High-performance asymmetric supercapacitor based on graphene hydrogel and nanostructured MnO2

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Supercapacitors are crucial for energy storage applications.
• Developing high-performance supercapacitors requires novel electrode materials and device architectures.
• Graphene hydrogel and manganese dioxide nanostructures show promise for supercapacitor electrodes.

Purpose of the Study:

• To fabricate and characterize an asymmetric supercapacitor with enhanced energy and power densities.
• To utilize graphene hydrogel (GH) as a negative electrode and MnO(2) nanoplates on nickel foam (MnO(2)-NF) as a positive electrode.
• To evaluate the electrochemical performance of the asymmetric supercapacitor in a neutral aqueous electrolyte.

Main Methods:

• Fabrication of an asymmetric supercapacitor using GH and MnO(2)-NF electrodes.
• Electrochemical characterization including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
• Performance evaluation in a neutral aqueous Na(2)SO(4) electrolyte over a wide potential window.

Main Results:

• The asymmetric supercapacitor achieved an energy density of 23.2 Wh kg(-1) at a power density of 1.0 kW kg(-1).
• The device operated stably over a wide potential window of 0-2.0 V with 83.4% capacitance retention after 5000 cycles.
• Significantly improved energy density compared to symmetric supercapacitors based on GH (5.5 Wh kg(-1)) and MnO(2)-NF (6.7 Wh kg(-1)).

Conclusions:

• The developed asymmetric supercapacitor demonstrates high energy and power densities, making it suitable for advanced energy storage.
• The complementary electrode design and optimized materials contribute to the superior performance and stability.
• This work presents a promising strategy for designing high-performance supercapacitors using earth-abundant materials.