Redox-Mediated Poly(2-acrylamido-2-methyl-1-propanesulfonic acid)/Ammonium Molybdate Hydrogels for Highly Effective Flexible Supercapacitors

Flexible supercapacitors were constructed by using novel redox-mediated polymer electrolytes including poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and ammonium molybdate [(NH₄)₂MoO₄] (Mo). The gel polymer electrolytes PAMPS/Mo_x were prepared in different compositions, where x represents the doping ratio of Mo into PAMPS electrolyte. The structure and morphology of the electrolytes were elucidated by using various spectroscopic and microscopic methods, and then they were used in the fabrication of symmetric supercapacitors. The electrochemical performances of the devices were investigated by using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The system containing active carbon as the electrode and PAMPS/Mo₃ as the electrolyte produced a maximum specific capacitance of 530 F g⁻¹ with a 30 % enhancement in capacitance compared to the Mo-free supercapacitor. The energy density of the device is 73 Wh kg⁻¹ with a power density of 580 W kg⁻¹. The redox-active hydrogel-based supercapacitor exhibited an excellent performance even after 2500 charge-discharge cycles, maintaining 92 % of its original capacitance. A flexible supercapacitor was assembled by using PAMPS/Mo₃ electrolyte and successfully operated a light-emitting diode (LED).