Flexible and Self-Healable Poly (N, N-dimethylacrylamide) Hydrogels for Supercapacitor Prototype

Abstract Flexible, and self-healable supercapacitors possess significant advantages over liquid electrolyte based supercapacitors. Liquid electrolytes are usually organic and not environmentally friendly. Therefore, flexible water-based electrolyte is a reliable choice. Water-based hydrogel electrolyte is a novel approach to overcome liquid electrolyte related drawbacks. In this study, we propose physically crosslinked poly (N, N-dimethylacrylamide) hydrogel using sodium montmorillonite as a crosslinking agent. The hydrogel electrolytes are prepared by adding different weight % (wt.%) of magnesium trifluoromethanesulfonate (MgOTf) salt as a source of ions. The synthesized hydrogel and hydrogel electrolytes are characterized via functional group identification, thermal decomposition, surface morphology, and elemental composition. Fourier transform infrared (FTIR) deconvolution and transference number measurement are conducted to confirm the complexation and ionic species. Based on the surface morphology, FTIR, and transference number measurement, it could be deduced that enhanced ionic conductivity is due to the amorphous nature of hydrogel electrolyte. Furthermore, an ionic conductivity study revealed that hydrogel electrolyte formulated by adding 30 wt.% salt (DMA3) attained maximum ionic conductivity of 6.69 × 10-3 S/cm. The electrochemical characterization of fabricated symmetric supercapacitor described that AC/DMA3/AC achieved the highest specific capacitance of 119 F/g at 3 mV/s and 142 F/g at 50 mA/g along with 98.07 % capacitance retention at 4 A/g after 5000 consecutive charge-discharge cycles. In addition, a flexible prototype supercapacitor device was designed using two symmetrical optimized AC/DMA3/AC cells connected in series, charged with external power supply, and lighted up the light-emitting diode (LED). The self-healability of the prototype was also examined. Results are very promising for the development of compact, self-standing, self-healable, highly flexible, lightweight, and biocompatible supercapacitors.