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

Abstract

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.

3D‐Printed Structure Boosts the Kinetics and Intrinsic Capacitance of Pseudocapacitive Graphene Aerogels

“…It offers great flexibility in the material (ink) selection and has been recently applied to prepare electrodes for electrochemical energy storage devices, including lithium‐ion batteries, sodium‐ion batteries, lithium–sulfur batteries, lithium metal batteries, and supercapacitors . In comparison to bulk electrodes, these 3D‐printed electrodes have shown improved electrolyte infiltration and ion diffusion …”

Two‐Dimensional Transition Metal Carbides and Nitrides (MXenes): Synthesis, Properties, and Electrochemical Energy Storage Applications

“…It is also reported that nitrogen doping is beneficial to enhance the electrical conductivity. Yu et al similarly used melamine as the nitrogen source to realize the crumpled nitrogen‐doped Ti 3 C 2 T x , which showcased a high areal capacitance (70.1 mF cm −2 ) coupled with improved cycling performance, demonstrating a great potential for the heteroatom doping in achieving advanced MXene‐based supercapacitors with high charge storage properties.…”

MXene-based 3D porous macrostructures for electrochemical energy storage

“…Although Akuzum et al study provides insights into the processability of MXenes, the development of printing procedures and ink formulations are still at the early stages; mostly producing flat re-stacked films or single printed layer arrays using techniques such as painting, writing [88], stamping [89], screen printing [90,91] and extrusion [92] and hence not fully utilizing the potentialities of printing in threedimensions. Only recently Yang et al demonstrated for the first time the possibility to print 3D MXene freestanding objects by designing inks composed solely of large, high aspect ratio MXene flakes (8 μm average lateral size and 1-3 layers) and water [93].…”

“…Later, Yu et al designed crumpled N-doped MXene (MXene-N) composite inks for printable electrochemical energy storage devices [91]. By mixing MXene-N with carbon nanotubes (CNT), activated carbon (AC) and GO, they were also able to produce a highly viscous, binder-free hybrid ink with ideal shearthinning features for extrusion printing with controlled thickness.…”

“…Porous Ti 3 C 2 T x assembled with bacterial cellulose (mass loading of 5 mg cm −2 ) showed high gravimetric and areal capacitances (416 F g −1 and 2.084 mF cm −2 , respectively at 3 mA cm −2 with 5 mg cm −2 mass loading) and excellent mechanical strength, even at high deformation [101]. Meanwhile, some promising reports have started to pave the way for MXene based 3D printed electrodes [91,93]. For example, freeze-dried extrusion printed Ti 3 C 2 T x electrodes (8.5 mg cm −2 mass loading) presented an areal capacitance of 2100 mF cm −2 with 242 F g −1 gravimetric capacitance at 1.7 mA cm −2 [93].…”