A New Free-Standing Aqueous Zinc-Ion Capacitor Based on MnO₂-CNTs Cathode and MXene Anode

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Current energy storage devices face limitations: batteries have low power density, and supercapacitors have low energy density.
• Ion capacitors offer a potential solution by integrating battery-type and capacitor-type electrodes to achieve high energy and power densities.

Purpose of the Study:

• To design and realize a novel zinc-ion capacitor (ZIC) for enhanced energy storage performance.
• To address the safety concerns associated with organic electrolytes in traditional ion capacitors.

Main Methods:

• Assembled a ZIC using a free-standing manganese dioxide-carbon nanotubes (MnO2-CNTs) cathode and MXene (Ti3C2Tx) anode.
• Utilized an aqueous electrolyte for improved safety and performance.
• Evaluated electrochemical performance, including specific capacitance, energy density, power density, and cycling stability.

Main Results:

• The ZIC demonstrated a high specific capacitance of 115.1 F g−1 at 1 mV s−1.
• Achieved a high energy density of 98.6 Wh kg−1 at a power density of 77.5 W kg−1.
• Exhibited excellent power density of 2480.6 W kg−1 (at 29.7 Wh kg−1) and retained ~83.6% capacitance after 15,000 cycles.
• The ZIC also showed strong performance in an aqueous gel electrolyte.

Conclusions:

• The developed ZIC offers a promising strategy for next-generation high-performance energy storage devices.
• The use of aqueous electrolytes enhances safety compared to organic electrolytes.
• The combination of MnO2-CNTs and MXene electrodes provides a synergistic effect for superior electrochemical properties.