Won Joon Jeong

Advisor: Prof. Matthew T. McDowell

will propose a doctoral thesis entitled,

Understanding High-Capacity Anode Materials in Solid-State Batteries: Reaction Mechanisms and Interface Evolution

On

Thursday, April 24, 2024

12pm – 2pm

Callaway Manufacturing Research Building, Auditorium 101
and

Virtually via MS Teams

https://teams.microsoft.com/l/meetup-join/19%3ameeting_NWM2OTI2YWMtNTI0Yi00NTBlLThkNjItYjM3YWM1MzE4OWI5%40thread.v2/0?context=%7b%22Tid%22%3a%22482198bb-ae7b-4b25-8b7a-6d7f32faa083%22%2c%22Oid%22%3a%226fd62816-b43e-4ad4-810f-d8f0645c865c%22%7d

Committee:

Prof. Matthew T. McDowell – School of Materials Science and Engineering (advisor)

Prof. Meilin Liu – School of Materials Science and Engineering

Prof. Seung Soon Jang – School of Materials Science and Engineering

Prof. Anju Toor – School of Materials Science and Engineering

Prof. Hailong Chen – George W. Woodruff School of Mechanical Engineering

Abstract

High-capacity anode materials, including lithium metal and alloy anodes, offer substantial advantages for solid-state batteries over conventional lithium-ion batteries. However, their practical implementation is limited by interfacial instability during repeated cycling. Morphological changes in the anode during electrochemical cycling can cause loss of contact with the solid-state electrolyte, resulting in increased cell resistance. Unwanted side reactions between high-capacity anode materials and solid-state electrolyte present an additional challenge that must be addressed. Furthermore, the electrochemical behavior of these anode materials under varying operating conditions remains poorly understood.

Previously, I investigated the electrochemical lithiation/delithiation behavior of 12 different elemental alloy anodes in solid-state batteries with Li6PS5Cl solid-state electrolyte, enabling direct behavioral comparisons. The materials showed highly divergent first-cycle Coulombic efficiency in half cells, ranging from 99.3% for indium to ~20% for antimony. Through microstructural imaging and comparison to liquid-electrolyte cells, I have identified that lithium trapping within the foil during delithiation as the principal reason for low Coulombic efficiency in most materials, with interfacial contact loss exacerbating this effect. The exceptional Coulombic efficiency of indium was found to be due to unique delithiation reaction front morphology evolution in which the high-diffusivity LiIn phase remains at the solid-state electrolyte interface. This comprehensive study links elemental composition to reaction and degradation behavior for alloy anodes and thus provides guidance towards better solid-state batteries.

Based on the findings from my previous work, I propose two research objectives to advance the understanding of interfacial instability in high-capacity anode materials in solid-state batteries. First, I aim to investigate interphase formation at the interface between alloy anodes and solid-state electrolyte under various stack pressures. This study will highlight the potential advantages of alloy anodes over lithium metal anode in suppressing interphase growth kinetics. Finally, I will examine interfacial evolution at low temperatures in lithium metal and anode-free solid-state batteries. This work will identify key challenges associated with low temperature operation and offer guidance for developing high-performance lithium metal based solid-state batteries under such conditions.