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Ultrafine TiO2 Confined in Porous-Nitrogen-Doped Carbon from Metal−Organic Frameworks for High-Performance Lithium Sulfur Batteries Yongling An,† Zhen Zhang,† Huifang Fei,† Shenglin Xiong,‡ Bing Ji,§ and Jinkui Feng*,† †
Key Laboratory for Liquid−Solid Structural Evolution & Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jinan 250061, P.R. China ‡ School of Chemistry and Chemical Engineering and §School of Control Science and Engineering, Shandong University, Jinan 250100, P.R. China S Supporting Information *
ABSTRACT: Ultrafine TiO2 confined in porous-nitrogen-doped carbon is synthesized from a single metal−organic framework precursor. As a novel interlayer for lithium−sulfur batteries, the TiO2@NC composite can act as both a high efficiency lithium polysulfide barrier to suppress the side reactions and an additional current collector to enhance the polysulfide redox reactions. The lithium−sulfur battery with a TiO2@NC interlayer delivers a high reversible capacity of 1460 mAh g−1 at 0.2 C and capacity retention of 71% even after 500 cycles with high rate capability.
KEYWORDS: lithium−sulfur battery, metal−organic framework, TiO2, nitrogen-doped carbon, interlayer
1. INTRODUCTION With the development of advanced portable electronics and electrical vehicles (EVs), there is an urgent demand for highenergy-density power sources.1 Lithium−sulfur batteries have attracted great attention due to their high theoretical specific capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1).2,3 However, there are several key issues that hinder the commercialization of lithium−sulfur batteries: (1) Dissolution of polysulfide intermediates Li2Sx (2 < x < 8) during reaction leads to the shuttle effect, which deteriorates Coulombic efficiency, corrodes the lithium anode, and depresses sulfur utilization, causing rapid fading of capacity. (2) Large volume changes (80%) during the lithiation/delithiation process may destroy the conductive network of the electrode and accelerate the dissolution of polysulfide intermediates. (3) Low ionic and electronic conductivity of sulfur and Li2Sx may lead to insufficient utilization of active materials and limit rate performance.4−8 To overcome these problems, several strategies have been developed, such as constructing conductive matrix−sulfur composites,9−16 using low-polysulfide-soluble electrolytes,17 modifying lithium metal anodes,18 adding an interlayer,19−23 and introducing polysulfide reservoirs.24,25 Sulfur-confined porous conductive networks (such as porous carbon,10,11 carbon nanotubes,12,13 graphene,14,15 conducting polymers,14,16 etc.) are the most popular strategy, as they can act not only as © XXXX American Chemical Society
electronic conductive agents but also as volume change buffers and lithium polysulfide barriers.10,12,14 Recently, Wang26 et al. found that porous-nitrogen-doped carbon was an ideal choice to host lithium batteries, as it can promote chemical bonding between carbon and polysulfide chains. Mesoporous-nitrogendoped carbon−sulfur cathodes show excellent cycling stability (95% capacity retention within 100 cycles) at high rate and high sulfur content (70%).27,28 Furthermore, some metal oxides and sulfides have proven to be effective lithium polysulfide reservoirs which can retain lithium polysulfide via strong physical/chemical adsorption and include TiOx,29−32 FeS2,33 SiO2,34 Al2O3,35 MnO2,36 etc. Among them, TiO2 has proven to be particularly promising due to its outstanding adsorption ability.31,32 However, the semiconductor character lowers its electrochemical reversibility.30 It has been proven that combining the porous carbon and lithium polysulfide reservoirs can bring synergetic advantages.37,38 Nazar et al. found that 4% mesoporous titania added to a sulfur/carbon composite can lessen polysulfide dissolution and significantly improve the capacity retention of the Li−S battery.37,38 Recently, Yu et al. found that uniform distribution of TiO2 is a key factor for long cycling life. By Received: December 27, 2016 Accepted: March 22, 2017
A
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces
2. RESULTS AND DISCUSSION The crystal structure of the synthesized samples was measured by the XRD method. From Figure 2a we can see that the XRD patterns of as-synthesized NH2-MIL-125(Ti) and TiO2@NC are indexed well with the standard data.46−51 The structure of MIL-125(Ti) includes the chains of the μ-OH corner-sharing TiO6 octahedron, which is interknitted with NH2-BDC molecules to constitute three-dimensional pores.46,47 The XRD patterns of TiO2@NC at 600 °C (Figure 2a) fit well with the pure anatase structure (JCPDS, no. 21-1272), and the weak peaks suggest a polycrystalline structure with fine crystallite size, which is beneficial to adsorb the polysulfide.51−53 To evaluate the content of carbon in TiO2@NC, TGA was performed. The TGA result reveals that TiO2@NC undergoes two stages of weight loss, as shown in the Figure 2b. A slow weight loss of 4% assigned in the first stage between 30 and 200 °C is due to the residual absorbed water and DMF molecules. The main weight loss (about 52%) occurred in the second stage between 300 and 700 °C, attributed to the oxidation of carbon.54,55 Furthermore, the porous properties of TiO2@NC was investigated by BET, as illustrated in Figure 2c. The N2 adsorption−desorption isotherms feature an appropriate BET surface of 155 m2 g−1, and the distribution of pore size indicated that TiO2@NC is an emblematical mesoporous material with an average pore diameter of about 2 nm (Figure S3). The large specific surface can also facilitate the absorbance of polysulfides to improve the electrochemical performance of lithium−sulfur batteries.30,50 Furthermore, the electronic state and chemical composition of TiO2@NC was examined by XPS. The representative XPS spectrum of binding energies from 0 to 1000 eV is shown in Figure 2d. This result confirms the existence of carbon, nitrogen, oxygen, and titanium elements, as indicated by the peaks of Ti 2p (at 456 eV, Figure S4), C 1s (at 285 eV, Figure S5), N 1s (at 398 eV, Figure S6), and O 1s (at 531 eV).56−59,63 The content of N in the NH2-BDC ligands is estimated to be 1.5% by XPS (by weight). N doping can provide an additional adsorption of lithium polysulfides, improving the cycling performance.26 The Raman spectra (Figure S7) demonstrate that the composites are composed of anatase TiO2 and carbon which act as electronic conductive agents and lithium polysulfide barriers, depressing the occurrence of the shuttle effect.10,21 The electronic conductivity of TiO2@NC is about 200 mS cm−1 compared to 10−7 mS cm−1 of pure TiO2. The surface morphologies of TiO2@NC were analyzed by FESEM. As shown in Figure 3a, TiO2@NC displays a tetrahedron shape with an average particle size of 150−200 nm. Moreover, the TiO 2 @NC surface has a porous character.50,54 To provide detailed insight into the microstructure of TiO2@NC, HR-TEM was also performed. Figure 3b and 3c shows the typical TEM images of TiO2@NC at different magnifications. TiO2@NC exhibits a porous structure with fine crystals confined in a porous carbon web. The porous carbon structure can not only absorb and retain Li2Sx but can also provide a conductive network to facilitate the redox reaction of lithium polysulfides, which may further improve the electrochemical performance of the lithium−sulfur battery. The polycrystalline character of TiO2@NC was substantiated by HR-TEM (Figure 3d) that shows that the TiO2 nanoparticles with the average diameter of 5−10 nm are surrounded by amorphous carbon, which are marked by the red circle. This result was confirmed by results calculated from Scherrer’s
depositing well-dispersed TiO2 on a nitrogen-doped graphene/ sulfur electrode via atomic layer deposition (ALD), a high capacity retention of 86% is retained after 500 cycles.30 However, it remains a challenge to produce uniform TiO2− porous carbon complexes on a large scale and for low cost. Recently, introducing an electronic conductive interlayer between the cathode and separator has been proven to be a facile and inexpensive method to improve the electrochemical performance of lithium−sulfur batteries.19−23 A porous conductive interlayer can not only act as an additional current collector to enhance the utilization of the active material but can also block polysulfide migration.39 This method does not require the formation of complicated sulfur−conductive matrix composites and leads to facile and inexpensive manufacturing.20−23 For example, Manthiram et al. reported that with microporous carbon paper as a bifunctional interlayer, lithium− sulfur batteries can retain 85% of initial capacity after 100 cycles and a high rate of 846 mAh g−1 at 3 C.19 It can be expected that a fine porous TiO2/nitrogen-doped carbon would be an ideal choice as an interlayer.30 In this paper, we present the electrochemical performance of lithium−sulfur batteries with ultrafine TiO2 confined in a porous-nitrogen-doped carbon web from an MOF as the interlayer (Figure 1). The MOF consists of metal ions or
Figure 1. Schematic of the synthesis of TiO2@NC crystals and the charge−discharge process of the lithium−sulfur battery with TiO2@ NC as the interlayer.
clusters coordinated to organic ligands with repeated units and many pores.40,41 The syntheses of porous materials from MOFs have attracted attention due to the simple preparation process, the adjustable porous structure, the uniform distribution of metal elements, and the high carbon yield.42−44 After heat treatment, the MOF is converted into metal-element-confined carbon materials with retained intrinsic porous structure.45 The nitrogen-doped carbon can not only restrain the particle size of TiO2 and enhance the electronic conductivity but can also provide additional lithium polysulfide adsorption. The cumulative advantages of the nitrogen-doped porous carbon and uniformly dispersed ultrafine TiO2 afford better polysulfide absorption and good electronic conductivity.30,31 Lithium− sulfur batteries with the TiO2@NC interlayer exhibited ultralong cycle life and excellent rate performance. B
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces
Figure 2. (a) XRD patterns of NH2-MIL-125(Ti) and TiO2@NC. (b) TGA curve. (c) Nitrogen adsorption−desorption isotherm. (d) XPS spectra of TiO2@NC.
three cyclic voltammetry (CV) curves of the blank and TiO2@ NC-interlayer-included lithium−sulfur batteries between 1.9 and 3 V at a rate of 0.1 mV s−1. Both curves demonstrate two pairs of sharp redox peaks which represent the typical electrochemical oxidation and reduction of sulfur occurring in two intervals during the charge−discharge process.4,5 The first cathodic peak located at 2.3 V is ascribed to the reduction of elemental sulfur to lithium polysulfide (Li2Sx, 4 < x < 8). The second cathodic peak at 2.0 V involves the further reduction of lithium polysulfide to Li2S2 and finally to Li2S. The anodic scan also involves two intervals. The anodic peak at 2.35 V is related to the formation of Li2Sx (x > 2), and the reaction process continues until the lithium polysulfide is exhaustively depleted. Finally, elemental sulfur is generated at about 2.4 V.60 From the figures we can see that the curves of the lithium−sulfur battery with the TiO2@NC interlayer are similar to that of the blank lithium−sulfur battery, indicating the same charge−discharge mechanism. To further clarify the effect of the TiO2@NC interlayer on the charge−discharge character of the lithium− sulfur battery, the CV of the TiO2@NC/Li cell was also probed. One definite reduction peak appeared at 1.75 V corresponding to the intercalation of lithium ion in the titanium dioxide host. The reduction potential is lower than the full discharge voltage, indicating that TiO2@NC does not participate during the cycling process of the lithium−sulfur battery.41,42 Figure 4c and 4d shows the 1st, 2nd, and 500th charge−discharge profile of the lithium−sulfur battery with and without TiO2@NC as an interlayer between 1.9 and 3 V at a current density of 1 C (1 C = 1680 mAh g−1). Both show the typical double plateau charge−discharge curve, indicating a similar charge and discharge mechanism, which is consistent with the CV results. The high voltage platform corresponds to the reaction where sulfur is reduced to Li2Sx (4 < x < 8). The low voltage platform is related to the transition from Li2Sx to Li2S2 and Li2S. Specifically, the lithium−sulfur battery with the
Figure 3. (a) SEM image. (b, c) TEM image. (d) High resolution TEM (HRTEM) image with (101) d-spacing indicated and selected area electron diffraction (SAED) pattern of TiO2@NC.
equation based on the XRD pattern. The lattice fringes of 0.352 nm correspond to the (101) plane of the anatase structure. The selected area electron diffraction (SAED) pattern on the bottom left of Figure 3d demonstrates several diffraction rings, (101), (004), (200), (105), which proves a polycrystalline structure composed of anatase nanocrystals. The well-dispersed ultrafine TiO2 particles provide more adsorption sites while the porous N-doped carbon can act as a host for polysulfides, an electronic and ion conductive matrix, and additional polysulfide barriers.31,32,46−48,54−59 The electrochemical performance of the lithium−sulfur battery with and without an interlayer of TiO2@NC was evaluated by cyclic voltammetry (CV) and static-current charge/discharge cycling. Figure 4a and 4b reveals the initial C
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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Figure 4. Electrochemical performance of the lithium−sulfur battery with and without an interlayer of TiO2@NC between 1.9 and 3.0 V. (a) Cyclic voltammetry of the blank lithium−sulfur battery at a scan rate of 0.1 mV s−1. (b) Cyclic voltammetry of the lithium-ion battery with TiO2@NC as a cathode material between 1.0 and 3.0 V and the lithium−sulfur battery with TiO2@NC as the interlayer at a scan rate of 0.1 mV s−1. (c) Galvanostatic charge−discharge voltage profiles of the blank lithium−sulfur battery at a current density of 1 C. (d) Galvanostatic charge−discharge voltage profiles of the lithium−sulfur battery with TiO2@NC as the interlayer at a current density of 1 C. (e) Cycling performance of the lithium− sulfur battery without an interlayer and TiO2@NC as the interlayer at a current density of 1 C. (f) Rate capability of the lithium−sulfur battery without an interlayer and with TiO2@NC as the interlayer at various current densities from 0.2 to 3 C.
TiO2@NC interlayer (Figure 4d) shows a capacity of 1002 mAh g−1 and 947 mAh g−1 in the first and second cycles, comparable with 998 mAh g−1 and 987 mAh g−1 of blank lithium−sulfur batteries (Figure 4c). The voltage polarity of the cell with the TiO2@NC interlayer is larger in the initial cycles, which may be ascribed to the lower lithium polysulfide diffusion rate and longer diffusion pathway caused by the interlayer. However, after 500 cycles, the polarity of blank lithium−sulfur is higher than the cell with the interlayer. This may result from the increased interface impedance on the lithium metal anode, which is caused by side reactions with lithium polysulfides.7 The enhancement mechanism was examined via inner resistance changes. The inner resistance data was tested at 1000 Hz by an inner resistance tester. The resistance of the blank cell increased from 15 Ω (before cycling) to 130 Ω (after 500 cycles), while the inner resistance of the cell with an interlayer only increased from 20 Ω to 35 Ω under the same condition. The cycling performance of the lithium−sulfur
batteries with and without the interlayer was investigated (Figure 4e). The batteries were cycled between 1.9 and 3.0 V at a current density of 1 C for 500 cycles. The reversible capacity of the blank lithium−sulfur battery decreased from 998 mAh g−1 to 220 mAh g−1 after 500 cycles, which corresponds to a capacity retention of 22.04%. For the lithium−sulfur battery with TiO2@NC as an interlayer, the reversible capacity decreased from 1002 mAh g−1 to 712 mAh g−1, maintaining a capacity retention of 71.06% and high Coulombic efficiency. The greatly improved electrochemical performance is ascribed to the lithium polysulfide barrier effect of the TiO2@NC interlayer, which not only alleviates the corrosion of the lithium metal anodes but also acts as an additional current collector for lithium−sulfur batteries.19 The cycling properties of the lithium−sulfur battery without an interlayer, and TiO2@NC and carbon black as the interlayer, are compared in Figure S8. The cycling performance of the lithium−sulfur battery with a carbon black interlayer is inferior to blank lithium−sulfur D
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces
3. CONCLUSION In summary, we successfully achieved ultrafine TiO2 confined in a porous-nitrogen-doped carbon network (TiO2@NC) from a single MOF precursor. Lithium−sulfur batteries with a TiO2@NC-based interlayer display a prolonged cycle life and outstanding rate performance, which may benefit from the stronger lithium polysulfide adsorption of both the ultrafine TiO2 and the porous-nitrogen-doped carbon network. This work may be useful for the further design and optimization of lithium−sulfur batteries.
batteries but superior to that with TiO2@NC as the interlayer after 140 cycles. So TiO2@NC can be an ideal choice as the interlayer to improve the cycling performance of lithium−sulfur batteries. Furthermore, the lithium−sulfur battery with the TiO2@NC interlayer also exhibits a favorable rate ability, as shown in Figure 4f. With an increase in current density, the lithium−sulfur batteries with a TiO2@NC interlayer can deliver a reversible capacity of 1435 mAh g−1, 1181 mAh g−1, 1001 mAh g−1, 844 mAh g−1, and 736 mAh g−1 at a current density of 0.2, 0.5, 1, 2, and 3 C, respectively. A reversible capacity of 1162 mAh g−1 can be obtained after the current density decreases to 0.2 C. For the lithium−sulfur battery without an interlayer, a specific capacity of 1408 mAh g−1, 1136 mAh g−1, 875 mAh g−1, 616 mAh g−1, and 355 mAh g−1 can be achieved at a current density of 0.2, 0.5, 1, 2, and 3 C, respectively. The specific capacity returns to 805 mAh g−1 when the rate is readjusted to 0.2 C. The rate capability of the lithium−sulfur battery with TiO2@NC as the interlayer is much better than that of the lithium−sulfur battery without an interlayer, indicating the promising properties of TiO2@NC as an interlayer.41,61−63 To directly view the adsorption character of TiO2@NC, TiO2@NC powder was dispersed in a 0.001 M THF solution of lithium polysulfides (Li2S8). As shown in Figure 5a, the brown
4. EXPERIMENTAL SECTION Synthesis of TiO2@NC Crystals. The synthesis of NH2-MIL125(Ti) crystals was achieved by a solvothermal method in N,Ndimethylformamide (DMF)−methanol (CH3OH) mixed solvent with 2-amino-1,4-benzenedicarboxylic acid (NH2-BDC) and tetrabutyl titanate (TBT) as metal root and organic linker. In the process of a typical experiment, 1.08 g (6 mmol) of NH2-BDC and 0.52 mL (1.5 mmol) of Ti(OC4H9)4 were dissolved into 18 mL of DMF and 2 mL of CH3OH to form a well-distributed solution under magnetic stirring for 30 min at room temperature. Then it was transferred to the autoclave. The autoclave was airproofed and heated at 150 °C for 72 h, and the yellow precipitate was centrifugated and washed several times with DMF and CH3OH. The products were dried in the vacuum oven at 50 °C for 12 h and calcined at 200 °C for 6 h to eliminate the dissociated solvent.46,47 Finally, it was heated at 600 °C for 10 h at a heating rate of 5 °C min−1 in a tube furnace under the N2 atmosphere, and the final products were TiO2@NC crystals.48−50 Characterization Methods. X-ray diffraction is widely used to determine the phase structure of materials. In the experiment, the XRD spectra were gathered by a Rigaku Dmaxrc diffractometer using Cu Kα radiation (V = 50 kV, I = 100 mA) at a scanning rate 4° min−1 from 5° to 80°. The morphology and size of the as-prepared samples were measured using field emission scanning electron microscopy (FESEM, SU-70) and high resolution transmission electron microscopy (HRTEM, JEOL JEM-2100). Thermogravimetric analysis (TGA, TG-209C) was accomplished in the temperature range of 30 °C to 800 °C under oxygen atmosphere at a heating rate of 5 °C min−1. The X-ray photoelectron spectroscopy (XPS, ESCALAB 250) analysis was studied with Al Kα as the X-ray source. The porous property of the surface area based on the nitrogen adsorption− desorption isotherms was tested by Brunauer−Emmett−Teller theory (BET, ASAP 2020). Raman spectra were obtained with a JY HR800 under ambient conditions, with a laser spot size of about 1 μm. Li2S8 was prepared by stirring stoichiometric amounts of S8 and Li2S in tetrahydrofuran (THF) for 48 h at room temperature. Electrochemical Measurements. The sulfur slurry was arranged by mixing 75 wt % sulfur−Ketjenblack compound (XRD patterns are provided in Figure S1 and a TGA curve revealed a sulfur loading of 80 wt % sulfur−Ketjenblack as shown in Figure S2), 10 wt % Super P carbon, and 15 wt % sodium carboxymethylmellulose (CMC) binder. The slurry was coated on aluminum foil using a current collector. After drying at 50 °C for 24 h in a vacuum oven, the electrodes were cut into small round disks with a diameter of 14 mm. The interlayer of TiO2@ NC and carbon black was prepared by blending and then roll-pressing 70 wt % TiO2@NC and 30 wt % polytetrafluoroethylene (PTFE) composites, 70 wt % super P, and 30 wt % PTFE composites, respectively. The mixture was pressed into slices and dried at 100 °C for 12 h in an air-circulated oven. Finally, small species of ⌀ 16 mm were obtained. The thickness of the interlayer is about 0.1 mm, and the weight is 1.1 mg cm−2. All the cells were installed in a glovebox and measured at room temperature. The electrochemical performance was determined by a galvanostatic programmable battery charger in a 2016 cell with a voltage range of 1.9−3.0 V at a current density of 1 C. The cyclic voltammetry properties were checked out at a scanning rate of 0.1 mV s−1 using an electrochemical workstation.
Figure 5. Adsorption mechanism of TiO2@NC. (a) Image of the pale solution of lithium polysulfides and the colorless solution after a period of time to assimilate TiO2@NC. (b) EDX spectra. (c−f) Elemental mapping images of TiO2@NC after absorbing the solution of lithium polysulfides.
polysulfide solution became almost colorless after adding TiO2@NC powder for 24 h. This indicates that TiO2@NC can well absorb polysulfide to restrain the occurrence of the shuttle effect.62 The EDX spectra (Figure 5b) reveal an abundant scatter of sulfur after absorbing polysulfide, demonstrating that the lithium polysulfide is uniformly absorbed by TiO2@NC, depressing the shuttle effect.21,31 Figure 5c−f displays the base and Ti, N, S element mapping results of TiO2@NC after absorbance of polysulfide for 24 h. The sulfur signal was found to be distributed homogeneously in TiO2@NC composites, further confirming the excellent adsorption and permeate ability of TiO2@NC composites.32,64−69 E
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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(15) Zhou, G. M.; Pei, S. F.; Li, L.; Wang, D. W.; Wang, S. G.; Huang, K.; Yin, L. C.; Li, F.; Cheng, H. M. A Graphene-Pure-Sulfur Sandwich Structure for Ultrafast, Long-Life Lithium-Sulfur Batteries. Adv. Mater. 2014, 26, 625−631. (16) Xiao, L. F.; Cao, Y. L.; Xiao, J.; Schwenzer, B.; Engelhard, M. H.; Saraf, L. V.; Nie, Z. M.; Exarhos, G. J.; Liu, J. A Soft Approach to Encapsulate Sulfur: Polyaniline Nanotubes for Lithium Sulfur Batteries with Long Cycle Life. Adv. Mater. 2012, 24, 1176−1181. (17) Liu, M.; Zhou, D.; He, Y. B.; Fu, Y. Z.; Qin, X. Y.; Miao, C.; Du, H. D.; Li, B. H.; Yang, Q. H.; Lin, Z. Q.; Zhao, T. S.; Kang, F. Y. Novel Gel Polymer Electrolyte for High-Performance Lithium-Sulfur Batteries. Nano Energy 2016, 22, 278−289. (18) Cheng, X. B.; Peng, H. J.; Huang, J. Q.; Zhang, R.; Zhao, C. Z.; Zhang, Q. Dual-Phase Lithium Metal Anode Containing a PolysulfideInduced Solid Electrolyte Interphase and Nanostructured Graphene Framework for Lithium−Sulfur Batteries. ACS Nano 2015, 9, 6373− 6382. (19) Su, Y. S.; Manthiram, A. Lithium-Sulphur Batteries with a Microporous Carbon Paper as a Bifunctional Interlayer. Nat. Commun. 2012, 3, 1166. (20) Yao, H. B.; Yan, K.; Li, W. Y.; Zheng, G. Y.; Kong, D. S.; Seh, Z. W.; Narasimhan, V. K.; Liang, Z.; Cui, Y. Improved Lithium-Sulfur Batteries with a Conductive Coating on the Separator to Prevent the Accumulation of Inactive S-Related Species at the Cathode-Separator Interface. Energy Environ. Sci. 2014, 7, 3381−3390. (21) Chung, S. H.; Manthiram, A. A Hierarchical Carbonized Paper with Controllable Thickness as a Modulable Interlayer System for High Performance Li-S Batteries. Chem. Commun. 2014, 50, 4184− 4187. (22) Zu, C. X.; Su, Y. S.; Fu, Y. Z.; Manthiram, A. Improved LithiumSulfur Cells with a Treated Carbon Paper Interlayer. Phys. Chem. Chem. Phys. 2013, 15, 2291−2297. (23) Su, Y. S.; Fu, Y. Z.; Cochell, T.; Manthiram, A. A Strategic Approach to Recharging Lithium-Sulphur Batteries for Long Cycle Life. Nat. Commun. 2013, 4, 2985. (24) Chen, S. Q.; Sun, B.; Xie, X. Q.; Mondal, A. K.; Huang, X. D.; Wang, G. X. Multi-Chambered Micro/Mesoporous Carbon Nanocubes as New Polysulfides Reserviors for Lithium-Sulfur Batteries with Long Cycle Life. Nano Energy 2015, 16, 268−280. (25) Ji, X. L.; Evers, S.; Black, R.; Nazar, L. F. Stabilizing LithiumSulphur Cathodes Using Polysulphide Reservoirs. Nat. Commun. 2011, 2, 325. (26) Wang, Q. F.; Zou, R. Q.; Xia, W.; Ma, J.; Qiu, B.; Mahmood, A.; Zhao, R.; Yang, Y. Y. C.; Xia, D. G.; Xu, Q. Facile Synthesis of Ultrasmall CoS2 Nanoparticles within Thin N-Doped Porous Carbon Shell for High Performance Lithium-Ion Batteries. Small 2015, 11, 2511−2517. (27) Song, J. X.; Xu, T.; Gordin, M. L.; Zhu, P. Y.; Lv, D. P.; Jiang, Y. B.; Chen, Y. S.; Duan, Y. H.; Wang, D. H. Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries. Adv. Funct. Mater. 2014, 24, 1243−1250. (28) Zhang, J. W.; Cai, Y. R.; Zhong, Q. W.; Lai, D. Z.; Yao, J. M. Porous Nitrogen-Doped Carbon Derived from Silk Fibroin Protein Encapsulating Sulfur as a Superior Cathode Material for HighPerformance Lithium-Sulfur Batteries. Nanoscale 2015, 7, 17791− 17797. (29) Seh, Z. W.; Li, W.; Cha, J. J.; Zheng, G.; Yang, Y.; McDowell, M. T.; Hsu, P. C.; Cui, Y. Sulphur-TiO2 Yolk-Shell Nanoarchitecture with Internal Void Space for Long-Cycle Lithium-Sulphur Batteries. Nat. Commun. 2013, 4, 1331. (30) Yu, M. P.; Ma, J. S.; Song, H. Q.; Wang, A. J.; Tian, F. Y.; Wang, Y. S.; Qiu, H.; Wang, R. M. Atomic Layer Deposited TiO2 on a Nitrogen-Doped Graphene/Sulfur Electrode for High Performance Lithium-Sulfur Batteries. Energy Environ. Sci. 2016, 9, 1495−1503. (31) Xiao, Z. B.; Yang, Z.; Wang, L.; Nie, H. G.; Zhong, M. E.; Lai, Q. Q.; Xu, X. J.; Zhang, L. J.; Huang, S. M. A Lightweight TiO2/ Graphene Interlayer, Applied as a Highly Effective Polysulfide
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.6b16699. An additional seven figures describing XRD, TG, and cycling of the sulfur−carbon cathode, BET, XPS, and Raman of the TiO2@NC composites (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Jinkui Feng: 0000-0002-5683-849X Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (grant nos. 51371107 and 51571130), Key Research Plan of Sh an dong Province (no. 2015GGE27286), Key Project of the National Natural Science Foundation (no. 51532005), and Taishan scholar program (no. ts201511004).
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REFERENCES
(1) Scrosati, B.; Hassoun, J.; Sun, Y. K. Lithium-ion batteries. A Look into the Future. Energy Environ. Sci. 2011, 4, 3287−3295. (2) Wild, M.; O’Neill, L.; Zhang, T.; Purkayastha, R.; Minton, G.; Marinescu, M.; Offer, G. J. Lithium Sulfur Batteries, A Mechanistic Review. Energy Environ. Sci. 2015, 8, 3477−3494. (3) Dunn, B.; Kamath, H.; Tarascon, J. M. Electrical Energy Storage for the Grid: A Battery of Choices. Science 2011, 334, 928−935. (4) 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. (5) Yang, Y.; Zheng, G. Y.; Cui, Y. Nanostructured Sulfur Cathodes. Chem. Soc. Rev. 2013, 42, 3018−3032. (6) Yin, Y. X.; Xin, S.; Guo, Y. G.; Wan, L. J. Lithium-Sulfur Batteries: Electrochemistry, Materials, and Prospects. Angew. Chem., Int. Ed. 2013, 52, 13186−13200. (7) Zhou, G. M.; Li, F.; Cheng, H. M. Progress in Flexible Lithium Batteries and Future Prospects. Energy Environ. Sci. 2014, 7, 1307− 1338. (8) Xu, W.; Wang, J.; Ding, F.; Chen, X.; Nasybulin, E.; Zhang, Y.; Zhang, J. G. Lithium Metal Anodes for Rechargeable Batteries. Energy Environ. Sci. 2014, 7, 513−537. (9) Zhang, B.; Qin, X.; Li, G. R.; Gao, X. P. Enhancement of Long Stability of Sulfur Cathode by Encapsulating Sulfur into Micropores of Carbon Spheres. Energy Environ. Sci. 2010, 3, 1531−1537. (10) Ji, L. W.; Rao, M. M.; Aloni, S.; Wang, L.; Cairns, E. J.; Zhang, Y. G. Porous Carbon Nanofiber-Sulfur Composite Electrodes for Lithium/Sulfur Cells. Energy Environ. Sci. 2011, 4, 5053−5059. (11) Cao, Z. Y.; Wei, B. Q. A Perspective: Carbon Nanotube MacroFilms for Energy Storage. Energy Environ. Sci. 2013, 6, 3183−3201. (12) Zhou, G. M.; Wang, D. W.; Li, F.; Hou, P. X.; Yin, L. C.; Liu, C.; Lu, G. Q.; Gentle, I. R.; Cheng, H. M. A Flexible Nanostructured Sulphur-Carbon Nanotube Cathode with High Rate Performance for Li-S Batteries. Energy Environ. Sci. 2012, 5, 8901−8906. (13) Yin, L. C.; Wang, J. L.; Lin, F. J.; Yang, J.; Nuli, Y. Polyacrylonitrile/Graphene Composite as a Precursor to a SulfurBased Cathode Material for High-Rate Rechargeable Li-S Batteries. Energy Environ. Sci. 2012, 5, 6966−6972. (14) Xu, C. H.; Xu, B. H.; Gu, Y. Z.; Xiong, G.; Sun, J.; Zhao, X. S. Graphene-Based Electrodes for Electrochemical Energy Storage. Energy Environ. Sci. 2013, 6, 1388−1414. F
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces Absorbent for Fast, Long-Life Lithium-Sulfur Batteries. Adv. Mater. 2015, 27, 2891−2898. (32) Hwang, J. Y.; Kim, H. M.; Lee, S. K.; Lee, J. H.; Abouimrane, A.; Khaleel, M. A.; Belharouak, I.; Manthiram, A.; Sun, Y.-K. High-Energy, High-Rate, Lithium-Sulfur Batteries: Synergetic Effect of Hollow TiO2Webbed Carbon Nanotubes and a Dual Functional Carbon-Paper Interlayer. Adv. Energy Mater. 2016, 6, 1501480. (33) Douglas, A.; Carter, R.; Oakes, L.; Share, K.; Cohn, A. P.; Pint, C. L. Ultrafine Iron Pyrite (FeS2) Nanocrystals Improve Sodium− Sulfur and Lithium−Sulfur Conversion Reactions for Efficient Batteries. ACS Nano 2015, 9, 11156−11165. (34) Rehman, S.; Guo, S. J.; Hou, Y. L. Rational Design of Si/SiO2@ Hierarchical Porous Carbon Spheres as Efficient Polysulfide Reservoirs for High-Performance Li-S Battery. Adv. Mater. 2016, 28, 3167−3172. (35) Han, X.; Xu, Y.; Chen, X.; Chen, Y. C.; Weadock, N.; Wan, J.; Zhu, H.; Liu, Y.; Li, H.; Rubloff, G.; Wang, C.; Hu, L. Reactivation of Dissolved Polysulfides in Li-S Batteries Based on Atomic Layer Deposition of Al2O3 in Nanoporous Carbon Cloth. Nano Energy 2013, 2, 1197−1206. (36) Li, Z.; Zhang, J. T.; Lou, X. W. Hollow Carbon Nanofibers Filled with MnO2 Nanosheets as Efficient Sulfur Hosts for LithiumSulfur Batteries. Angew. Chem., Int. Ed. 2015, 54, 12886−12890. (37) Liang, X.; Garsuch, A.; Nazar, L. F. Sulfur Cathodes Based on Conductive MXene Nanosheets for High-Performance Lithium-Sulfur Batteries. Angew. Chem., Int. Ed. 2015, 54, 3907−3911. (38) Evers, S.; Nazar, L. F. New Approaches for High Energy Density Lithium−Sulfur Battery Cathodes. Acc. Chem. Res. 2013, 46, 1135− 1143. (39) Chai, L. Y.; Wang, J. X.; Wang, H. Y.; Zhang, L. Y.; Yu, W. T.; Mai, L. Q. Porous Carbonized Graphene-Embedded Fungus Film as an Interlayer for Superior Li-S Batteries. Nano Energy 2015, 17, 224− 232. (40) Yaghi, O. M.; Li, H. Hydrothermal Synthesis of a Metal-Organic Framework Containing Large Rectangular Channels. J. Am. Chem. Soc. 1995, 117, 10401−10402. (41) Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.; Choi, E.; Yazaydin, A. O.; Snurr, R. Q.; O’Keeffe, M.; Kim, J.; Yaghi, O. M. Ultrahigh Porosity in Metal-Organic Frameworks. Science 2010, 329, 424−428. (42) Deng, H.; Grunder, S.; Cordova, K. E.; Valente, C.; Furukawa, H.; Hmadeh, M.; Gandara, F.; Whalley, A. C.; Liu, Z.; Asahina, S.; Kazumori, H.; O’Keeffe, M.; Terasaki, O.; Stoddart, J. F.; Yaghi, O. M. Large-Pore Apertures in a Series of Metal-Organic Frameworks. Science 2012, 336, 1018−1023. (43) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and Applications of Metal-Organic Frameworks. Science 2013, 341, 1230444. (44) Xia, W.; Mahmood, A.; Zou, R. Q.; Xu, Q. Metal-Organic Frameworks and their Derived Nanostructures for Electrochemical Energy Storage and Conversion. Energy Environ. Sci. 2015, 8, 1837− 1866. (45) Sun, J. K.; Xu, Q. Functional Materials Derived from Open Framework Templates/Precursors: Synthesis and Applications. Energy Environ. Sci. 2014, 7, 2071−2100. (46) Khaletskaya, K.; Pougin, A.; Medishetty, R.; Rosler, C.; Wiktor, C.; Strunk, J.; Fischer, R. A. Fabrication of Gold/Titania Photocatalyst for CO2 Reduction Based on Pyrolytic Conversion of the Metal− Organic Framework NH2-MIL-125(Ti) Loaded with Gold Nanoparticles. Chem. Mater. 2015, 27, 7248−7257. (47) Hu, S.; Liu, M.; Li, K. Y.; Zuo, Y.; Zhang, A. F.; Song, C. S.; Zhang, G. L.; Guo, X. W. Solvothermal Synthesis of NH2-MIL125(Ti) from Circular Plate to Octahedron. CrystEngComm 2014, 16, 9645−9650. (48) Cao, X. H.; Zheng, B.; Rui, X. H.; Shi, W. H.; Yan, Q. Y.; Zhang, H. Metal Oxide-Coated Three-Dimensional Graphene Prepared by the Use of Metal-Organic Frameworks as Precursors. Angew. Chem., Int. Ed. 2014, 53, 1404−1409. (49) Jin, Z. K.; Yang, M.; Wang, J. J.; Gao, H. Y.; Lu, Y. F.; Wang, G. One-Pot Fabrication of Hierarchical Nanosheet-Based TiO2-Carbon
Hollow Microspheres for Anode Materials of High-Rate Lithium-Ion Batteries. Chem. - Eur. J. 2016, 22, 6031−6036. (50) Wang, Z. Q.; Li, X.; Xu, H.; Yang, Y.; Cui, Y. J.; Pan, H. G.; Wang, Z. Y.; Chen, B. L.; Qian, G. D. Porous Anatase TiO2 Constructed from a Metal-Organic Framework for Advanced Lithium-Ion Battery Anodes. J. Mater. Chem. A 2014, 2, 12571−12575. (51) Crepaldi, E. L.; Soler-Illia, G. J. A. A.; Grosso, D.; Cagnol, F.; Ribot, F.; Sanchez, C. Controlled Formation of Highly Organized Mesoporous Titania Thin Films: From Mesostructured Hybrids to Mesoporous Nanoanatase TiO2. J. Am. Chem. Soc. 2003, 125, 9770− 9786. (52) Ni, J. F.; Fu, S. D.; Wu, C.; Maier, J.; Yu, Y.; Li, L. SelfSupported Nanotube Arrays of Sulfur-Doped TiO2 Enabling Ultrastable and Robust Sodium Storage. Adv. Mater. 2016, 28, 2259−2265. (53) Bala, S.; Mondal, I.; Goswami, A.; Pal, U.; Mondal, R. Co-MOF as a Sacrificial Template: Manifesting a New Co3O4/TiO2 System with Ap-N Heterojunction for Photocatalytic Hydrogen Evolution. J. Mater. Chem. A 2015, 3, 20288−20296. (54) Xiu, Z. L.; Alfaruqi, M. H.; Gim, J.; Song, J.; Kim, S.; Duong, P. T.; Baboo, J. P.; Mathew, V.; Kim, J. MOF-Derived Mesoporous Anatase TiO2 as Anode Material for Lithium-Ion Batteries with High Rate Capability and Long Cycle Stability. J. Alloys Compd. 2016, 674, 174−178. (55) Li, X. N.; Liang, J. W.; Zhang, K. L.; Hou, Z. G.; Zhang, W. Q.; Zhu, Y. C.; Qian, Y. T. Amorphous S-rich S1‑xSex/C(x ≤ 0.1) Composites Promise Better Lithium-Sulfur Batteries in a CarbonateBased Electrolyte. Energy Environ. Sci. 2015, 8, 3181−3186. (56) Talapaneni, S. N.; Mane, G. P.; Mano, A.; Anand, C.; Dhawale, D. S.; Mori, T.; Vinu, A. Synthesis of Nitrogen-Rich Mesoporous Carbon Nitride with Tunable Pores, Band Gaps and Nitrogen Content from a Single Aminoguanidine Precursor. ChemSusChem 2012, 5, 700−708. (57) Han, K.; Shen, J.; Hao, S.; Ye, H.; Wolverton, C.; Kung, M. C.; Kung, H. H. Free-Standing Nitrogen-doped Graphene Paper as Electrodes for High-Performance Lithium/Dissolved Polysulfide Batteries. ChemSusChem 2014, 7, 2545−2553. (58) Cong, Y.; Li, X. K.; Qin, Y.; Dong, Z. J.; Yuan, G. M.; Cui, Z. W.; Lai, X. J. Carbon-Doped TiO2 Coating on Multiwalled Carbon Nanotubes with Higher Visible Light Photocatalytic Activity. Appl. Catal., B 2011, 107, 128−134. (59) Fu, Y.; Ming, H.; Zhou, Q.; Jin, L. L.; Li, X. W.; Zheng, J. W. Nitrogen-Doped Carbon Coating Inside Porous TiO2 Using Small Nitrogen-Containing Molecules for Improving Performance of Lithium-Ion Batteries. Electrochim. Acta 2014, 134, 478−485. (60) Peng, H. J.; Huang, J. Q.; Zhao, M. Q.; Zhang, Q.; Cheng, X. B.; Liu, X. Y.; Qian, W. Z.; Wei, F. Nanoarchitectured Graphene/CNT@ Porous Carbon with Extraordinary Electrical Conductivity and Interconnected Micro/Mesopores for Lithium-Sulfur Batteries. Adv. Funct. Mater. 2014, 24, 2772−2781. (61) Qie, L.; Manthiram, A. A Facile Layer-by-Layer Approach for High-Areal-Capacity Sulfur Cathodes. Adv. Mater. 2015, 27, 1694− 700. (62) Song, J. X.; Yu, Z. X.; Gordin, M. L.; Wang, D. H. Advanced Sulfur Cathode Enabled by Highly Crumpled Nitrogen-Doped Graphene Sheets for High-Energy-Density Lithium−Sulfur Batteries. Nano Lett. 2016, 16, 864−870. (63) Qiao, Y.; Hu, X. L.; Liu, Y.; Chen, C. J.; Xu, H. H.; Hou, D. F.; Hu, P.; Huang, Y. H. Conformal N-Doped Carbon on Nanoporous TiO2 Spheres as a High-Performance Anode Material for Lithium-Ion Batteries. J. Mater. Chem. A 2013, 1, 10375−10381. (64) Bai, S. Y.; Liu, X. Z.; Zhu, K.; Wu, S. C.; Zhou, H. S. MetalOrganic Framework-Based Separator for Lithium-Sulfur Batteries. Nature Energy 2016, 1, 16094. (65) Zuo, W. H.; Wang, C.; Li, Y. Y.; Liu, J. P. Directly Grown Nanostructured Electrodes for High Volumetric Energy Density Binder-Free Hybrid Supercapacitors: A Case Study of CNTs// Li4Ti5O12. Sci. Rep. 2015, 5, 7780. (66) Wang, X. L.; Li, G.; Li, J. D.; Zhang, Y. N.; Wook, A.; Yu, A. P.; Chen, Z. W. Structural and Chemical Synergistic Encapsulation of G
DOI: 10.1021/acsami.6b16699 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces Polysulfides Enables Ultralong-Life Lithium-Sulfur Batteries. Energy Environ. Sci. 2016, 9, 2533−2538. (67) Tang, H. L.; Cai, S. C.; Xie, S. L.; Wang, Z. B.; Tong, Y. X.; Pan, M.; Lu, X. H. Metal-Organic-Framework-Derived Dual Metal- and Nitrogen-Doped Carbon as Efficient and Robust Oxygen Reduction Reaction Catalysts for Microbial Fuel Cells. Adv. Sci. 2016, 3, 1500265. (68) Jozwiuk, A.; Berkes, B. B.; Weiss, T.; Sommer, H.; Janek, J.; Brezesinski, T. The Critical Role of Lithium Nitrate in the Gas Evolution of Lithium-Sulfur Batteries. Energy Environ. Sci. 2016, 9, 2603−2608. (69) Balogun, M.-S.; Zhu, Y. K.; Qiu, W. T.; Luo, Y.; Huang, Y. C.; Liang, C. L.; Lu, X. H.; Tong, Y. X. Chemically Lithiated TiO2 Heterostructured Nanosheet Anode with Excellent Rate Capability and Long Cycle Life for High-Performance Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2015, 7, 25991−26003.
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