科研之友
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摘要
A novel gel polymer, polyvinyl alcohol-orthophosphoric acid-2-mercaptopyridine (PVA-H3PO4-PySH), is prepared through introducing redox-mediated 2-mercaptopyridine into a polyvinyl alcohol-orthophosphoric acid host, and a solid state supercapacitor is fabricated using the gel polymer as an electrolyte and a separator and using activated carbons as electrodes. The PVA-H3PO4-PySH gel polymer was shown to have excellent stretching and bending properties. The electrochemical properties of the supercapacitor are investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Surprisingly, electrode specific capacitance (1128 F g(-1)) and energy density (39.17 W h kg(-1)) are increased by 447% by introducing PySH as the redox mediator in the PVA-H3PO4 gel polymer. The supercapacitor with the PVA-H3PO4-PySH gel polymer shows an excellent capacitance retention of 80% for over 1000 cycles. Simultaneously, the ionic conductivity of the gel polymer electrolyte increased by 92% up to 22.57 mS cm(-1) compared to that of the PVA-H3PO4 system. These improved performances are owed to the redox reaction between 2-mercaptopyridine (PySH) and 2,2'-bipyridine (PySSPy) redox couples in the PVA-H3PO4-PySH gel electrolyte, indicating the supercapacitor combines the double-layer characteristic of carbon-based supercapacitors and the faradaic reactions characteristic of batteries' energy-storage processes.
