Research Progress on the Application of Electrically Conductive Hydrogel Electrodes in Flexible Energy Storage Systems

Electrically conductive hydrogels (ECHs) represent a novel class of hydrogels that combine conductive materials with a hydrogel matrix. They exhibit high electrical conductivity, excellent flexibility, and ease of structural modulation, thereby offering promising prospects in fields such as flexible supercapacitors and batteries. Various ECHs electrodes have been developed to date for the fabrication of flexible energy storage devices with outstanding mechanical and electrochemical performance. This review summarizes recent advancements in ECHs electrodes for flexible supercapacitors and batteries, discusses key factors for enhancing their performance in flexible energy storage applications, outlines the synergistic effects between the hydrogel matrix and electroactive fillers in ECHs electrodes, and systematically introduces flexible supercapacitors based on conductive polymer hydrogels, graphene hydrogels, and composite hydrogel electrodes. Additionally, it presents flexible lithium-ion batteries employing silicon-based hydrogels and transition metal oxide hydrogel electrodes. Finally, challenges and opportunities in the realm of ECHs electrodes in this field are explored.