【Research Background】
      In order to meet the ever-increasing energy storage needs, there is a high degree of research enthusiasm for new materials with high energy and power density, low cost and environmental friendliness. Among the many alternative materials, tin-tin and tin-based materials are among the most promising lithium-ion anode materials, with a theoretical capacity of 944 mAh g-1. However, the defects of tin materials are also obvious, such as strong volume expansion of more than 300%, agglomeration, poor conductivity during lithium insertion and delithiation, accompanied by polarization, powdering and rapid collapse of electrode materials. , in turn, a large capacity reduction. There are many strategies that can be used to improve the performance of tin-based materials, such as nanocrystals for the preparation of tin particles, alloying with other transition metals, and preparation of tin/carbon composites. Among them, tin-based materials and carbon materials are more practical because they can limit volume change and improve conductivity.

 [Introduction]
        Recently, Professor Zheng Junchao of the Central South University published a paper in the internationally renowned academic journal Nano Energy entitled Synthesis of sandwich-like structured Sn/SnOx @MXene composite through in-situ growth for highly reversible lithium storage. A composite of Sn/SnOx nanoparticles grown in situ between two-dimensional MXene (Ti3C2Tx) layers by simple electrostatic attraction and liquid phase reduction is reported. Physical characterization indicates that Sn/SnOx nanoparticles are uniformly distributed in the MXene layer. In between, form a sandwich structure. MXene‘s multilayer structure effectively limits the volume expansion and agglomeration of Sn/SnOx particles, accelerating the transfer of lithium ions and electrons. At the same time, it also effectively limits the re-deposition of the nanosheet during the lithium ion intercalation and deintercalation process, and has a reversible capacity of 594.2 mAh g-1 after 200 charge and discharge cycles. The synergistic effect of the two gives the composite excellent electrochemical properties.

[Graphic introduction]

Figure 1. Synthetic route of Sn/SnOx@Ti3C2 and in situ reduction growth mechanism

图2. Sn/SnO_x, Ti₃C₂, Sn/SnO_x@Ti₃C₂的XRD和拉曼图谱。

Figure 3. SEM image of Sn/SnOx, Ti3C2, Sn/SnOx@Ti3C2; element distribution of Sn/SnOx@Ti3C2; TEM of Sn/SnOx@Ti3C2, HRTEM and Fourier transformed image.

Reaction equation:

SnO2 +4Li++4e- → Sn +2Li2O
SnO+2Li ++2e-→ Sn +Li2O
Sn+ xLi++xe-↔ LixSn
Ti3C2+xLi++xe- ↔ LixTi3C2