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On/off switchable electronic conduction in intercalated metal-organic frameworks

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Science Advances  25 Aug 2017:
Vol. 3, no. 8, e1603103
DOI: 10.1126/sciadv.1603103
  • Fig. 1 Schematic illustration of redox mechanism for crystalline 2,6-Naph(COOLi)2.

    Orange, intercalated Li; green, pristine Li; red, O; blue, C; white, H.

  • Fig. 2 Predictive calculation of electronic band conduction.

    (A to C) Calculated electronic band structures obtained from the HSE06 functional for the pristine sample (A) and the Li-intercalated sample corresponding to model 1 (B) and model 2 (C). The valance band maximum and conduction band minimum (CBM) are represented in the band structures as blue and red lines, respectively. (D to F) 3D electron density distribution (obtained with the PBEsol functional) of the CBM of the 2,6-Naph(COOLi)2 crystal structure for the pristine sample (D) and the Li-intercalated sample corresponding to model 1 (E) and model 2 (F). Orange, intercalated Li; green, pristine Li; red, O; blue, C; white, H. (G to I) 2D electron density distribution of the CBM across the π-stacking packing naphthalene layer via the C1, C1′, C2, and C2′ carbons corresponding to the figure above for the pristine sample (G) and the Li-intercalated sample obtained using model 1 (H) and model 2 (I).

  • Fig. 3 Predictive calculation of electron hopping conduction.

    (A and B) Schemes of electron hopping pathways between adjacent molecules for the pristine sample (A) and the Li-intercalated samples corresponding to model 2 (B). Orange, intercalated Li; green, pristine Li; red, O; blue, C; white, H. (C to E) Comparison of the predicted electronic transfer integral (C), diffusion coefficient (D), and drift mobility of hopping (E) before and after Li intercalation.

  • Fig. 4 Experimental confirmation of switchable electronic conduction.

    (A) Schematic of chemical reductive lithiation of 2,6-Naph(COOLi)2 using lithium naphthalenide. (B) Photographs of 2,6-Naph(COOLi)2 electrode without conductive carbon before (left) and after (right) being immersed in a lithium naphthalenide/tetrahydrofuran (THF) solution. (C to E) Comparison of I-V curves (C), Bode plots (D), and Nyquist plots (E) for 2,6-Naph(COOLi)2 samples before (blue) and after (red) being immersed in the same solution. In (E), the inset is the equivalent circuit for a mixed electronic and ionic conductive material. The intersections at high (100 kHz) and low (1 Hz) frequencies with the real axis are the mixed electronic and ionic resistances in parallel (ReRi/Re + Ri) and the only electronic resistance (Re), respectively. (F) Arrhenius plots of each conductivity obtained from I-V curves and EIS at various temperatures (fig. S10), σe (red) and σi (green), which are calculated using the equivalent circuit model shown in the inset of (E) for the mixed electronic and ionic conductive material, and polarization measurement, σI-V (blue). All conductivity values were calculated using percolation theory (see Materials and Methods).

  • Fig. 5 Heat-responsive on/off switching of electronic transport characteristics.

    (A) Temperature dependence of in situ powder XRD patterns of Li-intercalated 2,6-Naph(COOLi)2 for temperatures of up to 400°C. (B to D) Change in Bode plots (B), I-V curves (C), and Nyquist plots (D) for pristine, Li-intercalated samples and Li-intercalated samples prepared by heat treatment at temperatures of 100° and 200°C.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/8/e1603103/DC1

    fig. S1. Charge/discharge curves and differential capacity (dQ/dV) curves.

    fig. S2. The profile of GITT against time.

    fig. S3. Electrochemical behavior before and after Li intercalation.

    fig. S4. Schematic illustrations of the crystalline structures corresponding to the pristine and Li-intercalated states.

    fig. S5. DOS and PDOS profiles.

    fig. S6. Ex situ powder XRD patterns without conductive carbon before (left) and after (right) being immersed in a lithium naphthalenide/THF solution.

    fig. S7. Schematic illustration of closed parallel-pellet cell used for electrical measurements.

    fig. S8. Interpretation of electron and ion transport mechanism of the proposed material.

    fig. S9. Dependence of electrical properties on the treatment time of the chemical Li intercalation.

    fig. S10. Electrical properties of the Li-intercalated 2,6-Naph(COOLi)2 samples at various temperatures.

    fig. S11. Powder XRD patterns of pristine nondoped sample (black line) and Li-doped sample after heating (red line).

    fig. S12. Temperature dependence of in situ powder XRD patterns of Li-intercalated 2,6-Naph(COOLi)2 for temperatures of up to 400°C in the high-angle region.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Charge/discharge curves and differential capacity (dQ/dV) curves.
    • fig. S2. The profile of GITT against time.
    • fig. S3. Electrochemical behavior before and after Li intercalation.
    • fig. S4. Schematic illustrations of the crystalline structures corresponding to the pristine and Li-intercalated states.
    • fig. S5. DOS and PDOS profiles.
    • fig. S6. Ex situ powder XRD patterns without conductive carbon before (left) and after (right) being immersed in a lithium naphthalenide/THF solution.
    • fig. S7. Schematic illustration of closed parallel-pellet cell used for electrical measurements.
    • fig. S8. Interpretation of electron and ion transport mechanism of the proposed material.
    • fig. S9. Dependence of electrical properties on the treatment time of the chemical Li intercalation.
    • fig. S10. Electrical properties of the Li-intercalated 2,6-Naph(COOLi)2 samples at various temperatures.
    • fig. S11. Powder XRD patterns of pristine nondoped sample (black line) and Li-doped sample after heating (red line).
    • fig. S12. Temperature dependence of in situ powder XRD patterns of Li-intercalated 2,6-Naph(COOLi)2 for temperatures of up to 400°C in the high-angle region.

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