Zn-Ion Storage in an Anode-Protected High-Performance Aqueous Organic Zinc Ion Battery

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Organic materials offer potential for rechargeable batteries but face challenges in ion storage and stability.
• Naphthalenediimide (NDI) exhibits redox activity and ion-docking capabilities for Zn²⁺-ion storage.
• Anode degradation and sluggish ion kinetics are critical issues in developing advanced batteries.

Purpose of the Study:

• To investigate the complexities of Zn²⁺-ion storage in organic stacked layered naphthalenediimide (NDI).
• To elucidate the mechanisms behind capacity degradation during long-term cycling.
• To evaluate the efficacy of a zinc phthalocyanine (ZnPc) protective layer in enhancing battery performance.

Main Methods:

• Systematic experimentation and theoretical calculations were employed.
• Morphological and structural characterization of the NDI material.
• Electrochemical testing including cycling stability and coulombic efficiency measurements.

Main Results:

• NDI facilitates Zn²⁺ insertion/deinsertion and provides redox-active docking sites.
• Capacity fade was observed due to NDI structural transformation (hexagonal to flower-like) caused by co-insertion of Zn²⁺ and protons.
• The ZnPc layer effectively guided Zn²⁺ deposition, suppressed side reactions, and improved capacity retention and cycling stability (>99% coulombic efficiency).

Conclusions:

• Understanding phase transitions, ion diffusion, and zinc electrodeposition is crucial for designing organic Zn²⁺-ion hosts.
• The ZnPc protective layer is a promising strategy for stabilizing organic cathodes in aqueous zinc-ion batteries (AZIBs).
• This work provides a conceptual framework for developing next-generation organic electrode materials for AZIBs.