Flexible Supercapacitors and Solid-State Electrolytes: A Perspective on the Key to Flexibility

Supercapacitors are a class of portable and sustainable energy storage devices with higher power and lower energy densities. Their commercial utility requires aqueous electrolytes, which hinder their flexibility, and hence, these devices may not find applications in wearable electronic devices. The evolution of polymers and solid-state electrolytes could solve flexibility issues with supercapacitors. The utility of different solid state and polymer electrolytes raises critical questions about stability, electrical conductivity, practical cyclability, and operational temperatures of the flexible devices. This Review discusses broad categories of solid-state electrolytes such as inorganic solid electrolytes, gel polymer electrolytes, and polyelectrolytes. The fabricated flexible solid-state supercapacitors’ electrochemical characterization and sustainable charge storage routines are discussed.