426615 Nanostructured Surfactant Ionic Liquids with Unusually High Capacitances for High-Temperature Flexible Supercapacitors

Tuesday, November 10, 2015: 1:20 PM
251F (Salt Palace Convention Center)
Xianwen Mao1, Paul Brown1, Margarida Costa Gomes2 and T. Alan Hatton1, (1)Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, (2)Chemical Engineering, MIT, Cambridge, MA

We report a new class of electrolytes, surfactant ionic liquids (SILs), that give rise to unprecedentedly high intrinsic areal capacitances (~100 to 200 µF/cm2), much larger than the values (~5 to 20 µF/cm2) of other known ionic liquids (ILs) based on smaller anions as well as commonly used aqueous/organic electrolytes. Such high capacitances can probably be attributed to an increased molecular structuring at the nanometer scale due to the presence of large non-polar alkyl chains and charged heads in these fluids. We demonstrate that extremely high gravimetric/volumetric capacitances can be achieved by combining SILs with proper porous electrodes with high surface areas. Due to the extremely wide potential working windows of ILs (~ 4 to 5 V), we show that the SIL-based devices exhibit ultrahigh energy densities. In addition, the SIL-based devices show an increasing capacitance with higher temperatures, which highlights another unique advantage of SILs, which is the suitability for operation at extremely high temperature (~200 oC), with myriad niche applications such as powering sensors and actuators for oil industry downhole operations (above 120 oC), electronics in hybrid electric vehicles (HEV, >60 oC), or military weapons and space equipment. Furthermore, we demonstrate that SILs can be easily polymerized to generate a quasi-solid yet flexible gel-like structure, as well as form seamless binding with current collectors/porous electrodes, for the development of next-generation solid-state highly flexible energy devices.

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