3D Printing of Freestanding MXene Architectures for Current-Collector-Free Supercapacitors

Additive manufacturing (AM) technologies appear as a paradigm for scalable manufacture of electrochemical energy storage (EES) devices, where complex 3D architectures are typically required but are hard to achieve using conventional techniques. The combination of these technologies and innovative material formulations that maximize surface area accessibility and ion transport within electrodes while minimizing space are of growing interest. Herein, aqueous inks composed of atomically thin (1-3 nm) 2D Ti₃ C₂ T_x with large lateral size of about 8 µm possessing ideal viscoelastic properties are formulated for extrusion-based 3D printing of freestanding, high specific surface area architectures to determine the viability of manufacturing energy storage devices. The 3D-printed device achieves a high areal capacitance of 2.1 F cm^-2 at 1.7 mA cm^-2 and a gravimetric capacitance of 242.5 F g^-1 at 0.2 A g^-1 with a retention of above 90% capacitance for 10 000 cycles. It also exhibits a high energy density of 0.0244 mWh cm^-2 and a power density of 0.64 mW cm^-2 at 4.3 mA cm^-2 . It is anticipated that the sustainable printing and design approach developed in this work can be applied to fabricate high-performance bespoke multiscale and multidimensional architectures of functional and structural materials for integrated devices in various applications.