Air-stable, high-performance, flexible microsupercapacitor with patterned ionogel electrolyte

We describe the fabrication of air-stable, high-performance, planar microsupercapacitors (MSCs) on a flexible poly(ethylene terephthalate) substrate with patterned ionogel electrolyte, i.e., poly(ethylene glycol) diacrylate/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and electrodes of spray-coated multiwalled carbon nanotubes. The flexible MSC showed good cyclability, retaining ∼80% of initial capacitance after 30000 cycles, and good mechanical stability down to a bending diameter of 3 mm under compressive stress; 95% of the initial capacitance was retained after 1000 bending cycles. The MSC had high electrochemical stability with retaining 90% of its initial capacitance for 8 weeks in air. Furthermore, vertical stacking of MSCs with patterned solid film of ionogel electrolyte could increase the areal capacitance dramatically. This flexible MSC has potential applications as an energy-storage device in micro/nanoelectronics, without encapsulation for air stability.