Surface-Adaptive Capillarity Enabling Densified 3D Printing for Ultra-High Areal and Volumetric Energy Density Supercapacitors.

Endowing supercapacitors with higher energy density is of great practical significance but remains extremely challenging. In this work, an innovative densified 3D printing enabled by a surface-adaptive capillarity strategy is proposed for the first time. The printable ink formulated with pyrrole surface-modified reduced graphene oxide renders the printed electrodes excellent surface tension regulability to the subsequent capillary densification, creating an intensely condensed electrode with well-maintained structural integrity. Furthermore, simultaneous in situ nitrogen doping and hierarchical micro-meso porosity are readily realized upon post-carbonization, encouraging enhanced capacitance and fast reaction dynamics. As a result, the printed symmetric supercapacitor delivers a double leap in areal and volumetric energy densities in both aqueous and organic electrolytes, a rarely achieved yet gravely desired attribute for 3D printed energy storage devices.