Highly stable flexible supercapacitors enabled by dual-network polyampholyte hydrogel without additional electrolyte additives

Abstract

High-performance dual-network polyampholyte hydrogel is designed for flexible supercapacitors with remarkable mechanical stability and thermal and cycling stability. The dual-network hydrogel is produced through physical and chemical cross-linking between the random copolymer of the monomers containing Na+ and Cl- ions and high-viscosity xanthan gum. It shows high ionic conductivity (38.84 mS cm−1), low activation energy (0.089 eV), satisfactory mechanical properties, fire-resistant, and sturdy contact with electrodes. In addition, the self-containing mobile ions inside the hydrogel electrolyte without extra electrolyte additives help to significantly reduce the concentration polarization. Accordingly, the quasi-solid supercapacitor based on active carbon delivers super mechanical and thermal stability with no significant capacitance reduction after various deformations, compressing, and different temperatures. Besides, it delivers high specific capacitance of 110F g−1 at 0.5 A/g with 87.6 % retention after 10,000 cycles, showing maximum energy density and power density of 33.1 Wh kg−1 and 200.1 W kg−1. Notably, high capacitance retention (84.2 %) can be maintained after 7500 cycles even at 50 ℃. Therefore, this work provides a promising strategy to produce a kind of multifunctional hydrogel electrolyte for highly stable and durable next-generation flexible energy storage devices.