SUBJECT: Ph.D. Dissertation Defense
BY: Michael Lee
TIME: Tuesday, May 3, 2022, 1:00 p.m.
PLACE:, Virtual
TITLE: Designing 3D Structured Electrodes and Electrolytes for High-Performance Rechargeable Batteries
COMMITTEE: Dr. Seung Woo Lee, Chair (ME)
Dr. Peter J. Hesketh (ME)
Dr. W. Hong Yeo (ME)
Dr. Matthew McDowell (MSE)
Dr. Thomas Fuller (CHBE)


There is a critical impediment to the practical use of lithium (Li)-ion batteries (LIBs) at low temperature conditions owing to the sluggish intercalation reactions and metallic Li-plating issue. The promising strategy to resolve these hindrances is the transition of the charge storage mechanism from the diffusive intercalation to the capacitive charge storage. Here, we report structure-controlled 3D graphene-based electrodes prepared by controlling the stacking process of graphene sheets via an aerosol drying process. The defective structures of graphene are identified to utilize the surface-charge storage mechanism. The electrochemical analysis is employed to elucidate the charge storage mechanisms of electrodes as a function of potential and temperature. This study is to demonstrate that the 3D structured electrodes can effectively utilize the surface-charge storage mechanism for improving low-temperature performances. The use of Li metal anodes in solid-state batteries (SSBs) has emerged for replacing conventional LIBs. Solid-state electrolytes (SSEs) are a key technology for safe operation of Li-metal batteries (LMBs) by suppressing the uncontrolled dendritic Li. However, the mechanical property and electrochemical performance offered by current SSEs do not suffice for practical applications of LMBs. Here, we report a class of elastomeric SSEs having a 3D interconnected plastic crystal phase. The elastomeric electrolytes show a combination of mechanical robustness, high ionic conductivity, low interfacial resistance, and high Li-ion transference number. The elastomeric electrolytes enable stable operation of full cells comprising a limited Li source, a thin electrolyte, and a high-loading LiNi0.83Mn0.06Co0.11O2 cathode at a high voltage of 4.5 V at ambient temperature, delivering a high specific energy exceeding 410 Wh kg-1. The elastomeric electrolyte system presents a powerful strategy for enabling stable operation of high-energy, solid-state Li batteries.