Versatile N-Doped MXene Ink for Printed Electrochemical Energy Storage Application

Printing is regarded as a revolutionary and feasible technique to guide the fabrication of versatile functional systems with designed architectures. 2D MXenes are nowadays attractive in printed energy storage devices. However, owing to the van der Waals interaction between the MXene layers, the restacking issues within the printed electrodes can significantly impede the ion/electrolyte transport and hence handicap the electrochemical performances. Herein, a melamine formaldehyde templating method is demonstrated to develop crumpled nitrogen-doped MXene (MXene-N) nanosheets. The nitrogen doping boosts the electrochemical performances of MXene via enhanced conductivity and redox activity. Accordingly, two types of MXene-N inks are prepared throughout the optimization of the ink viscosity to fit the 2D screen printing and 3D extrusion printing, respectively. As a result, the screen printed MXene-N microsupercapacitor delivers an areal capacitance of 70.1 mF cm−2 and outstanding mechanical robustness. Furthermore, the 3D-printed MXene-N based supercapacitor manifests an areal capacitance of 8.2 F cm−2 for a three-layered electrode and readily stores a high areal energy density of 0.42 mWh cm−2. The approach to harnessing such versatile MXene-N inks offers distinctive insights into the printed energy storage systems with high areal energy density and large scalability.