Achieving thermally stable supercapacitors with a temperature responsive electrolyte
Thermally stable electrochemical devices are ideal due to their stabilized performance and longer service life at extreme temperatures. However, ageing in supercapacitors, which is caused by generation of heat induced by high voltage, current, temperature, and aided by temperature induced self-accelerating reactions, plague the performance and lead to shortened service life. Poly(N-isopropylacrylamide) (PNIPAM) has been one of the most studied temperature responsive polymers (TRPs) in the past decades; it has a lower critical solution temperature (LCST) around 32 °C. By integrating PNIPAM into aqueous electrolyte, it was found that once LCST is reached, the specific capacitance of supercapacitors is reduced, which is accredited to drag of ion migration and precipitated polymer chains reside upon electrode surface. The capacitance reduction is even more obvious when the electrolyte solute changed into large size solute potassium ferricyanide. In terms of specific capacitance, comparing to an increase of the control, the PNIPAM integrated systems experienced a decrease under 70 °C. The integration of TRPs into electrochemical systems offers alternative approach to suppress high temperature capacitive reactions and ageing, thus could guarantee longer service life, performance stabilized supercapacitors.
The authors would like to thank Ms. Kim Ivey for assistance with GPC measurement and the Department of Materials Science and Engineering and the Department of Chemical and Biomolecular Engineering of Clemson University for funding support.
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