MoS2-Coated N-doped Mesoporous Carbon Spherical Composite

Subscriber access provided by University of Sunderland

Article

MoS2-Coated N-doped Mesoporous Carbon Spherical Composite Cathode and CNTs/Chitosan Modified Separator for Advanced Lithium Sulfur Batteries Shouxin Jiang, Manfang Chen, Xianyou Wang, Zhenyu Wu, Peng Zeng, Cheng Huang, and Ying Wang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b04157 • Publication Date (Web): 19 Oct 2018 Downloaded from http://pubs.acs.org on October 23, 2018

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 41 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 Sustainable Chemistry & Engineering

MoS2-Coated N-doped Mesoporous Carbon Spherical Composite Cathode and CNTs/Chitosan Modified Separator for Advanced Lithium Sulfur Batteries Shouxin Jianga, Manfang Chena, Xianyou Wanga*, Zhenyu Wua, Peng Zenga, Cheng Huanga, Ying Wangb (a: National Base for International Science & Technology Cooperation, National Local Joint Engineering Laboratory for Key Materials of New Energy Storage Battery, Hunan Province Key Laboratory of Electrochemical Energy Storage & Conversion, School of Chemistry, Xiangtan University, Hunan 411105, China b: Department of Chemistry, University of North Carolina at Chapel Hill, North Carolina, 27514, USA)

Abstract The polysulfide shuttle effect is one of the most important problems hindering the commercial application of lithium-sulfur batteries (LSBs). In order to solve above problem and promote the LSBs commercialization, herein a holistic design strategy on the molybdenum disulfide-coated nitrogen-doped mesoporous carbon sphere/sulfur (NMCS@MoS2/S) composite cathode and carbon nanotube/chitosan modified separator (CNTs/CH) is proposed. In the holistic design, the NMCS@MoS2 plays a role in the host of sulfur and the lithium polysulfides (LiPSs) adsorbent, the CNTs/CH modified separator also has an inestimable role in promoting lithium ion transport and chemical adsorption of LiPSs. The results show that the LSBs with the NMCS@MoS2/S-CNTs/CH release a high reversible capacity of 827 mAh g-1 with

*



Corresponding author: Tel: +86 731 58293377; E-mail address: [email protected] (X. Wang) Corresponding author: Tel: +1 984-234-8489; E-mail address: [email protected] (Y. Wang) 1

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

high capacity retention of 92.4 % at 0.5 C after 200 cycles. The delicate design exhibits apparently excellent electrochemical performance and provides an exciting strategy for solving the shuttle effect of LiPSs and boosting industrialization of LSBs.

Keywords: Lithium sulfur batteries; Polysulfides; Holistic design; Molybdenum disulfide; Chitosan

Introduction With the rapid development of portable electronic devices and electric vehicles, the requirement of advanced energy storage systems with low cost and high energy density has significantly increased.1-4 However, due to the low energy density of traditional lithium-ion batteries, the current technology of lithium ion battery can not meet the requirements of the development of the times. LSBs are considered as a promising candidate for the next-generation energy storage equipment, on account of its high theoretical specific capacity (1675 mAh g-1) and energy density (2600 Wh kg-1).5-7 Simultaneously, elemental sulfur is low-price, environmental-friendly and abundant in nature.8 Nevertheless, the applications of LSBs are limited by the three main issues: (1) poor conductivity of the elemental sulfur and the discharge products (Li2S and Li2S2); (2) large volumetric expansion (80 %) from sulfur to Li2S; (3) the "shuttle effect" produced by the soluble LiPSs (Li2Sn, 4 ≤ n ≤ 8), which lead to the loss of the sulfur, poor cycle stability of the LSBs and serious security problems.9-11 For solving the mentioned-above problems, the combination of sulfur and carbonaceous materials has been regarded as a common way because of the good 2


Page 2 of 41

Page 3 of 41 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


conductivity of carbon materials. Nazar and her co-workers first proposed the highly ordered mesoporous carbon (CMK-3) as the host materials of sulfur, and the resultant LSBs showed good electrochemistry performances.12 Enlightened by this work, carbon materials as the host materials of sulfur have arisen one after another, such as biomaterial carbon,13-15 hollow carbon spheres,16,

17

carbon nanotubes18-20 and

graphene.21, 22 Although these researches have achieved some good progress, there is not strong binding ability between the non-polar carbon materials and the polar LiPSs by physical adsorption. The carbon/sulfur composite cathode still suffered from poor cycle stability over long cycles.23 Lately, the polar materials are widely concerned because of their strong chemical interaction with LiPSs. For instance, nitrogen-sulfur co-doped carbon materials lead to a significant increase in the chemical adsorption capacity of LiPSs.24-26 Metal oxides,27, 28 metal sulfides,29-31 metal nitrides,32-34 and metal carbides

35, 36

are also used as the host of sulfur, because their adsorption

capacity for LiPSs is stronger than carbon materials. To raise the performance of LSBs to a new height, various interlayer and modified separator are introduced into the LSBs.37-42 Although the technology of LSBs has made great progress, so far, researchers have not proposed effective methods to provide high specific capacity and good stability capacity with high sulfur loading. At present, almost all of the works only focus on heightening the loading of sulfur without regard to the holistic design of the LSBs with the design of cathode and modified separator. Herein, we propose a holistic design of the high-performance LSBs, including a high-polarity molybdenum 3



disulfide-coated nitrogen-doped mesoporous carbon sphere (NMCS@MoS2) as a host material of sulfur and a carbon nanotube/chitosan-modified separator as a separator. In this holistic design, the high polarity MoS2 ameliorates the electrochemical reaction kinetics and promotes the adsorption ability for LiPSs. In addition, the CNTs/CH heightens cycle stability and rate performance by the improvement of the Li+ ion transfer and adsorption capacity for LiPSs. Therefore, the proposed LSBs with NMCS@MoS2/S-CNTs/CH deliver a high initial specific capacity of 847 mAh g-1 with a slight capacity attenuation of 0.08 % per cycle after 500 cycles, showing excellent long-term cycle stability at 1 C.

Experimental section Composite synthesis Synthesis of CNTs/CH, CNTs and CH Modified Separators. Chitosan (1g) was distributed in a 2 wt% acetic acid solution under stirring vigorously for 24 h. Mixed up the prepared chitosan dispersion with CNTs in a ratio of 5:95 wt % in a diluent of 1:1 (V/V) of isopropanol to deionized water. Then, transferred the mixture to the agate ball mill and ball mill for 10 h under 400 rpm using agate beads. The separator was coated with the slurry and dried at 40 °C overnight in vacuum. To obtain the CNTs/CH modified separator, the coated separator was cut into a small circle with a diameter of 19 mm. The CNTs and CH modified separator was prepared by the same method. Synthesis of Walnut-like Mesoporous Silica Nanosphere (WMSNs). 4


Page 4 of 41

Page 5 of 41 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


Triethylamine (TEA, 0.41 g) was scattered in deionized water (150 ml) with stirring magnetically at 70 °C for 1 h. Hexadecyl trimethyl ammonium bromide (CTAB, 2.28 g) and NaSal (1.512g) were added into the above solution with further stirred for 1 h. Then, tetraethoxysilane (TEOS, 24 mL) was added drop by drop under stirring magnetically for 12h. The solution was washed in deionized water to remove the impurity. To obtain the WMSNs, the material was dried in oven at 60 °C for 12 h. Synthesis of NMCS The prepared WMSNs (120 mg) was scattered in buffer solution (90 mL, pH = 8.5) under ultrasonic for 1 h. Then, dopamine (180 mg) was scattered in the above solution and kept stirring for one day at room temperature. The product was obtained by filtration and washed several times with ethanol and deionized water. After being dried at 50 °C for 12 h, the product was transferred to corundum crucible and annealed in a tube furnace at 800 °C for 3 h under argon atmosphere with a heating rate of 3 °C min-1. Subsequently, the products after carbonization were transferred to a Teflon beaker, and using hydrofluoric acid (HF, 5 wt %) to remove WMSNs by stirring vigorously in the fume hood for 12 h. In order to remove the redundant HF, the products were washed by deionized water. The NMCS was gained after being dried at 60 °C in vacuum for 12 h. Synthesis of NMCS@MoS2 Firstly, NMCS (50 mg) was distributed in deionized water (50 mL) under ultrasonic for 30 minutes to obtain a uniform black solution, and then sodium molybdate dihydrate (400 mg) and thiourea (400 mg) were ultrasonically dispersed in 5



the above solution for 30 minutes and transferred to 100 mL Teflon lined stainless steel autoclave with reacted at 200 °C for 24 h in high temperature blast oven. The products were washed with deionized water and ethanol and then dried under vacuum at 80 °C for 12 h. Finally, to obtain NMCS@MoS2, the product was heated at 800 °C for 6 hours to improve the crystallinity in a tube furnace under an argon atmosphere to obtain NMCS@MoS2. Synthesis of NMCS@MoS2/S and NMCS/S Mixing NMCS@MoS2 and sulfur in a mass ratio of 1:3, then add to the mixed solution of CS2 and alcohol with vigorously stirring. It was placed overnight in a fume hood for evaporation of CS2 and alcohol. Transfered the material to a sealed vial and holded at 160 °C for 12 hours under an argon atmosphere, followed by a treatment at 250 °C for 90 minutes to remove excess sulfur from the surface of the material. This gave the NMCS@MoS2/S composite, and the NMCS/S composite was prepared in the same manner. Synthesis of Li2S6 solution Mixing lithium sulfide (Li2S) and element sulfur in a molar ratio of 1:5 are added to suitable THF solution with vigorously stirring at 25 °C in an argon glove box. Materials characterization The structure, morphology, composition information and optical properties of these materials were probed by scanning electron microscopy (SEM, TM4000, Japan) transmission electron microscope (TEM, JEOL, JEM-2100F), Raman spectroscopy (LabRAM HR800, 532 nm excitation), X-ray diffraction (XRD, Model D8-Advance, 6


Page 6 of 41

Page 7 of 41 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


Germany) and X-ray photoelectron spectroscopy (XPS, K-Alpha+, America). The sulfur and MoS2 content of the samples were researched on Series Q500 instrument (TGA Instruments, USA). Brunauer-Emmett-Teller (BET) was mined to analyze the specific surface area and the holey structure.

Electrochemical measurements The cathode electrodes for the LSBs were made by modulating the slurry of 70 wt% active materials (NMCS@MoS2/S or NMC/S), 20 wt% Super P and 10 wt% PVDF in NMP on the current collector and dried 60 °C for 12 h before using. The active material mass loading about 1.2 mg cm-2. The anode was lithium wafer. CNTs/CH, CNTs or CH modified separator were employed as separator. The 1 mol L-1 LiTFSI and 0.1 LiNO3 were dissolved in a mixture of 1,3-dioxolane (DOL) / 1,2-dimethoxyethane (DME) (1/1, v/v) as ele ctrolyte. LSBs were characterized at different constant current rates between 1.8 V and 2.8 V on Neware tester (BTS-XWJ-6.44S-00052 Neware, Shenzhen, China) in a petty voltage window of 1.8-2.8V. Cyclic voltammetry (CV) and EIS measurements were tested by an electrochemical workstation (CHI660e, Chenhua, China). The CV examinations were examined between 1.8 and 2.8V at a scan rate of 0.2 mV S-1 .The frequency range of EIS was from 10-2 to 105 Hz with amplitude of 5 mV. All the tests were conducted at 25 °C.

7



Results and discussions The schematic diagram of the synthesis process of NMCS@MoS2/S sample is shown in Fig. 1a. First, the WMSNs is prepared by the reported method.43 After coating with polydopamine, the composite is heated on 800 °C for 3 h and processed by the 5 % HF solution to remove the WMSNs. The NMCS owning a uniform diameter of about 250 nm is produced. Subsequently, NMCS@MoS2 is made through a simple solvothermal method and heated at 800 °C for 6 h in argon atmosphere to improve the crystallinity. Finally, sulfur is infiltrated into NMCS@MoS2 host. The schematic diagram of the adsorbed polysulfide by chitosan is shown in Fig. 1b. The chitosan uniformly covers the surface of the carbon nanotubes after ball milling. The polar functional groups of hydroxyl and amino on the surface of the chitosan can tightly adsorb the LiPSs dissolved in the electrolyte.

8


Page 8 of 41

Page 9 of 41 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 1. (a) Schematic diagram of the synthesis step of NMCS@MoS2/S sample (b) Schematic diagram adsorption of polysulfide by chitosan. In order to study the morphology and nanostructure of as-prepared composites, the representative SEM and TEM images are illustrated in Fig. 2. As demonstrated in Fig. 2a and b, it can clearly draw such a conclusion that the prepared DMCSs reflect a unique dendritic structure and uniform particle size of around 300 nm. The NMCS show small particle size of about 250 nm in Fig. 2c and d. At the same time, from the TEM images of Fig. 2g, the NMCS own abundant pore structures, which will help to increase sulfur loading. In addition, there is a distinct graphitization layer at the edge of NMCS. As shown in Fig. 2e, f, I and k, the MoS2 nanosheets are evenly coated on 9



the NMCS. The HRTEM images of NMCS@MoS2 is shown in Fig. 2i, the layer spacing is approximately 0.65 nm, which corresponds to the (002) lattice plane of MoS2. As shown in Fig. 2l-o, elemental mapping images demonstrate the uniform distribution of Mo, S, C and N in NMCS@MoS2.

Figure 2. SEM images of (a, b) DMCSs, (c, d) NMCS, (e, f) NMCS@MoS2, (g) TEM images of NMCS, (h) HRTEM images of NMCS, (i, k) TEM images of NMCS@MoS2, (j) HRTEM images of NMCS@MoS2, elemental mapping

images of (l) carbon, (m) nitrogen (n) molybdenum (o) sulfur. The digital photo of the prepared CNTs/CH modified separator is shown in 10


Page 10 of 41

Page 11 of 41 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


Fig.3a, the surface of the CNTs/CH modified separator is smooth. After several times of bending as shown in the illustration of Fig.3b, the material is attached firmly to the diaphragm without any shedding or peeling, which shows good mechanical stability. From the SEM image of Fig. 3c, the surface of the CNTs/CH modified separator is smooth and compact. The cross-section SEM image of the CNTs/CH is shown in Fig. 3d, it can be clearly seen that the coated layer of CNTs/CH modified separator owns uniform thickness of 5 μm. In addition, the areal mass of CNTs/CH modified separator is lightweight (0.35 mg cm-2).

11



Page 12 of 41

Figure 3. Digital photos of (a) CNTs/CH modified separator, (b) CNTs/CH modified separator after be folded several times, (c) SEM images of surface of CNTs/CH modified separator, (d) cross section of CNTs/CH modified separator. N2 adsorption/desorption isotherms of the NMCS, NMCS@MoS2 and NMCS@MoS2/S samples are confirmed and displayed in Fig. 4a, b and c, where typical type-IV isotherms could be observed for all three samples, indicating a large number

of

mesoporous

in

the

composites.

The

corresponding

Brunauer–Emmett–Teller (BET) specific surface areas of the NMCS, NMCS@MoS2 12


Page 13 of 41 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


and NMCS@MoS2/S are 1198.1, 323.5 and 136.1 m2 g-1, respectively. MoS2 coating on NMCS results in a smaller specific surface area. The smaller one of the NMCS@MoS2/S is owed to the infiltration of sulfur to the NMCS@MoS2. As shown in Fig.4d, e, f and based on the BJH calculation, the pore size of NMCS, NMCS@MoS2 and NMCS@MoS2/S samples are 7.53, 13.02 and 8.97 nm, respectively. NMCS@MoS2 shows a large specific surface area and rich pore structure, which is beneficial to the infiltration of elemental sulfur, lithium ion transport, electrolyte infiltration and physical confinement of LiPSs. The increase of the pore size for NMCS@MoS2 is due to the sheet-structured MoS2 coated on the surface of NMCS, while the decrease of the pore size for NMCS@MoS2/S is attributed to infiltration of sulfur. The pore volumes of the NMCS and NMCS@MoS2 and NMCS@MoS2/S are 2.52, 1.14 and 0.32 cm3 g-1, respectively. Obviously, the specific surface area and pore volume in the NMCS@MoS2/S material were significantly decreased, indicating that sulfur penetrated into the pore structure of the material.

13



Figure 4. N2 adsorption/desorption isotherms and pore size distributions of NMCS (a, d), NMCS@MoS2 (b, e) and NMCS@MoS2/S (c, f). The crystal structures and phase information of NMCS, NMCS@MoS2, NMCS@S and NMCS@MoS2/S are investigated using X-ray diffraction (XRD, XPS and Raman spectrum. Fig. 5a demonstrates the XRD pattern of the NMCS@MoS2, the peaks can correspond to the 2H-MoS2 phase (JCPDS no. 37-1492). The diffraction peaks positions of NMCS/S and NMCS@MoS2/S are in full accord with standard card (JCPSD no. 08-0247) as shown in Fig. 5b. TGA method is used to measure the sulfur content of the NMCS/S and NMCS@MoS2/S composite in N2 flow under a heating rate of 10 °C min-1. As shown in Fig. 5c, sulfur contents of NMCS/S and 14


Page 14 of 41

Page 15 of 41 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


NMCS@MoS2/S composites are about 76 and 78 wt %, respectively. At the same time, in order to confirm the carbon content in the NMCS@MoS2, the NMCS@MoS2 composite is tested by TGA method in airflow under a heating rate of 10 °C min-1. The weight loss of 38 wt% of the NMCS@MoS2 is corresponds to the conversion of MoS2 to MoO3 and the combustion of NMCS. The MoS2 content of the NMCS@MoS2 is calculated about 69 wt%.44 Raman spectra of the NMCS@MoS2 in Fig. 5d exhibits two distinct peaks at around 80.8 and 407.8 cm-1 are described as E12g and A1g, which are the vibration modes of MoS2. Simultaneously, the characteristic bands D band (1352 cm-1) and G band (1583 cm-1) are observed in NMCS and NMCS@MoS2. The ID/IG ratios of NMCS and NMCS@ MoS2 are 0.86 and 1.01, respectively. Compared with NMCS, the ID/IG ratio of NMCS@MoS2 material increases, indicating that the reduction process of MoS2 changes the structure of NMCS and contains more structural defects,45 which is consistent with XRD results. In the XPS spectrum of NMCS of Fig. 5e, it can be clearly seen that only three peaks at 284.1, 401.1 and 533.1 eV are revealed, corresponding to C 1s, N 1s and O 1s, respectively. Differently, seven peaks can be clearly seen at 532.1, 413.0, 401.1, 281.1, 229.1, 162.1 and 37.1 eV in the XPS spectrum of NMCS@MoS2, which corresponds to O 1s, Mo 3p, N 1s, C 1s, Mo 3d, S 2p and Mo 4p, respectively. Meanwhile, the atomic ratio of S to Mo is about 0.5, which is consistent with the stoichiometric ratio of MoS2. As shown in Fig. 5f, the three C 1s peaks at 284.8, 286.1, and 289.4 eV are ascribed to C−C/C=C, C−O/C−N and C=O/O−C=O, respectively. Three obvious peaks of N 1s at 398.3, 400.9 and 403.5 eV are attributed to the pyridinic, pyrrolic and 15



graphitic N in Fig. 5g. The Mo 3d spectra in Fig 5h displays two peaks at 229.7 and 232.9 eV, corresponding to Mo 3d5/2 and Mo 3d3/2, respectively, owing to the Mo4+ of MoS2. The peak located at 227.1 eV is corresponding to S 2s of S2-. As shown in Fig. 5i, two apparent peaks at 162.5 and 163.7 eV in the S 2p spectrum are described as S 2p3/2 and S 2p1/2, respectively. All of these chemical compositions and valence states will help to improve the electrochemical performance of LSBs.

Figure 5. (a) XRD pattern of NMCS and NMCS@MoS2, (b) XRD pattern of NMCS/S and NMCS@MoS2/S, (c) TGA traces, sulfur contents of NMCS/S and NMCS@MoS2 in N2, carbon contents of NMCS@MoS2 in air, (d) Raman spectra of NMCS and NMCS@MoS2, (e) XPS measure spectrum of NMCS and NMCS@MoS2, (f) C 1s, (g) N 1s, (h) Mo 3d, (i) S 2p, A more intuitive method to detect the interaction of NMCS, NMCS@MoS2 and 16


Page 16 of 41

Page 17 of 41 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


CNTs/CH to Li2S6 is shown in Fig. 6h. 10 mg of the NMCS, NMCS@MoS2 and CNTs/CH samples are separately added to the prepared Li2S6 solution. Unsurprisingly, when NMCS is added to Li2S6 solution, the color becomes slightly lighter, indicating weak binding ability to LiPSs. Conversely, when NMCS@MoS2 and CNTs/CH are added to the prepared Li2S6 solution, respectively. The yellow-colored Li2S6 solution rapidly becomes nearly colorless, indicating strong binding ability of NMCS@MoS2 and CNTs/CH to LiPSs. Meanwhile, in order to further analyze the Li2S6 concentration in the solution, UV adsorption spectroscopy is used. Compared with the Li2S6 solution, the NMCS is added to the Li2S6 solution, and the S62- characteristic peaks decreased slightly. Conversely, with the addition of NMCS@MoS2 and CNTs/CH, the characteristic peaks of S62- are drastically reduced, indicating that most of the Li2S6 in the solution is absorbed by NMCS@MoS2 and CNTs/CH, which proves strong adsorption capacity of NMCS@MoS2 and CNTs/CH to LiPSs.

17



Figure 6. UV/Vis adsorption spectra and adsorption ability tests of NMCS, NMCS@MoS2 and CNTs/CH with Li2S6. To evaluate the effect of NMCS@MoS2-CNTs/CH on the performance of the LSBs, CV and galvanostatic charge-discharge test of the LSBs are tested with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH in the between 1.8 and 2.8V. Fig. 7a, b and c reveals the 1st to 5th CV profiles of LSBs with the NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH. Two reduction peaks at about 2.4 and 2.0 V indicate that S8 is reduced to long-chain LiPS (Li2Sx, 4 ≤ x ≤ 8) and the conversion from long-chain LiPSs to Li2S2/Li2S, while the one oxidation peak is put down to the oxidation of Li2S2/Li2S to S8. As shown in Fig. 7c, the high coincidence of the CV curves of the LSBs with NMCS@MoS2/S-CNTs/CH from the 1st to 5th cycles imply the electrode holding excellent reversibility and low polarization. From 18


Page 18 of 41

Page 19 of 41 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 1st to 5th cycles, in contrast to the LSBs with NMCS/S and NMCS@MoS2/S, the LSBs with NMCS@MoS2/S-CNTs/CH show better curve overlap and higher peak currents, which indicates that LSBs with NMCS@MoS2/S–CNTs/CH possessing excellent cycle stability, fast kinetics and high capacity because of the high conductivity of CNTs and the strong chemistry adsorption of MoS2 and chitosan with LiPSs. The galvanostatic charge-discharge test of the LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH are conducted at 0.1 C shown in Fig, d, e and f. The LSBs with NMCS/S and NMCS@MoS2/S deliver original capacity of 1211 and 1302 mAh g-1 with potential polarization of 205 and 188 mV. While the LSBs with NMCS@MoS2/S–CNTs/CH demonstrates higher original capacity of 1375 mAh g-1 and lower potential polarization of 163 mV, which illustrates

faster

redox

reaction

kinetics

NMCS@MoS2/S-CNTs/CH.

19


for

the

LSBs

with


Figure 7. CV and galvanostatic charge-discharge profiles of NMCS/S (a, d), NMCS@MoS2/S (b, e) and NMCS@MoS2/S-CNTs/CH (c, f). LSBs with NMCS/S, NMCS@MoS2/S and NMCS/S-CNTs/CH, deliver initial capacity of 780, 891 and 890 mAh g-1 with fast capacity decay of 0.3 %, 0.18 % and 0.2 % per cycle after 200 cycles at 0.5 C as shown in Fig. 8a. The rapid capacity decay of LSBs with NMCS/S mainly due to the dissolution and migration of LiPSs and subsequent deposition of Li2S2 and Li2S on the surface of the lithium anode during successive charge/discharge process, which leads to safety issues. The polar MoS2 and CNTs/CH play a certain role in inhibiting the “shuttle effect” of LiPSs, and the corresponding electrochemical performance is significantly improved. The LSBs 20


Page 20 of 41

Page 21 of 41 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


with NMCS@MoS2/S-CNTs/CH present more stable cycle performances conversely. The LSBs with NMCS@MoS2/S-CNTs/CH deliver higher initial capacity of 893 mAh g-1 with a very low capacity decay of 0.04 % after 200 cycles. At the same time, in order to compare the effects of CNTs and CH on the performances of LSBs, LSBs with NMCS@MoS2/S-CNTS and NMCS@MoS2/S-CH are tested at 0.5 C. The LSBs with NMCS@MoS2/S-CNTS delivers higher discharge capacity than the LSBs with NMCS@MoS2/S-CH before 100 cycles because the conductivity of CNTs is higher than one of CH. On the other hand, the capacity decay of the LSBs with NMCS@MoS2/S-CH (0.13 %) is lower than LSBs with NMCS@MoS2/S-CNTs (0.15 %), the good cycle performance can be attributed to the inhibition of the shuttle effect of LiPSs by chitosan. The rate performances of the LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH at the current rate range from 0.1 to 1 C are revealed in Fig. 8b. The reversible discharge capacities of the LSBs with the NMCS@MoS2/S-CNTs/CH are 1250, 1134, 904 and 843 mAh g-1 at 0.1, 0.2, 0.5 and 1 C, respectively. And the specific capacity of 1210 mAh g-1 when the current density back to 0.1 C. It is nearly close to the original capacity and higher than the LSBs with NMCS/S and NMCS@MoS2/S. Simultaneously, the rate performance of LSBs with NMCS@MoS2/S is much better than with NMCS/S, which is owed to the strong affinity between MoS2 and LiPSs. As shown in Fig. 8d, the LSBs with NMCS@MoS2/S-CNTs/CH are tested to investigate the long-term cycle stability at high rate of 1 C for 500 cycles. The LSBs with NMCS@MoS2/S-CNTs/CH deliver high initial specific capacity of 847 mAh g-1 with a slight capacity attenuation of 21



Page 22 of 41

0.08 % per cycle after 500 cycles, demonstrating outstanding cycle stability over long cycle life. The high areal active material mass loading is a general strategy to improve the energy density of LSBs. LSBs with NMCS@MoS2/S-CNTs/CH have high areal active material mass loading about 4.2 mg cm-2, and can deliver high peak capacity of 690 mAh g-1 and high capacity retention of 89. 2 % after 200 cycles at 0.5 C. In

addition,

the

electrochemical

performance

of

LSBs

with

NMCS@MoS2/S-CNTs/CH compared with other similar research work is listed in Table 1.

46-51

Evidently, this work shows outstanding electrochemical performance,

good long-term cycle stability and high areal active material mass loading. EIS

spectra

of

the

LSBs

with

NMCS/S,

NMCS@MoS2/S

and

NMCS@MoS2/S-CNTs/CH are presented in Fig. 8c. The equivalent circuit mold in the inset of Fig. 8c is employed to analyze and explain the impedance spectra, in which Rs is the electrolyte resistance, Rct associated with charge transfer and CPE is equivalent to capacitor. Warburg impedance (W) represents the slope of the line. Rct and Rs of the LSBs with the NMCS@MoS2/S are smaller than the LSBs with the NMCS/S, which indicates that interface properties are improved by the introduction of

MoS2.

Furthermore,

the

Rct

and

Rs

of

the

LSBs

with

the

NMCS@MoS2/S-CNTs/CH are smaller than the LSBs with the NMCS@MoS2/S because the CNTs/CH has large number of active sites of chitosan and good electronic conductivity of CNTs.

22


Page 23 of 41 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 8. (a) Cycle stabilities of LSBs with NMCS/S, NMCS@MoS2/S, NMCS /S-CNTs/CH,

NMCS@MoS2/S-CNTs,

NMCS@MoS2/S-CH

and

NMCS@MoS2/S-CNTs/CH at 0.5 C, (b) rate performances of LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH, (c) Nyquist plots of LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH, (d) long-term cycling performance of NMCS@MoS2/S-CNTs/CH at 1 C, (e) cycle stability of LSBs with 23



NMCS@MoS2/S-CNTs/CH

with

high

areal

active

Page 24 of 41

material

mass

loading

approximately 4.2 mg cm-2 at 0.5 C. Table.1 Comparison of the results with other literature Sample

NMCS@MoS2/ S-CNTs/CH

Ti3C2/S-Ti3C2/ PP S/Co3O4 MoS2-rGO/S S/NiS@C-HS S@MPC-DHSs NSF-S

Areal active material mass loading (mg cm-2 ) 1.2

Rates

Cycles

Initial capacity (mAh g-1)

Reversible capacity (mAh g-1)

Ref

0.5 C

200

894

826

This work

1.2 4.0 0.8-1.0

1C 0.5 C 0.5 C

500 200 200

0.8 0.85 2.6 0.6-0.9 4.0

0.2 C 1C 0.5 C 0.5 C 0.6 C

200 300 300 1000 150

847 690 About 820 1164 872 723 800 Not mentioned

501 616 About 400 644 480 695 400 414

46

47 48 49 50 51

Therefore, above test results make clear that holistic design of NMCS@MoS2/S and CNTs/CH plays a vital role in inhibiting the “shuttle effect” of LiPSs and improving the electrochemical performance of LSBs.

Conclusion In summary, a holistic design with NMCS@MoS2/S cathode and CNTs/Chitosan modified separator is proposed to inhibit the “shuttle effect” of LiPSs in LSBs. As a host material equipped with highly conductive carbon and highly polar MoS2, NMCS@MoS2 not only availably adsorbs LiPSs, but also significantly improves the 24


Page 25 of 41 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 reaction kinetics. The CNTs/CH modified separator plays a dual-functional role in the LSBs and further enhances LSBs electrochemical performances because the CNTs layer of CNTs/CH modified separator as a highly conductive layer can boost not only Li+ ion transfer, but also sulfur utilization, and chitosan further can effectively reinforce LiPSs adsorption capacity by way of a large amount of amino and hydroxyl groups in the chitosan molecule. The LSBs with the NMCS@MoS2/S-CNTs/CH deliver a reversible specific capacity of 501 mAh g-1 with a slight capacity attenuation of 0.08 % per cycle after 500 cycles. Therefore, the holistic design strategy for LSBs can enhance fully sulfur loading, restrain LiPSs shuttle effect and increase cycle stability, which are necessary to meet the requirements of high energy density and long-term stability of large-scale commercialization of LSBs.

Acknowledgments This work is supported financially by National Key Research and Development Program of China (2018YFB0104204), the National Natural Science Foundation of China (No. 51272221), the Hunan Provincial Innovation Foundation for Postgraduate (CX2017B292) and the Key Project of Strategic New Industry of Hunan Province (No. 2016GK4005 and 2016GK4030).

References [1] Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J. M. Li-O2 and Li-S batteries with high energy storage. Nat. Mater. 2012, 11, 19-29. 25



[2] Pang, Q.; Liang, X.; Kwok, C.Y.; Kulisch, J.; Nazar, L.F. A Comprehensive Approach toward Stable Lithium-Sulfur Batteries with High Volumetric Energy Density. Adv. Energy Mater. 2017, 7, 1601630. [3] Song, X. S; Li, X. F.;

Bai, Z. M.; Yan, B.; Xiong, D. B.; Lin, L. X.; Zhao, H.;

Li, D. J.; Shao, Y. Y. Rationally-designed configuration of directly-coated Ni3S2/Ni electrode by RGO providing superior sodium storage. Carbon, 2018, 133, 14-22. [4] Xiong, D. B.; Li, X. F.; Bai, Z. M.; Lu, S. G. Recent Advances in Layered Ti3C2Tx MXene for Electrochemical Energy Storage. Small 2018, 14, e1703419. [5] Seh, Z. W.; Sun, Y. M.; Zhang, Q. F.; Cui, Y. Designing high-energy lithium-sulfur batteries. Chem. Soc. Rev. 2016, 45, 5605-5634. [6] Manthiram, A.; Fu, Y. Z.; Chung, S.-H.; Zu, C. X.; Su, Y.-S. Rechargeable lithium-sulfur batteries. Chem. Rev. 2014, 114, 11751-11787. [7] Schuster, J.; He, G.; Mandlmeier, B.; Yim, T.; Lee, K. T.; Bein, T.; Nazar, L. F. Spherical ordered mesoporous carbon nanoparticles with high porosity for lithium-sulfur batteries. Angew. Chem. Int. Ed. 2012, 51, 3591-3595. [8] Fang, R. P.; Zhao, S. Y.; Sun, Z. H.; Wang, D.-W.; Cheng, H.-M.; Li, F. More Reliable Lithium-Sulfur Batteries: Status, Solutions and Prospects. Adv. Mater. 2017, 29, 1606823. [9] Hou, T.-Z.; Xu, W.-T.; Chen, X.; Peng, Hong. J.; Huang, J. Q.; Zhang, Q. Lithium Bond Chemistry in Lithium–Sulfur Batteries. Angew. Chem. Int. Ed. 2017, 56, 8178-8182. [10] Chung, S.H.; Manthiram, A. Rational Design of Statically and Dynamically Stable Lithium-Sulfur Batteries with High Sulfur Loading and Low Electrolyte/Sulfur Ratio. Adv. Mater. 2018, 30, 1705951.

26


Page 26 of 41

Page 27 of 41 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


[11] Preefer, M. B.; Oschmann, B.; Hawker, C. J.; Seshadri, R.; Wudl, F. High Sulfur Content Material with Stable Cycling in Lithium-Sulfur Batteries. Angew. Chem. Int. Ed. 2017, 129, 15314-15318. [12] Ji, X. L.; Lee, K. T.; Nazar, L. F.; A highly ordered nanostructured carbon-sulphur cathode for lithium-sulphur batteries. Nat. Mater. 2009, 8, 500-506. [13] Chen, M. F.; Jiang, S. X.; Cai, S. Y.; Wang, X. Y.; Xiang, K. X.; Ma, Z. Y.; Song, P.; Fisher, A. C. Hierarchical porous carbon modified with ionic surfactants as efficient sulfur hosts for the high-performance lithium-sulfur batteries. Chem. Eng. J. 2017, 313, 404-414. [14] Chen, M. F.; Wang, X. Y.; Cai, S. Y.; Ma, Z. Y.; Song, P.; Fisher, A. C. Enhancing the performance of lithium–sulfur batteries by anchoring polar polymers on the surface of sulfur host materials. J. Mater. Chem. A 2016, 4, 16148-16156. [15] Xu, G.Y.; Han, J. P.; Ding, B.; Nie, P.; Pan, J.; Dou, H.; Li, H. S.; Zhang, X. G. Biomass-derived porous carbon materials with sulfur and nitrogen dual-doping for energy storage. Green Chem. 2015, 17, 1668-1674. [16] Jayaprakash, N.; Shen, J.; Moganty, S. S.; Corona, A.; Archer, L .A. Porous hollow carbon@sulfur composites for high-power lithium-sulfur batteries. Angew. Chem. Int. Ed. 2011, 50, 5904-5908. [17] Zhou, G. M.; Zhao, Y. B.; Manthiram, A. Dual-Confined Flexible Sulfur Cathodes Encapsulated in Nitrogen-Doped Double-Shelled Hollow Carbon Spheres and Wrapped with Graphene for Li-S Batteries. Adv. Energy Mater. 2015, 5, 1402263. [18] Ahn, W.; Kim, K.-B.; Jung, K.-N.; Shin, K.-H.; Jin, C.-S. Synthesis and electrochemical properties of a sulfur-multi walled carbon nanotubes composite as a cathode material for lithium sulfur batteries. J. Power Sources 2012, 202, 394-399. 27



[19] Zhang, Z.; Kong, L.-L.; Liu, S.; Li, G.-R.; Gao, X.-P. A High-Efficiency Sulfur/Carbon Composite Based on 3D Graphene Nanosheet@Carbon Nanotube Matrix as Cathode for Lithium-Sulfur Battery, Adv. Energy Mater. 2017, 7, 1602543. [20] Guo, J. C.; Xu, Y. H.; Wang, C. S. Sulfur-impregnated disordered carbon nanotubes cathode for lithium-sulfur batteries. Nano Lett. 2011, 11, 4288-4294. [21] Zu, C. X.; Manthiram, A. Hydroxylated Graphene-Sulfur Nanocomposites for High-Rate Lithium-Sulfur Batteries. Adv. Energy Mater. 2013, 3, 1008-1012. [22] Tang, C.; Zhang, Q.; Zhao, M.-Q.; Huang, J-Q.; Cheng, X.-B.; Tian, G-L.; Peng, H. J.; Wei, F. Nitrogen-doped aligned carbon nanotube/graphene sandwiches: facile catalytic growth on bifunctional natural catalysts and their applications as scaffolds for high-rate lithium-sulfur batteries. Adv. Mater. 2014, 26, 6100-6105. [23] Chen, K.; Sun, Z. H.; Fang, R. P.; Shi, Y.; Cheng, H.-M.; Li, F. Metal-Organic Frameworks (MOFs)-Derived Nitrogen-Doped Porous Carbon Anchored on Graphene with Multifunctional Effects for Lithium-Sulfur Batteries. Adv. Funct. Mater. 2018, 1707592. [24] Niu, S. Z.; Lv, W.; Zhou, G. M.; He, Y. B.; Li, B. H.; Yang, Q.-H.; Kang, F. Y. N and S co-doped porous carbon spheres prepared using l-cysteine as a dual functional agent for high-performance lithium–sulfur batteries. Chem. Commun. 2015, 51, 17720-17723. [25] Ruan, J. F.; Yuan, T.; Pang, Y. P.; Luo, S. N.; Peng, C. X.; Yang, J. H.; Zheng, S.Y.; Nitrogen and sulfur dual-doped carbon films as flexible free-standing anodes for Li-ion and Na-ion batteries. Carbon 2018, 126, 9-16. [26] Zhou, G. M.; Paek, E.; Hwang, G. S.; Manthiram, A. Long-life Li/polysulphide batteries with high sulphur loading enabled by lightweight three-dimensional nitrogen/sulphur-codoped graphene sponge. Nat. Commun. 2015, 6, 7760. 28


Page 28 of 41

Page 29 of 41 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


[27] Li, Z.; Zhang, J. T.; Guan, B. Y.; Wang, D.; Liu, L.-M.; Lou, X.W. A sulfur host based on titanium monoxide@carbon hollow spheres for advanced lithium-sulfur batteries. Nat. Commun. 2016, 7, 13065. [28] Chen, M. F.; Lu, Q.; Jiang, S. X.; Huang, C.; Wang, X. Y.; Wu, B.; Xiang, K. X.; Wu, Y. T. MnO2 nanosheets grown on the internal/external surface of N-doped hollow porous carbon nanospheres as the sulfur host of advanced lithium-sulfur batteries. Chem. Eng. J. 2018, 335, 831-842. [29] Lei, T. Y.; Chen, W. Huang, J. W.; Yan, C. Y.; Sun, H. X.; Wang, C.; Zhang, W. L.; Li, Y. R.; Xiong, J. Multi-Functional Layered WS2 Nanosheets for Enhancing the Performance of Lithium-Sulfur Batteries. Adv. Energy Mater. 2017, 7, 1601843. [30] Lin, H. B.; Yang, L. Q.; Jiang, X.; Li, G. C.; Zhang, T. R.; Yao, Q. F.; Zheng, G. Y. W.; Lee, J. Y. Electrocatalysis of polysulfide conversion by sulfur-deficient MoS2 nanoflakes for lithium–sulfur batteries. Energy Environ. Sci. 2017, 10, 1476-1486. [31] Chen, T.; Zhang, Z. W.; Cheng, B. R.; Chen, R. P.; Hu, Y.; Ma, L. B.; Zhu, G. Y.; Liu, J.; Jin, Z. Self-Templated Formation of Interlaced Carbon Nanotubes Threaded Hollow Co3S4 Nanoboxes for High-Rate and Heat-Resistant Lithium-Sulfur Batteries. J. Am. Chem. Soc. 2017, 139, 12710-12715. [32] Sun, Z. H.; Zhang, J. Q.; Yin, L. C.; Hu, G. J.; Fang, R. P.; Cheng, H.-M.; Li, F. Conductive porous vanadium nitride/graphene composite as chemical anchor of polysulfides for lithium-sulfur batteries. Nat. Commun. 2017, 8, 14627. [33] Cui, Z. M.; Zu, C. X.; Zhou, W. D.; Manthiram, A.; Goodenough, J. B. Mesoporous Titanium Nitride-Enabled Highly Stable Lithium-Sulfur Batteries. Adv. Mater. 2016, 28, 6926-6931. [34] Li, X. X.; Ding, K.; Gao, B.; Li, Q. W.; Li, Y. Y.; Fu, J. J.; Zhang, X. M.; Chu, P. K.; Huo. K. Freestanding carbon encapsulated mesoporous vanadium nitride 29



nanowires enable highly stable sulfur cathodes for lithium-sulfur batteries. Nano Energy 2017, 40, 655-662. [35] Fang, R. P.; Zhao, S. Y.; Sun, Z. H.; Wang, D-W.; Amal, R.; Wang, S. G.; Cheng, H-M.; Li, F. Polysulfide immobilization and conversion on a conductive polar MoC@MoOx material for lithium-sulfur batteries. Energy Storage Mater. 2018, 10, 56-61. [36] Bao, W. Z.; Su, D. W.; Zhang, W. X.; Guo, X.; Wang, G. X.; 3D Metal Carbide@Mesoporous Carbon Hybrid Architecture as a New Polysulfide Reservoir for Lithium-Sulfur Batteries. Adv. Funct. Mater. 2016, 26, 8746-8756. [37] Lu, Y.; Gu, S.; Guo, J.; Rui, K.; Chen, C. H.; Zhang, S. P.; Jin, J.; Yang, J. H.; Wen, Z. Y. Sulfonic Groups Originated Dual-Functional Interlayer for High Performance Lithium-Sulfur Battery. ACS Appl. Mater. Interfaces 2017, 9, 14878-14888. [38] Ghazi, Z. A.; He, X.; Khattak, A. M.; Khan, N. A.; Liang, B.; Iqbal, A.; Wang, J. X.; Sin, H.; Li, L. S.; Tang, Z. Y. MoS2/Celgard Separator as Efficient Polysulfide Barrier for Long-Life Lithium-Sulfur Batteries. Adv. Mater. 2017, 29, 1606817. [39] Liu, M.; Li, Q.; Qin, X. Y.; Liang, G. M.; Han, W. J.; Zhou, D.; He, Y.-B.; Li, B. F.; Kang, F. Y. Suppressing Self-Discharge and Shuttle Effect of Lithium-Sulfur Batteries with V2O5-Decorated Carbon Nanofiber Interlayer. Small 2017, 13, 1602539. [40] Fan, Y.; Yang, Z.; Hua, W. X.; Liu, D.; Tao, T.; Rahman, M. M.; Lei, W. W.; Huang, S. M.; Chen, Y. Functionalized Boron Nitride Nanosheets/Graphene Interlayer for Fast and Long-Life Lithium-Sulfur Batteries. Adv. Energy Mater. 2017, 7, 1602380.

30


Page 30 of 41

Page 31 of 41 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


[41] Jiang, S. X.; Chen, M. F., Wang, X. Y., Zhang, Y., Huang, C., Zhang, Y. P., Wang, Y. Honeycomb-like Nitrogen and Sulfur Dual-Doped Hierarchical Porous Biomass Carbon Bifunctional Interlayer for Advanced Lithium-Sulfur Batteries. Chem. Eng. J. 2018, https://doi.org/10.1016/j.cej.2018.08.170. [42] Hu, N. N.; Lv, X. S.; Dai, Y.; Fan, L. L.; Xiong, D. B.; Li, X. F. SnO2/Reduced Graphene Oxide Interlayer Mitigating the Shuttle Effect of Li-S Batteries. ACS Appl. Mater. Interfaces 2018, 10, 18665-18674. [43] Jiao, J. Q.; Fu, J. Y.; Wei, Y. H.; Zhao, Z.; Duan, A. J.; Xu, C. M.; Li, J. M.; Song, H.; Zheng, P.; Wang, X. L.; Yang, Y. N.; Liu, Y. Al-modified dendritic mesoporous silica nanospheres-supported NiMo catalysts for the hydrodesulfurization of dibenzothiophene: Efficient accessibility of active sites and suitable metal–support interaction. J. Catal. 2017, 356, 269-282. [44] Chen, B.; Meng, Y. H.; He, F.; Liu, E. Z.; Shi, C. S.; He, C. N.; Ma, L. Y.; Li, Q. Y.; Li, J. J.; Zhao, N. Q. Thermal decomposition-reduced layer-by-layer nitrogen-doped

graphene/MoS2/nitrogen-doped

graphene

heterostructure

for

promising lithium-ion batteries. Nano Energy 2017, 41, 154-163. [45] Tan, L.; Li, X. H.; Wang, Z. X.; Guo, H. J.; Wang, J. X. Lightweight Reduced Graphene Oxide@MoS2 Interlayer as Polysulfide Barrier for High-Performance Lithium-Sulfur Batteries. ACS Appl. Mater. Interfaces 2018, 10, 3707-3713. [46] Dong, Y. F.; Zheng, S. H.; Qin, J. Q.; Zhao, X. J.; Shi, H. D.; Wang, X. H.; Chen, J.; Wu, Z-S. All-MXene-Based Integrated Electrode Constructed by Ti3C2 Nanoribbon Framework Host and Nanosheet Interlayer for High-Energy-Density Li-S Batteries. ACS Nano 2018, 12, 2381-2388. [47] Wang, H. Q.; Zhou, T. F.; Li, D.; Gao, H.; Gao, G. P.; Du, A. J.; Liu, H. K.; Guo, Z. P. Ultrathin Cobaltosic Oxide Nanosheets as an Effective Sulfur Encapsulation 31



Matrix with Strong Affinity Toward Polysulfides. ACS Appl. Mater. Interfaces 2017, 9, 4320-4325. [48] You, Y.; Ye, Y. W.; Wei, M. L.; Sun, W. J.; Tang, Q.; Zhang, J.; Chen, X.; Li, H. Q.; Xu, J. Three-dimensional MoS2/rGO foams as efficient sulfur hosts for high-performance lithium-sulfur batteries. Chem. Eng. J. 2019, 355, 671-678. [49] Ye, C.; Zhang, L.; Guo, C. X.; Li, D. D.; Vasileff, A.; Wang, H. H.; Qiao, S.-Z. A 3D Hybrid of Chemically Coupled Nickel Sulfide and Hollow Carbon Spheres for High Performance Lithium-Sulfur Batteries. Adv. Funct. Mater. 2017, 27, 1702524. [50] Wang, Q.; Wang, Z.-B.; Li, C.; Gu, D.-M., High sulfur content microporous carbon coated sulfur composites synthesized via in situ oxidation of metal sulfide for high-performance Li/S batteries. J. Mater. Chem. A 2017, 5, 6052-6059. [51] Li, Z.; Zhang, S. G.; Zhang, J. H.; Xu, M.; Tatara, R.; Dokko, K.; Watanabe, M. Three-Dimensionally Hierarchical Ni/Ni3S2/S Cathode for Lithium-Sulfur Battery. ACS Appl. Mater. Interfaces 2017, 9, 38477-38485.

32


Page 32 of 41

Page 33 of 41 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


TOC graphic:

Synopsis: LSBs with NMCS@MoS2/S-CNTs/CH can meet the requirements of high energy density and long-term stability of large-scale commercialization of LSBs.

33



Figure 1. (a) Schematic diagram of the synthesis process of NMCS@MoS2/S composite, (b) Schematic diagram adsorption of polysulfide by chitosan.


Page 34 of 41

Page 35 of 41 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.SEM images of (a, b) DMCSs, (c, d) NMCS, (e, f) NMCS@MoS2, (g) TEM images of NMCS, (h) HRTEM images of NMCS, (i, k) TEM images of NMCS@MoS2 (j) HRTEM images of NMCS@MoS2, elemental mappings of (l) carbon, (m) nitrogen (n) molybdenum (o) sulfur.



Figure. 3 Digital photos of (a) CNTs/CH modified separator, (b) CNTs/CH modified separator after be folded several times, (c) SEM images of surface of CNTs/CH modified separator, (d) cross section of CNTs/CH modified separator.


Page 36 of 41

Page 37 of 41 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. N2 adsorption/desorption isotherms and pore size distributions of NMCS (a, d), NMCS@MoS2 (b, e) and NMCS@MoS2/S (c, f).



Figure 5. (a) XRD pattern of NMCS and NMCS@MoS2, (b) XRD pattern of NMCS/S and NMCS@MoS2/S, (c) TGA traces, sulfur contents of NMCS/S and NMCS@MoS2 in N2, carbon contents of NMCS@MoS2 in air, (d) Raman spectra of NMCS and NMCS@MoS2, (e) XPS measure spectrum of NMCS and NMCS@MoS2, (f) C 1s, (g) N 1s, (h) Mo 3d, (i) S 2p.


Page 38 of 41

Page 39 of 41 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. 6 UV/Vis adsorption spectra and adsorption ability tests of NMCS, NMCS@MoS2 and CNTs/CH with Li2S6.



Figure 7. CV and galvanostatic charge-discharge profiles of NMCS/S (a, d), NMCS@MoS2/S (b, e) and NMCS@MoS2/S-CNTs/CH (c, f).


Page 40 of 41

Page 41 of 41 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 8. (a) Cycle stabilities of LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH at 0.5 C, (b) rate performances of LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH, (c) Nyquist plots of LSBs with NMCS/S, NMCS@MoS2/S and NMCS@MoS2/S-CNTs/CH, (d) long-term cycling performance of NMCS@MoS2/S-CNTs/CH at 1C, (e) Cycle stability of LSBs with NMCS@MoS2/S-CNTs/CH with high areal sulfur loading about 4.2 mg cm-2 at 0.5 C.


MoS2-Coated N-doped Mesoporous Carbon Spherical Composite

Recommend Documents