SUPPLEMENTARY INFORMATIONARTICLE NUMBER: 16010 | DOI: 10.1038/NENERGY.2016.10

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Heterogeneous Seeded Growth of Lithium Metal for its Selective

Deposition and Stable Encapsulation Kai Yan1, Zhenda Lu1, Hyun-wook Lee1, Feng Xiong1, 2, Po-Chun Hsu1, Yuzhang Li1, Jie

Zhao1, Steven Chu3 and Yi Cui1, 4* 1Department of Materials Science and Engineering, 2Department of Electrical Engineering, 3Department of Physics, Stanford University, Stanford, CA 94305 USA. 4Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA *Corresponding Author Email: yicui@stanford.edu

Supplementary Figures

Supplementary Figure 1. Phase diagrams of selected materials1, including dissolving materials in lithium (a, b, c, d, e and f for Au, Ag, Zn, Mg, Pt and Al), non-dissolving

Selective deposition and stable encapsulation of lithium through heterogeneous seeded growth

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materials in lithium (g, h and i for C (graphite), Si and Sn) and non-alloying materials with lithium (j and k for copper and nickel).

Supplementary Figure 2. X-ray diffraction spectrum for as synthesized nanocapsules (upper panel). The existence of gold together with two different phases of silicon dioxide can be extracted from the peaks, according to powder diffraction files (PDFs) in the bottom panel. The broad bump around 24˚ is ascribed to amorphous carbon shell.

Supplementary Figure 3. Thermal gravimetric analysis (TGA) of as synthesized carbon nanocapsules. It can be seen that the major mass loss occurred between 550˚C and 600˚C, which corresponded to the oxidation of amorphous carbon. The residual mass included both gold and trivial amount of silica, suggesting mass loading of gold below 25%. Considering the extremely low density of nanocapsules with ~800 nm diameter constructed by only ~20 nm wall thickness, the actual gold loading in the anode is almost negligible. On the other hand, huge void space inside the nanocapsule could be expected, because of the vast difference between gold and carbon in their densities.

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Supplementary Figure 4. Magnified images of Figure 4a and b, showing the detailed structures after lithium metal deposition for carbon shells without (a) and with (b) gold seeds.

Supplementary Figure 5. Magnified images of the in situ TEM setup as well as the lithium metal filing process.

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Supplementary Figure 6. Electron energy loss spectrum (EELS) of nanocapsules before and after lithium deposition. (a) TEM image of several hollow nanocapsules loaded with the in situ setup. (b) and (c) EELS spectra of carbon and lithium before lithium was plated. No lithium signal was observed, indicative of absence of lithium. (d) TEM image of the same sample after deposition of lithium. In addition to the full fillings of lithium metal inside the nanocapsules, the thickness of the carbon shells were observed to thicken outward, suggesting potential deposition of lithium outside carbon shell when the internal space is full. (e) and (f) Corresponding EELS spectra of carbon and lithium after lithium plating. While the carbon signal remained the same, two prominent peaks were observed, proving a direct evidence for the existence of lithium.

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Supplementary Figure 7. Galvanostatic cycling test of carbon shells with gold seeds for lithium metal. (a) Coulombic efficiency of with 2mAh/cm2 capacity. (b) Voltage profiles of lithium metal cycling at cycle 20, 50 and 100. (c) Coulombic efficiency with increasing capacity. The system failed at areal capacity of 3mAh/cm2 due to the limited hollow space. All the tests were carried out in alkyl carbonate electrolyte system (1M LiPF6 in EC:DEC with 1% VC and 10% FEC).

Supplementary References 1. Massalski, T. B. & Okamoto, H. Binary Alloy Phase Diagrams. (ASM International,

1990).