Redox-Active Phenanthrenequinone Triangles in Aqueous Rechargeable Zinc Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous rechargeable zinc batteries (ZBs) are promising for large-scale energy storage due to their safety, cost, and rate performance.
• Quinone compounds are attractive cathode materials for ZBs, offering high capacity, sustainability, and low cost.
• Dissolution of quinone-based cathodes during cycling limits battery lifespan.

Purpose of the Study:

• To develop a stable and high-performance cathode material for aqueous rechargeable zinc batteries.
• To overcome the dissolution issue of traditional quinone cathodes.
• To investigate the mechanism of improved performance in novel organic macrocycle cathodes.

Main Methods:

• Synthesis and characterization of a redox-active triangular phenanthrenequinone-based macrocycle (PQ-Δ).
• Electrochemical testing of PQ-Δ as a cathode material in aqueous ZBs.
• Density functional theory (DFT) calculations to elucidate the mechanism of interfacial resistance reduction.

Main Results:

• The PQ-Δ cathode demonstrated insertion of Zn²⁺ ions and H₂O molecules, effectively decreasing interfacial resistance.
• DFT calculations revealed that hydrated Zn²⁺ ion insertion lowers the desolvation energy penalty.
• The PQ-Δ cathode achieved a high reversible capacity (210 mAh g⁻¹) and excellent cycle stability (99.9% retention after 500 cycles).

Conclusions:

• The rigid triangular structure and hydrated ion insertion in PQ-Δ significantly enhance electrochemical performance.
• Low interfacial resistance, achieved through solvation of divalent ions, is crucial for divalent battery systems.
• Electron-active organic macrocycles represent a viable strategy for developing advanced cathode materials for ZBs.