee
Dr. Matthew McDowell – School of Materials Science and Engineering (advisor)
Dr. Meilin Liu – School of Materials Science and Engineering
Dr. Seung Soon Jang – School of Materials Science and Engineering
Dr. Anju Toor – School of Materials Science and Engineering
Dr. Hailong Chen – George W. Woodruff School of Mechanical Engineering
Abstract
Solid-state batteries (SSBs) have attracted significant attention as next-generation energy storage systems because of their potential to provide higher energy density and improved safety than conventional lithium-ion batteries. High-capacity anode materials, such as lithium metal and alloy anodes, offer great promise for SSBs by enabling significantly higher energy densities. However, the practical implementation of these anodes in SSBs remains limited by interfacial instabilities, including electrolyte decomposition and contact loss at the electrode/electrolyte interface, particularly under demanding operating conditions such as low stack pressures and low temperatures. Addressing these challenges requires a fundamental understanding of the electro-chemo-mechanical processes governing the evolution of electrode/electrolyte interfaces during battery operation.
Although alloy anodes have been proposed as promising alternatives to lithium metal for SSBs, their electrochemical behavior remains poorly understood. By systematically evaluating twelve elemental alloy anodes with a sulfide solid electrolyte, this work demonstrates that each alloy exhibits distinct lithiation and delithiation behavior, resulting in a wide range of electrochemical reversibility. The study further identified irreversible lithium trapping within the alloy during delithiation as the primary mechanism responsible for the reduced Coulombic efficiency.
The formation and evolution of interphase at alloy anode/sulfide solid electrolyte interfaces were further investigated. An advanced electrochemical technique, coulometric titration time analysis, was employed to directly monitor electrolyte decomposition and quantify interphase growth kinetics. The results showed that alloy anodes substantially suppress interphase growth relative to lithium metal. Furthermore, this study reveal that interphase evolution strongly depends on the electrode/electrolyte contact area, which is governed by the mechanical properties of the electrode as well as its morphological evolution during lithiation.
Finally, the influence of various alloy-based interlayers on the low-temperature operation of anode-free sulfide SSBs was investigated. Through combined electrochemical measurements, impedance spectroscopy, and cryogenic focused ion beam characterization performed between 25 °C and 0 °C, this work revealed the mechanism behind failure of anode-free SSBs at low temperatures. At 0 °C, the interlayers showed limited effectiveness, with altered mechanical properties of lithium metal and reduced lithium transport kinetics through the interlayer identified as the primary factors governing its diminished performance. Collectively, the overall findings provide fundamental insights and practical design guidelines for developing novel high-capacity electrode materials and stable electrode/electrolyte interfaces for sulfide solid-state batteries operating under commercially relevant conditions.