Advanced MXene/Graphene Oxide/Lignosulfonate Inks for 3D Printing Thick Electrodes with Vertically Aligned Pores to Dually Boost Mass Loading and Areal Capacitance

Abstract Direct ink writing 3D printing, using ink extrusion, promises to transform conventional 2D thin electrodes into 3D thick architectures for high‐performance supercapacitors. However, formulating 3D printing inks and designing 3D architectures for electrodes remain challenges. In this work, a novel MXene/graphene oxide/lignosulfonate (MGL) ink with excellent rheological properties is developed for 3D printing MGL thick electrodes with vertically aligned architectures. The MGL ink exhibited excellent shear‐thinning properties for smooth 3D printing and shape retention after printing. The 3D‐printed MGL thick electrode, with a thickness of up to 4 mm, achieved a breakthrough mass loading of 72.1 mg cm − 2 , resulting in an extremely high areal capacitance of 8.6 F cm − 2 that is 9.6 times greater than the value observed for the bulk MGL electrode (0.9 F cm − 2 ). Additionally, supercapacitors using the 3D MGL electrode achieved an energy density of 505.3 µWh cm − 2 , significantly surpassing the value for bulk MGL electrode (52.8 µWh cm − 2 ). This enhancement is attributed to the efficient design of the electrodes, where vertically aligned pores in the 3D MGL electrode enhanced ion transfer and reaction kinetics. This study demonstrates an innovative approach for formulating inks and provides guidance for designing 3D thick electrodes with rapid ion transport and excellent electrochemical performance.