Hydrogels Enable Smart Aqueous Batteries

The growing trend of intelligent devices ranging from wearables and soft robots to artificial intelligence has set a high demand for smart batteries. Hydrogels provide opportunities for smart aqueous batteries to self-adjust their functions according to the operating conditions. Despite the progress in hydrogel-based aqueous batteries, a gap remains between the designable functions of diverse hydrogels and the expected performance of batteries. In this chapter, we first briefly introduce the fundamentals of hydrogels, including formation, structure and characteristics of the internal water and ions. Batteries that operate under unusual mechanical and temperature conditions enabled by hydrogels are highlighted. Challenges and opportunities for further development of hydrogels are outlined to propose future research in smart batteries towards all-climate power sources and intelligent wearables.