Recent advances in flexible/stretchable hydrogel electrolytes in energy storage devices

Due to global concerns about environmental and energy challenges, there has been a surge in exploring compatible power sources supporting devices, including flexible rechargeable batteries, other wearable electronic devices, and solar cells. The present study is based on a detailed review of hydrogel electrolytes which are found as excellent candidates for power devices and supercapacitors with their unique features of being wet and soft, thus, making them flexible. Due to water retention in interstitial spaces within hydrogels, dissolved mobile electrolyte ions exist to support electrochemical reactions. The classification of hydrogels is presented in detail. Herein, the state-of-art advances in hydrogel materials for flexible energy storage devices including supercapacitors and rechargeable batteries, solar cells, and artificial skins are reviewed.