SUPPLEMENTARY INFORMATIONDOI: 10.1038/NNANO.2016.32
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Supplementary Information
Layered reduced graphene oxide with nanoscale interlayer gaps as stable
host for lithium metal anodes
Dingchang Lin, Yayuan Liu, Zheng Liang, Hyun-Wook Lee, Jie Sun, Haotian Wang, Kai
Yan, Jin Xie, Yi Cui.
Table of contents
Part I: Materials synthesis
Supplementary Figure 1.│Time evolution of spark reaction.
Supplementary Figure 2.│Time evolution of Li infusion into layered rGO film.
Part II: Lithiophilicity of the layered rGO film
Supplementary Figure 3.│Lithiophilicity of various carbon materials.
Supplementary Figure 4.│First-principles calculations on surface binding energy.
Supplementary Figure 5.│Capillary force at different scale and litiophilicity.
Part III: Characterizations on the materials
Supplementary Figure 6.│Brunauer–Emmett–Teller (BET) surface area
characterizations on GO/rGO.
Layered reduced graphene oxide with nanoscale interlayer gaps as a stable
host for lithium metal anodes
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Supplementary Figure 7.│ X-ray photoelectron spectroscopy (XPS) Li 1s spectra
of Li foil and Li-rGO composite.
Supplementary Figure 8.│XPS survey characterizations on GO/rGO.
Supplementary Figure 9.│Raman spectroscopy characterizations on GO/rGO.
Supplementary Figure 10.│X-ray diffraction (XRD) characterizations.
Supplementary Figure 11.│Layered Li-rGO electrodes with different thickness.
Supplementary Figure 12.│Surface morphology of layered Li-rGO after cycled at
5 mA cm-2.
Supplementary Figure 13.│Layered Li-rGO electrode surface after 100
galvanostatic cycles.
Supplementary Figure 14.│Time evolution of Li deposition observed with in situ
TEM.
Supplementary Figure 15.│Ex situ SEM characterization on thickness variation.
Part IV: Electrochemical testing
Supplementary Figure 16.│Comparison on the voltage profiles at various current
density.
Supplementary Figure 17.│Long-cycle stabililty of layered Li-rGO electrode.
Supplementary Figure 18.│Electrochemical cycling performance with ether-based
electrolyte.
Supplementary Figure 19.│Electrochemical cycling of symmetric cells at 2 mA
cm-2.
Supplementary Figure 20.│High areal capacity cycling stability of layered Li-rGO
electrodes.
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Supplementary Figure 21.│Electrochemical impedance spectroscopy
characterizations before cycling.
Supplementary Figure 22.│Electrochemical performance of the LCO/Li-rGO
cells.
Supplementary Figure 23.│Electrochemical performance of the LTO/Li-rGO
cells.
Supplementary Figure 24.│Battery cycling with limited Li amount.
Part V: Supplementary Movies
Supplementary Video 1.│Spark reaction on GO film.
Supplementary Video 2.│Li infustion into rGO film.
Supplementary Video 3.│Flexibility of Li-rGO film.
Supplementary Video 4.│In situ TEM movie of Li infusion with side view. The
video is played at 50 x the actual speed.
Supplementary Video 5.│In situ TEM movie of Li infusion with top view. The
video is played at 15 x the actual speed.
Supplementary Video 6. │ In situ TEM movie of dendritic Li deposition without a
host. The video is played at 50 x the actual speed.
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Supplementary Figure 1. │Time evolution of spark reaction. Time-lapse images of the
spark reaction visualizing the detailed phenomenon of the reaction within 100 milliseconds.
The images of the reaction at different time of 0 ms (a), 20 ms (b), 40 ms (c), 60 ms (d),
80 ms (e), and 100 ms (f) were shown successively. The yellow arrow in a shows the initial
contact point between GO and molten Li, where the reaction initiated. The flame shown in
the images illustrates the possible H2 formation under the strong reduction condition in the
presence of molten Li and its combustion reaction with the trace amount of oxygen in the
glove box. This can be one of the reasons for the interlayer expansion of GO.
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Supplementary Figure 2. │ Time evolution of Li infusion into layered rGO film. Time-
lapse images (a, 0s; b, 5s; c, 12s; d, 20s; e, 45s) of Li infusion process into the sparked-
rGO film. The edge of the sparked-rGO film was put in contact with the molten Li. Rapid
Li infusion can be observed where it took less than 1 minute for Li to spread across the
whole sparked-rGO surface.
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Supplementary Figure 3. │ Lithiophilicity of various carbon materials. Surface
wetting of molten Li on different carbon materials, including CNT film (a,f), carbon fiber
paper (b,g), mesoporous carbon coated on Cu foil (c,h), electrospun carbon nanofiber (d,i)
and sparked-rGO film (e,j). For sparked-rGO film, the molten Li was rapidly infused into
the matrix with good wettability. In contrast, the other carbon materials showed relatively
large contact angle, indicating relatively poor Li surface wettability.
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Supplementary Figure 4. │ First-principles calculations on surface binding energy.
First-principles calculations showing the binding energy between Li and bare graphene
surface (a), carbonyl (C=O) groups (b), alkoxy groups (C-O) (c), and epoxyl (C-O-C)
groups (d). The carbonyl and alkoxy groups show much stronger interaction with Li
compared to bare graphene surface.
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Supplementary Figure 5. │ Capillary force at different scale and litiophilicity.
Schematic showing the effect of capillary force with different surface ‘lithiophilicity’
(‘lithiophobic’-left, ‘lithiophilic’-middle & right) and different interlayer gap dimension
(‘larger interlayer dimension’-middle, ‘nanoscale interlayer dimension’-right). It is known
that the capillary force on lyophobic surface will lower the liquid level while the lyophilic
surface will lift the liquid level. The height of the liquid level is inversely proportional to
the diameter, which means smaller spacing with lyophilic surface will give rise to higher
liquid level.
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Supplementary Figure 6. │ Brunauer–Emmett–Teller (BET) surface area
characterizations on GO/rGO. N2 adsorption-desorption isotherms of the pristine GO
film (blue) and the sparked rGO film (red), from which the BET surface area was calculated
to be 8.0 m2 g-1 and 394.3 m2 g-1, respectively.
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Supplementary Figure 7.│ X-ray photoelectron spectroscopy (XPS) Li 1s spectra of
Li foil and Li-rGO composite. The XPS Li 1s spectra of Li foil and Li-rGO composite
showing the signals of metallic Li (red), Li2O/LiOH (green) and Li2CO3 (blue).
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Supplementary Figure 8.│XPS survey characterizations on GO/rGO. XPS survey
spectra of pristine GO (black) and sparked rGO (red). After spark reaction, significantly
increased C/O ratio can be observed, which indicates the removal of O-containing species
and the reduction of GO in the spark process.
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Supplementary Figure 9. │ Raman spectroscopy characterizations on GO/rGO.
Raman spectra of pristine GO (black) and sparked rGO (red) films. The sparked rGO
showed lower D/G band ratio.
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Supplementary Figure 10. │ X-ray diffraction (XRD) characterizations. XRD spectra
of pristine GO film (blue), sparked rGO (black) and Li-rGO composite (red). Pristine GO
showed a sharp peak at 2θ ~ 11°, which is typical for highly oxidized graphite with
remarkably increased interlayer spacing (d ~ 0.8 nm). The peak at 2θ ~ 11° disappeared for
sparked rGO, indicating the partial reduction of GO. A sharp peak corresponding to
metallic Li (110) can be observed for Li-rGO, indicating the successful infusion of Li into
the rGO matrix.
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Supplementary Figure 11. │ Layered Li-rGO electrodes with different thickness.
SEM images of the Li-rGO electrodes with different thickness of ~50 μm (a,d), ~80 μm
(b,e), and ~200 μm (c,f). The magnified SEM images shown in d-f indicate consistent
layered structure with similar spacing despite the electrode thickness
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Supplementary Figure 12. │ Surface morphology of layered Li-rGO after cycled at 5
mA cm-2. Low-magnification (a) and magnified (b) SEM images of the top surface of
layered Li-rGO electrode after 10 galvanostatic cycles with current density of 5 mA cm-2.
The stripping/plating capacity was fixed at 1 mAh cm-2. The images show relatively flat
surface, small quantity of Li can be observed on the top surface (b).
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Supplementary Figure 13.│Layered Li-rGO electrode surface after 100 galvanostatic
cycles. a, SEM image of the layered Li-rGO electrode surface after 100 cycles with SEI
coverage. b, SEM image of the layered Li-rGO electrode surface after 100 cycles where
the region on the left of the red dash line has SEI coverage and that on the right has no SEI
coverage. c, SEM image of the layered Li-rGO electrode surface after 100 cycles without
SEI coverage. Part of SEI layer on the surface was removed gently by mechanical scratch
while the rest part left intact. The cell was cycled in symmetric configuration with layered
Li-rGO as the electrodes, at current density of 1 mA cm-2 with the capacity fixed at 1 mAh
m-2 for 100 cycles.
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Supplementary Figure 14. │ Time evolution of Li deposition observed with in situ
TEM. a-e, Time evolution of Li deposition onto a substrate without stable host. Snapshots
at 0 s, 100 s, 200 s, 300 s and 350 s are shown, with dendritic Li shooting out (Scale bar: 1
μm). f-i, Time evolution of Li deposition into rGO host. Snapshots at 0 s, 100 s, 200 s and
300 s are shown, where no dendritic Li deposition can be observed (Scale bar: 200 nm).
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Supplementary Figure 15. │ Ex situ SEM characterization on thickness variation. Ex
situ SEM characterization on the thickness change before (a), after (b) Li stripping and
after one stripping/plating cycle (c). After Li stripping, only minimal thickness decrease of
~20% can be observed. And after plating Li back, the thickness is similar to the original
state.
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Supplementary Figure 16. │ Comparison on the voltage profiles at various current
density. Voltage profiles of Li-rGO (left column) and Li foil (right column) symmetric
cells at different cycles varied from the 1st to the 100th cycle. Profiles at different current
densities of 1 mA cm-2 (a,b), 2 mA cm-2 (c,d) and 3 mA cm-2 (e,f) were chosen for
comparison.
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Supplementary Figure 17.│Long-cycle stabililty of layered Li-rGO electrode. a,
Galvanostatic cycling of symmetric Li-rGO electrode (blue) and bare Li foil (red) in the
first 500 hours, which is equivalent to 250 cycles. The current density was fixed at 1 mA
cm-2 with stripping/plating capacity of 1 mAh cm-2. b, The detailed voltage profiles from
80th to 100th cycle as marked with dash line in a. c, The detailed voltage profiles from 230th
cycle to 250th cycle as marked with dash line in a.
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Supplementary Figure 18. │ Electrochemical cycling performance with ether-based
electrolyte. a, Galvanostatic cycling of Li foil (red) and Li-rGO film (blue) symmetric
cells in ether-based electrolyte (1M LiTFSI in 1:1, v/v DOL/DME with 1% LiNO3). Li-
rGO electrode showed much lower overpotential as well as more stable cycling stability
compared to the Li foil counterpart. The curves of 800,000-1,000,000 seconds (green dash
rectangle) and 2,800,000-3,000,000 seconds (blue dash rectangle) were enlarged and
shown in b and c, respectively. The Li-rGO electrode exhibited extremely stable cycling
performance in the DOL/DME electrolyte, with stable cycling of >450 cycles as shown in
a.
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Supplementary Figure 19. │ Electrochemical cycling of symmetric cells at 2 mA cm-
2. Galvanostatic cycling of Li foil (red) and Li-rGO film (blue) in symmetric cell
configuration at the current density of 2 mA cm-2. The stripping/plating capacity was fixed
at 1 mAh cm-2. The detailed voltage profiles of the 1st, 10th, 50th, and 100th cycles were
further shown in the inset figures with scale of y axis shown on the left.
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Supplementary Figure 20. │High areal capacity cycling stability of layered Li-rGO
electrodes. Galvanostatic cycling of symmetric Li-rGO electrode (blue) and bare Li foil
(red) with higher areal capacity of 3 mAh cm-2 in the first 300 hours, which is equivalent
to 50 cycles. The current density was fixed at 1 mA cm-2.
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Supplementary Figure 21.│Electrochemical impedance spectroscopy
characterizations before cycling. Nyquist plots of the symmetric cells of Li foil (black)
and layered Li-rGO (red) before electrochemical cycling. Li foil showed considerably
larger interfacial resistance compared to the layered Li-rGO counterpart.
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Supplementary Figure 22. │ Electrochemical performance of the LCO/Li-rGO cells.
Voltage profile comparison of the LCO/Li-rGO cells and the LCO/Li foil cells at the rate
of 0.2 C (a) and 10 C (c). b, Voltage profiles of the LCO/Li-rGO cells operated at various
rates from 0.2 C to 10 C. d, Cycling performance of the LCO/Li-rGO cells and the
LCO/Li foil cells at the rate of 1 C. Activation process was performed at the initial cycles
with the rate of 0.2 C.
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Supplementary Figure 23. │ Electrochemical performance of the LTO/Li-rGO cells.
a, Rate capability of the LTO/Li-rGO and LTO/Li foil cells at various rates from 0.2 C to
10 C. Voltage profile comparison of the LCO/Li-rGO cells and the LCO/Li foil cells at
the rate of 0.2 C (b), 0.5 C (c), 1 C (d), 2 C (e), 4 C (f), and 10 C (g) were shown.
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Supplementary Figure 24. Battery cycling with limited Li amount. │ Cycling stability
test with limited amount of Li. High areal capacity of LTO (~ 3 mAh cm-2) was used here.
LTO was used as the positive electrode and performed as the reservoir for Li. Since LTO
itself does not supply Li to the cell and it has high enough Coulombic efficiency, the Li
source is all from the Li metal electrode while Li loss during cycling should majorly
attributed to the loss on Li metal electrode.
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