Self-Healing Wide and Thin Li Metal Anodes Prepared. Using Calendared Li Metal Powder for Improving Cycle

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1 Supporting Information Self-Healing Wide and Thin Li Metal Anodes Prepared Using Calendared Li Metal Powder for Improving Cycle Life and Rate Capability Dahee Jin, Jeonghun Oh, Alex Friesen, Kyuman Kim, Taejin Jo, Yong Min Lee *, and Myung-Hyun Ryou * Department of Chemical and Biological Engineering, Hanbat National University, 125 Dongseo-daero, Yuseong-gu, Daejeon, 34158, Republic of Korea 45, Mapo-daero, Mapo-gu, Seoul, Iljin Materials, 04167, Republic of Korea Department of Energy Systems Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno Jungang-Daero, Daegu 42988, Republic of Korea Corresponding Author *Tel.: ; fax: , mhryou@hanbat.ac.kr (M.-H. Ryou) *Tel.: , Fax: , yongmin.lee@hanbat.ac.kr (Y.M. Lee) S-1

2 Table S1. A comparison table of current work with state-of-the-art work on Li metal. N o. Journal name Lithium metal anode information Coating Solution Lithium metal Thickness Cell Assembly Current work Stabilized Lithium Powder (LiMP, Li 2 CO 3 coating) LiMP:PVdF 97:3 Solvent: NMP 40µm (21.5-cm-wide) Li/LMO (2032-coin cell) Heine, Jennifer, et al. Advanced Energy Materials (I.F.; ) Heine et al. Electrochimica Acta 138 (2014) (I.F: ) W.-S. Kim et al. Electrochimica Acta 50 (2004) (I.F: 4.789) C.W. Kwon et al. Journal of Power Sources 93 (2001) 145~150 (I.F:6.721) Coated lithium Powder (CLiP, LiF coating) Coated lithium Powder (CLiP, LiF coating) Lithium metal Powder Lithium metal Powder Not mentioned PVdF/THF PVdF/NMP PIB/Heptane Using compress PVdF/THF PVdF/NMP 125µm (after pressing) 200 µm (Before Pressing) 180~230 µm (after pressing) Depth 300 µm Li/Cu (Swagelok cell) Li/Cu (Swagelok cell) Li powder /Li powder LCO/Li Powder S-2

3 S.-T. Hong et al. Electrochimica Acta 50 (2004) (I.F: 4.789) Adv. Funct. Mater. 2013, 23, (I.F: ) H. Lee et al./adv. Funct. Mater. 2017, (I.F: ) Tu, Zhengyuan et al. Small (2015): (I.F: ) Zheng, Jianming, et al. Nature Energy 2 (2017): Harry, Katherine J., et al. Nature materials 13.1 (2014): (I.F.: ) Liu, Yayuan, et al. Advanced Materials (2017). (I.F.: ) Lithium metal Powder Lithium metal Powder Using compress Using compress 1.60 mm (after pressing) 40µm (after pressing) Li powder /Li powder Li powder / LiV 3 O 8 Lithium metal µm Lithium metal/cu Lithium metal µm Lithium metal/li 4 Ti 5 O 12 Lithium metal µm Lithium metal/nmc442 Lithium metal µm Li metal/li metal Lithium metal 750 µm Lithium metal/li 4 Ti 5 O 12 S-3

4 Figure S1.. Digital camera image of large-scale LiMP electrode that fabricated a 21.5-cm-wide, 40-µmthickness. Figure S2. Voltage profiles of selected cycles of LMO cells coupled with (a) Li foil and (b) 0%, (c) 20%, and (d) 40% compressed LiMP electrodes. S-4

5 Determination of the true average Coulombic efficiency The average Coulombic efficiency (CE) for a Li metal electrode is usually determined by plating a given amount of Li (Q p ) onto a substrate (e.g., Cu, Ni, Pt) and then cycling a small fraction of it (Q c ) until a defined voltage is reached after n cycles, indicating the consumption of Q p. 1 The CE is then calculated by using equation (1): 1 (1) The disadvantage of this method is clearly the dependency on the substrate properties (material, morphology, etc.), which will influence the plating and stripping of the Li metal. Thus, the results from individual substrates are not comparable. This method is suitable for comparing the effects of electrolytes, but it is not suitable for modified Li metal electrodes including surface coating and Li host materials due to the reversed plating and stripping process. Therefore, in this report, we proposed a simple method of determining the true average CE for Li battery systems based on Li metal anodes, employing an excess amount of Li, and with Li-giving intercalationbased compounds as cathodes. Based on the nature of the discharge capacity decrease, we divided the discharge capacity decrease into two regions, which are dominated by different degradation mechanisms (Figure S3). (i) Region A: In this case, the total available amount of Li is larger than the total amount of Li from the cathode (Q Available > Q Cathode ). The major aging mechanism may come from the increased resistance of the anode and/or cathode. With the increased resistance, the amount of Li that can be cycled in the selected voltage window gradually decreases, but it does not suddenly decrease. Consequently, this region exhibits very high CEs. (ii) Region B: In this case, the available amount of Li is less than the total amount of Li from the cathode (Q Available < Q Cathode ). In this region, capacity fading occurs rapidly. Furthermore, at the intersection between regions A and B, the available amount of Li is similar to the total amount of Li from the cathode (Q Available Q Cathode ). To reveal the practical average CEs of battery systems, we only considered region A. By assuming the total amount of Li (Q Li ) depleted from the Li metal electrode and denoting the Li loss in the region A as Q Resistance, the total amount of Li consumption on an Li metal electrode at the intersection between regions A and B becomes Q Li + Q Resistance by following S-5

6 Consequently, the average CE can be calculated based on the cycle number (n) to reach the intersection between regions A and B with equation (2): 1. (2) Q Li can be calculated or estimated based on the geometry, measured electrochemically or by weight. The electrochemical determination can be performed with symmetrical Li/Li cells, as shown in Figure S4, in a full stripping experiment. The calculated CEs and corresponding parameters are listed in Table S2. Equation (2) requires further improvement because it assumes no other failure (e.g., electrolyte depletion) or capacity fading mechanism of the cell other than Li depletion. Furthermore, it is assumed that the cathode has a CE of 100% and that no capacity loss arises from the cathode. 2 Figure S3. Determination of the true average CE of Li metal electrodes coupled with Li giving cathodes. (a) Determination of intersection point B of the Li foil (40 µm) and LiMP (40 µm) electrode as the last maximum. (b) Electrochemically determined Li excess amount Q Li added to Q Cathode in A and the corresponding fit to match intersection point B. S-6

7 Figure S4. Full Li stripping curve of the LiMP and Li foil electrode to determine the absolute capacity of the electrode until a potential increase of 1 V, which corresponds to the Cu potential. In accordance with the electrode mass, specific capacities of ~3,073 mah g -1 and ~3,600 mah g -1 were determined for the LiMP and Li foil electrode, respectively Table S2. Determination of the CE of an Li metal electrode with an LMO cathode and 1.15M LiPF6 in EC:EMC = 3:7 (v:v) + FEC 2 wt.% as an electrolyte with equation (2). LiMP (Compressed 40%) Lithium Foil Specific Capacity (mah g -1 ) Q Anode (mah) Q Anode / Q Cathode Cycle number at intersection point B Q Resistance (mah) Average Coulmbic efficiency of Li (%) S-7

8 Table S3. Calculated energy density increase for a battery stack applying compressed LiMP electrodes in comparison to graphite/lmo cell chemistry. The electrolyte, separator, separator porosity, separator thickness, electrode porosity, binder, conductive agent, electrode thickness, and current collector material and thickness were included in the calculations. The cell packing material and cell design were not considered. The calculations were based on a self-developed model system. Gravimetric energy density increase (%) Volumetric energy density increase (%) LiMP (40µm) / LMO LiMP (20µm) / LMO LiMP (10µm) / LMO Figure S5. Cross-sectional SEM images of 0%, 20%, and 40% LiMP electrodes. References [1] L. Grande, E. Paillard, G.-T. Kim, S. Monaco, S. Passerini, Int. J. Mol. Sci. 2014, 15, [2] B. D. Adams, J. Zheng, X. Ren, W. Xu, and J.-G. Zhang, Adv. Energy Mater. DOI: /aenm S-8