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

Abstract

A family of 2D transition metal carbides and nitrides known as MXenes has received increasing attention since the discovery of Ti3C2 in 2011. To date, about 30 different MXenes with well‐defined structures and properties have been synthesized, and many more are theoretically predicted to exist. Due to the numerous assets including excellent mechanical properties, metallic conductivity, unique in‐plane anisotropic structure, tunable band gap, and so on, MXenes rapidly positioned themselves at the forefront of the 2D materials world and have found numerous promising applications. Particular interest is devoted to applications in electrochemical energy storage, whereby 2D MXenes work either as electrodes, additives, separators, or hosts. This review summarizes recent advances in the synthesis, fundamental properties and composites of MXene and highlights the state‐of‐the‐art electrochemical performance of MXene‐based electrodes/devices. The progresses in the field of supercapacitors and Li‐ion batteries, Li‐S batteries, Na‐ and other alkali metal ion batteries are reviewed, and current challenges and new opportunities for MXenes in this surging energy storage field are presented. In the focus of interest is the possibility to boost device‐level performance, particularly that of rechargeable batteries, which are of utmost importance in future energy technologies. Very recently, the 2019 Nobel Prize in Chemistry was awarded to the inventors of the Li‐ion battery. For sure, this will provide an additional stimulation to study fundamental aspects of electrochemical energy storage.

Ti3C2Tx MXene-Based Light-Responsive Hydrogel Composite for Bendable Bilayer Photoactuator

“…This makes the strip transition from a “C-shape” to an “I-shape,” followed by inverted “C-shape.” The contribution of MXene in the photothermal behavior of MXene/NIPAm is crucial, as the sample without MXene did not show any bending changes during the experiment. MXene is known for its high heat conductivity [ 52 ]. This increases the sensitivity/efficiency of the photothermal process.…”

The Recent Advances in the Mechanical Properties of Self-Standing Two-Dimensional MXene-Based Nanostructures: Deep Insights into the Supercapacitor

“…Meanwhile, the power delivery (P) can be calculated using this equation P = V 2 /4R, where R is the equivalent series resistance of the supercapacitor. Self-standing MXenes are among the most promising materials for supercapacitors due to their excellent electrical conductivity, mechanical flexibility, high surface area, and high capacitance [ 24 , 69 , 70 ]. Thereby, few reviews emphasized the utilization of MXenes as supercapacitors, which showed that self-standing Ti 3 C 2 T x is the most studied MXenes [ 71 , 72 , 73 ].…”

W2C/WS2 Alloy Nanoflowers as Anode Materials for Lithium-Ion Storage

“…The W 2 C/WS 2 _2h, W 2 C/WS 2 _4h, and W 2 C/WS 2 _12h NFs showed the charge and discharge capacities of 595.2 and 935.2 mAh g −1 , 751.8 and 1040.5 mAh g −1 , 717.7 and 953.5 mAh g −1 , respectively. It has been reported that carbide materials are promising candidates for energy storage applications [ 41 ]. In this study, the addition of W 2 C to the WS 2 NF sample improved its storage capacity.…”