Layered reduced graphene oxide with nanoscale interlayer gaps as a stable

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1 Layered reduced graphene oxide with nanoscale interlayer gaps as a 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. NATURE NANOTECHNOLOGY 1

2 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. 2 NATURE NANOTECHNOLOGY

3 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 3

4 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. 4 NATURE NANOTECHNOLOGY

5 SUPPLEMENTARY INFORMATION Supplementary Figure 2. Time evolution of Li infusion into layered rgo film. Timelapse images (a, 0s; b, 5s; c, 12s; d, 20s; e, 45s) of Li infusion process into the sparkedrgo 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. NATURE NANOTECHNOLOGY 5

6 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. 6 NATURE NANOTECHNOLOGY

7 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 7

8 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. 8 NATURE NANOTECHNOLOGY

9 SUPPLEMENTARY INFORMATION 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 m 2 g -1 and m 2 g -1, respectively. NATURE NANOTECHNOLOGY 9

10 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). 10 NATURE NANOTECHNOLOGY

11 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 11

12 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. 12 NATURE NANOTECHNOLOGY

13 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 13

14 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 14 NATURE NANOTECHNOLOGY

15 SUPPLEMENTARY INFORMATION 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). NATURE NANOTECHNOLOGY 15

16 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. 16 NATURE NANOTECHNOLOGY

17 SUPPLEMENTARY INFORMATION 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). NATURE NANOTECHNOLOGY 17

18 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. 18 NATURE NANOTECHNOLOGY

19 SUPPLEMENTARY INFORMATION 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 1 st to the 100 th 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. NATURE NANOTECHNOLOGY 19

20 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 80 th to 100 th cycle as marked with dash line in a. c, The detailed voltage profiles from 230 th cycle to 250 th cycle as marked with dash line in a. 20 NATURE NANOTECHNOLOGY

21 SUPPLEMENTARY INFORMATION 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). LirGO 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. NATURE NANOTECHNOLOGY 21

22 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 1 st, 10 th, 50 th, and 100 th cycles were further shown in the inset figures with scale of y axis shown on the left. 22 NATURE NANOTECHNOLOGY

23 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 23

24 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. 24 NATURE NANOTECHNOLOGY

25 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 25

26 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. 26 NATURE NANOTECHNOLOGY

27 SUPPLEMENTARY INFORMATION 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. NATURE NANOTECHNOLOGY 27