A Simple Strategy for Constructing Hierarchical Composite Electrodes of PPy‐Posttreated 3D‐Printed Carbon Aerogel with Ultrahigh Areal Capacitance over 8000 mF cm–2

Abstract A well‐designed pore structure and optimized interface will improve specific capacitances of carbon‐based supercapacitor electrodes significantly. Herein, a simple strategy is used to prepare the hierarchically porous 3D‐printed carbon aerogel (CA) electrodes via combining direct ink writing, freezing drying, carbonization, and polypyrrole (PPy) posttreatment. The 3D‐printed CA electrodes without PPy present a quasi‐proportional increase in areal capacitance as thickness, achieving an extremely high areal capacitance of 6875 mF cm –2 under a thickness of 2.2 mm. Additionally, PPy posttreated 3D‐printed CA (PPy@CA) electrode has improved wettability and contact conductivity, which shows a further significant increase of areal capacitance to 8126 mF cm –2 . After 10 000 continuous cycles, the PPy@CA electrode exhibits an excellent cyclic stability similar to that of 3D‐printed CA electrode by maintaining 91% of its original capacitance. This simple strategy may provide a novel insight to dramatically boost the energy storage properties of supercapacitor electrodes and their functionalization.