Supra-3‑V Nonaqueous Redox-Flow Batteries Based on Simple Terephthalonitrile Anolytes

Area of Science:

• Materials Science
• Electrochemistry
• Organic Chemistry

Background:

• Designing organic molecules for nonaqueous redox-flow batteries requires balancing redox potential, solubility, and stability.
• High synthetic complexity often hinders the practical, large-scale application of these materials.

Purpose of the Study:

• To investigate alkyl-substituted terephthalonitriles as potential anolytes for redox-flow batteries.
• To assess the impact of alkyl substitution on the stability and performance of terephthalonitrile-based anolytes.

Main Methods:

• Synthesis of alkyl-substituted terephthalonitriles.
• Electrochemical testing of redox-flow batteries using these anolytes.
• Density functional theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• 2,5-dialkylterephthalonitriles demonstrated improved stability compared to mono-substituted derivatives.
• Flow batteries utilizing these anolytes achieved over 3 V with excellent capacity retention (>99.8% cycle⁻¹).
• Energy efficiencies reached up to 77% at 40 mA cm⁻², outperforming many benzene-based anolytes.

Conclusions:

• 2,5-dialkylterephthalonitriles present a promising, synthetically accessible class of anolytes for nonaqueous redox-flow batteries.
• Further enhancements in solubility and long-term stability are necessary for practical, large-scale implementation.