SCIENCE CHINA Materials, Volume 63 , Issue 7 : 1216-1226(2020) https://doi.org/10.1007/s40843-020-1302-6

Reduced CoNi2S4 nanosheets decorated by sulfur vacancies with enhanced electrochemical performance for asymmetric supercapacitors

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  • ReceivedFeb 3, 2020
  • AcceptedMar 16, 2020
  • PublishedMay 8, 2020


Nowadays, it is a matter of great concern to design electrode materials with excellent electrochemical performance for supercapacitors by a safe, efficient and simple method. And these characteristics are usually related to the vacancies and impurities in the electrode. To investigate the effect of the vacancies on the electrochemical properties of the supercapacitor cathode material, the uniform reduced CoNi2S4 (r-CoNi2S4) nanosheets with sulfur vacancies have been successfully prepared by a one-step hydrothermal method. And the formation of sulfur vacancies are characterized by Raman, X-ray photoelectron spectroscopy and other means. As the electrode for supercapacitor, the r-CoNi2S4 nanosheet electrode delivers a high capacity of 1918.9 F g−1 at a current density of 1 A g−1, superior rate capability (87.9% retention at a current density of 20 A g−1) and extraordinary cycling stability. Compared with the original CoNi2S4 nanosheet electrode (1226 F g−1 at current density of 1 A g−1), the r-CoNi2S4 nanosheet electrode shows a great improvement. The asymmetric supercapacitor based on the r-CoNi2S4 positive electrode and activated carbon negative electrode exhibits a high energy density of 30.3 W h kg−1 at a power density of 802.1 W kg−1, as well as excellent long-term cycling stability. The feasibility and great potential of the device in practical applications have been successfully proved by lightening the light emitting diodes of three different colors.

Funded by

the National Natural Science Foundation of China(61376011,51402141)

Gansu Provincial Natural Science Foundation of China(17JR5RA198)

the Fundamental Research Funds for the Central Universities(lzujbky-2018-119,lzujbky-2018-ct08)

and Shenzhen Science and Technology Innovation Committee(JCYJ20170818155813437)


This work was supported by the National Natural Science Foundation of China (61376011 and 51402141), Gansu Provincial Natural Science Foundation (17JR5RA198), the Fundamental Research Funds for the Central Universities (lzujbky-2018-119 and lzujbky-2018-ct08), and Shenzhen Science and Technology Innovation Committee (JCYJ20170818155813437).

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Liu Y, Wen Y and Li H designed and engineered the samples; Liu Y, Wen Y conceived the post-fabrication tuning of random modes; Liu Y and Zhang Y performed the experiments; Liu Y, Wen Y and Zhang Y performed the data analysis; Liu Y wrote the paper with support from Wen Y; Liu Y, Wen Y, Huang J and Peng S contributed to the theoretical analysis. All authors contributed to the general discussion.

Author information

Yanpeng Liu was awarded a BSc degree by Harbin Institute of Technology in 2018. He is currently a graduate student in the School of Materials Science and Engineering at Lanzhou University. His main research interests are nanostructure design of NiCoS supercapacitors and aqueous zinc ion batteries.

Shanglong Peng is a professor of Lanzhou University. From 2010 to 2016, he worked at the University of Washington, Seoul National University and the Hong Kong University of Science and Technology. Currently, he is mainly engaged in the design of nanomaterials, interface regulation and their applications in energy conversion and storage, including supercapacitors, solar cells and flexible wearable integrated energy conversion and storage integrated devices.


Supplementary information

Supporting data are available in the online version of the paper.


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  • Figure 1

    Schematic illustration of fabricating the CoNi2S4 and r-CoNi2S4 nanosheets on the Ni foam and generating the sulfur vacancies by NaBH4 treatment.

  • Figure 2

    SEM images of the r-CoNi2S4 nanosheets at (a) low and (b) high magnifications. (c) TEM and (d) HRTEM images of the r-CoNi2S4 nanosheets, the inset of (d) is the corresponding SAED pattern. (e) TEM image of the region for elemental mapping. (f) Ni, (g) Co, and (h) S element mappings based on image (e).

  • Figure 3

    (a) XRD patterns of the CoNi2S4 and r-CoNi2S4 nanosheets. (b) Raman spectra of the CoNi2S4 and r-CoNi2S4 nanosheets. (c) XPS survey scan spectra, (d) Ni 2p, (e) Co 2p and (f) S 2p of the CoNi2S4 and r-CoNi2S4 nanosheets (Sat. means shake-up satellites).

  • Figure 4

    (a) CV curves of the r-CoNi2S4, the CoNi2S4 and bare Ni foam electrodes at 20 mV s−1 in 6 mol L−1 KOH electrolyte. (b) GCD curves of the r-CoNi2S4 and CoNi2S4 electrodes at 1 A g−1. (c) Specific capacity at different current densities for the r-CoNi2S4 and CoNi2S4 electrodes. (d) Nyquist plots of the r-CoNi2S4 and CoNi2S4 electrodes. (e) Long-term cycling performance for the r-CoNi2S4 and CoNi2S4 electrodes at 20 A g−1 for 4000 cycles.

  • Figure 5

    (a) CV curves of the r-CoNi2S4 and AC electrodes at a scan rate of 20 mV s−1. (b) CV curves of the r-CoNi2S4//AC ASCs at various scan rates from 1 to 50 mV s−1. (c) GCD curves of the r-CoNi2S4//AC ASCs at different current densities from 1 to 20 A g−1. (d) Ragone plots of the devices and the other related reported ASCs. (e) Cycling performance of the r-CoNi2S4//AC ASC during 10,000 cycles at a constant current density of 10 A g−1. The inset of (e) is the optical image of the LEDs with three different colors that are lit by two integrated r-CoNi2S4//AC ASCs connected in series.

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