Modeling Insight into Battery Electrolyte Electrochemical Stability and Interfacial Structure.

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Electroactive interfaces are crucial for electrochemical energy devices.
• Electrolyte stability at electrode interfaces is key to device performance and longevity.
• Understanding local electrolyte composition and structure as a function of voltage is essential for manipulating interphases.

Purpose of the Study:

• To investigate molecular-scale solvent and ion partitioning in electrolyte double layers under applied potential.
• To predict changes in electrolyte stability and initial oxidation/reduction reactions based on interfacial composition.
• To explore strategies for manipulating interphases and expanding electrochemical device operating windows.

Main Methods:

• Molecular dynamics (MD) simulations of highly concentrated lithium aqueous and nonaqueous electrolytes.
• Quantum chemistry (QC) calculations on representative molecular clusters.
• Surface-enhanced infrared spectroscopy (SEIS) for experimental validation.

Main Results:

• Highly concentrated electrolytes exclude solvent from the positive electrode, enhancing oxidation stability.
• Anion adsorption/desorption behavior at the positive electrode can be tuned by chemical structure and potential.
• Proton transfer (H-transfer) reactions significantly lower solvent oxidation potentials, a critical factor for battery operation.
• F-transfer reactions and LiF formation during anion/solvent reduction are influenced by double-layer partitioning.

Conclusions:

• Molecular-level insights into interfacial electrolyte behavior enable prediction and control of electrochemical stability.
• Designing anions and understanding H-transfer reactions are critical for optimizing electrolyte performance.
• Interfacial compositional control offers a powerful tool for enhancing electrochemical device operation.