【Research Background】

Among metal sulfide anodes, tin (II) sulfide has a higher theoretical capacity (1022 mAh g ^-1 ), which makes it a potential candidate for sodium ion batteries (SIB). The orthorhombic-SnS can store Na ⁺ through a combination of transformation and alloying reaction mechanisms , involving two structural phase transitions from orthorhombic-SnS to cubic- Sn to orthorhombic-Na 15 Sn 4 . The controllable size of nano-tin coupled to the surface of the highly conductive substrate can introduce additional pseudocapacitance to maximize the reaction sites on the surface. The ideal two-dimensional (2D) heterostructure has atomic layer thickness, high surface exposure and a large number of edge sites, with enhanced pseudocapacitance and ultrafast dynamics. However, most SnS nanocomposites are mainly concentrated on graphene-based materials. Exploring new strategies to combine with other promising conductive substrates to achieve controllable fabrication of SnS remains a huge challenge.

【Achievement Introduction】

Recently, the Department of Chemistry, Beijing Institute of Technology Minhua Cao professor research group at the internationally renowned academic journal Chemistry - A European Journal published an article entitled: Toward Understanding pseudocapacitive at The Enhanced Storage in 3D SnS / MXene Architecture Enabled by Engineered Surface Reactions research papers , This study developed a precursor-oriented strategy to obtain 3D SnS / Ti 3 C 2 T x hybrids (expressed as SnS / Ti 3 C 2 T x -O) with excellent Na storage , ie in Ti 3 The surface of the tin hydroxide (Sn 6 O 4 (OH) 4 ) precursor on the C 2 T x nanosheet was grown, then vulcanized in an oil bath, and then annealed. Compared with one-step hydrothermal vulcanization, precursor-guided vulcanization is achieved under mild conditions. The tiny SnS nanocrystals (about 5 nm in size) formed through a strong TiS covalent bond with the wrinkled Ti 3C 2 T x nanosheets are coupled, exposing a large number of edges and active sites. Our SnS / Ti 3 C 2 T x -O negative electrode has a highly tortuous sheet structure, and has a strong 3D network architecture and a designed surface reaction, which can provide pseudocapacitor-based storage in the SIB, significantly improved a capacity G 0.1 ^-1 when G mAh 565 ^-1 and excellent rate performance.

【Graphic introduction】

Flowchart 1.  Schematic diagram of the preparation of 3D SnS / Ti 3 C 2 T x -O and bulk SnS / Ti 3 C 2 T x -H

Figure 1 (a) TEM image of the original Ti 3 C 2 T x nanosheet (b) Sn 6 O 4 (OH) 4  / Ti 3 C 2 T x precursor (c, d) 3D SnS / Ti 3 C 2 T SEM images of x -O and (e, f) bulk SnS / Ti 3 C 2 T x -H

Fig of SnS 2 / of Ti . 3 C 2 T X  -O of (a, b) TEM (c ) HRTEM image (d) EDS spectrum and (e) corresponding to the element mapping images (F) of SnS / of Ti . 3 C 2 T X  -O , SnS / Ti 3 C 2 T x  -H and Ti 3 C 2 T x nitrogen adsorption-desorption isotherms and corresponding pore size distribution (inset)

Figure 3 Physical characterization of SnS / Ti 3 C 2 T x  -O, SnS / Ti 3 C 2 T x  -H and Ti 3 C 2 T x samples

Figure 4 (ac) XANES spectra and related calculations of SnS / Ti 3 C 2 T x -O, SnS / Ti 3 C 2 T x -H and Ti 3 C 2 T x samples (d) SnS / Ti 3 C 2 T X  -O, of SnS / of Ti . 3 C 2 T X  -H, SnCl2 2 ∙ 2H 2 O and SnCl2 . 4 ∙ 5H 2 O in L of Sn . 3 - an edge of the XANES spectrum

Figure 5  Electrochemical performance of SnS / Ti 3 C 2 T x -O electrode

Fig.6  Ectopic XRD pattern of SnS / Ti 3 C 2 T x -O electrode in different states

Fig. 7 Kinetic analysis of the electrochemical behavior of SnS / Ti 3 C 2 T x -O

【Summary of this article】

This article explores a precursor-guided synthesis strategy for the construction of tiny SnS nanocrystals (approximately 5 nm in size) anchored on wrinkled Ti 3 C 2 T x nanosheets. And in SnS / of Ti . 3 C 2 T X of Ti is -H . 3 C 2 T X cover plate on the opposite SnS random, prepared SnS / of Ti . 3 C 2 T X -O ensures powerful 3D network architecture. XPS and EXAFS confirmed the unique Ti-S covalent bond of these two compounds, greatly enhancing the structural durability. In addition, the highly exposed surfaces and edges of SnS nanocrystallites on wrinkled Ti 3 C 2 T x promote ion conduction and reaction kinetics. By greatly improving the surface reaction, the SnS / Ti 3 C 2 T x -O of 1.0 mV s ^-1 can achieve up to 92.7% of the main contribution of the pseudo-capacitance. Overall, combining the advantages of morphology and structural features, SnS / Ti 3 C 2The T x -O negative electrode improves the Na storage performance as a whole. This work will open up a new way to control the sulfide morphology and nano / microstructure adjustment to achieve excellent electrochemical performance.

Literature link:

https://doi.org/10.1002/chem.202000795

Source: MXene Frontier

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