Mechanical reliable, NIR light-induced rapid self-healing hydrogel electrolyte towards flexible zinc-ion hybrid supercapacitors with low-temperature adaptability and long service life

Abstract

Hydrogel electrolytes hold great potential in flexible zinc ion supercapacitors (ZICs) due to their high conductivity, good safety, and flexibility. However, freezing of electrolytes at low temperature (subzero) leads to drastic reduction in ionic conductivity and mechanical properties that deteriorates the performance of flexible ZICs. Besides, the mechanical fracture during arbitrary deformations significantly prunes out the lifespan of the flexible device. Herein, a Zn2+ and Li+ co-doped, polypyrrole-dopamine decorated Sb2S3 incorporated, and polyvinyl alcohol/ poly(N-(2-hydroxyethyl) acrylamide) double-network hydrogel electrolyte is constructed with favorable mechanical reliability, anti-freezing, and self-healing ability. In addition, it delivers ultra-high ionic conductivity of 8.6 and 3.7 S m−1 at 20 and −30 °C, respectively, and displays excellent mechanical properties to withstand tensile stress of 1.85 MPa with tensile elongation of 760%, together with fracture energy of 5.14 MJ m−3. Notably, the fractured hydrogel electrolyte can recover itself after only 90 s of infrared illumination, while regaining 83% of its tensile strain and almost 100% of its ionic conductivity during −30–60 °C. Moreover, ZICs coupled with this hydrogel electrolyte not only show a wide voltage window (up to 2 V), but also provide high energy density of 230 Wh kg−1 at power density of 500 W kg−1 with a capacity retention of 86.7% after 20,000 cycles under 20 °C. Furthermore, the ZICs are able to retain excellent capacity even under various mechanical deformation at −30 °C. This contribution will open up new insights into design of advanced wearable flexible electronics with environmental adaptability and long-life span.