Additive-free MXene inks and direct printing of micro-supercapacitors

Abstract

Direct printing of functional inks is critical for applications in diverse areas including elec-trochemical energy storage, smart electronics and healthcare. However, the available prin-table ink formulations are far from ideal. Either surfactants/additives are typically involved orthe ink concentration is low, which add complexity to the manufacturing and compromisesthe printing resolution. Here, we demonstrate two types of two-dimensional titanium carbide(Ti3C2Tx) MXene inks, aqueous and organic in the absence of any additive or binary-solventsystems, for extrusion printing and inkjet printing, respectively. We show examples of all-MXene-printed structures, such as micro-supercapacitors, conductive tracks and ohmicresistors on untreated plastic and paper substrates, with high printing resolution and spatialuniformity. The volumetric capacitance and energy density of the all-MXene-printed micro-supercapacitors are orders of magnitude greater than existing inkjet/extrusion-printed activematerials. The versatile direct-ink-printing technique highlights the promise of additive-freeMXene inks for scalable fabrication of easy-to-integrate components of printable electronics.