MXenes for Rechargeable Batteries Beyond the Lithium‐Ion

Abstract

past few decades. [2] In spite of the great success of the LIBs in consumer electronics and electric vehicles, their gridscale implementation is hindered by the limited lithium resources (only 20 ppm in the earth's crust) as well as the safety concerns. [3] In this regard, many other EES systems based on more abundant and less active elements, such as sodium (2.3%), potassium (2.1%), magnesium (2.3%), aluminum (8.2%), and zinc (75 ppm), have been developed and have already achieved significant progress. [1d,4] Historically, 2D layered materials have been employed as electrodes for batteries (e.g., graphite, [5] LiCoO 2 , [6] and TiS 2 [7]). Since the discovery of monolayer graphene in 2004, [8] more and more emerging 2D materials have quickly become popular electrode materials for various EES devices. This is not surprising given the unique structure and property of 2D materials. Their relatively large interlayer space allows fast ion (de)intercalation, whereas the highly anisotropic 2D structure enables fast charge transfer. Recently, a new class of 2D transition metal carbides, nitrides, and carbonitrides, known as MXenes, [9] was discovered and has attracted increasing research interest. Up to date, more than 30 MXenes have been successfully synthesized. [10] Similar to other 2D layered materials, MXenes also possess large/tunable interlayer spaces and high aspect ratios. In addition, MXenes show excellent hydrophilicity (contact angle is ≈21.5°-35°) [11] and extraordinary conductivity (e.g., ≈9880 S cm −1 for Ti 3 C 2 T x , 3250 ± 100 S cm −1 for V 2 CT x). [12] Further, MXenes are coupled with various terminations (e.g., OH, O, and F), which endow rich surface chemistries. These unique properties make them appealing in various applications, especially for energy storage devices such as batteries and supercapacitors. [1d,4i,13] We noted that there have already been several excellent reviews on the application of MXenes for energy storage and conversion, which cover a wide range of topics including for LIBs, supercapacitors, electrocatalysis, photocatalysis, electromagnetic interference, and so on. [10a,14] However, a more specific summary focuses on the rechargeable batteries is required and beneficial for the researchers working on nextgeneration batteries. Moreover, the study and investigation on MXenes for other EES systems beyond LIB are rapidly developing and have achieved great progress very recently. For example, great research efforts have been invested in exploring the application of MXenes in Li-sulfur batteries Research on next-generation battery technologies (beyond Li-ion batteries, or LIBs) has been accelerating over the past few years. A key challenge for these emerging batteries has been the lack of suitable electrode materials, which severely limits their further developments. MXenes, a new class of 2D transition metal carbides, carbonitrides, and nitrides, are proposed as electrode materials for these emerging batteries due to several desirable attributes. These attributes include large a...

Electrochemical Zinc Ion Capacitors: Fundamentals, Materials, and Systems

“…Electrolytes with small‐size anions, such as BF 4 − and DCA − , [ 165 ] are preferred in graphite‐based ZICs. On the other hand, new capacitive cathode materials, such as various MXenes, [ 241 ] phosphorus‐based materials, [ 242 ] and transition metal nitrides, [ 79 ] can be applied to the high‐performance ZICs. In situ analysis can be used to address the capacity fading mechanisms of redox materials, such as in situ Raman, NMR, and TEM techniques.…”

Covalent Assembly of Two‐Dimensional COF‐on‐MXene Heterostructures Enables Fast Charging Lithium Hosts

“…As an emerging 2D material, MXenes are being actively studied as desired precursors for constructing extended architectures. [16][17][18][19] Unlike other 2D materials, such as graphene and transition metal dichalcogenides, MXene nanosheets with the combined properties of excellent electronic conductivity and abundant terminal groups (e.g., hydroxyl groups) can enable the generation of versatile MXene-based hybrids via electrostatic absorption or intercalation, which is important for alleviating MXene self-restacking and enhancing compound electrical conductivity. [20,21] Based on this, CNTs, [21][22][23] polymers, [24] and metalbased particles [17,[25][26][27] have been combined with MXenes for various electrochemical energy storage applications.…”

Strategies for Fabricating High‐Performance Electrochemical Energy‐Storage Devices by MXenes

“…species are being added to this list. [20] The current studies focus on the synthesis of new MXenes as well as novel procedures for discovered species and their corresponding derivatives. [21] The preparation procedures of MXenes are categorised into two major groups, a) top-down strategies from MAX phases or non-MAX precursors (as shown in Figure 1 (b)), and b) bottom-up methods which form thin films of MXenes based on the atomic building blocks.…”

“…Lastly, it is possible to achieve a reasonable rate performance for the device at high sulphur loading because of the facilitated electron transport caused by the metallic nature of MXenes. [20,133] MXenes for Aqueous-Based Supercapacitors: The chemical composition as well as the structural properties of MXenes can influence the electrochemical energy storage performance (pseudocapacitive as well as electric double layer behaviour) of MXenes dramatically. As an example, oxygen-containing groups on Ti 3 C 2 T x MXenes can interact with the intercalated protons in sulfuric acid, showing a strong pseudocapacitive nature during the operation.…”

“…Figure20. TEM images of (a) Ti 3 C 2 and (b) pillar-free anatase TiO 2 /Ti 3 C 2 illustrating the expanded interlayer distance from 1.01 to 1.30 nm [206].…”