Durable Zn-ion hybrid capacitors using 3D printed carbon composites

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable Zn-ion hybrid capacitors (ZHCs) are promising for energy storage due to safety and material abundance.
• Practical ZHC application is limited by Zn anode dendrite growth, corrosion, and low cathode mass loading.

Purpose of the Study:

• To enhance ZHC capacity and durability using a hybrid-ion electrolyte and a 3D printed graphene-carbon nanotube (Gr-C) cathode.
• To investigate the effects of the hybrid electrolyte on Zn anode plating/stripping behavior.
• To explore the performance benefits of 3D Gr-C composite electrodes.

Main Methods:

• Fabrication of ZHCs with a hybrid electrolyte (NaCl and ZnSO4) and 3D printed Gr-C cathodes.
• Electrochemical characterization including capacity, cycling stability, and rate performance measurements.
• In situ electrochemical and ex situ ToF-SIMs analysis to study Zn anode behavior.

Main Results:

• The hybrid electrolyte demonstrated higher ionic conductivity and lower pH, promoting uniform Zn plating/stripping.
• 3D Gr-C electrodes exhibited enhanced ion accessibility and dual-ion charge storage.
• The optimized ZHC achieved a maximum capacity of 0.84 mA h cm⁻² at 3 mA cm⁻² with 78.7% capacity retention at 20 mA cm⁻² after cycling.
• Compared to pristine electrolyte ZHCs, the hybrid system showed significantly improved capacity (0.72 mA h cm⁻²) and cycle life (14.8% retention).

Conclusions:

• The synergistic combination of a hybrid-ion electrolyte and 3D Gr-C cathode significantly enhances ZHC performance.
• The developed ZHCs are dendrite-free and exhibit superior durability, addressing key limitations in Zn-ion hybrid capacitor technology.
• This work provides a pathway for developing highly durable and high-performance 3D energy storage devices.