CAREER: Unveil the Electrical Double Layer Structure in Battery Electrolyte Systems

Energy storage is a key technology to the Nation’s economy, safety, and commitment to mitigate climate change. It has been increasingly important with the expanded widespread demand among most industries, spanning from large-scale electrical grid storage to electric vehicles and consumer electronics. While the innovation of lithium-ion batteries (LIB) has revolutionized daily life, the industry is hitting a major obstacle to keep pace with increasing demand of customers due to the lack of breakthrough in fundamentals of battery technology. The electrical double layer (EDL) is the interfacial layer at the electrode/electrolyte boundary. It governs the electron transfer, ion migration, and solvent molecular adsorption/desorption processes. In battery applications, EDL significantly impacts performance like cyclability, power rate, capacity retention, and safety. However, the fundamental knowledge of EDL in battery electrolytes is still lacking. This project aims to unveil the properties and structures of the EDL in LIB electrolyte systems, determine how these properties impact battery performance, and thus guide the development of safer, more efficient, powerful, and reliable battery systems. Moreover, this program will serve as an education vehicle to 1) build a strong and sustainable pipeline that supplies high quality battery experts to academia and industry and 2) create an inclusive and equitable battery research and education environment for students and scholars with diverse backgrounds.The goal of this CAREER project is to develop a novel in-situ characterization platform to directly probe the potential dependent properties and structure of EDL in typical LIB electrolytes (high concentration and nonaqueous). The objective of this work is to 1) characterize EDL properties by electrocapillarity with static mercury electrode, 2) resolve the EDL structure by varied angle Attenuated Total Reflection-Fourier Transform infrared (ATR-FTIR), and 3) bridge the EDL properties to electrochemical behavior of battery electrolytes. This interfacial characterization platform will enable the characterization of a series of interfacial and EDL properties in LIB electrolytes, including interfacial free energy, surface excess of ions, Potential of Zero Charge (PZC), surface charge density, and double layer capacitance. The knowledge derived from this project will accelerate the design optimization of electrolyte, shed light on interfacial modification of electrode, and advance the fundamental knowledge of solid/liquid interface. The characterization approaches developed in this project are transformative in more battery electrolyte systems beyond LIB electrolytes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.