The strategic role of conducting polymers in zinc- and alkali-ion hybrid capacitors

The integration of mechanically resilient conducting polymers into zinc- and alkali-ion hybrid capacitors has attracted attention for sustainable, flexible, high-performance, energy storage systems. By exhibiting mixed ionic–electronic conductivity, controllable ion-polymer interactions, electric double-layer, pseudocapacitive, and battery-type behavior, conducting polymers can perform multifunctional roles in both cathodes and anodes, and are capable of supporting all three charge storage mechanisms. As cathodes, conducting polymers provide redox activity and enable versatile integration with carbon or metal oxide hybrids, enhancing both capacity and rate performance. As anodes, conducting polymers serve as ion-selective, conformal coatings that mitigate dendritic growth, buffer structural stress, and stabilize solid–electrolyte interphases. Recent developments in three-dimensional nanostructuring, ion-selective frameworks, and elastomeric composites for wearable applications, along with AI-guided materials discovery and sustainable materials integration, have established conducting polymers as indispensable building blocks for safe, sustainable, and high-performance hybrid capacitors for powering the next generation of electronics and energy storage systems. This Review discusses the use of conducting polymers as anodes and cathodes in zinc- and alkali-ion hybrid capacitors, including their ability to support charge storage mechanisms, as a sustainable way to improve performance of electronics and energy storage devices.