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It is very urgent to develop new anode materials with excellent electrochemical performance for lithium-ion batteries. In this paper, SnO2 / Nga was successfully converted into SnO2 @ Sn / Nga as anode of ternary sodium ion battery by microwave plasma technology. The negative electrode has excellent electrochemical performance, high specific capacity, excellent rate performance and stable cycle performance. This unique nanocomposite design can be extended to other alloy anode materials and used in sodium ion batteries and lithium ion batteries.
With the continuous consumption of fossil fuels and the increasingly serious environmental problems, it is particularly important to find environmentally friendly energy storage technology. Sodium ion battery (SIBS), as a substitute of lithium-ion battery (LIBS), has rich resources and low price. Unfortunately, due to the limitation of sodium ion radius, commercial graphite (sibs: 372mah g-1) can not provide satisfactory sodium storage capacity. Therefore, it is very urgent to develop new anode materials with excellent electrochemical performance for sibs. In view of this, SnO2 with high specific capacity (667mah g-1) and moderate electrochemical window has been widely used as anode materials. However, in addition to the volume expansion and low conductivity of SnO2, there are also some problems that are difficult to overcome: (1) Na2O (SnO2 + 4na + + 4E -? Sn + 2na2o) generated by the conversion reaction will cause large irreversible capacity loss and low initial coulomb efficiency. Although Na2O can prevent the agglomeration of particles, the unstable Sn / Na2O interface can not prevent the phase separation and self aggregation, which greatly reduces the reversibility of the reaction. (2) During the cycling process, Sn particles gradually agglomerate to further slow down the diffusion of Na + in the subsequent alloy reaction (Sn + XNA + + XE -? Naxsn).
Recently, Nanjing University of Posts and Telecommunications professor Yu Kehan (Communication writer) and so on, through the microwave plasma technology, skillfully constructed the core shell structure of SnO2@Sn/ nitrogen doped graphene aerogel (SnO2@Sn/NGA). In the first discharge process, the stable Na2O@Sn interface was obtained, which greatly improved the reversibility of the conversion reaction. Meanwhile, the thin Na2O layer could not only promote the diffusion of Na+. It can effectively prevent the agglomeration of Sn particles. In addition, the plasma reduced the oxygen-containing functional groups in graphene, which improved its conductivity and electrochemical performance. Based on these advantages, SnO2 @ Sn / Nga as a negative electrode shows excellent sodium storage performance. Relevant achievements were published in chemelectrochem under the title of "plasma enabled territory SnO2 @ Sn / nitrogen doped graphene aerogel anone for sodium ion batteries", and were selected as the cover paper. The first author of this paper is Ma Yujie, a graduate student.
Paper link:
https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/celc.202000197
Figure 1. Schematic diagram of SnO2 @ Sn / Nga synthesized by hydrothermal synthesis reaction and microwave plasma process.
Figure 2. Morphology and structural characterization of SnO2 @ Sn / Nga. (a) SEM images of SnO2 / Nga, (B-C) SEM and TEM images of SnO2 @ Sn / Nga, (d-f) HRTEM images and element distribution images of SnO2 @ Sn / Nga.
Figure 3. XPS analysis and XRD and Raman spectra of (a) SnO2 / Nga and SnO2 @ Sn / Nga, (B-E) Sn3d and C1s high resolution XPS spectra, (f) SnO2 / Nga and SnO2 @ Sn / Nga XRD diffraction spectra, (g) SnO2 / Nga and SnO2 @ Sn / Nga Raman spectra.
Figure 4. Electrochemical performance test of SnO2 @ Sn / Nga negative electrode assembled battery (a) CV Curve of SnO2 @ Sn / Nga, (b) charge discharge curve of SnO2 @ Sn / Nga, (C-D) cycle curve and magnification curve of SnO2 @ Sn / Nga and control sample, (E) cycle curve of SnO2 @ Sn / Nga at different current density, (f) AC impedance curve of SnO2 / Nga and SnO2 @ Sn / Nga.
Figure 5. SEM characterization of the electrode after use. The electrode (A-D) SnO2 @ Sn / Nga, (E-H) SnO2 / Nga after 200 cycles of 2A g-1 circulation.
In a word, SnO2 / Nga was successfully converted into SnO2 @ Sn / Nga as anode of ternary sodium ion battery by microwave plasma technology. The core-shell structure of SnO2 @ Sn ensures that Na2O can improve the electrochemical performance of the negative electrode in many ways, especially to prevent particle agglomeration, stabilize the electrode structure, improve the Na + diffusion path, and ensure the reversible conversion of Sn? SnO2. Therefore, the anode has excellent electrochemical performance, high specific capacity, excellent rate performance and stable cycle performance. At the same time, with the increase of the graphitization degree of NGA, the rate property is further improved. In addition, this unique nanocomposite design can be extended to other alloy anode materials and used in sodium ion batteries and lithium-ion batteries. (thanks for Professor Wei's interpretation)
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