Hierarchical polyimide-derived nitrogen self-doped carbon nanoflowers for large operating voltage aqueous supercapacitor

Herein, novel polyimide (PI) nanoflowers with intertwined nanosheets is synthesized by one-step hydrothermal "bottom-up" self-assembly crystal growing process by using low-cost aromatic diamine and dianhydride as monomers. Then, hierarchical polyimide-based porous carbon nanoflowers (PI-CNFs) are prepared by synchronous activation and catalytic carbonization approach utilizing polyimide as carbon precursor and FeCl 3 as activating agent and catalyst. Owing to its unique interlaced porous nanosheet structure, high specific surface area and high nitrogen doping content, the PI-CNFs possesses high specific capacitance, capacity rate performance and overlength cycle life. In addition, a novel symmetrical aqueous supercapacitor assembled with PI-CNFs has a large operating voltage of 2.0 V, a high specific energy of 18.3 Wh kg −1 at specific power of 500 W kg −1 , as well as excellent cycling stability. Therefore, this work will propose an affordable strategy for designing novel polymer nanosheets, and open up the possibility of easy preparation, environmentally friendly and low-cost synthetic polymers-based carbon nanosheets to meet the energy storage demands.