Mixed-Phase MnO₂/N-Containing Graphene Composites Applied as Electrode Active Materials for Flexible Asymmetric...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Flexible solid-state asymmetric supercapacitors require advanced electrode materials for improved energy and power densities.
• Manganese dioxide (MnO₂) and graphene-based materials are promising candidates due to their electrochemical properties.

Purpose of the Study:

• To fabricate and characterize MnO₂/N-containing graphene composites for flexible solid-state asymmetric supercapacitors.
• To investigate the synergistic effects of MnO₂ and N-containing graphene on electrochemical performance.
• To optimize the Mn content and mass loading for superior supercapacitor performance.

Main Methods:

• Fabrication of MnO₂/N-containing graphene composites with varying Mn content.
• Material characterization using SEM, TEM, EDS, XPS, FTIR, and Raman spectroscopy.
• Electrochemical performance evaluation including cyclic voltammetry (CV) and impedance spectroscopy.

Main Results:

• The composites exhibited mixed α- and γ-phase MnO₂ nanostructures decorated on N-containing graphene.
• N-containing graphene effectively reduced charge transfer impedance (R_CT) and improved conductivity.
• Optimized 3-NGM1 electrode achieved a high specific capacitance of 638 F·g^-1, with energy density of 372.7 Wh·kg^-1 and power density of 4731.1 W·kg^-1.
• Excess Mn content led to increased R_CT and suppressed ionic diffusion, highlighting the importance of optimization.

Conclusions:

• The synergistic effect between mixed-phase MnO₂ and N-containing graphene significantly enhances supercapacitor performance.
• These composites are promising active materials for flexible solid-state asymmetric supercapacitors.
• Pseudocapacitive MnO₂ contributes more significantly to specific capacitance enhancement than N-containing graphene.