Hydrogel-stabilized zinc ion batteries: progress and outlook

Aqueous zinc-ion batteries (ZIBs) offer numerous advantages, such as high energy density, enhanced safety, and low cost, making them an ideal choice for energy storage and conversion applications in the "post-lithium" era. Hydrogel electrolytes, as the key component of flexible ZIBs, combine the ionic conductivity of traditional water electrolytes with the dimensional stability of solid polymer electrolytes. However, it remains a challenge to design comprehensive and appropriate hydrogel electrolytes to provide flexible ZIBs with good reversibility and versatility. This review discusses the engineering design of hydrogel electrolytes required for flexible ZIBs from the viewpoint of an electrolyte designer. The basic properties of the hydrogel electrolytes, zinc anodes, cathodes and electrolyte stabilization effects are described in detail. Furthermore, we explore the various challenges faced by hydrogel electrolytes and propose corresponding strategies. Finally, the review offers insights into the future development of hydrogel-stabilized ZIBs. We explored effective solutions for enhancing the operational stability of ZIBs by designing hydrogel electrolytes that protect zinc anodes, cathodes, and electrolytes.