Ionic polymer-metal composite (IPMC) as a flexible capacitor: a COMSOL Multiphysics study

This work investigates the behavior of ionic polymer-metal composite (IPMC) capacitors, which are promising for flexible energy storage applications due to the mechanical softness and stability in aqueous environments. A physics-based modeling framework was developed to reveal the inner workings of IPMC-based capacitors, comprising solid-state electrolytes, platinum electrodes, and coupled ion transport and electrostatic interactions. The model, implemented in COMSOL Multiphysics, was qualitatively validated by comparing simulated and experimental cyclic voltammetry (CV) curves, focusing on capturing capacitive behavior and the magnitude of the current values over the scanned voltage range. To explore the device performance characteristics, the effects of the voltage scan rate and the presence of microcracks in the electrodes on capacitor behavior were investigated using the model. Microcracks, which often result from fabrication processes or continuous bending, pose challenges in predicting device performance. Simulations showed that reducing the scan rate from 0.1 to 0.015 V/s increased the specific capacitance from approximately 0.9 to 2.9 mF/g. Additionally, the introduction of thousands of randomly distributed microcracks, based on experimentally observed densities, led to only a modest capacitance reduction (~4.5%), indicating that IPMC capacitors are tolerant to minor structural imperfections. These findings demonstrate the utility of the modeling framework in evaluating structural and operational factors that influence IPMC capacitor behavior. Unlike previous modeling studies focused on actuation and sensing, this work introduces a dedicated simulation framework for IPMC capacitor modeling, incorporating the effects of electrode microcracks to potentially support predictive design in flexible energy storage systems.