Research ArticleELECTROCHEMISTRY

An ion redistributor for dendrite-free lithium metal anodes

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Science Advances  09 Nov 2018:
Vol. 4, no. 11, eaat3446
DOI: 10.1126/sciadv.aat3446
  • Fig. 1

    Schematic illustration of the electrochemical deposition behaviors of the Li metal anodes using (A) a routine PP separator and (B) a composite separator with the LLZTO layer as an ion redistributor to uniform Li-ion distribution.

  • Fig. 2 Morphological characterizations of the composite separator with the LLZTO layer as an ion redistributor.

    (A) Scanning electron microscope (SEM) and digital images of the surface of composite separators. (B and C) Cross section of the composite separator exhibiting (B) an overall view consisting of the LLZTO film and the PP matrix and (C) the LLZTO layer. (D) Digital image of the composite separator at a bending state.

  • Fig. 3 Ion transportation behaviors in a routine PP separator and the composite separator with the LLZTO layer as an ion redistributor.

    (A) Distributions of Li ions through routine PP separator and (B) LLZTO composite separator. Colors in the graph represent the concentration of Li ions ([Li+]). (C and D) SEM images of Li metal deposits through (C) routine PP separator and (D) composite separator.

  • Fig. 4 Electrochemical performances of cells using composite separators with the LLZTO layer as an ion redistributor and routine PP separator.

    (A) Variations of Coulombic efficiency with cycle numbers in Li I Cu cells at a current density of 0.5 mA cm−2 in ether-based (DOL/DME) electrolytes. (B) Interfacial resistance in Li-Li cells calculated from impedance spectra after 1-, 100-, and 750-hour cycling. (C and D) Voltage profiles for Li I Li symmetric cells using (C) carbonate-based EC/DEC electrolytes and (D) ether-based DOL/DME electrolytes at a current density of 1.0 mA cm−2.

  • Fig. 5 Practical pouch-cell performances of LLZTO composite separators and routine PP separators.

    (A) Capacity retention with cycle numbers of pouch cells at 0.1 C. (B) Charge and discharge voltage profiles at the 10th cycle (solid line) and the 50th cycle (dashed line) with LLZTO a composite separator (orange) and routine PP separator (cyan). (C and D) Morphology of Li metal anodes after 90 cycles with (C) composite separators using the LLZTO layer as an ion redistributor and (D) the routine PP separator.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/11/eaat3446/DC1

    Fig. S1. XRD patterns of the LLZTO composite separator (orange), LLZTO powder (cyan), and the powder diffraction file (PDF) of Li5La2Nb2O12.

    Fig. S2. TEM images of the LLZTO ceramic powders.

    Fig. S3. SEM image for the surface of commercial PP separator (Celgard 2400).

    Fig. S4. TGA curves of routine PP separator (cyan) and LLZTO composite separator (orange) in nitrogen or oxygen atmosphere.

    Fig. S5. FEM models for the routine PP separator (without LLZTO layer) and the composite separator (with LLZTO layer).

    Fig. S6. The relative concentration of Li ions beneath the routine PP separator (cyan line) and the composite separator (orange line) at y = 9.0 μm in the FEM simulation results (Fig. 3, A and B).

    Fig. S7. Schematic illustration of the electrolytic cells designed for electrochemical deposition to avoid the effect of stress.

    Fig. S8. Schematic illustration of the coin cells designed for electrochemical deposition to avoid the effect of stress and maintain the close contact between LLZTO ion redistributors and electrodes.

    Fig. S9. SEM images of Li metal deposits in coin cells with PTFE circle.

    Fig. S10. Charge and discharge voltage profiles of Li | Cu cells.

    Fig. S11. Voltage profiles for Li | Li symmetric cells using carbonate-based EC/DEC electrolytes at a current density of 0.5 mA cm−2.

    Fig. S12. Voltage profiles for Li | Li symmetric cells using ether-based DOL/DME electrolytes at a current density of 0.5 mA cm−2.

    Fig. S13. Impedance spectra of Li | Li cells.

    Fig. S14. SEM images of Li metal electrodes in Li | Li symmetric cells.

    Fig. S15. XPS survey of LLZTO layer on composite separators.

    Fig. S16. XPS spectra of LLZTO layer on composite separators.

    Fig. S17. Morphological characterizations of the LLZTO composite separator after cycling.

    Fig. S18. XPS spectra of the deposited Li metal anode surface with the LLZTO composite separator in DOL/DME electrolytes.

    Fig. S19. XPS spectra of the deposited Li metal anode surface with the routine PP separator in DOL/DME electrolytes.

    Fig. S20. Voltage hysteresis of Li | Li pouch cells with EC/DEC electrolytes at a current density of 0.25 mA cm−2.

    Fig. S21. Morphology and cycling performances of the separator with PAN layer of lower ionic conductivity compared with the LLZTO composite separator of the LLZTO film.

    Fig. S22. Morphology of the composite separator with Al2O3 layer.

    Fig. S23. Cycling performances of the composite separator with Al2O3 and LLZTO coating layer.

    Fig. S24. Cycling performances of the composite separator with Al2O3 layer and LLZTO coating layers.

    Fig. S25. Electrochemical impedances of Li | Li symmetrical cells in EC/DEC electrolytes at 1.0 mA cm−2.

    Fig. S26. Ion transportation behaviors in the composite separator with a LLZTO ion conductive layer and a Li-ion insulator layer when limited liquid electrolytes are adopted.

    Fig. S27. Atomic force microscopy analysis of the LLZTO composite separator and the Al2O3 composite separator.

    Fig. S28. Morphology and cycling performances of the separator with a thicker LLZTO film (30 μm) to redistribute Li ions compared with the LLZTO composite separator of the 5-μm LLZTO film.

    Fig. S29. Morphology and cycling performances of the separator with isolated LLZTO particles compared with the LLZTO composite separator of the 5-μm LLZTO film.

    Table S1. Statistics of the concentration of Li ions beneath the routine PP separator and the composite separator at y = 9.0 μm.

    Table S2. Element atomic percentage of Li metal anode surface with the LLZTO composite separator and the routine PP separator obtained from XPS spectra.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. XRD patterns of the LLZTO composite separator (orange), LLZTO powder (cyan), and the powder diffraction file (PDF) of Li5La2Nb2O12.
    • Fig. S2. TEM images of the LLZTO ceramic powders.
    • Fig. S3. SEM image for the surface of commercial PP separator (Celgard 2400).
    • Fig. S4. TGA curves of routine PP separator (cyan) and LLZTO composite separator (orange) in nitrogen or oxygen atmosphere.
    • Fig. S5. FEM models for the routine PP separator (without LLZTO layer) and the composite separator (with LLZTO layer).
    • Fig. S6. The relative concentration of Li ions beneath the routine PP separator (cyan line) and the composite separator (orange line) at y = 9.0 μm in the FEM simulation results ( Fig. 3, A and B).
    • Fig. S7. Schematic illustration of the electrolytic cells designed for electrochemical deposition to avoid the effect of stress.
    • Fig. S8. Schematic illustration of the coin cells designed for electrochemical deposition to avoid the effect of stress and maintain the close contact between LLZTO ion redistributors and electrodes.
    • Fig. S9. SEM images of Li metal deposits in coin cells with PTFE circle.
    • Fig. S10. Charge and discharge voltage profiles of Li | Cu cells.
    • Fig. S11. Voltage profiles for Li | Li symmetric cells using carbonate-based EC/DEC electrolytes at a current density of 0.5 mA cm−2.
    • Fig. S12. Voltage profiles for Li | Li symmetric cells using ether-based DOL/DME electrolytes at a current density of 0.5 mA cm−2.
    • Fig. S13. Impedance spectra of Li | Li cells.
    • Fig. S14. SEM images of Li metal electrodes in Li | Li symmetric cells.
    • Fig. S15. XPS survey of LLZTO layer on composite separators.
    • Fig. S16. XPS spectra of LLZTO layer on composite separators.
    • Fig. S17. Morphological characterizations of the LLZTO composite separator after cycling.
    • Fig. S18. XPS spectra of the deposited Li metal anode surface with the LLZTO composite separator in DOL/DME electrolytes.
    • Fig. S19. XPS spectra of the deposited Li metal anode surface with the routine PP separator in DOL/DME electrolytes.
    • Fig. S20. Voltage hysteresis of Li | Li pouch cells with EC/DEC electrolytes at a current density of 0.25 mA cm−2.
    • Fig. S21. Morphology and cycling performances of the separator with PAN layer of lower ionic conductivity compared with the LLZTO composite separator of the LLZTO film.
    • Fig. S22. Morphology of the composite separator with Al2O3 layer.
    • Fig. S23. Cycling performances of the composite separator with Al2O3 and LLZTO coating layer.
    • Fig. S24. Cycling performances of the composite separator with Al2O3 layer and LLZTO coating layers.
    • Fig. S25. Electrochemical impedances of Li | Li symmetrical cells in EC/DEC electrolytes at 1.0 mA cm−2.
    • Fig. S26. Ion transportation behaviors in the composite separator with a LLZTO ion conductive layer and a Li-ion insulator layer when limited liquid electrolytes are adopted.
    • Fig. S27. Atomic force microscopy analysis of the LLZTO composite separator and the Al2O3 composite separator.
    • Fig. S28. Morphology and cycling performances of the separator with a thicker LLZTO film (30 μm) to redistribute Li ions compared with the LLZTO composite separator of the 5-μm LLZTO film.
    • Fig. S29. Morphology and cycling performances of the separator with isolated LLZTO particles compared with the LLZTO composite separator of the 5-μm LLZTO film.
    • Table S1. Statistics of the concentration of Li ions beneath the routine PP separator and the composite separator at y = 9.0 μm.
    • Table S2. Element atomic percentage of Li metal anode surface with the LLZTO composite separator and the routine PP separator obtained from XPS spectra.

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