Hydrogels for Flexible/Wearable Batteries

Abstract

With the rapid development of society, wearable electronic devices have attracted widespread attention. In order to meet the requirements of wearable electronic devices for energy storage devices, they must have the characteristics of bending, stretching, and even twisting. Batteries and supercapacitors are the two mainstream commercial energy storage devices currently on the market, which are the most potential energy storage devices that can be used in wearable electronic products. However, conventional batteries and supercapacitors are not flexible due to device design constraints. Therefore, in order to realize the characteristic of flexibility, it is necessary to innovate the structure and material design of energy storage devices. It is worth noting that hydrogel is considered an ideal framework for constructing flexible energy storage devices, which is mainly attributed to the unique properties of hydrogels and the electrical properties of conductive materials. Specifically, hydrogel not only has a three-dimensional continuous conductive network structure to provide more active sites for electrochemical reactions but also the material is flexible to accommodate large mechanical deformations. In recent years, hydrogels have been designed with various micro-nano structures and used in flexible batteries to exhibit excellent electrochemical properties. In this chapter, we describe the types and properties of hydrogels and summarize the material design and synthesis methods. Then, the research progress of hydrogel in flexible batteries is introduced. Finally, challenges and opportunities in this field are discussed.