Microscopic Model for Cyclic Voltammetry of Porous Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Cyclic voltammetry (CV) is crucial for characterizing electrochemical devices like supercapacitors.
• A quantitative link between CV measurements and the microscopic properties of supercapacitors is currently lacking.
• Understanding this relationship is key to optimizing supercapacitor performance.

Purpose of the Study:

• To establish a quantitative relationship between cyclic voltammetry and the microscopic properties of supercapacitors.
• To develop a predictive model for cyclic voltammetry based on fundamental physical parameters.
• To investigate the influence of pore size distribution on charging dynamics.

Main Methods:

• Utilized the microscopic "stack-electrode" model and its equivalent circuit representation.
• Simulated electric double-layer formation in porous electrodes.
• Analyzed the governing dimensionless parameter ωτ_{n} (scan frequency × relaxation timescale).

Main Results:

• The dimensionless parameter ωτ_{n} dictates CV curves and capacitance behavior.
• Capacitance remains scan-rate independent for ωτ_{n}≪1 and becomes scan-rate dependent for ωτ_{n}≫1.
• The model accurately reproduces experimental CV curves across a wide range of scan frequencies (ω) with a single fit parameter.

Conclusions:

• The developed model provides a quantitative bridge between CV and microscopic properties of supercapacitors.
• The findings offer insights into scan-rate dependency and the role of pore size distribution in charging dynamics.
• This work facilitates more accurate characterization and design of supercapacitors.