M4X3 MXenes: Application in Energy Storage Devices

Abstract

MXene has garnered widespread recognition in the scientific community due to its remarkable properties, including excellent thermal stability, high conductivity, good hydrophilicity and dispersibility, easy processability, tunable surface properties, and admirable flexibility. MXenes have been categorized into different families based on the number of M and X layers in M_n+1X_n, such as M₂X, M₃X₂, M₄X₃, and, recently, M₅X₄. Among these families, M₂X and M₃X₂, particularly Ti₃C₂, have been greatly explored while limited studies have been given to M₅X₄ MXene synthesis. Meanwhile, studies on the M₄X₃ MXene family have developed recently, hence, demanding a compilation of evaluated studies. Herein, this review provides a systematic overview of the latest advancements in M₄X₃ MXenes, focusing on their properties and applications in energy storage devices. The objective of this review is to provide guidance to researchers on fostering M₄X₃ MXene-based nanomaterials, not only for energy storage devices but also for broader applications.

Keywords: 2D materials; Energy storage; M4X3 MXenes; MXene; Properties.

Fig. 1

Overview schematic of the review focus areas

Fig. 2

a A brief timeline of the progress in M₄X₃ MXenes. b Synthesized MXenes reported to date, including 18 M₂X, 12 M₃X₂, 14 M₄X₃, and three M₅X₄. Reproduced with permission from Ref. [18]. Copyright 2023, American Chemical Society

Fig. 3

Unique properties of MXene materials

Fig. 4

a CVs at different potential windows at a scan rate of 1 V s⁻¹. Reproduced with permission from Ref. [72]. Copyright 2019, Elsevier; b CVs of MXene-Ti_xTa_4–xC₃ at different potential windows at a scan rate 1 V s⁻¹. Reproduced with permission from Ref. [125]. Copyright 2023, ACS Publications; and c step-by-step synthesis and schematic model and stoichiometry of TTO hybrid structure for the fluorine-free conversion of the Ta₄AlC₃ MAX phase to surface-modified Ta₄C₃T_x MXene nanosheets decorated with tantalum oxide nanoparticles. Reproduced with permission from Ref. [127]. Copyright 2021, Wiley

Fig. 5

In-situ XRD patterns during electrochemical cycles in a 1 m H₂SO₄ and b 1 m MgSO₄. Reproduced with permission from Ref. [128]. Copyright 2020 Wiley: TEM images of c 6-Nb₄C₃T_x, d 8-Nb₄C₃T_x flakes. Inset shows SAED patterns, e variation of specific capacitance versus scan rate, and f schematic illustrating transport of electrolyte ions through Nb₄C₃T_x layers and ion diffusion pathways between MXene sheets and across a Nb₄C₃T_x flake with a pinhole. Reproduced with permission from Ref. [98]. Copyright 2022, Elsevier. g CVs of three-electrode cells containing a TMA-Nb₄C_3, h calculated specific capacitances of the TMA-Nb₄C₃ electrode as a function of scan rate, and i CVs of three-electrode cells containing Li-V₂C (− ve), Li-V₂O₅-CNT (+ ve) electrodes, and Li-V₂C/Li-V₂O₅-CNT asymmetric cell at 5 mV s⁻¹. Reproduced with permission from Ref. [67]. Copyright 2023, Wiley

Fig. 6

a Preparation schematic for the d-V₄C₃T_x film and b the d-V₄C₃T_x film for 60,000 cycles (the inset shows the charge–discharge profiles from the first to 10th cycles and the last ten cycles for the 60,000th cycles). Reproduced with permission from Ref. [96]. Copyright 2022, Wiley. Photographs of the water droplet shape with the contact angle (CA) on cold-pressed free-standing discs of the ball-milled c V₄AlC₃ and d V₄C₃T_x. Reproduced with permission from Ref. [68]. Copyright 2019, Elsevier. e GCD curves of the V₄C₃T_x, NH₃-V₄C₃T_x-350 °C and NH₃-V₄C₃T_x-550 °C at 3 A g⁻¹. Reproduced with permission from Ref. [69]. Copyright 2019, Elsevier

Fig. 7

a Schematic illustration of the synthesis of partially oxidized Mo₂Ti₂C₃ (PO-Mo₂Ti₂C₃), cross-sectional SEM images of b Mo₂Ti₂C₃ and c PO-Mo₂Ti₂C₃ free-standing MXene films. Reproduced with permission from Ref. [129]. Copyright 2023, Wiley. d Variation of b-values as a function of potential for the anodic scan. The inset shows the power–law dependence of the peak current at scan rates from 5 to 200 mV s^–1. e Percentage of the surface-controlled and diffusion-controlled area in the CV curve at a scan rate of 25 mV s^–1 for f-Mo₂Ti₂C₃. Reproduced with permission from Ref. [130]. Copyright 2022, ACS Publications

Fig. 8

Future directions of M₄X₃ MXenes