Simultaneously Regulating Lithium Ion Flux and Surface Activity for

Subscriber access provided by EDINBURGH UNIVERSITY LIBRARY | @ http://www.lib.ed.ac.uk

Energy, Environmental, and Catalysis Applications

Simultaneously Regulating Lithium Ion Flux and Surface Activity for Dendrite-free Lithium Metal Anode Xianshu Wang, Zhenghui Pan, Jingchun Zhuang, Guanjie Li, Xiaoyu Ding, Mingzhu Liu, Qiankui Zhang, Youhao Liao, Yuegang Zhang, and Weishan Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b21069 • Publication Date (Web): 10 Jan 2019 Downloaded from http://pubs.acs.org on January 23, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Simultaneously Regulating Lithium Ion Flux and Surface Activity for Dendrite-Free Lithium Metal Anode Xianshu Wang,† Zhenghui Pan,‡ Jingchun Zhuang,† Guanjie Li,† Xiaoyu Ding,‡ Mingzhu Liu,† Qiankui Zhang,† Youhao Liao,†,§ Yuegang Zhang, ‡,‖,* Weishan Li,†,§,* †

School of Chemistry and Environment, South China Normal University, Guangzhou 510006,

China. ‡

i-lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences Suzhou,

Jiangsu 215123 , China. §

Engineering Research Center of MTEES (Ministry of Education), Research Center of BMET

(Guangdong Province), and Key Laboratory of ETESPG (GHEI), South China Normal University, Guangzhou 510006, China. ‖

Department of Physics, Tsinghua University, Beijing100084, China

KEYWORDS: Lithium metal anode; dendrite-free; lithium ion flux; surface activity; polymer cladding

1 ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT

Li dendrite growth due to the uncontrolled Li plating/stripping processes has been being a challenge for the application of Li metal anode in high energy secondary batteries. A novel strategy is proposed in this work to address this issue, which is based on simultaneously regulating Li ion (Li+) flux and Li metal surface activity by a terpolymer cladding that orients the Li+ flux and mitigates the side reactions for Li plating/striping. This cladding provides Li anode with dendritefree surface morphology and enhanced electrochemical performances. A stable cycling of 800 hours and 1400 hours are achieved for Li symmetric cells in carbonate-based and ether-based electrolytes, respectively. As well, the asymmetric Li-LiFePO4 and Li-sulfur cells attain a prolonged cycle lifespan with reduced interfacial resistance after cycling. These performances might be further improved by more delicately designing the polymer structure and assembling the cladding, which might help fulfill the practical applications of Li anode in high energy batteries.

1. INTRODUCTION Since the first commercialized lithium (Li) anode-based primary battery appeared in 1970s, the reversibility of Li plating/stripping had been one of the hottest research topics in the area of electrochemical energy storage. However, this area became inactive during 90’s because it was difficult to solve the Li dendrite growth issue. Currently, ever-growing market demand for nextgeneration high energy secondary batteries, such as Li-sulfur batteries, re-focuses the research interest again on the Li metal anode.1-5 Although much attempts have been devoted to fulfilling 2 ACS Paragon Plus Environment

Page 2 of 29

Page 3 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the rechargeability of Li metal anode, which involve Li-free hosts,6-12 solid-state electrolytes,13-15 electrolyte additives,16-19 artificial interfaces,20-23 and others,24-25 large-scale application of Li metal anode has not been realized up to date. The poor rechargeability of Li metal anode results from the non-uniformity of Li plating/stripping and its intrinsic high chemical activity.26-28 Generally, the convection diffusion of Li+ to interface is a significant determining step for Li deposition. For an uneven electrode surface, the Li+ flux yields a discrepant concentration distribution, especially at some local area. Thus, a seriously non-uniform deposition occurs on Li anode surface, which is the fundamental cause of Li dendrite growth. On the other hand, Li metal is endowed with quite high activity because of its ultralow potential, and thus represents considerably unstable interface with traditional electrolyte.28-29 During Li deposition/dissolution, the breaking and repairing of interfacial layers ineluctably expose Li metal to electrolyte and cause the irreversible consumption of electrolyte, rendering low Coulombic efficiency (CE), capacity fade, and eventually failure of the batteries.30-31 Therefore, it is necessary to develop a strategy that can simultaneously regulate Li+ flux and Li metal surface activity during dynamic Li plating/stripping processes. Several strategies have been proposed to suppress dendrite growth and parasitic reactions of electrolyte by regulating Li+ flux and Li surface activity. Lu’s group fabricated silicate coatings by vapor deposition for protecting the Li surface.32 Archer’s group established a patterned LiF coating on Li metal by magnetron sputtering to stabilize Li surface.23 Wu’s group coated a F-rich interface on Cu foil by using high-polarity poly(vinylidene difluoride) to redistribute Li+ flux.33 However, these strategies either involve a high-cost and complicated procedure such as vapor deposition, or increase the overpotential for Li stripping/plating.



In this work, we propose a new strategy that can simultaneously regulate Li+ flux and Li surface activity by a facile application of an as-synthesized terpolymer cladding, poly(butylmethacrylate-acrylonitrile-styrene) (P(BMA-AN-St)) (Figure S1), onto Li metal surface. This terpolymer exhibits excellent electrochemical stability and mechanical strength. When it was coated on a polyethelene membrane, a stable potential window of -0.5 ~ 4.9 V was achieved, while the fracture strength of the membrane was improved from 91 to 97 MPa.34 Most importantly, this polymer contains various functional groups, which exhibit a binding ability with Li ion (Li+) and Li metal. With these features, dendrite growth and electrolyte side reactions on Li metal are highly suppressed and electrochemical performances of the Li metal anode are significantly improved under the protection of polymer cladding. Charge/discharge tests demonstrate that this cladding not only prolongs the Li plating/stripping lifespan of Li symmetric cells, but also guarantees an enhanced CE for a Li/Cu cell, and improves the capacity retention for asymmetric Li-LiFePO4 and Li-S full cells.

2. RESULTS AND DISCUSSION The Li plating/stripping behaviors on electrodes of the bare Li and the Li with cladding (denoted as Clad Li) are illustrated in Figure 1. Owing to the irregular surface on bare Li, the uncontrollable Li+ flux dominates the cyclic process (Figure 1a). Thus, Li metal suffers from dendrite growth and severe electrolyte decomposition, and fails soon. As illustrated in Figure 1b and c, the polymer in the cladding provides channels for Li+ flux and protects the Li surface via the affinity of its polar groups (C=O and C≡N) with Li+ and Li metal, so that the Li+ flux and Li surface activity is simultaneously regulated, yielding uniform and reversible Li striping/depositing


Page 4 of 29

Page 5 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


processes. Due to the affinity of the polar groups in the polymer chains with Li+ and Li metal, as demonstrated by theoretical calculations below, the polymer chains in the cladding are arranged orderly to form the channels for regulating Li+ flux. Thereby, such a cladding makes it possible to realize dendrite-free surface morphology and prolonged lifespan of Li metal anode for deep cycling. The Clad Li electrode was characterized by Fourier transform infrared spectra (FTIR), Raman and X-ray photoelectron spectroscopy (XPS). The cladding shows some strong characteristic absorption peaks of phenyl bone (1456 cm-1), C=O (1722 cm-1), and C≡N (2241 cm-1) (Figure 2a),34 consistent with the FTIR spectra of P(BMA-AN-St) powder (Figure S2). This result indicates that the terpolymer has been successfully transferred on Li metal surface. The resultant cladding is ~4 μm thick (Figure S3a) and exhibits an ionic conductivity of 4.59 × 10-5 S cm-1 (Figure S3b), which is comparable to those of the polyethylene oxide (PEO)-based polymer solid electrolytes,35-36 but far lower than that of gel polymer electrolytes that have a high ionic conductivity of ~ 10-3 S cm-1.34, 37-40 Therefore, the cladding behaves like solid polymer electrolyte rather than gel polymer electrolyte in which the polymer membrane exhibits a porous structure. In fact, no pores can be observed in the cladding, as shown in the inset of Figure 2f. Swelling might take place on the surface of cladding under the attack from the electrolyte, but less possibly in the cladding. Raman spectra further supports the formation of the cladding on Li surface (Figure S4). With this cladding, no XPS signal linked to Li metal can be detected in the Li 1s spectrum for the Clad Li (Figure 2b). In contrast, the bare Li electrode delivers the signal of Li metal (53.7 eV),32 along with LiOCO2R (55.0 eV) and Li2CO3 (55.5 eV) species.41 This difference in the Li 1s spectrum, together with those differences in the XPS spectra of C 1s, O 1s and N 1s (Figure S5), confirms the successful application of the cladding on Li. As observed by automated laser confocal 5 ACS Paragon Plus Environment


microscopy and SEM, the uneven surface of the bare Li (Figure 2c and e) turns to be smooth after applying the cladding (Figure 2d and f). The polar groups in the cladding exhibit affinity with Li ion and Li metal, which can be confirmed by the calculated binding energy and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels (Figure 3). As shown in Figure 3a, the cladding shows a comparative stability due to the higher LUMO and lower HOMO energy of P(BMA-AN-St) than the solvents. Additionally, the HOMO and LUMO energy level gaps indicate the stability of conjugated compounds.42 The larger the energy level gap is, the less possible change in this conjugation occurs. Therefore, the compounds with larger energy level gaps are more stable. It can be seen from Figure 3a that the monomers that construct the cladding have much wider gaps between HOMO and LOMO than the solvents in electrolyte after binding Li atom, indicating that there is a better electrochemical stability between Li metal and the cladding than electrolyte. This feature of the cladding mitigates the activity of Li metal and suppresses the electrolyte decomposition. The higher binding energies of AN-Li+ and BMA-Li+ demonstrate the cladding possesses a stronger affinity with Li+ than the electrolyte (Figure 3b). With this feature, the cladding can control Li+ flux via the given channels provided by the polar groups (Figure 1c) and ensure the uniform striping/depositing processes. The contribution of the cladding to the regulation of Li+ flux and Li metal surface activity can be confirmed by electrochemical impedance spectroscopy (EIS). Figure 3c presents the EIS of Li symmetric cells after the first cycling, which can be well fitted by the equivalent circuits presented in Figure S6. For the bare Li, Rs, Rf and Rct represent the resistance of electrolyte, solid electrolyte interphase film and charge transfer, respectively. Besides these resistances, the Clad Li has an additional Rc, reflecting the cladding resistance. The Clad Li has a larger electrolyte resistance Rs (7 Ω) than the bare Li (2 Ω), which is 6 ACS Paragon Plus Environment

Page 6 of 29

Page 7 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


associated with the reduced amount of the electrolyte by the taking in of the cladding. Additionally, the Clad Li yields a resistance Rc (221 Ω), and presents a larger charge transfer resistance Rct (140 Ω) due to the presence of this cladding than the bare Li (58 Ω), suggesting that the surface activity of Li metal is mitigated by the cladding. On the other hand, the Clad Li possesses a far smaller Rf (14 Ω) than the bare Li (245 Ω), demonstrating that the electrolyte decomposition on the bare Li can be highly suppressed by the cladding. The unsuppressed electrolyte decomposition will cause successively increasing Rf with cycling, which is detrimental to battery performances.43 Therefore, the cladding is beneficial for Li+ flux on the Li/electrolyte interface. To further verify the regulation of Li metal activity by the cladding, both the bare Li and Clad Li electrodes were exposed to air under 25 oC and 40% humidity. Figure 3d presents the photos of Li surface evolution after the air exposure. Initially, the bare Li presents a reflection of metallic luster, in contrast to the matte color of the Clad Li. The surface color of the Clad Li visually keeps unchanged even after air exposure for 10 min, while the bare Li surface tarnishes immediately after 1 min air exposure due to the formation of lithium-based compounds such nitride, hydroxide and carbonate.44-45 The optical micrographs also confirm the regulation effect of the Li metal surface activity by the cladding (Figure S7). Due to the regulation of Li+ flux and Li metal surface activity, surface morphology of the Clad Li differs significantly with that of the bare Li after cycling (Figure 4a, b). As expected, the surface of bare Li becomes fractured and exhibits a porous structure (Figure 4a), resulting from the parasitic reactions during cycling.5 The existence of a large amount of “dead Li” further enlarges the polarization and deteriorates the performance of Li electrode.32 Under the same cycling condition, the Clad Li preserves a smooth surface (Figure 4b). Therefore, the cladding exhibits its ability to inhibit Li dendrite growth and parasitic reactions. At the enhanced current 7 ACS Paragon Plus Environment


densities of 0.5 and 1.0 mA cm-2 (Figure S8), a dendrite-free surface morphology is still harvested on the Clad Li, while the bare Li surface is covered with arbitrary dendrites together with massive deposits. These deposits are the by-products of electrolyte decomposition, as supported by XPS characterizations (Figure 4c & Figure S9). The species of CO32-, Li2CO3 and C=O in C 1s and O 1s spectra, and LixPOFy and P-O in F 1s and P 2p spectra, related to solvent and salt degradations,27, 46

show higher intensities in bare Li than the Clad Li, verifying the contribution of the cladding to

the suppression of side reactions. Notably, the N 1s signal corresponding to the polar C≡N group (N 1s spectra, 399.8 eV, Figure S9a) in the polymer cladding for the cycled Clad Li is preserved (blue dashed circle in Figure 3c), indicating that this polymer coating is stable, providing a sustained protection for Li metal electrode. To further demonstrate the contribution of the cladding, symmetric cell tests were performed in carbonate-based and ether-based electrolytes (Figure 4d-g, and Figure S10-14). The symmetric cell with the bare Li in carbonate-based electrolyte succumbs to a random voltage oscillation after 280 hours at 0.5 mA cm-2 (only 70 cycles) and a sudden voltage drops at the 81th cycle (Figure 3d), corresponding to the accumulation of electrolyte decomposition products and short circuit, respectively.47-48 For the Clad Li symmetric cell, however, a low voltage hysteresis below 0.1 V is maintained over 800 h. At a current density of 1.0 mA cm-2, a similar improvement can be observed (Figure S10a). Even at a larger Li capacity of 3 mA h cm-2 under a larger current density of 3 mA cm-2 (Figure S11), the desirable stability of Clad Li based symmetric cell is achieved, compared to the fast overpotential increment and short circuit within 100 h for the bare Li symmetric cell, indicating that the Clad Li meets the requirement in practical applications. In ether-based electrolyte, a much improved cycleability can be obtained (Figure 4e) because of the lower reactivity of ether with Li metal.49 The bare Li symmetric cell yields a gradual evolution of 8 ACS Paragon Plus Environment

Page 8 of 29

Page 9 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


plating/stripping overpotential from 26 mV to over 1 V after 1300 hours’ cycling, and then is terminated by short circuit. By comparison, the Clad Li symmetric cell presents a superior electrochemical stability with almost no voltage changes until 1100 hours. At 1.0 mA cm-2 (Figure S12a), the Clad Li symmetric cell also shows a negligible voltage change for 800 h, while unstable and high overpotential occurs for the bare Li cell, confirming that the cladding layer effectively stabilizes Li/electrolyte interface and ensures a durable plating/stripping performance. It should be noted that these excellent performances result from the optimal thickness of the cladding (4μm, Figure S3a). A thinner cladding (about 1 μm) has cracks (Figure S13a) and cannot provide a protection for Li anode, resulting in the increasing overpotential of the cell from 100 h (Figure S13c). On the other hand, a thicker cladding provides a smooth surface (Figure S13b) but increases the interfacial resistance of Li electrode, resulting in the larger overpotential of the cell during cycling (Figure 13c). The Clad Li symmetric cells always possess higher overpotential in the initial cycles than the bare Li cells (Insets in Figure 4d, e, Figure S10b, c and S12b, c), which results from the resistance of the cladding. After multiple cycles, the bare Li symmetric cell stops reversible plating/stripping cycling due to a seriously fluctuated voltage profile, while the Clad Li cell maintains a remarkably symmetric deposition/dissolution profile and a low overpotential. Such a feature can be incarnated by EIS results of the Li symmetric cells in carbonate-based electrolyte (Figure 4f), where the interface resistance (~ 180 Ω) for the Clad Li cell slightly exceeds that of the bare Li cell (~ 145 Ω) at the third cycle. After 100 cycles, however, the bare Li symmetric cell has a larger interface resistance (~ 99 Ω) than Clad Li cell (~ 75 Ω), owing to the accumulation of side reaction products, which plays an obstructive role on Li+ flux.50 CE tests of Li/Cu cells further demonstrate the contribution of the cladding (Figure 4g). The CE of bare Li/bare Cu cell fluctuates at an average 9 ACS Paragon Plus Environment


level of 88% and then rapidly declines to a low level in less than 50 cycles, indicating the interfacial instability of Li/electrolyte and dendrite growth. With the protection of cladding on the Cuelectrode, the CE is improved slightly, but still decays to a low level in 90 cycles. In contrast, the Clad Li/bare Cu cell holds the CE of over 90% and the Clad Li/clad Cu cell shows its CE of over 92% within 100 cycles (Figure 4g). These improved CE values demonstrate the contribution of the cladding. Although, the CE presented in this work is not high enough to reach the best cyclic stability of Li anode,51 it can be improved with auxiliary strategies such as optimizing the electrolyte composition. The Clad Li was further evaluated in the batteries paired with LiFePO4 (LFP, 2.5 mg cm-2) and sulfur (S, 1.4 mg cm-2) cathodes with the addition of 70 μL carbonate- and ether-based electrolyte for each battery, respectively (Figure 5). LFP-based batteries with the bare Li and Clad Li anodes present an indistinctive specific capacity retention in the initial 400 cycles (Figure 5a), which can be explained by the Li-containing feature of LFP cathode whose capacity delivery is hardly affected by the anode under a low Li plating/stripping capacity. However, the difference starts to show up after 400 cycles for the bare Li and Clad Li anodes. The discharge capacity of the bare Li/LFP battery gradually drops to 71.5 mA h g-1 at the 800th cycle, but the Clad Li/LFP battery still keeps a reversible capacity of 90 mA h g-1 under the same cycling conditions. The improved lifespan of LFP/based battery is also confirmed by voltage-capacity curves and voltage hysteresis (Figure S14). Even when matched with LiNi0.8Co0.15Al0.05O2 cathode, the Clad Li anode still provides the cell with good performance (Figure S15). The EIS behavior of Li/LFP batteries at different cycles is similar to that of Li symmetric cells (Figure 5b). Initially, the interfacial resistance of the Clad Li-based battery is relatively higher than that of the bare Li-based battery. After 100 cycles, the situation is reversed, confirming the regulation of Li metal surface activity 10 ACS Paragon Plus Environment

Page 10 of 29

Page 11 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


by the cladding. After hundreds of cycles, the surfaces of the bare Li and Clad Li anodes suffer from different levels of degradation and accumulation of electrolyte decomposition products (Figure 5c, d), where the former is packed with small chalked particles while the latter still shows a reasonably integrated surface. Li/S battery using ether-based electrolyte also exhibits improved performances when the cladding is applied on the Li anode. The CE of the bare Li-S battery is lower than that of the Clad Li-S battery, especially in the initial cycling period (Figure 5g), suggesting that more polysulfides react with Li metal without cladding protection. The Clad Li-S battery has a very slow capacity decaying, with a 53% retention over 600 cycles, compared to 23 % of bare Li/S battery (Figure S16). It can be noted from Figure 5g that, differently from the behavior of LFP-based battery (Figure 5a), the Clad Li/S battery shows lower initial capacity than bare Li/S battery. This phenomenon can be explained by the Li-free feature of S cathode whose capacity delivery is highly related to Li anodes. With the presence of the cladding, the Clad Li has a larger initial interface resistance, leading to the lower initial capacity of Clad Li/S battery. The EIS behavior (Figure 5h) and surface morphology (Figure 5e, f) of the Li-S batteries also confirms the positive effect of the cladding.

3. CONCLUSION In summary, we have demonstrated that the cladding based on a terpolymer with functional groups of C≡N and C=O, poly(butylmethacrylate-acrylonitrile-styrene), is efficient in regulation of Li+ flux and Li surface activity for Li metal anode. With the contribution of the cladding, dendrite growth and electrolyte decomposition are highly suppressed. Consequently, the Li anode 11 ACS Paragon Plus Environment


with cladding exhibits significantly improved long-term cycleability in symmetric cells as well as Li/LiFePO4 and Li/S batteries. As a proof-of-concept study, this simple but efficient strategy on the reasonable regulation of Li+ flux and Li surface activity can enable Li metal chemistry for more durable and higher-safety Li metal batteries with high energy densities.

4. EXPERIMENTAL SECTION Synthesis of polymer. The terpolymer for cladding was synthesized by emulsion polymerization using monomers, butylmethacrylate (BMA), acrylonitrile (AN), and styrene (St) (Figure S1), as our previous report.34 This tempolymer was selected because it contains special functional groups, including the carbonyl in BMA that is compatible to Li metal, the cyan in AN that is stable electrochemically and exhibits highly ionic conductivity, and the phenyl in St that is stable physically. The synthesized polymer and functional groups of the monomers were identified by Fourier transform infrared spectra (FTIR, Bruker Tensor 27). Raman were collected to further notarize the structure of polymer powder on Raman instrument (WITec Apyron automated confocal Raman microscopy) (Figure S17). Battery materials. Li metal chip (diameter = 15.6 mm, thickness = 450 μm) was purchased from Tianjin China Energy Lithium Co. Ltd. Cu current collector was purchased from Shenzhen Kejing Star Technology Co., Ltd. The lithium iron phosphate (LiFePO4) and lithium nickel-cobaltaluminum oxide (LiNi0.85Co0.1Al0.05O2) were supplied by Shenzhen OptimumNano Energy Co., Ltd. Battery-grade electrolytes were purchased from Suzhou Fosai New Material Co., Ltd.


Page 12 of 29

Page 13 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Carbonated-based electrolyte was 1 M lithium hexafiluorophosphate (LiPF6) dissolved in a 1:1:1 (w/w/w) mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC): dimethyl carbonate (DEC)

without

any

additive.

Ether-based

electrolyte

was

1

M

lithium

bis(trifluoromethanesulfonyl)imide (LiTFSI) in a 1:1 (v/v) mixture of 1,3-dioxolane (DOL) and 1, 2-dimethoxyethane (DME) with 1 wt. % lithium nitrate (LiNO3) additive. In this work, the experiments without special remark were executed in carbonate-based electrolyte, excepting for those indicated by ether-based electrolyte. Sulfur composite for sulfur cathode was prepared according to the reference.52 Briefly, 100 mg carbon nanotube (CNT) was dispersed into DI water to form aqueous solution after preoxidization, followed by mixing with aniline (ANI) solution (300 mg ANI dissolved into 0.1 mol L-1 hydrochloride acid) under stirring. Then, the aqueous solution of ammonium persulphate as initiator was added dropwise into the resultant mixture with nitrogen flow under vigorous stirring in ice-water bath overnight. The reaction sediments were collected by filtering and washing with DI and ethanol, then freeze-drying for 24 h to yield a CNT@PANI composite. The as-prepared CNT@PANI composite was mingled with sublimed sulfur (99.9%, Aladdin) by ball-milling. The blend was treated at 155 oC for 10 h and 180 oC for another 12 h through hot melt method in a sealed vessel under argon atmosphere. Finally, the CNT@PANI@S composite was obtained for using in Li-sulfur battery. In this composite, sulfur mass ratio was confirmed by thermal weight loss (Figure S18). Electrode preparations. Li metal foil as control (denoted as bare Li) was cleaned with anhydrous hexane to expose a fresh surface. The polymer powder with 10% mass ratio was dissolved in N, N-dimethylacetamide (DMAc, 99%, aladdin) at ambient temperature under magnetic stirring to form a gel that was coated on cleaned Li metal foil (denoted as Clad Li) or Cu 13 ACS Paragon Plus Environment


foil (denoted as clad Cu). Subsequently, the solvent was removed by evaporation at room temperature overnight in the chamber of Ar-filled glove box (Mbraun), where the moisture and oxygen contents were less than 0.1 ppm. LiFePO4, LiNi0.8Co0.15Al0.05O2 and as-prepared sulfur cathodes were fabricated by using a slurry casting method. Active materials (LiFePO4, LiNi0.8Co0.15Al0.05O2 or sulfur), conductive carbon, and binder were mixed with weight ratio of 8:1:1 to form a homogenous slurry with N-methyl-2pyrrolidone, then casted onto aluminum foil (LiFePO4 and LiNi0.8Co0.15Al0.05O2) or carbon-coated aluminum foil (sulfur) with a doctor blade. All the electrodes were dried vacuum and then cut into disks (diameter = 12 mm). The mass loading for LiFePO4, LiNi0.8Co0.15Al0.05O2 and sulfur were around 2.5, 5.8 and 1.4 mg cm-2, respectively. Characterizations. The clad layer on Li surface and its thickness were confirmed by FTIR and scanning electron microscopy (SEM, FEI 250G), respectively. The sample (clad film) for characterizations was collected from clad Li reacting with DI water. Raman analysis was operated to assure the coverage of complete coating on Li metal anode. The excitation wavelength of laser was fixed at 633 nm. Automated laser confocal microscopy as a selected function of Raman Instrument was used to detect surface status of Li metal before and after polymer cladding and provide three-dimensional optical information of electrodes. X-ray photoelectron spectroscopy (XPS) was conducted on ESCALAB 250 to monitor surface chemistry of Li metal before and after polymer cladding, as well as that after cycling. The morphology of electrode surface was examined via SEM. The cycled electrodes were rinsed with carbonate or ether and dried in a vacuum chamber overnight before analysis. The XPS and SEM samples were prepared in the Ar-filled glove box and transferred to vacuum chamber using transfer vessel.


Page 14 of 29

Page 15 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Electrochemical measurements. All battery tests and Li proof-of-concept studies were performed using CR2025-type coin cells in carbonate- or ether-based electrolyte with Celgard 2400 separator. The electrolyte volume was controlled to 70 μL for each cell. Electrochemical tests were conducted on Land CT2000 battery testers using galvanostatic charging-discharging mode at different current densities. In symmetric Li cells, a capacity was fixed at 1 or 3 mA h cm-2 under a current density of 0.5, 1.0 or 3.0 mA cm-2 for Li striping/depositing in both carbonated- and ether-based electrolytes. The asymmetric Li-LiFePO4, Li-LiNi0.8Co0.15Al0.05O2 and Li-S batteries were cycled at a voltage range of 2.2~4.1, 3.0~4.35 and 1.6~2.7 V (vs. Li/Li+) in carbonate- and ether-based electrolytes, respectively. Specific capacities were calculated with respect to the mass of LiFePO4, LiNi0.8Co0.15Al0.05O2 and S. Electrochemical impedance spectra were collected at open circuit potential (OCP) using an frequency analyzer (Metrohm Autolab/PGSTAT30) in a frequency range from 200 kHz to 10 mHz with an amplitude of 10 mV. Ionic conductivity of polymer cladding was measured by EIS in the symmetric stainless steel cell with casted P(BMAAN-St) membrane. Theoretical calculations. The calculations were performed using the Gaussian 09 package53 to affirm the interaction between Li+ and polymer monomers (AN, BMA), which is an evidence of Li+ being regulated. The equilibrium structures were optimized with the B3LYP in conjunction with the 6-311++G(d) level basis set for Li, C, H, O and N. Polarized continuum models (PCM) were used to investigate the bulk solvent effect (dielectric constant is 20.5). The frequency calculations were performed at the same level to confirm that every optimized structure corresponded to a stationary one. The binding energy was acquired by: E (binding energy) = E (complex) – E (Li+) – E (molecule) (1)



where E (molecule), E (Li+) and E (complex), are the total energy after optimization for isolated solvent molecules (EC, EMC, DEC) or polymer monomers, Li ion and the corresponding Li+ combination with solvent molecules or polymer monomers, respectively. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy level was also calculated by the optimization of P(BMA-AN-St) and the conjugations between solvent molecules or monomers and Li atom.

ASSOCIATED CONTENT Supporting Information The following files are available free of charge on the ACS Publications website at DOI: Additional figures including FTIR, Raman and XPS spectra; optical photos; SEM images; additional electrochemical data. (file type, docx)

AUTHOR INFORMATION Corresponding Authors * E-mail: [email protected] * E-mail: [email protected] ORCID Yuegang Zhang: 0000-0003-0344-8399 16 ACS Paragon Plus Environment

Page 16 of 29

Page 17 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Weishan Li: 0000-0002-1495-4441 Author Contributions All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work is supported by the National Key Research and Development Program of China (Grant Nos. 2018YFB0104000 and 2016YFB0100100), the National Natural Science Foundation of China (Grant Nos. 51471073 and 21433013), and the key project of Science and Technology in Guangdong Province (Grant No. 2017A010106006).

REFERENCES (1) Kim, H.; Jeong, G.; Kim, Y. U.; Kim, J. H.; Park, C. M.; Sohn, H. J. Metallic Anodes for Next Generation Secondary Batteries. Chemical Society Reviews 2013, 42 (23), 9011-9034. (2) Lang, J.; Qi, L.; Luo, Y.; Wu, H. High Performance Lithium Metal Anode: Progress and Prospects. Energy Storage Materials 2017, 7, 115-129. (3) Wang, L.; Zhou, Z.; Yan, X.; Hou, F.; Wen, L.; Luo, W.; Liang, J.; Dou, S. X. Engineering of Lithium-Metal Anodes towards a Safe and Stable Battery. Energy Storage Materials 2018, 14, 22-48.



(4) Shen, X.; Liu, H.; Cheng, X.-B.; Yan, C.; Huang, J.-Q. Beyond Lithium Ion Batteries: Higher Energy Density Battery Systems Based on Lithium Metal Anodes. Energy Storage Materials 2018, 12, 161-175. (5) Lin, D.; Liu, Y.; Cui, Y. Reviving the Lithium Metal Anode for High-Energy Batteries. Nature Nanotechnology 2017, 12 (3), 194-206. (6) Wang, X.; Pan Z.; Wu, Y.; Xu, G.; Zheng, X.; Qiu, Y.; Liu, M.; Zhang, Y.; Li, W. Reducing Lithium Deposition Overpotential with Silver Nanocrystals Anchored on Graphene Aerogel. Nanoscale 2018, 10, 16562-16567. (7) Lu, L.-L.; Ge, J.; Yang, J.-N.; Chen, S.-M.; Yao, H.-B.; Zhou, F.; Yu, S.-H. Free-Standing Copper Nanowire Network Current Collector for Improving Lithium Anode Performance. Nano Letters 2016, 16 (7), 4431-4437. (8) Yang, C. P.; Yin, Y. X.; Zhang, S. F.; Li, N. W.; Guo, Y. G. Accommodating Lithium into 3D Current Collectors with a Submicron Skeleton towards Long-Life Lithium Metal Anodes. Nature Communications 2015, 6, 8058. (9) Zuo, T. T.; Wu, X. W.; Yang, C. P.; Yin, Y. X.; Ye, H.; Li, N. W.; Guo, Y. G. Graphitized Carbon Fibers as Multifunctional 3D Current Collectors for High Areal Capacity Li Anodes. Advanced Materials 2017, 29 (29) 201700389. (10) Raji, A. O.; Villegas Salvatierra, R.; Kim, N. D.; Fan, X.; Li, Y.; Silva, G. A. L.; Sha, J.; Tour, J. M. Lithium Batteries with Nearly Maximum Metal Storage. ACS Nano 2017, 11 (6), 63626369. (11) Wang, X.; Pan, Z.; Wu, Y.; Ding, X.; Hong, X.; Xu, G.; Liu, M.; Zhang, Y.; Li, W. Infiltrating Lithium into Carbon Cloth Decorated with Zinc Oxide Arrays for Dendrite-Free Lithium Metal Anode. Nano Res. 2018, http://doi.org/10.1007/s12274-018-2245-z. (12) Liu, Y.; Lin, D.; Liang, Z.; Zhao, J.; Yan, K.; Cui, Y. Lithium-Coated Polymeric Matrix as a Minimum Volume-Change and Dendrite-Free Lithium Metal Anode. Nature Communications 2016, 7, 10992. (13) Cao, Y.; Meng, X.; Elam, J. W. Atomic Layer Deposition of LixAlyS Solid-State Electrolytes for Stabilizing Lithium-Metal Anodes. ChemElectroChem 2016, 3 (6), 858-863. (14) Luo, W.; Gong, Y.; Zhu, Y.; Fu, K. K.; Dai, J.; Lacey, S. D.; Wang, C.; Liu, B.; Han, X.; Mo, Y.; Wachsman, E. D.; Hu, L. Transition from Superlithiophobicity to Superlithiophilicity of


Page 18 of 29

Page 19 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Garnet Solid-State Electrolyte. Journal of the American Chemical Society 2016, 138 (37), 1225812262. (15) Zhou, W.; Wang, S.; Li, Y.; Xin, S.; Manthiram, A.; Goodenough, J. B. Plating a DendriteFree Lithium Anode with a Polymer/Ceramic/Polymer Sandwich Electrolyte. Journal of the American Chemical Society 2016, 138 (30), 9385-9388. (16) Ding, F.; Xu, W.; Graff, G. L.; Zhang, J.; Sushko, M. L.; Chen, X.; Shao, Y.; Engelhard, M. H.; Nie, Z.; Xiao, J.; Liu, X.; Sushko, P. V.; Liu, J.; Zhang, J. G. Dendrite-Free Lithium Deposition via Self-Healing Electrostatic Shield Mechanism. Journal of the American Chemical Society 2013, 135 (11), 4450-4456. (17) Song, J. H.; Yeon, J. T.; Jang, J. Y.; Han, J. G.; Lee, S. M.; Choi, N. S. Effect of Fluoroethylene Carbonate on Electrochemical Performances of Lithium Electrodes and LithiumSulfur Batteries. Journal of the Electrochemical Society 2013, 160 (6), A873-A881. (18) Lin, Z.; Liu, Z.; Fu, W.; Dudney, N. J.; Liang, C. Phosphorous Pentasulfide as a Novel Additive for High-Performance Lithium-Sulfur Batteries. Advanced Functional Materials 2013, 23 (8), 1064-1069. (19) Li, W.; Yao, H.; Yan, K.; Zheng, G.; Liang, Z.; Chiang, Y. M.; Cui, Y. The Synergetic Effect of Lithium Polysulfide and Lithium Nitrate to Prevent Lithium Dendrite Growth. Nature Communications 2015, 6, 7436. (20) Xu, R.; Zhang, X.-Q.; Cheng, X.-B.; Peng, H.-J.; Zhao, C.-Z.; Yan, C.; Huang, J.-Q. Artificial Soft-Rigid Protective Layer for Dendrite-Free Lithium Metal Anode. Advanced Functional Materials 2018, 28 (8), 1705838. (21) Trinh, N. D.; Lepage, D.; Ayme-Perrot, D.; Badia, A.; Dolle, M.; Rochefort, D. An Artificial Lithium Protective Layer that Enables the Use of Acetonitrile-Based Electrolytes in Lithium Metal Batteries. Angewandte Chemie International Edition 2018, 57 (18), 5072-5075. (22) Li, N. W.; Yin, Y. X.; Yang, C. P.; Guo, Y. G. An Artificial Solid Electrolyte Interphase Layer for Stable Lithium Metal Anodes. Advanced Materials 2016, 28 (9), 1853-1858. (23) Fan, L.; Zhuang, H. L.; Gao, L.; Lu, Y.; Archer, L. A. Regulating Li deposition at artificial solid electrolyte interphases. Journal of Materials Chemistry A 2017, 5 (7), 3483-3492. (24) Mayers, M. Z.; Kaminski, J. W.; Miller, T. F. Suppression of Dendrite Formation via Pulse Charging in Rechargeable Lithium Metal Batteries. The Journal of Physical Chemistry C 2012, 116 (50), 26214-26221. 19 ACS Paragon Plus Environment


(25) Zhang, D.; Zhou, Y.; Liu, C.; Fan, S. The Effect of the Carbon Nanotube Buffer Layer on the Performance of a Li Metal Battery. Nanoscale 2016, 8 (21), 11161-11167. (26) Liu, W.; Lin, D.; Pei, A.; Cui, Y. Stabilizing Lithium Metal Anodes by Uniform Li-Ion Flux Distribution in Nanochannel Confinement. Journal of the American Chemical Society 2016, 138 (47), 15443-15450. (27) Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H. A Short Review of Failure Mechanisms of Lithium Metal and Lithiated Graphite Anodes in Liquid Electrolyte Solutions. Solid state ionics 2002, 148, 405-416. (28) Odziemkowski, M.; Irish, D. E. An Electrochemical Study of the Reactivity at the Lithium Electrolyte-Bare Lithium Metal Interface. Journal of the Electrochemical Society 1992, 139 (11), 3063-3074. (29) Cheng, X. B.; Zhang, R.; Zhao, C. Z.; Wei, F.; Zhang, J. G.; Zhang, Q. A Review of Solid Electrolyte Interphases on Lithium Metal Anode. Advanced Science 2016, 3 (3), 1500213. (30) Matsuda, S.; Kubo, Y.; Uosaki, K.; Nakanishi, S. Insulative Microfiber 3D Matrix as a Host Material Minimizing Volume Change of the Anode of Li Metal Batteries. ACS Energy Letters 2017, 2 (4), 924-929. (31) Zhang, Y.; Luo, W.; Wang, C.; Li, Y.; Chen, C.; Song, J.; Dai, J.; Hitz, E. M.; Xu, S.; Yang, C.; Wang, Y.; Hu, L. High-Capacity, Low-Tortuosity, and Channel-Guided Lithium Metal Anode. Proceedings of the National Academy of Sciences of the United States of America 2017, 114 (14), 3584-3589. (32) Liu, F.; Xiao, Q.; Wu, H. B.; Shen, L.; Xu, D.; Cai, M.; Lu, Y. Fabrication of Hybrid Silicate Coatings by a Simple Vapor Deposition Method for Lithium Metal Anodes. Advanced Energy Materials 2018, 8 (6), 1701744. (33) Luo, J.; Fang, C.-C.; Wu, N.-L. High Polarity Poly(vinylidene difluoride) Thin Coating for Dendrite-Free and High-Performance Lithium Metal Anodes. Advanced Energy Materials 2018, 8 (2), 1701482. (34) Huang, W.; Liao, Y.; Li, G.; He, Z.; Luo, X.; Li, W. Investigation on Polyethylene Supported Poly(butyl methacrylate-acrylonitrile-styrene) Terpolymer Based Gel Electrolyte Reinforced by Doping Nano-SiO2 for High Voltage Lithium Ion Battery. Electrochimica Acta 2017, 251, 145154.


Page 20 of 29

Page 21 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(35) Sun, C.; Liu, J.; Gong, Y.; Wilkinson, D. P.; Zhang, J. Recent Advances in All-Solid-State Rechargeable Lithium Batteries. Nano Energy 2017, 33, 363-386. (36) Xue, Z.; He, D.; Xie, X. Poly(ethylene oxide)-Based Electrolytes for Lithium-Ion Batteries. Journal of Materials Chemistry A 2015, 3 (38), 19218-19253. (37) Chen, T.; Liao, Y.; Wang, X.; Luo, X.; Li, X.; Li, W. Investigation on High-Safety Lithium Ion Battery Using Polyethylene Supported Poly(Methyl Methacrylate-Acrylonitrile-Butyl Acrylate) Copolymer Based Gel Electrolyte. Electrochimica Acta 2016, 191, 923-932. (38) Luo, X.; Liao, Y.; Xie, H.; Zhu, Y.; Huang, Q.; Li, W. Enhancement of Cyclic Stability for High Voltage Lithium Ion Battery at Elevated Temperature by Using Polyethylene-Supported Poly(Methyl-Methacrylate-Butyl Acrylate-Acrylonitrile-Styrene) Based Novel Gel Electrolyte. Electrochimica Acta 2016, 220, 47-56. (39) Liao, Y.; Chen, T.; Luo, X.; Fu, Z.; Li, X.; Li, W. Cycling Performance Improvement of Polypropylene Supported Poly(Vinylidene Fluoride-co-Hexafluoropropylene)/Maleic AnhydrideGrated-Polyvinylidene Fluoride Based Gel Electrolyte by Incorporating Nano-Al2O3 for Full Batteries. Journal of Membrane Science 2016, 507, 126-134. (40) Sun, P.; Liao, Y.; Luo, X.; Li, Z.; Chen, T.; Xing, L.; Li, W. The Improved Effect of Codoping with Nano-SiO2 and Nano-Al2O3 on the Performance of Poly(Methyl MethacrylateAcrylonitrile-Ethyl Acrylate) Based Gel Polymer Electrolyte for Lithium Ion Batteries. RSC Advances 2015, 5 (79), 64368-64377. (41) Zheng, J.; Yan, P.; Cao, R.; Xiang, H.; Engelhard, M. H.; Polzin, B. J.; Wang, C.; Zhang, J.-G.; Xu, W. Effects of Propylene Carbonate Content in CsPF6-Containing Electrolytes on the Enhanced Performances of Graphite Electrode for Lithium-Ion Batteries. ACS Applied Materials & Interfaces 2016, 8 (8), 5715-5722. (42) Xing, L.; Zheng, X.; Schroeder, M.; Alvarado, J.; von Wald Cresce, A.; Xu, K.; Li, Q.; Li, W. Deciphering the Ethylene Carbonate-Propylene Carbonate Mystery in Li-Ion Batteries. Accounts of chemical research 2018, 51 (2), 282-289. (43) Waag, W.; Käbitz, S.; Sauer, D. U. Experimental Investigation of the Lithium-Ion Battery Impedance Characteristic at Various Conditions and Aging States and Its Influence on the Application. Appl. Energy 2013, 102, 885-897. (44) Sun, Y.; Li, Y.; Sun, J.; Li, Y.; Pei, A.; Cui, Y. Stabilized Li3N for Efficient Battery Cathode Prelithiation. Energy Storage Materials 2017, 6, 119-124. 21 ACS Paragon Plus Environment


(45) Zhao, J.; Zhou, G.; Yan, K.; Xie, J.; Li, Y.; Liao, L.; Jin, Y.; Liu, k.; Hsu, P. -C.; Wang, J.; Cheng, H. -M.; Cui, Y. Air-Stable and Freestanding Lithium Alloy/Graphene Foil as An Alternative to Lithium Metal Anodes. Nature Nanotechnology 2017, 12, 993-999. (46) Xu, K. Electrolytes and Interphases in Li-Ion Batteries and Beyond. Chemical Reviews 2014, 114 (23), 11503-618. (47) Lu, Q.; He, Y.-B.; Yu, Q.; Li, B.; Kaneti, Y. V.; Yao, Y.; Kang, F.; Yang, Q.-H. DendriteFree, High-Rate, Long-Life Lithium Metal Batteries with a 3D Cross-Linked Network Polymer Electrolyte. Advanced Materials 2017, 29 (13), 1604460. (48) Hu, Z.; Zhang, S.; Dong, S.; Li, W.; Li, H.; Cui, G.; Chen, L. Poly(ethyl α-cyanoacrylate)Based Artificial Solid Electrolyte Interphase Layer for Enhanced Interface Stability of Li Metal Anodes. Chemistry of Materials 2017, 29 (11), 4682-4689. (49) Park, M. S.; Ma, S. B.; Lee, D. J.; Im, D.; Doo, S. G.; Yamamoto, O. A Highly Reversible Lithium Metal Anode. Scientific Reports 2014, 4, 3815. (50) Chen, K.-H.; Wood, K. N.; Kazyak, E.; LePage, W. S.; Davis, A. L.; Sanchez, A. J.; Dasgupta, N. P. Dead Lithium: Mass Transport Effects on Voltage, Capacity, and Failure of Lithium Metal Anodes. Journal of Materials Chemistry A 2017, 5 (23), 11671-11681. (51) Qian, J.; Adams, B. D.; Zheng, J.; Xu, W.; Henderson, W. A.; Wang, J.; Bowden, M. E.; Xu, S.; Hu, J.; Zhang, J.-G. Anode-Free Rechargeable Lithium Metal Batteries. Advanced Functional Materials 2016, 26 (39), 7094-7102. (52) Wang, J.; Cheng, S.; Li, W.; Li, Jia, L.; Xiao, Q.; Hou, Y.; Zheng, Z.; Li, H.; Zhang, S.; Zhou, L.; Liu, M.; Lin, H.; Zhang, Y. Robust Electrical “Highway” Network for High Mass Loading Sulfur Cathode. Nano Energy 2017, 40, 390-398. (53) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; 22 ACS Paragon Plus Environment

Page 22 of 29

Page 23 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision A, Gaussian, Inc, Wallingford, CT, 2009.



Figure 1. Schematic illustrations on Li repeated plating/stripping (a) without regulation, where lithium dendrite forms and the parasitic reactions of electrolyte occur, and (b) with the regulation of P(BMA-AN-St) cladding on lithium ion flux and lithium metal surface activity. (c) The local magnified view on the contribution of the cladding.


Page 24 of 29

Page 25 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. (a) FTIR spectrum of the polymer cladding on Li metal surface. (b) Li 1s spectra of Li metal with and without polymer cladding by XPS. The three-dimensional mappings of Li metal surface (c) without and (d) with clad layer from automated laser confocal microscopy. SEM images of Li metal (e) without and (f) with clad layer.



Figure 3. (a) Frontier molecular orbital energies and LUMO-HOMO energy level gaps of EC-Li, EMC-Li, DEC-Li, AN-Li, BMA-Li and P(BMA-AN-St), together with their corresponding optimized structure and molecular orbital diagrams. (b) Binding energies of polymer monomers (AN, BMA) and solvent molecules (EC, EMC, DEC) with Li ion. (c) Electrochemical impedance spectra of Li symmetric cell with (red) and without (black) clad layer after 1st cycling. The inset presents the various resistances obtained by fitting. (d) Digital images of lithium foil with and without clad layer exposed to air at 25 °C and 40% humidity. The diameter of lithium foil is 15.6 mm.


Page 26 of 29

Page 27 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. Surface information after cycling and electrochemical performance for lithium metal electrodes. SEM images of Li metal surface (a) without and (b) with clad layer after cycling in Li symmetric cells at a current density of 0.25 mA cm-2 with a Li capacity of 1.0 mA h cm-2. (c) XPS analysis of cycled Li metal electrodes with and without clad layer. The voltage profiles of clad Li symmetric cell in (d) carbonate-based and (e) ether-based electrolyte at 0.5 mA cm-2 with Li plating/stripping capacity of 1.0 mA h cm-2. (f) Electrochemical impedance spectra of Li symmetric cell in carbonate-based electrolyte after 3 and 100 cycles. (g) Coulombic efficiency (CE) of Li/Cu cells with and without polymer-cladding in ether-based electrolyte at 0.5 mA cm-2 with the plating/stripping capacity of 1.0 mA h cm-2.



Figure 5. Electrochemical performance of rechargeable lithium metal batteries. (a) The galvanostatic cycling performance of Li-LiFePO4 (LFP) batteries at 1 C rate in a voltage range from 2.2 to 4.1 V after the three formation cycles. (b) The EIS comparison of Li-LFP batteries before cycling, after 3 and 100 cycle at 1 C rate. SEM images of (c, e) bare Li and (d, f) clad Li anodes after cycling in Li-LFP and Li-S batteries, respectively. (g) The galvanostatic cycling performance of Li-S batteries at 0.5 C rate in a voltage range from 1.6 to 2.7 V after the two formation cycles. (h) The EIS behavior of Li-S batteries before cycling, after 2 and 100 cycle at 0.2 C rate.


Page 28 of 29

Page 29 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table of Contents Graphical and Synopsis


Simultaneously Regulating Lithium Ion Flux and Surface Activity for

Recommend Documents