Clusters and Their Contributions to Ionic Conductivity in NaOTf-DME Electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Electrolytes are crucial for batteries and electrolytic cells.
• Understanding ion transport at the molecular level is key to optimizing electrolyte performance.
• Current models often lack detailed insights into cluster-specific conductivity contributions.

Purpose of the Study:

• To develop a framework for assessing the conductivity contributions of molecular clusters in electrolytes.
• To quantitatively determine the percentage contribution of charged clusters to overall electric conductivity.
• To provide insights into electrolyte behavior for advanced battery applications.

Main Methods:

• Identification and molarity calculation of clusters using excess infrared spectroscopy and density functional theory (DFT).
• Estimation of cluster self-diffusion coefficients via the Stokes-Einstein relation.
• Evaluation of charged cluster conductivities using the Nernst-Einstein equation.

Main Results:

• A model electrolyte system of sodium trifluoromethanesulfonate (NaOTf) and 1,2-dimethoxyethane (DME) was analyzed.
• Specific clusters like Na+(DME)3 and OTf-(DME)4 were identified and their conductivity contributions quantified.
• Na+(DME)3 dominates conductivity at low salt concentrations, while OTf-(DME)4 is dominant at high concentrations.
• Strong interactions were observed between DME and Na+, with weak interactions between DME and OTf-.

Conclusions:

• The study provides a quantitative method to assess cluster contributions to electrolyte conductivity.
• The findings offer crucial physical insights into ion transport mechanisms within electrolytes.
• This research can inform the design of novel electrolytes for high-performance batteries.