Energy storage devices based on flexible and self-healable hydrogel electrolytes: Recent advances and future prospects

Hydrogel electrolytes (Hy-ELs) have distinct attributes such as softness and wetness, making them well-suited for producing flexible energy storage devices. In addition, the diverse and adaptable chemical compositions of hydrogels present possibilities for bestowing novel related capabilities, such as exceptional longevity, notable resilience to severe temperatures, sensitivity to stimuli, and the capacity for self-restoration. The abovementioned characteristics can be attained by manipulating polymer chains and chemical structures and advancing flexible energy storage devices with remarkable and fascinating capabilities. This paper extensively examines the design concepts related to flexible hydrogels and Hy-ELs and their significant ramifications in several scientific and industrial domains. The subject matter spans various facets, including polymer chemistry, synthesis procedures, properties, and adaptability demonstrations. The discourse also addressed relevant existing challenges and viewpoints and potential future trajectories for exploiting Hy-ELs in energy storage and other relevant sectors. Hydrophilic polymer networks exhibit a unique ability to retain significant quantities of water while maintaining properties similar to those of a solid substance. Hydrogels have extensive applications in diverse domains, including medicine, agriculture, and consumer products, demonstrating their exceptional versatility and compatibility with biological systems. The composition and categorization of hydrogels (natural and synthesized) were explored and discussed. Moreover, this research examines the mechanical properties and self-healing (SH) capabilities of Hy-ELs, with a particular focus on their utilization in energy storage technologies, such as supercapacitors (SUCPs) and batteries. Furthermore, the classifications of Hy-ELs and the methodologies utilized for their synthesis emphasizing their mechanical properties and intrinsic capacity for self-healability were presented.