Harvesting micropower energy from the ambient environment requires an intermediate energy storage, for which printed aqueous supercapacitors are well suited due to their low cost and environmental friendliness. In this work, a systematic study of a large set of devices is used to investigate the effect of process variability and operating voltage on the performance and stability of screen printed aqueous supercapacitors. The current collectors and active layers are printed with graphite and activated carbon inks, respectively, and aqueous NaCl used as the electrolyte. The devices are characterized through galvanostatic discharge measurements for quantitative determination of capacitance and equivalent series resistance (ESR), as well as impedance spectroscopy for a detailed study of the factors contributing to ESR. The capacitances are 200–360 mF and the ESRs 7.9–12.7 Ω, depending on the layer thicknesses. The ESR is found to be dominated by the resistance of the graphite current collectors and is compatible with applications in low-power distributed electronics. The effects of different operating voltages on the capacitance, leakage and aging rate of the supercapacitors are tested, and 1.0 V found to be the optimal choice for using the devices in energy harvesting applications.

No abstract

No abstract

Gelatin offers a safe and sustainable alternative for gel electrolytes in printed supercapacitors. In this work, the performance of a non-toxic natural polymer electrolyte is studied in screen and stencil-printed supercapacitors. The basic electrical properties are determined with samples prepared on laboratory scale; subsequently, roll-to-roll printed samples are used to observe behavior of the samples under severe mechanical stress. With a 2 M NaCl gel electrolyte, electrical performance equal to that of a 1 M liquid electrolyte is reached, and the devices endure bending down to a 10 mm radius. Even below that, functional devices are successfully measured, although leakage current levels deteriorate somewhat during bending. However, even these samples recover to baseline levels after they are straightened and can be thus used in various applications, since devices with no short circuits or permanent degradation can be successfully prepared.

No abstract