Atomic layer deposition encapsulated activated carbon electrodes for high voltage stable supercapacitors

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• High energy density supercapacitors require operating voltage enhancement.
• Activated carbon electrodes exhibit poor electrochemical stability above 2.5 V, limiting performance.
• Developing stable electrodes is crucial for advanced energy storage solutions.

Purpose of the Study:

• To enhance the electrochemical stability of activated carbon electrodes for high-voltage supercapacitors.
• To investigate the efficacy of atomic layer deposition (ALD) for surface modification of activated carbons.
• To improve the energy density and cycle life of supercapacitors operating at elevated voltages.

Main Methods:

• Conformal coating of a 2-nanometer-thick Al2O3 dielectric layer onto activated carbon surfaces using ALD.
• Electrochemical testing of ALD-modified activated carbon electrodes at 3 V operation.
• Accelerated cycle testing at 70 °C to evaluate long-term stability and capacitance retention.

Main Results:

• ALD encapsulation maintained the microporous morphology of activated carbon.
• Electrodes demonstrated excellent stability at 3 V, achieving a 39% energy density enhancement compared to 2.5 V operation.
• Protected electrodes retained 74% of initial voltage after 50 hours and 88% of capacitance after 5000 cycles, showing significant improvements over bare activated carbon.

Conclusions:

• ALD-based surface modification effectively enhances the electrochemical stability of activated carbon for high-voltage supercapacitors.
• The Al2O3 coating protects surface functional groups and reduces electrolyte degradation, leading to improved performance and longevity.
• This ALD approach provides a versatile strategy for improving the stability of carbon materials in various energy and environmental applications.