Manipulating Aggregate Electrochemistry for High-Performance Organic Redox Flow Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Organic Chemistry

Background:

• Organic molecules are key energy storage units in organic redox flow batteries (ORFBs).
• The aggregation of these molecules in solution is critical but understudied.
• Understanding and controlling aggregation is vital for optimizing ORFB performance.

Purpose of the Study:

• To investigate the aggregation of organic molecules in ORFBs at the molecular level.
• To explore molecular engineering strategies for manipulating and counteracting aggregation.
• To establish a link between molecular aggregation and battery performance metrics.

Main Methods:

• Development of a pyridinium molecular library.
• Utilizing theoretical calculations and physiochemical methods for characterization.
• Analyzing the impact of aggregation on molecular energy levels and thermodynamic potential.

Main Results:

• Singly-reduced monoradicals aggregate in concentrated solutions due to solvation, orbital overlap, and dispersion.
• Aggregation can be controlled via molecular engineering, electrostatic repulsion, or twisted geometries.
• Monoradical aggregation lowers energy levels and linearly scales with thermodynamic potential, reducing battery voltage.

Conclusions:

• Molecular aggregation in ORFBs negatively impacts energy density by lowering voltage.
• Anti-aggregation strategies effectively break the scaling relationship between molecular properties and performance.
• This research offers insights into electrolyte behavior and provides a chemical strategy for enhancing flow battery design.