Overcoming the cyclic stability bottleneck of conducting polymer-based supercapacitors: From degradation mechanisms to practical solutions – A review

Conducting polymer-based supercapacitors have the potential to combine the high energy density of batteries with the high-power density of carbon-based electric double-layer capacitors. The primary limitation of these materials, however, is their poor cyclic stability, which restricts their widespread practical application. This review provides a critical and systematic analysis of degradation mechanisms in conducting polymer-based supercapacitors, with particular focus on polyaniline (PANI), polypyrrole (PPy), and poly(3,4-ethylenedioxythiophene) (PEDOT). It also critically evaluates state-of-the-art strategies to address this challenge. The three principal failure modes identified are: structural disintegration associated with osmotic expansion, electrochemical degradation due to overoxidation, and interfacial delamination. From this mechanistic perspective, we examine practical solution routes classified into four categories: (1) nanostructural engineering to accommodate volume changes, (2) formation of composites with carbon and two-dimensional materials, (3) optimization of redox-active electrolytes, and (4) covalent interfacial design. Each strategy is critically assessed regarding its advantages, limitations, scalability challenges, and technology readiness level. The review concludes with future perspectives, including the role of machine learning in material design, the development of self-regenerating supercapacitors, and the urgent need for standardized testing protocols. Degradation mitigation strategies are maturing, and the full potential of conducting polymer-based supercapacitors for future energy applications is now increasingly attainable.