Nanofoaming to boost electrochemical performance of three-dimensional compressible carbon monoliths for robust supercapacitors

Supercapacitors with excellent mechanical properties are urgently demanded. However, the most promising three-dimensional carbon materials electrodes for practical applications remain challenging due to their limited specific surface area, poor mechanical properties and the resulting inferior electrochemical performance. Here, nanofoaming strategy by one-step carbonization of ZnCl2-loaded commercial melamine foam was used to prepare three-dimensional carbon monoliths with nanobubbles (3D-CFN). Beneficial from the eliminated stress concentration points by the nanobubbles, 3D-CFN presents excellent compressible properties (no obvious fracture even though the strain up to 56%) and considerable specific surface area up to 535 m2 g−1. As a supercapacitor electrode, 3D-CFN maintains its original specific capacitance at the strain up to 83%, 91.4% at the bending angle of 180°, and 78.2% after 200 cyclic bending tests at the angle of 90°, respectively, demonstrating its excellent electrochemical stability under different force conditions. Moreover, the assembled 3D-CFN symmetric supercapacitor delivers a maximum energy density of 10.8 Wh kg−1 and a maximum power density of 25.6 kW kg−1. These results verify the applicability of nanofoaming in fabrication of flexible binder-free carbon foams and suggest 3D-CFN is a promising candidate for robust supercapacitors.