Recent progress in MXene layers materials for supercapacitors: High‐performance electrodes

Abstract

In 2011, Gogotsi et al. discovered a new type of two‐dimensional transition metal carbides and nitrides, called MXenes, which have become a dazzling new star in the energy storage industry. MXenes are endowed with a series of fascinating properties due to their unique structures and tunable surface chemical functional groups. The application of MXenes in electrochemical energy storage has attracted special attention, especially showing great potential in supercapacitor applications. Compared with other materials, MXenes have high mechanical flexibility, high energy density, and good electrochemical performance, so they are especially suitable as electrode materials for supercapacitors. However, similar to other 2D materials, due to the strong van der Waals forces, MXene layers inevitably undergo stacking agglomeration, resulting in severe loss of electrochemically active sites. If the self‐stacking of MXenes layers can be effectively suppressed, their electrochemical performance will be enhanced. Structural optimization of MXenes and composite doping of MXenes with other materials are two strategies with significant effects. This review summarizes recent advances in MXene synthesis, fundamental properties, and composite materials, focusing on the latest electrochemical performance of MXene‐based electrodes/devices, and puts forward the challenges and new opportunities that MXenes face in this emerging energy storage field.

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“…Original MXene has a sheet-like structure with an average size of ∼80 nm, whereas NH 2 -MXene exhibited a similar sheet structure, which indicated the incorporation of amine groups did not cause damage to the structure of MXene. 15,16 Corresponding elemental distribution (Fig. 2c–f) confirmed the successful preparation of NH 2 -MXene, as evidenced by the simultaneous presence of C and Ti elements of MXene and N elements of APTES.…”

The Many Deaths of Supercapacitors: Degradation, Aging, and Performance Fading

“…[ 203 ] Accordingly, MXenes have wealthy surface functional groups (e.g., OH, F, O), which provide a considerably large number of active sites with great potential for efficient loading of active materials and surface modification. [ 201 ] Hence, MXenes have high electrical conductivity, hydrophilicity, and ion intercalation. [ 204 ] Furthermore, their high mechanical strength and volumetric specific capacity are beneficial for preparing binder‐free electrode materials, increasing the interest in using MXenes in supercapacitor applications.…”

“…They can be used not only as active material but also as a binder, flexible backbone, and conductive additive. [ 201 ] The combination of Ti 3 C 2 T x MXene and rGO for preparing composite electrodes for flexible supercapacitors was reported with excellent cycling stability of 90% capacitance retention after 40 000 cycles at a high current of 100 A g −1 ( Figure 11 A). [ 215 ] The lifespan of the main performance of MXene‐based flexible supercapacitors at different rates is summarized in Table 4.…”

A Review of Nb2CTx MXene as an Emerging 2D Material: Synthesis, Applications in Rechargeable Batteries and Supercapacitors, Progress, and Outlook

“…Ti 3 C 2 T x was synthesized by etching of its MAX phase, Ti 3 AlC 2 , using hydrofluoric acid (HF) . More than 25 different MXenes have been synthesized, including Ti 3 C 2 T x , Zr 3 C 2 T x , Nb 2 CT x , V 2 CT x , Mo 2 CT x , Ti 4 N 3 T x , Mo 2 ScC 2 T x , (Ti 0.5 Nb 0.5 ) 2 CT x , (Nb 0.8 Ti 0.2 ) 4 C 3 T x , and (Nb 0.8 Zr 0.2 ) 4 C 3 T x , to name a few. The combinations of individual constituents are varied, and more than 100 MAX phases have been successfully synthesized to date.…”

“…8 T i 0 . 2 ) 4 C 3 T x , 3 4 a n d (Nb 0.8 Zr 0.2 ) 4 C 3 T x , 35 to name a few. The combinations of individual constituents are varied, and more than 100 MAX phases have been successfully synthesized to date.…”