Research ArticleELECTROCHEMISTRY

Ultrahigh areal number density solid-state on-chip microsupercapacitors via electrohydrodynamic jet printing

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Science Advances  06 Mar 2020:
Vol. 6, no. 10, eaaz1692
DOI: 10.1126/sciadv.aaz1692
  • Fig. 1 Fabrication of on-chip UHD SS–MSCs via EHD jet printing.

    (A) Schematic representation depicting stepwise fabrication of the on-chip UHD SS–MSC. (B) Photograph of the SS–MSC on a human finger. (C) Optical microscopy image of the interdigitated electrodes (feature size = 10 μm) on the Ti/Au current collector. (D) Cross-sectional SEM image of the electrode/solid-state gel electrolyte assembly formed on the SiO2/Si chip. (E) Conceptual illustration of the on-chip UHD SS–MSC monolithically integrated with the circuit board of an electronic device. Photo credit: (B) Kwon-Hyung Lee, Ulsan National Institute of Science and Technology.

  • Fig. 2 Design of electrode inks and fabrication of electrodes via EHD jet printing.

    (A) Zeta potential profile of the electrode ink containing the CMC binder that acts as a surface charge–tuning agent of the nAC particles. (B) Schematic of the electrode ink representing the CMC-assisted electrostatic repulsion and its beneficial effect on the dispersion stability. (C) UV-vis absorption spectra and photographs (inset) of the electrode inks (initially and after 3 weeks). a.u., arbitrary units. (D) Conceptual depiction of various EHD jetting modes and change in the diameter of the ejected electrode droplets as a function of applied voltage. Insets are photographs of the droplets in different jetting modes. Scale bars, 20 μm. (E) Optical microscopy images and thickness variation of the electrodes as a function of printing cycles. (F) SEM image of the printed electrode (20 printing cycles). (G) Photographs of letter (“UNIST”)-shaped printed electrodes of different sizes and micrometer-sized printed electrodes with various form factors. Photo credit: (C) Kwon-Hyung Lee, Ulsan National Institute of Science and Technology.

  • Fig. 3 Solid-state gel electrolytes fabricated via UV curing–assisted EHD jet printing.

    (A) Schematic representation depicting preparation of the solid-state gel electrolyte, along with the chemical structures of the electrolyte components. (B) Change in the characteristic FTIR peaks assigned to thiol (─SH) groups (2575 cm−1) and acrylic C═C bonds (1610 to 1625 cm−1) in the thiol-ene polymer network before/after UV curing. (C) Optical microscopy image of the solid-state gel electrolyte–deposited pixel arrays (area of a pixel = 0.8 mm × 0.8 mm) after being subjected to mechanical vibration for 60 s (vortex mixer; amplitude, 3 mm; frequency, 2000 Hz). Inset shows the liquid electrolyte (i.e., [EMIM][TFSI]) pixel arrays. (D) Ionic conductivity of the solid-state gel electrolyte as a function of temperature. RT, room temperature, 25°C. (E) Change in the ionic conductivity and dimensions of the solid-state gel electrolyte at 150°C as a function of elapsed time. (F) Optical microscopy image of the solid-state gel electrolyte fabricated directly on the interdigitated electrode-deposited SiO2/Si chip substrate via EHD jet printing. Inset shows an EDS elemental mapping image showing uniform coverage of the interdigitated electrodes with the solid-state gel electrolyte, in which the green dots represent fluorine atoms originating from the [EMIM][TFSI] ionic liquid. Photo credit: (A and E) Kwon-Hyung Lee, Ulsan National Institute of Science and Technology.

  • Fig. 4 Electrochemical performance of SS–MSCs.

    (A) Optical microscopy images of the printed electrodes with different widths (10, 20, and 40 μm, denoted as W10, W20, and W40, respectively). Scale bars, 50 μm. (B) Nyquist plots of the SS–MSCs with different electrode widths. Inset shows an associated equivalent circuit based on a modified Randles circuit. Red arrows indicate knee frequencies. (C) CV profiles (scan rate, 1 to 500 mV s−1) of the SS–MSC. Inset shows a photograph of the SS–MSC. (D) Capacitance retention (scan rate, 1000 mV s−1) of the SS–MSC as a function of charge/discharge cycle number. (E) Galvanostatic charge-discharge (GCD) profiles of the five SS–MSC unit cells connected in series or in parallel. (F) Photograph of the micro–light emitting diode (LED) powered by 10 SS–MSC unit cells with the combined configuration (2S × 5P) of two cells in series (2S) and five cells in parallel (5P, represented by the red dashed boxes). Photo credit: (F) Kwon-Hyung Lee, Ulsan National Institute of Science and Technology.

  • Fig. 5 On-chip UHD SS–MSCs as a device-unitized power source.

    (A) Photographs and schematic representation of the UHD SS–MSCs (comprising 36 unit cells connected in series) fabricated on a chip (area = 8.0 mm × 8.2 mm, smaller than a coin). Inset shows an optical microscopy image of the unit cell in the UHD SS–MSCs. (B) Photograph of the on-chip UHD SS–MSCs monolithically integrated on a circuit board of an electronic device. (C) A series of CV profiles (scan rate, 1 V s−1) of the on-chip UHD SS–MSCs in the voltage range 5 to 43.2 V at an interval of 5.0 V (the last interval was 3.2 V). (D) Capacitance retention (scan rate, 20.0 V s−1) of the on-chip UHD SS–MSCs as a function of charge/discharge cycle number at an areal operating voltage of 65.9 V cm−2. Inset shows CV profiles over a wide range of scan rates (0.1 to 5.0 V s−1) after exposure to a hot plate (80°C) for 0.5 hours. Photo credit: (A and B) Kwon-Hyung Lee, Ulsan National Institute of Science and Technology.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/10/eaaz1692/DC1

    Fig. S1. Basic characteristics of nAC.

    Fig. S2. Characteristics of the electrode ink with and without CMC binder.

    Fig. S3. Process description of the EHD jet printing for the fabrication of interdigitated electrodes.

    Fig. S4. Characterization of the EHD jet-printed electrodes as a function of printing cycles.

    Fig. S5. EHD jet printing of the electrolyte ink.

    Fig. S6. Characteristics of the solid-state gel electrolytes.

    Fig. S7. Photographs showing contact angle change and effect on the affinity between the electrolyte ink and SiO2/Si chip substrate.

    Fig. S8. Configuration and electrochemical performance of the SS–MSC.

    Fig. S9. Schematic representation of the five SS–MSCs.

    Table S1. Comparison in the major characteristics between the on-chip UHD SS–MSCs (this study) and the previously reported MSCs fabricated by printing techniques.

    Movie S1. Video clip showing the fabrication of interdigitated electrodes on top of the SiO2/Si chip substrate through the EHD jet printing.

    Movie S2. Video clip showing the fabrication of solid-state gel electrolytes on top of interdigitated electrodes-deposited SiO2/Si chip substrate through the EHD jet printing.

    References (3740)

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Basic characteristics of nAC.
    • Fig. S2. Characteristics of the electrode ink with and without CMC binder.
    • Fig. S3. Process description of the EHD jet printing for the fabrication of interdigitated electrodes.
    • Fig. S4. Characterization of the EHD jet-printed electrodes as a function of printing cycles.
    • Fig. S5. EHD jet printing of the electrolyte ink.
    • Fig. S6. Characteristics of the solid-state gel electrolytes.
    • Fig. S7. Photographs showing contact angle change and effect on the affinity between the electrolyte ink and SiO2/Si chip substrate.
    • Fig. S8. Configuration and electrochemical performance of the SS–MSC.
    • Fig. S9. Schematic representation of the five SS–MSCs.
    • Table S1. Comparison in the major characteristics between the on-chip UHD SS–MSCs (this study) and the previously reported MSCs fabricated by printing techniques.
    • Legends for movies S1 and S2
    • References (3740)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Video clip showing the fabrication of interdigitated electrodes on top of the SiO2/Si chip substrate through the EHD jet printing.
    • Movie S2 (.mp4 format). Video clip showing the fabrication of solid-state gel electrolytes on top of interdigitated electrodes-deposited SiO2/Si chip substrate through the EHD jet printing.

    Files in this Data Supplement:

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