Two-dimensional (2D) transition metal carbides, and/or nitrides, so-called MXenes, have triggered intensive research interests in applications ranging from electrochemical energy storage to electronics devices. Producing these functional devices by printing necessitates to match the rheological properties of MXene dispersions to the requirements of various solution processing techniques. In particular, for additive manufacturing such as extrusion-printing, MXene inks with high solid fraction are typically required, which is commonly achieved by tediously removing excessive free water (top-down route). Here, the study reports on a bottom-up route to reach a highly concentrated binary MXene-water blend, so-called MXene dough, by controlling the water admixture to freeze-dried MXene flakes by exposure to water mist. The existence of a critical threshold of MXene solid content (≈60%), beyond which no dough is formed, or formed with compromised ductility is revealed. Such metallic MXene dough possesses high electrical conductivity, excellent oxidation stability, and can withstand a couple of months without apparent decay, providing that the MXene dough is properly stored at low-temperature with suppressed dehydration environment. Solution processing of the MXene dough into a micro-supercapacitor with gravimetric capacitance of 161.7 F g-1 is demonstrated. The impressive chemical and physical stability/redispersibility of MXene dough indicate its great promise in future commercialization.
Keywords: dough; extrusion printing; inks; micro-supercapacitors; transition metal carbides; two-dimensional MXene.
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