High strength self-healable supercapacitor based on supramolecular polymer hydrogel with upper critical solubility temperature

Here, we report poly(N-acryloylglycinamide-co-vinyltriazole) p(NAGA-co-VTZ) supramolecular polymer hydrogel doped with activated polypyrrole nanotubes (acPPyNTs) as a high-strength self-healable material for supercapacitors. First, the p(NAGA-co-VTZ) hydrogel films were synthesized by photopolymerization of N-acryloylglycinamide and 1-vinyl-1,2,4-triazole without any cross-linkers. Scanning electron microscopy and mechanical tests showed that initial monomer concentration strongly affects both hydrogel microstructure and resulted mechanical properties. The hydrogels demonstrated self-healing ability through hydrogen bonding at the temperatures above upper critical solubility temperature, excellent mechanical properties (0.9 MPa), large stretchability (1300 %) and cut resistance. Next, as active material for electrochemical double layer capacitors (EDLC) carbonized and ethanol/KOH activated polypyrrole nanotubes (acPPyNTs) were prepared. Symmetric self-healable supercapacitor employing p(NAGA-co-VTZ) hydrogel, acPPyNTs and aqueous 3M KCl solution was assembled. Cyclic voltammetry, galvanostatic charge-discharge measurements showed that the prepared device gave a specific capacitance of 282.62 F g-1 at 0.2 A g-1 and high areal capacitance of 316.86 mF cm-2 at scan rate of 10 mV s-1. The supercapacitor operates over wide voltage window (0-1.2 V) and provides excellent cyclic performance with capacitance retention of 97 % after 10 000 cycles and 94 % after self-healing. Overall, the prepared self-healable supercapacitor appears to have considerable potential as high-performance energy storage device.