Multiscale Pore Network Boosts Capacitance of Carbon Electrodes for Ultrafast Charging

Increasing charge storage capability during fast charging (at ultrahigh current densities) has been a long-standing challenge for supercapacitors. In this work, a novel porous carbon foam electrode with multiscale pore network is reported that achieves a remarkable gravimetric capacitance of 374.7 ± 7.7 F g^-1 at a current density of 1 A g^-1. More importantly, it retains 235.9 ± 7.5 F g^-1 (60% of its capacitance at 1 A g^-1) at an ultrahigh current density of 500 A g^-1. Electron microscopy studies reveal that this carbon structure contains multiscale pores assembled in a hierarchical pattern. The outstanding capacitive performance benefits from its extremely large surface area of 2905 m² g^-1, as around 88% of the electric charges are stored via electrical double layer. Significantly, electrochemical analyses show that the hierarchical porous structure containing macro-, meso-, and micropores allows efficient ion diffusion and charge transfer, resulting in the excellent rate capability. The findings pave the way for improving rate capability of supercapacitors and enhancing their capacitances at ultrahigh current densities.