Laser cutting assisted fabrication of assembled solid-state supercapacitors based on polypyrrole coated paper

In this work, a simple process has been demonstrated to fabricate solid-state paper-based supercapacitors. A highly conductive paper was prepared through coating polypyrrole on cellulose paper by interfacial polymerization. Among the PPy/paper samples prepared using different Py concentrations of 0.5%, 1.0%, 2.0% and 2.5%, PPy/paper (1.0% Py) displayed the highest specific capacitance (247.4F/g at 0.01 V s⁻¹) and a good flexibility: the conductivity could retain near the original value even after being bent 450 times. Then, the PPy/paper (1.0% Py) electrodes with desired shapes were manufactured easily by laser cutting. A thin solid-state planar supercapacitor unit was fabricated by assembling the two PPy/paper electrodes and polyvinyl alcohol/H₃PO₄ electrolyte, and it exhibited a capacity of 51.6 mF and a high areal specific capacitance of 12.9 mF cm⁻². Furthermore, 8 supercapacitor units were connected in series and parallel to obtain a thin supercapacitor array generating a higher output voltage and capacity. The supercapacitor array was integrated with a flexible printed circuit board, and it lighted up 3 light-emitting diodes, even under bending conditions. This method can be used to scale up the fabrication of flexible integrated paper-based energy storage devices for various portable and wearable electronics.