Mask-painting symmetrical micro-supercapacitors based on scalable, pore size adjustable, N-doped hierarchical porous carbon

High specific surface area carbons with a hierarchical porous structure and outstanding conductivity have gained tremendous attention for energy storage applications due to their stable electrochemical properties and high rate capability. However, high specific surface areas are always generated from a high content of micropores. Scalable syntheses of porous carbons with ultrahigh specific surface area as well as a high content of macropores and mesopores still remain a great challenge. Herein, N-doped hierarchical porous carbon with an ultrahigh specific surface area of 2315 m2 g−1 together with high contents of macropores and mesopores was synthesized from poly(acrylonitrile) (PAN) by using a rationally designed, stepwise pore-forming process. After mixing with a small amount of carbon nanotubes, excellent electrochemical properties, including a high specific capacitance (286.8 F g−1), outstanding rate capability and cycling stability (97.2% after 20 000 cycles), were obtained. An interdigitated symmetric micro-supercapacitor (MSC) prepared by a simple mask-painting method exhibits high areal capacitance up to 36.5 mF cm−2 at a current density of 0.25 mA cm−2 and a high energy density of 5.07 μW h cm−2 at a power density of 0.25 mW cm−2. Furthermore, symmetrical MSCs display excellent rate capability, outstanding cycling stability (98.2% after 10 000 cycles) and remarkable bending stability (81.3% after 500 bending cycles at a 180° bending angle). Additionally, the areal capacitance and output voltage of the symmetrical MSCs can be easily adjusted using tandem or shunt models representing practical applications.