Cladding Layer for 3D High Capacity
Supporting Information Solid Electrolyte Lithium Phosphous Oxynitride as a Protective NanoCladding Layer for 3D High Capacity Conversion Electrodes Chuan-Fu Lin1,2*, Malachi Noked1,2,3, Alexander C. Kozen1, 2, Chanyuan Liu1, Oliver Zhao1, Keith Gregorczyk1,2, Liangbing Hu1, Sang Bok Lee3, Gary W. Rubloff1,2 1. Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742ss 2. Institute for System Research, University of Maryland, College Park, MD 20742 3. Department of Chemistry, University of Maryland, College Park, MD 20742 Email: [email protected]; [email protected]
RuO2 ALD Film Properties We characterized the 20 nm ALD RuO2 film deposited on quartz substrates by Raman spectroscopy and XRD. In Figure S1, we observed 3 Raman peaks (blue) at 520 cm-1, 635 cm-1 and 696 cm-1 corresponding to RuO2 peaks (RuO2 powders and RuO2 ALD film) that reported previously to confirm the high quality of RuO2 growth via atomic layer deposition.2 The green curve gives the signal from quartz substrates.
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In Figure S2, we show the X-ray diffraction of ALD grown RuO2 film. The RuO2(110), RuO2(101) and RuO2(211) diffraction peaks are shown in XRD theta-2 theta measurement that confirms the poly-crystallinity of deposited RuO2 film.2-3 The low signal is due to very small amount of RuO2 (20 nm) deposited on the substrates.
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We further utilize transmission electron microscopy to image the core-shell RuO2@MWCNT fabricated by ALD. The high resolution TEM image of RuO2 on MWCNT shown in Figure S3(a) resolves the crystal plane of RuO2 grain that agrees with previous XRD data to confirm the crystallinity of as-prepared RuO2 film. In Figure S3(b), we show the energy-dispersive x-ray spectrum (EDX) of the core-shell structure. C, Ru and O are the main elements detected in EDX spectrum.
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Electrochemical Cycling Behavior In Figure S4 (a), we show that the first discharge capacities of both bare RuO2 and LiPONprotected RuO2 electrodes are higher than the theoretical capacity of RuO2 (806 mAh/g), with current density of 100mA/g. We attribute the additional capacity to electrolyte decomposition on the domains of bare MWCNTs, leading to capacity values that exceed the theoretical values for RuO2 as previously reported.
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We further show the 1st discharge capacity of LiPON-protected RuO2 electrode with C/20 (~50 mA/g) rate in Fugure S4 (b). We observe higher capacity (at least 20% higher) at both the regions above and below 0.8 V compared with Figure S4 (a). Here we demonstrated that it is clear that the kinetics of electrochemical systems play significant roles on specific capacities. Therefore it is difficult to compare one system to another (with different structures, crystallinities, geometries…etc.) by specific capacities. The possible explanation of partial loss of the capacity obtained above 0.8 V (620 mAh/g instead of previously reported 800 mAh/g by Maier et al.) is attributed to partial thermal lithiation of the RuO2 during the ALD process of LiPON, as
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demonstrated by the TEM image of the as-prepared sample in Figure S4c (Note: the thickness of LiPON layer decreased as a function of time as exposed to high energy electron beam in TEM). In our work, we provide reliable controlled samples to investigate the effects of LiPON protection layers on conversion electrodes, which is rather relevant to draw the conclusions we have made in the manuscript.
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In Figure S5, we show the specific capacities of MWCNT@RuO2 vs. MWCNT@RuO2@LiPON. The capacities was derived from the weighed mass of electrodes before and after ALD coating of RuO2 on MWCNT. The LiPON protected MWCNT@RuO2 exhibited superior stability of discharged capacity over 50 cycles, in which the capacity close to its theoretical capacity and maintain healthy retention over 50 cycles. In contrast, the capacity of unprotected RuO2 decays fastly in first 20 cycles. (Data shown in Figure S5 started from 2nd cycle)
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Statistics from Multiple Cells The statistical cycling performance is obtained in Figure S6 by averaging the cycling data over multiple cells (5 cells of MWCNT@RuO2@LiPON; 3 cells of MWCNT@RuO2). In Figure S6, we show the averaged and normalized specific capacities of MWCNT@RuO2 (red) and MWCNT@RuO2@LiPON (blue). It is convincing that even under various uncertain factors (sample variations, ALD coating variations, coin cell assembly, room temperature variations) that could be involved in multiple cells, MWCNT@RuO2@LiPON electrodes show superior
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cycling stability and capacity retention compared with bare MWCNT@RuO2 electrodes statistically.
Self-Discharge Experiment In our system, since we have liquid electrolyte and separator between LiPON-protected RuO2 electrode (working electrode) and Li metal (counter electrode), we don’t expect significant battery self-discharge in the system. In order to show that we further conducted the selfdischarge experiment under conditions that mimic as close as possible to the conditions in the paper published by Talin et al.4 on all-solid-state batteries - namely low current and constant 9
voltage (in fact, our currents are an order of magnitudes higher than the currents in Talin’s paper hence we run the experiment potentiostaticly to avoid need of months of operation). Once the battery is done charging at 2.5 V, we stop the current and take the OCV (open circuit voltage) measurement for additional 8 hours as presented in Figure S7. It is clear that in our system, the self-discharge is negligible (cell potential is maintained and stabilized above 2.32 V for 8 hrs), and the relaxation in voltage is a normal relaxation of the electrochemical system.
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REFERENCES: 1. Hu, L.; Wu, H.; Gao, Y. F.; Cao, A. Y.; Li, H. B.; McDough, J.; Xie, X.; Zhou, M.; Cui, Y., Silicon-Carbon Nanotube Coaxial Sponge as Li-Ion Anodes with High Areal Capacity. Adv. Energy Mater. 2011, 1, 523–527 2. Gregorczyk, K. E.; Kozen, A.C.; Chen, X.; Schroeder, M.A.; Noked, M.; Cao, A.; Hu, L.; Rubloff, G.W., Fabrication of 3D Core–Shell Multiwalled Carbon Nanotube@RuO2LithiumIon Battery Electrodes through a RuO2 Atomic Layer Deposition Process. ACS Nano 2015, 9, 464–473 3. Kim, W. –H.; Park, S. –J.; Kim D. Y.; Kim, H, Atomic Layer Deposition of Ruthenium and Ruthenium-oxide Thin Films by Using a Ru(EtCp)2 Precursor and Oxygen Gas. Journal of the Korean Physical Society, 2009 55, 32∼37 4. Ruzmetov, D.; Oleshko, V. P.; Haney, P. M.; Lezec, H. J.; Karki, K.; Baloch, K. H.; Agrawal, A. K.; Davydov, A. V.; Krylyuk, S.; Liu, Y.; Huang, J. Y.; Tanase, M.; Cumings, J.; Talin, A. A., Electrolyte Stability Determines Scaling Limits for Solid-State 3D Li Ion Batteries. Nano Lett. 2012, 12, 505−511
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RuO2 ALD Film Properties We characterized the 20 nm ALD RuO2 film deposited on quartz substrates by Raman spectroscopy and XRD. In Figure S1, we observed 3 Raman peaks (blue) at 520 cm-1, 635 cm-1 and 696 cm-1 corresponding to RuO2 peaks (RuO2 powders and RuO2 ALD film) that reported previously to confirm the high quality of RuO2 growth via atomic layer deposition.2 The green curve gives the signal from quartz substrates.
1
In Figure S2, we show the X-ray diffraction of ALD grown RuO2 film. The RuO2(110), RuO2(101) and RuO2(211) diffraction peaks are shown in XRD theta-2 theta measurement that confirms the poly-crystallinity of deposited RuO2 film.2-3 The low signal is due to very small amount of RuO2 (20 nm) deposited on the substrates.
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We further utilize transmission electron microscopy to image the core-shell RuO2@MWCNT fabricated by ALD. The high resolution TEM image of RuO2 on MWCNT shown in Figure S3(a) resolves the crystal plane of RuO2 grain that agrees with previous XRD data to confirm the crystallinity of as-prepared RuO2 film. In Figure S3(b), we show the energy-dispersive x-ray spectrum (EDX) of the core-shell structure. C, Ru and O are the main elements detected in EDX spectrum.
3
Electrochemical Cycling Behavior In Figure S4 (a), we show that the first discharge capacities of both bare RuO2 and LiPONprotected RuO2 electrodes are higher than the theoretical capacity of RuO2 (806 mAh/g), with current density of 100mA/g. We attribute the additional capacity to electrolyte decomposition on the domains of bare MWCNTs, leading to capacity values that exceed the theoretical values for RuO2 as previously reported.
4
We further show the 1st discharge capacity of LiPON-protected RuO2 electrode with C/20 (~50 mA/g) rate in Fugure S4 (b). We observe higher capacity (at least 20% higher) at both the regions above and below 0.8 V compared with Figure S4 (a). Here we demonstrated that it is clear that the kinetics of electrochemical systems play significant roles on specific capacities. Therefore it is difficult to compare one system to another (with different structures, crystallinities, geometries…etc.) by specific capacities. The possible explanation of partial loss of the capacity obtained above 0.8 V (620 mAh/g instead of previously reported 800 mAh/g by Maier et al.) is attributed to partial thermal lithiation of the RuO2 during the ALD process of LiPON, as
5
demonstrated by the TEM image of the as-prepared sample in Figure S4c (Note: the thickness of LiPON layer decreased as a function of time as exposed to high energy electron beam in TEM). In our work, we provide reliable controlled samples to investigate the effects of LiPON protection layers on conversion electrodes, which is rather relevant to draw the conclusions we have made in the manuscript.
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In Figure S5, we show the specific capacities of MWCNT@RuO2 vs. MWCNT@RuO2@LiPON. The capacities was derived from the weighed mass of electrodes before and after ALD coating of RuO2 on MWCNT. The LiPON protected MWCNT@RuO2 exhibited superior stability of discharged capacity over 50 cycles, in which the capacity close to its theoretical capacity and maintain healthy retention over 50 cycles. In contrast, the capacity of unprotected RuO2 decays fastly in first 20 cycles. (Data shown in Figure S5 started from 2nd cycle)
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Statistics from Multiple Cells The statistical cycling performance is obtained in Figure S6 by averaging the cycling data over multiple cells (5 cells of MWCNT@RuO2@LiPON; 3 cells of MWCNT@RuO2). In Figure S6, we show the averaged and normalized specific capacities of MWCNT@RuO2 (red) and MWCNT@RuO2@LiPON (blue). It is convincing that even under various uncertain factors (sample variations, ALD coating variations, coin cell assembly, room temperature variations) that could be involved in multiple cells, MWCNT@RuO2@LiPON electrodes show superior
8
cycling stability and capacity retention compared with bare MWCNT@RuO2 electrodes statistically.
Self-Discharge Experiment In our system, since we have liquid electrolyte and separator between LiPON-protected RuO2 electrode (working electrode) and Li metal (counter electrode), we don’t expect significant battery self-discharge in the system. In order to show that we further conducted the selfdischarge experiment under conditions that mimic as close as possible to the conditions in the paper published by Talin et al.4 on all-solid-state batteries - namely low current and constant 9
voltage (in fact, our currents are an order of magnitudes higher than the currents in Talin’s paper hence we run the experiment potentiostaticly to avoid need of months of operation). Once the battery is done charging at 2.5 V, we stop the current and take the OCV (open circuit voltage) measurement for additional 8 hours as presented in Figure S7. It is clear that in our system, the self-discharge is negligible (cell potential is maintained and stabilized above 2.32 V for 8 hrs), and the relaxation in voltage is a normal relaxation of the electrochemical system.
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REFERENCES: 1. Hu, L.; Wu, H.; Gao, Y. F.; Cao, A. Y.; Li, H. B.; McDough, J.; Xie, X.; Zhou, M.; Cui, Y., Silicon-Carbon Nanotube Coaxial Sponge as Li-Ion Anodes with High Areal Capacity. Adv. Energy Mater. 2011, 1, 523–527 2. Gregorczyk, K. E.; Kozen, A.C.; Chen, X.; Schroeder, M.A.; Noked, M.; Cao, A.; Hu, L.; Rubloff, G.W., Fabrication of 3D Core–Shell Multiwalled Carbon Nanotube@RuO2LithiumIon Battery Electrodes through a RuO2 Atomic Layer Deposition Process. ACS Nano 2015, 9, 464–473 3. Kim, W. –H.; Park, S. –J.; Kim D. Y.; Kim, H, Atomic Layer Deposition of Ruthenium and Ruthenium-oxide Thin Films by Using a Ru(EtCp)2 Precursor and Oxygen Gas. Journal of the Korean Physical Society, 2009 55, 32∼37 4. Ruzmetov, D.; Oleshko, V. P.; Haney, P. M.; Lezec, H. J.; Karki, K.; Baloch, K. H.; Agrawal, A. K.; Davydov, A. V.; Krylyuk, S.; Liu, Y.; Huang, J. Y.; Tanase, M.; Cumings, J.; Talin, A. A., Electrolyte Stability Determines Scaling Limits for Solid-State 3D Li Ion Batteries. Nano Lett. 2012, 12, 505−511
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