ABSTRACT
Hydrogels are a special class of porous materials with structures and properties that can be defined and designed through the fabrication process. This is the most important characteristic of these porous materials that makes them great candidates for the design of high-performance energy storage, conversion, and generation systems. Tunable mechanical properties, structural stability, large available surface area with a large number of active sites for reaction and deposition, and the designable number of electron transport pathways to facilitate the diffusion of electrons and ions are the main structural properties of hydrogels in energy storage/harvesting applications. In this chapter, various synthesis strategies reported for the fabrication of hydrogels are overviewed. Moreover, different types of hydrogels that can be prepared from different types of precursors including carbonous materials, polymers, and inorganic precursors are covered. These hydrogel materials have been successfully used as electrodes, electrolytes, current collectors, 3D junction systems, etc. in various types of energy-related applications such as lithium-ion batteries, supercapacitors, catalysts, and fuel cells. Based on the unique properties of hydrogels such as flexibility, elasticity, and compatibility with different application environments, different types of new energy storage, harvesting, and conversion devices can be developed. Considering the high performance of hydrogels in different energy-related areas, the applications of energy devices based on these materials can be extended to other areas of technology.
