Overdetermination method for accurate dynamic ion correlations in highly concentrated electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Highly concentrated battery electrolytes offer enhanced safety and stability.
• Ion transport properties are crucial for battery performance and influenced by ion correlation.
• Accurate determination of transport parameters like Onsager coefficients and thermodynamic factors is essential.

Purpose of the Study:

• To investigate the minimum experimental data required for accurate characterization of transport properties in concentrated electrolytes.
• To compare the uncertainties in Onsager coefficients and thermodynamic factors obtained from different numbers of experimental measurements.
• To evaluate the impact of overdetermination on the reliability of electrolyte transport property analysis.

Main Methods:

• Combined electrochemical impedance spectroscopy, electrophoretic NMR, and concentration cell measurements.
• Characterized two highly concentrated sulfolane/LiFSI electrolytes.
• Compared results from sets of four and five experimental quantities.

Main Results:

• Methods using only four experimental quantities resulted in large uncertainties for either Onsager coefficients or the thermodynamic factor.
• Overdetermination with five experimental quantities provided acceptable uncertainties for all four target quantities.
• Analysis revealed insights into dynamic ion correlations and transport limitations.

Conclusions:

• Accurate determination of battery electrolyte transport properties necessitates overdetermined experimental data.
• Five experimental measurements are crucial for reliable quantification of Onsager coefficients and thermodynamic factors.
• This study highlights the importance of experimental design for understanding ion dynamics in advanced battery electrolytes.