Thin film of Ti3C2TxMXene-based flexible energy storage device with industrial scale and environmental stability

I. Overview of the article. 


MXenes, two-dimensional transition metal carbides and nitrides have attracted great interest because of their excellent metal conductivity, solution treatability, energy storage and other applications. However, the original MXene thin films often have the problems of poor environmental stability and mechanical properties caused by its polar terminal groups, so the interlayer interaction is weak. In this paper, a heteroatomic doping strategy with adaptive surface function of MXene is proposed, and then a large size reduced graphene oxide is added as a conductive additive to expand the production of high mechanical strength S, N-MXene/rGO (SNMG-40) mixed films. It is worth noting that SNMG-40 films also show long-term cyclic stability and can be immersed in environmental conditions or in sulfuric acid electrolytes for more than 100 days. This strategy proposed by the author makes MXene materials more competitive as flexible electronic devices and EMI shielding in practical applications. 




Second, guided reading of picture and text. 



Figure 1. 
Schematic diagram of the synthesis of S and N-doped MXene. 

The manufacturing process of S and N-doped Ti3C2TxMXene includes two main steps: Ti3C2TxMXene thin sheet and annealing doping of sulfur and nitrogen atoms. 



Figure 2. 
Characterization of partial 2D-Ti3C2Tx carrying molecules. 

The XRD patterns of pure MXene and S, N-MXene and embedded (002) peaks show the EDS mapping images of S and N elements. 





Figure 3. 
High resolution XPS spectra of several S and N-MXene. 






Figure 4. 
Preparation and characterization of SNMG thin films. 

Figure (a) S, N-MXene/rGO (SNMG) mixed film can be continuously treated by leaf coating, natural drying and go reduction. In the first step, S water and N-MXene/GO composite dispersions are dispersed on the surface of polyester substrate. Before this process, the high quality thin films of S and N-MXene were characterized by transmission electron microscope (TEM) and atomic force microscope (AFM). As shown in figure 2B, large area freestanding SNMG-40 films have good flexibility and can be rolled up for easier storage. In order to observe the morphology and microstructure of SNMG thin films, scanning electron microscope (SEM) and TEM images were obtained. As shown in figure 2C, the thickness of the SNMG-40 film is about 1 μ m, showing a highly aligned layered structure from the cross-sectional SEM image. 






Figure 5. 
Energy storage properties of SNMG thin films. 

Heteroatom-doped SNMG thin films have good conductivity, excellent flexibility and unique alternating stacking structure. Therefore, they are expected to have good electrochemical performance, high energy storage capacity, rapid electrolyte transport and improved cycle stability. As shown in the figure above, the electrochemical performance of SNMG thin films as electrodes was evaluated. 






Figure 6. 
Application of SNMG-40 thin film in flexible asymmetric supercapacitors. 

As shown in the figure above, you can see that the capacitance is maintained at different bending angles and inserted into the above equipment, the display device can power the LED in the bending state. 




III. Summary of the full text. 

To sum up, the authors have proved that the combination of S, n-doped MXene and large rGO films can produce MXene-based films (SNMG-40) with enlarged area and stable environment by blade coating method. The resulting SNMG-40 films show excellent electrical conductivity (1198Scm-1), tensile strength up to ≈ 45MPa, and high capacitance of 698.5F cm-3. AMGSC also provides excellent mechanical durability and energy storage performance. This work helps to achieve scalable and environmentally stable MXene-based films, as well as a balance between high electrochemical and mechanical properties, thus allowing flexible MXene-based films to shift from labor-scale research to large-scale practical applications. 

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