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A Functional Separator Coated with Sulfonated SEBS to Synergistically Enhance the Electrochemical Performance and Anti-self-discharge Behavior of Li-S Batteries Kai Yang, Lei Zhong, Yudi Mo, Rui Wen, Min Xiao, Dongmei Han, Shuanjin Wang, and Yuezhong Meng ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.8b00275 • Publication Date (Web): 22 May 2018 Downloaded from http://pubs.acs.org on May 23, 2018

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ACS Applied Energy Materials

A Functional Separator Coated with Sulfonated SEBS to Synergistically Enhance the Electrochemical Performance and Anti-self-discharge Behavior of Li-S Batteries Kai Yang, Lei Zhong, Yudi Mo, Rui Wen, Min Xiao, Dongmei Han, Shuanjin Wang*, Yuezhong Meng*

The Key Laboratory of Low-carbon Chemistry & Energy Conservation of Guangdong Province / State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, PR China *Corresponding author, Tel: +86 20 84114113; E-mail: [email protected] (Y. Z. Meng) or [email protected] (S. J. Wang).

Abstract Lithium sulfur battery is highly appealing for energy storage due to its high theoretical capacity and energy density. Nevertheless, as one of the pivotal problems, the shuttling of soluble polysulfide intermediates hinders its practical application. In this work, we employ an electronic conductive carbon material and a lithium ion conductive block polymer (lithium sulfonated poly(styrene-ethylene-butylenestyrene), Li+-SSEBS) to fabricate a functional separator by a simple coating method. The functional coating on the PP separator exhibits excellent electronic conductivity for reactivating the active materials, good lithium ion conductivity for facilitating lithium ion transport, and great ionic selectivity for the suppressing polysulfide shuttle. With this separator, the battery shows a high initial discharge capacity of 1066 mAh g-1 and excellent capacity retention of 762.7 mAh g−1 after 350 cycles at 0.5 C. It also

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exhibits excellent rate performance with a high capacity of 750 mAh g-1 at 2 C and good recovery capability. Furthermore, a correction strategy has been adopted to investigate the anti-self-discharge behavior of Li-S battery, which is more reasonable and precise than reported method. The results demonstrate that the SEBS based functional separator can endow the enhanced electrochemical performance and anti-self-charge capability of Li-S battery.

Keywords:

Lithium

sulfonated

poly(styrene-ethylene-butylene-styrene)

(Li+-SSEBS), functional separator, ionic selectivity, electronic conductivity, lithium sulfur batteries

Introduction With the limitation of energy density, the commercialized lithium-ion batteries (LIBs) are unable to meet the ever-increasing specific energy requirements of electric vehicles and large-scale smart devices.1-3 lithium-sulfur (Li-S) batteries (with a theoretical energy density of 2600 Wh kg−1) have five times higher theoretical energy density than the commercialized LIBs and achieved over 500 Wh kg−1 of weight energy density in reality with low cost.4,5 Combined with non-toxic as well as environmental friendliness, Li-S batteries become one of the most promising next-generation high energy density rechargeable devices.6 Nevertheless, the commercial application of Li-S batteries still has been hindered by several serious problems. Recent works have been focused on solving the inherent insulation of sulfur,1,7 rapid capacity fade, self-discharge due to the polysulfides shuttling,8,9 and passivation and dendrite formation of the lithium metal anode.5,10,11 Across the board, the polysulfide shuttle is one of the principal factors for passivating the metal lithium


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anode and causing the poor Coulombic efficiency and cycling stability of Li–S batteries.12-14 In recent years, great efforts have been made in designing electrode host material and innovating cell configuration to alleviate the polysulfide shuttle.15-20 As an indispensable component of the battery, separator serves as an electrical insulator for avoiding internal short-circuit and transporting channels for lithium ions.12,21 In Li-S battery, the separator can function as an ion transporting selector for inhibiting polysulfides migration without decreasing the conductivity of lithium ions.21-24 The ion transporting selectivity of lithium ion and polysulfides is very important for improving the performances of Li-S batteries. Thus, it has been attracting much attention to modify the commercial separator with the functional materials. Various strategies have been tried to develop a modified separator for suppressing the migration of polysulfides and providing convenient transportation of lithium ion. Carbon materials coated separator has been reported firstly to confine the polysulfides in the cathode region by Nazar L. F. and her co-workers.25 Along this line, various of carbon materials, such as graphene,23,26,27 mesoporous carbon,28 carbon nanotube,29,30 activated carbon particles31 and their hybrids,32 have been widely used to modify separator for polysulfides’ trapping. The electron conductive carbon material coating layer on separator can trap polysulfides in some extent and then reactivate the active intermediates as a second current collector. Arumugam M. gave a concept of “polysulfide-trapping” for stabilizing the active material and activating the bulk sulfur cores by boron-doped multi-walled carbon nanotube or layer-by-layer modified



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separator.30,33 Coating ceramic or metal oxide onto PP separator is an effective way of suppressing the polysulfide migration by physical absorption. The inorganic compounds, such as Al2O3,34,35 SiO2,36 BaTiO3,14 and Ti3C237 have been used to confine polysulfides and improve thermal stability of PP separator by mixing, doping, coating and so on. The polar negative charge groups, for example, -SO3- and -COO-, can suppress the migration of soluble polysulfides by Coulombic repulsion, and their ion transporting channels can facilitate lithium ion transporting simultaneously.38-40 The separators modified by materials with negative charges have proved effective in improving electrochemical performance of Li-S batteries. Polymer materials with -SO3- negative groups, such as Nafion23 and sulfonated polystyrene (PSS),38,41,42 have been reported to modify polyolefin separator. As an amorphous polymer with rubber property

and

high

molecular

weight,

sulfonated

poly(styrene-ethylene

-butylene-styrene) (SSEBS) has been used as a binder to improve the electrochemical performance of active materials of cathode in redox systems.43 The chemical formula and synthetic scheme of SSEBS was presented in Figure S1. To our knowledge, SSEBS has not been used to enhance the electrochemical performance of Li-S battery. The proton of the sulfonic acid group in SSEBS can be exchanged into Li+ and the resulting Li+-SSEBS polymer possesses lithium ion transporting ability as a single-ion conductor. Compared with other sulfonated polymers, Li+-SSEBS is low cost and exhibits excellent thermal stability, good mechanical properties and good lithium ion transporting ability.


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In this study, we propose a new composite separator by coating a mixture of Li+-SSEBS and carbon material (Super P) onto a commercial polyolefin separator. The Li+-SSEBS/Super P coating is expected to restrain the “polysulfide shuttle effect” effectively. The soft polyolefin chain of Li+-SSEBS can improve the miscibility, interface contact affinity of the coating layer with polyolefin separator. The negative charges of -SO3- groups can suppress the migration of soluble polysulfides by Coulombic repulsion effect, but allow Li+ transport. The conductive carbon (Super P) can increase the electronic conductivity and adsorb the polysulfide intermediates for reactivating redox-active intermediates, and at the same time suppressing polysulfide shuttling. Li-S battery using this functional separator delivers an initial capacity of 1066 mAh g-1 at 0.5 C and still retains a capacity of 762.7 mAh g−1 after 350 cycles. Furthermore, to evaluate the capability of the functional separator to restrain polysulfide shuttle, we present a correction method based on Hart’ method44 to investigate the self-discharge behavior of Li-S batteries. The results show that such Li+-SSEBS based coating can act as a functional layer of separator to enhance the electrochemical performance and anti-self-discharge behavior of Li-S batteries.

Experimental section 2.1 Synthesis of lithium sulfonated poly(styrene-ethylene-butylene-styrene) (Li+-SSEBS) Li+-SSEBS was synthesized by the modified method of the reference.45 2.0 g of SEBS (Taipol@SEBS 6150) and 100 mL of 1, 2-dichloroethane (DCE) and



cyclohexane (v/v = 7:1) were charged into a three-neck reactor and stirred continuously for several hours under dry N2 atmosphere at 50 oC to get a transparent solution (labelled as solution A). Meanwhile, 4.8 mL of acetic anhydride and 17 mL of DCE were added into a sealed N2 purged round bottom flask and kept below 0 oC, and then 1.6 mL of 96 % sulfuric acid was added while the temperature was maintained below 5 oC to a get acetic sulfate solution (labeled as solution B). After 30 min stirring, solution B was added into solution A under continuous stirring at 50 oC for 3 h, afterwards, 30 mL of isopropanol was added to end the reaction. After cooling down to room temperature, 100 mL of deionized water was added. The mixture was isolated by evaporating DCE and isopropanol. The residues were dialyzed in deionized water several times till PH=7, and then in 1 M LiOH aqueous solution for 24 h to get Li+-SSEBS polymer. After washing with water till PH=7 and dried at 50 o

C, Li+-SSEBS was obtained as a brown solid. The sulfonation degree of Li+-SSEBS

was confirmed by a titration method and controlled at ~ 47%.45-47 2.2 Fabrication of Li+-SSEBS modified separator (Li+-SSEBS-mSP) The modified separator (mSP) was fabricated by coating mixed slurry of Li+-SSEBS and Super P in NMP onto one side of the commercial PP separator. In a typical procedure, 0.1 g Li+-SSEBS was dissolved in 10 mL N-methyl-2-pyrolidone (NMP), and then 0.9 g super P (TIMCAL) was added. The mixture was stirred for several hours to form the homogeneous slurry. This slurry was coated onto one side of Celgard 2400 separator by a doctor blade, and dried in a vacuum oven at 50 oC for 12 h. After drying, the modified separator was cut into disks with a diameter of 19 mm


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before used and the loading of the coating layer was controlled at 0.24~0.28 mg cm-2. The coating layer with different Li+-SSEBS content (10 wt.%, 15 wt.%, 20 wt.% and 30 wt.%) was prepared and the corresponding modified separators are termed as Li+-SSEBS10-mSP, Li+-SSEBS15-mSP, Li+-SSEBS20-mSP and Li+-SSEBS30-mSP in turns. As a control separator, the separator with the coating layer of PVDF and Super P was also made by the same method and the sample with 15 wt.% PVDF is named as PVDF15-mSP. 2.3 Preparation of the Li2S6 solution 1 M of Li2S6 solution for diffusion test was prepared by dissolving lithium sulfide (Li2S) and sublimed sulfur (molar ratio of 1:5) into 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) (v/v = 1:1) and stirred at 60 oC for 24 h under argon atmosphere.48 2.4 Fabrication of sulfur cathode A mixture of 70 wt.% sublimed sulfur (99. 5%, Aladdin, China), 20 wt.% Super P, and 10 wt.% polyvinylidene fluoride (PVDF, Arkema HSV900) was mixed in NMP after grinding by a mortar, and stirred for 24 hours to form a uniform slurry. The obtained slurry was coated onto an aluminum foil using a doctor blade, dried at 50 °C for 24 h in the oven, and then punched into disks with a diameter of 14 mm. The sulfur loadings of the cathodes are 1.1-1.3 mg cm-2 and used to assemble Li-S cells. All the capacity values were calculated on the basis of sulfur mass. 2.5 Cell assembly and electrochemical measurements The standard 2025 coin-type cells were assembled inside an argon-filled glove



box by employing sulfur cathode, lithium wafers as a node, and different separators. The electrolyte was 1.0 mol L-1 lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.2 mol L-1 LiNO3 in a mixed solvent of DOL and DME (v/v = 1:1). The amount of the electrolyte used in the cell is 22 µL based on 1 mg of sulfur in cathodes. The electrochemical impedance spectroscopy (EIS) was measured on an electrochemical workstation (CHI750E) in the frequency range of 1 MHz to 100 mHz. Cyclic voltammogram (CV) measurement was carried out on CHI750E at a scan rate of 0.1 mV s-1 with a cutoff voltage of 1.7-2.8 V at 25 oC. The charge and discharge performances were tested in galvanostatic mode within a voltage range of 1.7-2.8 V using a Land multichannel battery system.

Results and discussion As we known, poly(styrene-ethylene-butylene-styrene) (SEBS) is a block copolymer containing a polystyrene block, whose phenyl ring can be attached with sulfonic groups by sulfonation reaction. Here, Li+-SSEBS was synthesized using acetic sulfate as the mild sulfonating agent47,49 followed by transformation from proton (H+) into Li+ form (Figure S1). The FT-IR spectra of sulfonated SEBS (SSEBS) and pristine SEBS are shown in Figure 1a. The broad adsorption peak at 1050-1250 cm-1 of SSEBS belongs to the overlap with S-O symmetric and asymmetric stretching vibration of sulfonic acid groups (1090 cm-1 and 1032 cm-1).45,47 These provide evidence of the successful introduction of sulfonic groups onto SEBS. The sulfonation degree is easy to be analyzed by the traditional titration method.47 Because the


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decomposition of sulfonic acid group start at about 250 oC, the content of -SO3− can be investigated by thermal gravimetric analysis (TGA).38, 50-51 As presented in Figure S2, the mass loss in the temperature of 200 oC-400 oC is about 9 wt.%, which is close to the sulfonation degree determined by traditional titration method.

Figure 1 FT-IR spectra of SEBS and SSEBS (a), SEM and EDS results of Li+-SSEBS15-mSP: all elements scanning morphology of the surface (b) and the corresponding elemental mapping images of S and O (c).



Figure 2 SEM images of pristine separator (a) and Li+-SSEBS-mSP separators with different Li+-SSEBS contents (b-e) and (f) cross-section of Li+-SSEBS15-mSP. The insets (a-e) are digital photographs of different separators.

Li+-SSEBS is soluble in aprotic organic solvents, such as NMP, so its slurry with carbons (Super P) can be easily coated onto the surface of PP separator using a blade method. The peaks of O and S elements in the EDX spectrum confirm the existence of SO3- group (Figure 1b). Elemental mapping of the coating separator shows the uniform distribution of sulfur and oxygen (Figure 1c), which proves the well dispersion of Li+-SSEBS and Super P on the surface of the separator. The coatings with different Li+-SSEBS contents were prepared for pristine PP separator. The thickness of the coating layer is ~8 µm (Figure 2f) and the loadings of the coating layer are 0.24~0.28 mg cm-2. As shown in Figure 2a, the pristine PP separator shows plenty of uniform and abundant pores on the surface. After coated with a mixture of


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Li+-SSEBS and super P, the pores on the surfaces of their pristine separators have been covered. It can be clearly seen from Figure 2b-f that Super P carbon nanoparticles and Li+-SSEBS constitute a uniform interweaved structure on the surfaces of

Li+-SSEBS-mSP

separators.

Furthermore,

without any

visible

agglomeration was observed in the coating layer. The twisty and nanoscale channel in the coating layer combined with -SO3- groups of Li+-SSEBS are expected to facilitate lithium ion transport and restrain the migration of polysulfides (Sn2-) by Coulombic repulsion between -SO3- and Sn2-.31 With the increase of Li+-SSEBS content, no obvious differences in morphology are observed, except the one with 30% Li+-SSEBS. Li+-SSEBS polymer material in Li+-SSEBS30-mSP forming a continuous dense phase (Figure 2e), which would reduce the porosity and electrical conductivity of the coating layer. To further understand the relationship of the pore structures of these coating layer and the ratio of Li+-SSEBS and Super P, the pore size distribution and pore volume of different separators are all investigated (Figure S3). The results indicate that the coating layers can decrease the pore diameter of PP separator, effectively. Li+-SSEBS and Super P layer could fabricate rich pore structures. With the increase of Li+-SSEBS polymer, the pore volume presents an increasing trend at micropore and mesoporous regions. However, the pore volume distinctly decrease and display a dense phase, when the content of Li+-SSEBS polymer up to 30 wt.%. The conductivity test provides the date of different coating layer, which is significant for a collector and could help explain the electrochemical performance of Li-S batteries (Figure S4).



Figure 3 The Nyquist plots (rest 12 h after assembly and measured at ~2.4 V) (a), discharge/charge profiles at 0.5 C of 10th cycle (b) and cycling performances at 0.5 C(c) of Li-S batteries with Li+-SSEBS-mSP separators

EIS was used to evaluate the conductivity of Li-S batteries with different separators. As presented in Figure 3a, all Nyquist plots of different batteries have a depressed semicircle in the medium-high frequency region corresponding to the charge-transfer resistance (Rct), and a straight inclined line in the low-frequency region corresponding to the ion-diffusion resistance (the Warburg impedance, Wc), which can be allocated to the corresponding equivalent circuit.[50] The charge-transfer resistances of all Li+-SSEBS-mSP separators are smaller than that of the pristine PP separator. The charge transfer resistances of Li+-SSEBS-mSP separators with 10% and 15% of Li+-SSEBS are as low as 60 Ω. The smaller Rct of ACS Paragon Plus Environment

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the modified separators can be attributed to the Li+ transporting ability of Li+-SSEBS polymers. However, with the increase of Li+-SSEBS content, the carbon particles are wrapped by the Li+-SSEBS polymer material, which reduces the porosity and increase the density of the coating layer (Fig 1b-e). As a result, the Rct of Li+-SSEBS-mSP separator increases with the increase of Li+-SSEBS content. The lithium ion diffusion coefficient and lithium ion transference number results provide the ample evidence for the change of Li+ transporting ability in different ratios of Li+-SSEBS and Super P (Figure S5, S6 and Table S1). Furthermore, the discharge-charge curves offer the similar evidence (Figure 3b). With the increase of Li+-SSEBS content, the polarization of the cells increased obviously. The high polarization would lower discharge capacity of battery and deteriorate the capacity retention.1,12 The cycle performances of different cells at 0.5 C for 150 cycles are presented in Figure 3c. The cell with Li+-SSEBS10-mSP delivers the highest discharge capacity of 1131 mA h g-1 at 0.5C, which attributes to the lowest charge-transfer resistance and polarization. However, the cell with Li+-SSEBS15-mSP shows the best capacity retention, and its discharge capacity is higher than that of the battery with Li+-SSEBS10-mSP after 80 cycles. Coulombic efficiencies of all cells are about 99% without any visible difference. Therefore, Li+-SSEBS15-mSP is selected for further investigations.



Figure 4 Demonstration of the separators to suppress polysulfide diffusion: mechanism illustration (a, b and c) and the optical photographs of the diffusion test (Pristine PP separator (a1-2), PVDF15-mSP (b1-2) and Li+-SSEBS15-mSP (c1-2). As evidence, the polysulfides permeability of different separators was investigated via a visible test.51,52 As displayed in Figure 4 and Figure S7, the outer large vial contained a blank electrolyte solution (DME/DOL 1:1, v: v) and the inner


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small vial contained an electrolyte solution with 1 M Li2S6 in DME/DOL. Different separators were set as a septum under the open cap of the small vial. The diffusion behavior of polysulfides was recorded by a digital camera. During the testing time period, the Li2S6 in the small vial diffused into the large vial and the color of the large vial turned into yellow and then dark. However, after the same testing time, the color in the large vial for the set up with Li+-SSEBS15-mSP changed more slowly than those of PVDF15-mSP and pristine PP separators. As expected, Li+-SSEBS-mSP exhibits the best ability of suppressing the diffusion of polysulfides among them. The polysulfides diffusion mechanisms through different separators are illustrated in Figure 4a-c. The best capability of suppressing polysulfides shuttle for Li+-SSEBS15-mSP could be ascribed to the twisty porous structure and the Coulombic repulsion effect from -SO3- negative charges of polymer. These results helped to understand the good electrochemical performances of Li-S batteries with Li+-SSEBS15-mSP.



Figure 5 Electrochemical performance test: cyclic voltammetry curves (a), cycling performances at 0.2 C for 200 cycles (b), discharge-charge profiles of the 10th cycle at 0.5 C (c) and rate performances (d) of different Li-S batteries; cycling performance of Li-S battery with Li+-SSEBS15-mSP at 0.5 C for 350 cycles(e).

In order to determine the effect of Li+-SSEBS in the coating on the performance of Li-S battery, the separator PVDF15-mSP without sulfonic groups was also fabricated as a control as well as pristine PP separator. From the CV curves present in Figure 5a, in the cathodic scan, the reduction of elemental sulfur to lithium


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polysulfides (Li2Sx, 4 < x < 8) near 2.30 V and lithium polysulfides to insoluble Li2S2 and Li2S (2.00 V) were both detected.23, 55 There is a 0.07 V shift from 2.01 to 1.94 V in the cells with Li+-SSEBS15-mSP comparing to that of the cells with pristine PP separators. However, in the anodic scan, the peak shift is 0.09 V to 2.32 V (2.41 V). The peak positions of cells with Li+-SSEBS15-mSP and PVDF15-mSP are almost same, and their peak currents are higher than that of PP separator, indicating their faster redox reaction kinetics. These demonstrate that the carbons in coating layer decreased the polarization of the batteries, which can also be confirmed by the discharge-charge curves and EIS measurements (Figure 5c and Figure 6). As a result, the Li-S battery with Li+-SSEBS15-mSP shows a high initial specific capacity of 1233 mAh g-1 at 0.2 C, and maintains 845 mAh g-1 after 200 cycles. It confirms the ability of Li+-SSEBS15-mSP to trap lithium polysulfides. Ascribing to its -SO3- groups, Li+-SSEBS in coating layer can facilitate the transport of Li+ and suppress the shuttle of polysulfides between cathode and anode. Furthermore, Li+-SSEBS15-mSP also shows the best cycling performance at 0.5 C for 200 cycles (Figure S8). These demonstrate that Li+-SSEBS plays a significant role in blocking polysulfides. The rate capabilities of different batteries are exhibited in Figure 5d. The battery with Li+-SSEBS15-mSP shows higher discharge capacities than PVDF15-mSP and pristine PP separator at various current rates. The discharge capacities of Li+-SSEBS15-mSP are 1260, 1180, 1060, 973 and 750 mAh g-1 at rate of 0.1, 0.3, 0.5, 1, and 2 C, respectively. The specific capacity returns to 1048 at 0.5 C, after 32 cycles.



The discharge-charge profiles are shown in Figure S9, which provide further illustration of low polarization at different current densities. For the battery with Li+-SSEBS15-mSP, both the capacity and cycling stability are better than those of other batteries. Batteries with the modified separators have high specific capacities due to the conductive carbon for reducing polarization. The coating layer both with conductive carbon and Li+-SSEBS endows the battery better rate performances due to the synergistic encapsulation of polysulfides by electronic conductivity of Super P and Coulombic repulsion of Li+-SSEBS, as well as the facilitated lithium ion transport. The cycling performance of battery with Li+-SSEBS15-mSP at 0.5 C is shown in Figure 5e. A reversible discharge capacity of 1066 mAh g-1 is obtained after two-cycle activation at 0.05 C. After 350 cycles, the cell still retains a 762.7 mAh g−1 capacity at 0.5 C, revealing its outstanding cycling stability. Furthermore, all the Coulombic efficiencies maintain above 99%. Both Li+-SSEBS polymer with electronegative group and Super P with high electron conductivity play the predominant role in achieving the excellent electrochemical performance. Moreover, a thick cathode with high sulfur loading (3.2 mg cm-2) was also investigated for Li-S battery with Li+-SSEBS15-mSP. As depicted in Figure S10a, after 6 cycles of activation at 0.05-0.1 C, this cell with a high areal sulfur loading still delivers a discharge capacity of 707.7 mAh g−1 at 0.5 C after 100 cycles with high Coulombic efficiency. And the cell with a cathode for practical loading (> 5 mg cm-2) and Li+-SSEBS15-mSP also presents a competitive performance (Figure S10b).


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Figure 6 The Nyquist plots and corresponding equivalent circuits of Li-S batteries with different separators: (a) fresh batteries (rest 12 h after assembly and measured at ~2.4 V) and (b) the batteries at charged states after 50 cycles at 0.5 C (measured at ~2.4 V).

As depicted in Figure 6a and b, EIS measurements of the batteries before and after 50 cycles at 0.5 C were investigated. From the Nyquist plots and equivalent circuits, The ohmic resistance (Re) and the charge-transfer resistances (Rct) of batteries with modified separators are much lower than that of PP separator, indicating that the coating layers provide the faster ion transfer rate and favorable electrical conductivity. After 50 cycles, the charge-transfer resistances (Rct) values of different batteries are all decreased obviously, suggesting the redistribution of active materials in cells. EIS of the battery with PP separator has other small semicircle at middle



frequency region, corresponding to the interface contact resistance (Rs) due to the deposition of more insoluble and insulated polysulfides on the Li surface for control battery.56 However, Rs is not observed for the separators with coating layers. The differences of lithium ion diffusion coefficients and lithium ion transference numbers of various separators could explain the obvious distinction of electrochemical performance (Figure S11, S12 and Table S2). The conductive carbon (Super P) in coating layers can trap the dissolved polysulfides and serve as an additional cathode for the further electrochemical reaction, which contribute to the lower polarization and better electrochemical performance. Combined with Li+-SSEBS for facilitating lithium ion transport and suppressing polysulfide shuttle, the battery exhibits excellent electrochemical performance, as has been noted.

Figure 7 SEM images and EDS results of the Li+-SSEBS15-mSP before cycle (a,b) and after 50 cycles (c,d) at 0.5C


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To investigate the structural stability of the Li+-SSEBS modified separator, the surface morphology and elementary composition of Li+-SSEBS15-mSP is also measured by SEM and EDS test after 50 cycles, as shown in Figure 7. After cycling, the separator was observed directly with any washing treatment. Compared with the fresh separator (Figure 7a), the denser structure of Figure 7c results from the deposition of electrolyte salts and polysulfides. The EDS result could provide the clear evidence. The surface morphology and sulfur element content of lithium anode can be used to evaluate the capacity of trapping polysulfides. As shown in Figure S13, the cell with Li+-SSEBS15-mSP displays the most flat anode surface and the least sulfur content. The result indicates that Li+-SSEBS15-mSP presents the better performance of trapping polysulfides. The unchanged surface morphologies of Li+-SSEBS15-mSP and Li metal anode indicate the structure stability of Li+-SSEBS15-mSP and guarantee the excellent electrochemical performance of batteries during cycling.



Figure 8 Self-discharge performance test of cell with Li+-SSEBS15-mSP at 0.5 C: discharge–charge profiles (interrupted at 2.1 V, a) and (interrupted at different voltages for various batteries, b); discharge profiles of 8th cycle (continuous discharge) and 9th cycle (interrupted at 2.1 V and rest 72 h during discharge) (c); discharge profiles of 8th cycle (continuous discharge) and 9th cycle (interrupted at 2.06 V and rest 72 h during discharge) (d); typical voltage-cycling time profile (interrupted at 2.06 V and rest 72 h during discharge) (e) and discharge capacity-cycle index plots for different separators, giving ∆D upon self-discharge (f).


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The migration of polysulfides across the separator can react with the lithium metal anode and transform into insoluble Li2S2 and Li2S by disproportionation. These would result in the irreversible losses of active materials in the electrolyte and the discharge capacity. Capacity retention has been used mostly to evaluate the cycling performance of Li-S battery and compare the suppressing effect of different materials on polysulfides shuttle effect. However, the long-term cycling test takes more time and the capacity retention has been found not suitable for all materials.44 Nazar’s group has developed a new strategy to investigate the self-discharge behavior of Li-S batteries.44 This method can be used to predict the long-term cycling performance in several days and quickly measure the self-discharge behavior of Li-S batteries. As reported, the concentration of Sn2- in electrolyte is maximal at 2.1 V during the discharge of Li-S battery. So, the 9th discharge was interrupted at 2.1 V (Figure 8a and c) and rested for 72 h. The difference of discharge capacities between 8th and 9th (∆D) was used to evaluate the self-discharge behavior of Li-S batteries. This strategy has been employed and given the similar results.57-59 In fact, the voltage position for the highest concentration of Sn2- can be found in the discharge profile, where the long polysulfides would change into soluble Li2S4 entirely. The viscosity of the electrolyte increases with the increase of the concentration of Sn2- and achieves a maximum value,60 where the discharge voltage declines sharply and display a valley in the curve (position at arrow 1 in Figure 8c). Apparently, the discharge voltage of the highest concentration of Sn2- is different for different materials due to the different polarization of Li-S battery, as presented in Figure 8b. In this work, Li-S batteries



with Li+-SSEBS15-mSP and PVDF15-mSP separators exhibit lower polarization (Figure 8b) than the one with PP separator. Therefore, the interrupt voltage should be set at the “valley” position of the discharge curve, which would provide a more reasonable comparison with self-discharge behavior of different Li-S batteries. The interrupt voltage values were set at 2.06 V for Li+-SSEBS15-mSP (Figure 8b and d) and PVDF15-mSP (Figure 8b), but at 1.96 V for PP separator respectively. The discharge capacity loss rates (∆D) are also used to compare the self-discharge behavior of different batteries. Figure 8c and d show the results of the self-discharge test according to our modified method. The values of ∆D are 96, 126.4 and 192.6 mAh g-1 for batteries with Li+-SSEBS15-mSP, PVDF15-mSP and pristine PP separators, respectively. The loss rate value was defined as ∆D/C8th (C8th is the specific capacity of the 8th discharge).56 The loss rate values of the cells with Li+-SSEBS15-mSP, PVDF15-mSP and pristine PP separator are 8.8 %, 12.3% and 26.4%, respectively. The results indicate that the coating layer with Li+-SSEBS and Super P suppressed polysulfides diffusion and improved the anti-self-discharge behavior of Li-S batteries effectively, which are consistent with the diffusion test of polysulfides (Figure 4). For comparison, the self-discharge test without modification was also done and the interrupt voltages were set at 2.1 V for all batteries as the same with the reference (Figure 8a). The values of ∆′D are 87.7, 113.8 and 137.9 mAh g-1 for Li+-SSEBS15-mSP, PVDF15-mSP and PP separator, in their turns (Figure S14). The capacity loss rate values were obtained by the same formula, as listed in Table S3. Both the values are lower than those obtained


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by the improved test method, suggesting that the concentration of Sn2- did not reach the maximum value at 2.1 V. These demonstrate that the self-discharge method improved by this work is more reasonable and precise than commonly used method. From the above results, we confirm that the coating layer with Li+-SSEBS and Super P can serve as a functional modified layer of the commercial PP separator. This is an effective, facile and low cost strategy for improving electrochemical performance and restraining self-discharge behavior of Li-S batteries.

4. Conclusions In summary, we reported a functional coating layer with Li+-SSEBS and carbon (Super P) for the separator, which enhanced the electrochemical performances and anti-self-discharge behavior of Li-S batteries. The effect of Li+-SSEBS based functional coating can be assigned to the electrical conductivity of Super P, the Li+ transporting ability of Li+-SSEBS polymer, and the Coulombic repulsion effect of negative -SO3- with Sn2-. The ratio of Li+-SSEBS and Super P were investigated in detail for offering a good synergy effect of performance improvement. Li-S battery with

Li+-SSEBS15-mSP

exhibits

excellent

electrochemical

performances.

Furthermore, the self-discharge test method of the reference has been improved and used to evaluate the anti-self-discharge behavior of Li-S batteries, providing a more reasonable and precise test method of anti-self-discharge behavior. The results of this work show that the polymer materials with lithium sulfonic groups in the coating layer of separator can facilitate the transporting of Li+ and decrease the migration of



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lithium polysulides through the separator. This study introduces a simple, low cost and effective strategy to modify separator of Li-S batteries, which can suppress the shuttle effect of polysulfides and then enhance the batteries’ performance.

Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem. XXXX Figure S1-S14 and Table S1-S3

Acknowledgements This research was supported by the NSFC (U1301244, U1601211, 51573215, and 21506260), Guangdong Province Sci & Tech Bureau Key Strategic Project (No. 2016B010114004),

NSF

of

Guangdong

Province

(2016A030313354,

2014A030313159), the Special Project on the Integration of Industry, Education and

Research of Guangdong Province (2015B09090100, 2014B090904064), Guangzhou Scientific and Technological Planning Project (2014J4500002，201607010042, and 2017), the Fundamental Research Funds for the Central Universities (171gjc37).

References (1) Manthiram, A.; Fu, Y.; Chung, S. H.; Zu, C.; Su, Y. S. Rechargeable lithium-sulfur batteries. Chem. Rev. 2014, 114, 11751-11787. (2) Urbonaite, S.; Poux, T.; Novák, P. Progress Towards Commercially Viable Li-S Battery Cells. Adv. Eng. Mater. 2015, 5, 1500118-1500137. (3) Long, L.; Wang, S.; Xiao, M.; Meng, Y. Polymer electrolytes for lithium polymer batteries. J. Mater. Chem. A 2016, 4, 10038-10069. (4) Seh, Z. W.; Sun, Y.; Zhang, Q.; Cui, Y. Designing high-energy lithium-sulfur batteries. Chem. Soc. Rev. 2016, 45, 5605-5634.


Page 27 of 33 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


(5) Qu, C.; Chen, Y.; Yang, X.; Zhang, H.; Li, X.; Zhang, H. LiNO3 -free electrolyte for Li-S battery: A solvent of choice with low K sp of polysulfide and low dendrite of lithium. Nano Energy 2017, 39, 262-272. (6) Pang, Q.; Liang, X.; Kwok, C. Y.; Nazar, L. F. Advances in lithium-sulfur batteries based on multifunctional cathodes and electrolytes. Nat. Energy 2016, 1, 16132-16142. (7) Yan, B.; Li, X.; Bai, Z.; Song, X.; Xiong, D.; Zhao, M.; Li, D.; Lu, S. A review of atomic layer deposition providing high performance lithium sulfur batteries. J. Power Sources 2017, 338, 34-48. (8) Jiang, Y.; Chen, F.; Gao, Y.; Wang, Y.; Wang, S.; Gao, Q.; Jiao, Z.; Zhao, B.; Chen, Z. Inhibiting the shuttle effect of Li-S battery with a graphene oxide coating separator: Performance improvement and mechanism study. J. Power Sources 2017, 342, 929-938. (9) Li, Y.; Wang, L.; Gao, B.; Li, X.; Cai, Q.; Li, Q.; Peng, X.; Huo, K.; Chu, P. K. Hierarchical Porous Carbon Materials Derived from Self-Template Bamboo Leaves for Lithium-Sulfur Batteries. Electrochim. Acta 2017, 229, 352-360. (10) Jana, A.; Ely, D. R.; García, R. E. Dendrite-separator interactions in lithium-based batteries. ACS Appl. Mater. Inter. 2015, 275, 912-921. (11) Xie, K.; Yuan, K.; Zhang, K.; Shen, C.; Lv, W.; Liu, X.; Wang, J. G.; Wei, B. Dual Functionalities of Carbon Nanotube Films for Dendrite-Free and High Energy-High Power Lithium-Sulfur Batteries. ACS Appl. Mater. Inter. 2017, 9, 4605-4613. (12) Deng, N.; Kang, W.; Liu, Y.; Ju, J.; Wu, D.; Li, L.; Hassan, B. S.; Cheng, B. A review on separators for lithiumsulfur battery: Progress and prospects. J. Power Sources 2016, 331, 132-155. (13) Cheng, X.-B.; Huang, J.-Q.; Peng, H.-J.; Nie, J.-Q.; Liu, X.-Y.; Zhang, Q.; Wei, F. Polysulfide shuttle control: Towards a lithium-sulfur battery with superior capacity performance up to 1000 cycles by matching the sulfur/electrolyte loading. J. Power Sources 2014, 253, 263-268.



(14) Yim, T.; Han, S. H.; Park, N. H.; Park, M.-S.; Lee, J. H.; Shin, J.; Choi, J. W.; Jung, Y.; Jo, Y. N.; Yu, J.-S.; Kim, K. J. Effective Polysulfide Rejection by Dipole-Aligned BaTiO3 Coated Separator in Lithium-Sulfur Batteries. Adv. Funct. Mater. 2016, 26, 7817-7823. (15) Oschmann, B.; Park, J.; Kim, C.; Char, K.; Sung, Y.-E.; Zentel, R. Copolymerization of Polythiophene and Sulfur To Improve the Electrochemical Performance in Lithium-Sulfur Batteries. Chem. Mater. 2015, 27, 7011-7017. (16) Fang, R.; Zhao, S.; Hou, P.; Cheng, M.; Wang, S.; Cheng, H. M.; Liu, C.; Li, F. 3D Interconnected Electrode Materials with Ultrahigh Areal Sulfur Loading for Li-S Batteries. Adv. Mater. 2016, 28, 3374-3382. (17) Al Salem, H.; Babu, G.; Rao, C. V.; Arava, L. M. Electrocatalytic Polysulfide Traps for Controlling Redox Shuttle Process of Li-S Batteries. J. Am. Chem. Soc. 2015, 137, 11542-11545. (18) Wang, L.; Zhao, Y.; Thomas, M. L.; Dutta, A.; Byon, H. R. Sulfur-Based Catholyte Solution with a Glass-Ceramic Membrane for Li-S Batteries. ChemElectroChem 2016, 3, 152-157. (19) Wang, H.; Zhang, W.; Liu, H.; Guo, Z. A Strategy for Configuration of an Integrated Flexible Sulfur Cathode for High-Performance Lithium-Sulfur Batteries. Angew. Chem. Int. Ed. 2016, 55, 3992-3996. (20) Fang, R.; Zhao, S.; Pei, S.; Cheng, Y.; Hou, P.; Liu, M.; Cheng, H.-M.; Liu, C.; Li, F. An integrated electrode/separator with nitrogen and nickel functionalized carbon hybrids for advanced lithium/polysulfide batteries. Carbon 2016, 109, 719-726. (21) Xiang, Y.; Li, J.; Lei, J.; Liu, D.; Xie, Z.; Qu, D.; Li, K.; Deng, T.; Tang, H. Advanced Separators for Lithium-Ion and Lithium-Sulfur Batteries: A Review of Recent Progress. ChemSusChem 2016, 9, 3023-3039. (22) Bai, S.; Liu, X.; Zhu, K.; Wu, S.; Zhou, H. Metal-organic framework-based separator for lithium–sulfur batteries. Nat. Energy 2016, 1, 16094-16099. (23) Zhuang, T. Z.; Huang, J. Q.; Peng, H. J.; He, L. Y.; Cheng, X. B.; Chen, C. M.; Zhang, Q. Rational Integration of Polypropylene/Graphene Oxide/Nafion as Ternary-Layered


Page 28 of 33

Page 29 of 33 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


Separator to Retard the Shuttle of Polysulfides for Lithium-Sulfur Batteries. Small 2016, 12, 381-389. (24) Zhu, J.; Yanilmaz, M.; Fu, K.; Chen, C.; Lu, Y.; Ge, Y.; Kim, D.; Zhang, X. Understanding glass fiber membrane used as a novel separator for lithium-sulfur batteries. J. Membrane Sci.2016, 504, 89-96. (25) Ji, X.; Lee, K. T.; Nazar, L. F. A highly ordered nanostructured carbon-sulphur cathode for lithium-sulphur batteries. Nat. Mater. 2009, 8, 500-506. (26) Vizintin, A.; Lozinšek, M.; Chellappan, R. K.; Foix, D.; Krajnc, A.; Mali, G.; Drazic, G.; Genorio, B.; Dedryvère, R.; Dominko, R. Fluorinated Reduced Graphene Oxide as an Interlayer in Li–S Batteries. Chem. Mater. 2015, 27, 7070-7081. (27) Chen, G.; Song, X.; Wang, S.; Wang, Y.; Gao, T.; Ding, L.-X.; Wang, H. A multifunctional separator modified with cobalt and nitrogen co-doped porous carbon nanofibers for Li–S batteries. J. Membrane Sci. 2018, 548, 247-253. (28) Balach, J.; Jaumann, T.; Klose, M.; Oswald, S.; Eckert, J.; Giebeler, L. Functional Mesoporous Carbon-Coated Separator for Long-Life, High-Energy Lithium-Sulfur Batteries. Adv. Funct. Mater. 2015, 25, 5285-5291. (29) Kim, H. M.; Hwang, J. Y.; Manthiram, A.; Sun, Y. K. High-Performance Lithium-Sulfur Batteries with a Self-Assembled Multiwall Carbon Nanotube Interlayer and a Robust Electrode-Electrolyte Interface. ACS Appl. Mater. Inter. 2016, 8, 983-987. (30) Chung, S. H.; Han, P.; Manthiram, A. A Polysulfide-Trapping Interface for Electrochemically Stable Sulfur Cathode Development. ACS Appl. Mater. Inter. 2016, 8, 4709-4717. (31) Hao, Z.; Yuan, L.; Li, Z.; Liu, J.; Xiang, J.; Wu, C.; Zeng, R.; Huang, Y. High performance lithium-sulfur batteries with a facile and effective dual functional separator. Electrochim. Acta 2016, 200, 197-203. (32) Kim, M. S.; Ma, L.; Choudhury, S.; Moganty, S. S.; Wei, S.; Archer, L. A. Fabricating multifunctional nanoparticle membranes by a fast layer-by-layer Langmuir-Blodgett process: application in lithium–sulfur batteries. J. Mater. Chem. A 2016, 4, 14709-14719.



(33) Luo, L.; Chung, S.-H.; Manthiram, A. A trifunctional multi-walled carbon nanotubes/polyethylene glycol (MWCNT/PEG)-coated separator through a layer-by-layer coating strategy for high-energy Li-S batteries. J. Mater. Chem. A 2016, 4, 16805-16811. (34) Zhang, Z.; Lai, Y.; Zhang, Z.; Zhang, K.; Li, J. Al2O3-coated porous separator for enhanced electrochemical performance of lithium sulfur batteries. Electrochim. Acta 2014, 129, 55-61. (35) Dong, K.; Wang, S.; Zhang, H.; Wu, J. Preparation and electrochemical performance of sulfur-alumina cathode material for lithium-sulfur batteries. Mater. Res. Bull. 2013, 48, 2079-2083. (36) Zhu, J.; Yildirim, E.; Aly, K.; Shen, J.; Chen, C.; Lu, Y.; Jiang, M.; Kim, D.; Tonelli, A. E.; Pasquinelli, M. A.; Bradford, P. D.; Zhang, X. Hierarchical multi-component nanofiber separators for lithium polysulfide capture in lithium-sulfur batteries: an experimental and molecular modeling study. J. Mater. Chem. A 2016, 4, 13572-13581. (37) Song, J.; Su, D.; Xie, X.; Guo, X.; Bao, W.; Shao, G.; Wang, G. Immobilizing Polysulfides with MXene-Functionalized Separators for Stable Lithium-Sulfur Batteries. ACS Appl. Mater. Inter. 2016, 8, 29427-29433. (38) Ma, L.; Nath, P.; Tu, Z.; Tikekar, M.; Archer, L. A. Highly Conductive, Sulfonated, UV-Cross-Linked Separators for Li–S Batteries. Chem. Mater. 2016, 28, 5147-5154. (39) Xie, C. Electrostatic Shield Effect: An Effective Way to Modify Celgard Membrane Separator Used in Lithium-sulfur Battery. Int. J. Electrochem. Sci. 2017, 6751-6762. (40) Yu, X.; Joseph, J.; Manthiram, A. Suppression of the polysulfide-shuttle behavior in Li-S batteries through the development of a facile functional group on the polypropylene separator. Mater. Horiz. 2016, 3, 314-319. (41) Abbas, S. A.; Ibrahem, M. A.; Hu, L.-H.; Lin, C.-N.; Fang, J.; Boopathi, K. M.; Wang, P.-C.; Li, L.-J.; Chu, C.-W. Bifunctional separator as a polysulfide mediator for highly stable Li–S batteries. J. Mater. Chem. A 2016, 4, 9661-9669.


Page 30 of 33

Page 31 of 33 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


(42) Conder, J.; Forner-Cuenca, A.; Gubler, E. M.; Gubler, L.; Novak, P.; Trabesinger, S. Performance-Enhancing Asymmetric Separator for Lithium-Sulfur Batteries. ACS Appl. Mater. Inter. 2016, 8, 18822-18831. (43) Ju, Y.-W.; Jung, H.-R.; Lee, W.-J. Electrochemical characteristics of poly(3-methyl thiophene)/sulfonated-SEBS composite electrode for polymer battery. Synth. Met. 2007, 157, 823-826. (44) Hart, C. J.; Cuisinier, M.; Liang, X.; Kundu, D.; Garsuch, A.; Nazar, L. F. Rational design of sulphur host materials for Li-S batteries: correlating lithium polysulphide adsorptivity and self-discharge capacity loss. Chem. Commun. 2015, 51, 2308-2311. (45) Chen, X. C.; Kortright, J. B.; Balsara, N. P. Water Uptake and Proton Conductivity in Porous Block Copolymer Electrolyte Membranes. Macromolecules 2015, 48, 5648-5655. (46)

Ganguly,

A.;

Bhowmick,

A.

K.

Sulfonated

Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties. Nanoscale Res. Lett. 2008, 3, 36-44. (47) Weiss, R.; Sen, A.; Willis, C.; Pottick, L. Block copolymer ionomers: 1. Synthesis and physical properties of sulphonated poly (styrene-ethylene/butylene-styrene). Polymer 1991, 32, 1867-1874. (48) Jin, J.; Lin, C.; Zhang, W.; Wang, L.; Wang, Z. G.; Zhao, W.; Duan, W.; Zhao, Z. G.; Liu, B. Few-layered Ti3C2 nanosheet/glass fiber composite separator as lithium polysulphide reservoir for high-performance lithium-sulfur battery. J. Mater. Chem. A 2016, 4, 5993-5998. (49) Chen, X. C.; Wong, D. T.; Yakovlev, S.; Beers, K. M.; Downing, K. H.; Balsara, N. P. Effect of morphology of nanoscale hydrated channels on proton conductivity in block copolymer electrolyte membranes. Nano lett. 2014, 14, 4058-4064. (50) Mistri, E. A.; Mohanty, A. K.; Banerjee, S.; Komber, H.; Voit, B., Naphthalene dianhydride

based

semifluorinated

sulfonated

copoly(ether

imide)s:

Synthesis,

characterization and proton exchange properties. J. Membrane Sci. 2013, 441, 168-177. (51) Chhabra, P.; Choudhary, V., Synthesis and characterization of sulfonated naphthalenic polyimides

based

on

4,4’-diaminodiphenylether-2,2’-disulfonic


acid

and


bis[4-(4-aminophenoxy)phenylhexafluoropropane] for fuel cell applications. Eur. Polym. J. 2009, 45, 1467-1475. (52) Peng, H. J.; Wang, D. W.; Huang, J. Q.; Cheng, X. B.; Yuan, Z.; Wei, F.; Zhang, Q. Janus Separator of Polypropylene-Supported Cellular Graphene Framework for Sulfur Cathodes with High Utilization in Lithium-Sulfur Batteries. Adv. Sci. 2016, 3, 1500268-1500278. (53) Kim, P. J. H.; Seo, J.; Fu, K.; Choi, J.; Liu, Z.; Kwon, J.; Hu, L.; Paik, U. Synergistic protective effect of a BN-carbon separator for highly stable lithium sulfur batteries. NPG Asia Mater. 2017, 9, e375. (54) Lee, D. K.; Ahn, C. W.; Jeon, H.-J. Web-structured graphitic carbon fiber felt as an interlayer for rechargeable lithium-sulfur batteries with highly improved cycling performance. J. Power Sources 2017, 360, 559-568. (55) Liu, M.; Li, Q.; Qin, X.; Liang, G.; Han, W.; Zhou, D.; He, Y. B.; Li, B.; Kang, F., Suppressing Self-Discharge and Shuttle Effect of Lithium-Sulfur Batteries with V2O5-Decorated Carbon Nanofiber Interlayer. Small 2017, 13, 1602539-1602545. (56) Hendrickson, K. E.; Ma, L.; Cohn, G.; Lu, Y.; Archer, L. A., Model Membrane-Free Li-S Batteries for Enhanced Performance and Cycle Life. Adv. Sci. 2015, 2, 1500068. (57) Liu, F.; Xiao, Q.; Wu, H. B.; Sun, F.; Liu, X.; Li, F.; Le, Z.; Shen, L.; Wang, G.; Cai, M.; Lu, Y. Regenerative Polysulfide-Scavenging Layers Enabling Lithium-Sulfur Batteries with High Energy Density and Prolonged Cycling Life. ACS Nano 2017, 11,2697-2705. (58) Lu, Y.; Gu, S.; Guo, J.; Rui, K.; Chen, C.; Zhang, S.; Jin, J.; Yang, J.; Wen, Z. Sulfonic Groups Originated Dual-Functional Interlayer for High Performance Lithium-Sulfur Battery. ACS Appl. Mater. Inter. 2017, 9, 14878-14888. (59) Wang, Q.; Wen, Z.; Yang, J.; Jin, J.; Huang, X.; Wu, X.; Han, J. Electronic and ionic co-conductive coating on the separator towards high-performance lithium-sulfur batteries. J. Power Sources 2016, 306, 347-353. (60) Zhang, S. Improved Cyclability of Liquid Electrolyte Lithium/Sulfur Batteries by Optimizing Electrolyte/Sulfur Ratio. Energies 2012, 5, 5190-5197.


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Abstract Graphic


A Functional Separator Coated with Sulfonated ... - ACS Publications

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