Effect of the Electrical Double Layer (EDL) in Understanding the Correlation of Metal Plating/Stripping and Electrolyte Decomposition at Metal/Electrolyte Interfaces

Hui (Claire) Xiong, Micron School of Materials Science and Engineering, Boise State University, Boise, ID, 83725

Elton Graugnard, Micron School of Materials Science and Engineering, Boise State University, Boise, ID, 83725

Yue Qi, Engineering, Brown University, Providence. RI, 02912

Weiyang Li, Engineering, Dartmouth College, Hanover, NH, 03755

Rechargeable batteries have revolutionized how we store and use energy in many ways. High energy/power, and long-life batteries are desired for future applications. However, the high demands in performance have also placed a daunting task to design new battery systems that satisfy all categories. Rechargeable metal batteries (RMBs) are attractive because the high theoretical capacities of metal electrodes. Nevertheless, due to the low electrode potentials of metal electrodes (e.g., Li, Na, K, Mg … and their alloys), they often operate outside of the thermodynamic stability windows of most liquid electrolytes. Electrolyte research for these high-capacity metallic electrodes has recently moved away from traditional low concentration (dilute) electrolytes to high concentration electrolytes (e.g., solvent-in-salt electrolytes) and with heterogenous concentration nanostructures (e.g., in localized high concentration electrolytes, LHCE). This places new challenges in understanding the electrochemical processes at the electrode/electrolyte interface in these new electrolyte systems. The electrical double layer (EDL) is fundamental to all electrochemical devices where charge transfer reactions occur at electrified interfaces. While the EDL has generally been explained through classical models, including the Helmholtz, Gouy-Chapman, and Stern models, such models are no longer sufficient in predicting EDL structures and subsequent charge transfer processes when the electrolytes deviate from the dilute concentration condition assumed by current models. This is indeed the case in many of the new electrolyte systems developed in the past few years for RMBs. Due to the difficulty in balancing quantum accuracy and computational efficiency at complex electrified interfaces and challenges in characterizing the nanometer-sized EDL near the electrified interface, the EDL models remain ineffective for design advancement. There is neither established models, theory, nor experimental characterizations to fully describe the EDL and its effect on the consequent electrolyte decomposition and subsequent solid electrolyte interphase (SEI) formation as well as metal plating/stripping reactions in RMBs. This proposal aims to bridge the gap of fundamental knowledge and use-inspired science in RMBs through the development of a new unified EDL model that can predict the phenomena occurring at the interfaces between metal electrodes and advanced electrolytes. This project brings together experimental and theoretical experts from three Established Program to Stimulate Competitive Research (EPSCoR) states (Idaho, New Hampshire, and Rhode Island) with expertise in electrochemistry, chemistry, materials science and engineering, and artificial intelligence (AI)/machine learning (ML) modeling and simulation, along with four National Labs (Argonne, Idaho, Oak Ridge, and Pacific Northwest) to build regional and national capacity in advanced EDL models for Electrochemical Reactions at Electrified Interfaces (EREI) to enable  advanced battery materials research (BMR). This project serves as a key enabler for AI-driven battery design. 

The proposed EREI Implementation project will overcome the technical challenges of establishing new EDL models through a concerted experimental and computational approach to understand the structure-property relationship in different metal or alloy systems for RMBs. The specific Objectives of this research are to: (1) develop EDL models at different metal (e.g., Li, Na, K) or alloy interfaces via feeding molecular dynamics (MD)-predicted EDL structures into density functional theory (DFT) calculations, and calculating the metal decomposition potential within the EDL; (2) calibrate metal plating potentials using an internal standard reference, and validate the theoretical calculations; (3) control surface state via atomic layer deposition and graphene-based surface coating, and (4) determine the EDL structure and key factors underpinning the SEI formation and metal plating/stripping through in situ vibration spectroscopy, and scanning probe microscopy measurements. These objectives are interconnected to achieve the overarching goal.

This research was selected for funding by EPSCoR by the Office of Energy Efficiency and Renewable Energy and Basic Energy Sciences.

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