Determination of the Exchange Current Density at Lithium │ Polymer Electrolyte Interfaces

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Interfacial processes significantly impact solid-state battery internal resistance.
• Electrochemical reactions at the lithium│polymer interface are complex and change during battery cycling.
• Accurate determination of exchange current density (j0), a key kinetic parameter, is challenging due to overlapping impedance contributions.

Purpose of the Study:

• To develop and validate a reliable method for determining the exchange current density (j0) at the lithium│polymer electrolyte interface.
• To enable better analysis of interfacial processes and reactions in polymer electrolyte-based solid-state batteries.
• To address the discrepancies in j0 values obtained from different measurement methodologies.

Main Methods:

• Combining electrochemical impedance spectroscopy (EIS) with Bayesian inference and distribution of relaxation times (DRT) analyses.
• Utilizing polyethylene oxide (PEO)-based polymer electrolytes as a model system.
• Validating EIS-derived j0 values using DC polarization measurements fitted to a modified Butler-Volmer model.

Main Results:

• A robust methodology for accurately determining j0 in polymer electrolytes was established.
• The combined EIS, Bayesian inference, and DRT approach provided reliable kinetic data.
• Validation against DC polarization measurements confirmed the accuracy of the developed method.

Conclusions:

• The presented method enables reliable determination of exchange current density (j0) for polymer electrolytes.
• This facilitates a deeper understanding of interfacial charge transfer kinetics in solid-state batteries.
• Accurate j0 values are crucial for optimizing the performance and longevity of polymer electrolyte-based batteries.