Interrogation of 2,2'-Bipyrimidines as Low-Potential Two-Electron Electrolytes

Area of Science:

• Electrochemistry
• Materials Science
• Renewable Energy Storage

Background:

• Growing demand for renewable energy necessitates advanced grid storage solutions.
• Redox flow batteries (RFBs) are critical for grid energy storage, with performance dependent on electrolyte properties.
• Nitrogen-containing heterocycles show promise for multielectron reduction at low potentials.

Purpose of the Study:

• Develop a novel electrolyte scaffold for RFBs based on 2,2'-bipyrimidine.
• Investigate structure-function relationships to optimize electrolyte performance and stability.
• Enhance energy density and cycling stability in RFBs.

Main Methods:

• Synthesis and electrochemical evaluation of 24 bipyrimidine anolytes.
• Computational analysis to determine structure-function relationships.
• Investigation of decomposition pathways and stability under operating conditions.

Main Results:

• Identified a 2,2'-bipyrimidine scaffold capable of two-electron storage at a low potential (∼-2.0 V vs Fc/Fc+).
• Discovered that steric hindrance disrupting planarity in the reduced state correlates with degradation.
• Determined the primary decomposition pathway to be solvent protonation of the dianion, reversible by oxidation.

Conclusions:

• Novel bipyrimidine electrolytes offer potential for high-energy-density RFBs.
• Minimizing steric hindrance in electrolyte design significantly improves stability.
• Understanding decomposition mechanisms is key to developing durable RFB systems.