Hierarchically porous N-doped carbon nanosheet aerogel cathodes for Zn-ion hybrid supercapacitors with superhigh energy density

Carbon nanomaterials with large specific surface area and high electronic conductivity, have been widely used as capacitive cathode materials for Zn-ion hybrid supercapacitors. Doping of heteroatoms and regulation of pore structure are crucial for boosting the energy storage performances of the carbon-based cathodes. We propose a N-doped carbon nanosheet aerogel (N-CNAG) with high active N content and hierarchically porous structure, which can be prepared by the bubble-templated polymerization of Py and the carbonization of the PPy nanosheet hydrogel (PPyNHG). The high active N content of N-CNAG can produce high pseudocapacitance through the N-dependent electrochemical redox reactions. The hierarchically porous structure of N-CNAG can facilitate fast electrolyte ion diffusion. Based on the Zn anode and the N-CNAG cathode, the Zn-ion hybrid supercapacitor can provide a remarkable specific capacitance of 706 F g−1 at 1 A g−1 and the rate capability of 50 % from 1 A g−1 to 5 A g−1, mainly attributed to the high active N content and the hierarchically porous structure of N-CNAG. Additionally, this Zn-ion hybrid supercapacitor provides the superhigh energy density of 392 Wh kg−1 at 1 kW kg−1 and the cycling stability of 87.4 % after 10,000 cycles, holding great potential for developing high-energy-density Zn-ion hybrid supercapacitors.