Functionally integrated self-healable and redox bromide-ion additive hydrogel electrolyte for Zn-ion hybrid supercapacitors

Functional energy storage devices are usually dependent on functional hydrogel electrolytes, due to their high conductivity, flexibility and special functionality. However, the function of hydrogel electrolytes mostly depends on the functional groups of the polymer chain or their interaction with ions. The compatibility of function and electrochemical performance is the key to building a functional hydrogel electrolyte. In this study, a functionally integrated self-healable and redox bromide-ion additive hydrogel electrolyte (SAM-Zn) was synthesized based on a natural polymer backbone (sodium alginate aqueous solution), which exhibits outstanding self-healing ability and excellent mechanical properties. When SAM-Zn is assembled into Zn-ion hybrid supercapacitors (SAM-ZHS), which can achieve 219.4 mA h g⁻¹ at a wider voltage window (0–2.6 V), higher energy density of 210 Wh kg⁻¹ at 1914.6 W kg⁻¹. Besides, the self-healed SAM-ZHS displayed excellent cycling stability after 2,000 cycles with 96.8% capacity retention. This work provides a simple strategy for the combination of self-healing properties and excellent electrochemical properties in hydrogel electrolytes.