Modeling the electrical double layer at solid-state electrochemical interfaces.

Area of Science:

• Materials Science
• Electrochemistry
• Computational Physics

Background:

• Traditional electrical double layer (EDL) models are inadequate for all-solid-state electrochemical systems.
• Understanding the interface between solid electrolytes and electrodes is crucial for solid-state battery development.
• Existing models fail to capture the complex interplay of electronic and ionic charge carriers at solid-state interfaces.

Purpose of the Study:

• To develop a more general and accurate model for the electrical double layer (EDL) at solid-state electrochemical interfaces.
• To self-consistently capture the coupled electronic and ionic phenomena within the space-charge layer of solid-state batteries.
• To provide a framework for designing optimal interlayer materials and thicknesses to enhance lithium ion transport.

Main Methods:

• Developed a generalized EDL model based on the Poisson-Fermi-Dirac equation.
• Integrated the model with density functional theory (DFT) predictions.
• Applied the model to analyze the EDL structure in contact with a lithium metal anode, including Li$_{7}$La$_{3}$Zr$_{2}$O$_{12}$ (LLZO), LiF, Li$_{2}$O, and Li$_{2}$CO$_{3}$.

Main Results:

• The model successfully captures electronic band bending and defect concentration variations in the space-charge layer.
• Detailed EDL structures were elucidated for LLZO, LiF, Li$_{2}$O, and Li$_{2}$CO$_{3}$ in contact with Li metal.
• The model provides insights into minimizing electrostatic barriers for lithium ion transport across solid-state interfaces.

Conclusions:

• The proposed Poisson-Fermi-Dirac based EDL model offers a more general and accurate description for solid-state electrochemical interfaces.
• This model enables the rational design of interlayers to optimize interfacial properties and improve lithium ion conductivity in solid-state batteries.
• The findings are critical for advancing the development of high-performance and safe all-solid-state batteries.