SCIENCE CHINA Materials, Volume 62, Issue 4: 474-486(2019) https://doi.org/10.1007/s40843-018-9342-0

Rapid microwave-assisted refluxing synthesis of hierarchical mulberry-shaped Na3V2(PO4)2O2F@C as high performance cathode for sodium & lithium-ion batteries

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  • ReceivedJul 20, 2018
  • AcceptedAug 20, 2018
  • PublishedOct 8, 2018


Unique hierarchical mulberry-shaped Na3V2(PO4)2O2F@C nanocomposite was fabricated by a rapid microwave-assisted low-temperature refluxing strategy. The V(acac)3 reverse micelle systems in the water-in-oil microemulsions played key roles in forming the self-assembly architectures. The prepared Na3V2(PO4)2O2F@C nanoparticles with the anisotropic growth along the [002] direction were in-situ encapsulated in carbon shells, which greatly contribute to fast Na+/e transfer in electrodes. And the self-assemblies with high structure stability help to improve the cycle performance and mitigate voltage fading. The initial discharge capacity of Na3V2(PO4)2O2F@C as cathode for sodium ion batteries is about 127.9 mA h g−1 at 0.1 C. Besides, a high rate performance with a capacity of 88.1 mA h g−1 at 20 C has been achieved, and the capacity retains 82.1% after 2,000 cycles. In addition, the reaction kinetics and Na+ transportation mechanism of Na3V2(PO4)2O2F@C were preliminarily investigated by the ex situ X-ray diffraction, X-ray photoelectron spectroscopy and galvanostatic intermittent titration technique. More interestingly, when coupled with Li, the fabricated hybrid Li/Na-ion batteries also exhibit excellent rate and cycling performances. The proposed rapid refluxing strategy to synthesize mulberry-shaped Na3V2(PO4)2O2F@C opens up a new opportunity to develop high-performance electrode materials for the energy storage systems.

Funded by

the National Natural Science Foundation of China(21303042,21671096,21603094)

the Guangdong Special Support for the Science and Technology Leading Young Scientist(2016TQ03C919)

and the Basic Research Project of the Science and Technology Innovation Commission of Shenzhen(JCYJ20170412153139454,JCYJ20170817110251498)


This work was supported by the National Natural Science Foundation of China (21303042, 21875097, 21671096 and 21603094), Guangdong Special Support for the Science and Technology Leading Young Scientist (2016TQ03C919), and the Basic Research Project of the Science and Technology Innovation Commission of Shenzhen (JCYJ20170412153139454 and JCYJ20170817110251498).

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Hou Y performed the experiments and wrote the manuscript with the guidance from Lu Z and Chang Z. All authors contributed to the general discussion and revision.

Author information

Yan Hou is a PhD student at Henan Normal University. Her research focuses on the development of high-voltage cathode materials for lithium/sodium ion batteries.

Zhouguang Lu is now a Professor in the Department of Materials Science and Engineering, South University of Science and Technology of China. He obtained his BSc from the Central South University in 2001, his MSc degree, under the joint master program between Tsinghua University and Central South University in 2004, and PhD from the City University of Hong Kong in 2009. He is the recipient of Fulbright Fellowship of USA Government in 2008-2009 and the Overseas High-Caliber Personnel (Level B) of Shenzhen Government in 2013. His research mainly covers the design and synthesis of nanostructures and their application in energy storage and conversion with focus on lithium/sodium ion batteries, and lithium-air batteries. He has authored more than 100 peer-review journal papers with total citations of more than 4000 and h-index of 38.


Supplementary information

Supporting information is available in the online version of the paper.


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  • Figure 1

    Schematic illustration of the strategy for the fabrication of the mulberry-shaped Na3V2(PO4)2O2F@C self-assembly nanocomposite.

  • Figure 2

    SEM and TEM images of the samples collected from the reaction solution at various growth stage: (a) 0 h, (b) and (e) 0.5 h, (c) and (f) 1 h; (d) and (g) 220°C for 10 min of the microwave-assisted solvothermal process. Evolution of XRD (h) and Raman (i) patterns of the samples at various growth stage.

  • Figure 3

    Morphological and structural characterizations of NVPF@C. (a) TEM image; (b) HRTEM image; (c) EDX elemental mapping; (d) powder X-ray diffraction pattern and Rietveld refinements; (e) crystal structure of the Na3V2(PO4)2O2F; (f) high resolution XPS spectra of V 2p.

  • Figure 4

    Comparison of the electrochemical performance of the prepared NVPF and NVPF@C (vs. Na+/Na): (a) Representative CV and (b) galvanostatic charge/discharge curves of the initial cycles; (c) Nyquist plots of the impedance spectra; (d) rate capabilities from 0.1 to 50 C; (e) and (f) cycle stabilities at different rates of 1 C for 1,000 cycles and 20 C for 2,000 cycles.

  • Figure 5

    Spectroscopy investigation of the electrochemical reaction mechanism. (a) Comparison of XPS of V element and (b) ex situ XRD patterns collected at various charging/discharging states. (c) CV curves of various scan rates; (d) corresponding relationship between the peak current ip and the square root of the scan rate v1/2; GITT curves and the changes of the Na+ diffusion coefficient of NVPF@C in the initial charge (e) and discharge (f) processes.

  • Figure 6

    The electrochemical performance of NVPF@C in the potential range from 2.5 to 4.5 V (vs. Li+/Li): (a) CV curve at a scan rate of 0.1 mV s−1; (b) GCD curves and (c) rate performance at various current density from 0.065 to 2.600 A g−1; (d) cycle stabilities at a current density of 0.13 A g−1 ; (e) CV curves at various scan rates; (f) corresponding relationship between the peak current ip and the square root of the scan rate v1/2.

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