Extremely stretchable, sticky and conductive double-network ionic hydrogel for ultra-stretchable and compressible supercapacitors

Stretchable and wearable electronic devices have attracted increasing attention for the realization of stretchable and compressible energy storage devices. To adapt to human body motion under rigorous and extreme working conditions, it is highly desirable to develop supercapacitors with remarkable capacitance retention during substantial stretching and compressing. Here, an intrinsically ultra-stretchable and compressible supercapacitor with remarkable capacitance retention is successfully constructed based on a new extremely stretchable, sticky and conducive double-network (DN) ionic hydrogel electrolyte. The hydrogel electrolyte with extreme stretchability ( > 18,000%), high toughness, good compression recovery performance, and conductivity (2.0 S/m) is achieved by introducing a chemically and physically crosslinked polyacrylamide-polyvinylpyrrolidone (PAAM-PVP) DN and LiCl electrolyte. In particular, the adhesive force of the hydrogel electrolyte surface is enhanced 13 times due to salting-out effect. A supercapacitor fabricated based on this DN hydrogel electrolyte exhibits superior intrinsic ultra-stretchability (2500% strain), the ability to withstand compressibility (up to 7100-times the weight of the supercapacitor), and a high specific capacity (308.9 F/g at a current density of 0.21 A/g). More importantly, the supercapacitor shows remarkable capacitance retention (87% at 2500% tensile strain, 90% at 7100-fold compressive weight). In addition, the wrinkled-structured all-solid supercapacitor maintained over 97% capacitance after being stretched to 200% for 6000 cycles, and maintained 104% capacitance after being compressed to 7100-times its own weight for 1000 cycles. This work provides new insights into the synthesis of ionic electrolyte and promotes the development of next-generation all-solid-state energy storage devices with high stretchability and compressibility.